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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

Merapi (Indonesia) Dome growth, incandescent avalanches, and block-and-ash flows during March-August 2021

Villarrica (Chile) Activity declines; thermal anomalies persist during March-August 2021

Erta Ale (Ethiopia) Episodes of strong thermal signals from lava lakes during March and May 2021

La Palma (Spain) First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Telica (Nicaragua) Weak explosions and minor ash plumes during April-July 2021

Yasur (Vanuatu) Gas-and-ash explosions, SO2 plumes, and thermal anomalies during March-August 2021

Ibu (Indonesia) Intermittent low-level ash plumes, light ashfall, and thermal anomalies during January-August 2021

Suwanosejima (Japan) Intermittent explosions send incandescent ejecta 1 km from summit during January-June 2020

Kadovar (Papua New Guinea) Intermittent ash plumes and thermal anomalies during January-August 2021

Bezymianny (Russia) Frequent gas-and-steam emissions and a weak thermal anomaly during March-August 2021

Bagana (Papua New Guinea) Intermittent thermal anomalies continue and a possible lava flow during March 2021

Etna (Italy) Strombolian explosions, ash plumes, lava fountaining, and flows during April-July 2021



Merapi (Indonesia) — September 2021 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Dome growth, incandescent avalanches, and block-and-ash flows during March-August 2021

Merapi volcano in central Java, Indonesia, has a lengthy history of major eruptive episodes. Activity has included lava flows, pyroclastic flows, lahars, Plinian explosions with heavy ashfall, incandescent block avalanches, block-and-ash flows, and dome growth and destruction. Fatalities from these events were reported in 1994, 2006, and in 2010 when hundreds of thousands of people were evacuated. Renewed phreatic explosions in May 2018 cancelled airline fights and generated significant SO2 plumes. A new lava dome appeared in early August 2018; gradual dome growth and destruction was accompanied by block avalanches, block-and-ash flows, periodic explosions, and pyroclastic flows. Two new domes appeared in early 2021, one inside the summit crater and one at the top of the SW flank. Activity during March-August 2021 is covered in this report with Information provided by Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG which specifically monitors Merapi, the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, and the Darwin Volcanic Ash Advisory Centre (VAAC).

Two lava domes at the summit continued to grow during March-August 2021. On 17 February 2021 the volume of the dome on the SW flank was 397,500 m3, and the volume of the dome at the center of the summit crater was 426,000 m3. Six months later, on 1 September 2021, the SW dome volume was estimated at 1,440,000 m3 and the central dome volume was 2,842,000 m3 (figure 110). Tens of daily block avalanches, many incandescent, were recorded throughout the period, generally traveling 500-2,000 m down the flanks. Most of the activity was related to the SW flank dome, but there were also periods of activity on the SE flank produced by the central dome. Tens of block-and-ash flows also occurred each month, moving down the SW and SE flanks, some as far as 3 km from the summit. Ash from explosions and block-and-ash flows occasionally produced ashfall. Ash emissions increased substantially at the end of July and throughout August; the plumes resulted in ashfall over a larger area multiple times during August. The MODIS Log Radiative Power graph produced by the MIROVA project shows a marked increase in thermal activity during July and August (figure 111), corresponding to the increased number incandescent block avalanches and block-and-ash flows.

Figure (see Caption) Figure 110. The active dome inside the summit crater at Merapi is visible within the steam plumes rising from the summit on 8 August 2021. The volumes of both the center dome and the SW flank dome continued to grow throughout March-August 2021. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 111. The MIROVA graph of Log Radiative Power for Merapi from 15 November 2020 through August 2021 showed a steady increase in thermal energy throughout the period. Explosive activity produced an increasing number of incandescent block avalanches and block-and-ash flows into August. Courtesy of MIROVA.

The number of daily block avalanches during March 2021 ranged from a high of 210 on 5 March to a low of 97 on 20 March. On 6 March incandescent blocks were observed 24 times on the SW flank, traveling up to 1,000 m and on 8 March they were noted 20 times in the same place. Every day from 16 March through the end of the month, multiple incandescent block avalanches were reported. Most frequently, they descended 800-1,200 m down the SW flank, and were also periodically observed inside the summit crater on the growing central dome. Sentinel-2 satellite imagery showed a faint thermal anomaly on the SW flank on 19 March (figure 112), likely due to incandescent blocks and block-and-ash flows. Larger explosions on 27 March produced 27 incandescent block avalanches, with another 33 observed on 30 March.

Figure (see Caption) Figure 112. A faint thermal anomaly on the SW flank of Merapi near the summit on 19 March 2021 was likely caused by incandescent block avalanches from the growing SW-flank dome. Image uses Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Thirty-four different block-and-ash flows were reported on 14 days of March, usually one or two in a day. On 8 March, three block-and-ash flows traveled 1,300 m down the SW flank. Eight block-and-ash flows on 27 March extended 1,800 m down the SW flank (figure 113). On 30 March one block-and-ash flow traveled 1,500 m down the SW flank. During the last week of the month small amounts of ashfall were reported in Ngadirojo, Stabelan (4 km NW), Takeran, Tlogolele (5 km NW), Selo (3 km NNW), Pos Babadan (4 km NW), and Pasar Talun (12 km W), and around Talun Market. Based on photos taken from the SW flank, the summit dome grew from 45 m high on 11 March to 70 m high on 1 April. The Darwin VAAC issued an ash advisory on 27 March based on a ground report of ash emissions that rose to 3.7 km altitude. PVMBG reported the ash plume 500 m above the summit.

Figure (see Caption) Figure 113. Eight block-and-ash flows were recorded at Merapi on 27 March 2021, producing minor ashfall to the NW and sending incandescent blocks down the SW flank. Courtesy of MAGMA Indonesia.

Over 100 block avalanches occurred each day during April 2021, with few exceptions. The fewest, 74, occurred on 17 April, and the most, 225, occurred on 23 April. Incandescent block avalanches usually traveled 400-800 m down the SW flank. Sixteen were reported by BNPB on 2 April, and twenty were observed on 8 April, moving 700-1,000 m down the SW flank. On 12 April there were 29 incandescent block avalanches reaching 1,000 m down the SW flank; five more were observed 400 m down the SE flank. A total of 43 block-and-ash flows were noted on 17 days during the month, usually traveling 700-1,500 m from the summit. BNPB reported three block and ash flows on 2 April to a distance of 700-1,500 m down the SW flank (figure 114). Four of them traveled 1,800 m down the SW flank on 13 April and six traveled 1,300 m from the summit on 20 April; four moved 1,000-2,000 m down the SW flank on 23 April. Small amounts of ashfall were reported in Ngipiksari, Klangon, and Deles on 3 April 2021. An explosion on 23 April produced block-and-ash flows that traveled 2 km down the SW flank, produced an ash plume that rose 300 m above the summit, and caused ashfall in the Cepogo area of the Boyolali Regency in central Java.

Figure (see Caption) Figure 114. Sixteen incandescent block avalanches and three block-and-ash flows were reported on 2 April 2021 at Merapi. Courtesy of BNPB.

Between 101 and 165 block avalanches were recorded daily during May 2021. PVMBG reported block-and-ash flows traveling 1,700 m on the SW flank on 1 May, and incandescent blocks traveling 600 m down the SW and SE flanks. Incandescent blocks and block-and-ash flows were observed daily during 4-9 May moving 700-2,000 m on the SW flank, and 700 m on the SE flank on 9 May. Similar activity occurred during 14-19, 22, and 27-31 May. Seventeen days of the month had block-and-ash flows, with a total of 31 reported.

The number of block avalanches reported each day during June 2021 ranged from 103 on 1 June to 377 on 30 June. The number was between 100-200 during the first half of the month but rose to over 200 about half the time during the second half of the month, with two days over 300 reported. Incandescent block avalanches were observed multiple times every day with blocks sliding 500-2,000 m down both the SW and SE flanks. Block-and-ash flows also increased in number and frequency during June, compared with the previous months. A total of 85 were reported on all but four days of the month. During most days 1-5 were reported, except 17 were noted on 30 June. The block-and-ash flows sent debris 900-3,000 m down the SW and SE flanks (figure 115). BNPB reported two block-and-ash flows early on 20 June that traveled 2,500 and 1,500 m down the SW flank. Four block-and-ash flows traveled 3 km SE on 25 June (figure 116). The larger explosions that day produced an ash plume that rose to 1 km above the summit (3.9 km altitude) and drifted SE resulting in ashfall in several areas on the SE flank. An ash emission on 29 June rose to 3.4 km altitude and drifted W. The next day 17 block-and-ash flows descended 900-1,500 m down both the SW and SE flanks.

Figure (see Caption) Figure 115. Incandescent block avalanches and block-and-ash flows at Merapi produced significant thermal anomalies on both the SW and SE flanks on 7 (left) and 27 (right) June 2021. Sentinel-2 satellite images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 116. Four block-and-ash flows sent debris 3 km SE at Merapi on 25 June 2021. Courtesy of BNPB.

For the first 20 days of July, the daily number of block avalanches was usually over 200, reaching a high of 338 on 10 July. Multiple incandescent block avalanches occurred on both the SW and SE flanks, extending as far as 2 km on many days (figure 117). Far fewer block-and-ash-flows occurred in July than were reported in June; only 19 during 1-5, 9, 26, and 29 July moving as far as to 2 km down the SW flank. BNPB reported block-and-ash flows on 8 and 9 July that traveled 1,100 m down the SW flank. The Darwin VAAC reported an ash emission on 24 July that rose to 3.0 km altitude and drifted WSW. Incandescent block avalanches caused fires on the SW flank on 25 July about 2.5 km from the summit.

Figure (see Caption) Figure 117. Multiple incandescent block avalanches descended both the SW and SE flanks of Merapi during July 2021. On 12 July the blocks traveled 1,700 m down the SW flank and 1,200 m down the SE flank creating significant thermal anomalies in this Sentinel-2 image that uses Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Incandescent block avalanches were reported daily during August, reaching 1-2 km down the SW flank (figure 118). The number of daily block avalanches reported ranged from 61 to 385, exceeding 200 every day after 8 August (figure 119). Fifty-one block-and-ash flows were observed during sixteen days of August. Six were reported on 5 August, 7 on 12 August and 9 on 13 August. During other days 1-3 were observed. Most were reported moving 1,400 m down the SW flank. The largest events on 8, 10, and 12 August produced block-and-ash flows that traveled 2.5-3 km from the summit. They also traveled over 2 km from the summit on the SW flank on 13-15, 20, and 28 August.

Figure (see Caption) Figure 118. A large number of incandescent block avalanches and block-and-ash flows descended the SW flank of Merapi during August 2021. They were detected as large thermal anomalies in Sentinel-2 satellite images on 11 (left) and 16 (right) August. In addition, smaller anomalies were present at the summit crater dome. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub playground.
Figure (see Caption) Figure 119. Incandescent block avalanches traveled hundreds of meters down the SW flank of Merapi daily throughout August, including on 24 August 2021, shown here. Courtesy of MAGMA Indonesia.

The number of ash emissions increased significantly during August 2021, and ashfall was reported in surrounding communities on multiple occasions. The Darwin VAAC noted ash emissions continuously during 6-11, 14-19, and 28-29 August. They reported a minor ash emission visible in the webcam on 3 August that was not observed in satellite data, although a significant hotspot was apparent. An ash emission on 6 August rose to 4.3 km altitude and drifted SE. The next day a new emission rose to 3.7 km altitude and drifted NW; it was still clearly visible in satellite imagery early on 8 August moving WNW. Multiple discrete emissions were identifiable in satellite imagery throughout the day at 3.9 km altitude drifting W. An emission on 9 August rose to 3.0 km altitude and drifted WNW. The next day an emission that rose to 3.9 km altitude was discernible on multispectral satellite imagery. This was followed by another ash plume moving NW at 4.3 km altitude. On 11 August ash was observed in satellite imagery drifting NW at 3.0 km altitude. Later that day a plume appeared in satellite imagery moving SW at 4.3 km altitude. A new ash emission rose to 3.0 km altitude and drifted WSW on 14 August; the next day one rose to 3.7 km and drifted W. Ash to a similar altitude drifted W on 16 August and continued to be observed through 18 August, drifting SW (figure 120). On 19 August block-and-ash flows produced an ash plume near summit. Continuous ash emission was reported on 28 August drifting SW and W at 3.7 km altitude. An ash plume rose to 3.0 km altitude and drifted SW late in the day and continued into 29 August drifting NW before dissipating.

