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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

Cleveland (United States) Intermittent dome growth and explosions with small ash plumes, July 2018-January 2019

Planchon-Peteroa (Chile) New eruption begins in September 2018; continuous ash emissions and intermittent explosions December 2018-February 2019

Copahue (Chile-Argentina) Frequent emissions and small ash plumes continue from July through 7 December 2018

Kilauea (United States) Fissure 8 lava flow continues vigorously until 4 August, ocean entry ends in late August, last activity at fissure 8 cone on 5 September 2018

Piton de la Fournaise (France) Eruption from 15 September to 1 November produced a lava flow to the E

Veniaminof (United States) Eruption with lava flows and ash plumes during September-December 2018

Poas (Costa Rica) Frequent changes at the crater lake throughout 2018

Nevados de Chillan (Chile) Dome growth and destruction with several explosive events, June-November 2018

Sabancaya (Peru) Frequent ash plumes continued during June-November 2018

Stromboli (Italy) Explosive activity produced ash, lapilli, and bombs, with occasional spattering during July-October 2018

Santa Maria (Guatemala) Ash plumes, degassing, and avalanches continue during May-October 2018 with occasional lahars

Kilauea (United States) Lava fountains on the Lower East Rift Zone build 50-m-high pyroclastic cone and 13-km-long lava flow that engulfs Kapoho Bay during June 2018; 533 homes destroyed since 1 May



Cleveland (United States) — February 2019 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Intermittent dome growth and explosions with small ash plumes, July 2018-January 2019

Dome growth and destruction accompanied by small ash explosions have been typical behavior at Alaska's Cleveland volcano in recent years. Located on Chuginadak Island in the Aleutians, slightly over 1,500 km SW of Anchorage, it has historical activity, including three large (VEI 3) eruptions, recorded back to 1893. The Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC) are responsible for monitoring activity and notifying air traffic of aviation hazards associated with Cleveland. Its remoteness makes satellite imagery an important source of information for interpreting activity. This report covers continuing thermal and minor explosive activity during July 2018 through January 2019.

After evidence of a small lava dome on the floor of the summit crater appeared in late June 2018, weakly elevated surface temperatures were observed intermittently during July. A small deposit of fresh ejecta was observed in satellite data at the end of July. Weak and moderately elevated surface temperatures were observed during August and into September. A clear satellite image in mid-September confirmed the presence of a growing dome in the summit crater. No seismic or infrasound activity was reported in October or November, and persistent clouds mostly obscured satellite images. Four small explosions were reported during December 2018, two of them produced small ash plumes. A single explosion in early January produced a tephra deposit visible in satellite images, and a new dome was visible growing inside the crater during the middle of the month. Intermittent elevated surface temperatures were observed during the rest of January 2019, but no additional explosions were reported.

Low levels of unrest continued at Cleveland during July 2018. Elevated surface temperatures were detected through 3 July following the observation of a small lava dome on the floor of the summit crater on 25 June (BGVN 43:07). Weakly elevated surface temperatures were observed in high resolution satellite data on 11 July, and several times during the second half of the month when weather conditions were clear. Field crews working on Chuginadak Island on 19 July 2018 repaired the Cleveland web camera. Steaming at the summit was visible in both web camera and satellite images at times during the last week of July (figure 26). On 24 July, a small deposit of ballistic blocks was observed in satellite imagery within the summit crater and just below the eastern crater rim. These blocks suggested to AVO that minor explosive activity occurred at the summit that was below the detection threshold of the seismic and pressure sensors.

Figure (see Caption) Figure 26. The Cleveland webcam captured a brief clear view of the often-cloudy summit, exhibiting minor steaming, on 24 July 2018. Image courtesy of AVO/USGS.

No eruptive activity was detected during August. Moderately elevated surface temperatures were observed on 7 August and most days during the second week of the month. Occasional clear web camera views of the summit showed slight steam emissions. The Aviation Color Code was reduced from Orange to Yellow and the Volcano Alert Level to Advisory on 22 August 2018 after several weeks of only elevated surface temperatures in the summit area. Minor explosive activity had last been observed in late July and since that time there had been no evidence of lava extrusion in the summit crater. Elevated surface temperatures continued to be observed, however, during the last two weeks of the month.

Weakly elevated surface temperatures in the summit crater continued to be observed in satellite data during periods of clear weather in the first week of September. A few moderately elevated surface temperatures appeared in the second week, and continued during the third week of September. An unobscured satellite view on 10 September (figure 27) showed the first evidence of an emplaced lava dome within the crater. Temperatures were moderate to weakly elevated throughout the last week of the month. Satellite observations from 20 September suggested that the small collapse crater in the center of the summit dome emplaced over the summer was beginning to inflate, but clear evidence of new lava emplacement was not detected.

Figure (see Caption) Figure 27. Cleveland volcano on 10 September 2018 showed evidence of an emplaced dome within the summit crater with both a natural color (bands 4,3,2) image of the summit (upper) and an atmospheric penetration image (bands 12, 11 and 8A) that shows the thermal anomaly from the summit dome. Courtesy of Sentinel Hub.

No significant activity was detected in seismic or infrasound (pressure) sensor data during October or November 2018. Satellite views of the volcano were obscured by clouds for most of the time; elevated surface temperatures were observed in satellite data a few times in the last few days of October and during the first half of November; there were no observations of activity in mostly cloudy satellite images at the end of November.

Although a few satellite observations of elevated surface temperatures at the summit were made during the first week of December 2018, two small explosions occurred during the second week. The first happened on 8 December at 2355 AKST (0855 UTC on 9 December). The second, which had a higher peak seismic amplitude, occurred on 12 December at 1153 AKST (2053 UTC). No ash cloud was observed after either event, though satellite views were largely obscured by clouds at the time. The color code and Alert Level were raised to Orange/Watch after the second explosion. Elevated surface temperatures continued to be observed in satellite imagery at the volcano's summit during the second week. Another short-lived explosion occurred on 16 December at 0737 AKST (1637 UTC). A small ash cloud drifting NE was observed afterwards in satellite imagery. Elevated surface temperatures appeared following this explosion. Conditions were mostly cloudy for the remainder of December; occasional clear satellite views showed no further temperature anomalies. Local seismic sensors recorded a short-lived explosion at 1817 AKST on 28 December (0317 UTC 29 December). A pilot report indicated an ash plume from the event at 5.2 km altitude moving E.

Satellite images through 2 January 2019 showed that the explosion on 29 December enlarged the diameter of the summit crater by about 25 m and large ballistic blocks impacted the upper edifice N and E of the crater. After 10 days of diminished activity following the sequence of explosions in December, AVO reduced the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory on 7 January 2019. On 9 January at 1015 AKST (1915 UTC) the single local seismic sensor recorded a small, short-lived explosion. A satellite image captured three hours after the event revealed a tephra deposit, a steam plume, and elevated temperature at the summit (figure 28). The explosion was not detected on regional infrasound arrays, nor was a volcanic cloud observed above the meteorological clouds at 3 km altitude.

Figure (see Caption) Figure 28. A Landsat 8 image acquired three hours after the explosion at Cleveland on 9 January 2019 revealed a small steam plume and tephra deposit in visible imagery (left), and heat at the crater in the short-wave infrared (SWIR) bands (right, pan-sharpened false color). The small deposit is consistent with the geophysical evidence for the small size of the explosion. Image created by Hannah Dietterich, courtesy of AVO/USGS and Landsat 8.

Satellite data showed that starting around 12 January, a new and growing lava dome was present in the summit crater. It continued to grow slowly through 16 January. This prompted AVO to increase the Color Code to ORANGE and the Alert Level to WATCH on 17 January. Strongly elevated surface temperatures were observed in satellite imagery on 19 and 20 January, reflecting growth of a lava dome. The local infrasound array and a second seismic station near Cleveland that had been offline since 23 September 2018, returned data again briefly on 25 January. Weakly elevated surface temperatures were observed in satellite images during the last week of January. A steam plume was observed at the volcano during clear weather on 27 January. Satellite observations collected after 16 January showed the center of the newly emplaced lava dome slowly subsiding. No explosive activity was detected in regional seismic or infrasound data during the last week of the month.

The physically remote location of Cleveland in the Aleutians, and the often-unfavorable meteorological conditions that limit visible satellite observations make the thermal infrared data a valuable component of interpretations of activity. During July 2018 through January 2019 intermittent thermal signals were reported in the MIROVA graph (figure 29). A few of these signals (in September 2018 and January 2019) could be correlated to visual satellite images that confirmed growth of a summit lava dome.

Figure (see Caption) Figure 29. MIROVA data for the year ending on 31 January 2019 shows intermittent thermal anomalies at Cleveland volcano. Courtesy of MIROVA.

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey (USGS), 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 (ADGGS), 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/).


Planchon-Peteroa (Chile) — January 2019 Citation iconCite this Report

Planchon-Peteroa

Chile

35.223°S, 70.568°W; summit elev. 3977 m

All times are local (unless otherwise noted)


New eruption begins in September 2018; continuous ash emissions and intermittent explosions December 2018-February 2019

Planchón-Peteroa, a large basaltic to dacitic volcanic complex, lies on the remote Chile-Argentina border roughly 200 km S of Santiago, Chile. Its intermittent eruptive history has been characterized by short-lived explosive events with gas and ash plumes from active craters around the Volcán Peteroa area (figure 10). The most recent eruption, from February-June 2011, was a series of sporadic ash and gas plumes which rose as high as 5.5 km altitude and produced ashfall as far as 70 km away (BGVN 38:11). After seven years of little surface activity, a new series of ash emissions and explosive activity began in September 2018; a major seismic swarm in 2016 did not result in surface activity. Information for this report, covering through February 2019, was provided primarily by Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS) and the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 10. The Planchón-Peteroa volcanic complex was last active from February to June 2011, as seen in this image taken on 23 April 2011 from Santa Cruz de Colchagua, located 100 km NW. Image copyright by Andres Figueroa Z (HBOC), courtesy of Cumbres y Montañas de O'Higgins and used with permission from the photographer.

Planchón-Peteroa remained quiet during 2014 and 2015. A significant seismic swarm during 2016 led SERNAGEOMIN to raise the alert level for nearly the entire year, although no surface eruptive activity took place. A smaller seismic event in 2017 also did not include surface activity. Increased emissions that included particulate material were first reported in September 2018; the first explosions with ash took place in early November 2018. Persistent emissions with dense plumes of ash began in mid-December and continued through February 2019; intermittent pulses and explosions during that time coincided with increased seismic and thermal activity.

Activity during 2014-2015. Background levels of volcano-tectonic (VT) and long-period (LP) earthquakes were reported by SERNAGEOMIN throughout 2014 and 2015. A single seismic event greater than M 3.0 was reported on 11 May 2014, located within 1 km of the crater. Inclinometer, SO2, and thermal data all indicated no significant changes during the period. During March-July 2015 sporadic fumaroles were observed rising less than 200 m from the active crater.

Activity during 2016. An increase in LP seismic events from a few to several hundred per month was noted by SERNAGEOMIN beginning in January 2016. As a result, they increased the Alert Level of the volcano from Green to Yellow on 22 January. The webcam revealed degassing of mainly water vapor reaching close to 200 m above the active crater. During the first two weeks of February 2016 the number of LP events increased ten-fold from 328 in January to 3,634; all the events were smaller than M 1.1. The rate of LP seismicity increased further during the last two weeks of February to 7,301 events, and the steam plumes reached 400 m above the crater. LP seismicity remained high during March with 9,627 measured events; similar numbers of events were sustained through May 2016 (figure 11).

Figure (see Caption) Figure 11. Seismicity at Planchón-Peteroa from October 2015 through February 2019. Two periods of increased seismicity were detected prior to 2018, although the only observed changes in surface activity were slight increases in the height and intensity of the steam plumes. The first event, from January 2016-January 2017 included periods with very high numbers of both VT and LP events at different times during the year. The second period of increased seismicity was from July to December 2017; the numbers of VT events were elevated briefly in July, but the LP event numbers remained elevated through December. The number of LP seismic events began increasing again in July 2018; the first particulate emissions were noted in September, and significant explosions with ash began in November 2018. Note two vertical axes on graph, the left represents numbers of LP seismic events in orange, the right represents the number of VT seismic events in blue. Data courtesy of SERNAGEOMIN.

LP seismicity decreased substantially to only 470 events during the first two weeks of June 2016, leading SERNAGEOMIN to reduce the Alert Level to Green. However, during the second half of June a spike in the VT events from 8 during the first half of the month to 944 caused authorities to raise the Alert Level back to Yellow. This increase in VT seismic events was also accompanied by an increase in the number and spectral frequency of the LP events. They changed from having dominant frequencies between 1.9 and 2 Hz to 4-5 Hz, with a location that moved closer to the crater zone than before, and occurred at depths of around 1.5 km. On 28 June a M 3.4 VT event occurred 4.3 km NNE of the crater at a depth of 4.8 km. LP events numbered between 2,100 and 4,100 events monthly during June-September.

VT seismic events increased to their highest levels of 2016 during July (4,609 events) before beginning a gradual decline through the end of the year, ending with about 700 events in December (figure 11). A strong steam plume rose 550 m above the crater on 4 July 2016 and was accompanied by 400 VT events. The number of LP events increased significantly for the second time during the year beginning in October and remained over 14,000 events through January 2017. Three seismic events with local magnitude (ML) greater than M 3.0 were recorded on 7, 12, and 16 October; the locations of the events were approximately 3 km NNW at an average depth of 5 km. A M 3.4 event was recorded on 19 November. Low-level steam plumes did not rise more than 200 m above the crater for the remainder of the year. SERNAGEOMIN installed two new seismic stations, on 29 November and 15 December 2016.

Activity during 2017. Levels of both VT and LP seismic events declined during January-May 2017. A M 3.5 VT earthquake on 19 February was located 3.7 km NNW of the crater and 4.5 km deep. On 28 March, a M 3.6 event occurred in a similar location. Steam plumes occasionally rose as high as 200 m during the period. SERNAGEOMIN lowered the Alert Level to Green on 17 May 2017 based on the gradual decrease in seismicity to baseline levels accompanied by little to no surface activity.

A seismic swarm of 39 events on 15 June was located 14 km SE and 8-10 km deep. VT seismic events during the first half of July 2017 were located 4-7 km deep under the summit craters and included a M 4.0 event on 8 July. An increase in both VT and LP seismicity in early July led SERNAGEOMIN to raise the Alert Level to Yellow on 10 July (figure 11). The monthly number of VT events dropped below 100 in August and remained low for the rest of the year. A M 3.5 VT event was reported on 5 November, located 6.5 km E and 6 km deep. On 14 November seismometers recorded a 30-minute tremor event. A brief increase in degassing began on 23 November; steam plumes reached 600 m the next day but returned to less than 150 m by the end of the month. SERNAGEOMIN lowered the Alert Level to Green in mid-December 2017 as a result of decreased surface and seismic activity.

Activity during 2018. Low levels of surface and seismic activity persisted into early June 2018. Steam plumes rose no more than 500 m above the crater, numbers of VT events remained low, and the numbers of LP events decreased steadily. In mid-May the amplitude of continuous tremor events began to increase. The frequency of the tremor events had been around 1-2 Hz earlier in the year, but beginning on 21 June they increased to around 5 Hz; this was accompanied by an oscillating amplitude seismic signal referred to as "banded tremor." SERNAGEOMIN interpreted the increase in amplitude and the banded tremor as an indication of increased heat in the system, and as a result raised the Alert Level to Yellow on 6 July 2018. The number of LP seismic events increased steadily beginning in June, along with the amplitude of the seismic events, although there were no apparent changes in surface activity (figure 12). Weak thermal anomalies were first detected in satellite data in mid-August. SERNAGEOMIN noted that the locations of the seismic events were migrating closer to the crater, and the depths were shallowing from June to August 2018.

Figure (see Caption) Figure 12. No surface activity was seen at Planchón-Peteroa on 11 July 2018; SERNAGEOMIN had raised the Alert Level to Yellow from Green a few days earlier due to increased seismicity. Photo from SERNAGEOMIN webcam located about 10 km W. Courtesy of SERNAGEOMIN.

SERNAGEOMIN first reported the presence of particulate material in the persistent degassing from the active crater on 21 September 2018, noting that the degassing steam turned "slightly gray" but plumes did not rise more than 600 m above the crater. Mostly-white emissions continued during October, although they specifically mentioned emissions of low-intensity particulate material observed during 13-15 October, rising 600 m above the crater. Three MIROVA thermal alerts appeared on 14 October, the first over 1 MW to be recorded (figure 13). During the second half of October, SERNAGEOMIN noted persistent mostly-white degassing in the webcam that rose up to 700 m above the crater. They also reported webcam images in the second half of October that showed ash emissions rising a short distance above the crater, generally drifting SE, although they did not specify certain dates

Figure (see Caption) Figure 13. A graph of satellite thermal data by the MIROVA project from 8 April 2018 through February 2019 indicates that thermal anomalies were first reported in mid-October 2018; this corresponds with SERNAGEOMIN's observations of emissions containing significant quantities of particular material. Increased thermal activity during December 2018 and February 2019 corresponded with reports of increased explosive activity and ash emissions. Courtesy of MIROVA.

SERNAGEOMIN reported an explosion with an ash emission visible in the webcam on 7 November 2018; they reported the plume height at about 1,000 m above the crater (figure 14). The Buenos Aires VAAC reported the ash plume drifting SE visible in satellite imagery at 4.3 km altitude. Low-altitude ash emissions were observed in the webcam multiple additional times during November. In a special report issued on 7 December, SERNAGEOMIN reported a 1,300-m-high ash emission that dispersed ESE. The Buenos Aires VAAC reported continuous ash emissions beginning on 14 December that lasted through the rest of the month (figure 15).

Figure (see Caption) Figure 14. A webcam located a few kilometers W of Peteroa captured these images of the ash plume released on 7 November 2018. Courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 15. An ash cloud from Planchón-Peteroa was photographed from Paso Vergara on the Chile/Argentina border 5 km NE on 14 December 2018; the ash dispersed to the SE. Courtesy of Volcanes de Chile and SEGEMAR (Servicio Geológico Minero Argentino), copyright by Gendarmeria Nacional Argentina.

Plumes generally drifted SE at 4.6-4.9 km altitude during December, with occasional stronger puffs that were reported as high as 5.8 km altitude (figure 16). On 16 December the webcam recorded high-intensity pulsating ash emissions that drifted 20 km SE. Incandescence was visible around the crater that night. Webcam images showed dark gray plumes during the second half of December, suggesting a high concentration of ash; the pulsating nature of the emissions was observed in the webcam again during 24-27 December, reaching 1,600 m above the crater. Multiple thermal alerts were reported during the second half of the month.

Figure (see Caption) Figure 16. Volcanes de Chile annotated this 15 December 2018 Sentinel-2 satellite image showing the ash plume from Planchón-Peteroa drifting SE into Argentina. Courtesy of Sentinel Hub and Volcanes de Chile.

Activity during January-February 2019. Dense ash plumes were reported daily during January and February 2019 by both SERNAGEOMIN and the Buenos Aires VAAC; plumes heights were generally between 400 m and 1 km above the active crater (figure 17). Higher plumes that reached 2 km above the crater and drifted E were reported on 1 and 3 February (figure 18). SERNAGEOMIN noted that the first of these events was accompanied by an increase in very low frequency seismic activity (VLP).

