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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.


Recently Published Bulletin Reports

Ambrym (Vanuatu) Fissure eruption in mid-December 2018 produces fountaining and lava flows; no activity evident in caldera after 17 December

Fournaise, Piton de la (France) One-day eruptive events in April and July; 5-week eruption 27 April-1 June 2018

Negra, Sierra (Ecuador) Fissure opens on NNE caldera rim 26 June 2018, NW-flank lava flows reach the sea

Great Sitkin (United States) Small phreatic explosions in June and August 2018; ash deposit on snow near summit

Alaid (Russia) Small ash plume reported on 21 August 2018

Aira (Japan) Activity increased at Minamidake and decreased at Showa crater in early 2018

Suwanosejima (Japan) Intermittent ash emission continues from January through June 2018

Etna (Italy) Degassing continues, accompanied by intermittent ash emissions and small Strombolian explosions in June and July 2018

Stromboli (Italy) Continued Strombolian activity from five active summit vents through March-June 2018

Agung (Indonesia) Ash explosions and lava dome effusion continue during January-July 2018

Fernandina (Ecuador) Brief eruptive episode 16-22 June 2018, lava flows down N flank into the ocean

Fuego (Guatemala) Pyroclastic flows on 3 June 2018 cause at least 110 fatalities, 197 missing, and extensive damage; ongoing ash explosions, pyroclastic flows, and lahars



Ambrym (Vanuatu) — January 2019 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Fissure eruption in mid-December 2018 produces fountaining and lava flows; no activity evident in caldera after 17 December

Ambrym is a shield volcano in the Vanuatu archipelago with a 12-km-wide summit caldera containing the persistently active Benbow and Marum craters. These craters are home to multiple active vents that produce episodic lava lakes, explosions, lava flows, ash, and gas emissions. Occasional fissure eruptions occur outside of these main craters. This report covers July to December 2018 and summarizes reports by the Vanuatu Meteorology and Geohazards Department (VMGD), the Wellington Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data.

As of the beginning of the reporting period, the hazard status at Ambrym had remained at Volcanic Alert Level 2 ("Major unrest") since 7 December 2017. Monthly VMGD activity reports describe the continued activity within the two main craters, consisting of multiple lava lakes, sustained substantial degassing and steam emission, and seismic unrest. Frequent thermal anomalies were detected throughout the reporting period (figure 42). The danger areas were confined to the Permanent Exclusion Zone within a 1 km radius of Benbow crater, and the Permanent Exclusion Zone and Danger Zone A within about a 2.7 km radius of Marum crater (including Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu, see BGVN 43:07, figure 38).

Figure (see Caption) Figure 42. Plot of MODIS thermal infrared data analyzed by MIROVA showing the log radiative power of thermal anomalies at Ambrym for the year ending on 1 February 2019. After the December 2018 eruption no further thermal anomalies were noted for the reporting period. Courtesy of MIROVA.

Observations and seismic data analysis by VMGD confirmed the onset of a small-scale intra-caldera fissure eruption at 0600 local time on 15 December. This new fissure produced lava fountains and lava flows with ash and gas plumes (figure 43). Footage of the eruption by John Tasso shows the fissure eruption to the SE of Marum crater producing lava fountaining. A Sentinel-2 satellite image shows a white eruption plume and two new lava flow lobes (figure 44); the actual fissure vent was hidden by the plume. The northernmost lava flow filled in the 500 x 900 m Lewolembwi crater and a smaller lobe continued to flow towards the E (figure 44). Due to this elevated activity, the Volcanic Alert Level was raised to 3 ("Minor eruption"), with the danger zones increased to a 2 km radius around Benbow crater and a 4 km radius around Marum crater. VMGD warned of additional risk within 3 km of eruptive fissures in the SE caldera area.

Figure (see Caption) Figure 43. Image of the fissure eruption producing lava fountaining at Ambrym volcano, taken from a video recorded by John Tasso on 16 December 2018.
Figure (see Caption) Figure 44. Satellite imagery showing the Ambrym caldera area in November-December 2018. Top: True color Landsat-8 satellite image acquired on 13 December 2018 showing the area prior to the fissure eruption. Bottom: False-color infrared Sentinel-2 composite image (bands 12, 11, and 4) showing the multiple active vents and lava lakes within Marum and Benbow craters (top third of the image, acquired on 25 November 2018), and the eruption plume and the bright orange/red lava flow fronts in the bottom of the image (acquired on 15 December 2018); the fissure is obscured by the plume. Courtesy of Sentinel-Hub Playground.

Through 16-17 December, ash and gas emission continued from Benbow and Marum craters (figures 45 and 46), accompanied by ongoing localized seismicity; earthquakes with a magnitude greater than five were felt on neighboring islands. The Wellington VAAC issued ash advisories on 16 and 17 December noting maximum cloud altitudes of approximately 8 km.

Figure (see Caption) Figure 45. Ash emission from Ambrym volcano at 1600 on 16 December 2018. Webcam image courtesy of, and annotated by, VMGD.
Figure (see Caption) Figure 46. Elevated atmospheric SO2 emissions from Ambrym on 17 December 2018 with a total measured mass of 23.383 kt in this scene. The units on the scale bar reflect SO2 in terms of Dobson Units (DU). Courtesy of the NASA Goddard Flight Center Atmospheric Chemistry and Dynamics Laboratory.

From 14 to 26 December, the National Volcano Monitoring Network detected over 4,500 earthquakes related to the eruptive activity, but locally felt seismicity decreased. Analysis of satellite imagery confirmed surface deformation associated with the increase in activity. Media reports from Radio New Zealand indicated that seismic activity during December resulted in ground rupture and damage to homes on the island and residents were moved to evacuation centers.

During the reporting period, thermal anomalies were frequently detected by the MODIS satellite instruments and subsequently analyzed using the MODVOLC algorithm, reflecting the lava lake activity in Benbow and Marum craters, as well additional thermal anomalies during the December 2018 fissure eruption and subsequent lava flows to the SE of the main crater area (figures 47 and 48).

Figure (see Caption) Figure 47. MODVOLC Thermal Alert System from July through December 2018 showing the two active craters of Ambrym, Benbow and Marum, and the December 2018 fissure eruption. Red areas indicate approximate locations of Thermal Anomaly detections along with the number of detections. Courtesy of HIGP - MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 48. MODVOLC thermal alerts detected over Ambrym volcano during July 2018 through December 2018 showing hot spots located at Benbow and Marum craters and the December 2018 fissure eruption. Courtesy of HIGP - MODVOLC Thermal Alerts System.

As of 7 January 2019, Ambrym remains on Alert Level 3 with continued seismic activity. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system has not detected any recent thermal anomalies, indicating the end of the fissure eruption and a reduction in activity at the main craters.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Radio New Zealand, 155 The Terrace, Wellington 6011, New Zealand (URL: https://www.radionz.co.nz/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); John Tasso, Vanuatu Island Experience, Port Vatu, West Ambrym, Vanuatu (URL: http://vanuatuislandexperience.com/).


Piton de la Fournaise (France) — September 2018 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


One-day eruptive events in April and July; 5-week eruption 27 April-1 June 2018

Short pulses of intermittent eruptive activity have characterized Piton de la Fournaise, the large basaltic shield volcano on Reunion Island in the western Indian Ocean, for several thousand years. The most recent episode occurred during 14 July-28 August 2017 with a 450-m-long fissure on the S flank inside the Enclos Fouqué caldera about 850 m W of Château Fort. Three eruptive episodes occurred during March-August 2018, the period covered in this report; two lasted for one day each on the N flank in April and July, and one lasting from late April through May located on the S flank. Information is provided primarily by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) as well as satellite instruments.

The first of three eruptive events during March-August 2018 occurred during 3-4 April and was a 1-km-long fissure that opened in seven segments with two eruptive vents. It was located on the N flank of the central cone, just S of the Nez Coupé de Sainte Rose on the rim of the caldera. A longer lasting eruptive event began on 27 April and was located in the cratère Rivals area on the S flank of the central cone. The main fissure had three eruptive vents initially, only one of which produced lava that flowed in tunnels away from the site toward the S rim of the Enclos Fouqué caldera. The longest flow reached 3 km in length and set fires at the base of the rampart rim of the caldera. Flow activity gradually decreased throughout May, and seismic tremor ceased, indicating the end of the event, on 1 June 2018. A third, brief event on 13 July 2018 produced four fissures with 20-m-high incandescent lava and aa flows that traveled several hundred meters across the NNW flank of the central cone, covering a large section of the most popular hiking trail to the summit. The event only lasted for about 18 hours but caused significant geomorphologic change as the first flow activity in that area in several hundred years.

The MIROVA plot of thermal energy from 6 February-1 September 2018 clearly shows two of the three eruptive events that took place during that period. The 27 April to 1 June event produced an initial very strong thermal signature that decreased throughout May. Cooling after the flow ceased continued for most of June. The one-day eruptive event on 13 July was also recorded, but the similarly brief event on 3-4 April was not captured in the thermal data (figure 126).

Figure (see Caption) Figure 126. The MIROVA plot of thermal energy from Piton de La Fournaise from 6 February-1 September 2018 clearly shows two of the three eruptive events that took place during that period. The longest event, from 27 April to 1 June produced an initial very strong thermal signature that decreased throughout May. Cooling after the flow ceased continued for most of June. A brief one-day eruptive event on 13 July was also recorded. A similarly brief event on 3-4 April was not recorded. Courtesy of MIROVA.

Eruptive event of 3-4 April 2018. Minor inflation and seismicity were intermittent from the end of August 2017 when the last eruptive episode ended. Significant seismic activity around the summit resumed on 23 March 2018 and accelerated through the end of the month. Inflation continued throughout March as well. A change of composition was detected in the summit fumaroles on 23 March 2018; the fluids were enriched in CO2 and SO2. Beginning on 3 April around 0550 local time, OVPF reported a seismic swarm and deformation consistent with magma rising towards the surface. Seismic tremor began around 1040 in an area on the N flank near the Nez Coupé de Sainte Rose. The tremor intensity continued to increase throughout the day; OVPF visually confirmed the eruption around 1150 in the morning on the upper part of the N flank (figure 127).

Figure (see Caption) Figure 127. The eruptive site at Piton de la Fournaise on 3 April 2018 on the N flank near the Nez Coupé de Sainte Rose. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du 03 avril 2018 à 16h30 heure locale).

A helicopter overflight in mid-afternoon revealed a 1-km-long fissure that had opened in seven distinct segments; lava fountains emerged from two of the segments. The last active segment was just below the rampart of the Nez Coupé de Sainte Rose (figure 128). Both seismic and surface eruptive activity stopped abruptly the following day at 0400.

Figure (see Caption) Figure 128. The brief eruption of 3-4 April 2018 was located on the N flank of the central crater near the Nez Coupé de Sainte Rose, a point on the rampart rim of the Enclos. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du 03 avril 2018 à 16h30 heure locale).

Eruptive event of 27 April-1 June 2018. OVPF reported 2.5 cm of inflation in the 15 days after the 3-4 April eruption. Seismic activity resumed at the base of the summit area on 21 April, and a new seismic swarm began at 2015 local time on 27 April. This was followed three hours later by tremor activity indicating the beginning of a new eruptive event from fissures that opened on the S flank in the area of cratère Rivals (figure 129). Four fissures opened; one on each side of the crater and one cutting across it were initially active, but activity moved the next morning to a fourth fissure just downstream from Rivals crater and extended for less than 300 m. Fountains of lava rose to 30 m during a morning overflight on 28 April. Several streams of lava quickly coalesced into a single flow heading S towards the rampart at the rim of the Enclos Fouqué (figure 130). By 0830 on 28 April the flow was less than 300 m from the rim and had destroyed an OVPF seismic station and a GPS station. The OMI instrument on the Aura satellite recorded a significant SO2 plume from the event on 28 April (figure 131).

Figure (see Caption) Figure 129. A fissure extended about 300 m S from the Rivals crater on the S flank of the cone at Piton de la Fournaise on 28 April 2018 where a new eruptive event began the previous evening. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du samedi 28 avril 2018 à 10h00 heure locale).
Figure (see Caption) Figure 130. The flow from the new fissure near Rival crater at Piton de la Fournaise had flowed to within 300 m of the Enclos Fouqué caldera rim by 0830 on 28 April 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du samedi 28 avril 2018 à 10h00 heure locale).
Figure (see Caption) Figure 131. An SO2 plume of 9.51 Dobson Units (DU) drifted NW from Reunion Island on 28 April 2018 where Piton de la Fournaise began a new eruptive episode the previous evening. Courtesy of NASA Goddard Space Flight Center.

Tremor activity decreased throughout the day on 28 April while the flow continued. The surface flow rate was measured initially at 8-15 m3 per second; it had slowed to 3-7 m3 per second by late that afternoon. Three active vents were observed on the morning of 29 April that continued the next day with fountains rising about 15 m (figure 132). A small cone (less than 5 m high) had grown around the southernmost vent and the larger middle vent contained a small lava lake. Visible lava was flowing only from the middle vent. The flow consisted of three branches; the two spreading to the E were less than 150 m long while the third flow traveled W past the E Cassian crater and had reached 1.2 km in length by 1020 on 30 April. On 30 April OVPF observed a flow from the previous day that had traveled 2.6 km, reaching the foot of the S edge of the l'Enclos Fouqué rampart.

Figure (see Caption) Figure 132. Lava flowed from three active vents near the Rival crater at Piton de la Fournaise on 30 April 2018. A small cone (less than 5 m high) had grown around the southernmost vent (bottom center) and the larger middle vent contained a small lava lake. Lava was actively flowing from only the middle vent. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du lundi 30 avril 2018 à 16h00 heure locale).

OVPF noted on 2 May 2018 that the intensity of volcanic tremor remained stable, slight deflation was measured, and the surface flow rate was estimated from satellite data at 1-3 m3 per second. Field observations during the afternoon of 3 May indicated that most activity was occurring from the central vent which had grown into a small pyroclastic cone with incandescent ejecta and gas emissions (figure 133). A well-developed lava tunnel had a number of roof breakouts.

Figure (see Caption) Figure 133. The eruptive site at Piton de la Fournaise on 3 May 2018 had two main vents, the larger pyroclastic cone produced incandescent ejecta and dense gas plumes. Courtesy of OVPF (©IPGP/OVPF) (Bulletin d'activité du vendredi 4 mai 2018 à 15h00 heure locale).

Field reconnaissance during 6-7 May confirmed that most of the activity was concentrated at the central cone with incandescent ejecta rising less than 10 m from the top, and the only source of lava was enclosed in a tunnel. The front of the flow was still active with numerous fires reported at the base of the rampart at the rim of the Enclos Fouqué. The farthest upstream cone was still active, but weak with only occasional bursts of incandescent ejecta. By 10 May the intensity of the volcanic tremor had stabilized at a low level. Two cones remained active, the upstream cone had incandescent ejections rising 10-20 m high. Lava was contained in tunnels near the cones but was exposed below the Piton de Bert (figure 134). The frontal lobe of the flow was located 3 km from the eruptive site, downstream of Piton de Bert (figure 135) at the base of the rampart rim of the Enclos. Numerous fires continued at the base of the rampart due to fresh flows (figure 136).

Figure (see Caption) Figure 134. Lava flows were visible on the slope break below Piton de Bert at Piton de la Fournaise on 10 May 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).
Figure (see Caption) Figure 135. By 10 May 2018, the front of the flow from the 27 April eruptive event at Piton de la Fournaise was located 3 km from the eruptive site downstream from Piton de Bert. Courtesy of OVPF and Google Earth (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).
Figure (see Caption) Figure 136. Fires started by active lava flows affected the base of the rampart rim of the Enclos at Piton de la Fournaise on 10 May 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).

A minor spike in seismicity was recorded on 15 May 2018; at the same time inflation resumed underneath the caldera. The smaller, farthest upstream cone was the most active on 16 May, with 20-30 m high ejecta. A webcam view on 24 May showed that the vent on the larger pyroclastic cone was nearly closed, and that flow activity was largely contained in tunnels. Field observations that day also confirmed the overall decrease in activity; only a single incandescent zone in the lava field near the vent was observed at nightfall, although persistent degassing continued (figure 137).

Figure (see Caption) Figure 137. By 24 May 2018, activity at Piton de la Fournaise from the eruptive episode that began on 27 April had diminished significantly as seen in this view of the eruptive site near the Rival crater. Photo courtesy of Cité du Volcan and OVPF (Bulletin d'activité du vendredi 25 mai 2018 à 15h00 heure locale).

An overflight on 29 May confirmed the decreasing flow activity and continued inflation. Only rare tongues of lava could be observed in the flow field. The flow front had not progressed eastward for the previous 15 days. The main cone remained open at the top with a small eruptive vent less than 5 m in diameter. Small collapses and slumps were visible on the outer flanks of the cone (figure 138). The height of the main cone was estimated at 22-25 m on 31 May and the second vent was observed to be completely closed off. OVPF reported the end of the eruption at 1430 on 1 June 2018 based on the cessation of seismic tremor (figure 139). The MODVOLC thermal alert system recorded multiple thermal alerts from 27 April through 29 May.

Figure (see Caption) Figure 138. The main cone of the eruptive event at Piton de la Fournaise remained open at the top with a small eruptive vent less than 5 m in diameter on 29 May 2018 that produced abundant steam and gas. Small collapses and slumps were visible on the outer flanks of the cone. N is to the upper left of image. Courtesy of OVPF (© OVPF/IPGP ) (Bulletin d'activité du mercredi 30 mai 2018 à 15h30 heure locale).
Figure (see Caption) Figure 139. The evolution of the RSAM signal (indicator of the volcanic tremor and the intensity of the eruption) at Piton de l aFournaise between 27 April 2018 at 2000 and 1430 on 1 June at the seismic station of BOR, located at the summit of the central cone. Courtesy of OVPF (© OVPF/IPGP) (Bulletin exceptionnel du vendredi 1 juin 2018 à 15h00 heure locale).

Eruptive event of 13 July 2018. Throughout June 2018, very little activity was reported; only 23 shallow seismic events were recorded during the month and no significant deformation was measured by the OVPF deformation network. OVPF reported that inflation resumed around 1 July. A sharp increase in seismicity was observed beginning at 2340 local time on 12 July followed by a seismic swarm and rapid deformation around midnight. Tremor activity was recorded beginning about 0330 on 13 July and located on the N flank. The first images of the eruption were visible in a webcam at around 0430. Four eruptive fissures were observed in an overflight that morning around 0800 that opened over a 500-m-long zone, spreading from upstream of la Chapelle de Rosemont towards Formica Leo. Incandescent ejecta rose less than 20 m and the aa lava had flowed about 200 m from the fissures (figures 140 and 142). The lava flow propagation rate was estimated at about 6 m per minute during the first hour of activity. Thereafter, the rate continued to decrease to less than 1 m per minute at the end of the eruption. After a progressive decrease of tremor, and about 3 hours of "gas flushes" that are typically observed at the end of Piton de la Fournaise eruptions (according to OVPF), the eruption stopped on 13 July at 2200 local time. Both MIROVA and MODVOLC recorded thermal anomalies from the brief one-day event (figure 126).

Figure (see Caption) Figure 140. A new eruption at Piton de la Fournaise on 13 July 2018 lasted only a single day and produced a 500-m-long zone with four fissure vents located on the N flank of the cone near la Chapelle de Rosemont and flowing towards Formica Leo. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du vendredi 13 juillet 2018 à 10h30 heure locale).
Figure (see Caption) Figure 141. Four fissure vents on the N flank of the central cone near la Chapelle de Rosemont produced ejecta and lava flows for about 18 hours on 13 July 2018 at Piton de la Fournaise. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du vendredi 13 juillet 2018 à 10h30 heure locale).

The 13 July 2018 eruption lasted about 18 hours and produced about 0.3 million m3 of lava. Lava flows covered more than 400 m of the popular hiking trail leading to the summit (figure 142 and 143) and almost completely filled the Chapelle de Rosemont (figure 144), an old vent and a characteristic feature within the Enclos Fouqué landscape that was first described in reports of the early volcano expeditions at the end of the 18th century. This area of the volcano on the NNW flank had not experienced active eruptive events for at least the past 400 years. Despite the low volume of lava emitted and its short duration, this event significantly changed the geomorphology of the area, which was quite well known and popular with visitors. Inflation resumed after the eruptive event of 13 July and a brief pulse of seismic activity was reported by OVPF on 26 July. They noted on 13 August that after about a month of inflation, seismicity and inflation both ceased.

Figure (see Caption) Figure 142. The brief 13 July 2018 eruptive event covered an area on the NNW flank of the central cone that had not had active flow activity for at least 400 years. Photo taken midday on 13 July 2018. Courtesy of OVPF (© OVPF/IPGP) (July 2018 Monthly bulletin of the Piton de la Fournaise).
Figure (see Caption) Figure 143. The area of the lava flows covered during the 13 July 2018 eruption are shown in white, the fissures are shown in red, and the popular hiking trail to the summit is shown in yellow. Over 400 m of the trail was covered with fresh flows. The fissures were located on the NNW flank in the area of the Chapelle de Rosemont, an old vent. The base map was produced by OVPF using aerial and ground-based photographs that were processed by means of stereophotogrammetry. Courtesy of OVPF (July 2018 Monthly bulletin of the Piton de la Fournaise).
Figure (see Caption) Figure 144. Fresh, dark lava covers the Chapelle de Rosemont on 14 July 2018 after a one-day eruption at Piton de la Fournaise the previous day. The area was first described by explorers in the 18th century and had not seen recent flow activity. Courtesy of OVPF (© OVPF/IPGP) (July 2018 Monthly bulletin of the Piton de la Fournaise).

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Sierra Negra (Ecuador) — September 2018 Citation iconCite this Report

Sierra Negra

Ecuador

0.83°S, 91.17°W; summit elev. 1124 m

All times are local (unless otherwise noted)


Fissure opens on NNE caldera rim 26 June 2018, NW-flank lava flows reach the sea

Sierra Negra shield volcano on the Galápagos Island of Isabela has erupted six times since 1948, most recently in 2005. The eruptions of 2005, 1979, 1963, and 1953 were located in the area known as 'Volcán Chico' near the NNE rim of the summit caldera, which extends about 9 km E-W and 7 km N-S (figure 12). The lava flows generated in these eruptions were directed mainly towards the N and NE flanks of Sierra Negra, in some cases reaching Elizabeth Bay to the N and in others filling the interior of the caldera (figure 13). A new effusive eruption that occurred from 26 June through August 2018 is covered in this report with information provided primarily by Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN). Additional information comes from the Washington Volcanic Ash Advisory Center (VAAC), and several sources of satellite information.

Figure (see Caption) Figure 12. Sierra Negra is located on the southern part of Isabela Island in the Galápagos National Park, Ecuador. Courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).
Figure (see Caption) Figure 13. The Sierra Negra caldera with the locations of GPS stations and the fissures, vents, and flows from the 2005 eruption. From Geist et al. (2005), courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).