Figure (see Caption) Figure 120. Continuous ash emissions were reported by the Darwin VAAC during 14-19 August 2021 at Merapi. On 17 August block-and-ash flows descended the SW flank while dense white steam and diffuse ash rose from the summit area and drifted W. Courtesy of MAGMA Indonesia.

BNPB reported that 19 villages received ashfall on 11 August after block-and-ash flows traveled 2.5 km down the SW flank, sending ash emissions to 4.3 km altitude the previous day (figure 121). The communities were located in the Magelang Regency of central Java and included Paten and Sengi Villages in Dukun District; Ketep and Wonolelo Villages, Sawangan District; Pakis, Gejagan, Rejosari, Banyusidi, Ketundan, Petung and Daleman Kidul Villages in Pakis District; Pucungsari, Pesidi, and Lebak Villages in Grabag District; Kaliurang Village in Srumbung District; Kebonagung Village in Tegalrejo District; and Karangkajen, Donorejo, and Krincing Villages in the Secang District. On 10 and 12 August ashfall was also reported in Salam, Muntilan, and Mungkid. During the week of 13-19 August there were 20 block-and-ash flows that sent blocks as far as 3.5 km. Ashfall was reported on 16 August in the Dukun, Sawangan, Tegalrejo, Secang, Gowok, and Mertoyudan sub-districts in the Magelang District, and also in Selo, Boyolali, and Mojotengah in Wonosobo District. In addition, the sub-districts of Temanggung, Kedu, Pringsurat, Bulu, Tlogomulyo, Kranggan, and Parakan in Temanggung Regency were affected by ash. Ashfall was reported on 28 August and 1 September in several areas including in Srumbung, Salam, Ngluwar, Dukun, Mungkid, Sawangan, Muntilan, and Salaman sub-districts.

Figure (see Caption) Figure 121. Substantial ash emissions from block-and-ash flows on the SW flank of Merapi on 10 August 2021 produced ashfall in numerous nearby villages. Courtesy of PBBTKG.

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 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent 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.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); 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/); 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/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Villarrica (Chile) — September 2021 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Activity declines; thermal anomalies persist during March-August 2021

Eruptions documented at Chile's Villarrica since 1558 have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. An intermittently active lava lake at the summit has been the source of Strombolian activity, incandescent ejecta, and thermal anomalies for several decades; the current eruption has been ongoing since December 2014. Continuing low-level activity during March-August 2021 is covered in this report, with information provided by the Southern Andes Volcano Observatory (Observatorio Volcanológico de Los Andes del Sur, OVDAS), part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a private research group that studies volcanoes across Chile. Sentinel satellite imagery also provided valuable data.

Activity decreased at Villarrica during March-August 2021, with no explosions reported, and rare incandescence at night. Low levels of seismicity, emissions, SO2, and thermal activity led SERNAGEOMIN to lower the Alert Level from Yellow to Green (on a 4-Level scale) in mid-April, and reduce the warning area to 100 m around the summit crater. They reported that analysis of satellite data in late February 2021 indicated that the surface of the lava lake was about 70-80 m below the crater rim. Persistent weak thermal anomalies in satellite data suggested that the lava lake remained at a deep level throughout the period.

Incandescence at night was reported once during the first half of March, and then not again through August. The number of LP seismic events decreased steadily each month from 6,986 events recorded during March to 172 events recorded during August 2021. Tremor and acoustic signals remained low, and VT seismic events were intermittent with six reported in early March, one or two each month during April-June, 4 in July, and 11 in August. Emissions were white, of variable intensity, and with little or no particulate material. Plumes reached about 1,000 m above the crater most months, dropping to less than 600 m during July and August. Thermal anomalies in Sentinel-2 satellite data were the only consistent evidence of activity throughout the period; anomalies were present in all clear satellite images. The intensity of the anomalies varied, and occasional steam plumes were also present (figure 114). A single series of thermal images from the POVI infrared webcam on 7 August was consistent with the interpretation of the deep level of the lava lake within the crater (figure 115).

Figure (see Caption) Figure 114. Thermal anomalies of varying intensity appeared in all clear Sentinel-2 satellite images of Villarrica during March-August 2021. A weak anomaly on 15 April (left), a steam plume with an anomaly on 17 June (center), and a bright anomaly on 8 August (right) show the range of values. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 115. Low levels of incandescence recorded by the POVI webcam at Villarrica on 7 August 2021 were characteristic of the lava lake surface being located near the bottom of the crater. Courtesy of POVI.

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Erta Ale (Ethiopia) — October 2021 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Episodes of strong thermal signals from lava lakes during March and May 2021

Erta Ale, Ethiopia’s most active volcano in one of the most desolate regions on Earth contains two active craters with lava lakes (North Pit and South Pit) in the summit caldera. Since February 2020, volcanism has been relatively low, except for a brief surge of thermal activity at the end of November 2020 (BGVN 45:05, 45:10, 46:02). This report summarizes activity during March-August 2021 and is based on satellite data.

During the reporting period, thermal anomalies based on MODIS satellite instruments analyzed using the MODVOLC algorithm, recorded frequent thermal alerts during 19-31 March, including ten days of hotspots with up to 4 pixels (figure 104). The March hotspots were the first since 30 November 2020. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system recorded a heavy concentration of strong thermal anomalies during the second half of March and a smaller pulse (less radiative power and fewer anomalies) of activity during the second half of May, with a few scattered hotspots during other months (figure 105).

Figure (see Caption) Figure 104. Location of thermal anomalies at Erta Ale in March 2021 detected by MODIS satellite instruments. Courtesy of HIGP MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 105. Log radiative power time-series plot of thermal anomalies from Erta Ale for the year ending 4 August 2021, as recorded by the MIROVA system. A strong pulse of activity during the second half of March is evident, along with a smaller (weaker and less frequent) group of anomalies in the second half of May; a single anomaly was detected on 26-27 July 2021. Courtesy of MIROVA.

Sentinel-2 infrared images also showed thermal anomalies suggestive of lava lakes present in both N and S crater pits during March through July 2021 (figure 106). A weak thermal signal can be seen on both 4 and 9 March from the S pit, which was much stronger on 19 March. Only five days later, on 24 March, a much strong thermal signal appeared in the N crater. Additional strong thermal anomalies at the N pit were detected on 29 March, 23 April, and 18 May. The S pit showed a strong thermal anomaly on 27 July. Small weaker anomalies were frequently present at one or both craters through August 2021.

Figure (see Caption) Figure 106. Sentinel-2 thermal satellite images of Erta Ale during 9 March to 27 July 2021 showing thermal anomalies in both N and S pit craters of the summit caldera. Top left: Faint thermal anomaly in the S pit crater on 9 March. Top right: Strong thermal anomaly in the S pit crater on 19 March. Center left: Strong thermal anomaly in the N pit crater and weak anomaly in the S pit on 24 March. Center right: Weak thermal anomaly in the S pit crater on 13 May. Bottom left: Strong thermal anomaly in the N rater on 18 May. Bottom right: Strong thermal anomaly in the S crater on 27 July. Sentinel-2 images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground. 

Geologic Background. The Erta Ale basaltic shield volcano is the most active in Ethiopia, with a 50-km-wide edifice that rises more than 600 m from below sea level in the barren Danakil depression. It is the namesake and most prominent feature of the Erta Ale Range. The volcano includes a 0.7 x 1.6 km elliptical summit crater hosting 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 usually also holds at least one long-term lava lake that has 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/).


La Palma (Spain) — October 2021 Citation iconCite this Report

La Palma

Spain

28.57°N, 17.83°W; summit elev. 2426 m

All times are local (unless otherwise noted)


First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Multiple eruptions have occurred during the last 7,000 years at the Cumbra Vieja volcanic center on La Palma, the NW-most of the Canary Islands. The eruptions have created cinder cones and craters, and produced fissure-fed lava flows that reached the sea a number of times. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas, most recently at the southern tip of the island in 1971. During the three-week eruption in October-November 1971, eruptive activity created a new cone, Teneguia, that had as many as six active vents (CSLP 90-71), and blocky lava flows that reached the sea on the SW flank.

A new eruption began at La Palma on 19 September 2021 in an area on the SW flank of the island about 20 km NW of the 1971 eruption, after a multi-year period of elevated seismicity. Two fissures opened and multiple vents produced lava fountains, ash plumes, and flows that traveled over 5 km W to the sea, destroying hundreds of properties in their path (figure 2). Activity through the end of September is covered in this report with information provided by Spain’s Instituto Geographico Nacional (IGN), the Instituto Volcanologico de Canarias (INVOLCAN), the Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA), maps from Copernicus EMS, satellite data, and news and social media reports.

Figure (see Caption) Figure 2. A 3D-rendering of the extent of lava flows from the Cumbra Vieja eruption on La Palma as of 15 October 2021 is shown in red with flows from earlier eruptions shown in tan. Data provided by Copernicus EMS and IGN, courtesy of INVOLCAN.

Precursor seismicity. In early July 2017 IGN enhanced their Volcanic Surveillance Network at La Palma to include four GPS antennas, five seismic stations, and four hydrochemical groundwater control points. A seismic swarm of 68 events located on the southern third of the island was recorded during 7-9 October 2017. It was the first of a series of seismic swarms recorded during 2017-2021 (table 1) located in the same general area. This first swarm was followed by a similar set of events a few days later during 13-14 October. The magnitudes of the events during October 2017 (given as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude) ranged from less than 1.5 to 2.7, and they occurred over a depth range of 12-35 km. The next seismic swarm of similar characteristics occurred during February 2018, followed by a smaller swarm of seven microseismic events recorded in the same area one year later, on 12 February 2019.

Table 1. Precursor seismicity episodes at La Palma between October 2017 and late June 2021 were all located in the southern third of the island. Magnitude is reported by IGN as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude. Data courtesy of IGN Noticias.

Date Detected Events Located Events Magnitude Range (mbLg) Depth Range (km)
07-09 Oct 2017 -- 68 Less than 1.5-2.7 12-35
13-14 Oct 2017 352 44 Less than 1.5-2.1 15-22
10-14 Feb 2018 -- 85 1.8-2.6 25-30
12 Feb 2019 -- 7 0.7-1.1 15
24 Jul-02 Aug 2020 682 160 1.2-2.5 16-39
23-26 Dec 2020 602 126 1.3-2.3 30
31 Jan 2021 -- 27 1.2-2.5 10-29
25 Jun 2021 80 12 Less than 2.2 18-34

By the time the next seismic swarm began in July 2020, IGN had a network of 13 seismic stations installed around the island. There were 160 located events that occurred during 24 July-2 August 2020 with magnitudes of 1.2-2.5 and depths of 16-39 km. Reprocessing of the previous data indicated a distribution of seismicity for the three series (October 2017, February 2018, and July 2020) in a wide strip in an east-west direction, although the October 2017 series occurred at a shallower depth and with the epicenters more concentrated. IGN noted similarities between the February 2018 and July-August 2020 events in terms of location and magnitude (figure 3). Another very similar swarm of 602 detected events was recorded during 23-26 December 2020, with most events located on the western slope of Cumbre Vieja. Two swarms on 21 January and 25 June 2021 had fewer events but similar depths and magnitudes to the earlier events.

Figure (see Caption) Figure 3. Comparison of seismic event depth and locations at La Palma from swarms during 2017, 2018, and 24 July-2 August 2020. Courtesy of IGN (06-08-2020 16:45 UTC, Final de la actividad en La Palma).