Figure (see Caption) Figure 17. Dense ash plumes drifted SE from Planchón-Peteroa on 4 January 2019 as seen in this false-color Sentinel-2B satellite image. Courtesy of Sentinel Hub and Volcanes de Chile.
Figure (see Caption) Figure 18. Volcanes de Chile captured this image of a dense ash plume drifting SE over Argentina from the SERNAGEOMIN webcam located about 10 km W of Planchón-Peteroa on 3 February 2018. Courtesy of Volcanes de Chile and SERNAGEOMIN.

Satellite-based SO2 instruments also detected a significant gas plume on 3 February (figure 19). SERNAGEOMIN reported a tremor signal on 14 February 2019 associated with a dense ash plume that rose to 2 km above the summit and drifted NE. Webcam images during the second half of February showed constant degassing; gray plumes drifted mostly SE about 2 km above the summit (figure 20).

Figure (see Caption) Figure 19. The TROPOMI instrument on the Sentinel-5P satellite recorded significant SO2 plumes drifting both E and W of Planchón-Peteroa on 3 February 2019; SERNAGEOMIN reported dense ash emissions the same day. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 20. Explosive activity at Planchón-Peteroa was recorded in Paso Vergara on the Chile/Argentina border 5 km NE on 20 February 2019 at the SEGEMAR CNEA webcam. Courtesy of SEGEMAR (Servicio Geológico Minero Argentino) and Felipe Aguilera Volcanes.

Geologic Background. Planchón-Peteroa is an elongated complex volcano along the Chile-Argentina border with several overlapping calderas. Activity began in the Pleistocene with construction of the basaltic-andesite to dacitic Volcán Azufre, followed by formation of basaltic and basaltic-andesite Volcán Planchón, 6 km to the north. About 11,500 years ago, much of Azufre and part of Planchón collapsed, forming the massive Río Teno debris avalanche, which traveled 95 km to reach Chile's Central Valley. Subsequently, Volcán Planchón II was formed. The youngest volcano, andesitic and basaltic-andesite Volcán Peteroa, consists of scattered vents between Azufre and Planchón. Peteroa has been active into historical time and contains a small steaming crater lake. Historical eruptions from the complex have been dominantly explosive, although lava flows were erupted in 1837 and 1937.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); 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/); Servicio Geológico Minero Argentino (SEGEMAR), Av. General Paz 5445 (colectora), Parque Tecnológico Miguelete, Edificio 14 y Edificio 25, San Martín (B1650 WAB) (URL: http://www.segemar.gov.ar/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Cumbres y Montañas de O'Higgins (URL: https://www.facebook.com/cymohiggins/); Volcanes de Chile (URL: https://www.volcanesdechile.net/, Twitter: @volcanesdechile); Felipe Aguilera Volcanes (Twitter: @FelipeVolcanes, URL: https://twitter.com/FelipeVolcanes).


Copahue (Chile-Argentina) — January 2019 Citation iconCite this Report

Copahue

Chile-Argentina

37.856°S, 71.183°W; summit elev. 2953 m

All times are local (unless otherwise noted)


Frequent emissions and small ash plumes continue from July through 7 December 2018

Copahue, on the border of Chile and Argentina, has frequent small ash eruptions and gas-and-steam plumes. The volcano alert was raised from Green to Yellow (on a scale going from green, yellow, orange, to red) on 24 March 2018 due to an increase in seismic activity and a phreatic explosion. Copahue has a dozen craters with recent activity focused at the Agrio crater, which contains a persistent fumarole field and a crater lake. This report summarizes activity from July through December 2018 and is based on reports issued by Servicio Nacional de Geología y Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur, (OVDAS), Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data.

Throughout July, Copahue produced gas-and-steam and ash plumes that deposited ash on and away from the slopes of the volcano (figure 19). From 1 to 15 July degassing was continuous with a maximum plume height of 300 m above the crater. A more energetic gas-and-steam plume was produced on 18 July (figure 20). Persistent gas and ash plumes during 16-31 July rose up to 1,500 m above the crater. Nighttime incandescence was present throughout the month.

Figure (see Caption) Figure 19. Sentinel-2 natural color satellite images of Copahue that show plumes and dark ash deposition throughout July 2018. The location of the active Agrio crater is indicated by the black arrow in the upper left image. Sentinel-2 Natural Color images (bands 12, 11, 14) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 20. Energetic degassing at Copahue related to hydrothermal activity on 18 July 2018. Webcam image courtesy of SERNAGEOMIN-OVDAS.

Throughout August intermittent gas-and-steam and ash plumes continued due to the interaction of the hydrothermal and magmatic system within the volcano (figure 21). Notices were issued by the Buenos Aires VAAC on 14 and 15 August for diffuse steam plumes possibly containing ash up to an altitude on 3.6 km. Constant degassing, intermittent ash plumes, and nighttime incandescence continued through September (figure 22).

Figure (see Caption) Figure 21. Low-level ash-and-gas emission at Copahue on 11, 24, and 28 of August 2018, and a plume and incandescence on 15 August. Webcam images courtesy of SERNAGEOMIN-OVDAS via CultureVolcan and Roberto Impaglione.
Figure (see Caption) Figure 22. A plume from Copahue on 1 September 2018. Webcam image courtesy of SERNAGEOMIN-OVDAS via Roberto Impaglione.

During September, October, and November, variable gas-and-steam and ash plumes were accompanied by visible incandescence at night. Continuous ash emission was observed from 16 to 30 November (figure 23); similar activity with plume heights up to 800 m from 1 to 6 December. On 2 December a Buenos Aires VAAC notice was issued for a narrow ash plume that drifted ESE. During 6-7 December an ash plume that rose up to 3 km altitude and drifted towards the SW was accompanied by a seismic swarm. No further ash emissions were noted through the end of the year.

Figure (see Caption) Figure 23. A low-lying plume at Copahue on the morning of 23 November 2018. Courtesy of Valentina.

MIROVA (Middle InfraRed Observation of Volcanic Activity) data showed intermittent minor thermal activity at the summit from July through December. There were no thermal anomalies detected by the MODVOLC algorithm for this time period. Twenty cloud-free Sentinel-2 satellite images revealed elevated thermal activity (hotspots) within Agrio crater throughout the reporting period (figure 24).

Figure (see Caption) Figure 24. Thermal activity in the Copahue crater during 2018 seen in Sentinel-2 infrared images. The orange-yellow areas indicate high temperatures within the active Agrio crater. Courtesy of Sentinel Hub Playground.

Geologic Background. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/); Valentina (URL: https://twitter.com/valecaviahue, Twitter: @valecaviahue); Roberto Impaglione (URL: https://twitter.com/robimpaglione, Twitter: @robimpaglione); CultureVolcan (URL: https://twitter.com/CultureVolcan, Twitter: @CultureVolcan).


Kilauea (United States) — January 2019 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Fissure 8 lava flow continues vigorously until 4 August, ocean entry ends in late August, last activity at fissure 8 cone on 5 September 2018

Kilauea's East Rift Zone (ERZ) has been intermittently active for at least two thousand years. Since the current eruptive period began in 1983 there have been open lava lakes and flows from the summit caldera and the East Rift Zone. A marked increase in seismicity and ground deformation at Pu'u 'O'o Cone on the upper East Rift Zone on 30 April 2018, and the subsequent collapse of its crater floor, marked the beginning of the largest lower East Rift Zone eruptive episode in at least 200 years; the ending of this episode in early September 2018 marked the end of 36 years of continuous activity.

During May 2018, lava moving into the Lower East Rift Zone opened 24 fissures along a 6-km-long NE-trending fracture zone, sending lava flows in multiple directions. As lava emerged from the fissures, the lava lake at Halema'uma'u drained and explosions sent ash plumes to several kilometer's altitude (BGVN 43:10). At the end of May, eruptive activity focused on 60-m-high fountains of lava from fissure 8 that created a rapidly moving flow that progressed 13 km in just five days, entering the ocean at Kapoho Bay and destroying over 500 homes. Throughout June vigorous effusion from fissure 8 created a 50-m-tall cone and a massive lava channel that carried lava to a growing 3-km-wide delta area which spread out into the ocean along the coast (BGVN 43:12). At Halema'uma'u crater, regular collapse explosion events were the response of the crater to the subsidence caused by the magma withdrawal on the lower East Rift Zone. The deepest part of the crater had reached 400 m below the caldera floor by late June. The eruptive events of July-September 2018 (figure 424), the last three months of this episode, are described in this report with information provided primarily from the US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) in the form of daily reports, volcanic activity notices, and abundant photo, map, and video data.

Figure (see Caption) Figure 424. Timeline of Activity at Kilauea, 1 July through 14 September 2018. Blue shaded region denotes activity at Halema'uma'u crater at the summit. Green shaded area describes activity on the lower East Rift Zone (LERZ). HST is Hawaii Standard Time. Black summit symbols indicate earthquakes; red LERZ symbols indicate lava fountains (stars), lava flows (triangles) and lava ocean entry.

Summary of activity, July-September 2018. The lava flow emerging from the fissure 8 cone on the Lower East Rift Zone continued unabated throughout July 2018. Overflows from the open channel were common, and often occurred a few hours after summit collapse events. There were multiple active ocean entry areas along the north, central, and southern portions of the coastal flow front of the fissure 8 flow at various times throughout the month. As the flow approached the delta area, lava spread out over the flow field and was no longer flowing on the surface but continued on the interior of the delta; numerous ocean entry points spanned the growing delta. In mid-July, an overflow diverted the channel W of Kapoho Crater, causing a new channel to the S of the delta that destroyed a park and a school, and increased the width of the delta to 6 km. The near-daily collapse events at Halema'uma'u crater continued until 2 August, transforming the geomorphology of the summit caldera.

Lower lava levels at the fissure 8 channel flow were first reported in early August; a reduced output from the cone was reported on 4 August and the lava level in the cone fell below the spillway the next day, shutting off the lava supply to the channel. The lava channel drained and crusted over during the next few days, but lava continued to enter the ocean at a decreasing rate for the rest of the month; the last ocean entry point had ceased by 29 August. A minor burst of spatter from gas jets inside the cone was noted on 20 August. The last activity was a small flow that covered the floor of the fissure 8 cone and created a small spatter cone during 1-5 September. Incandescence at the crater subsided during the next week until only steam activity was reported on the Lower East Rift Zone by the second half of September 2018.

Activity on the Lower East Rift Zone during 1-12 July 2018. The lava flow emerging from the fissure 8 cone on the Lower East Rift Zone continued unabated during July 2018 (figure 425). Overflows from the open channel were common, sending multiple short streams of lava down the built-up flanks of the channel (figure 426). The fissure 8 lava flow was the most significant activity at the Lower East Rift Zone during July 2018, but it was not the only activity observed by HVO scientists. Fissure 22 was also spattering tephra 50-80 m above a small spatter cone and feeding a short lava flow that was moving slowly NE along the edge of earlier flows during 1-11 July (figures 427 and 428). There were multiple active ocean entry areas along the north, central, and southern portions of the coastal flow front of the fissure 8 flow at various times throughout the month.

Figure (see Caption) Figure 425. The lava flow emerging from the fissure 8 cone on Kilauea's Lower East Rift Zone continued unabated on 3 July 2018, as viewed from the early morning HVO helicopter overflight. Recent heavy rains had soaked into the still-warm tephra causing the moisture to rise as steam around the channel. Note house and road in lower right for scale. Courtesy of HVO.
Figure (see Caption) Figure 426. Numerous overflows were visible from Kilauea's LERZ fissure 8 lava channel during the HVO morning overflight on 2 July 2018. They appear as lighter gray to silver areas on the margins of the channel. Note road and Puna Geothermal Venture (PGV) for scale on top. Courtesy of HVO.
Figure (see Caption) Figure 427. Ocean entries were active on the northern and central parts of the ocean entry delta of Kilauea's LERZ fissure 8 flow on 2 July 2018. Flows and overflows were also active along the W side of the delta area. Dark red areas are active flow zones, shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.
Figure (see Caption) Figure 428. This thermal map shows the fissure system and lava flows as of 0600 HST on 2 July 2018. The fountain at fissure 8 remained active, with the lava flow entering the ocean at Kapoho, although the active channel on the surface ended about 0.8 km from the coast. Fissure 22 was also spattering tephra 50-80 m above a small spatter cone and feeding a short lava flow that was moving slowly NE along the edge of earlier flows. The black and white area is the extent of the thermal map. Temperature in the image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.

The lava channel had begun crusting over near the coast late in June, and the lava was streaming from the flow's molten interior into the ocean at many points along its broad front during the first half of July. The crusted-over area was 0.8 km from the coast on 2 July and had increased to 2 km from the coast on 6 July (figure 429). Temporary channel blockages of the flow caused minor overflows north of Kapoho Crater during 4-6 July. Multiple breakouts fed flows on the N and the SW edge of the main `a`a flow. HVO captured images during an overflight on 8 July of the area where the open channel ended and turned into the broad flow area of the delta (figure 430).

Figure (see Caption) Figure 429. This thermal map shows the fissure system and lava flows as of 0600 on 6 July 2018. The fountain at fissure 8 remained active, with the lava flow entering the ocean in several places at Kapoho; the northern delta area was especially active. The crusted over area had increased to 2 km from the coast (compare with figure 428). Small flows were still observed near fissure 22. The black and white area is the extent of the thermal map. Temperature in the image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.
Figure (see Caption) Figure 430. The end of the surface channel in Kilauea's LERZ fissure 8 was near Kapoho Crater on 8 July 2018. Top: The partially filled Kapoho Crater (center) is next to the open lava channel where it makes a 90-degree turn around the crater. Lava flows freely through the channel only to the southern edge of the crater (left side of image). Lava then moves into and through the molten core of the thick 'a'a flow across a broad area. Bottom: Close up view of the "end" of the open lava channel where lava moves beneath the crusted 'a'a flow. Courtesy of HVO.

By 9 July the main lava channel had reorganized and was nearly continuous to the ocean on the S side of the flow, expanding the south margin by several hundred meters (figure 431). Lava was also entering the ocean along a 4-km-long line of small entry points across the delta. Early that afternoon observers reported multiple overflows along both sides of the main lava channel in an area just W of Kapoho Crater; small brushfires were reported along the margins. Another flow lobe farther down the channel was moving NE from the main channel. The channel near Four Corners was mostly crusted over, and plumes from the ocean entry were significantly reduced. The dramatic difference in landscapes on the northern and southern sides of the fissure 8 lava channel was readily apparent during a 10 July overflight (figure 432). With dominant trade winds blowing heat and volcanic gases to the SW, the N side of the lava channel remained verdant, while vegetation on the S side was severely impacted and appeared brown and yellow.

Figure (see Caption) Figure 431. By 9 July 2018 the lower part of Kilauea's LERZ fissure 8 flow had reorganized and was nearly continuous to the ocean on the south side of the flow, expanding the south margin by several hundred meters. Dark red areas denote active flow expansion and shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.
Figure (see Caption) Figure 432. During HVO's morning overflight on 10 July 2018, the dramatic difference in landscapes on the northern and southern sides of Kilauea's LERZ fissure 8 lava channel was readily apparent. With dominant trade winds blowing heat and volcanic gases to the SW, the N side of the lava channel remains verdant, while vegetation on the S side has been severely impacted and appears brown and yellow. The fissure 8 cone is obscured by a cloud of steam (top center), but a small speck of incandescence rises at the center. The width of the channel and levee in the narrowest place at lower left is about 500 m. Note houses and trees for scale. Courtesy of HVO.

A channel blockage just W of Kapoho Crater overnight on 10-11 July sent most of the channel S along the W edge of previous flows on the W side of the crater. By mid-morning this channelized ?a?a flow had advanced to within 0.5 km of the coast at Ahalanui Beach Park. A few houses were also threatened by overflows along the upper channel on 11 July (figure 433). The broad ocean entry area widened as a result and covered nearly 6 km by 12 July (figure 434).

Figure (see Caption) Figure 433. A pahoehoe flow fed by overflows from Kilauea's LERZ fissure 8 lava channel was active and threatening homes along Nohea Street in the Leilani Estates subdivision on 11 July 2018. Courtesy of HVO.
Figure (see Caption) Figure 434. An aerial view to the SW of the ocean entry at Kapoho from Kilauea's LERZ fissure 8 on 11 July 2018 shows Cape Kumukahi (with lighthouse) in the foreground surrounded by lava flows that formed in 1960. The northern edge of the new fissure 8 flow is close to the steam plume closest to the lighthouse. Kapoho Crater in the upper right is surrounded by new lava from fissure 8. See figure 431 for additional location details. Courtesy of HVO.

HVO first mentioned a connection between the lava levels in the upper channel of the fissure 8 flow and the collapse-explosion events at the summit on 12 July. They observed a rise in the lava level shortly after each collapse event at the summit for most of the rest of July. Overnight into 12 July, the diverted channelized ?a?a flow W of Kapoho Crater advanced to the ocean destroying the Kua O Ka La Charter School and Ahalanui Count Beach Park and established a robust ocean entry area (figure 435). Despite no visible surface connection to the fissure 8 channel, lava continued to stream out at several points on the 6-km-wide flow front into the ocean. A small island of lava also appeared offshore of the northernmost part of the ocean entry on 12 July (figure 436).

Figure (see Caption) Figure 435. The channel overflow during 9-10 July from Kilauea's LERZ fissure 8 flow created a new lobe that reached the ocean on 12 July 2018 destroying Ahalanui Park and the nearby charter school. The lava flow was also still entering the ocean at numerous points along the coast. The black and white area is the extent of the thermal map. Temperature in the image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique thermal images collected by a handheld camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.
Figure (see Caption) Figure 436. A small new island of lava from Kilauea's LERZ fissure 8 flow formed on the northernmost part of the ocean entry; it was visible during the morning overflight on 13 July 2018. HVO's field crew noticed the island was effusing lava similar to the lava streaming from the broad flow front along the coastline. The freshest lava in the delta has a silvery sheen and is adjacent to older flows. Courtesy of HVO.

Activity on the LERZ during 13-31 July 2018. As the southern margin of the flow continued to advance slowly south, it reached to within 1 km of the Isaac Hale Park on 14 July and within 750 m on 17 July. An increase in lava supply overnight into 18 July produced several channel overflows threatening homes on Nohea street and also additional overflows downstream on both sides of the channel. The overflows had stalled by mid-morning. South of Kapoho Crater, the surge produced an ?a?a flow that rode over the active southern flow that was still entering the ocean. The southern margin was 500 m from the boat ramp at Isaac Hale Park on 19 July (figure 437).

Figure (see Caption) Figure 437. The southern margin of Kilauea's LERZ fissure 8 flow was 500 m N of Isaac Hale Park on 19 July 2018. Active flow expansion is shown in dark red, shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.

During the HVO morning overflight on 20 July scientists noted that the channel was incandescent along its entire length from the vent to the ocean entry (figure 438, top). The most vigorous ocean entry was located a few hundred meters NE of the southern flow boundary; a few small pahoehoe flows were also entering the ocean on either side of the channel's main entry point (figure 438, bottom). On 23 July there were overflows just NW of Kapoho Crater following a collapse event at the summit the previous evening. During the day, small breakouts along the edge of the lava flow in the Ahalanui area caused the flow to expand westward. The flow margin was about 175 m from the Pohoiki boat ramp in Isaac Hale Park by the end of 24 July, and the active ocean entry was still a few hundred meters to the E of the lava flow margin. The numerous ocean entry points were concentrated along the southern half of the 6-km-long delta (figure 439).

