Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A new period of explosive activity that began in November 2016 has been characterized by pulses of ash emissions with some plumes exceeding 10 km altitude, thermal anomalies, and significant SO₂ plumes. Ash emissions and high levels of SO₂ continued each week during December 2019-May 2020. The Observatorio Vulcanologico INGEMMET (OVI) reports weekly on numbers of daily explosions, ash plume heights and directions of drift, seismicity, and other activity. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued three or four daily reports of ongoing ash emissions at Sabancaya throughout the period.

The dome inside the summit crater continued to grow throughout this period, along with nearly constant ash, gas, and steam emissions; the average number of daily explosions ranged from 4 to 29. Ash and gas plume heights rose 1,800-3,800 m above the summit crater, and multiple communities around the volcano reported ashfall every month (table 6). Sulfur dioxide emissions were notably high and recorded daily with the TROPOMI satellite instrument (figure 75). Thermal activity declined during December 2019 from levels earlier in the year but remained steady and increased in both frequency and intensity during April and May 2020 (figure 76). Infrared satellite images indicated that the primary heat source throughout the period was from the dome inside the summit crater (figure 77).

Table 6. Persistent activity at Sabancaya during December 2019-May 2020 included multiple daily explosions with ash plumes that rose several kilometers above the summit and drifted in many directions; this resulted in ashfall in communities within 30 km of the volcano. Satellite instruments recorded SO₂ emissions daily. Data courtesy of OVI-INGEMMET.

Figure 75. Sulfur dioxide anomalies were captured daily from Sabancaya during December 2019-May 2020 by the TROPOMI instrument on the Sentinel-5P satellite. Some of the largest SO2 plumes are shown here with dates listed in the information at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 76. Thermal activity at Sabancaya declined during December 2019 from levels earlier in the year but remained steady and increased slightly in frequency and intensity during April and May 2020, according to the MIROVA graph of Log Radiative Power from 23 June 2019 through May 2020. Courtesy of MIROVA.

Figure 77. Sentinel-2 satellite imagery of Sabancaya confirmed the frequent ash emissions and ongoing thermal activity from the dome inside the summit crater during December 2019-May 2020. Top row (left to right): On 6 December 2019 a large plume of steam and ash drifted N from the summit. On 16 December 2019 a thermal anomaly encircled the dome inside the summit caldera while gas and possible ash drifted NW. On 14 April 2020 a very similar pattern persisted inside the crater. Bottom row (left to right): On 19 April an ash plume was clearly visible above dense cloud cover. On 24 May the infrared glow around the dome remained strong; a diffuse plume drifted W. A large plume of ash and steam drifted SE from the summit on 29 May. Infrared images use Atmospheric penetration rendering (bands 12, 11, 8a), other images use Natural Color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

The average number of daily explosions during December 2019 decreased from a high of 16 the first week of the month to a low of five during the last week. Six pyroclastic flows occurred on 10 December (figure 78). Tremors were associated with gas-and-ash emissions for most of the month. Ashfall was reported in Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, and Chivay during the first week of the month, and in Huambo and Cabanaconde during the second week (figure 79). Inflation of the volcano was measured throughout the month. SO₂ flux was measured by OVI as ranging from 2,500 to 4,300 tons per day.

Figure 78. Multiple daily explosions at Sabancaya produced ash plumes that rose several kilometers above the summit. Left image is from 5 December and right image is from 11 December 2019. Note pyroclastic flows to the right of the crater on 11 December. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-49-2019/INGEMMET Semana del 2 al 8 de diciembre de 2019 and RSSAB-50-2019/INGEMMET Semana del 9 al 15 de diciembre de 2019).

Figure 79. Communities to the N and W of Sabancaya recorded ashfall from the volcano the first week of December and also every month during December 2019-May 2020. The red zone is the area where access is prohibited (about a 12-km radius from the crater). Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

During January and February 2020 the number of daily explosions averaged 4-20. Ash plumes rose as high as 3.4 km above the summit (figure 80) and drifted up to 30 km in multiple directions. Ashfall was reported in Chivay, Yanque, and Achoma on 8 January, and in Huambo on 25 February. Sulfur dioxide flux ranged from a low of 1,200 t/d on 29 February to a high of 8,200 t/d on 28 January. Inflation of the edifice was measured during January; deformation changed to deflation in early February but then returned to inflation by the end of the month.

Figure 80. Ash plumes rose from Sabancaya every day during January and February 2020. Left: 11 January. Right: 28 February. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-02-2020/INGEMMET Semana del 06 al 12 de enero del 2020 and RSSAB-09-2020/INGEMMET Semana del 24 de febrero al 01 de marzo del 2020).

Explosions continued during March and April 2020, averaging 8-29 per day. Explosions appeared to come from multiple vents on 11 March (figure 81). Ash plumes rose 3 km above the summit during the first week of March and again the first week of April; they were lower during the other weeks. Ashfall was reported in Madrigal, Lari, and Pinchollo on 27 March and 5 April. On 17 April ashfall was reported in Maca, Ichupampa, Yanque, Chivay, Coporaque, and Achoma. Sulfur dioxide flux ranged from 1,900 t/d on 5 March to 10,700 t/d on 30 March. Inflation at depth continued throughout March and April with 10 +/- 4 mm recorded between 21 and 26 April. Similar activity continued during May 2020; explosions averaged 6-16 per day (figure 82). Ashfall was reported on 6 May in Chivay, Achoma, Maca, Lari, Madrigal, and Pinchollo; heavy ashfall was reported in Achoma on 12 May. Additional ashfall was reported in Achoma, Maca, Madrigal, and Lari on 23 May.

Figure 81. Explosions at Sabancaya on 11 March 2020 appeared to originate simultaneously from two different vents (left). The plume on 12 April was measured at about 2,500 m above the summit. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-11-2020/INGEMMET Semana del 9 al 15 de marzo del 2020 and RSSAB-15-2020/INGEMMET Semana del 6 al 12 de abril del 2020).

Figure 82. Explosions dense with ash continued during May 2020 at Sabancaya. On 11 and 29 May 2020 ash plumes rose from the summit and drifted as far as 30 km before dissipating. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya , RSSAB-20-2020/INGEMMET Semana del 11 al 17 de mayo del 2020 and RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

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); 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); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The eruption at Sheveluch has continued for more than 20 years, with strong explosions that have produced ash plumes, lava dome growth, hot avalanches, numerous thermal anomalies, and strong fumarolic activity (BGVN 44:05). During this time, there have been periods of greater or lesser activity. The most recent period of increased activity began in December 2018 and continued through October 2019 (BGVN 44:11). This report covers activity between November 2019 to April 2020, a period during which activity waned. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT) and Tokyo Volcanic Ash Advisory Center (VAAC).

During the reporting period, KVERT noted that lava dome growth continued, accompanied by incandescence of the dome blocks and hot avalanches. Strong fumarolic activity was also present (figure 53). However, the overall eruption intensity waned. Ash plumes sometimes rose to 10 km altitude and drifted downwind over 600 km (table 14). The Aviation Color Code (ACC) remained at Orange (the second highest level on a four-color scale), except for 3 November when it was raised briefly to Red (the highest level).

Figure 53. Fumarolic activity of Sheveluch’s lava dome on 24 January 2020. Photo by Y. Demyanchuk; courtesy of KVERT.

Table 14. Explosions and ash plumes at Sheveluch during November 2019-April 2020. Dates and times are UTC, not local. Data courtesy of KVERT and the Tokyo VAAC.

KVERT reported thermal anomalies over the volcano every day, except for 25-26 January, when clouds obscured observations. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm recorded hotspots on 10 days in November, 13 days in December, nine days in January, eight days in both February and March, and five days in April. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month, almost all of which were of moderate radiative power (figure 54).

Figure 54. Thermal anomalies at Sheveluch continued at elevated levels during November 2019-April 2020, as seen on this MIROVA Log Radiative Power graph for July 2019-April 2020. Courtesy of MIROVA.

High sulfur dioxide levels were occasionally recorded just above or in the close vicinity of Sheveluch by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite, but very little drift was observed.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); 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); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

The ongoing eruption at Dukono is characterized by frequent explosions that send ash plumes to about 1.5-3 km altitude (0.3-1.8 km above the summit), although a few have risen higher. This type of typical activity (figure 13) continued through at least March 2020. The ash plume data below (table 21) were primarily provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC). During the reporting period of October 2019-March 2020, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to remain outside of the 2-km exclusion zone.

Table 21. Monthly summary of reported ash plumes from Dukono for October 2019-March 2020. The direction of drift for the ash plume through each month was highly variable; notable plume drift each month was only indicated in the table if at least two weekly reports were consistent. Data courtesy of the Darwin VAAC and PVMBG.

Figure 13.Satellite image of Dukono from Sentinel-2 on 12 November 2019, showing an ash plume drifting E. Image uses natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During the reporting period, high levels of sulfur dioxide were only recorded above or near the volcano during 30-31 October and 4 November 2019. High levels were recorded by the Ozone Mapping and Profiler Suite (OMPS) instrument aboard the Suomi National Polar-orbiting Partnership (NPP) satellite on 30 October 2019, in a plume drifting E. The next day high levels were also recorded by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite on 31 October (figure 14) and 4 November 2019, in plumes drifting SE and NE, respectively.

Figure 14. Sulfur dioxide emission on 31 October 2019 drifting E, probably from Dukono, as recorded by the TROPOMI instrument aboard the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Mount Etna is a stratovolcano located on the island of Sicily, Italy, with historical eruptions that date back 3,500 years. The most recent eruptive period began in September 2013 and has continued through March 2020. Activity is characterized by Strombolian explosions, lava flows, and ash plumes that commonly occur from the summit area, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. This reporting period covers information from October 2019 through March 2020 and includes frequent explosions and ash plumes. The primary source of information comes from the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during October 2019-March 2020. Strombolian activity and gas-and-steam and ash emissions were frequently observed at Etna throughout the entire reporting period, according to INGV and Toulouse VAAC notices. Activity was largely located within the main cone (Voragine-Bocca Nuova complex), the Northeast Crater (NEC), and the New Southeast Crater (NSEC). On 1, 17, and 19 October, ash plumes rose to a maximum altitude of 5 km. Due to constant Strombolian explosions, ground observations showed that a scoria cone located on the floor of the VOR Crater had begun to grow in late November and again in late January 2020. A lava flow was first detected on 6 December at the base of the scoria cone in the VOR Crater, which traveled toward the adjacent BN Crater. Additional lava flows were observed intermittently throughout the reporting period in the same crater. On 13 March, another small scoria cone had formed in the main VOR-BN complex due to Strombolian explosions.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity varying in power from 22 June 2019 to March 2020 (figure 286). The power and frequency of these thermal anomalies significantly decreased between August to mid-September. The pulse of activity in mid-September reflected a lava flow from the VOR Crater (BGVN 44:10). By late October through November, thermal anomalies were relatively weaker and less frequent. The next pulse in thermal activity reflected in the MIROVA graph occurred in early December, followed by another shortly after in early January, both of which were due to new lava flows from the VOR Crater. After 9 January the thermal anomalies remained frequent and strong; active lava flows continued through March accompanied by Strombolian explosions, gas-and-steam, SO2, and ash emissions. The most recent distinct pulse in thermal activity was seen in mid-March; on 13 March, another lava flow formed, accompanied by an increase in seismicity. This lava flow, like the previous ones, also originated in the VOR Crater and traveled W toward the BN Crater.

Figure 286. Multiple episodes of varying activity at Etna from 22 June 2019 through March 2020 were reflected in the MIROVA thermal energy data (Log Radiative Power). Courtesy of MIROVA.

Activity during October-December 2019. During October 2019, VONA (Volcano Observatory Notice for Aviation) notices issued by INGV reported ash plumes rose to a maximum altitude of 5 km on 1, 17, and 19 October. Strombolian explosions occurred frequently. Explosions were detected primarily in the VOR-BN Craters, ejecting coarse pyroclastic material that fell back into the crater area and occasionally rising above the crater rim. Ash emissions rose from the VOR-BN and NEC while intense gas-and-steam emissions were observed in the NSEC (figure 287). Between 10-12 and 14-20 October fine ashfall was observed in Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. In addition to these ash emissions, the explosive Strombolian activity contributed to significant SO2 plumes that drifted in different directions (figure 288).

Figure 287. Webcam images of ash emissions from the NE Crater at Etna from the a) CUAD (Catania) webcam on 10 October 2019; b) Milo webcam on 11 October 2019; c) Milo webcam on 12 October 2019; d) M.te Cagliato webcam on 13 October 2019. Courtesy of INGV (Report 42/2019, ETNA, Bollettino Settimanale, 07/10/2019 - 13/10/2019, data emissione 15/10/2019).

Figure 288. Strombolian activity at Etna contributed to significant SO2 plumes that drifted in multiple directions during the intermittent explosions in October 2019. Top left: 1 October 2019. Top right: 2 October 2019. Middle left: 15 October 2019. Middle right: 18 October 2019. Bottom left: 13 November 2019. Bottom right: 1 December 2019. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The INGV weekly bulletin covering activity between 25 October and 1 November 2019 reported that Strombolian explosions occurred at intervals of 5-10 minutes from within the VOR-BN and NEC, ejecting incandescent material above the crater rim, accompanied by modest ash emissions. In addition, gas-and-steam emissions were observed from all the summit craters. Field observations showed the cone in the crater floor of VOR that began to grow in mid-September 2019 had continued to grow throughout the month. During the week of 4-10 November, Strombolian activity within the Bocca Nuova Crater was accompanied by gas-and-steam emissions. The explosions in the VOR Crater occasionally ejected incandescent ejecta above the crater rim (figures 289 and 290). For the remainder of the month Strombolian explosions continued in the VOR-BN and NEC, producing sporadic ash emissions. Isolated and discontinuous explosions in the New Southeast Crater (NSEC) also produced fine ash, though gas-and-steam emissions still dominated the activity at this crater. Additionally, the explosions from these summit craters were frequently accompanied by strong SO2 emissions that drifted in different directions as discrete plumes.