Beginning in 2017, the Geophysical Institute of the National Polytechnic School (IGEPN) installed a surveillance network of six broadband seismic stations for the Galápagos volcanoes. One station is located on the NE edge of the Sierra Negra caldera and another on the SE flank. After 12 years of little activity, an increase in seismicity beneath and around the caldera became evident by July 2017 (figure 14). On 19 October 2017 (local time) the seismic monitors detected a 16-km-deep M 3.8 earthquake with an epicenter on the NE border of the caldera in the vicinity of Volcán Chico. Four additional similar earthquakes occurred within the next hour. Another earthquake of similar size occurred on 22 October; between 15 and 16 November, three earthquakes with M 3.0 or greater were recorded. The frequency of seismic activity increased significantly in December 2017, with over 550 events recorded during the first three weeks of December 2017; at least three had magnitudes greater than 3. GPS receivers showed uplift of the caldera floor of 80 cm between 2013 and 2017. InSAR interferometry data indicated substantial inflation of the caldera floor of about 70 cm between December 2016 and late November 2017, reaching a level higher than that which preceded the eruption of 2005 (figure 15).

Figure (see Caption) Figure 14. The number of daily seismic events at Sierra Negra between 13 May 2015 and 23 November 2017 show a distinct increase in activity by July 2017. The colors represent different types of earthquakes; red is VT or volcanotectonic, orange is LP or Long Period, and blue is HB or Hybrid. Courtesy of IG (Informe Especial Sierra Negra N.- 2, Actividad reciente del volcán Sierra Negra – Isla Isabela, 23 November 2017).
Figure (see Caption) Figure 15. Inflation of the caldera floor at Sierra Negra between December 2016 and November 2017 exceeded 70 cm. The left graph shows the displacement plotted in centimeters versus time, and the right image is the spatial deformation from the InSAR data showing inflation at the caldera (center) and on the SW coast of Isla Isabela. Figures courtesy of Falk Amelung (RSMAS) and IG (Informe Especial Sierra Negra N.- 2, Actividad reciente del volcán Sierra Negra – Isla Isabela, 23 November 2017).

By early January 2018, inflation over the preceding 12 months was close to 1 m, with a total inflation exceeding that prior to the 2005 eruption. Seismic activity, focused on two fracture zones trending NE-SW across the summit caldera, continued to increase until 26 June 2018 when a fissure opened near Volcán Chico on the NNE caldera rim. Over the next 24 hours four fissures opened on the N rim and the NW flank. Three of the fissures were active only for this period, but the fourth, on the NW flank about 7 km below the caldera rim, continued to effuse lava for all of July and most of August 2018. Lava flows reached the sea in early July. Several pulses of increased effusive activity corresponded with increased seismic, thermal, and gas-emission activity recorded by both ground-based and satellite instrumentation. By the last week of August active flows were no longer observed, although the cooling flows continued to emit thermal signals for several weeks.

Activity during January-early June 2018. Elevated seismicity continued into 2018 with a M 3.8 event recorded on 6 January 2018 that was felt by tourists, guides, and Galápagos National Park officials. Tens of additional smaller events continued throughout the month, reaching more than 100 seismic events per day a few times; the earthquakes were located below the caldera at a depth of less than 8 km. A M 4.1 event on 10 January was located at a depth of 7 km. By 12 January, the total inflation of the caldera since the beginning of 2017 was 98 cm (figure 16).

Figure (see Caption) Figure 16. Seismicity and deformation at Sierra Negra between 13 May 2015 and 28 December 2017. The orange line represents the cumulative VT earthquakes, and the blue points record the inflation in cm of the floor accumulated since the beginning of 2015. A change in slope of both curves is evident at the end of 2017 indicating the rate of increase of inflation and seismicity. Courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).

IG reported 14 seismic events with magnitudes ranging from 3.0-4.6 between 1 January and 19 March 2018. A M 4.4 event on 18 January was located less than 1 km below the surface with an epicenter on the S rim of the caldera. A M 4.1 event on 27 February was also located less than 1 km below the surface. A M 4.6 event on 14 March was the largest to date at Sierra Negra and was located only 0.3 km below the surface. Measurements of CO2, SO2, and H2S made at the Azufral fumarole field (figure 17) on the W rim of the caldera in early February did not have values significantly different compared to May 2014 and September 2017. With the continued increase in frequency and magnitude of shallow seismic activity, IG noted the increased risk of renewed eruptive activity, and noted that most of the active flows of the last 1,000 years were located on the N flank (figure 18).

Figure (see Caption) Figure 17. A fumarole field near Azufral on the W rim of the Sierra Negra caldera on 6 February 2018 remained unchanged after several months of increased seismicity in the area. Photo by M. Almeida, courtesy of IG-EPN (Informe Especial del Volcán Sierra Negra (Islas Galápagos) -2018 - Nº 3, Actualizado del estado de agitación interna y posibles escenarios eruptivos, 19 March 2018).
Figure (see Caption) Figure 18. Simplified geologic map of Sierra Negra with lava flows colored as a function of relative age (modified from Reynolds et al., 1995), courtesy of IG (Informe Especial del Volcán Sierra Negra (Islas Galápagos) -2018 - Nº 3, Actualizado del estado de agitación interna y posibles escenarios eruptivos, 19 March 2018).

Increases in seismicity continued into early June. IG noted that on 25 May 2018, 104 seismic events were recorded, the largest number in a single day since 2015. A M 4.8 event on 8 June was accompanied by over 40 other smaller earthquakes. The earthquake epicenters were mainly located on the edges of the crater in two NE-SW trending lineaments; the first covered the N and W edges of the crater and the second trended from the NE edge to the S edge. Deformation data indicated the largest displacements were at the caldera's center, compared with lower levels of deformation outside of the caldera.

Eruption of 26 June-late August 2018. IG reported an increase in seismicity and a M 4.2 earthquake on 22 June 2018. A larger M 5.3 earthquake was detected at 0315 on 26 June, 5.3 km below the caldera. The event was felt strongly on the upper flanks and in Puerto Villamil (23 km SE). About 8 hours later, at 1117, an earthquake swarm characterized by events located at 3-5 km depth was recorded. A M 4.2 earthquake took place at 1338 and was followed by increasing amplitudes of seismic and infrasound signals. Parque Nacional Galápagos staff then reported noises described as bellows coming from the Volcán Chico fissure vent, which, coupled with the seismicity and infrasound data, suggested the start of an eruption. About 20 minutes later IG described a thermal anomaly identified in satellite images in the N area of the caldera near Volcán Chico and Park staff observed lava flowing towards the crater's interior as well as towards the N flank in the direction of Elizabeth Bay (figure 19).

Figure (see Caption) Figure 19. Lava flows descended from the N flank of Sierra Negra to Elizabeth Bay on 26 June 2018 from four distinct fissure vents (numbered). Fissure 1 was located near Volcan Chico on the caldera rim, and fissures 2, 3, and 4 were located on the N flank. Details of the fissures are discussed later in the report. Video of the flow was captured by Nature Galápagos. Photo courtesy of AFP and BBC News, annotated and reprinted by IG (Informe Especial N° 16 – 2018, Volcán Sierra Negra, Islas Galápagos, Actualización de la Actividad Eruptiva, Quito, 23 de Julio del 2018).

The Washington VAAC reported an ash plume visible in satellite imagery late on 26 June at 10.6 km altitude drifting SW. By the following morning, a plume of ash mixed with SO2 was drifting W at 8.2 km altitude. IG reported a new ash emission late on 27 June drifting NW at 6.1 km altitude. A substantial SO2 plume emerged on 27 June and was recorded by the OMI and OMPS satellite-based instruments drifting SW that day and the next (figure 20). The MODVOLC thermal alert system confirmed the beginning of the eruption with over 100 alert pixels recorded on 27 June and over 50 the following day. The MIROVA system recorded an abrupt, very high thermal signal beginning on 26 June (figure 21). Seismic and acoustic data indicated a gradual decrease of activity after the initial outburst, but effusive lava flows continued on 27 June.

Figure (see Caption) Figure 20. A large plume of SO2 was emitted from Sierra Negra on 27 June 2018 at the beginning of the latest eruptive episode. It drifted SW the following day, as seen in these images captured by the OMPS instrument on the Suomi NPP satellite. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 21. The MIROVA project graph of thermal energy at Sierra Negra from 31 January 2018 through September 2108 shows the start of the lava flows on 27 June 2018 (UTC). Pulses of high thermal energy continued through late August when flow activity ceased; cooling of the flows continued into September 2018. Courtesy of MIROVA.

During 27 and 28 June, IG scientists were able to make a site visit to capture thermal, photographic, and physical evidence of the new lava flows (figure 22). A composite thermal image showed the extent of flows that traveled down the N flank as well as into the caldera (figure 23). A temperature of 580°C was measured near the eruptive fissure, and the surface temperatures averaged about 60°C, although some flows were measured as high as 200°C. The temperature inside a fracture on a lava flow was measured at 975°C (figure 24). Pelée hair and "spatter" bombs were visible around the eruptive fissures.

Figure (see Caption) Figure 22. The lava flows of 26 June 2018 at Sierra Negra emerged from a fissure on the N flank of the caldera rim and other fissures on the N flank and flowed N. N is to the right. Photo by Benjamin Bernard, courtesy of IG (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 23. Composite thermal images of the new lava flows at Sierra Negra taken on 27 June 2018 reveal the flows that emerged from the Volcán Chico fissure zone; most flows traveled N down the flank, a few (on the left) traveled down into the caldera. Images by Silvia Vallejo, courtesy of IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 24. The temperature of incandescent lava within a fresh flow at Sierra Negra was measured at 975°C on 27 June 2018. Left image by Francisco Vásconez; thermal image by Silvia Vallejo, courtesy of IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).

Pahoehoe and aa flows along with lava tunnels were visible in drone images. The visible fissures were slightly arcuate and aligned in a general ENE direction, similar to the fissures of 1979 and 2005 in the vicinity of Volcán Chico. The largest flow was more than 150 m long; they reached up to 130 m wide in the flat areas, but only between 25 and 35 m wide where they were channeled on the steeper slope. In the flatter areas they had characteristics of pahoehoe with a smooth surface, a sometimes rounded texture and lava tunnels (figure 25), while in the channelized areas with a steeper slope they had a rougher surface and were characterized as aa (figure 26). The flows averaged 0.5-1 m thick and in several places the lava filled fissures or previous depressions. The samples of pahoehoe that were collected were all aphanitic with no crystals, strongly iridescent, and vesiculated with fluid textures that indicated a high gas content and low viscosity.

Figure (see Caption) Figure 25. Pahoehoe flows, spatter, and a collapsing lava tunnel were visible near fissure 1 (above 'Spatter') at Sierra Negra when imaged by a drone during a field visit on 27-28 June 2018 shortly after the new eruptive episode began. This image covers the area near the top center of the image in figure 22 close to the fissure. Photos were taken by a drone flying 60 m above the flows by Benjamin Bernard, courtesy IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 26. Aa flows formed as lava traveled down the steeper parts of the N flank of Sierra Negra on 26 June 2018, seen in this drone image taken during a field visit on 27-28 June. This image general location can be seen in the bottom right area in figure 22. Photos were taken by a drone flying 60 m above the flows by Benjamin Bernard, courtesy IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).

A small seismic event followed by several hours of tremor was recorded at 1552 on 1 July; a short while later National Park staff observed active lava flows on the NW flank. On 4 July, IG reported a M 5.2 earthquake that was 5 km deep; it was followed by 68 smaller seismic events. On 7 July seismic tremor activity indicating another pulse of magmatic activity was recorded by a station on the NE edge of the caldera at 1700. At the same time, satellite data showed an increase in the intensity of the thermal anomaly on the NW flank; Parque Nacional Galápagos staff confirmed strong visible incandescence in an area near the beach. Tremor activity continued on 8 July, although the amplitude gradually decreased.

The Washington VAAC reported an ash plume visible in satellite imagery on 2 July at 6.1 km altitude drifting SW. Later in the day a concentrated plume interpreted to be primarily steam and gas extended about 260 km SW. On 8 July ash could be seen moving both W and SW in satellite imagery at 2.7-3.0 km altitude. Later that day ash was visible extending about 115 km SW from the summit and other gases extended 370 km W. That evening the ash plume extended about 190 km SW at 3.7 km altitude. Gas-and-ash plumes were observed continuously drifting SW for the next three days (9-11 July) at 3.7 km altitude to a distance of about 80 km. On 13 July, two areas of ash and gas were seen in satellite imagery moving 25 km NW from the summit and up to 45 km SW at altitudes of 3.9 and 2.4 km respectively. A low-level ash plume on 16 July extended 30 km SW from the summit at 2.4 km altitude; incandescence was also visible in the webcam. The next day ash and gas emissions extended about 120 km SW at a similar altitude. Ongoing steam, gas, and ash emissions were seen in satellite imagery and in the webcam extending 110 km NW from the summit on 19 July at 3.4 km altitude. The Washington VAAC reported an ash plume on 30 July that rose to 3.4 km altitude and drifted SW. Strong SO2 emissions were recorded by both the OMPS and OMI satellite instruments throughout July 2018 (figure 27).

Figure (see Caption) Figure 27. SO2 plumes from Sierra Negra exceeded 2 Dobson Units (DU) nearly every day during July 2018. Data gathered by the OMPS satellite instrument showed a large plume drifting SW on 2 July (top left), and a more narrow stream of SO2 drifting SW on 3 July (top right). The OMI satellite instrument captured large W-drifting plumes on 12 (bottom left) and 14 (bottom right) July. Courtesy of NASA Goddard Space Flight Center.

In a report issued by IGEPN covering activity through 23 July 2018, they noted that at least four fissures had initially opened on 26 June at the start of the eruption (see numbers in figure 19 at the beginning of this report, and figure 31 at the end). Fissure 1, the longest at 4 km, was located at the edge of the caldera in the area of Volcán Chico; lava flows from this fissure traveled 7 km down the flanks, and over 1 km within the interior of the caldera. NW-flank fissures 2, 3, and 4 were much smaller (about 250 m long). Fissures 1-3 were active only until 27 June; fissure 4 continued to be active throughout July. Lava from this fissure reached the ocean on 6 July.

Gas and possible volcanic ash extended 35 km SW of the summit on 4 August at 1.5 km altitude; this was the last report of an ash plume by the Washington VAAC for the eruption. Daily reports from IGEPN indicated that nightly incandescence from advancing flows continued into August. Occasional low-level steam and gas plumes were also visible. Pulses of lava effusion on 4 and 9 August were accompanied by major episodes of seismic tremor activity and substantial SO2 plumes (figure 28). On 15 August satellite images showed lava from fissure 4 continuing to enter the ocean. The area where the lavas entered the sea were far from any human population or agricultural activities and only accessible by boats.

Figure (see Caption) Figure 28. At Sierra Negra, large SO2 plumes were recorded by the OMPS instrument on the Suomi NPP satellite at the same time that an increase in seismic activity and effusion were noted on both 4 (left) and 9 (right) August 2018. Courtesy of NASA Goddard Space Flight Center.

Throughout the ongoing eruption, pulses of thermal activity detected by MODIS infrared satellite sensors correlated with increases in seismic activity and observed flow activity. The MIROVA plot showed a high level of heat flow from the onset of the eruption on 26 June gradually decreasing in intensity through mid-August (figure 21). This was followed by a significant drop in heat flow and gradual cooling thereafter. After the initial fissure activity near the crater rim on 26-27 June, all subsequent activity was concentrated farther down the N flank at fissure 4 and is reflected in the number of pixels concentrated in that area of the MODVOLC plot of thermal alerts from June-September 2018 (figure 29).

Figure (see Caption) Figure 29. MODVOLC thermal alert locations corresponded to the locations of the observed flow activity at Sierra Negra, showing the sustained thermal activity from the mid-flank fissure 4 that lasted from late June through mid-September 2018. Courtesy of HIGP - MODVOLC Thermal Alerts System .

The number of seismic events recorded during the eruptive episode had increased between 26 June and 30 July 2018 to an average of 265 per day. The peak was recorded on 29 June with 940 earthquakes. Between 31 July and 23 August, the average number was 121 per day, still higher than the level of 38 per day prior to the beginning of the eruption on 26 June. IG reported a continuous decline in activity during the last two weeks of August 2018. After the initial burst of effusive activity during 26-27 June, five additional pulses of increased thermal, seismic, and gas-emission activity were observed in multiple sources of data on 1-2, 7-8, and 31 July, and 4 and 9 August (figure 30).

Figure (see Caption) Figure 30. Multiple parameters of data from the eruption of Sierra Negra from 21 June to 30 August 2018. The dashed green line marks the start of the eruption, while the pale green vertical bars indicate the different eruptive pulses recorded throughout the eruption. a) Seismic energy data (RSAM) recorded by station VCH1, in a window between 1-8 Hz (location shown in figure 31); b) Time series of degassing of SO2 recorded by the OMI and OMPS satellites instruments; c) thermal anomalies recorded by MODVOLC. Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018), also published in Vasconez et al (2018).

In a summary report on 31 August 2018, IG reported that the eruption was divided into two main phases. The first and most energetic phase lasted one day (26 June) and was characterized by the opening of five fissures (table 2) located on the rim and N and NW flanks, and creation of lava flows that traveled as far as 7 km from the vents (figure 31). Lava was only active from all five fissures during the first day of the eruption, covering an area greater than 17 km2. During the rest of the eruption from 27 June-23 August, about 13 km2 of lava was produced from fissure 4, with lava reaching the sea on 6 July and expanding the coastline by 1.5 km2. Detailed descriptions of the fissures provided by IGEPN are given in the following section. By 25 August the lava flows covered an area of 30.6 square kilometers. Activity continued to decline the last week of August with decreased seismicity, gas emission, and no surficial activity visible.

Figure (see Caption) Figure 31. Map of the 26 June-August 2018 eruption of Sierra Negra volcano. The eruptive fissures are numbers and shown in yellow and described in detail in the next section. The coastline with Elizabeth Bay is shown in blue, and the lava flows appear in red. The green points include GPS and seismic stations, the epicenter of the earthquake of 5.3 MLV on 26 June, El Cura (control station of the Galápagos National Park) and the panoramic vista visited by tourists. Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018), also published in Vasconez et al (2018).

Table 2. Descriptions of the five fissures active during the June-August 2018 eruption of Sierra Negra (see figure 31 for locations). Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018)

Feature Location Description
Fissure 1 Edge of the caldera in the Volcán Chico area, trending WNW, tangential to the edge of the caldera. Four kilometers in length with lava flows that moved toward both the interior of the caldera and down the flank from the beginning of the eruption until 27 June, covering an area of 14.6 km2. The flows deposited outside the crater traveled 7 km downhill, without reaching the sea, while those inside it reached a maximum distance of 1.1 km.
Fissure 2 NW of the caldera about 3 km below its edge of the caldera at an elevation of 700 m. Approximately 250 m long and produced 4-km-long lava flows from the beginning of the eruption until 27 June, covering an area of 2.2 km2; its lava did not reach the sea.
Fissure 3 WNW of the caldera about 4 km below its edge at an elevation of 550 m. Approximately 250 m long and active from the beginning of the eruption until 27 June, emitting lava flows that covered an area of about 0.4 km2. The lava flows had a length of about 2 km and did not reach the sea.
Fissure 4 NW flank at an elevation of 100 m between 7 and 8 km below the rim of the caldera. Continuously emitting lava flows throughout the eruption. It was located on the On 6 July the lava flows from this fissure reached the ocean and modified the coastline of Isla Isabela by 1.5 km2. By 25 August when active flow ceased, its lavas had covered an area of approximately 13.3 km2.
Fissure 5 Western flank at an elevation of 840 m, 1.5 km downhill from the inner edge of the caldera. Length of 170 m and covered 0.026 km2.

References: Davidge L, Ebinger C, Ruiz M, Tepp G, Amelung F, Geist D, Cote D, Anzieta J, 2017, Seismicity patterns during a period of inflation at Sierra Negra volcano, Galápagos Ocean Island Chain. Earth and Planetary Science Letters. 462. DOI: 10.1016/j.epsl.2016.12.021.

Geist D, Naumann T R, Standish J J, Kurz M D, Harpp K S, White W M , Fornari D, 2005, Wolf Volcano, Galapagos Archipelago: Melting and magmatic evolution at the margins of a mantle plume. Journal of Petrology 46:2197-2224.

Vasconez F, Ramón P, Hernandez S, Hidalgo S, Bernard B, Ruiz M, Alvarado A., La Femina P, Ruiz G, 2018, The different characteristics of the recent eruptions of Fernandina and Sierra Negra volcanoes (Galápagos, Ecuador), Volcanica 1(2): 127-133. DOI: 10.30909/vol.01.02.127133.

Geologic Background. The broad shield volcano of Sierra Negra at the southern end of Isabela Island contains a shallow 7 x 10.5 km caldera that is the largest in the Galápagos Islands. Flank vents abound, including cinder cones and spatter cones concentrated along an ENE-trending rift system and tuff cones along the coast and forming offshore islands. The 1124-m-high volcano is elongated in a NE direction. Although it is the largest of the five major Isabela volcanoes, it has the flattest slopes, averaging less than 5 degrees and diminishing to 2 degrees near the coast. A sinuous 14-km-long, N-S-trending ridge occupies the west part of the caldera floor, which lies only about 100 m below its rim. Volcán de Azufre, the largest fumarolic area in the Galápagos Islands, lies within a graben between this ridge and the west caldera wall. Lava flows from a major eruption in 1979 extend all the way to the north coast from circumferential fissure vents on the upper northern flank. Sierra Negra, along with Cerro Azul and Volcán Wolf, is one of the most active of Isabela Island volcanoes.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nature Galápagos (Twitter: @natureGalápagos, https://twitter.com/natureGalápagos).


Great Sitkin (United States) — September 2018 Citation iconCite this Report

Great Sitkin

United States

52.076°N, 176.13°W; summit elev. 1740 m

All times are local (unless otherwise noted)


Small phreatic explosions in June and August 2018; ash deposit on snow near summit

Episodic recent and historic volcanic activity has been reported at Great Sitkin, located about 40 km NE of the community of Adak in the Aleutian Islands. Prior to the recent 2018 activity, the last confirmed eruption in 1974 produced at least one ash cloud that likely exceeded an altitude of 3 km (figures 1 and 2). This eruption extruded a lava dome that partially destroyed an existing dome from a 1945 eruption. Most recently, a small steam explosion was reported on 10 June 2018. In response, the Alaska Volcano Observatory (AVO) raised the Aviation Color Code (ACC) to Yellow (Advisory) from the previous Green (Normal).

Figure (see Caption) Figure 1. Eruption of Great Sitkin volcano in 1974. Photo taken from Adak Island, Alaska, located 40 km SW of the volcano. Photographer/Creator: Paul W. Roberts; courtesy of AVO/USGS (color corrected).
Figure (see Caption) Figure 2. Worldview-3 satellite image of Great Sitkin on 21 November 2017 showing the crater, areas of 1974 and 1945 lava flows, and steam (indicated by the red arrow) from the reported seismic swarm and steam event ending in 2017. Photographer/Creator: Chris Waytomas; image courtesy of AVO/USGS.