Figure (see Caption) Figure 438. HVO scientists noted that Kilauea's LERZ fissure 8 flow was incandescent all the way from the vent to the ocean the day before these 21 July 2018 images of the flow. Top: Fissure 8, source of the white gas plume in the distance, continued to erupt lava into the channel heading NE from the vent. Near Kapoho Crater (lower left), the channel turned S on the W side of the crater, sending lava toward the coast, where it entered the ocean in the Ahalanui area (bottom image). Channel overflows are visible in the lower right. Bottom: The most vigorous ocean entry of the fissure 8 flow was located a few hundred meters NE of the southern flow margin in the Ahalanui area. Courtesy of HVO.
Figure (see Caption) Figure 439. Kilauea's LERZ fissure 8 flow at 0600 on 24 July 2018. The dominant ocean entry points were on the section of coastline near Ahalanui and Pohoiki. The flow margin was about 175 m from the Pohoiki boat ramp in Isaac Hale Park by the end of 24 July. The black and white area is the extent of the thermal map. Temperature in the image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.

On 26 July, lava movement in the channel appeared sluggish and levels had dropped in the lower part of the channel compared to previous days. Pulses of lava were recorded every few minutes at the fissure 8 vent (figure 440). HVO suggested that overflows on 28 July may have resulted from a channel surge following a summit collapse event in the morning (figures 441 and 442). Lava was actively entering the ocean along a broad 2 km flow front centered near the former Ahalanui Beach Park, but the edge of the flow remained about 175 m from the Pohoiki boat ramp at Isaac Hale park for the rest of the month. There were a few breakouts to the W that were distant from the coast and not directly threatening Pohoiki. A more minor entry was building a pointed delta near the south edge of the flow. At 2202 on 29 July an earthquake on Kilauea's south flank was felt as far north as Hilo by a few people. The M 4.1 (NEIC) earthquake was weaker than recent summit earthquakes but it was felt more widely, possibly due to its greater depth of 7 km (compared with 2 km for summit earthquakes).

Figure (see Caption) Figure 440. Pulses of lava from Kilauea's LERZ fissure 8 vent occurred intermittently every few minutes on 26 July 2018. These photographs, taken over a period of about 4 minutes, showed the changes that occurred during these pulses. Initially, lava within the channel was almost out of sight. A pulse in the system then created a banked lava flow that threw spatter (fragments of molten lava) onto the channel margin. After the bottom photo was taken, the lava level again dropped nearly out of sight. Courtesy of HVO.
Figure (see Caption) Figure 441. Incandescent lava covering the 'a'a flow between Kilauea's LERZ fissure 8 lava channel and Kapoho Crater (lower left) is from an overflow that may have resulted from a channel surge following the morning summit collapse event on 28 July 2018. The active ocean entry can be seen in the far distance (upper left). Courtesy of HVO.
Figure (see Caption) Figure 442. Overflows from Kilauea's LERZ fissure 8 lava channel on 28 July 2018 may have ignited this fire (producing dark brown smoke) on Halekamahina, an older cinder-and-spatter cone to the west of Kapoho Crater. Courtesy of HVO.

Activity at Halema'uma'u during July and August 2018. Periodic collapse explosion events with energy equivalents to a M 5.2 or 5.3 earthquake continued on a near daily basis throughout July at Halema'uma'u, enlarging the crater floor inside the Kilauea caldera and creating large down-dropped blocks and fractures across the caldera (figure 443). Ash-poor plumes occasionally rose a few hundred meters above the caldera floor. Summit seismicity would drop dramatically after each explosion and then gradually increase to 25-35 earthquakes (mostly in the M 2-3 range) prior to the next collapse explosion. The periodicity of the explosion events was consistent until 24 July when a gap of 53 hours occurred until the next event on 26 July, the longest break since early June.

Figure (see Caption) Figure 443. The WorldView-3 satellite acquired this view of Kilauea's summit on 3 July 2018. Despite a few clouds, the area of heaviest fractures in the caldera is clear. Views into the expanding Halema'uma'u crater revealed a pit floored by rubble. The now-evacuated Jaggar Museum and Hawaii Volcano Observatory (HVO) is labelled on the NW caldera rim. Remains of the Crater Rim Drive are visible along the bottom of the image; the overlook parking lot was completely removed by the growing S rim of the crater. Courtesy of HVO.

Images of the caldera on 13 July and 1 August demonstrated the unprecedented magnitude of change that affected Kilauea during the month (figures 444 and 445). The last collapse explosion event, at 1155 HST on 2 August, was reported as a M 5.4 seismic event (figure 446). Seismicity increased after the event as it had after previous events, but after reaching about 30 earthquakes per hour on 4 August, seismicity decreased without a collapse-explosion event occurring. The rate of deformation at the summit as measured by tiltmeter and GPS was also much reduced after 4 August.

Figure (see Caption) Figure 444. USGS scientists acquired this aerial photo of Halema'uma'u and part of the Kilauea caldera floor during a helicopter overflight of the summit on 13 July 2018. In the lower third of the image are the buildings that housed the USGS Hawaiian Volcano Observatory and Hawai'i Volcanoes National Park's Jaggar Museum, the museum parking area, and a section of the Park's Crater Rim Drive. Although recent summit explosions had produced little ash, the gray landscape was a result of multiple thin layers of ash that blanketed the summit area during the ongoing explosions. Courtesy of HVO.
Figure (see Caption) Figure 445. This aerial view of Kilauea's summit taken on 1 August 2018 shows the continued growth of the crater. Compare with the previous image (figure 444) taken a few weeks earlier; a section of Hawai'i Volcanoes National Park's Crater Rim Drive and the road leading to the Kilauea Overlook parking area are visible at lower right. HVO, Jaggar Museum, and the museum parking area are visible at far middle right. On the far rim of the caldera, layers that are downdropped significantly more than on 13 July are clearly exposed. On the caldera rim (upper right) light-colored ash deposits from explosions in May were stirred up by brisk winds, creating a dust cloud dispersing downwind. Courtesy of HVO.
Figure (see Caption) Figure 446. Rockfalls along Kilauea's caldera walls were common during summit collapse events. This image, taken just after the 1155 HST collapse on 2 August 2018, shows dust rising from rockfalls along Uekahuna Bluff. This was the last collapse explosion event at Halema'uma'u during the current eruption.

Activity on the Lower East Rift Zone during August 2018. Activity continued essentially unchanged on the fissure 8 flow during 1-4 August, although there were reports of somewhat lower lava levels in the channel. Multiple overflows were reported late on 2 August, one of which started a small fire near Noni Farms Road. Other overflows were concentrated in the wide lava field W and SSW of Kapoho Crater, also igniting small fires in adjacent vegetation (figure 447). The south edge of the flow did not advance any closer to the boat ramp in Isaac Hale Park (figure 448). The channel was incandescent at its surface to approximately 4.5 km from the vent (figure 449); lava was still flowing farther beneath the crust to the vicinity of Kapoho Crater where it was seeping out of both sides of the channel. The lower lava channel adjacent to Kapoho Crater shifted W about 0.25 km early on 4 August and was feeding lava into the SW sector of the lower flow field.

Figure (see Caption) Figure 447. Overflows formed a pool of lava at the channel bend just west of Kapoho Crater (vegetated cone at left) on 1 and 2 August 2018 as seen in this view toward the SE on 1 August 2018 at Kilauea's LERZ fissure 8 flow. Courtesy of HVO.
Figure (see Caption) Figure 448. During the morning overflight on 2 August 2018, HVO geologists observed the ocean entry laze plume was being blown offshore, allowing this fairly clear view (looking NE) of the Pohoiki boat ramp at Isaac Hale Beach Park (structure, lower left). Incandescent spots of lava can be seen within the flow field beyond the boat ramp. HVO geologists also observed some lava escaping on or near the western flow margin. The southern margin of the flow front was still more than 100 m from the boat ramp. Courtesy of HVO.
Figure (see Caption) Figure 449. Kilauea's LERZ fissure 8 channel was incandescent for about 4.5 km from the vent in the early morning on 2 August 2018. Downstream of the vent, the channel split to form a "braided" section in the lava channel, and the north (right) arm of the braided section appeared to be partially abandoned. Lava was still visible in part of the northern braid, but the lower section was only weakly incandescent. The lava within the channel generally appeared to be at a lower level than in previous days. Courtesy of HVO.

The NE half of the flow's ocean-front was inactive with no evidence of effusion into the ocean by 4 August. Field observations and UAS overflight images indicated a reduced output of lava from fissure 8 during the day on 4 August. During the morning helicopter overflight on 5 August geologists confirmed a significant reduction in lava output from fissure 8 that began the previous day. HVO field geologists observed low levels of fountaining within the fissure 8 spatter cone and largely crusted lava in the spillway and channel system downstream (figure 450). The lava level in the channel near Kapoho Crater had dropped substantially on 5 August. (figure 451).

Figure (see Caption) Figure 450. HVO field geologists observed low levels of fountaining within Kilauea's LERZ fissure 8 spatter cone and largely crusted lava in the spillway and channel system downstream (left) during the morning overflight on 5 August 2018. The inner walls of the cone and lava surface were exposed and a dark crust had formed on the lava with the spillway. Courtesy of HVO.
Figure (see Caption) Figure 451. Incandescent lava remained visible in a section of Kilauea's LERZ fissure 8 channel W of Kapoho Crater (just visible at far left) on 5 August 2018 after a large drop in the flow rate during the previous day. This view is looking S toward the ocean; the laze plume rising from the ocean entry can be seen in the far distance. Courtesy of HVO.

Lava continued to slowly enter the ocean along a broad flow front generally near Pohoiki, but remained about 70 m SE of the boat ramp on 5 August. The next morning's overflight crew saw a weak to moderately active bubbling lava lake within the fissure 8 cone, a weak gas plume, and a completely crusted lava channel. Later in the morning ground crews found the upper channel largely devoid of lava, confirming that the channel was empty to at least the vicinity of Kapoho Crater where a short section of spiny active lava in a channel was present. There were small active breakouts near the coast on the Kapoho Bay and Ahalanui lobes, but the laze plume was greatly diminished. Active lava was close to the Pohoiki boat ramp but had not advanced significantly toward it. A major change in the heat flow recorded by satellite instruments was apparent by the end of the first week in August (figure 452). The MIROVA signal, which had shown a persistent high-intensity thermal signal for several years, recorded an abrupt drop in activity early in May that coincided with the opening of the fissures on the LERZ, and the dropping of the lava lake at Halema'uma'u. The lower levels of heat flow fluctuated from May through early August, and then ended abruptly after the first week of August.

Figure (see Caption) Figure 452. The MIROVA plot of thermal activity at Kilauea changed abruptly after the first week of August 2018 after many years of registering high heat flow from numerous sources at Kilauea. Compare with figure 310 (BGVN 43:03) and figure 290 (BGVN 42:11). Courtesy of MIROVA.

On 7 August the surface of the lava lake was about 5-10 m below the spillway entrance (figure 453) and the upper part of the channel was crusted over (figure 454). There were a diminishing number of small active flow points near the coast on the Kapoho Bay and Ahalanui lobes. By 9 August the overflight crew observed a crusted lava pond deep inside the steaming cone at a level significantly below that seen on 7 August. Up-rift of fissure 8, fissures 9, 10, and 24, and down-rift fissures 13, 23, 3, 21 and 7, continued to steam, but no new activity was observed. Lava was streaming at several points along the Kapoho Bay and Ahalanui coastline, causing wispy laze plumes on 10 August, and only minor areas of incandescence were visible in the lava pond inside the fissure 8 cone (figure 455). The next day the overflight crew noted two small ponds of lava inside the cone; one was crusted over and stagnant, and the other was incandescent and sluggishly convecting. A gas plumed billowed up from fissure 8 and low-level steaming was intermittent from a few of the otherwise inactive fissures.

Figure (see Caption) Figure 453. On 7 August 2018 Hawaii County's Civil Air Patrol got a closer view of Kilauea's LERZ fissure 8 cone and the small pond of lava within the vent. The lava was below the level of the spillway that fed the fissure 8 channel from May 27 to August 4, 2018. Courtesy of HVO.
Figure (see Caption) Figure 454. Lava in Kilauea's LERZ fissure 8 channel near the vent was crusted over by 7 August 2018. Fissure 8 and other inactive fissures were steaming in the background. Courtesy of HVO.
Figure (see Caption) Figure 455. The Unmanned Aircraft Systems (UAS) team flew over Kilauea's LERZ fissure 8 on 10 August 2018 and provided this aerial view into the cinder cone. The pond of lava within the vent had receded significantly from a few days earlier (see figure 453), and was about 40 m below the highest point on the cone's rim. Courtesy of HVO.

By 12 August the only incandescent lava visible on the flow field was that entering the ocean between Kapoho Bay and the Ahalanui area. Fresh black sand, created as molten lava is chilled and shattered by the surf, was being transported SW by longshore currents and accumulating in the Pohoiki small boat harbor (figure 456). A sandbar blocked the entrance to the harbor the following day. The westernmost ocean entry of lava was about 1 km from the harbor on 13 August.

Figure (see Caption) Figure 456. The Pohoiki boat ramp at Isaac Hale Park at Kilauea on 11 August 2018 was blocked in by a black sand bar forming from the longshore currents carrying material SW from the edge of the fissure 8 flow delta even though the southern-most flow margin had not advanced significantly toward the Pohoiki boat ramp. Geologists observed several small lava streams trickling into the sea along the southern portion of the lava delta, producing weak laze plumes. Courtesy of HVO.

By 14 August only a small, crusted over pond of lava deep inside the fissure 8 cone and a few scattered ocean entries were active; there had been no new lava actively flowing in the lower East Rift Zone since 6 August. No collapse events had occurred at the summit since 2 August. Earthquake and deformation data showed no net changes suggesting movement of subsurface magma or pressurization. Sulfur dioxide emission rates at both the summit and LERZ were drastically reduced; the combined rate was lower than at any time since late 2007. As a result of the reduced activity, HVO lowered the Alert Level for ground-based hazards from WARNING to WATCH on 17 August. By 18 August, the only incandescence visible was at the coast near Ahalanui, where there were a few ocean entries and minor laze plumes (figure 457).

Figure (see Caption) Figure 457. Lava was still entering the ocean at scattered entry points, mainly near Ahalanui (shown here), but also at Kapoho from Kilauea's LERZ fissure 8 flow on 17 August 2018 even though no new lava had entered the system since 6 August. Courtesy of HVO.

Gas jets were throwing spatter, fragments of glassy lava, from small incandescent areas deep within the fissure 8 cone on 20 August (figure 458). The last day that the small lava pond deep within the fissure 8 cone was visible during an overflight was on 25 August; a few ocean entries were still active. A single small lava stream from the Kapoho Bay lobe was the only moving lava noted during an HVO overflight on 27 August (figure 459). Two days later, on 29 August, no lava was entering the ocean.

Figure (see Caption) Figure 458. Gas jets were throwing spatter (fragments of glassy lava) from small incandescent areas deep within Kilauea's LERZ fissure 8 cone on 20 August 2018. The spatter is the light gray material around the two incandescent points at the center. Courtesy of HVO.
Figure (see Caption) Figure 459. Only one small ocean entry near Ahalanui was visible on 27 August 2018 at Kilauea's LERZ fissure 8 flow delta. Courtesy of HVO.

The fissure 8 lava flow entering the ocean had built a lava delta over 354 hectares (875 acres) in size by the end of August 2018 (figure 460). A sand bar, comprised of black sand and lava fragments carried by longshore currents from the lava delta, completely blocked the boat ramp at Isaac Hale Beach Park on 31 August 2018 (figure 461).

Figure (see Caption) Figure 460. Kilauea's LERZ fissure 8 lava flows had built a lava delta over 354 hectares (875 acres) in size, but no active ocean entries were observed by HVO geologists on 30 August 2018. View is to the SW. Courtesy of HVO.
Figure (see Caption) Figure 461. A sand bar, comprised of black sand and lava fragments carried by longshore currents from Kilauea's LERZ fissure 8 lava delta, blocked access to the boat ramp at Isaac Hale Beach Park on 31 August 2018. The white cement ramp leads down to a small pool of brackish water surrounded by black sand. The S edge of the ocean-entry delta is at lower left. Courtesy of HVO.

Activity during September 2018. A brief resurgence of minor activity during the first few days of September was the last observed from LERZ fissure 8. Incandescence was noted in the fissure 8 cone on 1 September. There was a persistent spot of spattering, and lava slowly covered the 15 x 65 m crater floor by evening (figure 462). Webcam views showed weak incandescence occasionally reflected on the eastern spillway wall from the crater overnight, suggesting that the lava in the crater remained active. A UAS oblique image the next afternoon showed that the new lava was mostly confined to the crater floor within the cone, although a small amount extended a short distance into the spillway (figure 463). Weak lava activity continued inside the fissure 8 cone for several days; lava filled the small footprint-shaped crater inside the cone as sluggish pahoehoe flows crept across the crater floor but did not flow down the spillway. A small spatter cone ejecting material every few seconds was noted on the floor of the crater on 4 September; observations the next day showed that it had reached an estimated height of around 3-4 m (figure 464). Only a small amount of incandescence was visible overnight on 5-6 September at fissure 8.

Figure (see Caption) Figure 462. An Unmanned Aircraft Systems overflight of Kilauea's LERZ fissure 8 on 1 September 2018 showed incandescence within the cinder cone, with reports that lava had covered the 15 x 65 m foot-print shaped crater floor by evening. Courtesy of HVO.
Figure (see Caption) Figure 463. This 2 September 2018 UAS oblique image of Kilauea's LERZ fissure 8 cone showed that the new lava was mostly confined to the crater floor within the cone, although a small amount extended a short distance into the spillway. HVO geologists noted that the lava activity was at a low level by the evening, with only minimal (if any) incandescence emanating from the cone. Gas emissions from the vent were nearly nonexistent. Courtesy of HVO.
Figure (see Caption) Figure 464. A close-up view of the small cone that formed on the floor of the crater within Kilauea's LERZ fissure 8 on 5 September 2018. Bits of spatter emitted from the cone every few seconds had built it up to an estimated height of around 3-4 m. See video of spatter on HVO website. Courtesy of HVO.

 Pu'u O'o crater experienced a series of small collapses on 8 September. These produced episodes of visible brown plumes throughout the day and generated small tilt offsets and seismic energy recorded by nearby geophysical instruments. The collapses had no discernable effect on other parts of the rift and continued for several days at a decreasing frequency. Minor amounts of incandescence and fuming continued to be observed on 9 September at the fissure 8 cone. A small collapse pit formed in the cone on 10 September exposing hot material underneath and producing a short-lived increase in incandescence. Minor fuming was visible the next day from the small spatter cone. Incandescence at the collapse pit decreased over the next few days, but a glowing spot just west of the pit appeared on 11 September and grew slowly for a few days before diminishing. HVO interpreted it to be a layer of incandescence exposed in the slowly subsiding lava surface within the fissure 8 cone. Minimal incandescence was visible overnight on 14-15 September. After this, only minor fuming was visible during the day; incandescence was no longer observed for the remainder of the month.

HVO determined that the 2018 Lower East Rift Zone eruptive episode ended on 5 September 2018, bringing with it an end to the lava lake at Halema'uma'u crater and the eruptive activity that had been continuous at either Pu'u O'o or Halema'uma'u since 3 January 1983; a period of more than 36 years. Satellite imagery from early September 2018 demonstrated some of the impact of this last eruptive episode on the region around Kilauea's lower East Rift Zone since the first fissure opened at the beginning of May 2018 (figures 465 and 466).