Figure 289. Photo of Strombolian activity and crater incandescence in the Voragine Crater at Etna on 15 November 2019. Photo by B. Behncke, taken by Tremestieri Etneo. Courtesy of INGV (Report 47/2019, ETNA, Bollettino Settimanale, 11/11/2019 - 17/11/2019, data emissione 19/11/2019).

Figure 290. Webcam images of summit crater activity during 26-29 November and 1 December 2019 at Etna. a) image recorded by the high-resolution camera on Montagnola (EMOV); b) and c) webcam images taken from Tremestieri Etneo on the southern slope of Etna showing summit incandescence; d) image recorded by the thermal camera on Montagnola (EMOT) showing summit incandescence at the NSEC. Courtesy of INGV (Report 49/2019, ETNA, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Frequent Strombolian explosions continued through December 2019 within the VOR-BN, NEC, and NSEC Craters with sporadic ash emissions observed in the VOR-BN and NEC. On 6 December, Strombolian explosions increased in the NSEC; webcam images showed incandescent pyroclastic material ejected above the crater rim. On the morning of 6 December a lava flow was observed from the base of the scoria cone in the VOR Crater that traveled toward the adjacent Bocca Nuova Crater. INGV reported that a new vent opened on the side of the saddle cone (NSEC) on 11 December and produced explosions until 14 December.

Activity during January-March 2020. On 9 January 2020 an aerial flight organized by RAI Linea Bianca and the state police showed the VOR Crater continuing to produce lava that was flowing over the crater rim into the BN Crater with some explosive activity in the scoria cone. Explosive Strombolian activity produced strong and distinct SO2 plumes (figure 291) and ash emissions through March, according to the weekly INGV reports, VONA notices, and satellite imagery. Several ash emissions during 21-22 January rose from the vent that opened on 11 December. According to INGV’s weekly bulletin for 21-26 January, the scoria cone in the VOR crater produced Strombolian explosions that increased in frequency and contributed to rapid cone growth, particularly the N part of the cone. Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2) (figure 292). The NEC had discontinuous Strombolian activity and periodic, diffuse ash emissions.

Figure 291. Distinct SO2 plumes drifting in multiple directions from Etna were visible in satellite imagery as Strombolian activity continued through March 2020. Top left: 21 January 2020. Top right: 2 February 2020. Bottom left: 10 March 2020. Bottom right: 19 March 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 292. a) A map of the lava field at Etna showing cooled flows (yellow) and active flows (red). The base of the scoria cone is outlined in black while the crater rim is outlined in red. b) Thermal image of the Bocca Nuova and Voragine Craters. The bright orange is the warmest temperature measure in the flow. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

Strombolian explosions continued into February 2020, accompanied by ash emissions and lava flows from the previous months (figure 293). During 17-23 February, INGV reported that some subsidence was observed in the central portion of the Bocca Nuova Crater. During 24 February to 1 March, the Strombolian explosions ejected lava from the VOR Crater up to 150-200 m above the vent as bombs fell on the W edge of the VOR crater rim (figure 294). Lava flows continued to move into the W part of the Bocca Nuova Crater.

Figure 293. Webcam images of A) Strombolian activity and B) effusive activity fed by the scoria cone grown inside the VOR Crater at Etna taken on 1 February 2020. C) Thermal image of the lava field produced by the VOR Crater taken by L. Lodato on 3 February (bottom left). Image of BN-1 taken by F. Ciancitto on 3 February in the summit area (bottom right). Courtesy of INGV; Report 06/2020, ETNA, Bollettino Settimanale, 27/01/2020 - 02/02/2020, data emissione 04/02/2020 (top) and Report 07/2020, ETNA, Bollettino Settimanale, 03/02/2020 - 09/02/2020, data emissione 11/02/2020 (bottom).

Figure 294. Photos of the VOR intra-crater scoria cone at Etna: a) Strombolian activity resumed on 25 February 2020 from the SW edge of BN taken by B. Behncke; b) weak Strombolian activity from the vent at the base N of the cone on 29 February 2020 from the W edge of VOR taken by V. Greco; c) old vent present at the base N of the cone, taken on 17 February 2020 from the E edge of VOR taken by B. Behncke; d) view of the flank of the cone, taken on 24 February 2020 from the W edge of VOR taken by F. Ciancitto. Courtesy of INGV (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

During 9-15 March 2020 Strombolian activity was detected in the VOR Crater while discontinuous ash emissions rose from the NEC and NSEC. Bombs were found in the N saddle between the VOR and NSEC craters. On 9 March, a small scoria cone that had formed in the Bocca Nuova Crater and was ejecting bombs and lava tens of meters above the S crater rim. The lava flow from the VOR Crater was no longer advancing. A third scoria cone had formed on 13 March NE in the main VOR-BN complex due to the Strombolian explosions on 29 February. Another lava flow formed on 13 March, accompanied by an increase in seismicity. The weekly report for 16-22 March reported Strombolian activity detected in the VOR Crater and gas-and-steam and rare ash emissions observed in the NEC and NSEC (figure 295). Explosions in the Bocca Nuova Crater ejected spatter and bombs 100 m high.

Figure 295. Map of the summit crater area of Etna showing the active vents and lava flows during 16-22 March 2020. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Courtesy of INGV (Report 13/2020, ETNA, Bollettino Settimanale, 16/03/2020 - 22/03/2020, data emissione 24/03/2020).

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

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris, Image at https://twitter.com/etnaboris/status/1183640328760414209/photo/1).

Merapi is a highly active stratovolcano located in Indonesia, just north of the city of Yogyakarta. The current eruption episode began in May 2018 and was characterized by phreatic explosions, ash plumes, block avalanches, and a newly active lava dome at the summit. This reporting period updates information from October 2019-March 2020 that includes explosions, pyroclastic flows, ash plumes, and ashfall. The primary reporting source of activity comes from Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG, the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG) and Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

Some ongoing lava dome growth continued in October 2019 in the NE-SW direction measuring 100 m in length, 30 m in width, and 20 m in depth. Gas-and-steam emissions were frequent, reaching a maximum height of 700 m above the crater on 31 October. An explosion at 1631 on 14 October removed the NE-SW trending section of the lava dome and produced an ash plume that rose 3 km above the crater and extended SW for about 2 km (figures 90 and 91). The plume resulted in ashfall as far as 25 km to the SW. According to a Darwin VAAC notice, a thermal hotspot was detected in HIMAWARI-8 satellite imagery. A pyroclastic flow associated with the eruption traveled down the SW flank in the Gendol drainage. During 14-20 October lava flows from the crater generated block-and-ash flows that traveled 1 km SW, according to BPPTKG.

Figure 90. An ash plume rising 3 km above Merapi on 14 October 2019.

Figure 91. Webcam image of an ash plume rising above Merapi at 1733 on 14 October 2019. Courtesy of BPPTKG via Jaime S. Sincioco.

At 0621 on 9 November 2019, an eruption produced an ash plume that rose 1.5 km above the crater and drifted W. Ashfall was observed in the W region as far as 15 km from the summit in Wonolelo and Sawangan in Magelang Regency, as well as Tlogolele and Selo in Boyolali Regency. An associated pyroclastic flow traveled 2 km down the Gendol drainage on the SE flank. On 12 November aerial drone photographs were used to measure the volume of the lava dome, which was 407,000 m3. On 17 November, an eruption produced an ash plume that rose 1 km above the crater, resulting in ashfall as far as 15 km W from the summit in the Dukun District, Magelang Regency (figure 92). A pyroclastic flow accompanying the eruption traveled 1 km down the SE flank in the Gendol drainage. By 30 November low-frequency earthquakes and CO2 gas emissions had increased.

Figure 92. An ash plume rising 1 km above Merapi on 17 November 2019. Courtesy of BPPTKG.

Volcanism was relatively low from 18 November 2019 through 12 February 2020, characterized primarily by gas-and-steam emissions and intermittent volcanic earthquakes. On 4 January a pyroclastic flow was recorded by the seismic network at 2036, but it wasn’t observed due to weather conditions. On 13 February an explosion was detected at 0516, which ejected incandescent material within a 1-km radius from the summit (figure 93). Ash plumes rose 2 km above the crater and drifted NW, resulting in ashfall within 10 km, primarily S of the summit; lightning was also seen in the plume. Ash was observed in Hargobinangun, Glagaharjo, and Kepuharjo. On 19 February aerial drone photographs were used to measure the change in the lava dome after the eruption; the volume of the lava had decreased, measuring 291,000 m3.

Figure 93. Webcam image of an ash plume rising from Merapi at 0516 on 13 February 2020. Courtesy of MAGMA Indonesia and PVMBG.

An explosion on 3 March at 0522 produced an ash plume that rose 6 km above the crater (figure 94), resulting in ashfall within 10 km of the summit, primarily to the NE in the Musuk and Cepogo Boyolali sub-districts and Mriyan Village, Boyolali (3 km from the summit). A pyroclastic flow accompanied this eruption, traveling down the SSE flank less than 2 km. Explosions continued to be detected on 25 and 27-28 March, resulting in ash plumes. The eruption on 27 March at 0530 produced an ash plume that rose 5 km above the crater, causing ashfall as far as 20 km to the W in the Mungkid subdistrict, Magelang Regency, and Banyubiru Village, Dukun District, Magelang Regency. An associated pyroclastic flow descended the SSE flank, traveling as far as 2 km. The ash plume from the 28 March eruption rose 2 km above the crater, causing ashfall within 5 km from the summit in the Krinjing subdistrict primarily to the W (figure 94).

Figure 94. Images of ash plumes rising from Merapi during 3 March (left) and 28 March 2020 (right). Images courtesy of BPPTKG (left) and PVMBG (right).

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Information Contacts: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Center for Research and Development of Geological Disaster Technology (URL: http://merapi.bgl.esdm.go.id/, Twitter: @BPPTKG); Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Jamie S. Sincioco, Phillipines (Twitter: @jaimessincioco, Image at https://twitter.com/jaimessincioco/status/1227966075519635456/photo/1).

Erta Ale is a shield volcano located in Ethiopia and contains multiple active pit craters in the summit and southeastern caldera. Volcanism has been characterized by lava flows and large lava flow fields since 2017. Surficial lava flow activity continued within the southeastern caldera during November 2019 until early April 2020; source information was primarily from various satellite data.

The number of days that thermal anomalies were detected using MODIS data in MODVOLC and NASA VIIRS satellite data was notably higher in November and December 2019 (figure 96); the number of thermal anomalies in the Sentinel-2 thermal imagery was substantially lower due to the presence of cloud cover. Across all satellite data, thermal anomalies were identified for 29 days in November, followed by 30 days in December. After December 2019, the number of days thermal anomalies were detected decreased; hotspots were detected for 17 days in January 2020 and 20 days in February. By March, these thermal anomalies became rare until activity ceased. Thermal anomalies were identified during 1-4 March, with weak anomalies seen again during 26 March-8 April 2020.

Figure 96. Graph comparing the number of thermal alerts using calendar dates using MODVOLC, NASA VIIRS, and Sentinel-2 satellite data for Erta Ale during November 2019-March 2020. Data courtesy of HIGP - MODVOLC Thermal Alerts System, NASA Worldview using the “Fire and Thermal Anomalies” layer, and Sentinel Hub Playground.

MIROVA (Middle Infrared Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent strong thermal anomalies from 18 April through December 2019 (figure 97). Between early August 2019 and March 2020, these thermal signatures were detected at distances less than 5 km from the summit. In late December the thermal intensity dropped slightly before again increasing, while at the same time moving slightly closer to the summit. Thermal anomalies then became more intermittent and steadily decreased in power over the next two months.

Figure 97. Two time-series plots of thermal anomalies from Erta Ale from 18 April 2019 through 18 April 2020 as recorded by the MIROVA system. The top plot (A) shows that the thermal anomalies were consistently strong (measured in log radiative power) and occurred frequently until early January 2020 when both the power and frequency visibly declined. The lower plot (B) shows these anomalies as a function of distance from the summit, including a sudden decrease in distance (measured in kilometers) in early August 2019, reflecting a change in the location of the lava flow outbreak. A smaller distance change can be identified at the end of December 2019. Courtesy of MIROVA.

Unlike the obvious distal breakouts to the NE seen previously (BGVN 44:04 and 44:11), infrared satellite imagery during November-December 2019 showed only a small area with a thermal anomaly near the NE edge of the Southeast Caldera (figure 98). A thermal alert was seen at that location using the MODVOLC system on 28 December, but the next day it had been replaced by an anomaly about 1.5 km WSW near the N edge of the Southeast Caldera where the recent flank eruption episode had been centered between January 2017 and January 2018 (BGVN 43:04). The thermal anomaly that was detected in the summit caldera was no longer visible after 9 January 2020, based on Sentinel-2 imagery. The exact location of lava flows shifted within the same general area during January and February 2020 and was last detected by Sentinel-2 on 4 March. After about two weeks without detectable thermal activity, weak unlocated anomalies were seen in VIIRS data on 26 March and in MODIS data on the MIROVA system four times between 26 March and 8 April. No further anomalies were noted through the rest of April 2020.

Figure 98. Sentinel-2 thermal satellite imagery of Erta Ale volcanism between November 2019 and March 2020 showing small lava flow outbreaks (bright yellow-orange) just NE of the southeastern calderas. A thermal anomaly can be seen in the summit crater on 15 November and very faintly on 20 December 2019. Imagery on 19 January 2020 showed a small thermal anomaly near the N edge of the Southeast Caldera where the recent flank eruption episode had been centered between January 2017 and January 2018. The last weak thermal hotspot was detected on 4 March (bottom right). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: 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); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).