AVO had previously reported that a seismic swarm had been detected beginning in late July 2016 and continuing through December 2017. Steam from the crater was also observed during this time period, in late November 2017 (figure 2). The seismicity was characterized by earthquakes typically less than magnitude 1.0 and at depths from near the summit to 30 km below sea level. Most earthquakes were in one of two clusters, beneath the volcano's summit or just offshore the NW coast of the island. Possible explosion signals were observed in seismic data on 10 January and 21 July 2017, but no confirmed emissions were observed locally or detected in infrasound data or satellite imagery.

The most recent eruption at Great Sitkin produced a small steam explosion which was detected in seismic data at 1139 local time on 10 June 2018 (figure 3). The explosion was followed by seismic activity which began diminishing after 24 hours, and by 15-16 June had returned to background levels.

Figure (see Caption) Figure 3. View of Great Sitkin steaming on 10 July 2018. Photographed from Adak Island, Alaska, approximately 40 km SW. Photo by Alain Beauparlant; image courtesy of AVO/USGS (color corrected).

Due to heavy cloud cover on 10 June 2018, satellite views were obscured. Subsequent satellite data collected on 11 June showed an ash deposit on the surface of the snow extending to about 2 km SW from a vent in the summit crater (figure 4). Minor changes in the vicinity of the summit crater were observed from satellite data, including possible fumaroles north of the main crater. On 17 June an aerial photograph showed minor steaming at the vent (figure 5).

Figure (see Caption) Figure 4. Satellite view of the Great Sitkin crater at 2300 UTC on 11 June 2018 showing an ash deposit extending for about 2 km to the SW. Ash was likely deposited during the brief explosion on 10 June 2018. Minor steaming from a vent through the 1974 lava flow is also visible in this image. View is from the southwest. Photographer/Creator: David Schneider; image courtesy of AVO/USGS.
Figure (see Caption) Figure 5. Aerial photo showing minor steaming at the summit of Great Sitkin, 17 June 2018. A small ash deposit extends SW from the vent. Photographer: Alaska Airlines Captain Dave Clum; image courtesy of AVO/USGS.

Another small phreatic explosion was observed in seismic data at 1105 local time on 11 August. Small local earthquakes preceded the event but were not recorded following the explosion. The event is similar to three other phreatic explosions that have occurred over the past 2 years.

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/).


Alaid (Russia) — September 2018 Citation iconCite this Report

Alaid

Russia

50.861°N, 155.565°E; summit elev. 2285 m

All times are local (unless otherwise noted)


Small ash plume reported on 21 August 2018

Sporadic ash and gas-and-ash plumes and strong thermal anomalies were reported from Alaid, in Russia's Kurile Islands, between 29 September 2015 and 30 September 2016 (figure 8). The Kamchatka Volcanic Eruptions Response Team (KVERT), which monitors the volcano, interpreted the thermal anomalies as Strombolian activity and a lava flow (BGVN 42:04). The current report summarizes activity during October 2016 through August 2018.

Figure (see Caption) Figure 8. Aerial photo of the Alaid summit area on 28 April 2016, with fresh lava filling the crater, a cinder cone in the southern part of the crater, and a lava flow on the SW flank. Photo by L. Fugura; courtesy of IVS FEB RAS, KVERT.

According to KVERT weekly reports, the Aviation Color Code for Alaid was Green (Volcano is in normal, non-eruptive state) throughout the reporting period. The only reported activity was from the Tokyo Volcanic Ash Advisory Center, which reported that on 21 August 2018, an ash plume identified in Himawari-8 satellite images rose to an altitude of 2.7 km (about 500 m above the summit) and drifted SE. The plume was clearly visible on imagery starting at 0830 Japan Standard Time (UTC + 9 hours), and remained noticeable for at least 4 hours. There were no other satellite or ground-based observations of this activity.

Figure (see Caption) Figure 9. Himawari-8 satellite image from 21 August 2018 at 1030 JST (UTC + 9 hours) showing a small ash plume drifting SE from Alaid towards Paramushir Island. Alaid is the small island NW of the larger Paramushi Island and directly W of the southern tip of the Kamchatka Peninsula. Courtesy of Himawari-8 Real-time Web.

Geologic Background. The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago. Numerous pyroclastic cones dot the lower flanks of this basaltic to basaltic-andesite volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.

Information Contacts: Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Himawari-8 Real-time Web, developed by the NICT Science Cloud project in NICT (National Institute of Information and Communications Technology), Japan, in collaboration with JMA (Japan Meteorological Agency) and CEReS (Center of Environmental Remote Sensing, Chiba University) (URL: https://himawari8.nict.go.jp/).


Aira (Japan) — August 2018 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Activity increased at Minamidake and decreased at Showa crater in early 2018

Sakurajima is a persistently active volcano within the Aira caldera in Kyushu, Japan. The two currently active summit craters are Showa and Minamidake, both of which produce intermittent ash plumes and occasional pyroclastic flows. This report summarizes the activity from January through June 2018 as described in reports issued by the Japan Meteorological Agency (JMA) and Tokyo Volcanic Ash Advisory Center (VAAC).

The volcano remains on Alert Level 3 (out of five). A change in activity occurred in late 2017 to early 2018, with a reduction in activity at the Showa crater and a significant increase in activity at the Minamidake crater (table 19 and figure 63). During January through June 2018 a total of 260 explosions were recorded at Minamidake (135 of these were explosive), and four at Showa. Pyroclastic flows were produced on 1 April from Showa crater that travelled 800 m, and a flow reached 1,300 m from Minamidake crater on 16 June. Periodic incandescence was visible at the summit throughout the reporting period.

Table 19. Eruptive events and pyroclastic flows recorded at the active craters of Sakurajima volcano in Aira caldera. The number of events that were explosive in nature are in parentheses. Data courtesy of JMA (January to June 2018 monthly reports).

Month No. of ash emissions at Showa crater No. of ash emissions at Minamidake crater Pyroclastic flows
Jan 2018 1 12 (4) --
Feb 2018 0 7 (3) --
Mar 2018 0 44 (17) --
Apr 2018 3 66 (50) 800 m E from Showa.
May 2018 0 96 (48) --
Jun 2018 0 35 (13) 1,300 m SW from Minamidake.
Figure (see Caption) Figure 63. The number of monthly explosions at Minamidake (upper) and Showa (lower) craters of Sakurajima, Aira caldera. The first half of 2018 has seen a dramatic increase in activity at Minamidake, and a decrease in activity at Showa crater. Grey bars indicate eruptions and red bars specify explosive eruptions. Note that the scale on the two graphs are different. Courtesy of JMA (June 2018 monthly report).

In January 2018, one ash emission occurred at Showa crater and twelve occurred at Minamidake, with four of these classified as explosive eruptions. The largest ash plume reached 2,500 m above the crater on the 18th and two explosions ejected material out to a maximum of 700-800 m from the craters. Through February, three of seven ash emissions at Minamidake were explosive. The largest ash plume occurred on the 19th and reached 1,500 m above the crater. On the 27th, the crater ejected material out to 700 m from the crater.

Through March, 44 ash emissions occurred with 17 of these classified as explosive events. The largest ash plume was produced on the 26th and reached 3,400 m above the crater. An explosive eruption on 10 March ejected material out to 1,300 m from the crater. During April, Minamidake produced 66 ash emission; 50 of these were explosive (figure 64). Showa produced three events in total and an event on 1 April produced a pyroclastic flow that traveled 800 m to the E (figure 65).The largest ash plume was from Minamidake that reached 3,400 m above the crater.

Figure (see Caption) Figure 64. True color Sentinel-2 satellite image of an ash plume at Sakurajima, Aira caldera, at 1056 on 12 April. The Tokyo VAAC reported that the plume that reached an altitude of 2.4 km. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 65. Eruption of the Sakurajima Showa crater (within the Aira caldera) at 1611 on 1 April. The ash plume rose to 1,700 m above the crater and the pyroclastic flow (circled) travelled 800 m to the east. Image taken by the Kaigata webcam, courtesy of JMA (April 2018 monthly report).

Elevated activity continued at Minamidake through May, with 96 ash emissions (48 explosive), and the highest reported ash plume reaching 3,200 m above the crater on the 24th. An explosion on 5 May scattered ejecta out to 1,300 m from the crater. Activity was reduced in June with 35 ash emissions (13 explosive) from Minamidake, with an explosive event on the 16th producing an ash plume to 4,700 m above the crater and a pyroclastic flow out to 1,300 m (figure 66). This event deposited ash on nearby communities.

Figure (see Caption) Figure 66. Eruption at the Sakurajima Minamidake crater (at Aira caldera) at 1607 on 16 June. The ash plume rose to 4,700 m above the crater and the pyroclastic flow (circled) traveled 1,300 m. Image captured by the Kaigata surveillance camera, courtesy of JMA (June 2018 monthly report).

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Suwanosejima (Japan) — August 2018 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Intermittent ash emission continues from January through June 2018

Suwanosejima volcano is located in the northern Ryukyu Islands in the south of Japan and has been on Alert Level 2 since December 2007. This report is a summary of activity for the period January to June 2018 and is based on information from the Japan Meteorological Agency (JMA) along with Tokyo VAAC notices.

During the reporting period, the active Ontake crater produced intermittent explosions that scattered ejecta around the crater and ash plumes to an altitude of 1.5-3 km. Ashfall was reported in a village 4 km away on 10 days during January-May 2018 (table 14). Incandescence was visible at night using monitoring equipment. Ash plumes were noted by the Tokyo Volcanic Ash Advisory Center (VAAC) throughout the reporting period (figure 32, table 15).

Table 14. Reported explosion information for Suwanosejima recorded in JMA monthly reports.

Month No. of explosions Max plume height (m above crater) Dates of ashfall in village 4 km SSW No. of seismic events Other daily activity detail
Jan 2018 0 1,100 27, 31 97 Incandescence at night.
Feb 2018 1 1,100 2, 3 100 Incandescence at night.
Mar 2018 9 2,200 25, 29 251 Incandescence at night. Ejecta scattered around the crater.
Apr 2018 8 2,000 18, 28, 29 62 Incandescence at night.
May 2018 2 1,100 14 90 Incandescence at night. Ejecta scattered around the crater.
Jun 2018 -- 900 -- 275 Incandescence at night.

Table 15. Number of Volcanic Ash Advisories, explosion dates, and plume heights for activity at Suwanosejima. The numbers in parentheses indicate the number of events on that date; the VAACs issued column does not include advisories that note a continued episode. Drift directions were highly variable. Data courtesy of Tokyo VAAC.

Month VAAs issued VAA dates Plume heights
Jan 2018 1 15 1.8 km
Feb 2018 1 2 1.2 km
Mar 2018 22 17, 22(3), 23, 25(2), 26(5), 27(5), 28(3), 29(2) 1.2-3.6 km
Apr 2018 16 1, 2, 3, 4(4), 5(2), 8, 11, 24, 27, 28(2) 1.2-2.4 km
May 2018 3 1, 4, 15 1-1.8 km
Jun 2018 1 1 --
Figure (see Caption) Figure 32. An ash plume at Suwanosejima reached 1 km above the crater on 3 February 2018. Image captured by the Kyanpuba webcam, courtesy of JMA (February 2018 monthly report).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Etna (Italy) — August 2018 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3295 m

All times are local (unless otherwise noted)


Degassing continues, accompanied by intermittent ash emissions and small Strombolian explosions in June and July 2018

Etna is the tallest active volcano in continental Europe with persistent activity at multiple summit craters and vents. The active craters are Bocca Nuova and Voragine within the Central Crater, the Northeast Crater, Southeast Crater, and the New Southeast Crater (figure 217). This report summarizes activity from April to July 2018 and is based on reports by the Istituto Nazionale di Geofisica e Vulcanologia (INGV).

Figure (see Caption) Figure 217. The active summit craters of Etna volcano: the Bocca Nuova and Voragine craters that occupy the older Central Crater, the Northeast Crater (Cratere di Nord-Est), Southeast Crater (Cratere di Sud-Est), and the New Southeast Crater (Nuovo Cratere di Sud-Est). The years given in parentheses indicate when the craters formed. Photo by Marco Neri, courtesy of INGV (19 July 2018 blog).

Activity through April was characterized by degassing at the summit craters (figure 218), with modest ash emissions from the New Southeast Crater and Northeast Crater in the first week, and occasional small ash emissions at the end of the month. Reduced activity dominated by degassing continued into May with modest ash emission from the Southeast and Northeast craters during the second week, and isolated ash emissions from the Northeast Crater in the second half of the month continuing into June.

Figure (see Caption) Figure 218. Degassing at the Bocca Nuova crater at the summit of Etna in late April. The top image is a photograph of the crater with the location of the bottom image, which is a thermal image showing the degassing and temperature at the vent reaching over 400°C. Courtesy of INGV (Weekly report No. 18/2018 for 24 to 30 April 2018, issued on 2 May 2018).

Throughout June the activity consisted of degassing at the summit craters with isolated diffuse ash emission from Northeast Crater (figure 219). This continued through to July until low-energy Strombolian activity commenced in the Bocca Nuova (from two vents) and Northeast craters (figures 220 and 221). The Strombolian explosions were small, lasting up to several tens of seconds, and were sometimes accompanied by red-brown ash emission. The ejected material was confined to within the craters. More energetic bursts were visible from the INGV surveillance camera located in Milo.

Figure (see Caption) Figure 219. Photos of isolated dilute red-brown ash emissions from the Etna Northeast Crater on the 6 and 8 June. Courtesy of INGV (Report No. 24/2018 for the period 4 to 10 June 2018, issued on 12 June 2018).
Figure (see Caption) Figure 220. A sequence of thermal infrared images of a Strombolian explosion at the Etna Bocca Nuova crater on 17 July 2018. Two vents are active (A and B), with vent B ejecting lava up to a few tens of meters above the vent. The color scale on the right of the images indicates the temperature in Celsius. Images taken by Giuseppe Salerno, courtesy of INGV (24 July 2018 INGV blog).
Figure (see Caption) Figure 221. Photos of Strombolian explosions at the base of the Etna Northeast Crater on 20 and 21 July 2018. The explosions occur when gas pockets burst and eject incandescent fluid lava above the vent. Photo by Michele Mammino, courtesy of INGV (24 July 2018 blog).

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Blog INGVvulcani, Istituto Nazionale di Geofisica e Vulcanologia (INGV) (URL: http://ingvvulcani.wordpress.com).


Stromboli (Italy) — August 2018 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Continued Strombolian activity from five active summit vents through March-June 2018

Stromboli is a persistently active volcano in the Aeolian Islands, Italy, with confirmed historical eruptions going back over about 2,000 years. The active summit craters on the crater terrace are situated above the Sciara del Fuoco, a steep talus slope on the NW side of the island that leads to the Tyrrhenian Sea below. The NE crater (Area N) includes the active N1 and N2 vents, while the Central and SW craters (Area CS) contains the C, S1, and S2 vents (figures 125 and 126).

Figure (see Caption) Figure 125. False color thermal Sentinel-2 satellite image of Stromboli volcano with the locations of the Sciara del Fuoco and the active craters and vents. Four of the active vents are visible in this image as bright yellow-orange areas. Image acquired on 27 June 2018 and processed using bands 12, 11, 4. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 126. Thermal image of the Stromboli crater terrace area showing the N (area N), and the central and S (area CS) craters with the active vents. Image taken by the Pizzo webcam, courtesy of INGV (report number 11/2018 for the period 5 to 11 March, released on 13 March 2018).

Typical activity comprises degassing and multiple explosions per hour that range from tens of seconds to a few minutes, known as Strombolian activity, which is named after this particular volcano (figure 127). The activity usually consists of low-intensity explosions that eject material (ash, lapilli, and blocks) up to 80 m above the crater and medium-low intensity explosions that eject material up to 120 m above the crater. This report describes the activity at Stromboli through March to June 2018 and summarizes reports published by the Istituto Nazionale di Geofisica e Vulcanologia (INGV).

Figure (see Caption) Figure 127. The daily frequency of explosions per hour produced by all the active vents at Stromboli during the period 1 January to 2 July 2018. Red indicates explosions within the N crater, green indicates activity at the central-S craters, and blue indicates the number of total events. Courtesy of INGV (report number 27/2018 for the period 25 June to 7 July, released on 3 July 2018).

Characteristic Strombolian activity occurred throughout March, typically consisting of 5-11 events per hour that ejected material up to 120 m above the craters. High-energy explosive events occurred on 7 and 18 March, both lasting around 40 seconds and ejecting material to a height of 400 m (figures 128 and 129).

Figure (see Caption) Figure 128. A high-energy explosive event on 7 March 2018 at the N2 vent of Stromboli. Top images (frames a to c) are thermal images, with the corresponding visible images across the bottom (frames d to f). Images were taken by the Pizzo webcams, courtesy of INGV (report number 11/2018 for the period 5 to 11 March, released on 13 March 2018).
Figure (see Caption) Figure 129. Thermal infrared images of the high-energy explosive event on 18 March 2018 at Stromboli. The images show approximately 40 seconds of the explosive sequence recorded by the Pizzo webcam, courtesy of INGV (report number 12/2018 for the period 12 to 18 March, released on 20 March 2018).

Typical Strombolian activity continued through April with 6-12 explosive events per hour, with two high-energy explosive events on 24 and 26 April that lasted nine and three minutes, respectively. Both events ejected material across the Sciara del Fuoco, producing ash plumes and lava fountaining (figure 130). Low to medium-low intensity activity continued through May and June, with explosions per hour in the range of 3-15 and 6-13, respectively.

Figure (see Caption) Figure 130. INGV noted an intense explosive sequence on 26 April 2018 at Stromboli. Top images (frames A to C) show the thermal signature of the explosion; bottom images (frames G to I) are the corresponding visible images. The sequence produced abundant ash, incandescent material, lava fountaining, and ejected large blocks to a height of 250 m above the vent that then fell around the crater and on the Sciara del Fuoco. Courtesy of the INGV (Blog INGVvulcani entry for 16 July 2018).

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period from about 13,000 to 5000 years ago was followed by formation of the modern edifice. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5000 years ago as a result of the most recent of a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/en/); Blog INGVvulcani, Istituto Nazionale di Geofisica e Vulcanologia (INGV) (URL: https://ingvvulcani.wordpress.com/2018/07/16/stromboli-e-le-sue-esplosioni/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Agung (Indonesia) — August 2018 Citation iconCite this Report

Agung

Indonesia

8.343°S, 115.508°E; summit elev. 2997 m

All times are local (unless otherwise noted)


Ash explosions and lava dome effusion continue during January-July 2018

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung was quiet until a new eruption began in November 2017 (BGVN 43:01). A lava dome emerged into the summit crater at the end of November and intermittent plumes of ash rose as high as 3 km above the summit through the end of the year. Activity continued into 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the growth of the lava dome within the summit crater. Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from January through July 2018.

Intermittent explosions with ash plumes were reported at Agung several times during January 2018, including Strombolian activity on 19 January. Activity decreased significantly by the end of the month; only one explosion with ash was reported during February. Two ash plumes were reported in March and three were reported each month during April and May. A more substantial explosion in mid-June produced an ash plume that rose to 7 km altitude. A series of deep-seated earthquakes during the third week of June was followed by large explosions and new effusions of lava inside the summit crater beginning on 28 June. A strong thermal signal also appeared on 28 June that gradually diminished during July. Intermittent plumes of steam and ash recurred daily until 19 July; plume heights rose up to 3 km above the summit on several occasions. Strombolian explosions on 2 and 8 July sent ejecta as far as 2 km from the summit. Explosive activity became more intermittent during the last two weeks of the month; the last reported explosion was on 27 July.

Activity during January-May 2018. During most days of January 2018 when fog was not obscuring the summit, PVMGB reported plumes of steam and minor ash rising about 500 m above the summit. In addition, intermittent explosions produced higher, denser ash plumes that rose 1,000-2,500 m above the summit several times. Ash plumes on 1 and 2 January rose to 1,000 and 1,500 m above the summit; incandescence was observed at the summit on both nights, and trace ashfall was reported at the Rendang Post on 2 January. The Darwin VAAC reported the ash plume on 1 January at 6.1 km altitude moving SW. A single MODVOLC thermal alert was recorded on 4 January. On 5 January PVMGB lowered the evacuation radius from 10 to 6 km, permitting the return of thousands of displaced people to their homes. Approximately 17,000 people in seven villages within 6 km of Agung were still under evacuation orders from the events of late 2017.

The Agung Volcano Observatory issued VONA's (Volcano Observatory Notice for Aviation) on 4, 8, 9, 11, 15, 17, 19, 23, 24, and 30 January relating to the larger explosions and ash plumes. On 11 January, an ash plume rose to 2,500 m above the summit and drifted N and NE (figure 29). Another 2,500-m-high ash plume on 19 January was accompanied by Strombolian activity at the summit for several hours, and incandescent ejecta that traveled 1,000 m from the crater. Ashfall was later reported in Tulamben village in the Kubu district (9 km NE) and in Purwekerti village in the Abang district (14 km ENE). Visual monitoring using drones carried out on 22 January showed that the volume of the lava dome was relatively unchanged at around 20 million m3. The summit was obscured by fog for the last week of the month.

Figure (see Caption) Figure 29. An eruption at Agung on 11 January 2018 sent an ash plume to 2,500 m above the summit. Courtesy of MAGMA Indonesia and PVMBG (Erupsi Gunung Agung 11 Januari 2018 17:54 WITA).

Activity decreased noticeably in late January and February. Steam and minor ash plumes rose only 50-800 m above the summit for most of the month. As a result of the decrease in activity, PVMBG lowered the Alert Level from Level IV to Level III (on a four-level scale) on 10 February 2018. The radius of evacuation was also lowered from 6 to 4 km. A single explosion on 14 February sent an ash plume to 1,500 m above the summit.

For most of March 2018, steam plumes rose less than 400 m above the summit. VONA's were issued by the Agung Volcano Observatory for ash plumes twice, on 12 March (local time) when a plume rose 800 m above the summit and drifted E, and on 26 March when the ash plume rose to 500 m and drifted NW. During much of April 2018, steam plumes rose less than 300 m above the summit; weather obscured views of the summit for most of the last week of the month. AVO issued VONA's for ash plumes on 6, 11 and 30 April; the plumes on 6 and 11 April rose 500 m and drifted W and SW respectively. The Darwin VAAC reported a series of four short-lived explosions with ash plumes on 11 April; they each dissipated within a few hours. PVMBG reported another explosion on 15 April that produced an ash plume that also rose 500 m. The plume on 30 April rose 1,500 m and drifted SW.

Similar activity persisted throughout May 2018. Steam plumes generally rose 50-100 m above the summit crater each day. In addition, explosions were reported on 9, 19, and 29 May. PVMBG reported that no ash plume was observed on 9 May, due to fog obscuring the summit, but the ash plume on 19 May rose to 1,000 m above the summit and drifted SE, and the ash plume on 29 May rose 500 m and drifted SW.

Activity during June and July 2018. The volcano was covered in fog for much of the first two weeks of June. A short-lived explosion on 10 June 2018 was reported by PVMBG, but meteoric clouds obscured the summit. The Darwin VAAC noted the plume in a satellite image drifting W at about 4.6 km altitude. An explosion on 13 June produced an ash plume that rose 2,000 m above the summit and drifted WSW (figure 30). Another explosion was recorded on 15 June, but the summit was obscured, and no ash cloud was visible to ground observers. However, the Darwin VAAC reported the plume visible in satellite imagery at 7 km altitude (about 4 km above the summit) drifting SW and S for most of the day before dissipating. Ashfall was reported about 7 km W in the village of Puregai. PVMBG reported white and gray emissions on 17 June that rose 500 m.