Figure (see Caption) Figure 465. This comparison shows satellite images of Leilani Estates subdivision before (2014) and after the LERZ eruptive episode of May-September 2018 at Kilauea. The image on the right, collected in early September 2018, shows that the eastern portion of the subdivision was covered by new lava. The fissure 8 lava channel runs NE from the fissure 8 cone at the start of the channel. Note also the brown areas of dead vegetation S of the lava flow. Highway 130 runs N-S along the left side of the images. Courtesy of HVO.
Figure (see Caption) Figure 466. This comparison of satellite imagery from before (2014) and after the May-September 2018 LERZ eruptive episode at Kilauea shows the area of Kapoho before and after the event. Kapoho Crater is in the left portion of the image. Lava filled much of the crater, including the small nested crater that contained Green Lake. The Kapoho Beach Lots subdivision is on the right side of the image, north of Kapoho Bay, and was completely covered by the fissure 8 lava flow. Vacationland Hawai'i, in the lower right corner of the image, was also completely covered, along with the adjacent tide pools. Kapoho Farm Lots, near the center of the image, is also beneath the flow. Courtesy of HVO.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: http://hvo.wr.usgs.gov/); 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/).


Piton de la Fournaise (France) — December 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)


Eruption from 15 September to 1 November produced a lava flow to the E

Piton de la Fournaise, located in the SE part of La Réunion Island in the Indian Ocean, has been producing frequent effusive basaltic eruptions on average twice a year since 1998. The activity is characterized by lava fountains and lava flows, and occasional explosive eruptions that shower blocks over the summit area and produce ash plumes. Almost all of the recent activity has occurred within the Enclos Fouqué caldera, with recent eruptions in 1977, 1986, and 1998 at vents outside of the caldera. The most recent eruptive episode lasted 18 hours on 13 July 2018. This report summarizes activity during September-November 2018 and is based on reports by Observatoire Volcanologique du Piton de la Fournaise (OVPF) and satellite data.

After deformation had ceased in early August, inflation resumed in the beginning of September (figure 145) accompanied by low-level seismicity. From 1 to 12 September CO2 concentrations at the summit had decreased, followed by an increase during 12-20 September. A seismic crisis was reported on 0145 on 15 September that included 995 shallow (less than 2 km depth) volcano-tectonic earthquakes recorded in less than four hours. This was accompanied by rapid deformation of up to 24 cm.

Figure (see Caption) Figure 145. Horizontal displacement at Piton de la Fournaise recorded in October 2018 at the OVPF permanent GPS stations located inside the caldera. The source for the deformation was located at a depth of 1-1.5 km below the Dolomieu crater. Courtesy of and copyright by OVPF/IPGP.

The eruption began at 0435 on 15 September with a fissure opening and erupting lava on the SW flank near Rivals crater. This new fissure was about 300 m downstream, and was a continuation of, the 27 April-1 June 2018 fissure. Volcanic tremor rapidly and steadily declined once the eruption began, which is commonly observed during eruptions of Piton de la Fournaise. An observation flight that day showed five fissures with lava fountains reaching 30 m high in the center of the fissure system (figure 146). By 1100 two main lava flows had merged further downflow and traveled 2 km from the fissures. During the first hours of the eruption the estimated time-averaged discharge rate was 22.7 and 44.7 m3/s.

Figure (see Caption) Figure 146. An overflight at Piton de la Fournaise at 1100 on 15 September 2018 showed that five fissures had opened and two main lava flows had merged and extended to 2 km. The lava fountain in the center of the fissures reached 30 m high. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 15 Septembre 2018 à 16h45).

A survey on the 15th recorded multiple lobes at the end of the lava flow and flow rates of 1-5 m3/s (figures 147 and 148). Three vents remained active on 16 September and a spatter cone was being constructed around them. The lava effusion rate was measured at 2.5-7 m3/s. SO2 levels were elevated and the resulting gas plume was dispersed towards the W. On the 17th the lava flow was still high on the flank and moving E.

Figure (see Caption) Figure 147. The lava flow of the 15 September 2018 eruption of Piton de la Fournaise as seen on 17 September. The top images are photographs of the active fissure and the location of the lava flow as it progresses towards the SE, and the bottom images are thermal infrared images of the lava flow. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 17 Septembre 2018 à 17h30).
Figure (see Caption) Figure 148. The active vent at Piton de la Fournaise producing a lava flow with flow rates of 1-5 m3/s on 15 September 2018. The opening of the vent is towards the south and a degassing plume is visible. Courtesy of and copyright by OVPF/IPGP.

By 18 September a cone had developed and was open to the south, producing lava fountaining and feeding the lava flow (figure 149). The lava flow had extended to 2.8 km from the vent, with the active flow front about 500 m from the southern wall of the caldera. The flows advanced several hundred meters by the 21st and the height of the cone was 30 m on the eastern side where a near-vertical wall had formed (figure 150). The cone contained three active lava fountains.

Figure (see Caption) Figure 149. A spatter cone being built around the new vent on Piton de la Fournaise on 18 September 2018 at 1230 local time. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 18 Septembre 2018 à 17h00).
Figure (see Caption) Figure 150. The active vent on Piton de la Fournaise with spattering activity on 21 September 2018 at 1615. The wall of the cone on the left of the photograph is nearly vertical and was 30 m high. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 21 Septembre 2018 à 20h00).

Fallout of Pele's hair was reported in the Grand Coude area on 22 September. The cone remained open to the south and a deep channel had formed with lava tubes observed close to the cone (figure 151). Three lava fountains continued to feed the lava flow towards the S, then the SE, with a flow rate of 1-3 m3/s.

Figure (see Caption) Figure 151. The eruption fissure at Piton de la Fournaise on 22 September at 1100 local time. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 22 Septembre 2018 à 17h15).

By 26 September the fissure system had evolved into a single cone and the opening towards the south had closed, leaving a circular vent and a lava lake (figure 152). Observations on the 26th showed that lava tubes were developing and feeding outbreak flows 150-300 m away from the cone. During 24-30 September the surface lava flow rate varied from 0.5 to 5.3 m/s, but this was expected to be higher in the lava tubes. By the 27th the majority of the lava was feeding from within the vent area into lava tubes that continued to feed breakout flows several hundred meters from the cone. On the 30th a small lava flow was also visible at the foot of the cone and spattering was seen low above the cone (figure 153).

Figure (see Caption) Figure 152. A view of the active cone and lava flow on Piton de la Fournaise on 25 September 2018. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 26 Septembre 2018 à 17h00).
Figure (see Caption) Figure 153. An explosion producing spatter that is added to the new cone on Piton de la Fournaise. Photographs taken around 1100 on 29 September 2018. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 30 Septmeber 2018 à 15h00).

The surface lava flow rate ranged from less than 1 and up to 4 m3/s on 1-2 October, with the majority of the activity still taking place in lava tubes with some small breakout flows (figure 154). There was a reduction in surface activity on 2-3 October along with a change from continuous degassing to the emission of discrete gas plumes ("gas pistons") that were accompanied by a sharp increase in tremor (figure 155). Observations on the 4th noted that spattering at the vent was minor and rare. No breakouts were observed.

Figure (see Caption) Figure 154. The surface activity of Piton de la Fournaise at 1030 on 2 October 2018. The activity was focused at a single vent and a cone had developed on top of the initial fissure. A white degassing plume and incandescent lava are seen at the vent, but the majority of activity is below the surface in lava tubes. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 3 Octobre 2018 à 14h00).
Figure (see Caption) Figure 155. Thermal infrared imaging of the Piton de la Fournaise eruptive site and active lava flow field taken from Piton Bert at 1050 on 8 October 2018.

Limited activity continued from the 5 to 7 October surface activity remained low, with minor spattering and few breakouts. Lava continued to flow within the lava tubes and degassing was visible at the surface above them. From 30 September to 8 October the lava had traveled 1.8 km E within lava tubes and emerged as a breakout along the northern flow (figure 156). The south and central flow-fronts had not advanced during this time.

Figure (see Caption) Figure 156. The progression of the Piton de la Fournaise lava flow from 30 September (red) to 8 October 2018 (blue) as determined by InSAR satellite data. There are three main lobes, with the activity focused at the northern lobe during this time. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 8 Octobre 2018 à 16h00).

On 14 October no lava channels were visible on the surface and only small breakouts were observed (figure 157). Activity continued in lava tubes and strong degassing persisted from both the vent and main lava tubes (figure 158). On the 18th OVPF/IPGP reported continued strong degassing and a small lava channel that had formed out to a few tens of meters from the cone (figures 159 and 160).

Figure (see Caption) Figure 157. OVPF sampling a lava breakout on Piton de la Fournaise 600 m from the lava flow front at 1015 on 14 October 2018. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 14 Octobre 2018 à 13h00).
Figure (see Caption) Figure 158. The Piton de la Fournaise eruption site at 0945 on 14 October 2018. At this point most of the activity is confined to lava tubes, with the main lava tube marked by degassing moving away from the degassing vent to the left of the photograph. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 14 Octobre 2018 à 13h00).
Figure (see Caption) Figure 159. A white gas plume at the active vent of Piton de la Fournaise on 18 October 2018. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 18 Octobre 2018 à 17h00).
Figure (see Caption) Figure 160. The eruptive vent and active lava flow on Piton de la Fournaise at 1130 on 18 October 2018. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 18 Octobre 2018 à 17h00).

By 25 October the lava flow rate was still low with no further extension of the flow boundary, SO2 emission from the vent were low (close to or below the detection limit), CO2 levels were decreasing, and the intensity of the tremor had stabilized at a very low level for about 24 hours (figure 161). At this point the lava field was essentially composed of lava tubes with a maximum recorded surface temperature (maximum integrated pixel temperature) of 71°C (figure 162). This low level of activity continued during the 26-28th with a small amount of surface lava activity about 1 km from the vent. Over 29-31 October the surface activity was extremely low with no fresh lava observed and only degassing at the vent. The eruption was declared over at 0400 on 1 November after 47 days of activity.

Figure (see Caption) Figure 161. Plot of Real-time Seismic-Amplitude Measurement (RSAM), an indicator of the volcanic tremor and intensity of the Piton de la Fournaise eruption, from 15 September to 25 October 2018. The increase in RSAM beginning on 3 October was due to a change in degassing regime due to the gradual closure of the eruptive vent as the cone grew. The RSAM values stabilized after 24 October; the eruption ended on 1 November. Courtesy of OVPF/IPGP (Bulletin d'activité du samedi 4 Octobre 2018 à 16h30).
Figure (see Caption) Figure 162. An ASTER infrared satellite image of Piton de la Fournaise showing the lava flow in the SE caldera area on 25 October 2018. At this time, the lava field is essentially composed of lava tubes and it has a maximum surface temperature of 71°C. Cooler temperatures are darker and hotter temperatures are shown as white. Courtesy of OVPF/IPGP.

Thermal observations during the September-November eruption showed the evolution of the lava flow and the reduction in surface temperatures when the activity was dominated by lava tubes (figure 163). The sharp increase in thermal anomalies detected by the MIROVA algorithm showed the onset of lava effusion, and the anomalies tapered off as the flow field cooled down (figure 164). The estimated volume of lava produced from 15 September to 17 October was 9-19 million m3, but this is lower than the actual erupted volume due to the lava tube activity. There were 459 MODVOLC thermal alerts from 15 September to 25 October.

Figure (see Caption) Figure 163. Infrared Sentinel-2 images showing the progression of the active areas of the Piton de la Fournaise lava flow (bright yellow-orange) during September and October 2018. Images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 164. The MIROVA plot of thermal energy from Piton de la Fournaise shows three eruptive episodes in 2018: 27 April-1 June, a one day event on 13 July, and 15 September-1 November. Thermal signatures continue beyond the eruption dates as the lava flows cool. Courtesy of MIROVA.

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, 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; Twitter: https://twitter.com/ObsFournaise); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Veniaminof (United States) — January 2019 Citation iconCite this Report

Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)


Eruption with lava flows and ash plumes during September-December 2018

The most recent eruptive period at Veniaminof began in September 2018 with seismic activity followed by ash emissions and lava flows continuing through mid-December 2018, the end of this reporting period (figure 25). An intracaldera cone has been the source of historic volcanic activity in the last 200 years and more recent activity last reported in June 2013 (BGVN 42:02). Veniaminof is closely monitored by the Alaska Volcanic Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC), and is also monitored by a Federal Aviation Administration (FAA) web camera in the town of Perryville, 35 km E.

Figure (see Caption) Figure 25. View of Veniaminof to the W with a diffuse ash plume at 1517 local time on 5 September 2018. Photo by Zachary Finley (color adjusted from original); courtesy of USGS/AVO.

The most recent Strombolian-type eruptive cycle commenced with increased seismic activity on 2 September 2018. Low-level ash that rose 3 km and pulsatory low-altitude ash emissions were observed in FAA webcam images on 4-6 September. Ash deposits extended onto the snowfield at and below the summit to the SSW and SE, forming a "v" shape downslope from the summit. On 7 September a thermal feature was detected, suggesting lava fountaining at the summit, which was later confirmed by satellite data showing a S-flank lava flow about 800 m long on 9-11 September (figure 26). FAA webcam images on 26 September showed lava fountains issuing from a second vent 75 m N of the first, producing additional lava flows on the S flank (figures 27 and 28). Minor ash emissions associated with lava fountaining possibly rose as high as 4.5 km and quickly dispersed.

Figure (see Caption) Figure 26. Geologic sketch map of lava flows and features on the intracaldera cone of Veniaminof as of 11 September 2018. DigitalGlobe WorldView-3 image (left) acquired with Digital Globe NextView License. Image by Chris Waythomas; courtesy of USGS/AVO.
Figure (see Caption) Figure 27. Veniaminof eruption on the evening of 18 September 2018. Photo by Pearl Gransbury; courtesy USGS/AVO.
Figure (see Caption) Figure 28. Veniaminof in eruption on 26 September 2018. A lava flow is visible on the S flank of the volcano with steaming at the base. Photo by Jesse Lopez (color adjusted from original); courtesy of USGS/AVO.

The lava flow had traveled 1 km down the S flank of the summit cone by 1 October. Satellite imagery from 6 October showed three lobes of lava flows and a plume over a thin tephra deposit. By 25 October the lava flow had traveled as far as 1.2 km (figures 29 and 30). Fractures in the ice sheet adjacent to the lava flow field continued to grow due to meltwater flowing beneath. Additionally, a persistent and robust steam plume which contained sulfur dioxide was visible from the FAA webcam on 18 October.

Figure (see Caption) Figure 29. False color ESA Sentinel-2 image of Veniaminof on 6 October 2018 showing lava effusion and a plume with a thin tephra deposit beneath to the N. The flow is ~1 km in length with the most active front on the E, which has a SWIR (short wave infrared) anomaly extending to the flow front. A branch in the channel feeding the western lobes appears to be active as well, but without any SWIR anomaly near the flow front, suggesting that this western branch is less active. The eastern flow front is producing the strongest steam plume. Prepared by Hannah Dietterich with ESA Sentinel-2 imagery; courtesy of USGS/AVO.
Figure (see Caption) Figure 30. Sentinel-2 satellite image of Veniaminof acquired 5 December 2018. Image shows three lava lobes with relative ages from oldest (1) to youngest (3). AVO became aware of flow 3 on 29 November 2018. It is uncertain when this flow first formed because the volcano had been obscured by clouds earlier. Prepared by Chris Waythomas; courtesy of USGS/AVO.

Ash emissions significantly increased overnight on 20-21 November, prompting AVO to raise the Aviation Color Code (ACC) to Red and the Alert Level to "Warning" (the highest levels on a four-level scale). The ash emissions rose to below 4.6 km and drifted more than 240 km SE. On 21 November observations and FAA webcam images indicated continuous ash emissions through most of the day as ash plumes drifted SE, extending as far as 400 km (figure 31). A short eruptive pulse was recorded during 1526-1726, and subsequent ash plumes rose to below 3 km with low-altitude ash emissions drifting 100 km S on 22 November (figure 32). Decreased ash emissions prompted AVO to lower the ACC and Alert Level to Orange and "Watch", respectively. However, lava effusion was persistent through 27 November.

Figure (see Caption) Figure 31. Plume rising from Veniaminof on 9 November 2018. View is to the west. Ash is visible at the summit and steam is rising from the S-flank lava flow. Photo by Zachary Finley (color adjusted from original); courtesy of USGS/AVO.
Figure (see Caption) Figure 32. Annotated satellite image of the Veniaminof eruption taken by Sentinel-2 on 22 November 2018. The image shows an eruptive plume above the active cone within the caldera, as well as a broad tephra deposit to the SE on snow extending to Perryville. Image courtesy of USGS/AVO (ESA/Copernicus; Sentinel-2 image visualized in EOS LandViewer).

During 27-28 November acoustic waves were recorded by regional infrasound sensors. A continuous low-amplitude tremor was recorded until the network went offline following a M 7 earthquake in Anchorage on 30 November. On 6 December seismicity changed from nearly continuous low-level volcanic tremor to intermittent small low-frequency events and short bursts of tremors, possibly indicating that lava effusion had slowed or stopped. Variable seismicity continued through 12 December, though there was no visual confirmation of lava effusion.

Minor ashfall was recorded in Perryville (35 km E) on 25 October and 22 November 2018. Elevated surface temperatures and thermal anomalies were identified in satellite data on 7, 12-26 September, 2-9 and 24-30 October, 7-22 November, and 4-5 December. Nighttime incandescence was visible from the FAA webcam at various times during this reporting period (figure 27). Following 22 November, the ACC remained at Orange and the Volcano Alert Level remained at "Watch."

The MIROVA thermal anomalies detected during this period were reported as having moderate to high radiative power (figure 33). Numerous thermal anomalies identified using the MODVOLC algorithm were also detected during this period, and showed the S-flank lava flows (figure 34).

Figure (see Caption) Figure 33. Plot showing the log radiative power of thermal anomalies at Veniaminof identified using MODIS data by the MIROVA system for the year ending on 28 February 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 34. Map of thermal alert pixels at Veniaminof from the MODVOLC Thermal Alert System during 7 September-24 December 2018 (UTC). Courtesy of HIGP - MODVOLC Thermal Alert System.

Geologic Background. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

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/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845 USA (URL: http://vaac.arh.noaa.gov/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Poas (Costa Rica) — January 2019 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Frequent changes at the crater lake throughout 2018

After an eruption in April 2017, the hot acidic lake of Poás volcano has been in a state of frequent change, with a fluctuating or absent crater lake and other crater changes. During 2018 low-level activity was dominated by hydrothermal vents and degassing. The crater lake was variable, with changes in water level and complete drying of the lake several times. Seismicity was variable with some periods of increased seismicity, deformation was variable but slight, and gas levels fluctuated through the year (figure 120).

Figure (see Caption) Figure 120. Typical situation in the Poás crater and gas data from 2018. Left: The bottom of the dry crater in March 2018 (top) and hydrothermal activity at the bottom of the crater in May 2018 (bottom). Right: Time series graphs showing the maximum concentration of SO2, ratio of SO2/CO2, and the ratio of H2S/SO2 measured at the Poás volcano by the permanent MultiGAS station. The variations are associated with the presence of the lake and with seismicity. Courtesy of OVSICORI-UNA (2018 annual bulletin).