Rincón de la Vieja is a remote volcanic complex in Costa Rica containing an acid lake that has regularly generated weak phreatic explosions since 2011 (BGVN 44:08). The most recent eruptive period occurred during late March-early June 2019, primarily consisting of small phreatic explosions, minor deposits on the N crater rim, and gas-and-steam emissions. The report period of August 2019-March 2020 was characterized by similar activity, including small phreatic explosions, gas-and-steam plumes, ash and lake sediment ejecta, and volcanic tremors. The most significant activity during this time occurred on 30 January, where a phreatic explosion ejected ash and lake sediment above the crater rim, resulting in a pyroclastic flow which gradually turned into a lahar. Information for this reporting period of August 2019-March 2020 comes from the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) using weekly bulletins.

According to OVSICORI-UNA, a small hydrothermal eruption was recorded on 1 August 2019. The seismicity was low with a few long period (LP) earthquakes around 1 August and intermittent background tremor. No explosions or emissions were reported through 11 September; seismicity remained low with an occasional LP earthquake and discontinuous tremor. The summit’s extension that has been recorded since the beginning of June stopped, and no significant deformation was observed in August.

Starting again in September 2019 and continuing intermittently through the reporting period, some deformation was observed at the base of the volcano as well as near the summit, according to OVSICORI-UNA. On 12 September an eruption occurred that was followed by volcanic tremors that continued through 15 September. In addition to these tremors, vigorous sustained gas-and-steam plumes were observed. The 16 September weekly bulletin did not describe any ejecta produced as a result of this event.

During 1-3 October small phreatic eruptions were accompanied by volcanic tremors that had decreased by 5 October. In November, volcanism and seismicity were relatively low and stable; few LP earthquakes were reported. This period of low activity remained through December. At the end of November, horizontal extension was observed at the summit, which continued through the first half of January.

Small phreatic eruptions were recorded on 2, 28, and 29 January 2020, with an increase in seismicity occurring on 27 January. On 30 January at 1213 a phreatic explosion produced a gas column that rose 1,500-2,000 m above the crater, with ash and lake sediment ejected up to 100 m above the crater. A news article posted by the Universidad de Costa Rica (UCR) noted that this explosion generated pyroclastic flows that traveled down the N flank for more than 2 km from the crater. As the pyroclastic flows moved through tributary channels, lahars were generated in the Pénjamo river, Zanjonuda gorge, and Azufrosa, traveling N for 4-10 km and passing through Buenos Aires de Upala (figure 29). Seismicity after this event decreased, though there were still some intermittent tremors.

Figure 29. Photo of a lahar generated from the 30 January 2020 eruption at Rincon de la Vieja. Photo taken by Mauricio Gutiérrez, courtesy of UCR.

On 17, 24, and 25 February and 11, 17, 19, 21, and 23 March, small phreatic eruptions were detected, according to OVSICORI-UNA. Geodetic measurements observed deformation consisting of horizontal extension and inflation near the summit in February-March. By the week of 30 March, the weekly bulletin reported 2-3 small eruptions accompanied by volcanic tremors occurred daily during most days of the week. None of these eruptions produced solid ejecta, pyroclastic flows, or lahars, according to the weekly OVSICORI-UNA bulletins during February-March 2020.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

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/, https://www.facebook.com/OVSICORI/); Luis Enrique Brenes Portuguéz, University of Costa Rica, Ciudad Universitaria Rodrigo Facio Brenes, San José, San Pedro, Costa Rica (URL: https://www.ucr.ac.cr/noticias/2020/01/30/actividad-del-volcan-rincon-de-la-vieja-es-normal-segun-experto.html).

Manam is a basaltic-andesitic stratovolcano that lies 13 km off the northern coast of mainland Papua New Guinea; it has a 400-year history of recorded evidence for recurring low-level ash plumes, occasional Strombolian activity, lava flows, pyroclastic avalanches, and large ash plumes from Main and South, the two active summit craters. The current eruption, ongoing since June 2014, produced multiple large explosive eruptions during January-September 2019, including two 15-km-high ash plumes in January, repeated SO₂ plumes each month, and another 15.2 km-high ash plume in June that resulted in ashfall and evacuations of several thousand people (BGVN 44:10).

This report covers continued activity during October 2019 through March 2020. Information about Manam is primarily provided by Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM). This information is supplemented with aviation alerts from the Darwin Volcanic Ash Advisory Center (VAAC). MODIS thermal anomaly satellite data is recorded by the University of Hawai'i's MODVOLC thermal alert recording system, and the Italian MIROVA project; sulfur dioxide monitoring is done by instruments on satellites managed by NASA's Goddard Space Flight Center. Satellite imagery provided by the Sentinel Hub Playground is also a valuable resource for information about this remote location.

A few modest explosions with ash emissions were reported in early October and early November 2019, and then not again until late March 2020. Although there was little explosive activity during the period, thermal anomalies were recorded intermittently, with low to moderate activity almost every month, as seen in the MODIS data from MIROVA (figure 71) and also in satellite imagery. Sulfur dioxide emissions persisted throughout the period producing emissions greater than 2.0 Dobson Units that were recorded in satellite data 3-13 days each month.

Figure 71. MIROVA thermal anomaly data for Manam from 17 June 2019 through March 2020 indicate continued low and moderate level thermal activity each month from August 2019 through February 2020, after a period of increased activity in June and early July 2019. Courtesy of MIROVA.

The Darwin VAAC reported an ash plume in visible satellite imagery moving NW at 3.1 km altitude on 2 October 2019. Weak ash emissions were observed drifting N for the next two days along with an IR anomaly at the summit. RVO reported incandescence at night during the first week of October. Visitors to the summit on 18 October 2019 recorded steam and fumarolic activity at both of the summit craters (figure 72) and recent avalanche debris on the steep slopes (figure 73).

Figure 72. Steam and fumarolic activity rose from Main crater at Manam on 18 October 2019 in this view to the south from a ridge north of the crater. Google Earth inset of summit shows location of photograph. Courtesy of Vulkanologische Gesellschaft and Claudio Jung, used with permission.

Figure 73. Volcanic debris covered an avalanche chute on the NE flank of Manam when visited by hikers on 18 October 2019. Courtesy of Vulkanologische Gesellschaft and Claudio Jung, used with permission.

On 2 November, a single large explosion at 1330 local time produced a thick, dark ash plume that rose about 1,000 m above the summit and drifted NW. A shockwave from the explosion was felt at the Bogia Government station located 40 km SE on the mainland about 1 minute later. RVO reported an increase in seismicity on 6 November about 90 minutes before the start of a new eruption from the Main Crater which occurred between 1600 and 1630; it produced light to dark gray ash clouds that rose about 1,000 m above the summit and drifted NW. Incandescent ejecta was visible at the start of the explosion and continued with intermittent strong pulses after dark, reaching peak intensity around 1900. Activity ended by 2200 that evening. The Darwin VAAC reported a discrete emission observed in satellite imagery on 8 November that rose to 4.6 km altitude and drifted WNW, although ground observers confirmed that no eruption took place; emissions were only steam and gas. There were no further reports of explosive activity until the Darwin VAAC reported an ash emission in visible satellite imagery on 20 March 2020 that rose to 3.1 km altitude and drifted E for a few hours before dissipating.

Although explosive activity was minimal during the period, SO₂ emissions, and evidence for continued thermal activity were recorded by satellite instruments each month. The TROPOMI instrument on the Sentinel-5P satellite captured evidence each month of SO₂ emissions exceeding two Dobson Units (figure 74). The most SO₂ activity occurred during October 2019, with 13 days of signatures over 2.0 DU. There were six days of elevated SO₂ each month in November and December, and five days in January 2020. During February and March, activity was less, with smaller SO₂ plumes recording more than 2.0 DU on three days each month. Sentinel-2 satellite imagery recorded thermal anomalies at least once from one or both of the summit craters each month between October 2019 and March 2020 (figure 75).

Figure 74. SO2 emissions at Manam exceeded 2 Dobson Units multiple days each month between October 2019 and March 2020. On 3 October 2019 (top left) emissions were also measured from Ulawun located 700 km E on New Britain island. On 30 November 2019 (top middle), in addition to a plume drifting N from Manam, a small SO2 plume was detected at Bagana on Bougainville Island, 1150 km E. The plume from Manam on 2 December 2019 drifted ESE (top right). On 26 January 2020 the plume drifted over 300 km E (bottom left). The plumes measured on 29 February and 4 March 2020 (bottom middle and right) only drifted a few tens of kilometers before dissipating. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 75. Sentinel-2 satellite imagery with Atmospheric penetration rendering (bands 12, 11, and 8a) showed thermal anomalies at one or both of Manam’s summit craters each month during October 2019-March 2020. On 17 October 2019 (top left) a bright anomaly and weak gas plume drifted NW from South crater, while a dense steam plume and weak anomaly were present at Main crater. On 25 January 2020 (top right) the gas and steam from the two craters were drifting E; the weaker Main crater thermal anomaly is just visible at the edge of the clouds. A clear image on 5 March 2020 (bottom left) shows weak plumes and distinct thermal anomalies from both craters; on 20 March (bottom right) the anomalies are still visible through dense cloud cover that may include steam from the crater vents as well. Courtesy of Sentinel Hub Playground.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; 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/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Vulkanologische Gesellschaft (URL: https://twitter.com/vulkanologen/status/1194228532219727874, https://twitter.com/vulkanologen/status/1193788836679225344); Claudio Jung, (URL: https://www.facebook.com/claudio.jung.1/posts/10220075272173895, https://www.instagram.com/jung.claudio/).

Near-constant fountains of lava at Stromboli have served as a natural beacon in the Tyrrhenian Sea for at least 2,000 years. Eruptive activity at the summit consistently occurs from multiple vents at both a north crater area (N area) and a southern crater group (CS area) on the Terrazza Craterica at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano-island (figure 168). Periodic lava flows emerge from the vents and flow down the scarp, sometimes reaching the sea; occasional large explosions produce ash plumes and pyroclastic flows. Thermal and visual cameras that monitor activity at the vents are located on the nearby Pizzo Sopra La Fossa, above the Terrazza Craterica, and at multiple locations on the flanks of the volcano. Detailed information for Stromboli is provided by Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) as well as other satellite sources of data; September-December 2019 is covered in this report.

Figure 168. This shaded relief map of Stromboli’s crater area was created from images acquired by drone on 9 July 2019 (In collaboration with GEOMAR drone group, Helmholtz Center for Ocean Research, Kiel, Germany). Inset shows Stromboli Island, the black rectangle indicates the area of the larger image, the black curved and the red hatched lines indicate, respectively, the morphological escarpment and the crater edges. Courtesy of INGV (Rep. No. 50/2019, Stromboli, Bollettino Settimanale, 02/12/2019 - 08/12/2019, data emissione 10/12/2019).

Activity was very consistent throughout the period of September-December 2019. Explosion rates ranged from 2-36 per hour and were of low to medium-high intensity, producing material that rose from less than 80 to over 150 m above the vents on occasion (table 7). The Strombolian activity in both crater areas often sent ejecta outside the crater rim onto the Terrazza Craterica, and also down the Sciara del Fuoco towards the coast. After the explosions of early July and late August, thermal activity decreased to more moderate levels that persisted throughout the period as seen in the MIROVA Log Radiative Power data (figure 169). Sentinel-2 satellite imagery supported descriptions of the constant glow at the summit, revealing incandescence at both summit areas, each showing repeating bursts of activity throughout the period (figure 170).

Table 7. Monthly summary of activity levels at Stromboli, September-December 2019. Low-intensity activity indicates ejecta rising less than 80 m, medium-intensity is ejecta rising less than 150 m, and high-intensity is ejecta rising over 200 m above the vent. Data courtesy of INGV.

Figure 169. Thermal activity at Stromboli was high during July-August 2019, when two major explosions occurred. Activity continued at more moderate levels through December 2019 as seen in the MIROVA graph of Log Radiative Power from 8 June through December 2019. Courtesy of MIROVA.

Figure 170. Stromboli reliably produced strong thermal signals from both of the summit vents throughout September-December 2019 and has done so since long before Sentinel-2 satellite imagery was able to detect it. Image dates are (top, l to r) 5 September, 15 October, 20 October, (bottom l to r) 14 November, 14 December 2019, and 3 January 2020. Sentinel-2 imagery uses Atmospheric penetration rendering with bands 12, 11, and 8A, courtesy of Sentinel Hub Playground.

After a major explosion with a pyroclastic flow on 28 August 2019, followed by lava flows that reached the ocean in the following days (BGVN 44:09), activity diminished in early September to levels more typically seen in recent times. This included Strombolian activity from vents in both the N and CS areas that sent ejecta typically 80-150 m high. Ejecta from the N area generally consisted of lapilli and bombs, while the material from the CS area was often finer grained with significant amounts of lapilli and ash. The number of explosive events remained high in September, frequently reaching 25-30 events per hour. The ejecta periodically landed outside the craters on the Terrazza Craterica and even traveled partway down the Sciara del Fuoco. An inspection on 7 September by INGV revealed four eruptive vents in the N crater area and five in the S crater area (figure 171). The most active vents in the N area were N1 with mostly ash emissions and N2 with Strombolian explosions rich in incandescent coarse material that sometimes rose well above 150 m in height. In the S area, S1 and S2 produced jets of lava that often reached 100 m high. A small cone was observed around N2, having grown after the 28 August explosion. Between 11 and 13 September aerial surveys with drones produced detailed visual and thermal imagery of the summit (figure 172).

Figure 171. Video of the Stromboli summit taken with a thermal camera on 7 September 2019 from the Pizzo sopra la Fossa revealed four active vents in the N area and five active vents in the S area. Images prepared by Piergiorgio Scarlato, courtesy of INGV (Rep. No. 37.2/2019, Stromboli, Bollettino Giornaliero del 10/09/2019).