Figure (see Caption) Figure 30. An ash plume at Agung on 13 June 2018 rose about 2,000 m above the summit and drifted WSW. View is looking N. Courtesy of PVMBG (Information on G. Agung Eruption, 13 June 2018).

An explosion during the evening (local time) of 27 June 2018 produced an ash plume that rose 2,000 m from the summit and drifted W. Another explosion the following morning produced a sustained ash cloud that lasted for several hours and again caused ashfall around the village of Puregai. It rose to about 2,000 m above the summit and drifted W and SW (figure 31).

Figure (see Caption) Figure 31. A sustained ash eruption began early on 28 June 2018 at Agung (top) and lasted well into the afternoon (bottom). Photo from a PBVBG webcam, posted on Twitter by Sutopo Purwo Nugroho‏ (BNPB).

PVMBG noted in late June that inflation of 5 mm had occurred since 13 May 2018. They reported that the ash plumes on 28 June caused some airlines to cancel flights to Bali, and ashfall was reported in several villages in Bangli and areas to the W and SW the following day (figure 32). The International Gusti Ngurah Rai (IGNR) airport (60 km SW) in Denpasar, the Blimbing Sari Airport (128 km W) in Banyuwangi, and the Noto Hadinegoro Airport (200 km W) in Jember closed for portions of the day on 29 June (ANTARA News).

Figure (see Caption) Figure 32. Settlement and plantation areas were coated with ash from Mount Agung in Pemuteran Village (10 km W) on 29 June 2018. Courtesy of Tempo.com and ANTARA/Nyoman Budhiana.

Incandescence overnight on 28-29 June indicated fresh effusions of lava at the summit; they were accompanied by ash emissions that rose 1,500-2,500 m. Thermal satellite images recorded on 29 June indicated significant hotspots within the crater with thermal energy reaching 819 Megawatts; this was the largest amount of thermal energy recorded during the 2017-2018 activity, significantly higher than the maximum recorded of 97 Megawatts reached at the end of November 2017. The MIROVA data clearly reflected the sudden surge of thermal energy into the summit crater at the end of June (figure 33).

Figure (see Caption) Figure 33. A large spike in thermal energy beginning on 28 June 2018 signaled a new surge of lava into the summit crater at Agung. This MIROVA plot of Log Radiative Power showed pulses of activity in early January, May, and early June, followed by the much larger surge of heat in late June that tapered off throughout July. Inset shows the nighttime incandescence on 28 June 2018 that resulted from the new effusion of lava. Photo taken at the PGMBG Webcam in Batu Lompeh (15 km N). Graph courtesy of MIROVA, photo courtesy of PVMBG (Press Release of Mount Agung's Latest Activities, June 29 to 3:00 p.m.)

The Darwin VAAC reported continuous emissions of ash beginning on 28 June that drifted to the W for over 24 hours. The height was initially reported by ground observers at 3.7 km altitude but was raised to 7 km altitude a few hours later, based on satellite imagery and pilot reports. By late that day, an upper plume (at 7 km) drifted SW and a second plume drifted W at 5.5 km altitude. By late on 29 June the continuous ash plume was drifting NW at 4.9 km altitude; it finally dissipated early on 30 June. In addition to large ash plumes and a major thermal anomaly, a substantial SO2 plume also emerged from Agung on 28-29 June 2018. The plume drifted W over Java and then dispersed to the NW over the next 24 hours (figure 34). A lingering, smaller plume was still visible two days later.

Figure (see Caption) Figure 34. A substantial SO2 plume was released from Agung during 28-29 June 2018 and captured by both the OMPS instrument on the Suomi satellite (upper images) and the OMI instrument on the Aura satellite (lower images). The plume first appeared on 28 June (top left) and was much larger the next day (top right). By 30 June it was dissipating over Java to the W and N (bottom left). A smaller plume drifted SW two days later (bottom right). Courtesy of NASA Goddard Space Flight Center.

A series of discrete eruptions lasting from late on 30 June through 2 July 2018 produced ash plumes that rose from 3.7 to 5.5 km altitude and drifted NW and W, according to the Darwin VAAC. Effusive activity continued to increase during the first week of July 2018 with the continued growth of the lava dome in the summit crater. PVMBG reported an additional volume of lava of 4 million m3 erupted from 28 June through the middle of July bringing the size of the dome to about 27 million m3. The frequency of explosions peaked on 2 July when Strombolian activity sent incandescent ejecta 2 km from the summit in all directions (figure 35).

Figure (see Caption) Figure 35. The eruption of Mount Agung on 2 July 2017 produced Strombolian activity and incandescent ejecta that traveled 2 km from the summit crater in all directions. Courtesy of ANTARA News/HO/BMKG.

Several VONA's issued during 2-3 July reported multiple explosions that sent ash plumes 700-2,000 m above the summit. Eighteen explosions were reported by PVMBG between 1 and 8 July. The Darwin VAAC noted a substantial explosion early on 2 July that produced a plume that rose to 7.6 km altitude and drifted W. The remains of the ash plume were discernable in satellite imagery about 250 km W of Agung by the end of the day. The ash plume on 4 July rose 2,500 m above the summit (figure 36).

Figure (see Caption) Figure 36. An explosion at Agung on 4 July 2018 produced an ash plume that rose 2,500 m above the summit, according to PVMBG. Courtesy of PVMBG (Information on G. Agung Eruption, July 4, 2018).

Strombolian activity was reported again on 8 July 2018 (figure 37). The Darwin VAAC reported intermittent explosions every day from 3-19 July, with ash plumes rising to altitudes from 3.7 to 6.7 km. Additional explosions were reported on 21, 24, 25, and 27 July (figure 38); ash plumes rose 700-2,000 m and drifted W or SE. MODVOLC thermal alerts resumed on 27 June, and multiple daily alerts persisted on most days through the end of July.

Figure (see Caption) Figure 37. Strombolian activity at Agung recurred for the third time in 2018 on 8 July 2018. Courtesy of PVMBG (Agung Strombolian Eruption Today July 8, 2018).
Figure (see Caption) Figure 38. A dense ash plume rose about 2,000 m above Mount Agung on 27 July 2018 at 1406 local time. Courtesy of PVMBG (Information on G. Agung Eruption, 27 July 2018).

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sutopo Purwo Nugroho?, BNPB, Twitter (URL: https://twitter.com/Sutopo_PN); TEMPO.CO, Tempo Building, Jl. Palmerah Barat No. 8, South Jakarta 12210, Indonesia (URL: https://nasional.tempo.co/read/1102118/pvmbg-energi-thermal-erupsi-gunung-agung-kali-ini-paling-besar); ANTARANEWS.com, ANTARA guesthouse lt 19, Jalan Merdeka Selatan No. 17, Jakarta Pusat, Indonesia, (URL: https://en.antaranews.com).


Fernandina (Ecuador) — August 2018 Citation iconCite this Report

Fernandina

Ecuador

0.37°S, 91.55°W; summit elev. 1476 m

All times are local (unless otherwise noted)


Brief eruptive episode 16-22 June 2018, lava flows down N flank into the ocean

Eruptions at Fernandina Island in the Galapagos often occur from vents located around the caldera rim along boundary faults and fissures, and occasionally from side vents on the flank. The last eruption in September 2017 lasted for about one week and originated from a fissure at the SW rim of the caldera. A new eruption in June 2018 lasted for less than a week and originated from a fissure on the N flank of the volcano. Information about the latest eruption was provided by Ecuador's Institudo Geofisica, Escuela Politécnica Nacional (IG-EPN), the Dirección del Parque Nacional Galápagos (PNG), the Washington Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.

A seismic swarm on 16 June 2018 preceded a brief eruptive episode at Fernandina that lasted from 16 to 22 June. Lava erupted from a radial fissure and quickly flowed to the sea down the N flank. Emissions were primarily gas with low ash content and included substantial SO2. After two days of activity, seismicity returned to background levels on 18 June. Park Officials reported only cooling flows and lava no longer entering the sea by 21 June 2018.

Eruption of June 2018. The first evidence of a new eruptive event at Fernandina began as a seismic swarm on 16 June 2018. The largest event (M 4.1) was located 4 km off the NE flank of the island. An active eruption was confirmed a few hours later by guides on a passing boat and by satellite images which indicated a thermal anomaly on the N flank. The eruption consisted of a lava flow on the NNE flank and a gas plume that rose 2-3 km and drifted SW (figure 32). The lava flow quickly reached the ocean, generating steam and gas explosions that were visible from Canal Bolívar, the narrow channel on the NE side of Isla Fernandina that separates it from Isla Isabela (figure 33).

Figure (see Caption) Figure 32. Lava from a new eruption at Fernandina flowed quickly down the N flank of the island to the ocean on 16 June 2018, according to Parque Nacional Galapagos officials. Courtesy of Parque Nacional Galapagos.
Figure (see Caption) Figure 33. Explosions produced large plumes of steam as lava reached the ocean on the N flank of Fernandina on 16 June 2018. Courtesy of Parque Nacional Galapagos.

Observations by PNG officials and visitors indicated that lava flows came from a radial fissure on the NNE flank, and produced gas plumes with low ash content that rose 2-3 km and drifted more than 250 km WNW (figures 34 and 35). The Washington VAAC detected an ash and gas plume in visible satellite imagery drifting W from the summit at 2.4 km altitude late in the day on 16 June, along with a significant thermal signature in infrared imagery. A second gas-and-ash plume at the same altitude drifted WNW the following day for a few hours before dissipating. After two days of intense eruptive activity, seismic tremor activity had declined significantly to background levels by noon on 18 June.

Figure (see Caption) Figure 34. Incandescent lava flows from the eruption of Fernandina produced large plumes of water vapor as they reached the sea during the evening of 16 June 2018. Courtesy of Parque Nacional Galapagos.
Figure (see Caption) Figure 35. Incandescent lava reached the sea during 16-18 June 2018 at Fernandina from a brief eruptive episode. The lava flowed down the N flank. Courtesy of CNH Tours, posted 20 June 2018.

‏A strong pulse of SO2 emissions that drifted W was recorded by satellite instruments on 17 and 18 June 2018 (figure 36). The MODVOLC thermal alert system also recorded a surge of over 100 thermal anomalies from infrared satellite imagery that lasted from 17 to 22 June. More than half of the anomalies appeared on 17 June. The alert pixels were all clustered on the N flank. The MIROVA system also record the spike in thermal activity on 17 June and indicated that the heat source was more than 5 km from the summit (figure 37).

Figure (see Caption) Figure 36. A strong pulse of SO2 issued from Fernandina on 17 June 2018 and was recorded by the OMPS instrument on the SUOMI NPP satellite. The plume drifted W and measured at about 27 Dobson Units (DU). Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 37. The MIROVA system log radiative power measurement for Fernandina showed a spike of thermal activity on 16-17 June 2018 that coincided with the fissure eruption that sent lava flows down the N flank of the volcano into the sea. The black bars indicate a heat source more than 5 km from the summit. The MODVOLC thermal alert system detected over 100 thermal alerts at Fernandina between 17 and 22 June 2018, concurring with observations of lava flows on the N flank of the volcano. Courtesy of MIROVA and MODVOLC.

By 21 June 2018 PNG officials reported that lava was no longer reaching the ocean, but steam from cooling flows was visible at the coastline and over the area of the new flows (figure 38).

Figure (see Caption) Figure 38. By 21 June 2018 active lava flows were no longer reaching the ocean at Fernandina, although steam from cooling lava was still visible near the coast and along the N flank. Courtesy of Parque Nacional Galapagos.

Geologic Background. Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Dirección del Parque Nacional Galápagos (DPNG), Av. Charles Darwin y S/N, Isla Santa Cruz, Galápagos, Ecuador (URL: http://www.galapagos.gob.ec/, Twitter: @parquegalapagos); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Cultural and Natural Heritage Tours, Galapagos, (CNH Tours), 14 Kilbarry Crescent, Ottawa, Ontario, K1K 0G8, Canada (URL: https://www.cnhtours.com/, Twitter: @CNHtours).


Fuego (Guatemala) — August 2018 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Pyroclastic flows on 3 June 2018 cause at least 110 fatalities, 197 missing, and extensive damage; ongoing ash explosions, pyroclastic flows, and lahars

Guatemala's Volcán de Fuego was continuously active throughout the first half of 2018; it has been erupting vigorously since 2002 with historical observations of eruptions dating back to 1531. These eruptions have resulted in major ashfalls, pyroclastic flows, lava flows, and damaging lahars. Large explosions with a significant number of fatalities occurred during 3-5 June 2018 and are covered in this report of activity from January-June 2018. Reports are provided by the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH) and the National Office of Disaster Management (CONRED); aviation alerts of ash plumes are issued by the Washington Volcanic Ash Advisory Center (VAAC). Satellite data from NASA, NOAA, and other sources provide valuable information about heat flow and gas emissions. Numerous media outlets provided photographs of the eruptive activity.

Summary of activity, January-June 2018. The first eruptive event of 2018 occurred during 31 January-1 February and lasted for about 20 hours. It included pyroclastic flows, lava flows, incandescent ejecta, ash plumes that rose to 7 km altitude, and ashfall more than 60 km from the volcano. Four lava flows emerged during the event, and the longest traveled 1,500 m down the Seca ravine. Multiple daily explosions that generated ash plumes continued through May 2018. Ash plumes usually rose to 4.2-4.9 km altitude (400-1,200 m above the summit) and drifted up to about 15 km from the volcano in the prevailing wind directions. Ashfall was often reported from communities within 10 km of the summit, most commonly to the W and SW, but also occasionally to the N and NE. Incandescent ejecta rose up to 300 m above the summit during periods of increased activity; block avalanches of the incandescent material descended the major drainages on all flanks, often as far as the vegetated areas several hundred m below the summit.

The first lahar of the year was reported on 9 April; additional lahars occurred several times during May after rainy periods. They were generally 20-30 m wide and 1-2 m deep, carrying debris 1-2 m in diameter. A lava flow was active in the Ceniza ravine for the second half of May, moving up to 1,000 m from the summit during heightened activity on 22 May, and again on 2 June.

The second major eruptive event of 2018, and the largest and deadliest explosive activity in recent history at Fuego, began with a strong explosion on the morning of 3 June 2018. Multiple explosions throughout the day produced an ash plume that was observed in satellite data at 15.2 km altitude, and a strong SO2 plume that drifted N and NE. Numerous large pyroclastic flows generated by the explosions throughout the day descended multiple ravines around the flanks. The most heavily damaged communities were San Miguel Los Lotes and El Rodeo, 10 km SE of the summit at the base of Las Lajas ravine. Most infrastructure in the communities was buried in ash; there were 110 reported fatalities, and at least 197 people reported missing and presumed dead. Additional explosions two days later caused a brief halt in recovery efforts as more pyroclastic flows covered the same area.

Abundant rainfall that began on 6 June 2018 led to over 30 lahars throughout the rest of the month, inundating all of the major ravines and tributaries of the Rio Pantaleón and Rio Gobernador and causing additional infrastructure damage to bridges and roads. The lahars were often 30-40 m wide, 3 m deep, and carried volcanic blocks and debris up to 3 m in diameter. Explosive activity declined to background levels by the middle of June, but daily explosions with ash plumes and incandescent avalanche blocks continued for the remainder of the month, with continued reports of ashfall in communities within 15 km of the summit.

Activity during January-February 2018. During January 2018, plumes of steam rose to 4.3-4.5 km altitude, drifting primarily W, SW, and S. Activity included 3 to 8 explosions per hour that generated ash plumes, which rose to about 4.3-4.8 km altitude (figure 82). Explosions on 19 January increased to 7-13 per hour, and produced ash plumes that drifted more than 15 km W, SW, and S. Incandescent ejecta rose 100-300 m above the crater and traveled up to 400 m from the crater, in some cases reaching vegetated areas. The SW flank was the most affected by ashfall; it was reported in the communities of San Pedro Yepocapa, Escuintla, Sangre de Cristo, Finca Palo Verde, El Porvenir, Santa Sofía, Morelia, Paniché I and II, Rochela, and Ceilán. Block avalanches traveled down the Seca, Taniluyá, Cenizas and Las Lajas ravines. On 28 January, seismic station FG3 registered an increase in pulses of tremor activity. MODVOLC thermal alerts were issued during 17 days in January. The Washington VAAC issued multiple daily aviation alerts on 22 days of the month.

Figure (see Caption) Figure 82. Moderate explosions produced a plume of ash at Fuego on 14 January 2018 that drifted W a few hundred meters above the summit, seen in this view from SW of the volcano. Courtesy of INSIVUMEH (Informe mensual de la actividad del Volcan de Fuego, Enero 2018).

The first major eruptive event of 2018 occurred during 31 January-1 February and lasted for about 20 hours. It included pyroclastic flows, lava flows, incandescent ejecta, ash plumes that rose to 7 km altitude, and ashfall more than 60 km W, SW, and NE from the volcano (figure 83). Explosive activity increased to 5-8 events per hour, incandescent material rose up to 300 m above the crater, and ejecta traveled 300 m.

Figure (see Caption) Figure 83. The first major eruptive event of 2018 at Fuego produced ash plumes, pyroclastic flows, lava flows and incandescent ejecta on 1 February. Photo taken from the N (adjacent Acatenango in the foreground) by Ruben Merida, courtesy of INSIVUMEH (Informe Mensual de la Actividad del Volcan de Fuego, Febrero 2018).

The substantial ash plume produced from the event drifted tens of kilometers to the W and SW (figures 84 and 85). The SW flank was the area most affected by ashfall, where communities of San Pedro Yepocapa and Escuintla, Sangre de Cristo, Palo Verde, El Porvenir, Santa Sofia, Morelia, Paniché I and II are located. Ashfall also occurred 10-25 km NE in La Rochela, San Andrés Osuna, La Reina, Ciudad Vieja, Antigua Guatemala, and in the WSW part of Guatemala City.

Figure (see Caption) Figure 84. A dense ash plume drifts W and SW from Fuego on 1 February 2018. Image taken by the Operational Land Imager (OLI) on Landsat 8. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 85. A closeup of Fuego (see box in figure 84) on 1 February 2018 shows an ash plume drifting W and fresh ash and pyroclastic flow deposits around the summit during the first major eruptive event of 2019. Image taken by the Operational Land Imager (OLI) on Landsat 8. Courtesy of NASA Earth Observatory.

Four lava flows emerged during the eruptive event; a 1,500-m-long flow traveled down the Seca ravine, a 700-m-long flow traveled down the Ceniza ravine, and flows in Las Lajas and La Honda canyons traveled 800 m from the summit. Numerous pyroclastic flows also descended the Honda and Seca ravines, and smaller pyroclastic flows descended the Trinidad and Las Lajas ravines (figure 86).

Figure (see Caption) Figure 86. Pyroclastic flows descended short distances down several ravines (barrancas) at Fuego on 1 February 2018. Courtesy of INSIVUMEH (Informe Mensual de la Actividad del Volcan de Fuego, Febrero 2018).

La Honda ravine had not been affected by pyroclastic flows since 1974; they traveled 5.8 km down that ravine (figure 87), and 4.2 km down the Seca ravine. About 2,880 residents of Escuintla (20 km SE) and Alotenango (8 km E) were evacuated during these events. Significant concentrations of SO2 were detected on 1 February by the Ozone Mapper Profiler Suite (OMPS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite (figure 88).

Figure (see Caption) Figure 87. Pyroclastic flow deposits covered several kilometers of barranca La Honda on 6 February 2018 from the events which occurred on 1 February. Courtesy of INSIVUMEH (Informe Mensual de la Actividad del Volcan de Fuego, Febrero 2018).
Figure (see Caption) Figure 88. Significant concentrations of SO2 drifted SW on 1 February from the eruptive event at Fuego; they were recorded by the Ozone Mapper Profiler Suite (OMPS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite. Courtesy of NASA Earth Observatory and NASA Goddard Space Flight Center.

Multiple daily explosions with ash plumes continued throughout the rest of February; plumes generally rose to 4.5-4.7 km altitude, and ashfall was reported in communities 10-20 km from the volcano in various directions. Block avalanches descended barrancas Seca, Taniluyá, and Ceniza on most days. Incandescence at night was visible up to 200 m above the crater. MODVOLC thermal alerts were issued on 8 days of the month, and the Washington VAAC issued multiple daily aviation alerts throughout the month.

Activity during March-May 2018. Constant activity continued during March and April 2018, without any major eruptive episodes. Continuous degassing, explosions with ash plumes (figure 89), incandescent ejecta, and daily block avalanches were reported. Steam plumes rose daily to 4.2-4.4 km altitude and usually drifted NW, W, SW, or S. Explosions averaged 4-9 per hour and produced ash plumes that rose to 4.3-4.8 km altitude drifting more than 20 km NW, W, SW, and S. Incandescent ejecta was measured up to 300 m above the crater and traveled a similar distance down the flanks. Block avalanches sent debris up to a kilometer down the major drainages most days. The MODVOLC system recorded thermal alerts during 20 days of March and 22 days of April. The communities most affected by near-daily ashfall, on the SW flank, included San Pedro Yepocapa and Escuintla, Sangre de Cristo, Palo Verde Estate, El Porvenir, Santa Sofia, Morelia, and Paniché I and II. The Washington VAAC issued multiple daily aviation alerts nearly every day during both months.

Figure (see Caption) Figure 89. The ash plume on 13 April 2018 at Fuego was typical of the activity during March and April. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán de Fuego (1402-09), Semana del 07 al 13 de abril de 2,018).

On 9 April the first lahar of the year descended the Seca canyon and the El Mineral channel, tributaries of the Pantaleón River. It was 10 m wide and 1.5 m deep, carrying abundant debris. In special bulletins released on 14 and 16 April INSIVUMEH noted increased explosive activity occurring at a rate of up to 10 explosions per hour, with ash plumes that rose to 4.8 km altitude. This was followed by a report of a lava flow during the evening of 16 April that traveled 1,300 m down the Seca Ravine.

Activity during the first two weeks of May 2018 was similar in character to the previous two months. Steam plumes rose to 4.1-4.3 km altitude, ash plumes rose to 4.5-4.8 km altitude from explosions that occurred at a rate of 4-8 per hour and drifted SW and W, and ashfall was reported in San Pedro Yepocapa, Morelia, El Por-venir, Sangre de Cristo, Santa Sofía, Finca Palo Verde, Panimaché I y II and other nearby communities. Incandescent ejecta rose 150-300 m high and was thrown 50 m from the crater; shockwaves from the explosions were felt 20-25 km away.

A lahar 12 m wide and 1.5 m deep descended the Seca Ravine on 10 May, dragging tree trunks and volcanic blocks as large as 1.5 m in diameter. A 500-m-long lava flow was reported in the barranca Ceniza on the afternoon of 15 May. Explosions occurred at a rate of 5-7 per hour on 16 May, and ash plumes rose as high as 7.8 km altitude and drifted 20 km W and SW, causing ashfall in Panimaché and Morelia. A moderate-sized lahar traveled down the El Jute ravine on 16 May after rains the previous night. During the afternoons of 16, 17, and 18 May lahars flowed down the Seca ravine from the recent abundant rainfall; they were 20 m wide, 1-2 m deep, and carried tree trunks and blocks 1-2 m in diameter. They grew to 25-30 m wide as they reached the confluence with the Rio Pantaleón, and the odor of sulfur was reported.