Renewed seismicity began on 11 September 2021. The number, frequency, and magnitude of the events all increased over the next several days, while the depth of the events grew shallower. On 13 September a multi-agency scientific committee raised the Alert Level to Yellow (the second lowest level on a four-color scale) for the municipalities of El Paso, Los Llanos de Aridane, Mazo, and Fuencaliente de la Palma. IGN noted a migration of the seismicity toward the W side of the island on 14 September (figure 4). The accumulated surface deformation between 12 and 14 September measured 1.5 cm from the island GNSS network. Seismic activity on 15 September continued to migrate slightly NW at depths of around 7-9 km; in addition, 20 shallow earthquakes of 1-3 km depth were recorded. The accumulated deformation had reached 6 cm by 15 September. As of 0930 on 16 September 50 shallow earthquakes between 1-5 km depth had been located and the maximum vertical deformation was around 10 cm in the area of the seismicity. During 16-18 September seismic activity decreased, but a 3.2 magnitude earthquake located at 100 m depth was felt by the local population. Intense surface seismicity (between 0-6 km) increased in the early hours of 19 September and numerous earthquakes were felt by the local population (figure 4). The maximum accumulated deformation increased to 15 cm in the area close to the seismicity by 1100 on 19 September, and the eruption began about five hours later.

Figure (see Caption) Figure 4. Seismic events at La Palma during 12-19 September 2021 showed distinct changes during those days. During 12-14 September (left) the seismicity migrated westward and was located at depths of about 7-13 km. The color scale on the left indicates the time of the events in hours before 0925 on 14 September, with red as the most recent. An abrupt increase in shallow seismicity on 19 September 2021 occurred a few hours before the eruption began, as shown by the bright orange dots in the right image. The color bar on the right represents the dates of the seismic events beginning on 11 September. Courtesy of IGN (left: 14-09-2021 09:30 UTC, right: 19-09-2021 11:00 UTC, Actualización de la información sobre la actividad volcánica en el sur de la isla de La Palma).

Eruption begins 19 September 2021. A fissure eruption began at 1510 local time (1410 UTC) on 19 September after the intense seismic and deformation activity that began on 11 September. Observers near the eruption site in the area of Cabeza de Vaca, in the municipality of El Paso, witnessed a large explosion with ejecta that produced a gas-and-ash plume. Strombolian activity was accompanied by phreatomagmatic pulses along two 100-m-long N-S fissures about 200 m apart. INVOLCAN scientists observed seven vents along the fissures during the initial stage of the eruption (figure 5). Multiple tall lava fountains fed flows downslope to the W, igniting fires. The PEVOLCA steering committee briefly raised the Alert Level to Orange, and then to Red by 1700 for high-risk municipalities directly affected by the eruption. About 5,500 people evacuated with no injuries reported, and authorities recommended that residents stay at least 2 km from the vents. INVOLCAN scientists determined an average flow rate of 700 m/hour and lava temperatures of around 1,075°C at the start of the eruption (figure 6).

Figure (see Caption) Figure 5. INVOLCAN scientists observed seven active vents along the fissure at the start of the La Palma eruption at Cumbre Vieja on 19 September 2021. Photo by Alba, courtesy of INVOLCAN.
Figure (see Caption) Figure 6. INVOLCAN scientists determined a flow rate for the new lava flows at La Palma on 19 September 2021 of 700 m/hour and a temperature of 1,075°C. Courtesy of INVOLCAN.

The Toulouse VAAC issued the first ash advisory for the La Palma eruption about 90 minutes after it began. They reported ongoing lava fountains and an ash plume to about 1 km altitude. The plume drifted SW at less than 1.5 km altitude, while SO2 emissions were reported drifting ESE at 3 km altitude. Later that day, they noted continuing intense lava fountains and ashfall in the vicinity of the volcano. The next day ash emissions drifted S at 2.4 km altitude. Sulfur dioxide emissions were measured by satellite instruments beginning on 19 September; they increased dramatically and drifted hundreds of kilometers E and SE toward the NE coast of Africa over the next few days (figure 7). Ongoing ash emissions rose to 4.6 km altitude later on 20 September. The first Sentinel-2 satellite images of the eruption appeared on 20 September showing a strong point source thermal anomaly partly covered by meteoric clouds (figure 8).

Figure (see Caption) Figure 7. Sulfur dioxide emissions from the Cumbre Vieja eruption at La Palma were measured by the TROPOMI Instrument on the Sentinel-5P satellite beginning on 19 September 2021 (left); they increased dramatically over the next several days. The plume was detected by satellite over 400 km SE over the western Sahara on the NW coast of Africa by 20 September. The plume was reported as visible at Gomera Island (80 km SE) on 21 September, having increased significantly in area and mass from the previous day. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 8. Sentinel-2 satellite images of La Palma show a sharp contrast from a cloudless sky before any signs of surface activity on 10 September 2021 (left) to dense cloud cover on the lower slopes of La Palma with a strong thermal anomaly from the new fissure vent and flows with rising steam plumes drifting NE on 20 September (right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

The first map of the new flow on 20 September produced by IGN in partnership with Copernicus Emergency Management Service (EMS) showed that the main channel of the lava flow had traveled more than 3 km W. The flows had covered about 1 km2 and destroyed an estimated 166 buildings (figure 9). A report of the PEVOLCA Scientific Committee indicated that activity on 20 and 21 September was concentrated at four main vents that produced parallel flows with an average flow rate of 200 m/hour; the maximum flow thickness was 10-12 m (figure 10). Strong lava fountaining continued both days and ash fell in the vicinity of the vents. By 0814 on 21 September an updated Copernicus EMS map showed that 350 homes had been covered by lava and the flow field had expanded to 1.54 km2. A few hundred more residents evacuated as lava advanced towards Tacande; bringing the number of evacuees to about 5,700. One lava flow branch was advancing slowly S at a rate of 2 m/hour. An ash cloud was observed later that day on the W flank of the volcano slowly drifting SW at 2.4 km altitude. Sulfur dioxide emissions were present over the SE part of the island and were visible at Gomera Island, 80 km SE. Late in the day, ash was observed in satellite imagery about 50 km W of the volcano, while intense lava fountaining continued at the source vent (figure 11).

Figure (see Caption) Figure 9. The first map of the new lava flow at La Palma on 20 September 2021 was produced by the Copernicus Emergency Management Service (EMS) in partnership with IGN. It showed that the main channel of the lava flow shown in red had traveled more than 3 km W covering about 1 km2 and had destroyed an estimated 166 buildings. Courtesy of Copernicus EMS.
Figure (see Caption) Figure 10. INVOLCAN scientists collected lava fragments from the Cumbre Vieja flow front at La Palma on 21 September 2021. The average flow thickness was 10-12 m. Courtesy of INVOLCAN.
Figure (see Caption) Figure 11. Intense fountaining continued at the vent of the Cumbre Vieja eruption on La Palma during the night of 21 September 2021; multiple small flows descended the flanks of the growing pyroclastic cone. Courtesy of Cabildo La Palma.

Activity during 22-25 September 2021. Ash emissions during 22 and 23 September drifted SW and S from 0-3 km altitude, and NE and E from 3-5 km altitude (figure 12); ashfall up to 3 cm thick was reported downwind. An SO2 plume was also noted drifting NE in satellite imagery. PEVOLCA reported on 23 September that two relatively slow-moving lava flows continued to advance downslope from the vent (figure 13). The northernmost flow was moving at 1 m/hour and was 12 m high and 500 m wide in some places. The southern flow, which surrounded Montaña Rajada, was moving at 4-5 m/hour and about 10 m high. The overall flow was 3.8 km long and 2.1 km from the coast (figure 14). By late on 23 September reports indicated 420 structures had been destroyed and the flow covered just under 2 km2.

Figure (see Caption) Figure 12. Ash emissions rose as high as 4.6 km altitude on 22 September 2021 at La Palma. Up to 3 cm of ashfall was reported downwind. Courtesy of El Periodico de Cataluny, S.L.U.
Figure (see Caption) Figure 13. Slow moving lava flows at La Palma continued downslope from the vents on 22 and 23 September 2021. Many businesses and homes in the community of Todoque, shown here, were destroyed by the lava flows on 22 September. Photo by Bomberos de Canarias, courtesy of RTVE.
Figure (see Caption) Figure 14 The original flow at La Palma as of 1913 on 20 September is shown in red. The progression of the lava flows each day from 20-23 September 2021 is shown in different colors. Lava flows covered almost 2 km2 of La Palma by the end of the day on 23 September 2021, and reports indicated 420 structures and 15.2 km of roads had been destroyed. The flow was about 3.8 km long and still 2.1 km from the coast. Courtesy of Copernicus EMS.

Lava fountains rose hundreds of meters above the summit crater of the new cone early on 24 September 2021 (figure 15). IGN reported an increase in explosive activity on 24 September that was accompanied by a sharp increase in tremor amplitude. This was followed a short while later by the opening of two new vents on the NW flank of the cone; the fast-moving flows merged into one and produced a new flow over top of the earlier flows. Part of the upper section of the S flank of the cone collapsed on 24 September and briefly caused flow speeds to increase to 250-300 m/hour overnight before slowing to an average speed of 40 m/hour. Due to the fast-moving flow, an evacuation order was issued in the early afternoon for Tajuya, Tacande de Abajo, and part of Tacande de Arriba, affecting 300-400 people. Three airlines also suspended flights to La Palma. The Toulouse VAAC reported ash plumes throughout the day. Ash plumes drifted SW below 3 km altitude and E and SE at 3-5.2 km altitude and resulted in significant ashfall in numerous locations by the next morning (figure 16). Pilots also reported ash near Tenerife and over La Gomera.

Figure (see Caption) Figure 15. Lava fountains several hundred meters high rose from the growing pyroclastic cone at La Palma in the early hours of 24 September 2021, seen from Tajuya. Dense ash emissions continued throughout the day. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 16. Ashfall in El Paso on La Palma covered cars and flowers on the morning of 25 September 2021. Ash emissions produced ashfall in numerous places around the island over the next several days. Courtesy of Volcanes de Canarias.

By 25 September there were three active vents in the crater and one on the flank of the cone (figure 17), and two active lava flows. On 25 and 26 September dense ash emissions (figure 18) closed the airport and produced ashfall not only in the municipalities near the eruption, but also on the eastern slope of the island; it was reported in Villa de Mazo, Breña Alta and Breña Baja, and Santa Cruz de La Palma or Puntallana. Plumes were drifting SW at altitudes below 1.5 km and NE between 1.5 and 3.9 km altitude over a large area. Mapping by Copernicus EMS indicated that the ashfall covered an area of 13 km2 (figure 19).

Figure (see Caption) Figure 17. A new vent opened on the lower W flank of the pyroclastic cone at La Palma on 25 September 2021. Courtesy of INVOLCAN.
Figure (see Caption) Figure 18. Dense ash emissions on 25 September 2021 at La Palma forced closure of the island’s airport. Photo by Desiree Martin, AFT, courtesy of Corporación de Radio y Televisión Española (RTVE).
Figure (see Caption) Figure 19. A large area of La Palma, shown in blue, was affected by ashfall to the W and SW of the erupting vent on 25 September 2021. The extent of the lava flow as of 1913 UTC on 20 September is shown in red, and the extent of the flow by 1206 on 25 September is shown in orange. Courtesy of Copernicus EMS.

Activity during 26-28 September 2021. During the evening of 26 September jets of lava up to 1 km high were visible from La Laguna and some explosions were strong enough to be felt within 5 km of the vent (figure 20). The main, more northerly lava flow overtook the center of Todoque, in the municipality of Los llanos de Aridane, which had been evacuated several days earlier. It crossed the highway (LP-213) in the center of town and continued 150 m W. It was initially moving at about 100 m/hour, was 4-6 m high, and the front was about 600 m wide, but it slowed significantly after crossing through Todoque, and the height grew to 15 m; it was located about 1,600 m from the coast. The more southerly flow continued moving at about 30 m/hour and was about 2.5 km long.