Figure 172. An aerial drone survey on 11 September 2019 at Stromboli produced a detailed view of the N and CS vent areas (left) and thermal images taken by a drone survey on 13 September (right) showed elevated temperatures down the Sciara del Fuoco in addition to the vents in the N and CS areas. Images by E. De Beni and M. Cantarero, courtesy of INGV (Rep. No. 37.5/2019, Stromboli, Bollettino Giornaliero del 13/09/2019).

Strombolian activity from the N crater on 28 September and 1 October 2019 produced blocks and debris that rolled down the Sciara del Fuoco and reached the ocean (figure 173). Explosive activity from the CS crater area sometimes produced ejecta over 150 m high (figure 174). A survey on 26 November revealed that a layer of ash 5-10 cm thick had covered the bombs and blocks that were deposited on the Pizzo Sopra la Fossa during the explosions of 3 July and 28 August (figure 175). On the morning of 27 December a lava flow emerged from the CS area and traveled a few hundred meters down the Sciara del Fuoco. The frequency of explosive events remained relatively constant from September through December 2019 after decreasing from higher levels during July and August (figure 176).

Figure 173. Strombolian activity from vents in the N crater area of Stromboli produced ejecta that traveled all the way to the bottom of the Sciara del Fuoco and entered the ocean. Top images taken 28 September 2019 from the 290 m elevation viewpoint by Rosanna Corsaro. Bottom images captured on 1 October from the webcam at 400 m elevation. Courtesy of INGV (Rep. No. 39.0/2019 and Rep. No. 40.3, Stromboli, Bollettino Giornaliero del 29/09/2019 and 02/10/2019).

Figure 174. Ejecta from Strombolian activity at the CS crater area of Stromboli rose over 150 m on multiple occasions. The webcam located at the 400 m elevation site captured this view of activity on 8 November 2019. Courtesy of INGV (Rep. No. 45.5/2019, Stromboli, Bollettino Giornaliero del 08/11/2019).

Figure 175. The Pizzo Sopra la Fossa area at Stromboli was covered with large blocks and pyroclastic debris on 6 September 2019, a week after the major explosion of 28 August (top). By 26 November, 5-10 cm of finer ash covered the surface; the restored webcam can be seen at the far right edge of the Pizzo (bottom). Courtesy of INGV (Rep. No. 49/2019, Stromboli, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Figure 176. The average hourly frequency of explosive events at Stromboli captured by surveillance cameras from 1 June 2019 through 5 January 2020 remained generally constant after the high levels seen during July and August. The Total value (blue) is the sum of the average daily hourly frequency of all explosive events produced by active vents.

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 took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to 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/); 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).

Semeru is a stratovolcano located in East Java, Indonesia containing an active Jonggring-Seloko vent at the Mahameru summit. Common activity has consisted of ash plumes, pyroclastic flows and avalanches, and lava flows that travel down the SE flank. This report updates volcanism from September 2019 to February 2020 using primary information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

The dominant activity at Semeru for this reporting period consists of ash plumes, which were frequently reported by the Darwin VAAC. An eruption on 10 September 2019 produced an ash plume rising 4 km altitude drifting WNW, as seen in HIMAWARI-8 satellite imagery. Ash plumes continued to rise during 13-14 September. During the month of October the Darwin VAAC reported at least six ash plumes on 13, 14, 17-18, and 29-30 October rising to a maximum altitude of 4.6 km and moving primarily S and SW. Activity in November and December was relatively low, dominated mostly by strong and frequent thermal anomalies.

Volcanism increased in January 2020 starting with an eruption on 17 and 18 January that sent a gray ash plume up to 4.6 km altitude (figure 38). Eruptions continued from 20 to 26 January, producing ash plumes that rose up to 500 m above the crater that drifted in different directions. For the duration of the month and into February, ash plumes occurred intermittently. On 26 February, incandescent ejecta was ejected up to 50 m and traveled as far as 1000 m. Small sulfur dioxide emissions were detected in the Sentinel 5P/TROPOMI instrument during 25-27 February (figure 39). Lava flows during 27-29 February extended 200-1,000 m down the SE flank; gas-and-steam and SO₂ emissions accompanied the flows. There were 15 shallow volcanic earthquakes detected on 29 February in addition to ash emissions rising 4.3 km altitude drifting ESE.

Figure 38. Ash plumes rising from the summit of Semeru on 17 (left) and 18 (right) January 2020. Courtesy of MAGMA Indonesia and via Ø.L. Andersen's Twitter feed (left).

Figure 39. Small SO2 plumes from Semeru were detected by the Sentinel 5P/TROPOMI instrument during 25 (left) and 26 (right) February 2020. Courtesy of NASA Goddard Space Flight Center.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed relatively weak and intermittent thermal anomalies occurring during May to August 2019 (figure 40). The frequency and power of these thermal anomalies significantly increased during September to mid-December 2019 with a few hotspots occurring at distances greater than 5 km from the summit. These farther thermal anomalies to the N and NE of the volcano do not appear to be caused by volcanic activity. There was a brief break in activity during mid-December to mid-January 2020 before renewed activity was detected in early February 2020.

Figure 40. Thermal anomalies were relatively weak at Semeru during 30 April 2019-August 2019, but significantly increased in power and frequency during September to early December 2019. There was a break in activity from mid-December through mid-January 2020 with renewed thermal anomalies around February 2020. Courtesy of MIROVA.

The MODVOLC algorithm detected 25 thermal hotspots during this reporting period, which took place during 25 September, 18 and 21 October 2019, 29 January, and 11, 14, 16, and 23 February 2020. Sentinel-2 thermal satellite imagery shows intermittent hotspots dominantly in the summit crater throughout this reporting period (figure 41).

Figure 41. Sentinel-2 thermal satellite imagery detected intermittent thermal anomalies (bright yellow-orange) at the summit of Semeru, which included some lava flows in late January to early February 2020. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com).

Frequent historical eruptions have been reported from Mexico's Popocatépetl going back to the 14th century. Activity increased in the mid-1990s after about 50 years of quiescence, and the current eruption, ongoing since January 2005, has included numerous episodes of lava-dome growth and destruction within the 500-m-wide summit caldera. Multiple emissions of steam and gas occur daily, rising generally 1-3 km above the summit at about 5,400 m elevation; many contain small amounts of ash. Larger, more explosive events with ash plumes and incandescent ejecta landing on the flanks occur frequently. Activity through August 2019 was typical of the ongoing eruption with near-constant emissions of water vapor, gas, and minor ash, as well as multiple explosions with ash plumes and incandescent blocks scattered on the flanks (BGVN 44:09). This report covers similar activity from September 2019 through February 2020. Information comes from daily reports provided by México's Centro Nacional de Prevención de Desastres (CENAPRED); ash plumes are reported by the Washington Volcanic Ash Advisory Center (VAAC). Satellite visible and thermal imagery and SO₂ data also provide helpful observations of activity.

Activity summary. Activity at Popocatépetl during September 2019-February 2020 continued at the high levels that have been ongoing for many years, characterized by hundreds of daily low-intensity emissions that included steam, gas, and small amounts of ash, and periods with multiple daily minor and moderate explosions that produce kilometer-plus-high ash plumes (figure 140). The Washington VAAC issued multiple daily volcanic ash advisories with plume altitudes around 6 km for many, although some were reported as high as 8.2 km. Hundreds of minutes of daily tremor activity often produced ash emissions as well. Incandescent ejecta landed 500-1,000 m from the summit frequently. The MIROVA thermal anomaly data showed near-constant moderate to high levels of thermal energy throughout the period (figure 141).

Figure 140. Emissions continued at a high rate from Popocatépetl throughout September 2019-February 2020. Daily low-intensity emissions numbered usually in the hundreds (blue, left axis), while less frequent minor (orange) and moderate (green) explosions, plotted on the right axis, occurred intermittently through November 2019, and increased again during February 2020. Data was compiled from CENAPRED daily reports.

Figure 141. MIROVA log radiative power thermal data for Popocatépetl from 1 May 2019 through February 2020 showed a constant output of moderate energy the entire time. Courtesy of MIROVA.

Sulfur dioxide emissions were measured with satellite instruments many days of each month from September 2019 thru February 2020. The intensity and drift directions varied significantly; some plumes remained detectable hundreds of kilometers from the volcano (figure 142). Plumes were detected almost daily in September, and on most days in October. They were measured at lower levels but often during November, and after pulses in early and late December only small plumes were visible during January 2020. Intermittent larger pulses returned in February. Dome growth and destruction in the summit crater continued throughout the period. A small dome was observed inside the summit crater in late September. Dome 85, 210-m-wide, was observed inside the summit crater in early November. Satellite imagery captured evidence of dome growth and ash emissions throughout the period (figure 143).

Figure 142. Sulfur dioxide emissions from Popocatépetl were frequent from September 2019 through February 2020. Plumes drifted SW on 7 September (top left), 30 October (top middle), and 21 February (bottom right). SO2 drifted N and NW on 26 November (top right). On 2 December (bottom left) a long plume of sulfur dioxide hundreds of kilometers long drifted SW over the Pacific Ocean while the drift direction changed to NW closer to the volcano. The SO2 plumes measured in January (bottom center) were generally smaller than during the other months covered in this report. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 143. Sentinel-2 satellite imagery of Popocatépetl during November 2019-February 2020 provided evidence for ongoing dome growth and explosions with ash emissions. Top left: a ring of incandescence inside the summit crater on 8 November 2019 was indicative of the growth of dome 85 observed by CENAPRED. Top middle: incandescence on 8 December inside the summit crater was typical of that observed many times during the period. Top right: a dense, narrow ash plume drifted N from the summit on 17 January 2020. Bottom left: Snow cover made ashfall on 6 February easily visible on the E flank. On 11 February, the summit crater was incandescent and nearly all the snow was covered with ash. Bottom right: a strong thermal anomaly and ash emission were captured on 21 February. Bottom left and top right images use Natural color rendering (bands 4, 3, 2); other images use Atmospheric penetration rendering to show infrared signal (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Activity during September-November 2019. On 1 September 2019 minor ashfall was reported in the communities of Atlautla, Ozumba, Juchitepec, and Tenango del Aire in the State of Mexico. The ash plumes rose less than 2 km above the summit and incandescent ejecta traveled less than 100 m from the summit crater. Twenty-two minor and three moderate explosions were recorded on 4-5 September along with minor ashfall in Juchitepec, Tenango del Aire, Tepetlixpa, and Atlautla. During a flyover on 5 September, officials did not observe a dome within the crater, and the dimensions remained the same as during the previous visit (350 m in diameter and 150 m deep) (figure 144). Ashfall was reported in Tlalmanalco and Amecameca on 6 September. The following day incandescent ejecta was visible on the flanks near the summit and ashfall was reported in Amecameca, Ayapango, and Tenango del Aire. The five moderate explosions on 8 September produced ash plumes that rose as high as 2 km above the summit, and incandescent ejecta on the flanks. Explosions on 10 September sent ejecta 500 m from the crater. Eight explosions during 20-21 September produced ejecta that traveled up to 1.5 km down the flanks (figure 145). During an overflight on 27 September specialists from the National Center for Disaster Prevention (CENAPRED ) of the National Coordination of Civil Protection and researchers from the Institute of Geophysics of UNAM observed a new dome 30 m in diameter; the overall crater had not changed size since the overflight in early September.

Figure 144. CENAPRED carried out overflights of Popocatépetl on 5 (left) and 27 September (right) 2019; the crater did not change in size, but a new dome 30 m in diameter was visible on 27 September. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl, 05 y 27 de septiembre).

Figure 145. Ash plumes at Popocatépetl on 19 (left) and 20 (right) September 2019 rose over a kilometer above the summit before dissipating. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 19 y 20 de septiembre).

Fourteen explosions were reported on 2 October 2019. The last one produced an ash plume that rose 2 km above the summit and sent incandescent ejecta down the E slope (figure 146). Ashfall was reported in the municipalities of Atlautla Ozumba, Ayapango and Ecatzingo in the State of Mexico. Explosions on 3 and 4 October also produced ash plumes that rose between 1 and 2 km above the summit and sent ejecta onto the flanks. Additional incandescent ejecta was reported on 6, 7, 15, and 19 October. The communities of Amecameca, Tenango del Aire, Tlalmanalco, Cocotitlán, Temamatla, and Tláhuac reported ashfall on 10 October; Amecameca reported more ashfall on 12 October. On 22 October slight ashfall appeared in Amecameca, Tenango del Aire, Tlalmanalco, Ayapango, Temamatla, and Atlautla.

Figure 146. Incandescent ejecta at Popocatépetl traveled down the E slope on 2 October 2019 (left); an ash plume two days later rose 2 km above the summit (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 2 y 4 de octubre).

During 2-3 November 2019 there was 780 minutes of tremor reported in four different episodes. The seismicity was accompanied by ash emissions that drifted W and NW and produced ashfall in numerous communities, including Amecameca, Juchitepec, Ozumba, Tepetlixpa, and Atlautla in the State of México, in Ayapango and Cuautla in the State of Morelos, and in the municipalities of Tlahuac, Tlalpan, and Xochimilco in Mexico City. A moderate explosion on 4 November sent incandescent ejecta 2 km down the slopes and produced an ash plume that rose 1.5 km and drifted NW. Minor ashfall was reported in Tlalmanalco, Amecameca, and Tenango del Aire, State of Mexico. Similar ash plumes from explosions occurred the following day. Scientists from CENAPRED and the Institute of Geophysics of UNAM observed dome number 85 during an overflight on 5 November 2019. It had a diameter of 210 m and was 80 m thick, with an irregular surface (figure 147). Multiple explosions on 6 and 7 November produced incandescent ejecta; a moderate explosion late on 11 November produced ejecta that traveled 1.5 km from the summit and produced an ash plume 2 km high (figure 148). A lengthy period of constant ash emission that drifted E was reported on 18 November. A moderate explosion on 28 November sent incandescent fragments 1.5 km down the slopes and ash one km above the summit.