A lava flow in the barranca Ceniza was active for a distance of 900 m on 17 May, 600 m on 18 May, and 150 m on 19 May. Occasional sounds were audible more than 30 km from Fuego on 20 May from the 6-8 explosions that occurred every hour. Incandescent pulses rose 250 m above the crater during the night. The lava flow was active again to 700-800 m down the Ceniza ravine on 21 May. Overall activity increased to 10-15 weak to moderate explosions per hour on 22 May. The ash plumes rose to 4.3-4.7 km altitude and drifted 15 km S. Incandescent ejecta rose 300 m above the crater and lava flowed 1,000 m down the Ceniza ravine. On 23 May pulses of incandescent material rose 200-350 m above the crater and generated block avalanches that traveled down the Seca, Ceniza, and Las Lajas ravines as far as the vegetated areas. The lava flow in the Ceniza ravine was active up to 800 m from the summit that day. Explosions had decreased to 5-7 per hour by 24 May; the lava flow was still active 800 m down the Ceniza on 25 May.

The Fuego Observatory reported lahars on 25 May in the Seca and Mineral ravines that were 35 m wide and 1.5 m deep carrying abundant volcanic material. They blocked access between the communities of Yepocapa and Morelia, Santa Sofia, and others on the SW flank. Weak explosions and incandescence continued during the last week of the month, with low-level ash plumes drifting generally S, although poor visibility obscured most observations. Ash advisory reports from the Washington VAAC were more intermittent during May than the previous few months, with reports issued on 13 days of the month. The MODVOLC system reported thermal alerts on 16 days during May. The MIROVA project Log Radiative Power plot for the first six months of 2018 showed constant levels of activity similar to that during 2017 (see figure 73, BGVN 43:02) through the beginning of June, with a spike during the eruptive episode of 31 January-1 February (figure 90). The thermal signal ceased abruptly after the explosive events of early June.

Figure (see Caption) Figure 90. The MIROVA project Log Radiative Power plot for Fuego for the first six months of 2018 showed constant levels of activity similar to that during 2017 (see figure 73, BGVN 43:02) through the beginning of June, with a spike during the eruptive episode of 31 January-1 February. Thermal activity ceased abruptly after the explosive events of early June. Courtesy of MIROVA.

Fuego was characterized by ongoing moderate activity during the first two days of June. Steam plumes rose to 4.5 km altitude and drifted S, and 5-8 moderate explosions per hour produced ash plumes that rose to 4.6-4.8 km altitude and drifted 8-20 km S and SE. Moderate to strong shock waves from the explosions caused roofs to vibrate 15-20 km away on the S flank. Pulses of incandescent ejecta rose 100-200 m above the crater and created block avalanches that descended the Seca, Ceniza and Las Lajas ravines as far as the vegetated areas; fine-grained ash fell in Panamiche I. On 2 June lahars descended the Seca, Rio Mineral, Cenizas, Trinidad and Jute ravines, and a lava flow was reported moving 1,000 m down the Ceniza ravine.

Eruptive events of 3-5 June 2018. The second major eruptive event of 2018, and the deadliest in the recent history of Fuego, began with a strong explosion in the early morning of 3 June 2018. The ash plume rose rapidly to 6 km altitude and initially drifted W and SW. It generated large pyroclastic flows that traveled down the Seca, Santa Teresa, and Ceniza ravines and into the communities of Sangre de Cristo and San Pedro Yepocapa on the W flank. Strong explosions continued throughout the day and generated additional large pyroclastic flows in the Seca, Cenizas, Mineral, Taniluyá, Las Lajas, and Honda ravines with devastating consequences to numerous communities around the volcano (figures 91-94).

Figure (see Caption) Figure 91. Large pyroclastic flows descended multiple flanks of Fuego on 3 June 2018 causing significant fatalities and extensive property damage in adjacent communities. View is from Alotenango, 8 km E of the summit. Photo Credit: Orlando Estrada/AFP/Getty, courtesy of The Express.
Figure (see Caption) Figure 92. A large pyroclastic flow on 3 June 2018 descended the Las Lajas ravine adjacent to La Reunión Golf Course, 7 km SE of the summit of Fuego. Courtesy of Matthew Watson, volcanologist.
Figure (see Caption) Figure 93. The pyroclastic flows at Fuego on 3 June 2018 descended multiple ravines and damaged or destroyed a number of roadways and bridges. Photo Credit: AFP/Getty, courtesy of The Express.
Figure (see Caption) Figure 94. After the pyroclastic flows at Fuego descended on 3 June 2018, the Las Lajas ravine adjacent to La Reunión Golf Course 7 km SE of the summit was filled with steaming ash and debris. Courtesy of GeoGis.

The Washington VAAC reported explosions later in the day that generated an ash plume that drifted NE at 9.1 km altitude and E at 15.2 km altitude. The Suomi NPP satellite captured an image of the ash plume rising above the cloud cover at 1300 local time (figure 95). Ashfall of tephra and lapilli was reported more than 25 km away in the village of La Soledad; in addition, the municipalities of Quisache (8 km NW), Acatenango (12 km NW), San Miguel Dueñas (10 km NE), Alotenango (8 km ENE), Antigua Guatemala (18 km NE), Chimaltenango (22 km N), and other areas NW and N of the volcano were impacted with ashfall. La Aurora airport in Guatemala City was closed for two days. In addition to the ash plume, a large plume of SO2 was recorded drifting N and E from the volcano at an altitude of 8 km shortly after the explosions were reported (figure 96).

Figure (see Caption) Figure 95. The ash plume from a large explosion at Fuego on 3 June 2018 rose above the cloud cover to over 15 km altitude and was imaged by the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP at 1300 local time. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 96. A substantial plume of sulfur dioxide (SO2) was detected by the Ozone Mapping Profiler Suite (OMPS) on Suomi NPP satellite after the large eruption at Fuego on 3 June 2018. The image shows concentrations of sulfur dioxide in the middle troposphere at an altitude of 8 kilometers as detected by OMPS. Michigan Tech volcanologist Simon Carn noted that this appeared to be the "highest sulfur dioxide loading measured in a Fuego eruption in the satellite era." Courtesy of NASA Earth Observatory and Goddard Earth Sciences Data and Information Services Center (GES DISC).

The pyroclastic flows down the SE flank were especially devastating to the communities in their path, covering roofs and vehicles with ash and debris (figure 97-100) and killing scores of people. The communities of San Miguel Los Lotes about 9 km SE of the summit and El Rodeo (10 km SE), both in Escuintla Province, were severely damaged from the pyroclastic flows, with most of the fatalities and missing people reported from those communities.

Figure (see Caption) Figure 97. The pyroclastic flows that traveled down the SE flank of Fuego on 3 June 2018 were especially devastating to the communities in their path. This image taken two days later on 5 June shows how the low-lying areas around the ravine are buried in ash from the fast-moving pyroclastic flow, but the higher areas (like the golf course on the right) are relatively free of ash and debris (see figure 94). Courtesy of BBC and Getty Images.
Figure (see Caption) Figure 98. The pyroclastic flows from the eruption at Fuego on 3 June 2018 buried buildings up to 2 m deep in ash and debris in the community of San Miguel Los Lotes, Escuintla Province. Photo by Luis Echeverria/Reuters, courtesy of the Telegraph.
Figure (see Caption) Figure 99. Numerous vehicles were swept away in the pyroclastic flows that descended through the village of San Miguel Los Lotes, Escuintla on 3 June 2018 during the eruption at Fuego. This photo was taken on 5 June as rescue workers continued to search the town. Courtesy of Reuters and the Express.
Figure (see Caption) Figure 100. The pyroclastic flows that traveled through El Rodeo on 3 June 2018 from the large eruption at Fuego contained both fine-grained ash and large angular boulders of volcanic rocks. Rescue workers were forced to evacuate the town on 5 June as additional pyroclastic flows threatened the already devastated community. Courtesy of the Associated Press (AP Photo/Rodrigo Abd).
Figure (see Caption) Figure 101. Most of the village of El Rodeo, 10 km SE of the summit of Fuego, was buried by ash and debris from a pyroclastic flow on 3 June 2018. Rescue workers searched the village while heavy equipment repaired roadways on 5 June. Photo by Rodrigo Abd, courtesy of the Associated Press.

Explosions continued until early evening on 3 June, when pyroclastic flow activity finally diminished. The debris from the pyroclastic flows resulted in lahars descending the Pantaleón, Mineral, and other drainages, leading to the evacuations of the communities of Sangre de Cristo, Finca Palo Verde, Panimache and others that evening. Explosive activity returned to lower levels the following day with dense ash plumes rising to 4.5-4.6 km altitude from 5-7 weak explosions that occurred every hour. Abundant fine ash rose from the ravines filled with pyroclastic flow material from the previous day and drifted SW, W, NW, and N, affecting communities up to 25 km away in those directions. The Washington VAAC reported remnants of the ash plume drifting 300 km ENE on 4 June.

By 4 June, CONRED had increased the Alert Level to red for the communities of Escuintla (22 km SE), Alotenango (8 km E), Sacatepéquez, Yepocapa (8 km NW), Santa Lucía Cotzumalguapa (22 km SW), and Chimaltenango, and opened 13 evacuation shelters in the area. CONRED initially reported on 5 June that 3,271 people were evacuated, 46 were injured and there were 70 known fatalities as a result of the pyroclastic flows and lahars on 3 June. A state of emergency was declared in all three of the provinces (Departments) of Escuintla, Sacatepéquez and Chimaltenango surrounding the volcano.

The number of block avalanches increased on 5 June as a result of 8-10 moderate explosions per hour; ash plumes and pyroclastic flow debris created persistent ash in the air around the volcano. The avalanches traveled 800-1,000 m down Las Lajas and Santa Teresa ravines. On 5 June, a pyroclastic flow descended the El Jute and Las Lajas ravines at 1410 local time. INSIVUMEH reported an increase in explosive activity a few hours later; dense ash plumes rose to 6 km altitude and drifted E and NE. Another pyroclastic flow descended the Las Lajas around 1928 local time that evening. These new pyroclastic flows led CONRAD to evacuate the additional communities of La Reyna, El Rodeo, Cañaveral I and IV, Hunnapu, Magnolia, and Sarita located on the Palín-Escuintla highway, and the highway itself was also closed (figure 102).

Figure (see Caption) Figure 102. Pyroclastic flows descended the flanks of Fuego on 5 June 2018, causing additional damage after the major eruption two days earlier. The view is from the community of El Rodeo, 10 km SE, heavily damaged at the beginning of the eruption. Photo Credits: Rodrigo Abd/AP/REX/Shutterstock, courtesy of the Associated Press.

Activity during 6-30 June 2018. Weak to moderate explosions continued at Fuego on 6 June with ash plumes rising to 4.7 km altitude and drifting W and SW. Significant rainfall in the area that afternoon around 1610 resulted in lahars descending the Seca and Mineral ravines, tributaries of the Rio Pantaleón. One lahar was 30-40 m wide and 4-5 m deep emanating warm sulfurous gases; it carried fine-grained material similar to cement, rocks and debris 2-3 m in diameter, and tree trunks. The communities around the mouths of the ravines and near the Pantaleón Bridge were most affected. New lahars about an hour later descended the Santa Teresa, Mineral and Taniluyá ravines, also tributaries of the Pantaleón River. These lahars were about 30 m wide, 2-3 m deep, and carried similar cement-like fine grained material down the Pantaleón along with blocks 2-3 m in diameter and tree trunks.

Seismic station FG3 recorded a pyroclastic flow descending Las Lajas and El Jute ravines at 2140 local time on 7 June. INSIVUMEH estimated that it produced an ash cloud that rose to 6 km altitude and drifted W and SW. INSIVUMEH issued five special bulletins on 8 June reporting numerous lahars and pyroclastic flows. Lahars descended Santa Teresa, Mineral, and Taniluyá ravines into the Pantaleón around 0240 local time; they were 30 m wide, 2-3 m deep, and carried 2-3-m-diameter blocks and tree trunks. Another surge of lahars registered on the seismogram about two hours later in the same ravines and also in the Ceniza, additionally affecting the Achiguate River. A pyroclastic flow descended Las Lajas ravine at 0820 in the morning, producing another 6-km-high ash cloud. Two more similar pyroclastic flows in the same area were recorded at the seismic station at 1945 and 2040 local time that evening.

During the afternoon of 9 June, lahars descended the Seca, Mineral, Niagara and Taniluyá, generating the largest lahar to date for the year in the Pantaleón River. It was 40 m wide and 5 m deep carrying abundant blocks up to 3 m in diameter and other debris down the W flank. Later that evening explosive activity continued at a rate of 4-7 per hour, dispersing ash plumes up to 15 km W and SW from the summit at an altitude of 4.2-4.4 km. The explosions were audible up to 10 km in all directions. The same ravines and also the Ceniza were affected by new lahars 35 m wide and 3 m deep the following afternoon as a result of the constant rains in the area. Rains continued on 11 June and resulted in strong lahars descending the Seca and Mineral ravines around 1415 local time with diameters of 35-40 m and depths of 3 m. Another strong lahar descended Las Lajas and el Jute ravines in the evening at 1750 local time; these had widths ranging from 35-55 m and depths up to 5 m.

INSIVUMEH reported an increase in explosive activity beginning in the morning of 12 June 2018, producing ash plumes that rose up to 5 km altitude and drifted NE and N 15-25 km. This activity also produced a pyroclastic flow down the Seca ravine around 0730 local time with an ash cloud that rose about 6 km and drifted N and NE. That afternoon a strong lahar descended the Las Lajas ravine, carrying blocks 3 m in diameter in a hot, thick flow that was 35-45 m wide and up to 5 m deep. Since there were no longer distinct channels in the ravine, the material spread out in a wide fan flowing towards the area around El Rodeo. Additional smaller lahars descended the Ceniza and Mineral ravines later that afternoon. By 12 June 2018 CONRED reported that 110 fatalities had been confirmed, 197 additional people were missing, and over 12,500 people had been evacuated since the 3 June explosions began.

On 13 June, a small pyroclastic flow descended the Ceniza ravine around 0630. It was the last pyroclastic flow reported during June. Beginning with the first post-eruption lahars on 6 June, multiple lahars occurred every day during 8-18, 20-23, 26, and 30 June (table 18). The barrancas of Seca, Mineral, Santa Teresa, Taniluyá, Niagra, Ceniza, Las Lajas, El Jute, Rio El Gobernador, and Rio Pantaleón were all impacted by the lahars; they ranged in size from smaller flows that were 20 m wide and 2 m deep carrying blocks 1-3 m in diameter to the largest which were over 40 m wide, up to 5 m deep and carried blocks as large as 3 m in diameter. The flows were warm or hot, carrying tree trunks and other debris, and had strong sulfurous odors. Communities adjacent to the ravines could feel the vibrations of the flows as they passed. As many of the ravines were full of ash and rocks from the pyroclastic flows, new channels were formed and the flows spread out in fans as they descended, further threatening the communities around the flanks of the volcano.

Table 18. Lahars at Fuego were reported 33 separate times between 6 and 30 June 2018; many reports included multiple simultaneous lahars in drainages around all the flanks. Data courtesy of INSIVUMEH.

Date Local time Ravine(s) Width (m) Depth (m) Block Size (m)
06 Jun 2018 1610 Seca, Mineral 30-40 4-5 2-3
06 Jun 2018 1720 Santa Teresa, Mineral and Taniluyá 30 2-3 2-3
08 Jun 2018 0240 Santa Teresa, Mineral, and Taniluyá 30 2-3 2-3
08 Jun 2018 0450 Santa Teresa, Mineral, and Taniluyá, Ceniza -- -- 2-3
09 Jun 2018 1400 Seca, Mineral, Niagara and Taniluyá 40 5 3
10 Jun 2018 1515 Seca, Mineral, Niagara and Taniluyá, Ceniza 35 3 1
11 Jun 2018 1415 Seca and Mineral 35-40 3 3
11 Jun 2018 1750 Las Lajas and el Jute 35-55 3-5 3
12 Jun 2018 1330 Las Lajas 35-45 5 3
12 Jun 2018 1425 Ceniza, Mineral 20 2 1-3
13 Jun 2018 0110 Ceniza 25 2 1-3
13 Jun 2018 1350 Las Lajas 30-40 3 3
14 Jun 2018 0145 Santa Teresa and Mineral 20-25 2 3
14 Jun 2018 1445 Taniluyá, Ceniza, rio El Gobernador, Las Lajas 30-45 3 3
15 Jun 2018 1715 Seca, Mineral 30-35 3 3
15 Jun 2018 1725 Las Lajas 30-35 2 3
15 Jun 2018 1740 Taniluyá, Ceniza 20-25 2 3
16 Jun 2018 1445 Las Lajas 30-35 2 3
17 Jun 2018 1415 Las Lajas -- -- 3
17 Jun 2018 1440 Seca, Mineral 40 2 2
18 Jun 2018 1510 Seca, Mineral 25-30 3 3
18 Jun 2018 1600 Las Lajas 40-45 2 3
20 Jun 2018 0735 Las Lajas 35-45 2-3 3
20 Jun 2018 1230 Las Lajas 30-35 3 3
20 Jun 2018 1415 Seca, Mineral, Taniluyá, Ceniza 30-35 3 3
21 Jun 2018 1940 Las Lajas 30-35 3 3
22 Jun 2018 0030 Las Lajas -- -- 3
22 Jun 2018 1450 Las Lajas -- -- 2-3
22 Jun 2018 1535 Rio Pantaleón 40 3 3
23 Jun 2018 1740 El Jute, Las Lajas, San Miguel los Lotes area -- -- 3
26 Jun 2018 1412 El Jute, Las Lajas, San Miguel los Lotes area -- -- 3
26 Jun 2018 1455 Seca, Mineral, Niagra, Ceniza -- -- 2-3
30 Jun 2018 1435 Seca, Mineral -- -- 2-3

Explosions continued daily through the end of June 2018 at rates ranging from 4 to 9 explosions per hour, creating block avalanches that descended all the major ravines. Ash plumes rose to 4.2-4.9 km altitude (500-1,000 m above the summit) and drifted in multiple directions. On 18 and 22 June, fine-grained ashfall was reported in Panimache, Morelia, Sangre de Cristo, and Palo Verde. By 24 June, satellite imagery revealed that elevated heat was still discernable in several ravines that had been filled with pyroclastic flow debris earlier in the month (figure 103). Explosions on 27 and 28 June sent ash plumes W and ashfall was reported in Sangre de Cristo, Yepocapa, and communities a few km W of Fuego.

Figure (see Caption) Figure 103. Elevated thermal signals in drainages filled with pyroclastic flows were still apparent in satellite imagery at Fuego on 24 June 2018, three weeks after a major explosive event. Courtesy of NASA Earth Observatory.

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Associated Press (URL: https://apnews.com/); AFP/Getty, Agence France-Presse (URL: http://www.afp.com/); BBC News (URL: https://www.bbc.com/); The Telegraph (URL: https://www.telegraph.co.uk/); Reuters (http://www.reuters.com/); The Express (URL: https://www.express.co.uk); Matthew Watson, School of Earth Sciences at the University of Bristol, Twitter: @Matthew__Watson), (URL: https://twitter.com/Matthew__Watson); GeoGis, Twitter: @jlescriba, (URL: https://twitter.com/jlescriba).

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Bulletin of the Global Volcanism Network - Volume 38, Number 01 (January 2013)

Managing Editor: Richard Wunderman

Akita-Komagatake (Japan)

Short lived plume rising to 50 m observed on 14 December 2011

Dona Juana (Colombia)

Seismic swarm in 2010 and monitoring efforts

Heard (Australia)

Satellite imagery reveals lava flows in December 2012

Huila, Nevado del (Colombia)

Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Izu-Oshima (Japan)

Non-eruptive May 2010 surface deformation from inferred deep instrusion

Kikai (Japan)

Steam plumes rose to 800 m duing latter half of 2012

Kuchinoerabujima (Japan)

Increased seismicity, 11 December 2011-5 January 2012

San Cristobal (Nicaragua)

Ash eruption during 25-28 December 2012



Akita-Komagatake (Japan) — January 2013 Citation iconCite this Report

Akita-Komagatake

Japan

39.761°N, 140.799°E; summit elev. 1637 m

All times are local (unless otherwise noted)


Short lived plume rising to 50 m observed on 14 December 2011

The Japanese Meterological Agency (JMA) reported that a short-lived plume rose to 50 m above Akita-Komaga-take on 14 December 2011 and was recorded by a camera located to the N of Me-dake's summit.

Aerial observations were conducted in cooperation with the Japan Ground Self Defense Force on 13 December. Areas of snow melt corresponded to geothermal areas that had been previously identified. No new geothermal areas were found.

An M 2.6 earthquake on 27 December at 1234 local time occurred ~2 km W of Me-dake, with a maximum JMA Seismic Intensity of 1 in Senboku-city, Akita Prefecture. The JMA Seismic Intensity scale, used in Japan and Taiwan is classified into 10 categories; 0 to 4, 5 weak, 5 strong, 6 weak, 6 strong, and 7. The seismicity around the area had temporarily increased, but then returned to baseline levels. No volcanic activity related to this seismicity was observed.

JMA reported no activity at Akita-Komaga-take in 2012.

Geologic Background. Two calderas partially filled by basaltic cones cut the summit of Akita-Komagatake volcano. The larger southern caldera is 1.5 x 3 km wide and has a shallow sloping floor that is drained through a narrow gap cutting the SW caldera rim. On its northern side the southern caldera borders a smaller more circular 1.2-km-wide caldera, whose rim is breached widely to the NE. The two calderas were formed following explosive eruptions at the end of the Pleistocene, between about 13,500 and 11,600 years ago. Two cones, Medake and Kodake, occupy the NE corner of the southern caldera, whose long axis trends NE-SW. The 1637-m-high Komagatake (also known as Onamedake) cone within the northern caldera is highest point, and has produced lava flows to the north and east; it has a 100-m-wide summit crater. Small-scale historical eruptions have occurred from cones and fissure vents inside the southern caldera. The temperatures of geothermal areas increased beginning in 2005, and some fumarolic plumes were observed in 2011-12.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/en).


Dona Juana (Colombia) — January 2013 Citation iconCite this Report

Dona Juana

Colombia

1.5°N, 76.936°W; summit elev. 4137 m

All times are local (unless otherwise noted)


Seismic swarm in 2010 and monitoring efforts

Doña Juana, a volcano in repose, is located ~50 km NE of Pasto, the provincial capital where the local Instituto Colombiano de Geología y Minería (INGEOMINAS) volcanic and seismic observatory is based (figure 1). In this report we discuss monitoring efforts that began as early as 2004, highlight elevated seismicity detected in mid-2010, and describe the relatively new national park which encompasses Doña Juana and two other volcanic centers (Petacas and Ánimas). Petacas is ~19 km NE of Doña Juana and Ánimas, 12.5 km NE. Ánimas lacks a clear Holocene age; however, Ánimas is an important landmark in this report because the recent seismicity is often found proximal to this volcano. Listed as a Quaternary volcanic center, Ánimas can be found in the "Preliminary List of Pleistocene Volcanoes" section of the Volcanoes of the World 3rd edition (Siebert and others, 2010).