Figure (see Caption) Figure 20. Jets of lava rose to nearly 1,000 m high at La Palma as seen from La Laguna on the evening of 26 September 2021. The lava flow remained active on the NW flank of the cone. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

The PEVOLCA Scientific Committee determined that the volume of erupted material from the beginning of the eruption on 19 September until 27 September was about 46.3 m3. By early on 27 September the front of the flow was close to the W side of Todoque Mountain (figure 21), and reports indicated that 589 buildings and 21 km of roads had been destroyed by the 2.5 km2 of lava. A seismic swarm on the morning of 27 September was located at about 10 km depth in the same area of the previous seismicity below the vent. In addition, pulses of tremor coincided with pulses of ash emissions. A new flow appeared on the N flank of the cone during the afternoon and partly covered previous flows through the center of Todoque, reaching about 2 km from the coast (figure 22). Ash emissions were more intermittent on 27 and 28 September, drifting SW to 1.5 km altitude and NE to 4.3 km altitude in sporadic pulses associated with lava fountains.

Figure (see Caption) Figure 21. The growth of the lava flow at La Palma during 20-27 September 2021 is shown in different colors. The flow as of 1913 on 20 September is shown in red. The extent of the flow as of 1206 on 25 September is shown in orange. The extent of the flow as of 1158 on 26 September is shown in blue, and the extent of the flow as of 0650 on 27 September is shown in green, nearly reaching Todoque Mountain by early on 27 September 2021. Reports indicated that 589 buildings and 21 km of roads had been destroyed from the 2.5 km2 of lava. Courtesy of Copernicus EMS.
Figure (see Caption) Figure 22. A new flow appeared on the N flank of the cone at La Palma during the afternoon of 27 September 2021 from a reactivated vent; it traveled rapidly downslope reaching the center of Todoque. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

The new flow moved through the upper outskirts of Todoque and had reached the road to El Pampillo on the border of the municipalities of Los Llanos and Tazacorte, about 1 km from the coast, early on 28 September (figure 23). A plume with moderate to high ash concentration rose to 5.2 km altitude and extended up to 25 km W. The altitude of the plume increased to 6.1 km drifting E later in the day. A significant SO2 cloud was clearly identifiable in satellite imagery in a 75 km radius around the island. In addition, satellite instruments measured very large plumes of SO2 drifting hundreds of kilometers E, S, and N over the next several days (figure 24).

Figure (see Caption) Figure 23. The new flow at La Palma moved through the upper outskirts of Todoque on 28 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 24. The TROPOMI instrument on the Sentinel-5P satellite measured very large plumes of SO2 hundreds of kilometers E, S, and N of La Palma during 28, 29, and 30 September 2021. In addition, plumes of SO2 were visible in satellite imagery in a 75 km radius around the island. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during 28-30 September 2021. Effusive activity continued with a sharp decrease in tremor during the day on 28 September. By evening, sustained fountaining was continuing at the N flank vent, while pulsating jets from three vents within the main crater produced strong effusion into both lava flows. The volume of the cone that had formed at the vent was estimated by PEVOLCA to be 10 million m3. Around 2300 local time on 28 September the main lava flow passed on the S side of Todoque Mountain and entered the sea in the area of Playa de Los Guirres in Tazacorte. A continuous cascading flow of lava fell over the cliff (figure 25) and began to form a lava delta. By dawn on 29 September the delta was growing out from the cliff, producing dense steam explosions where the lava entered the sea (figure 26).

Figure (see Caption) Figure 25. A continuous cascade of lava fell over the cliff near El Guirre beach in Tazacorte at La Palma around midnight on 28-29 September 2021. Photo by Angel Medina/EFE, courtesy of RTVE.
Figure (see Caption) Figure 26. By dawn on 29 September 2021 the delta was growing out from the cliff producing dense steam explosions where the lava entered the sea in Tazacorte, La Palma. Image taken from Tijarafe. Photo by Borja Suarez/Reuters, courtesy of RTVE.

By nightfall on 29 September vigorous Strombolian activity was continuing at the pyroclastic cone, and the main lava flow was active all the way to the sea, with a growing delta into the ocean. Ash emissions continued on 29 and 30 September, rising in pulses to 5.2 km altitude and drifting SE, changing to S, SW, and finally NW. Sentinel-2 satellite imagery comparing 25 and 30 September showed the growth of the lava flow during that interval (figure 27). Strombolian and flow activity continued at the fissure vent on 30 September with new surges of activity sending fresh pulses of lava over existing flows (figure 28). The ocean delta continued to grow and reached a thickness of 24 m by the end of 30 September. Mapping of the flow indicated that 870 buildings had been destroyed and the flow covered 3.5 km2 by midday on 30 September (figure 29).

Figure (see Caption) Figure 27. The lava flow at the La Palma eruption traveled downslope to the W between 25 (left) and 30 (right) September 2021. It reached the ocean and began building a delta into the sea late on 28 September. Image uses Atmospheric penetration rendering with bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 28. Fresh pulses of lava flowed over earlier flows at La Palma on 30 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 29. Continued mapping of the lava flow at La Palma indicated that by midday on 30 September 2021 it covered about 3.5 km2 and 870 buildings had been damaged or destroyed. The progress of the flow at different dates is shown in different colors. The status of the flow as of 1913 on 20 September is shown in red. The status as of 1206 on 26 September is shown in green. The status as of 1136 on 29 September is shown in orange, and the status as of 1217 on 30 September is shown in purple. Courtesy of Copernicus EMS.

Late on 30 September 2021 two new vents emerged about 600 m NW of the base of the main cone. They created a new flow about 450 m away from, and parallel to, the main flow that crossed a local highway by the next morning and continued moving W (figure 30). Multiple vents also remained active within and on the flank of the main cone. As of 1 October, the front of the delta was 475 m out from the coastline and 30 m deep. IGN concluded that the volume of material erupted through the end of September was approximately 80 million m3.

Figure (see Caption) Figure 30. Two new vents opened about 600 m NW of the base of the cone late on 30 September 2021. The new flows joined and headed W parallel to the main flow. Drone footage of the new vent was taken on 1 October by the Bristol Flight Lab, courtesy of INVOLCAN.

Geologic Background. The 47-km-long wedge-shaped island of La Palma, the NW-most of the Canary Islands, is composed of two large volcanic centers. The older northern one is cut by the massive steep-walled Caldera Taburiente, one of several massive collapse scarps produced by edifice failure to the SW. The younger Cumbre Vieja, the southern volcano, is one of the most active in the Canaries. The elongated volcano dates back to about 125,000 years ago and is oriented N-S. Eruptions during the past 7,000 years have formed abundant cinder cones and craters along the axis of Cumbre Vieja, producing fissure-fed lava flows that descend steeply to the sea. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas. The southern tip of the island is mantled by a broad lava field emplaced during the 1677-1678 eruption. Lava flows also reached the sea in 1585, 1646, 1712, 1949, and 1971.

Information Contacts: Instituto Geographico Nacional (IGN), C/ General Ibáñez de Íbero 3, 28003 Madrid – España, (URL: https://www.ign.es/web/ign/portal, https://www.ign.es/web/resources/volcanologia/html/CA_noticias.html); Instituto Volcanologico de Canarias (INVOLCAN) (URL: https://www.involcan.org/, https://www.facebook.com/INVOLCAN, Twitter: INVOLCAN, @involcan); Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA), (URL: https://www3.gobiernodecanarias.org/noticias/los-planes-de-evacuacion-del-pevolca-evitan-danos-personales-en-la-erupcion-volcanica-de-la-palma/); NASA 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/); Copernicus EMS (URL: https://emergency.copernicus.eu/, https://twitter.com/CopernicusEMS ); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Cabildo La Palma (URL: https://www.cabildodelapalma.es/es/algunas-de-las-imagenes-de-la-erupcion-volcanica-en-la-palma); El Periodico de Cataluny, S.L.U. (URL: https://www.elperiodico.com/es/fotos/sociedad/erupcion-palma-imagenes-12093812/12103264).Corporación de Radio y Televisión Española (RTVE) (URL: https://rtve.es, https://img2.rtve.es/imagenes/casas-todoque-alcanzadas-lava-este-miercoles-22-septiembre/1632308929494.jpg); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Volcanes de Canarias (URL:https://twitter.com/VolcansCanarias/status/1441711738983002114); Agence France-Presse (AFP) (URL: http://www.afp.com/ ); Bristol Flight Lab, University of Bristol, England (URL: www.https://flight-lab.bristol.ac.uk, https://twitter.com/UOBFlightLab).


Telica (Nicaragua) — September 2021 Citation iconCite this Report

Telica

Nicaragua

12.606°N, 86.84°W; summit elev. 1036 m

All times are local (unless otherwise noted)


Weak explosions and minor ash plumes during April-July 2021

A series of weak ash explosions during 30 November-8 December resulted in ashfall in neighboring communities (BGVN 46:03). The following report describes activity between March and August 2021, based on monthly and special bulletins published by the Instituto Nicaragüense de Estudios Territoriales (INETER) and satellite images.

According to INETER, the volcano was quiet during March through 21 April, when two small gas-and-ash explosions occurred on that date at 0527 and 0610. Ash rose about 400 m above the crater and fell on the volcano’s slopes. Satellite images during the last week of April showed dark emissions.

On 1 May 2021 a Sentinel-2 satellite image showed a weak ash plume extending W over the crater. Weak ash plumes were also recorded by Sentinel-2 on 3 May and 6 May. Then, according to INETER, a total of 60 weak explosions occurred during 6-8 May. The plumes reached a height of 300 m and drifted S and SW, with ash falling primarily on the volcano’s slopes (figure 56). Sentinel-2 images showed weaker dark emissions through the rest of May. INETER reported 19 more weak explosions during 16-17 May and 16 explosions on 22 May, starting at 0508. On 24 May, 15 new explosions occurred, averaging once every 15 minutes. Gas-and-ash columns reached 250 m above the crater, and tephra from the plumes dropped back into the crater. After the activity on 5 May, INETER scientists visited the volcano and observed strong degassing (figure 57).

Figure (see Caption) Figure 56. Webcam image showing an ash explosion at Telica on 7 May 2021. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua, Mayo, 2021).
Figure (see Caption) Figure 57. Degassing from the summit crater of Telica observed during a field visit after gas-and-ash emissions on 5 May 2021. Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua, Mayo, 2021).

According to INETER, on 20-21 June, four small gas and ash explosions occurred. Ash rose to a maximum height of 150 m above the crater and fell on the NW slope. Sentinel-2 images recorded only modest emissions during these explosions, including a dark plume extending S on 25 June (figure 58). INETER reported that on 29 June gas-and-ash emissions began at 0500, with ash reaching a maximum height of about 200 m above the crater and falling on the SW slope.

Figure (see Caption) Figure 58. Ash plume on 25 June 2021, as captured by a Sentinel-2 satellite (natural color, bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

The Washington Volcanic Ash Advisory Center (VAAC) reported ash plumes during 2-3 July. A few discrete emissions and ash near the crater were visible in webcam images on 2 July, and possible diffuse ash near and W of the crater was identified in satellite images. Plumes likely rose to about 200-500 m above the crater. Another steam-and-ash plume drifted SW and then turned N. On 3 July possible ash plumes rose about 500 m above the crater and drifted WSW. Sentinel-2 imagery showed an ash plume within the crater on 20 July. No additional ash plumes were detected or reported through August.

Additional observations. According to INETER, SO2 emissions measured with Mobile-DOAS using 7-8 transects ranged from an average of 47 metric tons/day (April) to 286 metric tons/day (August). The monthly values were generally lower during the first half of 2021 compared to March-December 2020 (figure 59). Seismic activity diminished every month between April (85,198 seismic events) and July (47,762 events), continuing a decreasing trend from January 2021 (about 140,000 seismic events). Most events during April-July were hybrid earthquakes. Tremor was 50-70 RSAM units in March and 10-30 RSAM units during April-July.

Figure (see Caption) Figure 59. Monthly SO2 levels at Telica during March 2020-June 2021. Blue dashed line shows average value (promedios); red dashed line is the standard deviation (desviación estándar). Courtesy of INETER (Boletín mensual Sismos y Volcanes de Nicaragua, Junio, 2021).