Figure 147. A new dome was visible inside the summit crater at Popocatépetl during an overflight on 5 November 2019. It had a diameter of 210 m and was 80 m thick. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl, 05 de noviembre).

Figure 148. Ash emissions and explosions with incandescent ejecta continued at Popocatépetl during November 2019. The ash plume on 1 November changed drift direction sharply a few hundred meters above the summit (left). Incandescent ejecta traveled 1.5 km down the flanks on 11 November (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 1 y 12 de noviembre).

Activity during December 2019-February 2020. Throughout December 2019 weak emissions of steam and gas were reported daily, sometimes with minor amounts of ash, and minor explosions were only reported on 21 and 27 December. On 21 December two new high-resolution webcams were installed around Popocatépetl, one 5 km from the crater at the Tlamacas station, and the second in San Juan Tianguismanalco, 20 km away. Ash emissions and incandescent ejecta 800 m from the summit were observed on 25 December (figure 149). Incandescence at night was reported during 27-29 December.

Figure 149. Incandescent ejecta moved 800 m down the flanks of Popocatépetl during explosions on 25 December 2019 (left); weak emissions of steam, gas, and minor ash were visible on 27 December and throughout the month. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 25 y 27 de diciembre).

Continuous emissions of water vapor and gas with low ash content were typical daily during January 2020. A moderate explosion on 9 January produced an ash plume that rose 3 km from the summit and drifted NE. In addition, incandescent ejecta traveled 1 km from the crater rim. A minor explosion on 21 January produced a 1.5-km-high plume with low ash content and incandescent ejecta that fell near the crater (figure 150). The first of two explosions late on 27 January produced ejecta that traveled 500 m and a 1-km-high ash plume. Constant incandescence was observed overnight on 29-30 January.

Figure 150. Although fewer explosions were recorded at Popocatépetl during January 2020, activity continued. An ash plume on 19 January rose over a kilometer above the summit (top left). A minor explosion on 21 January produced a 1.5-km-high plume with low ash content and incandescent ejecta that fell near the crater (top right). Smaller emissions with steam, gas, and ash were typical many days, including on 22 (bottom left) and 31 (bottom right) January 2019. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 19, 21, 22 y 31 de enero).

A moderate explosion on 5 February 2020 produced an ash plume that rose 1.5 km and drifted NNE. Explosions on 10 and 13 February sent ejecta 500 m down the flanks (figure 151). During an overflight on 18 February scientists noted that the internal crater maintained a diameter of 350 m and its approximate depth was 100-150 m; the crater was covered by tephra. For most of the second half of February the volcano had a continuous emission of gases with minor amounts of ash. In addition, multiple explosions produced ash plumes that rose 400-1,200 m above the crater and drifted in several different directions.

Figure 151. Ash emissions and explosions continued at Popocatépetl during February 2020. Dense ash drifted near the snow-covered summit on 6 February (top left). Incandescent ejecta traveled 500 m down the flanks on 13 February (top right). Ash plumes billowed from the summit on 18 and 22 February (bottom row). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl, 6, 15, 18 y 22 de febrero).

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.unam.mx/), Daily Report Archive http://www.cenapred.unam.mx:8080/reportesVolcanGobMX/BuscarReportesVolcan); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing and actively erupting since 1922. Ash explosions, pyroclastic, and lava flows have emerged from Caliente, the youngest of the four vents in the complex, for more than 40 years. A lava dome that appeared within the summit crater of Caliente in October 2016 has continued to grow, producing frequent block avalanches down the flanks. Daily explosions with ash plumes and block avalanches continued during September 2019-February 2020, the period covered in this report, with information primarily from Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center).

Constant fumarolic activity with steam and gas persisted from the Caliente dome throughout September 2019-February 2020. Explosions occurred multiple times per day, producing ash plumes that rose to altitudes of 3.1-3.5 km and usually drifted a few kilometers before dissipating. Several lahars during September and October carried volcanic blocks, ash, and debris down major drainages. Periodic ashfall was reported in communities within 10 km of the volcano. An increase in thermal activity beginning in November (figure 101) resulted in an increased number of observations of incandescence visible at night from the summit of Caliente through February 2020. Block avalanches occurred daily on the flanks of the dome, often reaching the base, stirring up small clouds of ash that drifted downwind.

Figure 101. The MIROVA project graph of thermal activity at Santa María from 12 May 2019 through February 2020 shows a gradual increase in thermal energy beginning in November 2019. This corresponds to an increase in the number of daily observations of incandescence at the summit of the Caliente dome during this period. Courtesy of MIROVA.

Constant steam and gas fumarolic activity rose from the Caliente dome, drifting W, usually rising to 2.8-3.0 km altitude during September 2019. Multiple daily explosions with ash plumes rising to 2.9-3.4 km altitude drifted W or SW over the communities of San Marcos, Loma Linda Palajunoj, and Monte Claro (figure 102). Constant block avalanches fell to the base of the cone on the NE and SE flanks. The Washington VAAC reported an ash plume visible in satellite imagery on 10 September at 3.1 km altitude drifting W. On 14 September another plume was spotted moving WSW at 4.6 km altitude which dissipated quickly; the webcam captured another plume on 16 September. Ashfall on 27 September reached about 1 km from the volcano; it reached 1.5 km on 29 September. Lahars descended the Rio Cabello de Ángel on 2 and 24 September (figure 102). They were about 15 m wide, and 1-3 m deep, carrying blocks 1-2 m in diameter.

Figure 102. A lahar descended the Rio Cabello de Ángel at Santa Maria and flowed into the Rio Nima 1 on 24 September 2019. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 21 al 27 de septiembre de 2019).

Througout October 2019, degassing of steam with minor gases occurred from the Caliente summit, rising to 2.9-3.0 km altitude and generally drifting SW. Weak explosions took place 1-5 times per hour, producing ash plumes that rose to 3.2-3.5 km altitude. Ashfall was reported in Monte Claro on 2 October. Nearly constant block avalanches descended the SE and S flanks, disturbing recent layers of fine ash and producing local ash clouds. Moderate explosions on 11 October produced ash plumes that rose to 3.5 km altitude and drifted W and SW about 1.5 km towards Río San Isidro (figure 103). The following day additional plumes drifted a similar distance to the SE. The Washington VAAC reported an ash emission visible in satellite imagery at 4.9 km altitude on 13 October drifting NNW. Ashfall was reported in Parcelamiento Monte Claro on 14 October. Some of the block avalanches observed on 14 October on the SE, S, and SW flanks were incandescent. Ash drifted 1.5 km W and SW on 17 October. Ashfall was reported near la finca Monte Claro on 25 and 28 October. A lahar descended the Río San Isidro, a tributary of the Río El Tambor on 7 October carrying blocks 1-2 m in diameter, tree trunks, and branches. It was about 16 m wide and 1-2 m deep. Additional lahars descended the rio Cabello de Angel on 23 and 24 October. They were about 15 m wide and 2 m deep, and carried ash and blocks 1-2 m in diameter, tree trunks, and branches.

Figure 103. Daily ash plumes were reported from the Caliente cone at Santa María during October 2019, similar to these from 30 September (left) and 11 October 2019 (right). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 28 de septiembre al 04 de octubre de 2019; Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 05 al 11 de octubre de 2019).

During November 2019, steam plumes rose to 2.9-3.0 km altitude and generally drifted E. There were 1-3 explosions per hour; the ash plumes produced rose to altitudes of 3.1-3.5 km and often drifted SW, resulting in ashfall around the volcanic complex. Block avalanches descended the S and SW flanks every day. On 4 November ashfall was reported in the fincas (ranches) of El Faro, Santa Marta, El Viejo Palmar, and Las Marías, and the odor of sulfur was reported 10 km S. Incandescence was observed at the Caliente dome during the night of 5-6 November. Ash fell again in El Viejo Palmar, fincas La Florida, El Faro, and Santa Marta (5-6 km SW) on 7 November. Sulfur odor was also reported 8-10 km S on 16, 19, and 22 November. Fine-grained ash fell on 18 November in Loma Linda and San Marcos Palajunoj. On 29 November strong block avalanches descended in the SW flank, stirring up reddish ash that had fallen on the flanks (figure 104). The ash drifted up to 20 km SW.

Figure 104. Ash plumes rose from explosions multiple times per day at Santa Maria’s Santiaguito complex during November 2019, and block avalanches stirred up reddish clouds of ash that drifted for many kilometers. Courtesy of INSIVUMEH. Left, 11 November 2019, from Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 09 al 15 de noviembre de 2019. Right, 29 November 2019 from BOLETÍN VULCANOLÓGICO ESPECIAL BESTG# 106-2019, Guatemala 29 de noviembre de 2019, 10:50 horas (Hora Local).

White steam plumes rising to 2.9-3.0 km altitude drifted SE most days during December 2019. One to three explosions per hour produced ash plumes that rose to 3.1-3.5 km altitude and drifted W and SW producing ashfall on the flanks. Several strong block avalanches sent material down the SW flank. Ash from the explosions drifted about 1.5 km SW on 3 and 7 December. The Washington VAAC reported a small ash emission that rose to 4.9 km altitude and drifted WSW on 8 December, and another on 13 December that rose to 4.3 km altitude. Ashfall was reported up to 10 km S on 24 December. Incandescence was reported at the dome by INSIVUMEH eight times during the month, significantly more than during the recent previous months (figure 105).

Figure 105. Strong thermal anomalies were visible in Sentinel-2 imagery at the summit of the Caliente cone at Santa María’s Santiaguito’s complex on 19 December 2019. Image uses Atmospheric Penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Activity during January 2020 was similar to that during previous months. White plumes of steam rose from the Caliente dome to altitudes of 2.7-3.0 km and drifted SE; one to three explosions per hour produced ash plumes that rose to 3.2-3.4 km altitude and generally drifted about 1.5 km SW before dissipating. Frequent block avalanches on the SE flank caused smaller plumes that drifted SSW often over the ranches of San Marcos and Loma Linda Palajunoj. On 28 January ash plumes drifted W and SW over the communities of Calaguache, El Nuevo Palmar, and Las Marías. In addition to incandescence observed at the crater of Caliente dome at least nine times, thermal anomalies in satellite imagery were detected multiple times from the block avalanches on the S flank (figure 106).

Figure 106. Incandescence at the summit and in the block avalanches on the S flank of the Caliente cone at Santa María’s Santiaguito’s complex was visible in Sentinel-2 satellite imagery on 8 and 13 January 2020. Atmospheric penetration rendering images (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

The Washington VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude drifting W on 3 February 2020. INSIVUMEH reported constant steam degassing that rose to 2.9-3.0 km altitude and drifted SW. In addition, 1-3 weak to moderate explosions per hour produced ash plumes to 3.1-3.5 km altitude that drifted about 1 km SW. Small amounts of ashfall around the volcano’s perimeter was common. The ash plumes on 5 February drifted NE over Santa María de Jesús. On 8 February the ash plumes drifted E and SE over the communities of Calaguache, El Nuevo Palmar, and Las Marías. Block avalanches on the S and SE flanks of Caliente dome continued, creating small ash clouds on the flank. Incandescence continued frequently at the crater and was also observed on the S flank in satellite imagery (figure 107).

Figure 107. Incandescence at the summit and on the S flank of the Caliente cone at Santa María’s Santiaguito’s complex was frequent during February 2020, including on 2 (left) and 17 (right) February 2020 as seen in Sentinel-2 imagery. Atmostpheric Penetration rendering imagery (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile 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 vents, with activity progressing W towards the most recent, 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/ ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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/).

Bagana is one of Melanesia's youngest and most active volcanoes; it is located on Bougainville Island, Papua New Guinea (figure 22). We begin this Bulletin report with a short summary of activity at Bagana from January 2013 through July 2014 (partly described in BGVN 39:06). We then focus on activity from August 2014-April 2015. The information included in this report primarily was found in material published by the Darwin Volcanic Ash Advisory Center (VAAC). Rabaul Volcano Observatory (RVO) reporting also appears in this report, particularly describing activity from August 2014. RVO reports are either sent directly to the Global Volcanism Program (GVP) or are included in Darwin VAAC Weekly Activity reports.

In this report we use local time for cases and observations reported by observers on the ground (two cases, on 10 and 12 August 2014). Otherwise, as is often the convention for satellite data, we use UTC. [Local time = UTC+11h.] The last Bulletin report (BGVN 39:06) discussed Bagana activity during 2011-2014.

Figure 22 below and figure 9 in BGVN 33:11 highlight the location of Bagana.

Figure 22. Image highlights the location of Bagana on Bougainville Island, Papua New Guinea. Bagana is located in a remote central portion of Bougainville Island. Papua New Guinea is located in SW Pacific, to the N and NE of Australia. Courtesy of the Darwin Volcanic Ash Advisory Center (VAAC).

Activity during January 2013-July 2014. During this interval, Bagana's activity was mainly characterized by the emission of ash plumes. Based on information in Volcanic Ash Advisories (VAAs) published by the Darwin VAAC, in 2013 ash plumes from Bagana ranged from 1.8-4 km in altitude above sea level (a.s.l.) and drifted between 35 and 130 km. These plumes drifted towards the SW-N-E.

Through July 2014, ash plumes from Bagana ranged from 2.1-3 km in altitude a.s.l. and drifted 25-110 km according to the Darwin VAAC's VAAs. Ash plumes again drifted to the SW-N-E, and also to the SSE.