Hydrothermal activity took place during January, with associated low-level gas emissions, and seismicity that reduced later in the month. At the beginning of January the crater lake was absent. After an increase in hydrothermal activity, the lake returned between 18-20 January (figure 121). The lake was measured to be 54°C on 22 January (on the eastern edge) and had a milky blue color with abundant degassing. Temperatures at actively degassing vents reached 97°C. Fumaroles with abundant yellow sulfur deposits were measured to be 160°C (figure 122).

Figure (see Caption) Figure 121. Changes to the Poás crater lake from January through March 2018. The level of water in the crater varies through time and the lake drained in January and March. Images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 122. Active fumaroles within the Poás crater, east of the lake. Yellow sulfur deposits and active degassing are visible. The fumaroles had a temperature of 160°C on 22 January 2018 when this photograph was taken. Courtesy of OVSICORI-UNA (22 January 2018 field report).

During February, activity remained low with fluctuating levels of CO2, SO2, and seismicity; the level of the lake also fluctuated. Activity remained shallow and related to the hydrothermal system with no magmatic activity. During March the seismicity decreased, coinciding with the disappearance of the crater lake during the March-May dry season. During April there was no change observed at the crater, and gas and seismicity continued to fluctuate within normal levels. Background activity and normal fluctuations continued through May until a phreatic (steam) eruption occurred on 25 May, producing a small gray plume and a larger white steam-and-gas plume (figure 123).

Figure (see Caption) Figure 123. A phreatic (steam) explosion on 25 May 2018 at the active Poás crater. Courtesy of OVSICORI-UNA (20 December 2018 report).

In June there was an increase in activity on the crater floor with increased submarine degassing and an increase in the lake water level. A high flow of SO2 (approximately 500 tons per day) was measured on 22 June. The measured level of SO2 was higher on 27 June, at 1,500 tons per day.

Gas emissions, deformation, and seismicity continued with fluctuations through July and August, with a decrease in SO2 around 30 July. Underwater fumaroles continued to be active. A milky-blue crater lake was present throughout this time (figure 124). During September, seismicity was described as highly variable and the crater lake was present (figure 125). Increased seismicity around 8 October coincided with slight inflation at the surface with an increase in activity through to 16 October. Gas emissions remained variable throughout September and October. A slight increase in seismicity occurred in early November and declined again by 19 November, with all other activity variable and within normal levels.

Figure (see Caption) Figure 124. The Caliente crater at Poás with a blue crater lake on 28 August 2018. Courtesy of Costa Rica Gobierno del Bicentenario.
Figure (see Caption) Figure 125. The partially-flooded Poás crater with a blue 38°C lake on 14 September 2018. The black arrow points to convection in the water from a flooded vent, with the insert photo showing a vent on the dry crater floor on 4 September 2017. Courtesy of OVSICORI-UNA (14 September 2018 report).

During December phreatic activity was observed at hydrothermal vents on the 19th (four events) and 20th (three events) that ejected water-saturated material up to 30 m above the vent accompanied by strong degassing and steam plumes. On 20 December it was observed that the lake level had dropped by 1 m and the lake was divided into two bodies of water, Boca A and Boca C. There were also changes in the crater lake color. Starting at the beginning of the month, the lake progressively changed from blue to green, especially visible on 8 December (figures 126, 127, and 128).

Figure (see Caption) Figure 126. Photos of the Poás crater lake showing the nearly-dry lakebed on 31 May, a blue lake on 7 July and 1 August, and a green lake on 6 December 2018. The change in the color of the water is due to the chemical composition of the lake including silica, iron, and sulfur, reflecting different wavelengths of light. Courtesy of OVSICORI-UNA.
Figure (see Caption) Figure 127. A view of the green crater lake with reduced water levels at Poás on 13 December 2018. Photo by Federico Chavarría-Kopper courtesy of OVSICORI-UNA.
Figure (see Caption) Figure 128. The changing crater lake of Poás volcano in December 2018. In one month the crater had a turquoise lake, a green lake, and was dry with no lake. Images courtesy of Sentinel Hub Playground.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Costa Rica Gobierno del Bicentenario, Official Website - Presidency of the Republic of Costa Rica, Zapote, San José, Costa Rica (URL: https://presidencia.go.cr/comunicados/2018/08/29-de-agosto-presidente-alvarado-dara-banderazo-de-reapertura-del-volcan-poas/).


Nevados de Chillan (Chile) — December 2018 Citation iconCite this Report

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


Dome growth and destruction with several explosive events, June-November 2018

Nevados de Chillán is a complex of late-Pleistocene to Holocene stratovolcanoes in the Chilean Central Andes. An eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater (Nicanor) on the E flank of the Nuevo crater, which lies on the NW flank of the cone of the large stratovolcano referred to as Volcán Viejo. Strombolian explosions and ash emissions continued throughout 2016 and 2017. The presence of a lava dome within the Nicanor crater was confirmed in early January 2018; it continued to grow through May 2018. This report covers continuing activity from June-November 2018 when growth and destruction of the dome alternated in a series of explosive events. Information for this report is provided primarily by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Activity at the Nevados de Chillán volcanic complex from June-November 2018 consisted of continued steam-and-gas emissions and periodic explosions with ash plumes and incandescent ejecta; these caused frequent changes to the size and shape of the Gil-Cruz dome within the Nicanor crater. Incandescent material as far as 300 m down the flank was seen in nighttime and thermal webcam images on multiple occasions. Larger explosive events during 13-15 July, 7-8 August, 11-12 September, 13 October, and 7 November produced significant ash plumes that rose a few kilometers above the summit, covered much of the area around the crater with fresh ash and blocks as large as a meter in diameter, and caused noticeable changes to the size and shape of the dome. A 400-m-long pyroclastic flow traveled down the E flank on 12 September 2018. The highest ash plume, on 7 November, rose almost 4 km above the summit and drifted SE.

Intermittent seismic and effusive activity continued during June 2018. Seismicity consisted of long-period earthquakes (LP) and tremor episodes (TR) related to the growth of the viscous lava dome located in the Nicanor crater, and occasional volcano-tectonic (VT) seismic events. Gray emissions and dark ash covering the snow were reported several times during the month. The dome was visible on clear days from the webcam located in Portezuelo (70 km NW); the thermal camera there showed intermittent evidence of emissions as well, usually as nighttime incandescence and ejecta scattered around the crater. Incandescent material traveled 300 m down the slope on 22 June. The Buenos Aires VAAC reported a brief emission on 23 June that rose to 4.6 km altitude and drifted NE before dissipating. It was accompanied briefly by a hotspot detected in thermal imagery.

Low-altitude steam and gas plumes were visible throughout July 2018 with periodic nighttime incandescence and ejecta blocks occasionally visible around the crater. Three explosions on 13, 14, and 15 July produced seismic events and significant ejecta, and resulted in partial destruction of the dome (figure 26). The event on 13 July was recorded as a M 3.7 located 430 m below the summit. During the night of 13-14 July images showed incandescence and ejecta on the NE flank near the crater ranging from centimeter to meter in size. The thermal webcam measured temperatures around 300?C. The second explosion on 14 July was recorded as a M 3.9 event located 1.4 km below the summit; webcam images in clear weather the following afternoon showed the extent of the new material on the NNE flank (figure 27). The third explosion in the early morning of 15 July was measured as a M 3.8 event and produced an incandescent column 340 m high. Additional ejecta on the NNE slope was visible in the webcam that afternoon. The Buenos Aires VAAC reported a pulse of ash moving ESE on 15 July at 6.4 km altitude. A video taken by SERNAGEOMIN during an overflight on 16 July showed ejecta around the flanks and steam rising from the partly destroyed dome. Intermittent, low-altitude steam-and-gas emissions continued for the rest of the month; light gray emissions were reported from 26 July through the end of the month.

Figure (see Caption) Figure 26. Images of the Gil-Cruz dome inside the Nicanor crater at Nevados de Chillán show changes in the character of the dome between 4 April and 16 July 2018 after a series of explosions on 13, 14, and 15 July 2018. The arrows show the main area covered by incandescent ejecta during the explosions. Left image courtesy of Nicolás Luengo V. and used with permission, right image taken during a SERNAGEOMIN overflight and copyright by Carabineros de Chile.
Figure (see Caption) Figure 27. Images from a SERNAGEOMIN webcam showing the NE slope of Nevados de Chillán on several dates in July 2018. Significant ejecta from an explosion during the night of 13-14 July covered the rim of the crater and traveled down the NNE slope over the snow (top). Additional new ejecta appeared on the NNE slope on 15 July 2018 after a third explosion in three days (bottom left). Steam and gas plumes rose from the crater on 24 July 2018 (bottom right) and for the remainder of the month after the explosions during 13-15 July. Courtesy of SERNAGEOMIN.

An explosion midday on 7 August 2018 produced abundant high-temperature ejecta around the crater and a 1.5 km high ash plume, according to SERNAGEOMIN. Intermittent gray plumes were reported the next day and for the remainder of August, along with incandescence at night from high-temperature degassing and smaller explosive events (figure 28). The Buenos Aires VAAC reported sporadic and small puffs of ash visible in the webcam on 27 August.

Figure (see Caption) Figure 28. Activity during August 2018 included a number of ash plumes and incandescent explosions at Nevados de Chillán. Skier Birgit Erti captured this image of an ash plume rising after an explosion on 8 August (left); courtesy of Jaime S. Sincioco. Incandescence from explosions at Nevados de Chillán on 16 August (right) was typical of activity throughout the month; courtesy of SERNAGEOMIN.

Intermittent gray emissions and minor incandescence at night were typical of the activity during September 2018, except for a series of explosive events during 11-13 September (figures 29). An explosion on 11 September produced ejecta that traveled 300 m down the slope. The largest event, on 12 September, produced a 2.5-km-high dense ash plume and a pyroclastic flow that went 400 m down the E slope. Communities within 1 km of the crater reported ashfall. Drone video footage from 13 September posted by Nicolas Luengo V. showed the path of a block-and-ash flow down the flank and dense steam emissions with ash rising from the partially destroyed dome (figure 30) (Luengo and Palma, 2018). The Buenos Aires VAAC reported a small ash plume at 4.3-4.9 km altitude drifting SSW on 14 September. Satellite images from 16 September again showed partial destruction of the growing dome at the summit from the explosive events.

Figure (see Caption) Figure 29. Incandescent explosions on 12 September 2018 (left) generated significant ash and ejecta, including a pyroclastic flow, that spread down the flank of Nevados de Chillán. Fresh deposits from the explosions were visible on 14 September (right) from the webcam. Courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 30. Dense steam-and-ash rose from the dome inside the Nicanor crater at Nevados de Chillán on 13 September 2018 in multiple explosive events. Courtesy of Nicolás Luengo, used with permission.

The Buenos Aires VAAC reported an ash emission to 6.1 km altitude on 13 October 2018 seen in multispectral imagery under mostly clear skies moving SSE, and another isolated emission at the same altitude moving SE on 31 October. SERNAGEOMIN reported abundant ejecta scattered around the crater after the 13 October event. Another explosive event on 7-8 November produced incandescent ejecta and ash plumes that were the highest of the reporting period, rising to 7 km altitude and moving SE as reported by the Buenos Aires VAAC (figure 31).

Figure (see Caption) Figure 31. Explosive events at Nevados de Chillán on 7 and 8 November 2018 were recorded by the SERNAGEOMIN webcam on the NE flank (left, 8 November), and by Samuel Opazo T (right, 7 November), likely taken from a community about 40 km NW. Courtesy of SERNAGEOMIN and Samuel Opazo T.

For most of November 2018, pulsating emissions from the crater were accompanied by nighttime incandescence with small explosions and short-range ejecta. The SERNAGEOMIN webcam captured images of explosions on 23, 27, and 29 November. The Buenos Aires VAAC observed weak pulses of ash in satellite imagery at 3.9 km altitude on 23 and 27 November. The intermittent explosions with incandescent blocks and ash from June through November 2018 produced occasional low to moderate thermal anomalies that were captured by the MIROVA project (figure 32).

Figure (see Caption) Figure 32. Low to moderate power thermal anomalies at Nevados de Chillán were intermittent between June and November 2018, increasing slightly in both intensity and frequency towards the end of the period. Courtesy of MIROVA.

Reference: Luengo, Nicolas and Palma, Jose Luis, 2018, Morfometría y tasas de extrusión del domo de lava del Complejo Volcánico Nevados de Chillán mediante el uso de drones eimágenes satelitales, Concepción, Chile, XV Congreso Geológico Chileno, University of Concepción, DOI:10.13140/RG.2.2.35386.64966/1.

Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/), 16 July 2018 overflight video on YouTube (https://www.youtube.com/watch?v=SVFklfEnWXI); 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/); Nicolas Luengo, University of Concepcion (Twitter: @nluengov), 13 September drone video footage on YouTube (https://www.youtube.com/watch?v=BZt5X3rWoFM); Jaime S. Sincioco (Twitter: @jaimessincioco); Samuel Opazo T (Twitter: @OpazoSamuel).


Sabancaya (Peru) — December 2018 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Frequent ash plumes continued during June-November 2018

Sabancaya has been continuously active in recent years after renewed unrest began in February 2013 following almost 10 years of quiescence. After an increase in seismicity and an increase in the volume and frequency of fumarole emissions, the first explosion of the current eruption occurred in November 2016. Since then, activity has largely consisted of ash plumes and fumarolic activity.

This report summarizes activity during June-November 2018 (table 3) and is based on reports by the Observatorio Vulcanológico division of El Instituto Geológico, Minero y Metalúrgico (OVI-INGEMMET) and Instituto Geofísico del Perú (IGP), and satellite data. During this time the average daily number of explosions was 22, and ranged from 13 to 30. Maximum ash plume heights varied between 1.3 to 4.5 km above the crater, with the maximum plume heights each month usually between 2.5 and 3.7 km. SO2 emissions were variable and reached a maximum of 14,859 tons per day and the drift directions were wind dependent (figure 51).

Table 3. Summary of eruptive activity at Sabancaya during June-November 2018 based on OVI-INGEMMET weekly reports and the HIGP MODVOLC hotspot monitoring algorithm.

Month Avg. Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Max SO2 tons/day
Jun 2018 24, 19, 29, 24 1,300-2,500 20-30 km, E, S, SE 19 3,000-5,600
Jul 2018 22, 23, 25, 24 1,300-2,500 20-30 km, S, SE, E 12 4,715-14,859
Aug 2018 19, 23, 27, 25, 25 2,600-4,500 30-50 km, N, NE, S, SE 27 2,230-5,000
Sep 2018 17, 13, 16, 21 2,500-3,700 30-50 km, N, NE, S, SE, NW 28 1,600-3,970
Oct 2018 24, 17, 23, 30 2,500-3,500 30-50 km, N, NE, SE, S, SW, W 21 2,200-5,027
Nov 2018 30, 18, 20, 20, 21 2,500-3,700 30-40 km, N, E, SE, S, SW, W, NW 35 2,300-4,600
Figure (see Caption) Figure 51. Examples of SO2 plumes from Sabancaya detected by the NASA Ozone Monitoring Instrument (OMI) in July, September, and October 2018 (dates, times, and SO2 max values are given in the header of each image). Courtesy of NASA Goddard Flight Center.

During June, Sabancaya produced 19-29 explosions per day that ejected ash plumes up to heights of 1.3-2.5 km above the crater (figure 52). These ash plumes extended to 20-30 km away from the volcano. The maximum emissions of SO2 throughout the month ranged from 3,500 to 5,600 tons per day. There was a total of 19 MIROVA thermal anomalies.

Figure (see Caption) Figure 52. An IGP webcam recorded an ash plume at Sabancaya that reached 1,500 m above the crater on 21 June 2018. Courtesy of IGP via OVI-INGEMMET (RSSAB-25-2018 18-24 June 2018 report).

Throughout July there were on average 22-25 explosions per day. Ash plumes reached heights of 1.3-2.5 km above the crater, and drifted 20-30 km to the S, SE, and E (figure 53). On 23 July, Sabancaya produced a continuous ash plume that traveled over 100 km to the SE (figure 54). SO2 emissions were higher this month, with maximum emissions reaching 14,859 tons per day. Twelve MODVOLC thermal alerts were issued.

Figure (see Caption) Figure 53. An ash plume rising through meteorological clouds at Sabancaya on 16 July 2018. Courtesy of IGP via OVI-INGEMMET (RSSAB-29-2018 16-22 July 2018 report).
Figure (see Caption) Figure 54. The ash plume at Sabancaya on 23 July 2018 traveled over Chachani, Misti, and Ubinas volcanoes, and the Quinistaquillas, Carumas, and Calacoa districts. Courtesy of OVI-INGEMMET (13 August 2018 report).

There were an average of 19-27 explosions per day throughout August (figure 55). Ash plumes reached maximum heights of 2.6-4.5 km, and drifted 30-50 km away in various directions. Activity generated two ash plumes on 24 August, one to 4 km above the crater at 0800 and the other to 4.5 km at 0945 (figure 56). The ash was dispersed to the NE, N, and E for 30 km over the towns of Chivay, Yanque, Coporaque, Ichupampa, Achoma, Maca and Pinchollo. On the 25th, an explosion at 1020 produced an ash plume to over 3 km above the crater that resulted in ashfall in the towns of Achoma, Maca and Pinchollo. There were 28 MODVOLC thermal alerts throughout the month. The maximum SO2 emissions reached 2,230-5,000 tons per day.

Figure (see Caption) Figure 55. Photograph of an explosion producing an ash plume at Sabancaya in early August 2018, taken while OVI-INGEMMET installed monitoring equipment. Courtesy of OVI-INGEMMET (10 August 2018 report).
Figure (see Caption) Figure 56. An ash plume at Sabancaya on 24 August 2018 at 0947 that reached a 4.5 km above the crater. The ash was dispersed 30 km to the NE, N, and E, and impacted the towns of Chivay, Yanque, Coporaque, Ichupampa, Achoma, Maca, and Pinchollo. Courtesy of OVI-INGEMMET (27 August 2018 report).

There was an average of 13-21 explosions per day during September, with ash plumes reaching 2.5-3.5 km above the crater. The ash traveled 30-50 km away in different directions (figure 57). There were 28 MODVOLC thermal alerts issued throughout the month, consistent with elevated thermal activity that is visible in Sentinel-2 satellite images (figure 58). The maximum measured SO2 emissions were 1,600-3,970 tons per day. A drone overflight by the IGP and the Pontifical Catholic University of Peru (PUCP) in the third week of September gave the first view of the crater since the eruption began in 2016 (figure 59), revealing lava in the crater and at least six ash emission points.

Figure (see Caption) Figure 57. Sentinel-2 satellite image of an ash plume at Sabancaya on 17 September 2018. The ash plume was directed towards the NE, then the SE. Natural color (bands 4, 3, 2) image courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 58. Sentinel-2 satellite images showing elevated thermal activity (bright orange-red) in the Sabancaya crater on the 7 and 22 September 2018. False color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 59. Drone video of the Sabancaya crater was taken in September 2018 showed lava on the crater floor and ash emissions from six locations. This image is a screenshot taken from video collected during the collaborative overflight by IGP and the Pontifical Catholic University of Peru. Courtesy of IGP (24 September 2018 report).

Similar activity continued through October, with an average of 17-30 reported explosions per day. Ash plumes reached maximum heights of 2.5-3.5 km and dispersed 30-50 km in various directions (figure 60). Ashfall was reported in the Huanca area during the week of 1-7 October. Maximum SO2 emissions were 2,200-5,027 tons per day. There were 21 MODVOLC thermal alerts issued for the month.