Figure (see Caption) Figure 1. This map of instrumentation from 2012 shows the monitoring network for Doña Juana with telemetered locations for the observatory in Pasto (red circle). Triangles are short period seismic stations (red triangles correspond to INGEOMINAS stations and the pink triangle is part of the National Seismic Network of Colombia (RSNC)), the orange hexagon is a broadband seismic station, green circles are electronic tiltmeters, and green squares are repeater stations for telemetry. The volcanic centers of Doña Juana and Galeras are labeled with yellow text. Courtesy of INGEOMINAS.

Aerial observations and field investigations. Aerial observations had been collected since 2004 in collaboration with the Colombian Air Force (FAC). Overflights during clear conditions provided views of the lava domes and exposures of bare rock where high elevation and frequent rockfalls limit vegetation (figure 2). Remote sensing images of the region also captured the variations in vegetation and distribution of scree slopes (figure 3).

Figure (see Caption) Figure 2. This SE looking photo of Doña Juana was taken during aerial surveys on 12 March 2007. The town of La Cruz appears in the foreground, ~13 km W of the volcanic edifice (on the skyline). Courtesy of INGEOMINAS.
Figure (see Caption) Figure 3. This false-color ASTER image of Doña Juana from 9 September 2010 provided a clear view of the sharp boundaries between heavy vegetated outer flanks (red) and the scrub-covered dome complex (green). Within the central dome area a pale region is attributed to scree from rockfalls. The lowlands, where agriculture dominates the topography, can be distinguished by the pale pink to white regions. Courtesy of NASA.

During 13-21 September 2006, INGEOMINAS led field investigations around Doña Juana. Four scientists focused on the area's stratigraphy and composition of volcanic deposits for development of a future hazard map as well as enhancing the knowledge of the volcano's eruptive history.

Monitoring stations. Three seismic stations were online in 2008: Lava, Florida, and Páramo (figure 4). The Páramo tiltmeter was also online in 2008. In 2009 two additional stations were online; La Cruz seismic station was installed in April and La Florida electronic tiltmeter was installed in June. In 2011, geochemical monitoring began at hot springs within 7 km of the edifice.

Figure (see Caption) Figure 4. The telemetered monitoring network for Doña Juana in 2012 included seismic and electronic tiltmeter instruments. Regular monitoring efforts also included measurements at hot springs (see text). Names of the two volcanic centers Doña Juana and Ánimas and the local communities are highlighted in green. The largest nearby community is the town of La Cruz, ~13 km NNW of the volcanic edifice. Volcán Ánimas is the nearest volcanic center to Doña Juana (~12.5 km NE); however, there has been no documented Holocene volcanism from this site. Courtesy of INGEOMINAS.

As of December 2012, the monitoring network consisted of four seismic stations, with radio repeaters linked to the Pasto network, and two electronic tiltmeters.

Hot spring investigations. INGEOMINAS routinely monitored six thermal springs located ~7 km N and SW from the summit (figure 4). There were three visits during 2011 (August, October, and December) and a visit in April 2012. Temperature and pH monitoring as well as geochemical analysis were the main goals for these investigations.

In their online April 2012 technical bulletin, INGEOMINAS noted that bicarbonate (HCO3) concentrations varied at all monitoring sites, and highest values were consistent between the Tajumbina (1,276-1,436 mg/L) and Ánimas II (1,159-1,229 mg/L) sites. Of all sites, Ánimas I showed an increase since August 2011 in both temperature (41.2°C to 55.3°C) and pH (6.5 to 6.83).

In April 2012, INGEOMINAS discovered a new hot spring location, Ánimas III. This site was within 1 km of Ánimas I, and at the time of sampling, had a neutral pH (7.02) and a lower temperature (56.6°C) compared to the neighboring Ánimas I and Ánimas II sites.

Seismicity. INGEOMINAS reported trends in local seismicity during 2009-2012 in technical bulletins available online. Limited seismicity was detected in 2009 and an abrupt change appeared in early 2010 (figure 5). Combined seismicity (volcano-tectonic, tremor, long period, hybrid, and a category noted as "VOL") tallied for 2010 produced an average of 241 events per month. INGEOMINAS assigned earthquakes to the "VOL" category if they did not meet the criteria of other earthquake types but could be distinguished by fracturing signals proximal to the volcanic edifice. Volcano-tectonic (VT) earthquakes occurred more frequently than other types, occurring on average 107 times per month.

Figure (see Caption) Figure 5. Monthly earthquakes detected with the Doña Juana seismic network during 2009-2012. The number of earthquakes represents a sum of volcano-tectonic, tremor, long period, hybrid, and 'VOL' (see text) events per month. Bar color alternates from red to blue to distinguish years. Courtesy of INGEOMINAS.

Seismicity peaked in August 2010 owing to three VT swarms. That month the various earthquakes totaled more than 675 events. These were low-magnitude earthquakes (M 0-2.7) with relatively shallow depths (7-10 km below the summit).

The calculated locations of earthquakes were available for events during 2010-2012 (table 1). During this time period, epicenters were frequently dispersed between Doña Juana and Ánimas except for the mid-2010 activity and during January-February 2011. This record of information highlights the significance of August 2010 when VT earthquakes were clustered ~7 km NE of Doña Juana, slightly closer to the older volcanic edifice Ánimas (figure 6).

Table 1. During June 2010-December 2012, earthquake detection was sufficient for calculating magnitudes and locations. During several months (January-May 2010, June and October 2011, and September and November 2012) no locations were determined. "Notes" refer to epicenter characteristics such as clustering locations; "dispersed" events are those that occurred at various depths and distances from the volcanic centers. Courtesy of INGEOMINAS.

Month Total Located Magnitude Depth (km below summit) Notes
Jun 2010 68 0.1-2.6 5-10 ~5 km SW of Ánimas
Jul 2010 14 0.2-1.5 6-10 ~5 km SW of Ánimas
Aug 2010 130 0-2.7 7-10 ~5 km SW of Ánimas
Sep 2010 34 0.2-2.1 1-11 ~5 km SW of Ánimas
Oct 2010 10 0.6-2.7 ~7 dispersed
Nov 2010 5 1.1-2.3 3-6 dispersed
Dec 2010 7 0.2-1.8 4-10 dispersed
Jan 2011 59 0.1-3.1 3-14; 6-8 ~8 km SW of Ánimas; many earthquakes clustered at 6-8 km depth
Feb 2011 1 1.2 7 2 km SW of Ánimas
Mar 2011 7 0.5-2.1 15-50 between Doña Juana and Ánimas
Apr 2011 2 <0.2 5.7-6.5 between Doña Juana and Ánimas
May 2011 2 0.4, 1.7 8, 11 dispersed
Jun 2011 -- -- -- --
Jul 2011 9 0.3-1.1 6-12 some clustering near Ánimas
Aug 2011 7 <2 4-15 between Doña Juana and Ánimas
Sep 2011 1 0.7 4 between Doña Juana and Ánimas
Oct 2011 -- -- -- --
Nov 2011 9 0.3-1.5 3-8 between Doña Juana and Ánimas
Dec 2011 2 0.9, 1.7 4-6 between Doña Juana and Ánimas
Jan 2012 16 0.3-1.5 1-19 between Doña Juana and Ánimas
Feb 2012 5 0.9-1.7 2-8 between Doña Juana and Ánimas
Mar 2012 2 0.8, 1.3 7 between Doña Juana and Ánimas
Apr 2012 5 0.4-1.3 0-18 dispersed
May 2012 7 0.5-1.4 3-9.5 dispersed
Jun 2012 20 0-2.3 1-14 dispersed
Jul 2012 13 0.7-1.9 1-14 dispersed
Aug 2012 6 0.2-1.9 0-14.5 SW of Doña Juana
Sep 2012 -- -- -- --
Oct 2012 4 0.7-1.3 0-20 SW of Doña Juana
Nov 2012 -- -- -- --
Dec 2012 2 1.1, 0.7 2, 20 ~10 km S of Doña Juana
Figure (see Caption) Figure 6. Volcano-tectonic seismicity during August 2010 was characterized by a swarm located between Doña Juana and Ánimas volcano; ~8 km NE of Doña Juana. Courtesy of INGEOMINAS.

Colombia's 52nd Natural National Park. In 2007, the Doña Juana-Cascabel Volcanic Complex Natural National Park was created both by the Ministry of Environmental, Housing and Territorial Development and the Colombian Natural National Parks (figure 7). This included Doña Juana, Ánimas, and Petacas volcano (located ~19 km NE of Doña Juana) within the 65,858 hectares of preserved land. Within this densely forested region, a series of streams and waterfalls was locally known as El Cascabel. The park was developed to protect diverse flora and fauna, including numerous endangered species such as the Andean condor, the Moor tapir, the spectacled bear, and puma; approximately 11% of the park includes alpine terrain.

Figure (see Caption) Figure 7. This map of biomes includes the Doña Juana-Cascabel Volcanic Complex Natural National Park and surrounding region. Doña Juana is located in the SW portion of the park. Shaded areas indicate low-elevation Amazon through high-elevation Andean environments. The park boundary is indicated by a heavy black line; populated areas are shaded light pink, road systems are represented by gray lines, and major towns are labeled. This map appears in the 2008-2013 Management Plan of PNN CVDJ-C (2008).

References. Department of the Environment, Housing and Territorial Development Special Administration Unit of the system of Natural National Parks (UAESPNN), 2008, Doña Juana-Cascabel Volcanic Complex Natural National Park (PNN CVDJ-C) Management Plan 2008-2013, Popayán, Colombia, July 2008.

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Geologic Background. The forested Doña Juana stratovolcano contains two calderas, breached to the NE and SW. The summit of the andesitic-dacitic volcano is comprised of a series of post-caldera lava domes. The older caldera, open to the NE, formed during the mid-Holocene, accompanied by voluminous pyroclastic flows. The younger caldera contains the active central cone. The only historical activity took place during a long-term eruption from 1897-1906, when growth of a summit lava dome was accompanied by major pyroclastic flows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Pasto, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); WWF Colombia (URL: http://www.wwf.org.co/?109882/Nuevo-Parque-Nacional-Natural-en-el-piedemonte-Andino-Amazonico-colombiano); Doña Juana-Cascabel Volcanic Complex National Natural Park (URL: http://www.parquesnacionales.gov.co/).


Heard (Australia) — January 2013 Citation iconCite this Report

Heard

Australia

53.106°S, 73.513°E; summit elev. 2745 m

All times are local (unless otherwise noted)


Satellite imagery reveals lava flows in December 2012

We received an informal report from Matt Patrick (Hawaiian Volcano Observatory) on a new eruptive episode at Big Ben volcano, Heard Island (figure 16). He noted that MODVOLC thermal alerts reappeared at Heard in September 2012 after a four year hiatus (the last eruptive episode ended on 2 March 2008; BGVN 33:01), suggesting the start of a new eruptive episode at the volcano. Since Heard Island is unsettled and extremely isolated, monitoring of the volcano is possibly primarily through satellite imagery (Patrick, 2013).

Figure (see Caption) Figure 16. A contour map (interval = 200 m) showing the partly ice-covered Heard Island. At the time of map preparation, the brown areas were ice free. Produced and issued in January 2000 by the Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia.

EO-1 Advanced Land Imager images collected through late 2012 and early 2013 confirm that eruptive activity resumed around September 2012, in the form of a low-level effusive style eruption similar to its other recent eruptions (figures 17 and 18). Patrick noted that the vent crater had enlarged significantly over the four years following the end of the last eruptive phase, March 2006-March 2008.

Figure (see Caption) Figure 17. A series of images documenting the summit crater and subsequent lava advances at Mawson Peak, Heard Island from 3 July 2012 to 5 January 2013. The Earth Observing-1 (EO-1) satellite's Advanced Land Imager (ALI) Band 1 (panchromatic) images (10-m-pixel size) acquired several clear images on 3 July, 9 September, 13 October, 15 and 28 December 2012, and 5 January 2013. North is to the top of the photos. In the first three images the 200-m diameter crater at the summit of Mawson Peak is easily visible, and there is no evidence of activity outside of the crater. Courtesy of Matt Patrick.
Figure (see Caption) Figure 18. EO-1 ALI Band 10-3-2 RGB composites (30-m-pixel size) of the same series of images as in figure 17 (3 July 2012 to 5 January 2013). North is to the top of the photos. The red is the shortwave infrared band (Band 10, 2 microns); red pixels indicate high temperatures suggesting hot lava surfaces. As in figure 17, the 3 July 2012 image shows that the summit crater was cold, with no evidence of lava inside. However, the 9 September 2012 image clearly shows that elevated temperatures (and presumably lava) had appeared in the crater, consistent with the appearance of MODVOLC thermal alerts later that month. Therefore, this eruptive episode appears to have started around September. Courtesy of Matt Patrick.

The 15 December 2012 image in figure 17 shows that a short lava flow from the summit was emplaced on the SW flank. The flow was ~420 m long and had two lobes. By 28 December, a flow consisting of two lobes (presumably the same flow as in the 15 December image) had reached 770 m SW of the summit crater. In the 5 January 2013 image this flow was 780 m long and had changed little over the previous week.

Figure 18 shows that the 9 September and 13 October 2012 images suggested active lava contained with the summit crater. The 15 and 28 December 2012 images showed elevated temperatures on the lava flow SW of the summit, suggesting it was active over this interval, which was consistent with the observed elongation of the flow in the visible images. Fewer high-temperature pixels in the 5 January 2013 image and the meager advancement observed in the visible images, suggested that the flow had stalled by this point.

Overall, the activity as of mid-March 2013 had consisted of lava within the crater and a lava flow of at least 770 m long emplaced SW of the crater. This low-level effusive activity is consistent with the previous three eruptive episodes observed in satellite images at Heard Island (Patrick and Smellie, in review). These three episodes, May 2000-November 2001 (BGVN 25:11, 26:02, 26:03, and 28:01), June 2003-July 2004 (BGVN 29:12), and March 2006-March 2008 (BGVN 31:05, 31:11, 32:03, 32:06, 33:01, and 35:09), each lasted 1-2 years. On this basis, Patrick suggested that this new eruptive episode may persist for a similar duration. MODVOLC thermal alerts were measured nearly continuously from 21 September 2012 through 24 February 2013.

References. Patrick, M., 2013, A new eruptive episode at Big Ben Volcano, Heard Island, informal communication to BGVN, 23 February 2013.

Patrick, M.R., and Smellie, J.L., in review, A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-2010, Antarctic Science, in review in 2013.

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon volcano lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben volcano because of its extensive ice cover. The historically active Mawson Peak forms the island's 2745-m high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported in historical time at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Information Contacts: Matt Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia (URL: https://data.aad.gov.au/database/mapcat/heard/heard_island.gif); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Nevado del Huila (Colombia) — January 2013 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Lava dome emplacement occurred at Nevado del Huila's Pico Central (central peak) in late 2008, and was accompanied by seismic unrest and significant sulfur dioxide (SO2) emissions (BGVN 37:10). Extrusion continued between November 2008 and November 2009. Ash plumes were frequently observed by webcameras during late 2008 to December 2009, and satellite imagery reviewed by the Washington Volcanic Ash Advisory Center (VAAC) detected intermittent ash emissions between October 2009 and April 2011. From January 2009 to December 2012, the Instituto Colombiano de Geología y Minería (INGEOMINAS) reported persistent emissions from the lava dome and dramatic changes to the perched glacier as the lava dome expanded across the E and W flanks. Activity generally decreased in November 2010 through 2012.

In this report, we focus on the time period of December 2008-December 2012 and also discuss monitoring efforts overseen by INGEOMINAS with collaborators such as the Colombian Air Force (FAC), the Washington VAAC, and the Sulfur Dioxide Group's Ozone Monitoring Instrument (OMI). The following subsections review webcamera and aerial observations, thermal-camera imaging, satellite images of volcanic plumes, seismicity, SO2 measurements (DOAS, Flyspec, and OMI), acoustic flow monitoring, and new tilt data. The local monitoring network was expanded during this reporting period, adding two infrasound monitoring stations in 2009 and 2012, two webcameras in 2010 and 2012, and instrumentation at the Caloto site that included a broadband seismometer and an electronic tilt station in 2012.

Web-camera observations. From December 2008 to December 2009, the Tafxnú web-camera (located ~15 km S of the volcanic edifice) frequently recorded gas-and-ash plumes rising higher than 2,000 m above the active dome (figure 26). In 2009, plumes (frequently ash-and-gas, but in some cases gas without ash) rose to maximum heights above the dome as follows: 1,000-2,000 m in June; 1,000-2,500 m in November; and 2,000-5,000 m in December.

Figure (see Caption) Figure 26. On 6 and 9 November 2009, summit activity from Nevado del Huila was observed by INGEOMINAS' N-looking Tafxnú web-camera. Accelerated dome growth was noted by INGEOMINAS that month (discussed in text below), and they annotated this image to circle the location of incandescence and summit activity. Note that these images have been altered from the originals; GVP staff increased the brightness and contrast in order to better distinguish the peaks of the Huila complex. (Top images) Incandescence on 6 November was absent at 0331 (left image) but appeared at 0333 within the green circled region (right image). INGEOMINAS suggested this incandescence resulted from dome collapse events exposing hot rock. The darker peak centered in the foreground is Pico Sur, while the active Pico Central is located higher and to the right of that peak in these images. (Bottom images) Plumes of ash and gas drifting NW from Pico Central were observed on 9 November at 0652 (left image) and 0653 (right image). The green circled region in the left-hand image corresponds to the same location circled in the image from 0333 on 6 November. Two water droplets on the camera lens created the local circular distortions. Courtesy of INGEOMINAS.

An additional camera was brought online in July 2010, located in the town of Maravillas (~10 km SE). A third camera, located at the Caloto site (~4 km SSW of the active dome) came online in July 2012 (figures 27 and 28).

Figure (see Caption) Figure 27. This composite image shows, at left, a map view of the three Nevado del Huila webcamera locations and the extent of their viewsheds. Photos at right show camera installation sites. The newest monitoring station (Caloto) was installed on 19 May 2012 on the SW flank. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 28. A map of monitoring stations for Nevado del Huila from June 2012 included locations of webcameras and seismic, geochemical, and geophysical instruments. The summit of Pico Central is located approximately beneath the text BUCB. Note that yellow and black lines represent major and minor roads, respectively, and blue lines represent rivers. Courtesy of INGEOMINAS.

Observations of dome growth and summit activity during 2009-2010. With support from the Colombian Air Force (FAC) during 2009-2012, INGEOMINAS monitored dome growth and geomorphological changes at Huila by conducting aerial observations with helicopters.

During February 2009 and June-December 2009, INGEOMINAS reported numerous episodes of tremor that were likely associated with ash emissions, but cloud cover and nightfall sometimes precluded direct observations. Notable ash plumes were observed on 11 February, 23 July, 3 August, 16-23 October, and 3, 9, 12, 13 and 15 November; ashfall was noted by observers on all days except 11 February. A crack that had formed along the N face of Pico Central in 2007 continued to steam during this time period.

During three overflights conducted in January 2009, INGEOMINAS determined that the Pico Central lava dome had grown since November 2008. With repeat aerial photography, scientists calculated a total dome volume of 52 x 106 m3 with dimensions of 1,000 m N-S and 250 m E-W. The fresh dome rock continuously degassed (figure 29). Tafxnú webcamera images also showed that gas emissions frequently rising above Pico Central were often blue-colored. Due to continued unrest at Nevado del Huila (note that this name is shortened to 'Huila' during the remainder of this report), especially seismicity and active dome growth at Pico Central, INGEOMINAS maintained Orange Alert (Alert Level II; the second highest Alert Level on a 4-color scale from Green/IV-Yellow/III-Orange/II-Red/I) during January-February 2009.

Figure (see Caption) Figure 29. On 28 January 2009, the FAC facilitated observations of Nevado del Huila's growing lava-dome. In this view, the SW flank (centered) emitted a small gas column. This image highlights the zone of active lava dome growth (outlined in yellow) and the perimeter of the crater (outlined in orange). Courtesy of FAC and INGEOMINAS.

On 11 February 2009, a small pulse of tremor was accompanied by an ash plume discharged at Pico Central which was captured by the Taxfnú webcamera during 0745-0751. During that time period, INGEOMINAS noted a small pulse of tremor. On 23 February, an INGEOMINAS passenger on a commercial aircraft saw diffuse gas escaping from both the crater that hosts the dome and from the N-flank crack. During March, the webcamera frequently showed degassing from the crater and the lava dome. Clear conditions enabled observers on commercial flights to observe a white plume rising from Pico Central in the morning of 10 March. INGEOMINAS noted that both seismicity and remote observations of dome growth indicated decreased activity since February. Accordingly, on 31 March 2009, INGEOMINAS reduced the Alert Level to Yellow (II).

Aerial observations in April highlighted the presence of ash covering the S glacier, confirming the ongoing eruption. Elevated temperatures were concentrated at the extreme high and low points of the dome and degassing continued from the higher-elevation portion of the crater (figure 30).

Figure (see Caption) Figure 30. Photos taken on 19 April 2009 showed Nevado del Huila's active dome and the adjacent ash-covered and locally disturbed glacier. (top) In this visible-light view, the active lava dome has extended down the SW flank of Pico Central (yellow line). Cloud cover obscures the upper peaks of Pico Central (left) and Pico Sur (right). The glacier around Pico Central is difficult to distinguish due to ash cover and cracking attributed to dome emplacement. (bottom) This image is a close-up of the lava dome's SW flank with a forward-looking infrared (FLIR) camera which disclosed higher thermal flux from the dome's upper and lower regions. Gas emissions had been more concentrated from the higher region of the dome, however, the bright glow in this image may also be due to the reflective cloud-cover seen in the visible-spectrum image (top). Courtesy of FAC and INGEOMINAS.

During May and June 2009, the dome's surface continued to produce thermal anomalies, and dome growth was inferred based on the observable fragmentation of dome rock and a wider distribution of fresh material. INGEOMINAS noted that the color of the extruded material in the higher region of the dome had changed to a red-brown color (earlier dome rock was distinctively gray).

On 23 July ashfall was reported at the local military base in Santo Domingo and José Jair Cuspian (Caloto). They reported ashfall in the NW sector of the volcanic edifice. INGEOMINAS reported that this ash event coincided with a pulse of tremor registered that day at 0442.

On 3 August there was a pulse of tremor at 0036 and INGEOMINAS received reports of ashfall in the municipalities of Toribío and Santander de Quilichao (~30 km and ~50 km W of the edifice, respectively). Aerial observations on 16 August established that the crater had grown wider.

During September 2009 there were no major changes observed via webcam. On 16 and 23 October, reports of widespread ashfall came from various municipalities of N Cauca, Valle del Cauca, and in the foothills around the volcano (departments of Cauca, Valle, Tolima, and Huila) (figure 31). There were also reports of sulfur odors from the most proximal communities.