Geologic Background. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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).


Yasur (Vanuatu) — September 2021 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Gas-and-ash explosions, SO2 plumes, and thermal anomalies during March-August 2021

Yasur is located at the SE tip of Tanna Island and contains a 400-m-wide summit crater within the small Yenkahe caldera. The current eruption has been ongoing since at least 1774 and has been characterized by Strombolian and Vulcanian activity. More recent activity has consisted of Strombolian activity and gas-and-ash emissions (BGVN 46:04), which continues during this reporting period of March through August 2021. Information primarily comes from monthly bulletins of the Vanuatu Meteorology and Geo-Hazards Department (VMGD) and various satellite data. The Volcano Alert Level remained at a 2 (on a scale of 0-4) during this reporting period.

VMGD reported that seismic data and recent visual observations confirmed ongoing explosions and gas-and-ash emissions during the reporting period. Sulfur dioxide emissions occasionally accompanied those explosions and were measured using the Sentinel-5P/TROPOMI satellite instrument for multiple days each month from March through August (figure 81). The density and drift direction varied.

Figure (see Caption) Figure 81. Occasional SO2 plumes of varying intensities up to 2 DUs (Dobson Units) were observed from Yasur throughout March-August 2021. Plumes drifted generally W on 16 March (top left), SW on 13 April (top right), and 16 June (bottom left), and above the volcano on 18 August (bottom right) 2021. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Intermittent thermal anomalies recorded by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system during March through August were of moderate intensity, though brief periods of low activity were observed during April and late June to early July (figure 82). A total of twelve thermal alerts were detected by the MODVOLC thermal algorithm on 1 (1) and 28 (2) March, 11 April (1), 26 May (1), 3 (1) and 11 (1) June, 28 (1) and 30 (1) July, and 10 (1) and 15 (2) August. On clear weather days, as many as three thermal anomalies at the summit crater (occupying both the N and S vents) were also seen in Sentinel-2 infrared satellite images (figure 83).

Figure (see Caption) Figure 82. MIROVA (Log Radiative Power) thermal data for Yasur during March-August 2021 showed consistent low- to moderate- thermal activity, with brief periods of rest and declining strength during April and late June to early July. Courtesy of MIROVA.
Figure (see Caption) Figure 83. Sentinel-2 infrared satellite images showing thermal anomalies (yellow-orange) of differing intensities in the N and S vents of the summit crater at Yasur on 16 March (top left), 15 May (top right), 9 June (bottom left), and 8 August (bottom right) 2021. During 16 March, 15 May, and 9 June, the two thermal anomalies in the crater were roughly the same intensity. By 8 August, the intensity of the anomaly in both vents had decreased slightly. Occasional gas-and-steam emissions accompanied the thermal activity. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA 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).


Ibu (Indonesia) — September 2021 Citation iconCite this Report

Ibu

Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

All times are local (unless otherwise noted)


Intermittent low-level ash plumes, light ashfall, and thermal anomalies during January-August 2021

Ibu is located along the NW coast of Halmahera Island in Indonesia and contains an inner crater measuring 1-km-wide and 400 m deep, an outer crater that measures 1.2-km-wide, and is breached on the N side. The first observed and recorded eruption occurred in 1911 and consisted of a small explosion in the summit crater. The current eruption period began in April 2008 and has recently been characterized by daily ash emissions, explosions, and thermal anomalies (BGVN 46:01). This report covers similar activity of white-and-gray emissions, ash plumes, and light ashfall during January through August 2021 using information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellite data. The Volcano Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Activity throughout January-August 2021 was consistent and similar to that of the previous year. Between 35 and 115 daily explosions were detected during the reporting period, the latter of which occurred on 7 February, and produced white-and-gray emissions that rose 200-1,000 m above the crater and drifted in different directions, according to PVMBG. Occasional larger explosions were reported in VONA and VAAC notices. According to the MIROVA plot (Log Radiative Power), thermal activity was consistent, yet low in power from January through August; during May, the anomalies were at their lowest strength (figure 31). The MODVOLC algorithm detected ten thermal alerts during this period, with one each on 1 February, 9 March, 22 April, 2 and 27 June, 29 July, and 12 August, and three on 23 August 2021. Some of this thermal activity was detected in Sentinel-2 infrared satellite images on clear weather days (figure 32).

Figure (see Caption) Figure 31. Constant low-power thermal anomalies were detected at the summit crater of Ibu during January through August 2021, as shown by the MIROVA graph (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 32. Thermal anomalies persisted in the summit crater of Ibu during January through August 2021. One strong central anomaly was commonly accompanied by a smaller one slightly to the NW, as shown on 10 January (top left), 1 March (top right), 5 April (middle left), and 8 August (bottom right) 2021. Images using “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

The Darwin VAAC detected a single minor ash plume on 7 January that rose to 1.8 km altitude, or about 500 m above the summit, and drifted N, based on a ground report. This information was also reported in a PVMBG VONA notice that stated the ash plume occurred at 1055. Similar low-level ash plumes persisted in February; during 5-6 February ash plumes rose to 1.8-2.4 km and drifted W and SW, based on HIMAWARI-8 satellite imagery. An ash plume rose 800 m above the crater on 8 February on 1101, according to a VONA notice. PVMBG reported that during 16-17 February a total of 88 eruptive events occurred. Consecutive ash plumes on 24, 25, and 26 February rose 500, 800, and 800 m above the crater, respectively (figure 33).

Figure (see Caption) Figure 33. An ash plume rose from the summit of Ibu on 25 February 2021 to a height of 800 m. Courtesy of MAGMA Indonesia.

Similar intermittent ash emissions continued during March and April. On 3, 9, and 12 March an ash plume rose to 2.1 km and drifted S, according to Darwin VAAC notices (figure 34). During 14, 21, 25, and 31 March ash plumes rose 600-1,000 m above the crater, based on VONA notices and PVMBG daily reports. A thermal anomaly was detected in satellite imagery near the summit on 22 March and 6-7 April, according to a Darwin VAAC report. Accompanying the latter thermal anomaly, at 1812 a VONA notice reported an ash plume rose 400 m above the crater. An ash plume rose 800 m above the crater on 20 April at 1819 and another detected on 22 April at 1258 rose 1,000 m above the crater. On 26 April an ash plume rose 600 m above the crater and drifted N.

Figure (see Caption) Figure 34. Intermittent ash plumes rising above the summit of Ibu were recorded multiple times in webcam images during March and April 2021, as shown here on 3 March 2021 rising to 2.1 km altitude and drifting S. Courtesy of MAGMA Indonesia.

During May and June, activity remained consistent with intermittent ash emissions. On 3 and 12 May an ash plume rose to 1.8 km altitude and drifted W and NW, based on HIMAWARI-8 satellite imagery. Ash plumes were visible during 16 (figure 35) and 17 May, the latter of which occurred at 1039 and rose ~750 m above the crater and drifted N. During the afternoon and evening of 19 May, light ashfall was reported in residential areas from the Naga village (4.8 km SW) to the Tongute village of Ternate (10 km W). On 6 and 10 June ash emissions rose to 1.8 km altitude and extended N. Rock avalanches were recorded through seismic data during 11-13 June, though they were not visually confirmed, according to PVMBG. During 18-20 June 63 eruptive events per day were detected.

Figure (see Caption) Figure 35. Ash plumes from the summit of Ibu continued during May and June 2021, as seen here on 16 May 2021. Courtesy of MAGMA Indonesia.

Low ash emissions continued during July and August; on 10 July at 0719 an ash plume rose 800 m above the crater and the next day, light ashfall was reported in residential areas to the W of the volcano, though it was not specified how far. During 14-15 and 17 July white-and-gray emissions rose 200-800 m above the crater and drifted N, S, and W; light ashfall was again observed in residential areas to the W, and loud rumblings were heard as far as the Ibu observation post. On 28 July an ash plume rose to 2.4 km altitude and extended NE. During 1-2 August an ash plume rose to 1.8-2.1 km altitude. An ash plume on 18 August was reported at 0810 rising 800 m above the crater and drifting W. An ash plume on 22 August rose to 1.8 km altitude and was accompanied by a thermal anomaly that was identified in satellite imagery.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

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.esdm.go.id/v1); 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).


Suwanosejima (Japan) — September 2021 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Intermittent explosions send incandescent ejecta 1 km from summit during January-June 2020

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian explosions, and ashfall. Ongoing activity since October 2004 has included explosions which generate incandescent ejecta and ash plumes that rise hundreds of meters above the summit to altitudes between 1 and 3 km. Incandescence is often observed at night and ejecta periodically reaches as far as a kilometer from the summit. Ashfall is usually noted several times each month in the nearby community on the SW flank of the island. Ongoing activity for January-June 2021 is covered in this report with information provided by the Japan Meteorological Agency (JMA), the Tokyo Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.

Intermittent pulses of explosive activity continued during January-June 2020. Ashfall was reported a few times each month in the village 4 km SW of the summit. Vibrations were felt there during the stronger explosive events, and summit incandescence was frequently observed with the surveillance camera located in the town. Most of the daily multiple explosions reached 1.2-1.8 km altitude and drifted in multiple directions, but several times each month ash emissions reached 2 km altitude or higher. Twice in March and once in June incandescent ejecta reached almost one kilometer from the summit crater, prompting JMA to raise the alert level. The MIROVA Log Radiative Power graph of the MODIS thermal anomaly data through June 2021 indicates intermittent pulses of increased thermal activity in late December 2020, March, and April 2021 that appear to correspond to increased periods of explosive activity (figure 58).

Figure (see Caption) Figure 58. The MIROVA Log Radiative Power graph of the MODIS thermal anomaly data from 28 October 2020 through June 2021 indicates intermittent pulses of increased thermal activity in late December 2020, March 2021, and April 2021 that appear to correspond to increased periods of explosive activity. Courtesy of MIROVA.

After a pulse of explosive activity at the end of December 2020, there was a decrease in activity during January 2021. This fact, along with no significant changes in the crustal movement data, led JMA to reduce the Alert Level from 3 (Mountain-entry restrictions) to 2 (Crater-area restrictions) on 14 January. No ejecta had traveled more than 1 km from the crater since late December. Only seven explosions were recorded during January compared with 460 in December 2020. Ash emissions rose up to 2,500 m above the crater rim, and ejecta traveled 400 m from the crater edge. During an overflight on 19 January JMA confirmed gray and white emissions at the summit and noted no particular changes to the crater since the previous observation on 28 December 2020. Numerous small explosions reported by the Tokyo VAAC rose to 1.2-1.8 km altitude and drifted in multiple directions, often S or SE, on most days during the month. During 15-16 January ash plumes rose to 2.0-2.4 km altitude and drifted NE. The highest plumes in January were reported on 20 and 21 January when they rose to 2.4 km and drifted W and E (figure 59).

Figure (see Caption) Figure 59. Ash emissions at Suwanosejima rose 2.5 km above the summit, according to JMA, on 20 January 2021 (left). The next day, incandescent ejecta traveled 400 m NE of the crater during explosive activity (right). Courtesy of JMA (Volcanic activity commentary for Suwanosejima, January 2021).

Seven explosions were also recorded during February 2021; they produced ash plumes that rose 1,800 m above the crater rim, and scattered ejecta up to 500 m from the Mitake crater. Ashfall and vibrations were reported several times in the nearby village, and incandescence was sometimes visible at night. From 2-9 February the Tokyo VAAC reported intermittent ash emissions on most days that rose to 1.2-1.8 km altitude and drifted S or SE. On 13 February an ash plume rose to 2.1 km altitude and drifted W. Ash emissions appeared in Sentinel-2 satellite imagery drifting E on 20 February (figure 60). The Tokyo VAAC reported the emissions at 1.2-1.5 km altitude. During 23-26 February ash emissions were reported at 1.5-1.8 km altitude drifting S, SW, NW, and SE.