August-December 2014. This section documents activity at Bagana from August to December 2014. Information on Bagana's activity was scarce during October and December. From August through December, Bagana's Aviation Color Code (ACC) was mainly Orange; however, as noted below, on 12 August 2014, Bagana's ACC was upgraded to Red, the highest of the four colors in the Code. During this interval, ash plumes ranged from 2.1-7.6 km in altitude a.s.l. and drifted as much as 167 km. The plumes drifted to the SW-NE.

At the beginning of August 2014, variable amounts of thin to thick white vapor were seen being emitted from Bagana. During the second week of August, activity at Bagana increased. On 6 and 8 August, noises associated with rock falls were reported. According to the RVO, these rockfalls "may have been triggered by breakaway of large blocky lava from the front lobe of ongoing effusive lava flows which are [well known] for Bagana activity."

According to a 10 August 2014 RVO report, around 0500 local time on 10 August 2014, an eruption began at Bagana that emitted an ash plume with a height estimated at several hundred meters above the crater. Personnel at the government station at Piva in Torokina (figure 21 in BGVN 39:06), reported that Bagana continued to emit variable thick dark ash clouds throughout the day. Ash clouds were blown to the SW and W, and possibly to the NW. In Wakovi, 6 km W of Bagana, ashfall was reported to have destroyed small tree branches, banana trees, and potato gardens. Ashfall was also reported in Laruma and at the Piva government station (figure 21 in BGVN 39:06). RVO further stated, "Conditions at Gotana, located about 9 km southwest from the volcano, are slightly better and people from Wakovi have been urged to move there if ashfall continues and conditions deteriorates."

Whether any Wakovi residents did evacuate is uncertain.

From 2332 UTC on 10 August to 2132 UTC on 11 August, a volcanic ash plume was seen in satellite imagery (figure 23). The plume rose to an altitude of 3.1 km a.s.l. and eventually extended 167 km SW. On 12 August 2014, the Darwin VAAC observed ash clouds rising to an altitude of 7.6 km a.s.l., resulting in Bagana's ACC to be increased to Red. The plumes eventually extended 167 km SW. In their VAAs from 12 August UTC, the Darwin VAAC remarked that an ongoing eruption (described as low-level in VAAs from 0700-~1000 UTC) was observed on satellite. In some of those VAAs, they also stated, "Ash from [the] initial explosive eruption [was] partially obscured by thunderstorm activity and [was] becoming detached from [the] volcano."

According to a 13 August 2014 RVO report, at 1810 local time on 12 August, an earthquake was felt with an intensity of II on the Modified Mercalli Scale. The report stated that the earthquake was tectonic in origin. That RVO report also stated that areas in the W and SW were affected by ashfall. They described the level of exposure from ash as moderate in Wakovi and low around Kawai, Gotana and Piva government station (figure 21 in BGVN 39:06).

Figure 23. A MTSAT-2 Visible satellite image captured on 10 August at 23:32 UTC. Volcanic ash plume emitted from Bagana is enclosed in the white rectangle. This plume was observed to an altitude of 3.1 km a.s.l and eventually drifted 167 km SW. On the image, Bagana is represented by the yellow circle. Taken from 6-14 August 2014 Weekly Activity report compiled by the Darwin VAAC.

According to the 13-19 August 2014 Darwin VAAC Weekly Activity report, Bagana's ACC was downgraded to Orange; the specific date when the downgrade occurred was not stated. Bagana's ACC remained Orange through the end of the year. RVO reported that since 10 August, there were ash emissions, but Bagana's level of activity had decreased.

From 25-28 August 2014, ash plumes, identified on satellite images, ranged from altitudes of 2.1-2.4 km a.s.l. and extended from 35-120 km, mainly to the W and WNW and some to the SW. From 19-31 August, RVO reported that Bagana's activity was characterized by weak to moderate white vapor. They reported light gray ash plumes blowing SW on 19 and 27 August and a dull glow emanating from the summit on 19, 27, 29, and 31 August. Low roaring noises were also briefly heard on 27 August according to the RVO.

During September 2014, the Darwin VAAC reported a narrow ash plume on satellite imagery at 2132 UTC on 13 September. The plume was observed at an altitude of 2.4 km a.s.l and extended 139 km to the W. Then at 2332 UTC on 20 September, another ash plume was observed at 2.4 km a.s.l. This plume extended 56 km W. In the available Darwin VAAC Weekly Activity reports, only Bagana's ACC was reported during the month of October.

In November 2014, an ash plume that extended 65 km S was observed at 2132 UTC on 8 November. In a VAA released at 0232 UTC on 9 November, the Darwin VAAC reported that ash from Bagana had dissipated in the satellite imagery. At the end of December 2014, Darwin VAAC reported an ash plume from Bagana on 29 December. The plume rose to an altitude of 2.4 km a.s.l. and extended ~95 km NE.

January through 14 April 2015. This section discusses Bagana activity from January to mid-April 2015. During this interval, Bagana's ACC was reported as Orange by the Darwin VAAC. During much of February and March 2015, Bagana's ACC was the only information reported in the available Darwin VAAC Weekly Activity reports. In this interval, ash plumes rose up to3.7 km in altitude a.s.l. and drifted to the N-NE-SE and to the SW.

At 2232 UTC on 20 January 2015, an ash plume was identified on satellite images. Darwin VAAC considered the plume to be low-level and it extended 37 km NE at an altitude of 3.7 km a.s.l. At 0032 UTC on 21 January, Darwin VAAC identified the ash plume again on satellite imagery. In that satellite image, the plume extended 22 km NE at an altitude of 3.7 km a.s.l. After that, the Darwin VAAC reported a meteorological cloud that covered the area. Later at 2232 UTC on 21 January, the plume was seen drifting 18 km SW at an altitude of 2.7 km a.s.l (figure 24).

Figure 24. An MTSAT-2 satellite image captured at 2232 UTC 21 January 2015. The volcanic ash plume in within the rectangle drifted 18 km SW at an altitude of 2.7 km a.s.l. Bagana is represented by the yellow circle. Taken from the 21-27 January 2015 issue of the Weekly Activity report compiled by the Darwin VAAC.

On 25 March 2015, an ash plume was identified on satellite imagery at 2132 UTC. The plume was observed at 2.1 km and drifted 37 km N-NE. At 2132 UTC on 26 March, another volcanic plume was observed at 3.1 km and extended 56 km NE. The Darwin VAAC reported observing a consistent plume until 0108 UTC on 30 March, when ash had dissipated. When the consistent plume was first observed was not stated in the 25-31 March 2015 Darwin VAAC Weekly Activity report. Darwin VAAC also reported a plume on satellite images at 2132 UTC on 31 March. The plume drifted 74 km SE at an altitude of 2.1 km a.s.l. The plume then shifted to the NE before a VAA at 0438 UTC on 2 April reported that the ash had dissipated. In the 8-14 April 2015 Weekly Activity report, the ACC remained at Orange.

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); and Rabaul Volcano Observatory, Department of Mineral Policy and Geohazards Management, Volcanological Observatory Geohazards Management Division, P.O. Box 386, Kokopo, East New Britain Province, Papua New Guinea.

This Bulletin report discusses activity at Chirinkotan from May 2014 to late-April 2015. The information presented here was primarily sourced from the Sakhalin Volcanic Eruptions Response Team (SVERT). SVERT is in charge of monitoring volcanic activity within the Kuril Islands from Onekotan in the N to Kunashir in the S (figure 2). The volcano also forms an island of the same name. Figure 1 in BGVN 38:12 provides a view of Chirinkotan's location within the Kuril Islands.

Our last Bulletin report (BGVN 38:12) recorded Chirinkotan activity that occurred from May 2013 to April 2014. During that interval, gas-and-steam emissions and thermal alerts were frequently observed and reported (table 1 in BGVN 38:12).

Figure 2. Maps highlighting the location of Chirinkotan, within the Kuril Islands. On the larger map, Chirinkotan is represented by a red dot directly above the label "Chirinkotan." The map also shows the other islands of the Kuril archipelago, which are located between the Kamchatka Peninsula (Russia, top center) and Hokkaido (Japan, lower left). Also marked on this map are appoximate seafloor convergence rates (arrows) and the location of the trench's E margin (heavy dashed line). The index map, in the top left corner, shows the general area in which the Kuril Islands are located. 'KC' represents the Kamchatka Current and 'SWC' represents the Soya warm current. Image taken from Belousov and others (2009).

May 2014 to late-April 2015. Due to similarities between Chirinkotan's activity from May 2014 through late-April 2015 and May 2013-April 2014 (BGVN 38:12), we once again use a table to summarize Chirinkotan's activity.

Due to their inaccessibility, SVERT relies on satellite monitoring to monitor volcanic activity within the Kuril Islands. On the basis of those observations, SVERT often reported thermal anomalies and gas-and-steam emissions at Chirinkotan during this reporting interval (May 2014 to late April 2015). SVERT frequently reported that clouds obscured views of Chirinkotan, which halted collection of satellite data.

SVERT also reports Chirinkotan's Aviation Color Code (ACC). The ACC is a four color scale used by some volcano observatories and the aviation community to communicate volcanic-ash hazards of a volcano. The colors in order of increasing volcanic activity are Green, Yellow, Orange and Red.

In an overview, the ACC stood at Yellow during the following periods: May 2014 to the beginning of June 2014; late November 2014 to late February 2015; and from mid-March to late April 2015. SVERT reported Chirinkotan's ACC as Green during June to late November 2014 and early March 2015.

Table 2 summarizes available SVERT data on Chirinkotan's activity. The table is divided into two columns labeled Date and Comments. The Date column refers to the week during which Chirinkotan activity was observed or reported by SVERT. The Comments column details Chirinkotan's ACC and what activity occurred at Chirinkotan on a particular day or during a particular week.

Table 2. Table condensing Chirinkotan's activity and cases where cloud cover hindered observations between May 2014 and late April 2015. The information in the table was observed in satellite data by SVERT personnel. Bulletin editors gathered this information from available SVERT material (generally published on the end date of the date ranges in the left column).

References. Belousov, A., Belousova, M., and Miller, T., 2009, Kurile Islands, pp 520-525 in: Encyclopedia of Islands, Gillespie, R. and Clague D., eds., University of California Press, 1111 pp., accessed on 29 April 2015, (URL: http://www.kscnet.ru/ivs/lavdi/staff/belousov/kuriles-2009.pdf).

Geologic Background. The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W volcanic chain that extends nearly 50 km W of the central part of the main Kuril Islands arc. It is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SW. Lava flows from a cone within the breached crater reached the shore of the island. Historical eruptions have been recorded since the 18th century. Lava flows were observed by the English fur trader Captain Snow in the 1880s.

Information Contacts: Sakhalin Volcanic Eruptions Response Team (SVERT), Institute of Marine Geology and Geophysics (IMG&G) Far East Division Russian Academy of Sciences (FED RAS), 1B Science St., Yuzhno-Sakhalinsk, 693022, Russia (URL: http://www.imgg.ru/).

This report, taken largely from Hawaiian Volcano Observatory (HVO) reports and online photo galleries, nominally covers 27 June to 30 December 2014 but adds a few details from earlier and later intervals. The lava flow just before this interval, called the Kahauale'a 2 flow, had started in May 2013 (BGVN 39:05). That flow had, during April-June 2014, advanced erratically (BGVN 39:09) and HVO Daily Updates declared it inactive ("cutoff and dead") by 30 June.

Prior to that, on 27 June, a new flow had emerged adjacent to the Kahauale'a 2 flow; it became informally named the June 27th breakout and then the June 27th lava flow. The June 27th lava flow made it to the outskirts of Pahoa, stopping at the end of 2014 with two lobes as close as about 0.7-0.8 km W of the major arterial road that passes through the town (HI-130).

The 27 June to 30 December 2014 interval was characterized by unusual developments shown here chiefly by a series of maps. The June 27th lava flow did not follow the usual pattern of flow from the summit or E rift zone to the sea. Rather, this June 27th lava flow, like the Kahauale?a 2 flow, generally progressed E to NE.

The HVO reporting during this reporting interval included a number of commonly seen processes in the over 3-decade-long eruption, which we largely omit here for brevity. We presented a summary of many of those processes in the introduction to our previous report (BGVN 39:09). They include, for example, glow, spatter, minor ash, pelee's hair, and similar emissions at either the summit vent's lava lake or along the E rift zone at Pu'u O'o crater. We have done little to track the details of breakouts on a daily or hourly basis, particularly in the near-vent area. It is also worth noting that monitoring was disrupted by Hurricane Iselle on and around 7 August 2014.

Subsections below are as follows: "Events at Pu'u O'o and Halema'ama'u"; "June 27th lava flow advance towards Pahoa"; "Graphical approaches to hazards and scientific communication"; "Lava lake heights in Overlook crater"; "Geophysical monitoring"; and "SO₂ flux data." For readers seeking a deeper understanding a recent book delves into the characteristics of Hawaiian volcanoes (Poland and others, 2014).

Events at Pu'u O'o and Halema'ama'u. On 27 June the new breakout on the NE flank of Pu'u O'o erupted through fissures. HVO's online reporting in their Photo and Video section stated that the breakout reached 1.5 km long by 1100 local time. Several fissures on the upper NE flank of Pu'u O'o cone sent out flows to the NE, HVO noted. These flows partially overlapped with the existing Kahauale?a 2 flow, which had scattered surface flows that morning. Breakouts caused minor subsidence in the Pu'u O'o crater floor. This led to collapses of several spatter cones on the crater floor. Small lava ponds were revealed and the NE lava pond enlarged due to the collapse. HVO reporting at the time (27 June) described the Kahauale?a 2 flow as still active.

By 30 June HVO declared the Kahauale?a 2 flow inactive. The lava tube feeding the Kahauale?a 2 lost hydraulic connection to the NE lava pond when the level of that lake dropped. The entry to the tube could be seen stranded meters above the lava in the vent wall (figure 231).