Figure (see Caption) Figure 31. An ash plume from Nevado del Huila's newly-formed crater and fumarolic sites was observed from aircraft on 23 October 2009. (top) A dark curtain of ash ("Cortina de cenizas") drifted SE from Pico Central that day; the plume height was ~1,000 m above the crater. The Washington VAAC reported ash in satellite images at 1015 that day, and noted that the ash plume rose to 6 km altitude, was ~46 km long, and drifting SE at 5 m/s. (bottom) A closer view of the W flank highlights gas-and-ash plumes rising from the upper crater (orange outline) while isolated sites released white plumes, including the site on the N flank of Pico Central (at left) where steam from a fissure had been observed consistently since November 2007. The accumulation of newly erupted material was typically observed from the upper region of the dome (circled in blue); the extent of the dome is outlined with yellow. Ashfall had covered the snow and glaciers of Huila; however, cracks in the glacier remained visible as jagged black and white lines, particularly on Pico Sur (right-hand edge of photo). Courtesy of FAC and INGEOMINAS.

At 0541 on 16 October 2009, the webcamera captured images of an ash plume rising in pulses from Pico Central and drifting E. Accordingly, the Alert Level was raised from Yellow (III) to Orange (II), where it stayed until 5 January 2010. An overflight on 23 October provided views of both intense fumarolic activity from the dome and a column of ash that reached up to 1,000 m above the crater. The summit and glaciers were covered by ashfall, lava extrusion was continuing from the upper region of the crater, and there were thermal anomalies where gas emissions were concentrated. An 11-minute-long episode of tremor that began at 0200 on 28 October was thought to signify dome rock extrusion.

Based on observations during overflights on 30 October and 2 November, INGEOMINAS calculated that the dome volume had increased by ~9 x 106 m3 since the previous estimate in January 2009. Aerial observers saw ash emitted in pulses.

Rapid dome growth occurred in November as witnessed during five aerial investigations (2, 4, 6, 10, and 25 November). On 3 November, an explosion was heard and ashfall was reported by the communities of Inzá, Mosoco, Jambaló y Belalcázar, and other communities SW of the volcano. New layers of ash had accumulated around the summits of Huila, often appearing brown-red as opposed to the gray material deposited in previous months (figure 32). A weekly INGEOMINAS report announced that by 10 November 2009, the dome volume had increased by ~16 x 106 m3 since the previous estimate, more than doubling the amount of growth that had occurred during January-October 2009.

Figure (see Caption) Figure 32. Aerial photos from November 2009 documented rapid changes on Nevado del Huila's Pico Central. (top) On 4 November INGEOMINAS observed additional ejecta surrounding the lava dome and elevated ash emissions. In this photo of the S face of Pico Central, steam and ash rise from the crater, and brown-red ash and blocks cover the glacier that surrounds the active dome. Dome rock extends from the center of Pico Central to lower elevations on the W flank. (bottom) This view of Nevado del Huila's SE flank on 25 November 2009 reveals the increased size of the lava dome which towers above Pico Sur, the rugged-looking peak centered in this view. Ash covered snow and glacial ice surrounds the immediate region of the dome while plumes of gas drift westerly. The dark gray, rounded peak to the lower left is Cerro Negro, the location of a seismic station that remained offline during this reporting period. Courtesy of FAC and INGEOMINAS.

Gas emissions were observed by the webcamera at Tafxnú and during four overflights in December 2009; however, fumarolic activity dropped during the first week of December. Aerial observations determined that 2008 dome rock was being covered by 2009 lava that contained fewer large blocks; the 2008 dome material was distinctively more gray and blocky. During an overflight on 29 December, clear weather allowed INGEOMINAS scientists to observe minor dome collapse events, new cracks in the glacier along the lower E dome contact, and additional dome rock extending down the E flank.

In January 2010, dome growth continued and notably expanded the dome E by ~50 m, further displacing portions of the Pico Central glacier. Gray ash continued to be deposited in the area, covering the glacier surfaces. White plumes were observed this month during overflights and from the webcamera. On 5 January, INGEOMINAS reduced the Alert Level from Orange (II) to Yellow (III); this status was maintained until 15 June 2010.

On 22 February 2010, scientists on board an FAC helicopter noted displaced glacial ice, some steaming along the dome edge, and the surface textures of the 2008 and 2009 lava domes persisted (blocky vs. smaller clast sizes, respectively; figure 33). Based on aerial observations, INGEOMINAS calculated a total dome volume of at least 70 x 106 m3.

Figure (see Caption) Figure 33. During an overflight on 22 February 2010, Nevado del Huila's active dome, displaced ice, and gas emissions were visible. Fresh volcanic material clearly began to extend W and E, divided by the long axis of the Huila complex. (Top) An aerial view of Pico Central's S-facing peak where the active dome was shedding material to the W and E. (Middle) Degassing dome rock is visible along the W flank. The blocky gray rock centered in this region was attributed to 2008 lava extrusion. (Bottom) New dome rock is in contact with the fragmented glacial ice on the E flank, and dome steaming is visible along the margin. Courtesy of FAC and INGEOMINAS.

INGEOMINAS reported that on 12 April additional ash had accumulated on the glacier and lava extrusion was continuing. Columns of gas continued to be emitted from the surface of the new dome, at the contact of 2008 and 2009 lava, and from the crack that had formed in 2007 on the N flank of Pico Central.

No overflights were conducted in June, however the Alert Level was raised to Orange (II) due to increased seismicity, primarily hybrid earthquakes and SO2 emissions (see seismic and SO2 discussion below). INGEOMINAS suggested that the marked increase in hybrid earthquakes may have been linked with the ascent of new magmatic material within the volcanic edifice.

In July, degassing continued and intermittent, small ash emissions were observed toward the end of the month by the ground-based cameras Tafxnú and Maravillas. By 16 July, INGEOMINAS reduced the Alert Level to Yellow (III), due to the reduction in seismicity and SO2 flux, where it remained through August. The Washington VAAC reported possible ash plumes drifting from Huila during 28-30 of July but an absence of such plumes during August.

A 19 August flight revealed that snow had accumulated on the dome. INGEOMINAS noted that some episodes of tremor were likely related to the process of lava dome extrusion and these conditions did not show wide variations in August. Minor ash emissions were reported toward the end of the month. The Maravillas camera detected incandescence on 26 and 29 August, possibly from hot rockfalls from the lava dome.

A pulse of tremor on 30 August at 0635 coincided with ash emissions also observed by the Tafxnú camera. In the afternoon that day, people in the town of Toribío (~30 km W) noted an ash plume. There was also a report that the Símbola River changed color due to the presence of ash. The VAAC noted a hotspot at the summit in satellite images on 31 August.

During September, webcameras imaged plumes of gas as well as gray and reddish-colored emissions attributed to volcanic ash. These plumes were not visible in satellite imagery; however, the Washington VAAC released two notices on 9 September in response to reports from INGEOMINAS that ground-based observations included continuous emissions of gases and some ash.

During the first week of September, the Maravillas webcamera and local populations observed incandescence from the active dome; INGEOMINAS attributed the activity to hot rockfalls on the dome. On 9 September, INGEOMINAS raised the Alert Level to Orange (II); seismicity (particularly energetic tremor) and frequent incandescence were considerations for this announcement. On 9 September, both webcameras captured images of ash and incandescence. On 10 September, drumbeat earthquakes (earthquake signatures related to dome extrusion) had appeared in the seismic records. The last time that drumbeat earthquakes had been detected from Huila was in November 2008 (BGVN 37:10). By 21 September, INGEOMINAS announced that 1,799 drumbeat earthquakes had been detected over the past 13 days.

An overflight on 15 September determined that conditions at the dome were continuing to change; extrusion continued from the highest part of the dome (near the contact with the crater wall). They also observed a debris flow containing rocks and ice that had originated from the edge of the dome and had traveled ~1.5 km down the E flank (figure 34). By the end of the month, gas emissions continued and incandescence was observed by the webcameras.

Figure (see Caption) Figure 34. On 15 September 2010 INGEOMINAS observed debris flows along the E flank of Nevado del Huila. (top) Snow had visibly collected on the active dome that continued to degass and displace the glacier. Near the dome, the glacier was notably fragmented and discolored due to overlying debris and ash. (bottom) This view is a closeup of the area below the fragmented glacier on Huila's E flank. The extent of the debris flow is visible as a 1.5 km long trace of gray material that had incorporated blocks of ice and rocks. Courtesy of FAC and INGEOMINAS.

Aerial observations on 29 September, 1 October, and 4 November confirmed ongoing dome growth. On 1 October, the VAAC reported ash drifting from the summit. On 12 October, INGEOMINAS reduced the Alert Level to Yellow (III); they stated that conditions appeared to have stabilized, in particular local seismicity and gas-and-ash emissions. The webcameras continued to capture images of white gas emissions during the second week of October. White plumes and some incandescence were visible in October. Thermal images from 4 November found that the W-central dome's temperature was 250°C. On 11 November the Washington VAAC reported ash drifting from the summit.

Observations during January-December 2011. The webcameras continued to record images of white plumes rising from the Pico Central dome throughout 2011. Aerial observations during the year noted frequent gas emissions and infrequent ash plumes. During an overflight on 25 January, a FLIR camera detected temperatures up to 90°C from various locations on the dome (figure 35). During an overflight on 29 March, observers noted degassing and odors of sulfur.

Figure (see Caption) Figure 35. In these photo pairs taken during an overflight on 25 January 2011, INGEOMINAS measured surface temperatures of Nevado del Huila's lava dome. (top) These photos are centered on the E flank of Huila. The thermal image is zoomed in on the brown-colored lava dome that continued to steam and degass, forming a small plume rising above Pico Central. For the dome, the minimum ("BAJA") and maximum ("ALTA") temperatures were less than 30 and 68.3°C, respectively. (bottom) These photos are viewing the S-facing Pico Central with the lava dome (centered). Gas emissions were rising from the highest region of the dome and the minimum and maximum temperatures were less than 30 and 80.6°C, respectively. Courtesy of FAC and INGEOMINAS.

On 19 April, the Washington VAAC reported that an ash plume was detected in enhanced multispectral imagery at 0315. The plume was drifting NNW from Huila. The announcement included a note that the ash plume did not appear to be the result of an explosive event. Later that day, after sunrise, INGEOMINAS confirmed that low seismicity was detected, a white plume was visible, but ash emissions were absent.

Aerial observations on 26 April included intense degassing from the NW side of the lava dome; the emissions were gray. A thermal camera detected temperatures of the dome in the range of 78-83°C. The glacier also appeared to have further deformed since the last aerial observations in March.

In May, degassing was observed with the webcameras on days where weather conditions permitted clear views. On 6 and 20 June, scientists confirmed that degassing continued during an overflight; they also observed the accumulation of snow on the lava dome as well as on the surrounding glacier. On 20 June, notable rockfalls were visible from the lava dome that contributed to scree along the dome's lower edges.

Degassing continued to appear in clear webcamera views and during overflights in June-July and September-December. Aerial observers on 22 October saw snow avalanches on the Pico Norte glacier and intense steaming from the upper regions of the dome.

Observations during January-December 2012. Throughout 2012, INGEOMINAS recorded observations of the dome based primarily on webcamera images. No major changes were noted in the weekly and monthly online reports; pervasive steaming and white plumes were frequently observed throughout the year by the two webcameras (Tafxnú and Maravillas). INGEOMINAS maintained Yellow Alert (III) during 2012.

One overflight was conducted by INGEOMINAS in 2012. On 14 January 2012, scientists observed the usual degassing and noted that snow had collected on the dome and glacier. That day's clear viewing conditions allowed detailed observations of the lava dome texture and INGEOMINAS attributed the spiny texture of the dome to late-stage extrusion (figure 36).

Figure (see Caption) Figure 36. On 14 January 2012, clear conditions provided aerial views of Nevado del Huila's lava dome texture. (top) This view of the dome's SE face is centered on the part of the lava dome that had started to accumulate snow cover. Steaming was visible from some regions of the dome but a strong plume was not visible during this overflight. (bottom) INGEOMINAS noted that the higher region of the dome had distinguishable spines that may have formed recently. Courtesy of FAC and INGEOMINAS.

Declining seismicity during January-August 2009. During 2009, four seismometers (two broadband and two short-period stations) were maintained by INGEOMINAS. Ash emissions in October 2009 temporarily disabled the short-period Verdún 2 station, located ~5 km N of the active dome. The Cerro Negro short-period station, closest to the active dome, was not operating during this reporting period (2009-2012). In general, three to four seismic stations were operating during 2009-2012.

In 2009, a total of nine earthquakes were large enough for people nearby to feel shaking; these events had magnitudes between 2.8 and 4.8 with focal depths between 6.2 and 12 km. The epicenters were 3-25 km away from the closest seismic station, CENE, which was located ~3 km S of Pico Central. INGEOMINAS highlighted these earthquakes in their monthly technical bulletins.

From January to September 2009, INGEOMINAS reported a decreasing trend in seismicity. In particular, volcano-tectonic (VT) and long period (LP) earthquakes were becoming less frequent on a monthly basis (figure 37). INGEOMINAS described VT earthquakes as resulting from rock-fracturing events, and LP earthquakes from fluid transport processes within the volcanic edifice. Large daily counts of LP earthquakes generally became less frequent over time. Low levels of tremor, hybrid events, and superficial activity (rockfalls and explosions) were detected throughout this time interval.

Figure (see Caption) Figure 37. Nevado del Huila's seismicity, in particular VT, LP, and tremor earthquakes, decreased overall during January-August 2009. In this plot, the number of events were tallied per day and plotted over time. The legend in the upper right-hand corner lists terminology in Spanish that relates to these conventions: VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Explosions were detected mainly in June and July; see previous subsection "Observations of dome growth and summit activity during 2009-2010" for descriptions of explosive activity. Courtesy of INGEOMINAS.

Clustered epicenters in 2009. Beginning in January 2009, INGEOMINAS described a clustering of seismicity notable in distinct regions of the volcanic edifice. These consisted of three regions, the SW sector, the SE sector, and beneath the central edifice (Pico Central). This pattern was particularly clear in June, October, and December. The June 2009 map of seismicity appears in figure 38. The deepest earthquakes (8-12 km) tended to occur S of the edifice while shallow events were distributed throughout the area. Several deep and distal earthquakes occurred each month with depths between 10-20 km and epicenters up to 25 km from the edifice; these events have been attributed to regional faults.

Figure (see Caption) Figure 38. A map with cross-sections plotting epicenters and hypocenters of volcano-tectonic and hybrid earthquakes during June 2009 at Nevado del Huila. Three zones of clustered activity took place beneath the volcanic edifice (dashes lines). Note the yellow bar for scale (10 km) and the yellow text labeling five seismic stations (marked with blue squares). Four stations were operating; Cerro Negro (CENE) was offline during this reporting period. The active summit area of Pico Central is ~3 km N of the CENE station. Courtesy of INGEOMINAS.

Peaks in seismicity and ash emissions between October 2009 and May 2010. INGEOMINAS reported an abrupt increase in seismicity in October 2009. The occurrence of VT, LP, hybrid, and tremor events had more than doubled since September. On 12 October, a swarm of VT events was detected (figure 39). During the onset of elevated seismicity, INGEOMINAS reported ash emissions during 17-21 October and the Washington VAAC released reports of ash observations from satellite imagery on 16 October.

Figure (see Caption) Figure 39. Seismicity from January 2009 through May 2010 detected from Nevado del Huila included notable peaks in LP earthquakes. In their May 2010 report, INGEOMINAS noted that tremor had been recorded continuously throughout January-May. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

The appearance of volcanic ash in satellite images was periodically reported by the Washington VAAC from October through mid-November 2009. Aided by the web-camera Tafxnú, INGEOMINAS reported observations of ash plumes frequently occurring through November.

The Washington VAAC reported that, after 15 November 2009, volcanic ash was no longer visible in satellite images. In their monthly technical report, INGEOMINAS noted seismic signals suggesting ash emissions in December 2009, and visual observations of white plumes from the summit that were inferred to be gas-rich. As seen on figure 39, LP events peaked dramatically during 9-10 December when signals characterized as drumbeats were detected (see BGVN 37:10 for additional descriptions of drumbeat earthquakes). INGEOMINAS suggested the onset of drumbeat earthquakes was associated with the extrusion of new material to the surface and growth of the lava dome.

INGEOMINAS reported an average of 995 LP earthquakes per month during January-March 2010. VT events tallied on a monthly basis averaged 239 during that same time interval, suggesting an absence of discernible major changes in the volcanic system since the drumbeat earthquake swarm in December 2009. Tremor was detected more frequently over time and from February to May an average increase of 37 events per month was recorded.

As seen at the right on figure 39, during April-May 2010, very high LP seismicity returned. LP earthquakes peaked in May, with a total of 5,141 events. During April-May, the Washington VAAC released advisories in response to possible ash plumes from Huila, however, they did not detect ash due to frequent cloud cover, and because numerous reports indicated eruptions at night, when satellite instruments offer fewer means of detecting ash.

An ML 3.8 earthquake shook the towns of Toéz and Tálaga (15 km SSW and 22 km S respectively) at 0708 on 23 May. These towns are located SW of Pico Central. The earthquake was located 8.13 km SW of Pico Central and was 7.2 km deep (relative to the elevation of the active crater).

Seismicity and ash observations during June-December 2010. In June, direct observations of ash plumes were rare due to weather conditions; however, the Washington VAAC reported ash visible in satellite imagery on 2 June 2010. While LP seismicity remained low in early June 2010, hybrid seismicity emerged from background levels (figure 40). During January-May, typically 3-34 hybrid earthquakes were detected per month. By 14 June, more than 200 hybrid events were occurring per day; however, by 24 June, hybrid earthquakes had decreased to less than 50 events per day. Hybrid earthquakes, events INGEOMINAS attributes to the combined mechanisms of fluid transport and rock fractures, rarely dominate Huila's seismic records.

Figure (see Caption) Figure 40. Seismicity from Nevado del Huila during 2010 included peaks of LP, VT, and tremor episodes. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

As seen on figure 40, during August-November 2010, elevated tremor persisted (630-2,576 episodes per month). LP seismicity peaked in May and then twice between September and December. For the tallest peak (September 2010), counts reached more than 1,000 events per day.

On 3 December at 2054 a felt M 3.4 earthquake within the Páez River drainage centered 6.2 km S of Pico Central had a relatively shallow focal depth of 5.2 km (as measured beneath the crater). Another felt earthquake was reported by residents in the Belalcázar-Cauca area on 29 December. This ML 2.9 event occurred at 2106 with a focal depth of 8 km, located 8.5 km SW of Pico Central. This earthquake lacked any noticeable effect on the stability of the volcanic system.

Seismicity in 2011. In 2011, INGEOMINAS noted that both LP earthquakes and tremor were decreasing over time (figure 41). Tremor persisted at low levels. In June VT and LP earthquakes notably increased to 434 and 623 events, respectively, but returned to background levels during the following month.

Figure (see Caption) Figure 41. This plot of Nevado del Huila's seismicity during January-December 2011 shows a general decline in seismicity. This plot excludes VT earthquakes, highlighting instead the daily count of LP, hybrid, and tremor events. Courtesy of INGEOMINAS.

In November 2011, several moderate earthquakes (M≤4) struck near Huila. In particular, three events had magnitudes 2.8, 3.2, and 4.0. For example, on 26 November, inhabitants of Mesa de Toéz felt an M 4.0 event whose epicenter was 8.5 km SW of Pico Central with a depth of 7.4 km (as measured below the crater). VT epicenters in November were widely distributed throughout the edifice and local region (figure 42). Depths of these earthquakes were within the range of past VT earthquakes (0-12 km). Persistent seismicity SW of Huila also continued in November.

Figure (see Caption) Figure 42. A map and cross-sections showing Nevado del Huila's VT epicenters during November 2011. The active dome is ~3 km N of CENE. INGEOMINAS noted four areas where seismicity was clustered (yellow shaded ovals). Note that the largest highlighted region has been an area of persistent seismicity throughout the year (for example, see figure 38). Seismic stations are marked with blue squares and labels (DIAB, VER2, CENE, BUCO, and MARA). Courtesy of INGEOMINAS.

Seismicity in 2012. The low-level seismicity observed in the last months of 2011 continued through 2012. In a comparison with 2011, the average number of events per year was remarkably reduced in 2012 (VT, LP, and tremor); hybrid earthquakes, however, were the exceptions. The average for hybrid earthquakes per month was slightly higher in 2012 (table 4). Hybrid earthquakes were quite variable in number during 2011, ranging from 0 to 60 per month.

Table 4. Monthly counts for volcanic-tectonic, long period, tremor, and hybrid events detected at Nevado del Huila during 2011-2012. More event types and data appear in INGEOMINAS online reports. Courtesy of INGEOMINAS.

Month Volcanic-tectonic Long-period Tremor Hybrid
Jan 2011 284 388 220 2
Feb 2011 217 1,064 154 15
Mar 2011 217 876 168 13
Apr 2011 168 634 152 0
May 2011 136 729 220 0
Jun 2011 434 623 128 60
Jul 2011 165 416 77 25
Aug 2011 143 491 51 32
Sep 2011 137 304 27 8
Oct 2011 110 371 50 13
Nov 2011 176 219 32 2
Dec 2011 164 195 32 34
2011 Avg: 196 526 109 17
 
Jan 2012 155 245 27 28
Feb 2012 111 159 12 18
Mar 2012 145 200 27 21
Apr 2012 154 244 19 21
May 2012 87 200 34 13
Jun 2012 121 183 11 18
Jul 2012 109 208 14 16
Aug 2012 118 178 15 30
Sep 2012 93 172 5 14
Oct 2012 168 257 18 23
Nov 2012 171 205 9 14
Dec 2012 158 227 26 32
2012 Avg: 133 207 18 21

The wide distribution of epicenters noted in November and December 2011 persisted during January-February 2012, but fewer earthquakes were detected during these months. From March through December, significant clustering was absent, although, in October some events appeared concentrated along Huila's N-S axis.

The largest earthquake in 2012 occurred in March; a 3.8 earthquake shook the town of Toribio (in Cauca) at 0248 on 15 March. The epicenter was 1.8 km E of Pico Central with a focal depth of approximately 3.2 km. Seismicity that month was slightly higher than February (table 4). Throughout the year, VT earthquakes were typically less than M 2.6.

Infrasound monitoring 2009-2012. Augmenting seismic monitoring efforts, an infrasound station installed at the Diablo monitoring site (located ~5 km NNW of the active dome) became operational in July 2009. An additional acoustic monitoring system was installed at the Caloto station (located ~3.7 km from the active dome) in May 2012. Data collected with infrasonic microphones complements seismic instrumentation and can be analyzed with similar techniques. The method has also detected distant explosions from volcanoes such as Sakura-jima, Japan (BGVN 20:08), Fuego, Guatemala (BGVN 36:06), and Stromboli, Italy (BGVN 26:07).

Sulfur dioxide emissions during 2009-2012. INGEOMINAS conducted routine sulfur dioxide (SO2) gas monitoring with differential optical absorption spectroscopy (DOAS) equipment from January 2009 through December 2012. With this mobile scanner, INGEOMINAS conducted traverses along the Pan-American Highway between the cities of Calí and Popayán (figure 43).