Figure (see Caption) Figure 60. Ash emissions were captured drifting E in Sentinel-2 satellite imagery at Suwanosejima on 20 February 2021. Image uses Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Two periods of increased explosive activity occurred during 2-7 and 30-31 March 2021; the number of explosions increased to 212 from the seven recorded during February. The Tokyo VAAC reported explosions with ash emissions that rose to 1.2-1.5 km altitude and drifted S and W during 1-5 March. Early on 6 March ejecta was thrown 900 m SE from the crater, followed by additional explosions that sent ejecta 400 m (figure 61). Ash plumes rose to 1.8-2.1 km altitude during 6-9 March. An ash emission reached 1,500 m above the crater (2.3 km altitude) on 15 March and an ash plume on 17 March reached 2.4 km altitude and drifted NE. Between 18 March and the end of the month the explosions sent plumes to 1.2-2.1 km altitude in multiple directions. A distinct thermal anomaly was recorded inside the summit crater on 27 March in Sentinel-2 satellite imagery (figure 62), likely from multiple explosions of incandescent ejecta. Large blocks of ejecta traveled up to 1 km multiple times during 30-31 March, resulting in JMA raising the Alert Level from 2 to 3 (on a scale of 1-5). In addition, ash emissions rose 800 m high with the explosions. During an overflight on 31 March JMA noted ash emissions (figure 63) and multiple high temperatures areas around the crater interpreted to be from incandescent ejecta. Vibrations were felt in the nearby village on both 6 and 31 March, and ashfall was reported several times.

Figure (see Caption) Figure 61. Incandescent ejecta and ash emissions increased significantly during March 2021 at Suwanosejima. Ejecta was thrown 900 m SE from the summit on 6 March; note the bright spot to the left of summit. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, March 2021).
Figure (see Caption) Figure 62. A bright thermal anomaly and ash plume drifting NW were recorded in Sentinel-2 satellite imagery at Suwanosejima on 27 March 2021. Image uses Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 63. Gray ash emissions were visible at the Mitake Crater of Suwanosejima during an overflight by JMA on 31 March 2021; view is from the SSE flank. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, March 2021).

A decrease in activity in early April 2021 led JMA to reduce the Alert Level from 3 to 2 on 5 April; 64 explosions were reported for the month. Incandescent ejecta reached 600 m from the crater. Ashfall was occasionally reported at the village 4 km away, and summit incandescence was occasionally observed from there as well. The Tokyo VAAC reported explosions on 1 and 2 April, and then multiple explosions daily during 6-12 April with ash plumes that rose to 1.5-2.7 km altitude and drifted SW and W. Multiple daily explosions continued during 19-21 and 23-30 April, with most plumes rising to 1.5-1.8 km altitude and drifting W or SW. Emissions reached 2.4 km altitude on 28 April and drifted NE and N. A very small thermal anomaly inside the summit crater was recorded in Sentinel-2 imagery on 21 April.

One hundred explosions were reported by JMA during May 2021. Incandescent ejecta reached 700 m from the crater rim on 6 May. Ashfall was recorded and vibrations were felt a number of times in the village 4 km SSW along with occasional incandescence visible at the summit crater with the surveillance camera located in the village. Higher altitude ash plumes were observed in May than during previous months; plumes reached heights over 2 km above the summit crater at least 13 times. The highest plume, on 30 May, reached 2.6 km above the summit (3.4 km altitude). The Tokyo VAAC reported multiple explosions almost every day of the month; on several days more than five explosions occurred. While the ash plumes often rose to 1.2-1.8 km altitude, they were significantly higher a number of times. During 2-3 May they rose to 2.4-3.0 km altitude and drifted SE and S. During 5-7 and 9-13 May they rose over 2 km each day. On 17 May a pilot reported ash 185 km SSW at 3.7 km altitude. Additional explosions that rose to over 2 km altitude occurred on 21-23 and 26-31 May. Plumes rose to 3.0-3.4 km altitude on 30 May and ten explosions were recorded the next day rising to 1.2-2.4 km altitude. One of them was recorded in Sentinel-2 satellite imagery (figure 64).

Figure (see Caption) Figure 64. A dense ash emission drifted W from Suwanosejima on 31 May 2021 as seen in Sentinel-2 satellite imagery with Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Ash emissions during June 2021 rose as high as 2,400 m above the crater; there were 157 explosions reported. Larger explosions on 21 and 23 June resulted in incandescent ejecta being thrown about 900 m NW and SE from the crater (figure 65). This prompted JMA to raise the Alert Level on 23 June from 2 to 3. The Japan Meteorological Agency Mobile Survey Team (JMA-MOT) conducted an aerial observation that day and confirmed that a part of the floor of the Mitake crater was still incandescent (figure 66); in addition, thermal anomalies were measured from scattered ejecta around the crater. The Tokyo VAAC reported multiple daily explosions and ash plumes throughout the month, most of which rose to 1.2-2.1 km altitude and drifted in various directions. Nine explosions were recorded on 1 June with plumes that rose as high as 2.4 km altitude and drifted W. Reports of plumes visible at 3.0 km altitude were noted on 1 and 2 June. During 4-9 June the multiple daily explosions rose to 1.2-2.1 km altitude drifting SE and NE; they were higher on 8 June, rising to 2.4-3.0 km altitude and drifting NW. Explosions on 14 June rose to 2.4 km altitude, and on 23 June ten explosions were recorded; two of them reached 3.0 km altitude and drifted SW. For the remainder of June, most days included explosions over 2 km altitude.

Figure (see Caption) Figure 65. Large blocks of incandescent ejecta were sent about 900 m NW and SW from the Mitake crater at Suwanosejima on 21 June 2021. Note the bright spots both to the left and right of the summit. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, June 2021).
Figure (see Caption) Figure 66. An aerial observation flight by JMA on 23 June 2021 at Suwanosejima confirmed the presence of incandescent ejecta inside the summit crater. Courtesy of JMA (Volcanic activity commentary for Suwanosejima, June 2021).

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

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground);


Kadovar (Papua New Guinea) — September 2021 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Intermittent ash plumes and thermal anomalies during January-August 2021

Kadovar, located in the Bismark Sea offshore from the island of New Guinea about 25 km NNE from the mouth of the Sepik River, has been erupting since January 2018 with intermittent ash and gas-and-steam plumes along with weak summit thermal anomalies (BGVN 46:01). Similar activity continued during this reporting period of January through August 2021 based on information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite data.

Relatively low activity during this reporting period consisted of primarily weak thermal anomalies in the summit crater and small gas-and-ash emissions (figure 59). On 3 and 7 January discrete ash puffs seen in HIMAWARI-8 satellite images rose to 1.5 km altitude and drifted SW and W, respectively; both dissipated within six hours. Ash plumes on 5 and 6 January rose to 1.8 km altitude and drifted NW. Occasional ash plumes were detected during March, rising to 1.5 km altitude and drifting W, based on satellite imagery. On 15 April an ash plume that rose to 1.8 km altitude and drifted W was accompanied by a small sulfur dioxide plume, according to the TROPOMI instrument on the Sentinel-5P satellite (figure 60). On 12 and 19 June, 4 July, and 1, 19, and 27 August small ash plumes that rose to 1.2-1.5 km altitude drifted W and NW.

Figure (see Caption) Figure 59. Sentinel-2 satellite images showing intermittent gas-and-steam plumes rising from Kadovar and drifting downwind on 10 March (top left), 29 April (top right), 13 June (bottom left), and 23 July (bottom right) 2021. Images with “Natural color” (bands 4, 3, 2) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 60. Small sulfur dioxide emissions were detected at Kadovar on 7 (left) and 15 (right) April 2021 with the TROPOMI instrument on the Sentinel-5P satellite, accompanying small ash plumes. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows weak clusters of thermal anomalies during January through March and May through August 2021 (figure 61). Stronger anomalies were detected during July through August, which was also reflected in Sentinel-2 infrared satellite imagery (figure 62).

Figure (see Caption) Figure 61. Occasional thermal anomalies (red dots) were detected at the summit of Kadovar during January through August 2021, as recorded by the Sentinel-2 MODIS Thermal Volcanic Activity data (bands 12, 11, 8A). A higher concentration of strong anomalies was detected during May and July-August. Courtesy of MIROVA.
Figure (see Caption) Figure 62. Sentinel-2 infrared satellite images showing a weak thermal anomaly in the summit crater of Kadovar on 28 February (top left), 29 May (top right), 29 July (bottom left), and 27 August (bottom right), accompanied by white gas-and-steam emissions that drifted generally SE and W. A significant thermal anomaly was noted on 27 August. Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

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/); 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).


Bezymianny (Russia) — September 2021 Citation iconCite this Report

Bezymianny

Russia

55.972°N, 160.595°E; summit elev. 2882 m

All times are local (unless otherwise noted)


Frequent gas-and-steam emissions and a weak thermal anomaly during March-August 2021

Bezymianny, part of the Klyuchevskoy volcano group on the Kamchatka Peninsula, has had frequent eruptions dating back to 1955. The current eruptive period began in May 2010 and has recently consisted of lava dome growth, strong fumarolic activity, and thermal anomalies (BGVN 46:03). This report covers similar low activity of white gas-and-steam emissions and a persistent, weak thermal anomaly at the summit crater during March through August 2021 using weekly and daily reports from the Kamchatka Volcano Eruptions Response Team (KVERT) and satellite data.

Activity at Bezymianny was relatively low during the reporting period, mostly consisting of frequent moderate gas-and-steam emissions (figure 44) and a weak thermal anomaly over the lava dome in the summit crater. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system based on the analysis of MODIS data showed intermittent low-power thermal anomalies during late March through August (figure 45). These low-power anomalies were also detected in the summit crater, occasionally accompanied by white gas-and-steam emissions on clear weather days, based on Sentinel-2 infrared satellite images (figure 46).

Figure (see Caption) Figure 44. Photo of Bezymianny showing strong fumarolic activity on 30 March 2021. Photo by A. Gerasimov, IVS FEB RAS. Courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 45. Intermittent low-power thermal anomalies at Bezymianny were detected by the MIROVA system (Log Radiative Power) during late March through August 2021. Courtesy of MIROVA.
Figure (see Caption) Figure 46. Sentinel-2 infrared satellite images of a weak thermal anomaly (dark orange) over the lava dome at Bezymianny’s summit crater on 2 May (left) and 15 August (right) 2021. The thermal anomaly is occasionally accompanied by white gas-and-steam emissions. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

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/); 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).


Bagana (Papua New Guinea) — September 2021 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies continue and a possible lava flow during March 2021

Bagana, located in central Bougainville Island in Papua New Guinea, is a remote volcano that has had historical eruptions dating back to 1842. The current eruption period began in February 2000 and has more recently consisted of ongoing thermal anomalies, possible lava flows, and gas-and-steam emissions (BGVN 46:01). This report updates information from January through August 2021 and describes continuing thermal anomalies, lava flows, ash emissions, and sulfur dioxide emissions using information from the Darwin Volcanic Ash Advisory Center (VAAC) and various satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent low-power thermal anomalies during January through August (figure 46). During late February the power of the thermal anomalies gradually increased and remained high during most of March due to possible lava flows that were present near the summit crater. This activity gradually decreased in power during April and remained low until early June, though these anomalies were still lower in power compared to those in March. The intensity of the thermal anomalies gradually increased throughout August. According to the MODVOLC thermal algorithm, a total of eight thermal alerts were detected near the summit area on 9 March (2), 11 March (1), 13 March (1), 16 March (1), 30 March (1), 1 April (1), and 6 June (1) 2021. These thermal alerts, as well as those that were higher in power according to the MIROVA graph, were detected by Sentinel-2 infrared satellite imagery, though cloud cover often prevented a clear view of the summit (figure 47). A strong anomaly was initially detected on 26 February in the summit crater, and by 13 March incandescent material was visible the N flank. Thermal activity suggesting a lava flow extended down the N flank on 23 March. Distinct sulfur dioxide plumes accompanied the stronger thermal anomalies, based on data from the TROPOMI instrument on the Sentinel-5P satellite (figure 48).