Figure 231. View of the wall (roughly 10 m high) above the lava pond in the NE portion of Pu'u O'o crater. The lava pond surface is in the lower portion of the photograph. The dark hole in the upper part of the photograph is the entrance to the ~2-m diameter lava tube that had been supplying lava to the Kahauale?a 2 flow. When the lava level dipped well below the entrance to the lava tube, lava ceased entering the tube, leaving the Kahauale?a 2 flow inactive. Look direction unstated. Courtesy of HVO.

More details follow on the June 27th flow's early phases, as reported in the 27 June 2014 Daily Update. "Seismic tremor levels were low with a few dropouts (periods when spattering is absent in the lava lake and gas emissions are relatively low). Sixteen earthquakes were strong enough to be located beneath Kilauea Volcano in the past 24 hours: 1 [centered on a fault system passing NNW of Kilauea's summit] in the Ka'oiki Pali area, 1 beneath Halema`uma`u Crater, 4 beneath the area south of Halema`uma`u Crater, 6 on south flank faults, 3 within the upper East Rift Zone, and one within the middle East Rift Zone. GPS receivers spanning the summit caldera recorded almost +4 cm of extension since May 24; the long-term, cross-caldera measurements indicate continued extension at a rate averaging 10 cm/yr (4 in/yr) since March, 2010.

"Recent Observations at the middle East Rift Zone vents: The tiltmeter at Pu'u O'o cone recorded an abrupt drop, that is slowing, of more than 7 microradians. The lava flow from the northeast spatter cone continued to be active until midnight; early this morning, coincident with the rapid deflation, the crater floor started to slowly subside and new lava was erupted on the north flank of Pu'u O'o cone; in addition, the upper part of the south cone collapsed around 7 am. GPS receivers recorded 5 cm of contraction across the cone following this morning's deflation."

"Recent Observations of the Kahauale'a 2 flow: PNcam views yesterday showed active breakouts at the north base of Pu'u O'o cone and distant broad smoke plumes, with multiple glowing points visible at night from both near and distant breakouts. A satellite image from June 20 showed multiple active breakouts in the interior of the Kahauale'a 2 flow extending 7.1 km (4.4 mi) northeast from the Pu'u O'o vent (see map for June 17 flow details).

"In general, this slow-moving [Kahauale'a 2 ] lava flow has made erratic progress over the past few months and appears to be slowly weakening. Disruption of the flow front has occurred during strong DI deflation events when the lava supply abruptly decreased causing the flow front to stagnate. DI inflation and resumption of lava supply usually follow a few days later. Breakouts reappear well behind the stalled flow front and take some time to reach the front again. In this way, the flow front has not advanced more than 1.8 km (1.1 mi) since the first time it stalled in early November, 2013."

The 27 June breakout formed a lava shield high on the Pu'u O'o cone during 28-29 June. A set of HVO photos taken on 26 June and 6 July documented before and after shots of a broad prominent shield. Associated text said the shield made a "dramatic change to the skyline" at Pu'u O'o. The text attributed the growth to the process of successive flows stacked on top of each other in the near vent area. The caption also said that the shield hosted a lava pond.

Photos of Pu'u O'o taken on 18 July addressed a new crater at Pu'u O'o. Since the onset of the "June 27 breakout" flow, the central part of Pu'u O'o's crater had slowly collapsed within a bounding ring fracture. One photo showed the pit formed on the southern side of the crater floor, which contained a small lava pond roughly 10 m across. This pit sporadically overflowed sending lava toward the deeper central part of the crater.

During 16-22 July the lava flow followed an incipient lava tube from the vent to the gentle break in slope at the base of Pu'u O'o, and continued slowly moving in two main lobes that extended about 2 km NE. Two small lava ponds within cones were present within two southeastern pits in the crater floor, and glow above two other pits indicated lava near the surface.

On 23 July the SE wall of Overlook crater fell into the lava lake and triggered an explosive event that threw spatter bombs onto the rim of Halema'ama'u. Ejected material ranged from dust-sized particles to spatter bombs ~70 cm across. The HVO Photos and Video portion of their website featured some dramatic web camera videos of the event. This process repeated again in this middle to late2014 time frame with cases noted on 6 and 23 August, and on 24 September.

A photo of the Pu'u O'o vent area on 26 September appears in figure 232.

Figure 232. Annotated photo taken 26 September 2014 showing Pu'u O'o and the vent and upper lava tube (orange dashed line at far right) for the June 27th lava flow. View is towards the E. Courtesy of HVO.

At 0115 on 19 October another explosion of spatter took place at the lava lake at Halema'ama'u from the lava lake in crater. . A collapse of wall rock fell into the lake, triggering a small explosion. The scar left by this collapse was visible as a light-colored area. The spatter fell around Halema'ama'u crater, which is within an area closed to the public due to hazards like this.

The summit lava lake has shown the usual fluctuations associated with changes in spattering behavior, which are also manifested as variations in tremor amplitudes and gas release. Small amounts of particulate material were carried aloft by the plume.

June 27th lava flow advance towards Pahoa. During the rest of this report, the advancing flow of note was the June 27th lava flow. As noted above, that flow ceased to advance rapidly but remained active near the distal end through the rest of 2014 (and months into 2015). That point is critical because the distal end began to encroach on the W margin of the town of Pahoa.

We present a series of HVO maps in this section, starting with one created to describe the June 27th lava flow (figure 233>).

Figure 233. A map describing lava flows on 27 June 2014. Map showing the Kahauale?a 2 flow (pink) in relation to the E part of the Island of Hawai?i as of 17 June 2014. The most distant active breakout for Kahauale?a 2 lava flow was 7.1 km straight-line distance NE of Pu'u O'o. A new breakout of 27 June (shown in red) started on the NE flank of Pu'u O'o, sending new lava NE. Lava flows emitted since 1983 are labeled on the next figure. The Kahauale?a 2 flow contained an approximately located lava tube, shown with a yellow line (dashed where its position is less well known). Courtesy of HVO.

All of the following maps have several features in common. The yellow line depicts the approximate location of the feeding lava tube (dashed where less certain). When time is referred to, the times are in local (Hawaii Standard) time. Some of the maps contain more details than others on background information such as the age ranges of lava flows going back to the start of this eruption (1983). Figure 234 and its caption explain the color scheme, although some later maps generalize all the older lava flows as one color. A critical detail on figure 234 is that by 30 June, the Kahauale'a 2 lava flow had been declared inactive.

Figure 234. A map describing Kilauea E rift zone and the start of the June 27th lava flow ("breakout") on 30 June 2014. The area of the new flow as mapped on 27 June appears pink, while the extending portion mapped 30 June appears red. The 2013–2014 Kahauale?a 2 flow appears reddish orange. Older lava flows distinguished by color as labeled (episode 1-48b flows (1983–1986) are shown in gray; episodes 48c–49 flows (1986–1992), yellow; episodes 50-55 flows (1992-2007), tan; episodes 58-60 flows (2007-2011), pale orange, and episode 61 flows (2011-2013), very light tan). Courtesy of HVO.

Figures 235 to 237 portray the June 27th lava flow advance from 29 July to 6 September. HVO attributed the surprisingly narrow character of the flow as likely related to the numerous linear cracks and down-dropped structures (grabens) found in this area. In this regard, HVO noted that lava within a linear crack remained hidden for several days but over the day of 25 August lava returned to the surface at a point slightly farther along the crack. The emerging lava created a small island surrounded by thick forest. The farthest tip of the flow that day reached 11.4 km from Pu'u O'o, and 3.1 km from the eastern boundary of the Wao Kele o Puna forest reserve. On 28 August plumes of smoke from burning vegetation marked the farthest active lava on the surface (small, scattered lobes of pahoehoe). In addition, a pad of lava had emerged from the long ground crack that funneled it NE earlier this week. The lava was inactive at its surface but thermal imagery indicated it was still quite warm. East of this pad of lava, steaming appeared on 28 August, suggesting continuing lava advance below the surface along a ground crack. Direct views into the crack were not possible due to thick vegetation, but close views of the steaming areas with a thermal camera revealed temperatures up to 190°C, temperatures interpreted by HVO as evidence of lava moving along a crack. That was confirmed on the 29th when lava again emerged out of a steaming crack. On 1 September lava plunged into another ground crack. On 10 September, the most distal flow front had reached 14.5 km (straight-line distance) from its vent at Pu'u O'o.

Figure 235. A map describing Kilauea's June 27th lava flow on 29 July 2014. The pink area represents lava emplaced by 18 July. The red area represents lava emplaced after that and as late as 29 July. By this time the new flow had advanced while remaining much narrower than the adjacent Kahauale?a 2 flow. The new flow (pink and red zones) had a straight-line length of ~4.4 km. Courtesy of HVO.

Figure 236. A map describing Kilauea's June 27 lava flow on 3 September 2014. The area of the flow as mapped on September 1 is shown in pink, while widening and advancement of the flow as of September 3 is shown in red. On 2 September, lava welled up out of the crack it was filling and spilled out onto the ground to feed new surface flows. As of early afternoon on 3 September, lava on the surface was 13.2 km from the vent and 1.3 km from the E boundary of the Wao Kele o Puna Forest Reserve. All older lava flows (1983-2014) are shown in gray; the yellow line marks the lava tube. Courtesy of HVO.

Figure 237. A map describing the state of Kilauea's June 27th lava flow on 6 September 2014. The larger scale expands the area of coverage to see both the distal part of the lava flow and its relation to nearby Puna communities. This map also depicts the distal ends of the flow at various dates in time. The area of the flow on 3 September is shown in pink, while widening and advancement of the flow as mapped at ~1110 on 6 September is shown in red. The black dots mark the flow front on specific dates. The blue lines show the modeled steepest down-slope paths (see text). The narrowness of the flow was attributed to areas of linear down-dropped zones (grabens) and cracks along the E rift zone. Courtesy of HVO.

Kauahikaua (2007) discussed the use of an appropriate digital elevation model (DEM) to calculate the steepest path of descent along the East rift zone (blue lines in figure 237 and subsequent figures). The basis of that report was a 1983 digital elevation model (DEM). For the case at hand, Bulletin editors are uncertain about the exact dataset used to make the model. Whatever their source, the blue lines on the subsequent maps (below) can be used to infer the approximate directions of the flow's potential advance. These models are imperfect since, for example, the maps have only a finite resolution, and they may lack the updated distribution of lava flows, which themselves change the topography. Kauahikaua (2007) points out that seemingly subtle differences between actual topography and the model may lead to divergence from the modeled lines of steepest descent.

In early September the flow changed its direction of advance. The flow, initially headed almost N along one of the modeled paths of greatest descent (blue lines). By 10 September the direction of advance curved, shifting again more to the E (figure 238). On 3 September, HVO raised the Volcano Alert Level from Watch to Warning, where they both remained during the rest of 2014.

Figure 238. A map describing the state of Kilauea's lava flow on 10 September 2014, but also emphasizing points of farthest advance through August and early September. The distal end of the pink region shows the state of advance as late as 1245 on 8 September 2015. The red region shows advance from that time until about 1445 on 10 September. Blue lines show modeled steepest paths of descent (see text). Courtesy of HVO.

On 15 September, HVO noted that the flow entered a subdivision called the Kaohe Homesteads (figure 239). They said that at this stage the flow was still within the vacant, forested NW portion of subdivision.

Figure 239. A map describing the state of advance for Kilauea's lava flows on 15 September 2014. The area of the flow as of 12 September at 1230 appears in pink. The area of flow advance after that, and as late as 15 September at 1400, appears in red. The active flow reached 15.5 km from the vent and had crossed the Wao Kele o Puna Forest Reserve boundary progressing into the vacant NW corner of Kaohe Homesteads. At this stage, HVO noted, the flow front was situated 4.3 km upslope from Pahoa Village road. HVO also reported the flow length as measured along the curving path of the lava-tube (yellow line) as 17.7 km. The purple arrow shows HVO's short-term projection of flow direction based on topography and recent flow behavior. Blue lines depict the modeled steepest lines of descent (see text). Courtesy of HVO.

By 19 September the flow still progressed NE through Kaohe Homesteads, HVO noted. For the previous several weeks, the flow had been moving through thick forest but around this time the flow front reached the forest boundary (figure 240) and more open ground.

Figure 240. A map (with key) describing the state of Kilauea's lavas on 6 October 2014. Note the Forest Reserve and its boundary (a thin line crossing the flow a few hundred meters E of the 12 September flow front). HVO noted that vegetation density dropped after crossing that boundary. Blue lines depict the modeled steepest lines of descent (see text). Courtesy of HVO.

The flow advanced at an increased rate during 22-23 October, and at 1400 on 24 October the flow front pushed ahead as a narrow lobe reaching ~19 km from the Pu'u O'o vent. The front was 135 m from Cemetery Rd./Apa?a Street, two roads on the W outskirts of town. On 26 October the flow's leading tip advanced through Pahoa cemetery.

During 22-28 October HVO reported that the lava flow remained active. On 22 October a narrow lava flow (less than 50 m wide) that had overtaken the flow front during the previous few days moved into a small gully. It sometimes moved as fast as 300 m/day (many times faster than the typical). Another breakout upslope continued to advance at a slower rate. On 24 October, HVO scientists aboard an overflight measured the cross-sectional area of the lava tube feeding the flow at the vent. Their measurement suggested a slight increase in the lava supplied to the flow.