Figure (see Caption) Figure 60. An example of an ash plume at Sabancaya on 28 October 2018. Courtesy of OVI-INGEMMET (RSSAB-43-2018 22-28 October weekly report).

November 2018 marked two years of uninterrupted activity at Sabancaya (figure 61). Between November 2016 and November 2017 there were 14,000 registered explosions with an average of 39 per day. From November 2017 to November 2018 there were more than 9,800 explosions recorded with an average of 27 per day. During the month there was an average of 18-30 explosions per day, with ash plumes reaching maximum heights of 2.5-3.7 km above the crater and dispersing 30-40 km in all directions. This month saw the highest number of MODVOLC thermal alerts with a total of 35. The maximum detected SO2 emissions were 2,300-4,600 tons per day.

Figure (see Caption) Figure 61. Graph showing the number of explosions per day at Sabancaya from November 2017 through to November 2018. Courtesy of IGP (6 November 2018 report).

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe; video URL: https://www.youtube.com/watch?v=CpLhruMwuxQ); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Stromboli (Italy) — December 2018 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Explosive activity produced ash, lapilli, and bombs, with occasional spattering during July-October 2018

Stromboli is a persistently-active volcano that currently has five active vents in the crater terrace area that sits above the steep slope of the Sciara del Fuoco. For several decades, activity has been focused at three main craters, the North crater (N area) and the Central and South craters (CS area), each with multiple frequently-active vents.

This report summarizes activity for July-October 2018 (table 4) and is based on reports by Istituto Nazionale di Geofisica e Vulcanologia (INGV) and satellite data. Intensities associated with explosions are based on the following heights of material ejected from the crater and are as follows. Very low is less than 40 m; low is 40-80 m; medium is 80-150 m; and high is greater than 150 m (figure 131). Overall, the intensity of all vents ranged from very low to medium, with variations in the eruption of ash and lapilli to bomb-sized material (less than 2 mm, 2-64 mm, and over 64 mm, respectively). The variations in activity of the five active vents during July-October is seen in Sentinel-2 thermal satellite data (figure 132).

Table 4. Activity at Stromboli during July-October 2018 summarized by vent areas: N Area (North) with vents N1 and N2; CS Area (central-south) with vents C, S1, and S2. Maximum reported heights for each month are given as meters above the crater. Data courtesy of INGV weekly reports.

Month N Area Activity CS Area Activity
Jul 2018 N1: Explosions ejected lapilli and bombs with some ash up to heights of 200 m. N2: Explosions ejected ash, lapilli, and bombs up to 200 m. The average explosion frequency for the N-Area was 1-19 per hour. C: Continuous degassing with intense Spattering on the 26th. S1: Gas jets with some ash, lapilli, blocks up to 80 m. S2: Explosions with ash, lapilli, blocks up to 150 m. The average explosion frequency for the CS-Area was 1-11 per hour.
Aug 2018 N1: Explosions ejected lapilli and bombs with some ash up to 140 m. N2: Explosions ejected lapilli and bombs with occasional spattering up to 140 m. The average explosion frequency for the N-Area was 2-20 per hour. C: Continuous degassing at two points, intense spattering on the 27th. Some explosions ejected material up to 120 m. S1: Explosive activity and gas jets, incandescent material up to 150 m. S2: Explosive activity ejected material up to 80 m. Major explosion occurred at the CS area on the 18th.The average explosion frequency for the CS-Area was 1-15 per hour.
Sep 2018 N1: Explosions ejected lapilli and bombs with some ash up to 140 m. N2: Explosions ejected mainly ash with some lapilli and bombs up to 150 m. The average explosion frequency for the N-Area was 2-12 per hour. C: Two emission points with continuous degassing, interrupted by explosions and spattering. S1: Jets of incandescent material up to 120 m. S2: Explosive activity with some ash and lapilli up to 120 m, two active vents from the 10th. The average explosion frequency for the CS-Area was 4-20 per hour.
Oct 2018 N1: Explosions ejected lapilli and bombs with some ash up to 150 m. N2: Explosions ejected mostly ash with some lapilli and bombs up to 150 m. The average explosion frequency for the N-Area was 1-13 per hour. C: Two emission points with continuous degassing interrupted by occasional spattering and explosions. S1: Jets of incandescent material up to 120 m. S2: Variable explosive activity ejecting material up to.120 m. The average explosion frequency for the CS-Area was 6-20 per hour.
Figure (see Caption) Figure 131. A thermal image of the active craters of Stromboli showing the Central-South crater (Area CS) and northern crater (Area N), with the active vents S1, S1, C, N1, N2. The white horizontal lines show the heights attributed to explosion intensity: low (bassa), medium (media), and alta (high). Image taken on 29 October 2018, courtesy of INGV (Report No. 44/2018, released on 30 October 2018).
Figure (see Caption) Figure 132. Infrared Sentinel-2 satellite images showing thermal variations at vents on Stromboli during July-October 2018. The active vents are shown in bright yellow-orange and gas plumes appear as light blue-white areas emanating from the vents. Courtesy of Sentinel Hub Playground.

During July Strombolian activity continued with explosions of low to medium-low intensity in the N Area; variable explosions ejected mainly lapilli and bombs along with some ash at the N1 vent, and mainly ash with lapilli and bombs at the N2 vent. Explosive activity was absent or sporadic at the N2 vent during 4-5 July. There was a rapid increase in explosion frequency at the N1 vent on the 14th, and on the 16th lapilli and bombs were ejected. During 16-29 July explosive activity in the N Area was focused at the N2 vent. The average frequency of explosions in the N area ranged from 1-19 per hour. Explosion intensity in the CS Area ranged from low to medium at both the S1 and S2 vents. The C vent produced continuous degassing that was interrupted by intense spattering on the 26th. Activity at the S1 vent was characterized as jets with some ash, lapilli, and blocks, and explosions with ash, lapilli, and blocks occurred at the S2 vent. The average frequency of explosions in the CS area ranged from 1 to 11 per hour during July. The total number of explosions at Stromboli increased in mid-July and remained elevated compared to previous months through the end of October (figure 133).

Figure (see Caption) Figure 133. Graph showing the average number of explosions at Stromboli per day from 1 January to 20 October 2018. The red data are for the N crater area, green are for the CS crater area, and dark blue are the total explosions per day for all active vents. There was a period from mid-January to mid-July when there was a reduction in the frequency of explosions, which then increased to around a total of 15-30 per day. Courtesy of INGV (Report No. 44/2018 released on 30 October 2018).

Similar activity continued through August with the exception of a strong explosion at the C vent that lasted approximately one minute at 1508 on 18 August (figure 134). The explosion ejected an ash plume that rapidly dissipated. Coarse pyroclastic material fell on the crater terrace area and the upper part of the Sciara del Fuoco, and rolled down to the ocean. Occasional intense spattering at the C vent was also observed on the 27th, interrupting the continuous degassing from two vents. Medium to low, and occasionally high-intensity gas jets that incorporated incandescent material were frequent at the S1 vent through August. Low- to medium-intensity explosive activity occurred at the S2 event throughout the month. Explosions averaged 1-11 per hour for the entire CS area during August. The N area produced variable explosions that ejected lapilli and bombs with some ash at the N1 vent. During 8-12 August most of the activity in the N area continued to be focused at the N2 vent, and during this time it produced intense spattering activity. During the rest of the month activity at the N2 vent was characterized by variable explosive activity that produced lapilli and bombs with occasional spattering. The average frequency of explosions for the month was 2-20 per hour.

Figure (see Caption) Figure 134. The major explosion at the Stromboli C vent on 18 August 2018 as seen in thermal and photograph images. The brief (less than one minute) explosion produced an ash plume that deposited material around the vent and on the Sciara del Fuoco. Courtesy of INGV (Report No. 34/2018 released on 21 August 2018).

The typical activity persisted through September with explosions producing ash, lapilli, and blocks (figures 135 and 136), gas jets with incandescent material (figures 137 and 138), and degassing. Over the month there was an average of 2-12 explosive events per hour at the N area, and an average of 4-20 events per hour at the CS area. Variable explosions that ejected lapilli and bombs with some ash characterized activity at the N2 vent, and mainly ash with some lapilli and bombs were typically ejected at the N1 vent. Continuous emissions originated from two points within the C vent and was occasionally interrupted by explosions and spattering. Jets of gas and incandescent material continued at the S1 vent and explosive activity with some ash and lapilli occurred at the S2 vent. The S2 vent had two active points from the 10 September onwards.

Figure (see Caption) Figure 135. Ash plumes and degassing on 10 September. Courtesy of Benjamin Simons, The University of Auckland.
Figure (see Caption) Figure 136. Thermal infrared video screenshots showing multiple active vents in the Stromboli central-south crater area on 10 September 2018. Vents are actively degassing and explosions eject hot lapilli and blocks at two craters. Courtesy of Benjamin Simons, The University of Auckland.
Figure (see Caption) Figure 137. A gas jet with incandescent lapilli and bombs from the Stromboli central-south crater area on 10 September 2018. White gas plumes are visible emanating from other vents in the central-south and north craters. Courtesy of Benjamin Simons, The University of Auckland.
Figure (see Caption) Figure 138. Screenshots of a video showing a gas jet with incandescent lapilli, bombs, and ash from the Stromboli Central-South crater area on 10 September 2018. A large bomb can be seen ejecting from the vent in the top photo. White plumes are a result of degassing of the surrounding vents. Courtesy of Benjamin Simons, The University of Auckland.

During October variable explosions continued to produce low-to medium-intensity explosions that ejected lapilli and bombs, and sometimes ash, at the N1 vent, and very low- to low-intensity explosions that produced mostly ash with some lapilli and bombs at the N2 vent. Explosions averaged 1-13 events per hour through the month. The CS area produced a higher average of 6-20 explosions per hour for October. Sustained degassing continued at two points in the C vent. Low- to medium-low-intensity jets on incandescent material occurred at the S1 vent, and the same intensity of explosive activity was reported at the S2 vent.

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/); Benjamin Simons, The University of Auckland, 23 Symonds Street, Auckland, 1010, New Zealand (URL: https://unidirectory.auckland.ac.nz/people/profile/bsim836); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Santa Maria (Guatemala) — December 2018 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Ash plumes, degassing, and avalanches continue during May-October 2018 with occasional lahars

Santa Maria is one of the most active volcanoes of Guatemala. The volcano is composed of a large edifice that reaches over 3.7 km above sea level; the Santiaguito dacitic dome complex to the SW, with the active Caliente dome, rises to a height of over 2.5 km (figure 77). The Santiaguito dome complex is situated in a large crater that formed during a catastrophic eruption in 1902. Growing since 1922, this complex has recently been characterized by dome-growth activity that includes degassing, ash plumes, avalanches, pyroclastic flows, lava flows, and lahars. This report summarizes activity from May through October 2018, and is based on reports by Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and satellite data. During this period, activity consisted of degassing, ash plumes, and avalanches at the Caliente dome, and lahars in multiple tributaries. Intermittent low-power thermal anomalies were detected throughout this period (figure 78).

Figure (see Caption) Figure 77. Santa Maria volcano consists of an older, larger peak to the NW and the Santiaguito dome complex to the SW. Top: The currently-active dome, Caliente, is situated in the 1.5-km-wide collapse crater. Bottom: The Caliente dome has fresh, unstable material accumulating in the crater that is prone to avalanches; image of the dome on 8 August 2018 (4-10 August 2018 weekly report). Courtesy of INSIVUMEH.
Figure (see Caption) Figure 78. Log radiative power MIROVA plot of MODIS infrared data at Santa Maria for May through November 2018. Courtesy of MIROVA.

Throughout May, active degassing of the dome produced white plumes up to 3.2 km above sea level. Frequent weak to moderate explosions produced white and gray ash plumes up to 3.3 km that were dispersed to the SW, W, and SE. As many as 15 explosions were recorded per day. Avalanches frequently occurred on the SE flank of the Caliente dome. The first lahar of the year was generated by rainfall on 10 May and traveled down the Cabello de Angel-Nimá I river. The lahar was composed of abundant fine material with larger branches and blocks up to 1 m in diameter, and it smelled of sulfur. The lahar deposit was 15 m wide and 1.2 m thick. A second lahar descended along the same path on 24 May and emplaced a deposit with a width of 18 m, a depth of 2 m, and blocks up to 2 m in diameter.

During June, white plumes associated with degassing of the Caliente dome often reached altitudes of 2.9 km, with a maximum of 3.9 km on 5 June. An average of 9-11 weak to moderate explosions per day ejected white and gray ash plumes up to 3.1-3.3 km altitude that were dispersed to the SW, W, and SE (figures 79 and 80). Ashfall was reported in Monte Claro on 26 June. Avalanches were recorded most days on the SE side of the dome due to ongoing growth. Lahars were reported on 13, 14, and 16 June down the Nimá I and Cabello de Ángel tributaries of the Samalá River (figures 81 and 82).

Figure (see Caption) Figure 79. A moderate explosion from the Caliente dome at Santa Maria generated an ash plume on 10 June 2018. Courtesy of INSIVUMEH (9-15 June 2018 weekly report).
Figure (see Caption) Figure 80. During the week of 23-30 June 2018 there was an average of 11 weak to moderate explosions per day at Santa Maria, as well as short avalanches on the S side of the dome. Left: a moderate explosion producing a plume from the Caliente dome. Right: Seismicity associated with activity of the dome including weak to moderate explosions. Courtesy of INSIVUMEH (modified from 23-30 2018 June report).
Figure (see Caption) Figure 81. Real-time Seismic-Amplitude Measurement (RSAM) graph showing four peaks corresponding to lahars on the 13 and 14 June 2018. The lahars traveled from Santa Maria down the Nimá I and Cabello de Ángel tributaries of the Samalá River. Courtesy of INSIVUMEH (9-15 June 2018 weekly report).
Figure (see Caption) Figure 82. The seismic signal produced by a lahar at Santa Maria on 16 June 2018. The lahar traveled down the Nimá I river channel. Courtesy of INSIVUMEH (16-22 June 2018 weekly report).

Throughout July, degassing of the dome and fumarolic activity produced white plumes reaching 3 km. These plumes were dominantly directed towards the SW and SE, and on a few days towards the N and W. Explosions frequently produced white and gray ash plumes up to 11 times per day (figure 83). Ash plumes often reached approximately 3.2 km altitude, drifted SE, SW, and W, and frequently deposited ash on the flanks. On 4 July an explosion produced incandescent material up to 150 m above the crater and the accompanying sound was heard in areas including El Palmar, Pueblo Nuevo, and San Felipe Retalhuleu. Avalanches most often occurred on the SE flank of the dome, with some occurring on the N, NE, and W flanks (figure 84). Incandescence was observed on the 11 July.

Figure (see Caption) Figure 83. Examples of plumes from moderate (top) and weak (bottom) explosions at Santa Maria's Caliente dome in July 2018. Courtesy of INSIVUMEH (July 1-6 and 21-27 July 2018 weekly reports, respectively).
Figure (see Caption) Figure 84. Avalanches on Santa Maria's Caliente dome during July 2018. Top: A small avalanche on the SE flank of the dome (7-13 July 2018 weekly report). Bottom: A moderate avalanche on the SE flank of the dome (21-17 July 2018 weekly report). Courtesy of INSIVUMEH.

Through August, degassing of the dome regularly produced white plumes up to a maximum observed altitude of 3.2 km (figure 85). Explosions generated white and gray ash plumes up to 3.1-3.3 km on most days, with a maximum of 13 explosions recorded per day. Gas-and-steam and ash plumes were often dispersed to the SE and sometimes towards the W. Ashfall often occurred on the slopes. Avalanches on the dome were recorded most days on the SE flank and sometimes on the E, NE, and W flanks. On 17 August at 1330 a lahar emplaced a deposit 18 m wide and 2.5 m thick, with blocks up to 3 m in diameter.

Figure (see Caption) Figure 85. Degassing of the Santa Maria Caliente dome forming white plumes during August 2018. Courtesy of INSIVUMEH (27 July-3 August 2018 and 4-10 August 2018, respectively).

Throughout September, degassing and fumarole activity of the Caliente dome produced white plumes up to 3.1 km. Explosions produced ash plumes that reached altitudes of 3.3 km up to 13 times per day. Degassing and ash plumes were most often dispersed to the SW, and sometimes to the W and SE. Red discoloration of ash was noted on 4 September due to the oxidation of the dome rock where the explosion was generated (figure 86). Ashfall often occurred within the proximity of the volcano. Avalanches were often reported as constant on the SE flank of the dome and sometimes occurring on the NE and E flanks. On 12 September a lahar was recorded traveling down both tributaries of the Samalá River. A larger lahar was generated on 20 September in the San Isidro-Tambor tributaries of the Samala River with a width of 25 m and a thickness of 2 m. The lahar carried tree trunks and branches, and blocks up to 2 m in diameter. A third lahar occurred on 24 September down the Cabello de Ángel River, with a width of 15 m, a thickness of 1.5 m, and carrying blocks up to 2 m in diameter.

Figure (see Caption) Figure 86. Oxidation in and around the crater of Caliente dome (top) at Santa Maria occurs due to the high temperatures and causes red discoloration of the rock. This leads to discolored plumes as seen on 4 September 2018 (bottom). Courtesy of INSIVUMEH (1-7 October 2018 weekly report).

Degassing at the dome during October produced white plumes to a maximum altitude of 3.2 km (figure 87). Explosions generated white and gray ash plumes up to 3.2 km, with up to 11 explosions recorded per day and an average of 8-9 per day. Plumes were often directed towards the SE, and sometimes to the W and NW. Ashfall frequently occurred on the slopes and was reported in Monte Claro on 16 and 26 October. Avalanches were frequent on the SE flank of the dome, and sometimes occurred on the W and NE flanks (figure 88). Incandescent material was observed during explosions on the 23rd. Two lahars were generated on 9 October; one traveled down the Cabello de Ángel river channel with a width of 20 m, a thickness of 2 m, and carrying blocks as large as 3 m in diameter. The second was 15-m-wide with a thickness of 1 m and blocks as large as 2 m in diameter which traveled down the San Isidro River.

Figure (see Caption) Figure 87. The Caliente dome of Santa Maria, the active dome of the Santiaguito dome complex. Top: degassing at the edge of the crater on 15 October 2018. Bottom: A moderate explosion that produced an ash plume with abundant gas on 16 October. Courtesy of INSIVUMEH (13-19 October 2018 weekly report).
Figure (see Caption) Figure 88. An avalanche on the NE flank of the Caliente dome of Santa Maria on 25 October 2018 with the corresponding seismic signal that lasted 3 minutes and 40 seconds. Courtesy of INSIVUMEH (20-26 October 2018 weekly report).

Geologic Background. Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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/ ); 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/).


Kilauea (United States) — December 2018 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Lava fountains on the Lower East Rift Zone build 50-m-high pyroclastic cone and 13-km-long lava flow that engulfs Kapoho Bay during June 2018; 533 homes destroyed since 1 May

Kilauea's East Rift Zone (ERZ) has been intermittently active for at least two thousand years. Open lava lakes and flows from the summit caldera and East Rift Zone have been almost continuously active since the current eruption began in 1983. A marked increase in seismicity and ground deformation at Pu'u 'O'o Cone on the upper East Rift Zone on 30 April 2018 and the subsequent collapse of its crater floor marked the beginning of the largest lower East Rift Zone eruptive episode in at least 200 years.