Figure (see Caption) Figure 46. Intermittent low- to moderate- thermal anomalies detected at Bagana during January through August 2021 as recorded by the MIROVA system (Log Radiative Power). During late February the power of the anomalies gradually increased and remained high during March due to the incandescent material detected near the summit crater. In April the anomalies decreased again in power and remained low until another brief increase occurred in early June and late August. Courtesy of MIROVA.
Figure (see Caption) Figure 47. Sentinel-2 infrared satellite images showing a persistent thermal anomaly in the summit crater of Bagana on 26 February (top left), 13 March (top right), 23 March (bottom left), and 6 June (bottom right) 2021. On 13 March incandescent material was visible on the N flank, which by 23 March appeared to be a lava flow. Sentinel-2 images with "Atmospheric penetration" (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 48. Distinct sulfur dioxide plumes were detected from Bagana on 19 March (top left), 22 May (top right), 26 July (bottom left), and 17 August (bottom right) 2021. Some of these plumes exceeded 2 Dobson Units (DUs) and drifted in different directions. Data is from the TROPOMI instrument on the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Ash emissions reported by the Darwin VAAC on 10 March rose to 2.4 km altitude and drifted NW, based on HIMAWARI-8 satellite images. On 14 June the ash plume rose to 2.1 km altitude and drifted W. Another ash plume on 9 July rose to 1.8 km altitude and drifted W. A Darwin VAAC report issued on 31 July described an ash plume that rose to a maximum altitude of 4.6 km and drifted W, followed by gas-and-steam emissions; however, this was not clearly visible due to the weather.

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/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA 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).


Etna (Italy) — August 2021 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3320 m

All times are local (unless otherwise noted)


Strombolian explosions, ash plumes, lava fountaining, and flows during April-July 2021

Etna, located on the island of Sicily, Italy, has documented records of historical eruptions dating back to 1500 BCE. Activity has frequently originated from its summit areas, which include 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). Another crater, referred to as the "cono della sella" (saddle cone), developed during early 2017 between SEC and NSEC. Its most recent eruptive period began in September 2013 and more recently has been characterized by Strombolian explosions, ash plumes, lava fountaining, and flows (BGVN 46:04). This report updates activity from April through July 2021, covering similar eruptive events, based on weekly and special reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV) and satellite data.

Summary of activity during April-July 2021. Volcanism was relatively low at Etna during April and mid-May, primarily characterized by Strombolian explosions and white gas-and-steam emissions. Beginning on 19 May 2021, activity intensified and remained high through July. Intra-crater Strombolian explosions varied in intensity and frequency dominantly in the Southeast Crater (SEC), accompanied by ash plumes that rose to a maximum altitude of 10 km, resulting in ashfall in nearby communities, lava flows primarily on the SW flank, and lava fountains that rose up to 1 km above the summit. Occasional isolated ash emissions were observed above the Northeast Crater (NEC) while degassing primarily characterized the Bocca Nuova Crater (BN) and the Voragine Crater (VOR).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows strong and frequent thermal anomalies during a majority of the reporting period; during April through mid-May there was a notable decline in the intensity of the anomalies, which was followed by a significant strong pulse, representing the lava flows in June and July (figure 340). This stronger thermal activity was also reflected in data from the MODVOLC thermal algorithm, a total of 183 alerts were detected in the summit crater during April through July; thermal anomalies were reported for four days in April, nine days in May, sixteen days in June, and twelve days in July. Additionally, the lava flows were clearly visible in Sentinel-2 infrared satellite imagery during June and July descending the SW and SE flanks from SEC (figure 341). Frequent Strombolian activity contributed to distinct sulfur dioxide plumes that exceeded two Dobson Units (DUs) that drifted generally S and E (figure 342).

Figure (see Caption) Figure 340. Strong and frequent thermal anomalies at Etna were detected during April through July 2021, as reflected in the MIROVA data (Log Radiative Power). Briefly during April and mid-May, the intensity of the thermal anomalies markedly decreased before renewed lava flows resulted in significantly high anomalies. Courtesy of MIROVA.
Figure (see Caption) Figure 341. Sentinel-2 infrared satellite imagery showing the strong lava flows mainly descending the SW and SE flanks of Etna during June-July 2021, frequently accompanied by white gas-and-steam emissions and thermal anomalies in the northern summit craters. The lava flows shown are all originating from the Southeast Crater (SEC). Lava descended the SW flank on 13 June (top left), 18 June (top right), 23 June (middle left), 26 June (middle right), 3 July (bottom left), and 8 July (bottom right) 2021, getting progressively cooler through July. Flows were visible on the SE flank on 23 June and 26 June. Images using “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 342. Sulfur dioxide plumes exceeding 2 Dobson Units (DUs) from Etna were detected by the TROPOMI instrument on the Sentinel-5P satellite on 1 April drifting S (top left), 26 May drifting E (top right), 27 June drifting E (bottom left), and 20 July drifting NE and SE (bottom right) 2021. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during April 2021. During April, INGV reported intra-crater Strombolian explosions in NEC, BN, and SEC. On 1 April around 0100 the SEC explosions transitioned into lava fountaining, generating an ash plume at 0940 that rose to 9 km altitude and drifted SSW. At 0200 a lava flow was reported in the eastern edge of SEC, moving toward the upper part of the VOR-BN complex (Valle del Bove) over the older flows that appeared during March 2021. By 1000 the fountaining had stopped, though explosions continued, producing ash plumes that rose to 5.5-9 km altitude and drifted S and SSW. As a result, ashfall was reported in Milia, Nicolosi, and Catania, and lapilli up to 1 cm was reported in Rifugio Sapienza. A second lava flow appeared at 1040, originating from the same eastern vent and migrating toward VOR-BN. Explosivity gradually declined around 1320 in SEC; by 2300 the lava flows had begun to cool and explosions were no longer observed in the summit crater. During the rest of the month volcanism was relatively low, though intra-crater Strombolian explosions continued in NEC and BN; degassing was prominent in SEC, VOR-BN, and NEC craters. Explosions would eject material tens of meters above the crater rim in NEC, accompanied by some ash emissions. At VOR-BN, an overflight on 13 April noted that activity was focused in the western vents, ejecting reddish ash emissions. An explosion in the eastern vent in SEC at 0030 on 25 April ejected incandescent material 350 m above the crater rim; an ash plume was visible drifting S.

Activity during May 2021. Activity during the first half of May remained similar to the previous month, with degassing at the summit craters and weak, intermittent Strombolian explosions occurring at the eastern vents in SEC, accompanied by ash emissions (figure 343). During the second week of May, INGV reported isolated ash emissions from NEC. On 19 May at 0221 the Strombolian activity in SEC intensified, accompanied by ash emissions, which evolved into lava fountaining by 0234 (figure 344). At the same time, a lava flow was observed traveling down the SW flank, reaching an elevation of 2.8 km. This event lasted three and a half hours, after which the fountains and explosions stopped abruptly. The lava flow was 1.8 km long, 1.5 m thick, and had a volume of 450,000 m3. On 22 May at 0134 Strombolian explosions continued in SEC, generating ash plumes that drifted SE. By 0302 the explosions evolved into lava fountains that ejected material to the NE. A second lava flow developed on the SW flank, overlapping the one from the 19th, advancing to 3 km elevation. It was 1 km long, 1.5 m thick, and had a volume of 150,000 m3. A third lava flow was observed on the E flank was 0.5 km long, 1.5 m thick, and a volume of 70,000 m3. At 0454 the lava fountain and explosive activity had stopped abruptly.

Figure (see Caption) Figure 343. Map of the summit craters at Etna showing the active vents during early May 2021. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. The hatch marks indicate the crater rims: BN = Bocca Nuova; VOR = Voragine; NEC = North East Crater; SEC = South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity. Yellow circles indicate steam and/or gas emissions only; degassing was the dominant activity at the summit craters during April through mid-May. A single vent in the eastern part of SEC was explosive. Courtesy of INGV (Report 19/2021, ETNA, Bollettino Settimanale, 03/05/2021 – 09/05/2021, data emissione 11/05/2021).
Figure (see Caption) Figure 344. Thermal images of the intense lava fountaining activity at Etna on 19 May (left) and 22 May (right) 2021 taken with the EMOT thermal camera. Courtesy of INGV (Report 21/2021, ETNA, Bollettino Settimanale, 17/05/2021 – 23/05/2021, data emissione 25/05/2021).

On 24 May explosions were accompanied by a lava flow on the SW flank that descended to 900 m elevation, was 1.5 m thick, and had an erupted volume of 150,000 m3. The most intense phase of the explosions occurred during 2235 and 2345; activity ended around 0010. On 25 May an ash plume rose to 4 km altitude and drifted ENE at 1020; by 1820 explosive activity resumed. Two eruptive episodes on 26 May with peaks at 0350 and 1300 resulted in fine ashfall in Milo (10 km E). The next day, explosions intensified in SEC at 1450 while tephra fell in Giarre (17 km ESE), Milo, and Fornazzo (10 km ESE), though inclement weather prevents visual observations. On 28 May three explosive events were detected beginning at 0830, reaching a maximum intensity at 0900, and ending at 0930. As a result, ashfall was reported in Giarre. A second explosive episode occurred during 1740 and 1815 and a third, more intense explosive episode occurred during 2115-2350. On 30 May explosions beginning at 0545 lasted for two hours and resulted in fine ashfall in Petrulli (12 km SE).

Activity during June 2021. Variable Strombolian activity persisted during June, mainly in SEC; minor and diffuse ash emissions occurred at BN and ash emissions were reported on 4 June in NEC. Degassing was reported in BN and VOR. Weak Strombolian activity in SEC began at 0850 on 2 June, producing minor and diffuse ash plumes, which intensified around 1000 and transitioned to lava fountains that lasted more than two hours (figure 345). The lava fountains generated ash plumes that rose to 5-6 km altitude and drifted E, resulting in ashfall N of Zafferana, near Petrulli and Santa Venerina (figure 345). A lava flow was observed on the S flank of SEC that traveled SW. Fountains stopped at 1245. During the night and early morning of 3-4 June weak intra-crater explosions continued. On 4 June activity increased at 1530 and was characterized by discontinuous ash emissions and a lava flow descending the S flank of SEC. Lava fountains began at 1820 and generated an ash plume that rose to 6.5 km altitude and drifted SE. Ejecta was deposited in Aci Castello, Aciterzza, San Giovanni, La Punta, Tremestieri, Catania, Viagrande, and between Pedara, Fleri, and Siracusa. By 1930 the fountaining had stopped; webcam images showed that by 2300 the lava flow remained active at an elevation of 2.8 km and was a thickness of 2 m.

Figure (see Caption) Figure 345. Webcam and thermal images of the dense ash plumes rising from SEC summit crater at Etna on 1 June (top left), 2 June (top right and bottom left), and 4 June (bottom right) 2021 taken with the EMOV webcam and EMOT thermal camera. Courtesy of INGV (Report 23/2021, ETNA, Bollettino Settimanale, 31/05/2021 – 06/06/2021, data emissione 08/06/2021).

On 9 June at 0110 intra-crater Strombolian activity was reported in the saddle cone, accompanied by discontinuous ash emissions, which continued through 11 June. Coarse material was ejected tens of meters from the edge of SEC, falling back into the crater. The lava flow descending the SW flank on 12 June reached an elevation of 2.7 km and was 1.7 km long, 1.5 m thick, and had a volume of 700,000 m3. At 2130 explosions transitioned into lava fountains that rose 400-500 m above the crater and produced an ash plume that rose to 5.5 km altitude and drifted SSE. Ashfall was reported in Sapienza, Refuge, Nicolosi, Tremestieri, Belpasso, and Catania. The fountains ended at 2350, alongside a cooling flow on the SW flank, though Strombolian explosions continued in SEC.