At approximately 0350 on 25 October lava crossed Apa'a Street and continued to advance towards the town of Pahoa. Throughout the morning the flow moved down the Pahoa cemetery driveway and then turned SE into adjoining pasture. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning. At 0900 on 26 October the flow was an estimated 140 m wide. The next day it had narrowed to 100 m wide and was about 570 m from Pahoa Village Road. At about 0200 on 28 October the flow had reached the first occupied residential property. The leading edge of the flow was less than 50 m wide but increased to 150 m upslope. At 1730 the lava flow was 310 m in a straight-line distance from Pahoa Village Road and about 900 meters in a straight-line distance from Highway 130. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

According to news articles, Pahoa is a town with 800-900 residents, and besides homes, contains small shops. A school and a few roads were closed. Crews were building temporary access roads and trying to build berms to divert lava away from the heavily traveled Highway 130, which passes through the town.

On 2 November, the lava flow front stalled, but scattered breakouts occurred upslope of the flow front. HVO documented in their online Photo and Video section that over the past several days leading up to 7 November, the flow had undergone inflation (thickening).

Although an earlier flow lobe had crossed Apa?a Street / Cemetery Road during October, on 9 November witnesses watched as fresh lava crossed asphalt pavement there, causing combustion with yellow flames and black sooty plumes. HVO cautioned that burning roads creates toxic fumes that can cause eye and respiratory tract irritation, as well as headaches, rashes, cough, and possibly cancer. On 25 October just a few hours after the flow crossed the road, the lava was only about 1 m thick. Ten days later, the flow grew to ~4 m thick.

The next map (figure 241) shows the lava's position as of 10 November 2014 with some earlier dated points of farthest advance indicated. On 10 November a breakout moved along Apa?a Street and onto private property setting an unoccupied home there on fire. According to news sources, this was the first home to be set on fire by the June 27th lava flow. Residents had long ago moved out of the wood frame structure, and had cleared out their belongings. The demise of the structure was widely seen in the news.

Around mid-November a solid-waste transfer station near that portion of the lava flow was the subject of numerous photos, including those documenting flow inflation, burning asphalt pavement, and how a strong cyclone (wire mesh) fence provided a an effective but short-lived barrier. HVO posted a photo disclosing how lava encroached close to the station on 13 November, crossing a fence and most of an access road that loops around the station.

Figure 241. A map (with key) describing Kilauea lava flows on 10 November 2014. On that day, surface activity was present along the N margin in the first few kilometers upslope (W) of the flow tip. For reference, Apa?a Street/Cemetery Road intersects the flow near the breakout farthest to the E. Blue lines depict the modeled steepest lines of descent (see text). Courtesy of HVO.

During an overflight on 1 December volcanologists measured a cross-sectional area of the lava stream within a tube near Pu'u 'O'o. They found a 25% reduction in area compared to the previous week. The result was consistent with less lava flowing through the tube due to summit deflation, which had been ongoing since 29 November.

A 21 December satellite image showed the flow moving towards Pahoa. The image came from the Advanced Land Imager instrument onboard NASA's Earth Observing 1 satellite. The image provided a view of active breakouts on this downslope (E) portion of the flow. Surface lava was active around the leading tip of the flow, but a short distance upslope (W) of the leading tip there was an absence of surface breakouts. About 1.5-2 km W and upslope of the leading tip of the flow, many scattered breakouts were indicated. Thus, HVO concluded, the image emphasizes that lava-flow movement was not limited to the flow front.

Figure 242 shows the lava flow one day before the end of 2014.

Figure 242. A map describing lava flows on 30 December 2014. This large-scale map shows the distal part of Kilauea's active E rift zone lava flow in relation to nearby Puna communities. The area of the flow on 22 December at 1500 is shown in pink; the areas that widened and advanced by 1430 on 30 December are shown in red. Most surface activity was within the leading 3 km of the flow's N lobe, but other small breakouts were scattered the flow in an area 7-8 km W of Pahoa (a region HVO described as just N of the True/Mid-Pacific geothermal well pad). One other breakout, outside the map area, was also active near Pu'u O'o. (As we will discuss in our next Bulletin report on Kilauea, the June 27th flow remained active at least as late as April 2015.) Courtesy of HVO.

At the end of 2014, Kilauea continued to erupt both at its summit and at Pu'u O'o along the East rift zone. An overflight on 1 January 2015 confirmed that the front of the 27 June lava flow remained stalled. However, HVO's Daily Update (issued at 0913 on 1 January) also noted a breakout along the S margin of the flow and 150 m up slope of the flow front, which had advanced ~20 m since the afternoon on the 31st. In addition to the aerial observations, farther back (upslope and W) from the flow front HVO noted that satellite data acquired on 31 December showed areas of activity 3 and 6 km W of the flow front .

Graphical approaches to scientific and hazards communication. The HVO website features a hazard map for Kilauea (HVO, 1997). It shows the relative degree of hazard from lava flows for different areas of the volcano. The E rift zone is within Zone 1, which HVO (1997) states "is the most hazardous; it consists of the summit area and rift zones because Kilauea's frequent eruptions originate in these areas."

As a result of the June 27th lava flow showing no signs of halting, on 3 December 2014, William P. Kenoi, the mayor of the County of Hawaii signed a proclamation that continued the state of emergency in the Puna district. This followed earlier proclamations signed on 4 September and 16 October 2014.

Figure 243 illustrates the advance of the June 27th lava flow from Pu'u O'o towards infrastructure such as Pahoa and the road through it (HI-130). The W-looking view has the advancing lava heading towards the reader. Figure 243 contains both a plot and an image of the June 27th lava flow, with four lobes identified by color coding (as defined on the right side of the figure). The illustration was posted on social media and serves to educate residents (it is not from a peer-reviewed publication). The same author has generated numerous other graphics associated with the advancing lavas and the geography of the Puna district, including relevant census and economic data, in what are often called infographics. Another example, focusing on roads, is figure 244.

Figure 243. Diagram that shows both a plot (at left) and an oblique view of the land surface (at right) summarizing lava advance as of 23 December 2014. In the view at right the colored lines define some of the critical flow lobes. The plot shows position versus time (during 28 June 2014 to 12 January 2015 in 28-day increments). Pahoa (indicated) resides on route 130 (HI-130). Many of the labeled features (Hawaiian Beaches, Rail Road Avenue, and Government Beach Road) may also be seen in figure 239>. Courtesy of Mark Kimura (University of Hawaii at Hilo).

Figure 244. An illustration of approximate drive times between various locations near the June 27th lava flow. The lava covered portion of the Chain of Craters road between Hawaii Volcanoes Nation Park at the W and Kalapana at the E is indicated as the yellow line with red dashes (the gray, lava covered portion, is ~13 km in length). Courtesy of Mark Kimura.

Work began on 24 October 2014 on the emergency access route between Hawai'i Volcanoes National Park and Kalapana along the historic portion of Chain of Craters Road-Kalapana alignment (yellow and red dashed line, figure 244). The lava-covered portion of that road is ~13-km long. According the National Park Service, the emergency route will assist residents of lower Puna district, whose access to the rest of the island would otherwise be cut off if E-flowing lava were to reach the ocean. According to a news article by Damon Tucker, bulldozers working inward from the E and W ends met in the middle on 6 November. The article noted that the roadbed was still considered 'rough grade' and when opened it will be ~6-m wide, 2 lane, and gravel surfaced. The road was intended chiefly for residents (and their agents and service provders) and, as planned, will not be open to the general public or park visitors. On the basis of several reports Bulletin editors found, the road's projected eventual cost varied within the range of 7-15.5 million dollars.

Lava lake heights in Overlook crater. At the summit, a lava lake resides in Overlook crater (see map of the Kilauea summit caldera area in the previous report, figure 229). Overlook crater is a source of ash, spatter, pelee's hair, and this area also vents the bulk of the SO₂; emissions (discussed in a subsection below). HVO Daily Updates describe Overlook crater as a pit or crater in the floor of the larger Halema`uma`u Crater. That crater resides, in turn, on the floor of the larger Kilauea caldera or crater. The pit is about 160 m in diameter at the ground surface on the Halema`uma`u crater floor. At a depth of 200 m below the Halema`uma`u crater floor (the deepest point visible when the lake drains to those depths) the pit is ~50 m in diameter. HVO Daily Updates also said that a lava pond or lake in the pit has been in evidence since November 2009 and through 2014. The surface of the lake moved up and down and measurements reflect the depth below the crater floor.

Overall, from available data during 27 June to 31 December the lake surface ranged between 30 and 70 m below the pit's rim at the Halema'ama'u crater floor. During 27 June to 9 July 2014 the lake remained fairly stable at near 30 m depth below the floor. Starting a few days after that and until 19 September the lake was in the approximate range 30-60 m deep. On 20 September it reached ~65 m deep. During 21-24 September daily distances to the lake surface descended with attendant fluctuations to ~70 m deep. During 25 September to 3 November the lake remained in the range of 40-70 m through the end of the year, although the depths were not specifically given during much of November and December.

HVO Daily Updates contain the following general background explaining more about the lava lake. Overlook crater has been more-or-less continuously active since it opened during a small explosive event on 19 March 2008. Small collapses in the Overlook crater are common, and over time have resulted in a gradual enlargement of the Overlook crater. During 2013 and early 2014, the lava level has been typically between 30 m and 60 m below the floor of Halema`uma`u Crater. The lake level responds to summit tilt changes with the lake generally receding during deflation and rising during inflation.

Geophysical monitoring. Geophysical monitoring, including seismicity at the summit was summarized in HVO Daily Updates during 27 June to 30 December. Located earthquakes in the summit area were most reliably reported only during 27 June through 7 August, an interval when they were often in the range 5 to 36 events per day. After that, the number of events was seldom reported although some comments noted an occasional number or a larger event (e.g., on 14 November, an M ~3.5 earthquake on Kilauea's S flank) and many cases mentioned 'several' located earthquakes or commented on a lack of changes in seismicity without further quantification. Tremor and small seismic swarms were noted often. For example, a swarm of long-period earthquakes occurred during 20-21 August centered beneath the summit caldera at ~8 km depth. Epicenters were reported elsewhere (besides the summit), for example on the S flank and various parts of the E rift zone.

In multiple entries during the reporting interval, episodes of tremor were interpreted by HVO as linked to spatter on the surface of the lava lake.

The 19 October Daily Update made these comments about seismicity, tilt, and summit deformation measured by GPS. "A cluster of small seismic events occurred at a shallow level beneath Kilauea's upper East Rift Zone at about the time that ground tilt switched from inflation to deflation. Such behavior is fairly common. Seismic tremor beneath the summit remained low and varied with changes in spattering on the surface of the lava lake. GPS receivers spanning the summit caldera recorded about 5 cm (2 in) of extension between early May and early July [2014]. Since then, little significant extension or contraction has occurred."

SO₂ flux data. Table 12 contains SO₂ flux data extracted from HVO Daily Updates for the interval 11 June 2014 through 13 January 2015. Near the start of that interval, during 25 June-1 July 2014, SO₂ fluxes at Halema'uma'u yielded the highest values of the interval, 8,400 metric tons per day (t/d). This was about 10% higher than the largest value reported in the first half of 2014 (BGVN 39:09). Overall, SO₂ fluxes for Pu'u 'O'o and associated E rift zone sources of degassing yielded somewhat elevated values. During the week of 25 June to 1 July 2014 scientists recorded fluxes of 900 t/d, about double the higher values HVO typically reported since July 2012.

Table 12. An overview of approximate and preliminary S0₂fluxes reported for Kilauea and some associated comments during 11 June 2014 to 13 January 2015. The majority of these measurements were averages or ranges for a week-long interval recording plumes from gases vented at the summit caldera. "Minor ash" represents cases for summit measurements where HVO noted "a tiny amount of particulate material carried aloft by the plume." Note comment in text below table about the shift in measurement methodology, which resulted in higher values. The measurements in brackets, [ ], record flux estimates on the stated dates from all sources vented on the East Rift Zone (ERZ). For brevity, ERZ measurements during mid-July to mid-September were omitted from the table. All data and quoted text came from HVO Daily Updates (see link in the Information Contacts section).

HVO emphasized the following caveat described in more detail in (BGVN 39:09). "Starting in 2014, [HVO began reporting] the emission rate estimated by a new, more accurate method. The numbers increase by a factor of 2-4 but the actual emission rate has not changed."

The gas plume from the summit area (Kilauea caldera), sometimes included minor amounts of ash-sized tephra (sometimes noted in table 12). These included fresh spatter bits and Pele's hair from the circulating lava lake in Overlook crater. In general, the heaviest tephra deposited near the source; the finer tephra, several kilometers downwind.

References. Kauahikaua, J., 2007, Lava flow hazard assessment, as of August 2007, for Kilauea East Rift Zone eruptions, Hawai'i Island: U.S. Geological Survey Open-File Report 2007-1264, 9 p., ( http://pubs.usgs.gov/of/2007/1264/ )

Kimura, Mark, 23 March 2015, Lower Puna infographics (https://www.facebook.com/lowerpuna) [Accessed in March 2015].

Poland, M.P., Takahashi, T.J., and Landowski, C.M., eds., 2014, Characteristics of Hawaiian volcanoes:

U.S. Geological Survey Professional Paper 1801, 428 p., http://dx.doi.org/10.3133/pp1801.

University of Hawaii at Hilo, 2015, UH Hilo Stories: Puna lava flow in graphics & maps, updated Feb. 22 (http://hilo.hawaii.edu/news/stories/2014/09/22/puna-lava-flow-in-graphics-maps/).

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: https://volcanoes.usgs.gov/observatories/hvo/, Daily Updates, https://volcanoes.usgs.gov/observatories/hvo/activity/Kilaueastatus.php, and (weekly) Volcano Watch, https://volcanoes.usgs.gov/observatories/hvo/volcanowatch/); Recent maps, https://volcanoes.usgs.gov/observatories/hvo/maps); and Mark Kimura, Department of Geography and Environmental Sciences, University of Hawaii at Hilo, Geography Department, 200 W. Kawili St., Hilo, HI 96720-4091.