During the month of May 2018 there were 24 fissures that opened along a 6-km-long NE-trending fracture zone on the lower East Rift Zone spawning lava flows in multiple directions, including several that traveled about 5 km SE to the coast; at least 94 structures were destroyed in the Leilani Estates subdivision and adjacent areas (BGVN 43:10). As lava emerged from the fissures, the lava lake at Halema'uma'u drained and explosions produced plumes that spread minor amounts of ash to downwind communities. At the end of May eruptive activity refocused around fissure 8, which began fountaining lava tens of meters into the air and creating a voluminous incandescent flow that headed downslope to the NE. The eruptive events of June 2018 (figure 386), the second month of this episode, are described below with information provided primarily from the US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) in the form of daily reports, volcanic activity notices, and abundant photo, map, and video data.

Figure (see Caption) Figure 386. A timeline of events at Kilauea for 28 May-30 June 2018. Blue shaded region denotes activity at Halema'uma'u crater at the summit. Green shaded area describes activity on the lower East Rift Zone (LERZ). HST is Hawaii Standard Time. Black summit symbols indicate earthquakes (diamonds) and ash plumes (stars); red LERZ symbols indicate lava fountains (stars), lava flows (triangles) and lava ocean entry.

Summary of events during June 2018. Lava fountains from fissure 8 were reaching 60 m in height on 29 May 2018 and producing a vigorous stream of lava that traveled rapidly downslope. Several lobes of lava advanced ENE, some at rates of several hundred meters per hour. Fissure 18 was also generating a narrow flow that headed SE for 3 km before stopping. A spatter cone began growing at fissure 8 and reached 30 m in height in just a few days. On the morning of 2 June the fissure 8 flow covered the Four Corners Intersection of Highways 132 and 137, and continued E and then SE around Kapoho Crater; lava flowed into the crater and evaporated the fresh water lake inside. Traveling at a rate of about 75 m per hour, the flow moved towards the shore and reached Kapoho Bay late on 3 June, where it began building a delta. In just a few days the delta was a kilometer in width, and lava was entering the ocean in many streams along the flow front, generating dense plumes of steam and laze.

By 15 June the fissure 8 cone had reached just over 50 m in height. Fissure 8 lava fountains persisted at 40-70 m high for all of June, feeding the 13-km-long channel to Kapoho Bay. Periodic overflows along the channel built up the levees on either side of the fast-moving river of lava; they were short-lived and traveled only a few meters. Flow speeds slowed as the lava spread out over the delta, which reached 150 hectares (380 acres) in size by 20 June. The ocean-entry points migrated north and south along the delta over the course of the month, expanding the width of the ocean entry area to over 3 km. Towards the end of June, lava was crusted over in the delta up to 1 km back from the ocean, and molten material was traveling within the interior of the earlier flows to the ocean. Minor oozing of lava was reported from a few other fissures during the month, but no other significant flow activity was observed.

Within Halema`uma`u crater at the summit a near-daily pattern of collapse explosion events was due to the subsidence caused by the magma withdrawal. As the crater subsided, its rim and walls slumped inward and large blocks dropped down along growing fractures around the caldera with seismic energy releases greater than M 5.0 almost every day. The deepest part of the crater had reached 400 m below the caldera floor by late June.

Activity at the Lower East Rift Zone during 29 May-4 June 2018. By 29 May, activity on Kilauea's lower East Rift Zone was focused on the vigorous eruption of lava from fissure 8 advancing rapidly downslope towards Highway 132. Lava fountains from fissure 8 reached 60 m in height on 29 May, feeding a flow that advanced NE over a flow from a few days earlier. The first lobe of the flow crossed Highway 132 just before 1400 that afternoon and continued NE. Most of the flow remained on the S side of the highway as it moved downslope. Visual observations in the early afternoon also confirmed continued weak activity at fissures 18 and 16. Fissure 18 had produced channelized flows which advanced about 2.6 km toward the coast during the previous day. At the ocean entry on the SE coast, only a few small channels of lava were still entering the ocean. Fissure 8 maintained high fountains throughout the day and into the overnight of 29-30 May with sustained heights exceeding 60 m and multiple secondary fountains that reached 20 m. As the flow moved downslope along the highway, the advance rates accelerated overnight, reaching approximately 550 m/hour. Overnight, sporadic bursts of activity were also observed from fissures 7 and 15.

Fissure 8 maintained fountains that rose 60-75 m high on 30 May. The flow split into three lobes; the two easternmost lobes advanced in a more ENE direction while the westernmost lobe advanced in a NE direction (figure 387). The flow rate had dropped to around 90 m/hour by late afternoon and slowed further to 45 m/hour by late evening. The fissure 18 flow also remained active, moving downslope toward Highway 137 at rates of less than 90 m/hour. By late afternoon, the front of the fissure 18 flow was about 1 km from Highway 137 and was spreading and slowing (figure 388). In the late afternoon, a new flow lobe began branching from the S side of the fissure 18 flow approximately 2 km upslope from the flow front. Throughout the day, sporadic bursts of activity were also observed from fissures 22, 6, and 13.

Figure (see Caption) Figure 387. A major lava flow that first emerged from Kilauea's fissure 8 on 28 May was moving rapidly downslope to the NE when photographed during HVO's early morning overflight on 30 May 2018. The lava channel was estimated to be about 35 m wide; 60-m-high fountains from the fissure are visible in the upper right. Courtesy of HVO.
Figure (see Caption) Figure 388. Kilauea's Lower East Rift Zone had many active flow fronts as of 1500 HST on 30 May 2018. Active fissures and flows are shown in dark red. Shaded purple areas indicate lava flows erupted in 1840, 1955, and 1960. Courtesy of HVO.

Four lobes of the fissure 8 flow advanced on 31 May (figure 389), fed by persistent fountaining that reached heights up to 80 m. A spatter cone was forming on the downwind side of the fountain and was approximately 30 m high. The fountains were feeding the flow to the NE, and minor overflows from the growing fissure 8 channel were occurring along its length, covering several of the remaining roads in Leilani Estates. The front of the flow advanced at about 90 m/hour through agricultural lands and was within 1.7 km of the Four Corners area (the intersection of Highways 132 and 137) by the evening. The fissure 18 flow that had advanced to within 1 km of Highway 137 had stalled. The new flow that branched from the fissure 18 channel 2 km upslope appeared to have captured most of the lava output from fissure 18. It descended downslope just to the S of the previous flow. Lava was pooling around the vent of fissure 22 throughout the day.

Figure (see Caption) Figure 389. Four advancing lobes from Kilauea's LERZ fissure 8 were moving 75 m per hour to the NE on the morning of 31 May 2018 in this view to the E. The flow moved north of Highway 132 in the vicinity of Noni Farms and Halekamahina roads, from which the two easternmost lobes advanced in a more ENE direction while the westernmost lobe advanced in a NE direction. Courtesy of HVO.

The advance rates of the distal part of the fissure 8 flow were low overnight on 31 May-1 June as lava ponded in a flat area, but flow continued throughout the day to within 0.5 km of the Four Corners intersection of Highways 132 and 137 by evening; fissures 18 and 22 were inactive. By 0645 on 2 June it was about 100 m from the intersection (figure 390). Around 0930 on 2 June a broad front over 275 m in width extending both north and south of Highway 132 (figures 391) crossed the intersection and continued advancing into Kapoho Crater (sometimes called Green Lake Crater) and Kapoho Beach Lots. It entered Green Lake within the crater, creating a large steam plume that was visible until 1330. The Hawaii County Fire Department reported around 1500, after an overflight, that lava had filled the lake and apparently boiled away all the water.

Figure (see Caption) Figure 390. This thermal map of Kilauea's LERZ fissure 8 flow shows the location of the lava front as of 0645 on 2 June 2018 shortly before it reached the Four Corners intersection. At that point it was roughly 10 km from the vent. The black and white area is the extent of the thermal map. Temperature is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.
Figure (see Caption) Figure 391. Around 0715 on 2 June 2018 Kilauea's LERZ fissure 8 flow was a 275-m-wide lava front advancing on both sides of Highway 132 (left); the flow front was approximately 90 m west of the Four Corners Intersection when USGS scientists on HVO's morning overflight captured this image. Note trees and highway for scale. Courtesy of HVO.

The flow continued to advance overnight on 2-3 June along an 800-m-wide front towards the ocean at Kapoho Bay between Kapoho Beach Road and Kapoho Kai Drive. As of 0700 on 3 June, the lava flow was around 450 m from the ocean (figures 392 and 393) traveling at a rate of about 75 m/hour. By 1745 it had advanced to within 225 m of the ocean at its closest approach point. The other branches of the fissure 8 lava flow were inactive, and all other fissures were inactive, although observers on the late afternoon overflight noted abundant gas emission from fissures 9 and 10 and incandescence without fountaining at fissures 16 and 18.

Figure (see Caption) Figure 392. At 0700 HST on 3 June 2018 Kilauea's LERZ fissure 8 flow front was about 450 m from the ocean, advancing at about 75 m/hour. View is to the W looking up the flow front. Nearly all of the front was active and advancing. Courtesy of HVO.
Figure (see Caption) Figure 393. The flow front of Kilauea's LERZ fissure 8 on the morning of 3 June 2018 was advancing around 75 m/hour along a broad front towards Kapoho Bay. Dark red areas are active flow expansion, shaded purple areas indicate lava flows erupted in 1840, 1955, and 1960. Courtesy of HVO.

Fountaining lava 45-75 m high at fissure 8 continued overnight on 3-4 June, feeding the growing lava channel flowing NE along Highway 132 to the Kapoho area. Throughout 30 May-3 June tephra landing downwind from the fountaining produced a growing pyroclastic cone at fissure 8 (figure 394). Local videographers reported that lava entered the ocean at Kapoho Bay at about 2230 HST on 3 June and began constructing a delta (figure 395); by late afternoon the next day the delta extended about 640 m into the bay. A laze plume (a corrosive seawater steam plume laden with hydrochloric acid and fine volcanic particles) was blowing inland from the ocean entry but dissipating quickly. The lava flow front was about 800 m wide. A lava breakout was also occurring upslope (N) of the Kapoho cone cinder pit. A lava breakout from the S margin of the flow near the intersection of Highway 132 and Railroad Avenue had completely encircled Kapoho Cone by the end of the day.

Figure (see Caption) Figure 394. A comparison of thermal images of the fountains and fast-growing pyroclastic cone at Kilauea's LERZ fissure 8 from 30 May to 3 June 2018 indicated the increase in height of the lava fountains from 45 to over 75 m, as well as the growth of a cone (pu'u) downwind to about 30 m height. HVO reported the lava fountain temperatures were reaching up to about 1,115°C (2,040°F). The composition of the lava erupted had high MgO (magnesium oxide) values, which came from olivine crystals that were being pulled from deep within the rift zone. Courtesy of HVO.
Figure (see Caption) Figure 395. The flow front of Kilauea's LERZ fissure 8 flow reached the ocean at Kapoho Bay late in the evening of 3 June; by 0613 HST on 4 June 2018 when this image was taken during an HVO overflight, the lava was creating a large laze plume and beginning to form a delta into the bay. Courtesy of HVO.

Activity at the Lower East Rift Zone during 5-12 June 2018. The intensity of the fountaining at fissure 8 declined overnight on 4-5 June to between 40-50 m in height, not far above the top of the cone formed during the previous several days (figure 396). By the early morning of 5 June the fissure 8 flow had completely filled Kapoho Bay, extending 1.1 km from the former coastline (figure 397). On the south side of the ocean entry, lava was entering the water at the Vacationland tidepools, having inundated most of that subdivision. To the north, lava had covered all but the northern part of Kapoho Beach Lots. The northernmost lobe of the fissure 8 flow, in the Noni Farms Road area, advanced downslope about 180 m overnight (figure 398) and continued to slowly advance during the day on 5 June.

Figure (see Caption) Figure 396. Lava fountains continued at Kilauea's LERZ fissure 8, although overnight on 4-5 June 2018 USGS field crews reported reduced fountain heights. The lava fountain had built a 35 m (115 ft) high spatter cone, and an actively-growing spatter rampart on its eastern side. The lava channel leading from the cone was filled to the top of its levees at the time of this photo. The white objects in the upper left are the roofs of houses adjacent to the edge of the flow levee. Courtesy of HVO.
Figure (see Caption) Figure 397. Kapoho Bay was filled with lava from Kilauea's LERZ fissure 8 flow by the morning of 5 June 2018, as seen in this view looking S during the morning HVO overflight. Hundreds of homes around the bay were buried within the lava flow. Courtesy of HVO.
Figure (see Caption) Figure 398. By 1000 HST on 5 June 2018 there were two growing areas of active ocean entry on the delta at the front of Kilauea's LERZ fissure 8 lava flow. Dark red areas are active flows and shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.

By the morning of 6 June 2018, the lava fountaining at fissure 8 continued to reach heights of 45-55 m and feed a stable channel to the NE and E (figure 399) to the ocean entry in the Kapoho Bay area. The lava delta that formed at the bay had also extended slightly outward overnight; during the day on 6 June a lateral lobe of the flow pushed slowly N through what remained of the Kapaho Beach Lots subdivision. Overnight on 6-7 June and throughout the following day the fountain heights from fissure 8 fluctuated between 58 and 70 m feeding the channel with vigorous flow (figure 400). The delta was about 1.9 km wide in the Vacationland/Waopae area and the flow was expanding northward (figure 401). By the late afternoon overflight on 8 June, two vigorous steam plumes were rising from the ocean flow front and being blown inland. Strong thermal upwelling was noted in the ocean extending up to 900 m out to sea from the visible lava front. Heavy gas and steam emissions were noted at fissures 9 and 10, but lava emission was occurring only at fissure 8.

Figure (see Caption) Figure 399. HVO used drones, referred to as Unmanned Aircraft Systems (UAS), to gather high-resolution video and images throughout the eruption on Kilauea's lower East Rift Zone. On 6 June 2018 a UAS flight collected video of flowing lava in the upper lava channel of fissure 8. The view is to the S towards the fissure 8 cone in the upper left. The houses on the right provide a sense of scale for the fissure 8 flow. Scientists used the video to assess lava flow velocities, which are measured by tracking surface features in the stationary video view. This still image was taken from video captured by the U.S. Geological Survey and Office of Aviation Services, Department of the Interior, with support from the Hawaiian Volcano Observatory. Courtesy of HVO.
Figure (see Caption) Figure 400. In this early morning view to the E on 7 June 2018, fountains of lava rise 50 m from Kilauea's LERZ fissure 8 and the lava channel travels NE to the ocean, a distance of about 12.5 km. Steam plumes in the distance rise from inactive fissures that opened during May. Courtesy of HVO.
Figure (see Caption) Figure 401. By 8 June 2018, Kilauea's LERZ fissure 8 flow had created a lava delta approximately 77 hectares (190 acres) in size, filling Kapoho Bay and shallow reefs along the nearby coastline. Dark red areas are active flows, shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.

Overnight on 8-9 July the fountains at fissure 8 were slightly lower, reaching heights of 40-55 m. Fissure 22 was incandescent and there was minor lava activity at fissures 16/18 while the fuming from fissures 24, 9, and 10 had decreased from the previous day. The fissure 8 flow had created a lava delta approximately 80 hectares (200 acres) in size by the morning of 9 June, filling Kapoho Bay and covering shallow reefs along the nearby coastline (figure 402); observers that night also noted vigorous convection taking place up to 1.5 km offshore from the entry points. Minor levee overflows along the upper part of the channel occurred on 10 June from the strong channelized flow (figure 403). Near the Four Corners region the channel was incandescent and flowing vigorously.

Figure (see Caption) Figure 402. A view from offshore of the Kapoho ocean entry of Kilauea's LERZ fissure 8 flow as of 0630 HST on 9 June 2018 shows the extent of the lava delta, about 80 hectares (200 acres) in size, that formed over the previous six days. Across the front of the delta plumes of laze, created by molten lava interacting with seawater, appeared diminished that morning, but this was probably due to a change in atmospheric conditions rather than a change in the amount of fissure 8 lava reaching the ocean. Courtesy of HVO.
Figure (see Caption) Figure 403. Overflows of the upper channel at Kilauea's LERZ fissure 8 lava flow on 10 June 2018 sent small flows of lava down the levee walls. These overflows did not extend far from the channel, so they posed no immediate threat to nearby areas. Channel overflows, like the ones shown here, add layers of lava to the channel levees, increasing their height and thickness. In the lower right of the photo, a paved road and power lines provide a scale for the size of the flow channel and levees. Courtesy of HVO.

By the evening on 10 June, three closely spaced lava fountains at fissure 8 were erupting with maximum heights reaching 35-40 m (figure 404), feeding the fast moving channelized and braided flow that now traveled 13 km to the ocean at Kapoho Bay (figure 405). A strong steam plume was observed on the S end of the ocean entry with frequent steam explosions at the flow front. Weak lava activity continued during 10-12 June at fissures 16/18 as it had for the previous several days (figure 406). Incandescence was noted at fissures 15 and 22 on 12 June. Lava was entering the ocean over a broader area than before with several minor incandescent points and small plumes, and two larger entries and corresponding plumes. The fissure 8 cinder cone had reached about 43 m in height by the evening of 12 June.

Figure (see Caption) Figure 404. The three closely spaced lava fountains at Kilauea's LERZ fissure 8 reached maximum heights of 35-40 m overnight 10-11 June 2018. Lava fragments falling from the fountains were building a substantial cinder-and-spatter cone around the erupting vent, with the bulk of the fragments falling on the downwind side of the cone. The cone had reached 43 m in height by 12 June. Courtesy of HVO.
Figure (see Caption) Figure 405. Braided channels of lava from Kilauea's LERZ fissure 8 covered a wide swath of the NW side of the LERZ in the morning on 12 June 2018. Incandescence from the fountain feeding the flow is visible several kilometers in the distance in this image looking upstream. The 13-km-long flow traveled NE then E and flowed into Kapho Bay. Courtesy of HVO.
Figure (see Caption) Figure 406. The fountains at Kilauea's LERZ fissure 8 remained active as of 1400 HST on 12 June 2018, with the 13-km-long lava flow entering the ocean at Kapoho Bay along a growing delta. Very small, weak lava flows were also active near the fissure 18 area (center). The black and white area is the extent of the thermal map. Temperature in the thermal image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.

Activity on the Lower East Rift Zone during 13-19 June 2018. Lava fountaining at fissure 8 during 13-19 June generally rose 30-50 m with intermittent bursts as high as 60 m. The growing cone was 52 m at its highest point on 15 June (figure 407). From fissure 8, lava flowed freely over small cascades (rapids) into a well-established channel (figure 408). Near the vent, channel lava was traveling about 24 km/hour; it slowed as it traveled the 13 km-long-channel (figure 409) to about 2 km/hour near the ocean entry at Kapoho Bay. Minor amounts of lava periodically spilled over the channel levees.

Figure (see Caption) Figure 407. Lava fountains were still rising higher than the 52-m-high cone at Kilauea's LERZ fissure 8 on 15 June 2018. Courtesy of HVO.
Figure (see Caption) Figure 408. Cascades of lava from 50-m-high fountains flowed over rapids into the channel of Kilauea's LERZ fissure 8 lava flow on 17 June 2018. Near the vent, lava was traveling about 24 km per hour; lava slowed to about 2 km per hour near the ocean entry at Kapoho.
Figure (see Caption) Figure 409. Lava flowed in an open channel 13 km long to the ocean from Kilauea's LERZ fissure 8 on 18 June 2018. Kapoho Crater, which partly filled with lava on 2 June, is the vegetated hill on the right side of the photograph. The lava evaporated Green Lake inside the crater. The ocean entry plume can be seen in the distance on the left. The small white objects on either side of the flow are large buildings about 75 m long. Highway 137 emerges from underneath the flow and heads S into the distance in the upper center of the image. Courtesy of HVO.