Figure (see Caption) Figure 43. On 14 and 24 August 2010, INGEOMINAS technicians traversed routes along the Pan-American Highway with mobile DOAS equipment to measure Nevado del Huila's SO2 gas fluxes. These images include color-coded line segments that correspond to high and low concentrations (red and blue, respectively). The approximate locations of the plume have been shaded to correspond with the locations of high SO2 flux. The plots shows the wavelength on the x-axis and concentration-pathlength (ppm-m) on the y-axis. (Top) This image includes the mapped route between the towns of Santander de Quilichao and Villarrica where the gas plume was scanned on 14 August. The wind speed was 10.8 m/s, wind direction was 294°, and SO2 flux was 28.2 kg/s (1,441 t/d). (Bottom) This image includes the results from 24 August when field technicians traversed routes between Pescador and Villarrica. SO2 flux was 23.3 kg/s (2,020 t/d); wind speed and direction were not reported. Courtesy of INGEOMINAS.

Scanning DOAS systems at fixed locations were operating during 2009-2012. During October 2009, elevated SO2 emissions were detected by the Calí and Santander de Quilichao stations (figure 44). In September 2009, a station was operating in Manantial (~53 km W of Huila).

Figure (see Caption) Figure 44. During 7 January 2009-27 November 2012, INGEOMINAS measured the SO2 flux from Nevado del Huila in a series of numbered campaigns (x-axis). A total of 137 values were reported from three detection methods, scan DOAS stations (corresponding to numbers 33 and 35 dating from October 2009, and 55-57 dating from June 2010), FLYSPEC (numbers 118-122 dating from May 2012, and 128 and 129 dating from August 2012), and mobile DOAS (all other values). Red and blue highlighting distinguishes the datasets from each year. SO2 detection was conducted several times each month and the maximum value from each measurement was reported. Courtesy of INGEOMINAS.

Wind velocity has a strong bearing on the computed SO2 flux. In their December 2011 technical bulletin, INGEOMINAS discussed the variability in windspeed and direction, including the Weather Research and Forecasting (WRF) modeling system used for calculations during 2011 (figure 45). The WRF was public domain software available online and was developed in order to provide atmospheric simulations based on numerical modeling.

Figure (see Caption) Figure 45. INGEOMINAS released the source of their windspeed data used for SO2 flux calculations in their December 2011 technical report. (top) This plot shows the datapoints used throughout 2011 for windspeed values determined by the WRF Model. (bottom) These images show a map of the expected aerial extent of the gas plume, a series of photos showing plume conditions during the SO2 surveys, and a table of the measurements from three surveys in December. Courtesy of INGEOMINAS.

In May and August 2012, INGEOMINAS reported the results from FLYSPEC (a portable UV spectrometer) surveys and discussed the variations observed in SO2 flux. They emphasized that SO2 fluxes were low, a finding consistent with previous measurements during this post-crisis period (dome growth had ceased by November 2009). They also mentioned that seismicity had been low in May 2012, particularly in those events related to fluid motion (LP earthquakes, for example).

Flux calculations required wind speed data from the WRF models and daily forecasts from the Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM), Colombia. Wind speeds in the range of 6-12 m/s during 8-29 May 2012 were applied to SO2 flux calculations.

Elevated SO2 emissions from Huila were detected almost daily by the OMI spectrometer during 2009-2012. The AURA satellite maps SO2 in the atmospheric column using ultraviolet solar backscatter. A flux can be estimated for the OMI spectrometer data by looking at the total mass of SO2 measured and the time it took to accumulate. On this basis, INGEOMINAS compared peaks in SO2 flux detected during traverses with DOAS (mobile and scanning) with OMI data for October 2009 (figure 46).

Figure (see Caption) Figure 46. In October 2009, elevated SO2 flux was detected from Nevado del Huila by three remote sensing techniques. (Top) The plotted values show combined datasets from mobile DOAS, OMI, and scan DOAS. (Bottom) The OMI spectrometer on the AURA satellite detected 9.95 kt of SO2 on 20 October 2009 (left) during its pass at 2414-2417 local time (coverage area of 368,974 km2, recording a maximum value of 43.3 Dobson Units (DU)). On 26 October 2009 (right) it detected 7.79 kt of SO2 during its pass at 2337-2340 local time (coverage area of 314,303 km2, recording a maximum value of 31.12 DU). Courtesy of INGEOMINAS and Simon Carn, Michigan Technological University and Joint Center for Earth Systems Technology, University of Maryland Baltimore County.

Lahar investigations. INGEOMINAS maintained seven early warning systems to warn of downstream flooding in vulnerable municipalities such as Belalcázar. At sites within the drainages of the Páez and Símbola rivers, flow monitoring with geophones has continued since October 2006, employing equipment installed by the INGEOMINAS Popayan Observatory in collaboration with the Nasa Kiwe Corporation (CNK). CNK is a relief group that has been active in this area of Colombia since the 1994 earthquake and resultant landslides that devastated the Cauca and Huila regions, including communities along the Páez river (BGVN 19:05). Those events also damaged the Tierradentro archaeological sites, a UNESCO World Heritage Site since 1995.

Following Huila's 2007 lahars (BGVN 33:01), Worni and others (2012) conducted fieldwork and reconstructed events in order to model future lahars for mitigation purposes. The researchers argued that large-volume lahars (tens to hundreds of millions of cubic meters) require targeted studies. The authors noted that "in 1994, 2007, and 2008, Huila volcano produced lahars with volumes of up to 320 million m3." To constrain the dimensions of simulated flows, they used inundation depths, travel duration, and observations of flow deposits from the April 2007 events and applied the two programs LAHARZ and FLO-2D for lahar modeling.

LAHARZ was developed by USGS scientists in order to provide a deterministic inundation forecasting tool; this program was designed to run in a Geographic Information System (GIS) environment (Schilling, 1998; Iverson and others, 1998). "For user-selected drainages and user-specified lahar volumes, LAHARZ can delineate a set of nested lahar-inundation zones that depict gradations in hazard in a manner that is rapid, objective, and reproducible" (Schilling, 1998). Worni and others (2012) presented results from the semi-empirical LAHARZ models along with physically-based results from FLO-2D (FLO-2D Software I, 2009) in order to forecast future inundation areas with specified flow volumes (figure 47). The authors concluded that, despite local deviations, the two models produced reasonable inundation depths (differing by only 10%) and encouraged future investigations that could address sources of uncertainty such as the effects of sediment entrainment that would cause dynamic changes in lahar volumes.

Figure (see Caption) Figure 47. Results are shown from two modeling programs to understand lahar hazards from Nevado del Huila, FLO-2D (top three images) and LAHARZ (bottom three images), for the specified flow volumes. Note the modeled effects on the Belalcázar region (located ~20 km S of Huila). Three scenarios are presented based on lahar flow volumes of 3 x 108, 6 x 108, and 10 x 108 m3. Image from Worni and others (2012).

Deformation monitoring during 2009-2012. An electronic tilt station was operating in July 2009, located at the Diablo monitoring site ~6.26 km NW of Pico Central (4.1 km above sea level). Telemetered data from a new electronic tilt station became available in May 2012; the station was located in the town of Caloto, located ~4 km SSW of Pico Central (4.2 km above sea level). Data from Diablo and Caloto was presented in the monthly technical bulletins posted online by INGEOMINAS.

After seven months of calibrations, INGEOMINAS developed an initial baseline for the new tilt data. The N and E components of Caloto recorded minor fluctuations during this time period. The trend of the E component was generally stable while the N component detected a gradual excursion during 17 June-25 September 2012.

References. FLO-2D Software I, 2009, FLO-2D User's Manual. Available at: www.flo-2d.com.

Iverson, R.M., Schilling, S.R, and Vallance, J.W., 1998, Objective delineation of areas at risk from inundation by lahars, Geological Society of America Bulletin, v. 110, no. 8, pg. 972-984.

Schilling, S.P, 1998, LAHARZ: GIS programs for automated mapping of lahar-inundation hazard zones, U.S. Geological Survey Open-File Report 98-638, 80 p.

Worni, R., Huggle, C., Stoffel, M., and Pulgarín, B., 2012, Challenges of modeling current very large lahars at Nevado del Huila Volcano, Colombia, Bulletin of Volcanology, 74: 309-324.

Geologic Background. Nevado del Huila, the highest peak in the Colombian Andes, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the volcanic complex. The first historical activity was an explosive eruption in the mid-16th century. Long-term, persistent steam columns had risen from Pico Central prior to the next eruption in 2007, when explosive activity was accompanied by damaging mudflows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Popayán, Popayán, Colombia; Washington Volcanic Ash Advisory Center (VAAC), NOAA Science Center Room 401, 5200 Auth road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Ozone Monitoring Instrument (OMI), Sulfur Dioxide Group, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/); Nasa Kiwe Corporation (CNK) (URL: http://www.nasakiwe.gov.co/index.php); Weather Research Forecasting (WRF) (URL: http://www.wrf-model.org/index.php).


Izu-Oshima (Japan) — January 2013 Citation iconCite this Report

Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Non-eruptive May 2010 surface deformation from inferred deep instrusion

Oshima is an active volcano located on the northern tip of the Izu-Bonin volcanic arc. Our last report of activity at Oshima (BGVN 21:08) enumerated a flurry of shallow low-frequency earthquakes beneath the top and W flank of the volcano that started on 5 August 1996.

Since those relatively benign events, the Japan Meteorological Agency (JMA) had not observed any subsequent events worthy of note until May 2010 when land surface inflation was detected. The inflation was registered by a strainmeter, a Global Positioning System (GPS) network (run by the Geospatial Information Authority of Japan, GSI), and a tiltmeter network (run by the National Research Institute for Earth Science and Disaster Prevention, NIED).

In July 2010 seismicity in the shallow parts of and around Oshima began to increase. (High seismicity synchronous with inflation of the edifice was seen earlier, including in 2004 and 2007). These events were considered to be due to magma intrusion into the deeper part of the volcano. There were no remarkable changes in surface phenomenon. In September, the inflation that was detected in May began declining. Seismicity in the shallow parts of and around Oshima continued at a low level with some small earthquakes which temporally increased in the western offshore areas of Oshima on 22 December 2010.

The earthquakes increased in frequency again on 9 February 2011. GPS and strainmeter measurements indicated contraction since January, but the trend reversed to show inflation in October 2011. Seismicity remained at a low level. Very low level gas emissions were sometimes observed by a camera positioned on the NW summit. Based on a field survey on 28 October, no remarkable change in surface phenomena was observed.

No remarkable activity has been noted since October 2011. Throughout the noted activity, JMA held the Alert Level at 1.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 parasitic cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high subplinian eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


Kikai (Japan) — January 2013 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Steam plumes rose to 800 m duing latter half of 2012

Kikai is a 17 x 20 km mostly submarine caldera as close as ~40 km from the S margin of the island of Kyushu (see figure 1 in BGVN 37:07; also see Shinohara and others, 2002, for 16 journal articles devoted to this volcano. Maeno, 2008, offers an online overview). A few areas on the caldera rim lie above water (figure 2). Mild-to-moderate emissions have often occurred at the dome called Iwo-dake (alternately spelled Iodake, figure 2). Table 4 summarizes the seismicity and steam plume observations for July-December 2012, an interval of calm, absence of tremor, and low hazard status.

Figure (see Caption) Figure 2. A shaded-relief, contour map of Kikai caldera that labels three islands on the N caldera rim, Satsuma Iwo-jima, Showa Iwo-jima, and Take-shima. Satsuma Iwo-jima contains the highest point of the complex (704 m elevation). On that island, the cones Iwo-dake (a rhyolitic volcano) and Inamura-dake (a basaltic volcano) both reflect post-caldera volcanism focused along or just inside the caldera's wall (the shaded, scalloped line trending NE across the island). The island Showa Iwo-jima emerged during the caldera's last major eruptions, during 1934-1935, starting with floating pumices and including late-stage lava emissions that helped armor the island and allowed it to erode only modestly during the subsequent decades of breaking waves. The caldera floor chiefly resides 300-500 m below sea level but it also contains some post-eruptive cones. From Fukashi Maeno (2008).

Table 4. Monthly summary of seismicity and plume observations at Kikai during July-December 2012. All reported plumes were described as white. Data courtesy of JMA.

Month Earthquakes per month Maximum steam plume height (m above Iwo-dake crater rim)
Jul 2012 238 800
Aug 2012 187 300
Sep 2012 193 500
Oct 2012 219 700
Nov 2012 168 400
Dec 2012 -- --

We last reported on Kikai activity through mid-2012 (BGVN 37:07) covering generally small steam plumes and monthly seismicity of up to ~200 earthquakes per month through June 2012. This report is a compilation of subsequent monthly reports of volcanic activity through December 2012 from Japan Meteorological Agency (JMA) monthly reports. The Alert Level remained constant at Level 2 (on a scale of 1-5: 2 = "Do not approach the crater"), before being downgraded to Level 1 in December 2012.

Between July and September 2012, plume emissions at the Iwo-dake summit crater continued (table 4). Weak incandescence was recorded at night with a high-sensitivity camera on 22 July, 28 August, 6 November and 22-24 November. Seismic activity remained at low levels. No unusual ground deformation was observed in GPS data through December 2012.

An aerial observation conducted by the Japan Maritime Self-Defense Force (JMSDF) on 11 September 2012 revealed white plumes rising from Iwo-dake's summit crater and flanks.

The results of a field survey conducted from 17-20 November 2012 showed no remarkable change in white fumes from Iwo-dake. Infrared images also found that the temperature distribution had remained essentially unchanged. Aerial monitoring conducted by the Japan Coast Guard (JCG) on 25 November 2012 revealed the presence of brown and green discolored water around the eastern coast (similar findings as a previous survey) as well as patterns of steaming similar to those observed during the field survey. SO2 emissions during 17-20 November 2012 were measured to be ~400 tons/day; a previous survey conducted in July 2012 yielded an estimated flux of ~500 tons/day.

References. Shinohara, H., Iguchi, M., Hedenquist, J.W., and Koyaguchi, T., 2002, Preface to special volume, Earth, Planets and Space 54 (3), pp. 173-174.

Maeno, F, 2008, Geology and eruptive history of Kikai Caldera, Earthquake Research Institute, University of Tokyo (URL: http://www.eri.u-tokyo.ac.jp/fmaeno/kikai/kikaicaldera.html); accessed 23 February 2013.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. Kikai was the source of one of the world's largest Holocene eruptions about 6300 years ago. Rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred in the 20th century at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km east of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Kuchinoerabujima (Japan) — January 2013 Citation iconCite this Report

Kuchinoerabujima

Japan

30.443°N, 130.217°E; summit elev. 657 m

All times are local (unless otherwise noted)


Increased seismicity, 11 December 2011-5 January 2012

Since a small eruption in 1980, Kuchinoerabu-jima experienced numerous periods of elevated seismicity, with volcanic earthquakes and tremor detected at least through December 2009 (BGVN 35:11). The volcano is located in the Ryukyu Island arc, off Japan's SW coast (figure 4).

Figure (see Caption) Figure 4. A map of the major volcanoes of Japan. Kuchinoerabu-jima is at the lower left. Courtesy of USGS/CVO.

Recent monthly reports of volcanic activity from the Japan Meteorological Agency (JMA) translated into English resumed in October 2010. The only recent English-translated JMA report on Kuchinoerabu-jima available online through December 2012 was in January 2012. We know of no other recent report on this volcano's seismic activity; therefore, this report summarizes seismicity between December 2011 and January 2012.

According to JMA, seismicity increased to a relatively high level immediately after 11 December 2011, but then decreased on 5 January 2012. On 20 January 2012, the Alert Level was lowered from 2 to 1; JMA noted that the possibility of an eruption was minimal.

During the December 2011-January 2012 period, no significant change in plume activity was observed, and plume heights remained below 100 m above the crater. According to a field survey on 11 January, infrared images (compared to images obtained in December 2011) showed no significant change in temperature distribution either at the summit or on the W slope of Shin-dake (also refered to as Shin-take), the youngest and most active cone.

Field surveys found that sulfur dioxide levels were 50 and 100 metric tons/day on 12 and 13 January 2012, respectively, which were lower than those recorded in December 2011 (200 metric tons/day on 9 December 2011).

According to JMA, continuous GPS measurements have established a baseline across Shin-dake, collecting data since September 2010. Shin-dake's rate of change in surface deformation at the stations has been slowing since September 2011.

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km west of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shintake, formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


San Cristobal (Nicaragua) — January 2013 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Ash eruption during 25-28 December 2012

Our last report highlighted monitoring efforts at San Cristóbal and the explosive eruption that began on 8 September 2012 (BGVN 37:08). By 16 September 2012, seismicity and emissions had decreased; however, the Instituto Nicaragüense de Estudios Territoriales (INETER) announced in late December 2012 that volcanic activity had re-started. In this report, we cover the time period of 25-31 December when seismicity, explosions, and gas-and-ash emissions were reported.

At 2000 on 25 December 2012, observers noted a series of gas-and-ash explosions from the summit. The wind carried the fine- to sand-sized ash SW. Several hours prior to this activity, INETER had reported that seismicity was elevated but sulfur dioxide emissions (SO2) were relatively low compared to measurements from previous days.

During the early hours of the morning on 26 December, winds dispersed fine ash NW, W, and SW. Sand-size ash was fell on the W and SW flanks (figure 28). Civil Defense authorities from the municipality of Chinandega reported an ash plume up to 500 m above the summit and described the event as a "moderate eruption" similar to the 8 September 2012 event.

Figure (see Caption) Figure 28. A view S toward San Cristóbal with an ash plume drifting westerly on 26 December 2012. The lower hills to the right are part of El Chonco, an older volcanic edifice. Photograph by Hector Retamal, AFP, Getty Images.

On 26 December, government officials reported to Reuters that local inhabitants were evacuating. Rosario Murillo, a government spokeswoman, called on residents within a 3 km radius of the volcano to leave the area; some families had already self-evacuated.

By 1000 that day, INETER reported that seismicity had increased, and that they had received reports from Civil Defense stating that an eruption of fine ash rose to ~2,500 m above the crater. By the early afternoon, four major seismic events were detected and interpreted as explosions at the summit. Ashfall from these events primarily affected an area within a 5-6 km radius of the summit: El Viejo, Las Rojas, Banderas, Abraham Rugama, and those communities north of Chinandega's urban limit Grecia (particularly two communities called ##1 and ##4; see figure 19 in BGVN 36:12 for major town locations).

In their second communication on 26 December, INETER suggested that local inhabitants protect their water sources from ashfall, particularly those communities W, SW, and S of the volcano. They also announced that grazing lands would be closed in those regions due to the quantity of ash that had fallen. Research at Raupehu, New Zealand, and elsewhere has found that grazing animals can suffer damage to their teeth and poisoning due to elevated sulfur and fluorine if they consume ash-covered plants (Cronin and others, 2003). Precautions were also recommended for young children who could be adversely affected by inhaling fine ash. INETER noted that aviation traffic had been alerted to the presence of ash in the region.

The Washington Volcanic Ash Advisory Center (VAAC) detected ash from San Cristóbal during 26-28 December. Emissions were ongoing during that time period; plumes rose 2.4-4.3 km a.s.l. and drifted approximately W over the Pacific Ocean as far as 670 km WNW from the summit (figure 29).

Figure (see Caption) Figure 29. The aerial extent of observed volcanic ash from San Cristóbal was concentrated in three discrete regions mainly offshore of Central America at 0430 on 28 December 2012. The red polygons were developed by the VAAC as geospatial files (KML) for display in Google Earth. Courtesy of Washington VAAC and Google Earth.

INETER reported to local news agencies that 7 of the 13 municipalities of Chinandega were affected by ashfall by 27 December. Visibility was greatly reduced within the urban city of Chinandega. Emissions continued from the summit and reached 200 m above the crater rim in the morning. At the time of their second online notice, a plume of fine ash was visible rising up to 500 m above the crater, and small-to-moderate sized explosions of gas and ash continued.

On 28 December, the minister of Agriculture and Forestry told the local news agency, La Jornada, that while 2 millimeters of ash had fallen in some areas around the volcanic edifice, the farming areas should not be adversely affected since most of the crops had already been harvested. The public utility company, ENACAL, conducted investigations into water quality for the region.

News agencies reported that up to 20 km of highway was affected by ashfall along the Pan-American Highway between Honduras and Nicaragua. Vehicles opted to use headlights due to reduced visibility. La Jornada reported that a total of 268 people had left the area of San Cristóbal by 28 December and 68 were evacuated by the national humanitarian agency (Nicaraguan Humanitarian Rescue Unit, UHR).

INETER reported that small to moderate sized explosions had occurred in the morning of 28 December and a significant increase in SO2 flux was detected. This announcement included warnings regarding eye, skin, and respiratory irritation due to volcanic gases. There were also recommendations regarding ash removal from roofs and structures. Ash was distributed NW, W, and SW from the volcano and satellite images detected ash extending across the Pacific Ocean following the regional airstream offshore of El Salvador.

After an explosion of ash and gas at 1100 on 28 December, emissions throughout the day were ash-poor. Seismicity also decreased that day and, by 29 December, explosions had ceased and diffuse gas emissions continued. In their online bulletin, INETER reported that, as of 31 December, no ash explosions had been detected over the past two days. Gas emissions continued from the summit but SO2 levels had returned to normal.

Volcanic hazards map for San Cristóbal. A map of volcanic hazards was available on the INETER website for the region of San Cristóbal (figure 30). Volcanic ballistics, lahars, landslides, lava flows, and tephrafall were assessed and likely impacted areas were delineated. The tephrafall region corresponded to the prevailing winds and correlated well with ash-effected regions during the December 2012 events.

Figure (see Caption) Figure 30. Volcanic hazards from San Cristóbal include ejecta, lahars, landslides, and lava flows. This map was released in April 2006 and developed to show the aerial extent of potential events. Densely populated regions are yellow, road systems are black, and rivers are blue; additional color regions correspond to hazards listed in the key (in Spanish). The brown circle has a radius of 5 km and encompasses the main volcanic edifice indicating the maximum expected extent of ballistics (volcanic bombs for example); the two tan regions indicate the extent of possible tephra fall (where lighter shading indicates a medium-level risk zone and darker is higher-level risk); red regions follow major drainages where lahars and landslides could occur; the region shaded pink encompasses the areas most likely effected by future lava flows. Courtesy of INETER.

Reference. Cronin, S.J., Neall, V.E., Lecointre, J.A., Hedley, M.J., and Loganathan, P., 2003, Environmental hazards of fluoride in volcanic ash: a case study from Ruapehu volcano, New Zealand, Journal of Volcanology and Geothermal Research, 121, 271-291.

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); La Jornada (URL: http://www.lajornadanet.com/diario/archivo/2012/diciembre/28/1.php); La Prensa de Nicaragua (URL: http://www.laprensa.com.ni/2012/12/27/ambito/128746/imprimir); Reuters.

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (BGVN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (BGVN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (BGVN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (BGVN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure (see Caption) Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure (see Caption) Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure (see Caption) Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).