Several laze plumes rose along the ocean entry margin as break outs fed many small and large flows during mid-June. The largest pahoehoe breakout area was on the northern margin of the flow (figure 410). A small amount of expansion continued at the southern boundary of the flow near the coast and south of Vacationland. By 17 June, lava flowing into the ocean had built a delta of flows, rock rubble, and black sand, which was over 121 hectares (320 acres) in size. The flow front at the coast was about 2.4 km wide by 18 June. Limited spattering and small flows were also observed at fissures 16 and 18 during 13-19 June; mild spattering from fissure 15 was observed late in the day on 16 June, and incandescence and mild spattering were observed from fissure 6 on 17 June.

Figure (see Caption) Figure 410. A large breakout of lava created several laze plumes as it entered the ocean along the northern ocean entry margin of Kilauea's LERZ fissure 8 flow delta on 14 June 2018. Courtesy of HVO.

Fissure 8 lava fountains 52-70 m tall showered spatter onto the cone overnight into 19 June (figure 411). Small overflows were observed on the N side of the channel near Pohoiki Road overnight and in the morning, with one breakout spreading slowly beyond the flow boundary. Field crews on the ground near fissure 8 midday on 19 June observed a still-vigorous channelized lava flow being fed by fountains at the vent. Standing waves were visible within the channel and cascades/rapids were visible near the base of the 50-m-high cone. The maximum flow velocity in the channel was measured at 28 km/hour. During the morning overflight, several small overflows could be seen along the channel margins. The flow of lava was faster in the center of the channel and decreased in speed toward the margins where friction with the channel walls increased. A small, sluggish overflow along a section of Luana Street was advancing NW. Fissures 6, 15, 16 were still oozing lava and fuming.

Figure (see Caption) Figure 411. Kilauea's LERZ fissure 8 vigor increased overnight on 18-19 June 2019 with lava fountains reaching up to 60 m. Spatter continued to build up on the E flank of cone and lava flowed into the channel. Courtesy of HVO.

Activity at Halema'uma'u crater during June 2018. Throughout June intermittent explosions and earthquakes continued at Halema'uma'u crater as the summit area subsided and adjusted to the withdrawal of magma from below. Inward slumping of the rim and walls of Halema`uma`u continued in response to the persistent subsidence. A near-daily pattern of explosive events was characterized by seismicity at the summit that would gradually increase to tens of events per hour, culminating with a larger explosion, often with an energy release equivalent magnitude greater than M 5.0. Seismicity would usually then drop significantly before gradually rising until the next explosion. Ash plumes from the explosions often rose to altitudes of 2.4-4.6 km. With each explosion, Halema'uma'u crater subsided, generating fractures and down-dropped blocks within and around the crater floor, dramatically reshaping the morphology of the summit caldera in just a few weeks (figures 412 and 413).

Figure (see Caption) Figure 412. HVO scientists captured this aerial view of a much-changed Halema'uma'u during their overflight of Kilauea's summit on the afternoon of 5 June 2018. Explosions and collapses had enlarged the crater (foreground) that previously hosted a lava lake, and the far rim of Halema'uma'u had also dropped with continued summit deflation. The parking area for the former overlook (closed since early 2008 due to volcanic hazards) is to the left of the crater with small fractures trending across it. Courtesy of HVO.
Figure (see Caption) Figure 413. Explosions and collapses continued throughout June 2018, enlarging Halema'uma'u crater almost daily. In this view on 12 June (one week after the previous image (figure 412)), the scale and rate of change at the summit of Kilauea was clear. The obvious flat surface (center) was the former Halema'uma'u crater floor, which had subsided at least 100 m during the previous two weeks. Large ground cracks circumferential to the crater rim can be seen cutting across the parking lot (left) for the former Halema'uma'u visitor overlook, which is beginning to fall into the crater. The deepest part of Halema'uma'u (foreground) was about 300 m below the crater rim. Courtesy of HVO.

Overnight on 10-11 June there were two explosions at the summit separated by about four hours, followed by a decrease in seismicity. Video recorded during a UAS (Unmanned Aircraft Systems) flight HVO on 24 June 2018 revealed details of the extensive changes occurring within Halema'uma'u crater since explosive eruptions of ash and gas and ongoing wall collapse had begun in mid-May. Clearly visible were the steep crater walls that continued to slump inward and downward with ongoing subsidence. The deepest part of Halema'uma'u had dropped over 400 m below the caldera floor. There were two obvious flat surfaces within the crater that had slumped downward as nearly intact blocks; the shallower one was the former caldera floor and the deeper one was the former Halema'uma'u crater floor. HVO reduced the Aviation Color code from Red to Orange on 24 June, citing the fact that the episodic plumes from the summit rarely exceeded 3 km altitude where the might pose a risk to aviation.

Activity on the Lower East Rift Zone during 20-30 June 2018. For the remainder of June, vigorous fountaining nearly 60 m high from fissure 8 fed the established channel that transported incandescent lava to the ocean at the Kapoho coastline where several entries were active (figure 414). The largest entry area was at the S end of the flow front, but the locations of the ocean entry points migrated back and forth along the delta over time. Periodic overflows from the channel were short-lived and produced sluggish pahoehoe flows that only traveled a few meters (figure 415). Minor effusion of lava was observed from fissures 6, 15, and 16. Activity ceased at fissure 6 by 22 June. During an overflight in the early morning of 23 June, only incandescence was noted at fissure 22.

Figure (see Caption) Figure 414. Lava from Kilauea's LERZ fissure 8 remained incandescent on its 13-km-long journey to the ocean in an open channel during the last part of June 2018. Plumes of steam and laze at the ocean entry were visible in the upper right of the left image on 20 June 2018. Small streams of lava entered the ocean across a broad area the same day, shown by the multiple white steam and laze plumes. Lava had added about 155 hectares (380 acres) of new land by 20 June 2018. Courtesy of HVO.
Figure (see Caption) Figure 415. Sluggish pahoehoe briefly spilled over a section the levee along the well-established channel of Kilauea's LERZ fissure 8 lava flow on 20 June 2018. The overflows generally traveled short distances measured in meters. Geologists tracked the extent of overflows and looked for potential areas of weakness and seepages along the sides of the perched channel in order to assess potential breakouts from the channel. The small blades of grass in the lower left suggest the scale of this photo is about one meter across. Courtesy of HVO.

The spatter cone grew to 55 m tall by 24 June, after which the lava fountains only occasionally rose above its highest point. Geologists measured lava entering the channel traveling as fast as 30 km/hour. By 25 June, most of the lava was entering the sea on the southern side of the flow front along a 1-km wide area marked by billowing laze plumes, although the lava front extended for more than 3 km along the coast (figure 416). Beginning on 27 June geologists observed fresh lava oozing at several points along the northern margin of the flow field in the area of the Kapoho Beach Lots. By then, the lava channel had crusted over about 0.8 km inland of the ocean entry; lava was moving beneath the crust and into the still-molten interior of earlier flows before it entered the sea (figure 417). The same day, small overflows on both sides of the channel occurred in the uppermost part of channel, but none of these overflows extended past the existing flow field (figure 418).

Figure (see Caption) Figure 416. Most of the lava from Kilauea's LERZ fissure 8 flow was entering the ocean at the southern edge of the delta flow field on 25 June 2018, although the whole delta extended for more than 3 km along the coast. Dark red areas were active flows, shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. Courtesy of HVO.
Figure (see Caption) Figure 417. At Kilauea's LERZ fissure 8 delta, small breakouts were observed in the morning of 27 June 2018 in the area of Kapoho Beach Lots on the N flank of the flow delta near the ocean. The lava channel had crusted over about 0.8 km inland of the ocean entry; lava was moving beneath the crust and into the still-molten interior of earlier flows before it entered the sea. This thermal map shows the fissure system and lava flows as of 0600 on 27 June 2018. The fountain at fissure 8 remained active, with the lava flow entering the ocean at Kapoho. Very small, short flows were observed near fissure 22. The black and white area is the extent of the thermal map. Temperature in the image is displayed as gray-scale values, with the brightest pixels indicating the hottest areas. The map was constructed by stitching many overlapping oblique images collected by a handheld thermal camera during a helicopter overflight of the flow field. The base is a copyrighted color satellite image (used with permission) provided by Digital Globe. Courtesy of HVO.
Figure (see Caption) Figure 418. A small overflow from the lava channel of Kilauea's LERZ fissure 8 flow, visible on the left, was recorded by an Unmanned Aircraft System (UAS) flight. Small overflows on both sides of the channel occurred shortly after midnight on 27 June 2018 in the uppermost part of channel. None of these overflows extended past the existing flow field. The 'arm' is likely about 10 m long. Image by the U.S. Geological Survey and Office of Aviation Services, Department of the Interior. Courtesy of HVO.

The northern margin of the ocean entry flow field was the most active during the last few days of the month with lava entering the sea over a broad area (figure 419). A few burning areas were also observed on the S side of the flow and W of Highway 137. Field crews were able to make rough estimates of the velocity of the flow in the channel by timing the large blocks in the flow as they passed by islands within the channel and known points along the edges (figure 420). Volcanic gas emissions were very high from fissure 8 eruptions throughout June 2018 causing trade winds to bring Vog (volcanic air pollution, a hazy mixture of SO2 gas and aerosols) to the central, south, and western parts of the Island of Hawaii on many occasions. Substantial SO2 plumes were recorded daily (figure 421).

Figure (see Caption) Figure 419. At the Kapoho coast, lava from Kilauea's LERZ fissure 8 entered the ocean over a broad area along the northern margin of the flow field on 30 June 2018. Courtesy of HVO.
Figure (see Caption) Figure 420. Lava flowed rapidly around islands in the lava channel of Kilauea's LERZ fissure 8 flow on 30 June 2018. The direction of flow was from the upper right to lower left. Field crews were able to make a rough calculation of velocity by timing large blocks as they passed between two landmarks that were a known distance apart. Courtesy of HVO.
Figure (see Caption) Figure 421. Volcanic gas emissions were very high from Kilauea's LERZ fissure 8 eruptions throughout June 2018 causing trade winds to bring VOG to the central, south, and western parts of the Island of Hawaii on many occasions. Large plumes of SO2 were identified with satellite instruments on numerous days of the month; 4, 13, 20, and 22 June, shown here, were just a few of the days where large SO2 plumes drifted SW on trade winds across the southern and western margins of the island of Hawaii. The island of Hawaii is 150 km from the N tip to the S tip. Courtesy of NASA Goddard Space Flight Center.

Thermal observations during May-June 2018. The MODVOLC thermal alert system captures infrared data from satellite instruments (MODIS) that indicate the location of hot-spots around the planet. The data collected for Kilauea for May and June 2018 clearly indicated the size and scope of the eruptive episode (figures 422 and 423). At the end of April, infrared data indicated strong activity at Halema'uma'u and weak activity from the episode 61g flow that originated on the flank of Pu'u 'O'o (figure 422). The first MODVOLC thermal alert of activity on the LERZ appeared 6 May; even though the lava lake had begun to drop, there was still a strong thermal signal at Halema'uma'u that day as well. As the eruption progressed during May, the increasing size of the effusive activity that included lava flows reaching the SE coast was apparent.

Figure (see Caption) Figure 422. Selected maps showing MODVOLC thermal alert pixels at Kilauea for May 2018. An overflowing lava lake at Halema'uma'u and the episode 61g flow that originated on the flank of Pu'u 'O'o were captured in the infrared data in late April. The first MODVOLC alert on the LERZ appeared in the first week of May, and continued to grow throughout the month; the signal at Halema'uma'u was gone by mid-May. Courtesy of MODVOLC.

By early June, just a few days after the flow-volume increase on the LERZ from the channel emerging from fissure 8, the new pattern of heat flow to the N and NE around Kapoho Cone was recorded in the satellite data. The growing delta filling Kapoho Bay generated a strong infrared signal throughout the month. Although the fissure 8 flow was essentially unchanged in its thermal output on 22 and 23 June based on ground observations, the infrared data for those two days was significantly different, likely reflecting atmospheric conditions that blocked satellite views. In spite of this, the general nature of the flow activity is still clear in the data. By the end of June, the extent of the MODVOLC thermal alert pixels clearly indicated the robust nature of the continuing eruption.

Figure (see Caption) Figure 423. In early June 2018 the new pattern of heat flow to the N and NE around Kapoho Cone was recorded in satellite thermal data. The growing delta filling Kapoho Bay generated a strong infrared signal throughout the month. A change in meteoric conditions, not a change in flow activity, was likely responsible for the change in signal on 22 and 23 June. By the end of June, the extent of the MODVOLC thermal alert pixels clearly indicated the robust nature of the continuing eruption.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: http://hvo.wr.usgs.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/); 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/).

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Natural Science Event Bulletin - Volume 01, Number 04 (January 1976)

Managing Editor: David Squires

Augustine (United States)

Explosive activity on 22 January precedes major eruptions

Colima (Mexico)

Lava flows continue

Kilauea (United States)

Slow inflation and two earthquakes

Pavlof (United States)

Intermittent steam and ash emissions

Reventador (Ecuador)

Explosive eruption begins on 4 January; lava flows enter the jungle

Shishaldin (United States)

White steam again seen during clear weather



Augustine (United States) — January 1976 Citation iconCite this Report

Augustine

United States

59.363°N, 153.43°W; summit elev. 1252 m

All times are local (unless otherwise noted)


Explosive activity on 22 January precedes major eruptions

Explosive activity, as measured by University of Alaska Geophysical Institute infrasonic stations, began on the afternoon of 22 January, and at 0745 on 23 January the first major ash eruption occurred. A second major explosion and ashfall followed at 1645 that afternoon. At least five major eruptions took place during the following 3 days. Ash clouds penetrated the tropopause, reaching heights of 14 km as measured by ANR height-finding radars. A light dusting of ash (~1.5 mm) fell at Anchorage. Ash also fell at Iliamna, Homer, and Seldovia, Alaska.

Microearthquake swarms and occasional explosions have been noted on the volcano since mid October. Island seismographs, presumably damaged by premonitory activity, stopped telemetering earthquake data about one week prior to the main eruptions. A strong increase of earthquake activity was recorded, however, on 22 January, on the University of Alaska and USGS seismic stations located on the mainland, W of the island volcano. Intense swarm activity accompanied the main eruptive phase. Lahars, mudflows and pyroclastic flows descended the flanks and some reached the sea. Vent-clearing and subsequent explosions removed much of the 1963-64 dome, resulting in a crater breached to the N.

The Burr Point Research Station (NW tip of the island) was severely damaged by blast and thermal effects from one or more nuées ardentes, and scoria and ashfall. Temperatures greater than 400°C were measured 9 feet below the surface of a pyroclastic flow E of the research station.

Chemical and petrographic analyses of the first 23 January ashfall, sampled at Seldovia and Iliamna, indicates that initial melt accompanying vent breaching explosions was dacitic andesite as documented in the following partial chemical analysis: SiO2 = 63.8%, Fe2O3 = 2.1%, FeO = 2.0%, MgO = 2.1%, CaO = 5.1%, Na2O = 3.9%, K2O = 1.3%. A relatively quiet period extended from 27 January to the end of the month.

Geologic Background. Augustine volcano, rising above Kamishak Bay in the southern Cook Inlet about 290 km SW of Anchorage, is the most active volcano of the eastern Aleutian arc. It consists of a complex of overlapping summit lava domes surrounded by an apron of volcaniclastic debris that descends to the sea on all sides. Few lava flows are exposed; the flanks consist mainly of debris-avalanche and pyroclastic-flow deposits formed by repeated collapse and regrowth of the volcano's summit. The latest episode of edifice collapse occurred during Augustine's largest historical eruption in 1883; subsequent dome growth has restored the volcano to a height comparable to that prior to 1883. The oldest dated volcanic rocks on Augustine are more than 40,000 years old. At least 11 large debris avalanches have reached the sea during the past 1800-2000 years, and five major pumiceous tephras have been erupted during this interval. Historical eruptions have typically consisted of explosive activity with emplacement of pumiceous pyroclastic-flow deposits followed by lava dome extrusion with associated block-and-ash flows.

Information Contacts: R. Forbes, Univ. of Alaska; P. Sventek, USAF, Cold Bay.


Colima (Mexico) — January 1976 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


Lava flows continue

By the end of December the E lava flow had descended the flank of the cone, reaching the vegetation and a ravine at the base. The flow advanced about 2,500 m in 60 days. On 28 January 1976 two new lava flows started to develop at the S and W sides of the dome [but see 1:6].

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: S. De la Cruz-Reyna, Universidad Nacional Autonoma de México (UNAM).


Kilauea (United States) — January 1976 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Slow inflation and two earthquakes

The volcano has been inflating slowly since the 29 November eruption. Two earthquakes, one of magnitude 4.0, shook Kilauea on 11 January, the largest events associated with the volcano in several months.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: R. Tilling, HVO.


Pavlof (United States) — January 1976 Citation iconCite this Report

Pavlof

United States

55.417°N, 161.894°W; summit elev. 2493 m

All times are local (unless otherwise noted)


Intermittent steam and ash emissions

3-4 January: intermittent steam, grey smoke, and black ash. 5 January: black ash. 11-12 January: steam. At 2130 on 11 January a pilot reported the volcano erupting red-hot mud/lava up to 300 meters above the cone. 17 January: grey smoke. 22 January: steam. 24-25 January: grey smoke and steam. 29-30 January: constant steam. 31 January: very intermittent steam.

Geologic Background. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Information Contacts: P. Sventek, USAF, Cold Bay.


Reventador (Ecuador) — January 1976 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Explosive eruption begins on 4 January; lava flows enter the jungle

An explosive eruption began during the early morning of 4 January. At dawn an ash column 1 km high was observed. Fine ash was carried W and SW over the Andes, dusting Quito through 10 January. Bombs blown 100 m vertically from the crater were large enough to be seen by the naked eye from a distance of 3 km. Strange seismic signatures, detected 90 km away (at Quito) and attributed to Reventador, began at 0115 on 4 January and continued until 0900 on 9 January. A portable seismograph 10 km from the cone measured continuous harmonic tremor.

Two lava flows descended from the breached crater and divided into three lobes at the base of the cone. During the first 40 hours flows traveled approximately 1.5 km E at 37 m/hour. By 9 January the three lobes had traveled 2.5 km and were advancing approximately 5 m/hour over lahar deposits and jungle. As of 27 January the lava flows had stopped, but infrequent explosive activity, including nuées ardentes, was continuing. The continual ash column had terminated by 25 January. The flows were a black basaltic andesite with olivine, augite, hypersthene, and oxyhornblende.

Reventador had similar eruptions in July 1972 and November 1973. When last visited before the current eruption, on 10 December 1975, it was producing a large steam column.

Further Reference. Hall, M.L., 1980, El Reventador, Ecuador: un volcán activo de los Andes Septentrionales: Revista Politécnica, v. 5, no. 2, p. 123-136.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: M. Hall, Escuela Politécnica, Quito.


Shishaldin (United States) — January 1976 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


White steam again seen during clear weather

White steam was noted at Shishaldin on 4-5, 11-12, 29-30, and 31 January.

Geologic Background. The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: P. Sventek, USAF, Cold Bay.

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 (NSEB 22:08) False Report of Mount Pinokis Eruption

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (NSEB 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/).