Several lava fountaining episodes were reported during 1332-1450 on 16 June, 2220 on 18 June to 0210 on 19 June, 2040-2215 on 19 June, 1131 on 20 June to 0214 on 21 June, overnight during 21-22 June, and during the early hours of 22 and 23 June. Each episode began with Strombolian explosions, followed by fountaining and crater overflows descending the SW and SE flanks toward the Valle del Bove (S) on 16 June while those on 21 June traveled 1 km SW toward Monte Frumento Supino, stopping at 2.9 km elevation (figure 341). Ash plumes rose as high as 8 km altitude, causing ashfall the S and SSE. INGV reported nine lava fountain episodes at SEC occurred during 21-27 June; explosive activity was concentrated in the W part of SEC at three of the four saddle vents, though some weak, isolated explosions were detected in the E vents (figure 346). The episodes generated ash plumes rising 5-10 km altitude while lava flows descended the SW and SE flanks (figure 346). An effusive vent was detected on the SE flank of SEC on 23 June. The lava fountaining events have caused SEC cone to grow significantly.

Figure (see Caption) Figure 346. Webcam images of the incandescent lava fountains and gray ash plumes rising from Etna during 21-27 June 2021. Lava flows could be seen on the flanks of the volcano on 21 June (top left), 23 June (top right and middle left), and 25 June (middle right and bottom left) 2021. All photos were taken by Tremestieri on the S flank 20 km from SEC. Courtesy of INGV (Report 26/2021, ETNA, Bollettino Settimanale, 21/06/2021 – 27/06/2021, data emissione 29/06/2021).

Activity during July 2021. Strombolian activity, lava fountains, and ash plumes from SEC continued in July, in addition to occasional gas-and-ash emissions in NEC and BN. Three episodes of lava fountains generated ash plumes that rose 5-10 km altitude, resulting in ashfall to the E and SE. The first episode occurred at SEC at 0040 on 2 July, beginning with Strombolian explosions. Resulting ash plumes drifted ESE and within an hour, lava fountains were visible, accompanied by lava flows moving SW; fountaining had stopped at 0250. The second episode began at 1656 on 4 July, producing fountains at 1725 and ash plumes, ending by 1900 (figure 347). Lava flows traveled SW and ENE while the ash plumes drifted ESE. The last episode occurred at 2330 on 6 July; ash plumes rose to 5 km altitude and drifted SE; ash deposits were observed on the S flank. Explosions intensified at 0000 on 7 July with fountaining occurring thirty minutes later, rising as high as 1 km. A small lava flow originated from the S side of the cone and traveled SW, reaching an elevation of 2.8 km.

Figure (see Caption) Figure 347. Webcam image of an ash plume from Etna on 4 July 2021 taken from the EMOV (Montagnola) camera. Courtesy of INGV (Report 30/2021, ETNA, Bollettino Settimanale, 19/07/2021 – 25/07/2021, data emissione 27/07/2021).

During fieldwork on 7 July scientists observed bombs up to 1 m in diameter on the N side of Mount Barbagallo, while smaller bombs were observed farther away. Lapilli was reported in the S part of Tremestieri, and ash was deposited in Nicolosi, as well as other communities downwind. This episode lasted about two hours. A second episode that began at 2100 on 8 July consisted of Strombolian activity and lava fountains. Ash plumes rose to 3.4 km altitude and drifted SE, resulting in ashfall and the front of the lava flow reached 2.4 km elevation. On 14 July explosions generated an ash plume that rose to 9 km altitude and drifted NE, which resulted in 1-cm-thick lapilli and ash deposits in the Rocca Campana district, as well as in the Rifugio, Citelli, and Presa, with ashfall in Taormina and the S part of Calabria. Another lava flow on the S flank of SEC was moving SW and had begun to cool by 15 July.

On 20 July at 0150 explosions in SEC generated ash emissions that drifted SSE; at 0650 the intensity of these explosions increased and eventually evolved into lava fountains at 0920. At the same time, a lava flow along the side of the SW flank of SEC was reported, as well as deposits of material on the S and E flanks of the volcano. Two lava flows moving SW were detected on the N flank of SEC, stopping at an elevation of 2.9 km. An ash plume drifted E and resulted in ashfall on the E flank and in Zafferana, Milo, and Fornazzo. On 26 July INGV reported continuous ash emissions at NEC that rose to 6 km altitude and drifted N. Strombolian activity intensified again at 0925 on 28 July in SEC, generating discontinuous ash emissions (figure 348); this episode stopped by 2318. Explosions in SEC began again at 1915 on 31 July, producing ash plumes that rose to 5 km altitude and drifted SE, resulting in ashfall in Fornazzo and Milo. At 2115 a lava flow down the SW flank reached 2.8 km elevation.

Figure (see Caption) Figure 348. Webcam images of the Strombolian explosions in the SEC on 28 July 2021 (top left) and the lava fountain activity on 31 July (top right) taken from surveillance cameras in Monte Cagliato and Bronte. Ashfall was observed in Fornazzo (bottom left) and Milo (bottom right). Courtesy of INGV (Report 31/2021, ETNA, Bollettino Settimanale, 26/07/2021 – 01/08/2021, data emissione 03/08/2021).

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/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA 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).

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Bulletin of the Global Volcanism Network - Volume 46, Number 10 (October 2021)

Managing Editor: Edward Venzke

Erta Ale (Ethiopia)

Episodes of strong thermal signals from lava lakes during March and May 2021

La Palma (Spain)

First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows



Erta Ale (Ethiopia) — October 2021 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Episodes of strong thermal signals from lava lakes during March and May 2021

Erta Ale, Ethiopia’s most active volcano in one of the most desolate regions on Earth contains two active craters with lava lakes (North Pit and South Pit) in the summit caldera. Since February 2020, volcanism has been relatively low, except for a brief surge of thermal activity at the end of November 2020 (BGVN 45:05, 45:10, 46:02). This report summarizes activity during March-August 2021 and is based on satellite data.

During the reporting period, thermal anomalies based on MODIS satellite instruments analyzed using the MODVOLC algorithm, recorded frequent thermal alerts during 19-31 March, including ten days of hotspots with up to 4 pixels (figure 104). The March hotspots were the first since 30 November 2020. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system recorded a heavy concentration of strong thermal anomalies during the second half of March and a smaller pulse (less radiative power and fewer anomalies) of activity during the second half of May, with a few scattered hotspots during other months (figure 105).

Figure (see Caption) Figure 104. Location of thermal anomalies at Erta Ale in March 2021 detected by MODIS satellite instruments. Courtesy of HIGP MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 105. Log radiative power time-series plot of thermal anomalies from Erta Ale for the year ending 4 August 2021, as recorded by the MIROVA system. A strong pulse of activity during the second half of March is evident, along with a smaller (weaker and less frequent) group of anomalies in the second half of May; a single anomaly was detected on 26-27 July 2021. Courtesy of MIROVA.

Sentinel-2 infrared images also showed thermal anomalies suggestive of lava lakes present in both N and S crater pits during March through July 2021 (figure 106). A weak thermal signal can be seen on both 4 and 9 March from the S pit, which was much stronger on 19 March. Only five days later, on 24 March, a much strong thermal signal appeared in the N crater. Additional strong thermal anomalies at the N pit were detected on 29 March, 23 April, and 18 May. The S pit showed a strong thermal anomaly on 27 July. Small weaker anomalies were frequently present at one or both craters through August 2021.

Figure (see Caption) Figure 106. Sentinel-2 thermal satellite images of Erta Ale during 9 March to 27 July 2021 showing thermal anomalies in both N and S pit craters of the summit caldera. Top left: Faint thermal anomaly in the S pit crater on 9 March. Top right: Strong thermal anomaly in the S pit crater on 19 March. Center left: Strong thermal anomaly in the N pit crater and weak anomaly in the S pit on 24 March. Center right: Weak thermal anomaly in the S pit crater on 13 May. Bottom left: Strong thermal anomaly in the N rater on 18 May. Bottom right: Strong thermal anomaly in the S crater on 27 July. Sentinel-2 images with “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground. 

Geologic Background. The Erta Ale basaltic shield volcano is the most active in Ethiopia, with a 50-km-wide edifice that rises more than 600 m from below sea level in the barren Danakil depression. It is the namesake and most prominent feature of the Erta Ale Range. The volcano includes a 0.7 x 1.6 km elliptical summit crater hosting 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 usually also holds at least one long-term lava lake that has 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/).


La Palma (Spain) — October 2021 Citation iconCite this Report

La Palma

Spain

28.57°N, 17.83°W; summit elev. 2426 m

All times are local (unless otherwise noted)


First eruption since 1971 starts on 19 September; lava fountains, ash plumes, and lava flows

Multiple eruptions have occurred during the last 7,000 years at the Cumbra Vieja volcanic center on La Palma, the NW-most of the Canary Islands. The eruptions have created cinder cones and craters, and produced fissure-fed lava flows that reached the sea a number of times. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas, most recently at the southern tip of the island in 1971. During the three-week eruption in October-November 1971, eruptive activity created a new cone, Teneguia, that had as many as six active vents (CSLP 90-71), and blocky lava flows that reached the sea on the SW flank.

A new eruption began at La Palma on 19 September 2021 in an area on the SW flank of the island about 20 km NW of the 1971 eruption, after a multi-year period of elevated seismicity. Two fissures opened and multiple vents produced lava fountains, ash plumes, and flows that traveled over 5 km W to the sea, destroying hundreds of properties in their path (figure 2). Activity through the end of September is covered in this report with information provided by Spain’s Instituto Geographico Nacional (IGN), the Instituto Volcanologico de Canarias (INVOLCAN), the Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA), maps from Copernicus EMS, satellite data, and news and social media reports.

Figure (see Caption) Figure 2. A 3D-rendering of the extent of lava flows from the Cumbra Vieja eruption on La Palma as of 15 October 2021 is shown in red with flows from earlier eruptions shown in tan. Data provided by Copernicus EMS and IGN, courtesy of INVOLCAN.

Precursor seismicity. In early July 2017 IGN enhanced their Volcanic Surveillance Network at La Palma to include four GPS antennas, five seismic stations, and four hydrochemical groundwater control points. A seismic swarm of 68 events located on the southern third of the island was recorded during 7-9 October 2017. It was the first of a series of seismic swarms recorded during 2017-2021 (table 1) located in the same general area. This first swarm was followed by a similar set of events a few days later during 13-14 October. The magnitudes of the events during October 2017 (given as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude) ranged from less than 1.5 to 2.7, and they occurred over a depth range of 12-35 km. The next seismic swarm of similar characteristics occurred during February 2018, followed by a smaller swarm of seven microseismic events recorded in the same area one year later, on 12 February 2019.

Table 1. Precursor seismicity episodes at La Palma between October 2017 and late June 2021 were all located in the southern third of the island. Magnitude is reported by IGN as MbLg, or the magnitude from the amplitude of the Lg phase, similar to the local Richter magnitude. Data courtesy of IGN Noticias.

Date Detected Events Located Events Magnitude Range (mbLg) Depth Range (km)
07-09 Oct 2017 -- 68 Less than 1.5-2.7 12-35
13-14 Oct 2017 352 44 Less than 1.5-2.1 15-22
10-14 Feb 2018 -- 85 1.8-2.6 25-30
12 Feb 2019 -- 7 0.7-1.1 15
24 Jul-02 Aug 2020 682 160 1.2-2.5 16-39
23-26 Dec 2020 602 126 1.3-2.3 30
31 Jan 2021 -- 27 1.2-2.5 10-29
25 Jun 2021 80 12 Less than 2.2 18-34

By the time the next seismic swarm began in July 2020, IGN had a network of 13 seismic stations installed around the island. There were 160 located events that occurred during 24 July-2 August 2020 with magnitudes of 1.2-2.5 and depths of 16-39 km. Reprocessing of the previous data indicated a distribution of seismicity for the three series (October 2017, February 2018, and July 2020) in a wide strip in an east-west direction, although the October 2017 series occurred at a shallower depth and with the epicenters more concentrated. IGN noted similarities between the February 2018 and July-August 2020 events in terms of location and magnitude (figure 3). Another very similar swarm of 602 detected events was recorded during 23-26 December 2020, with most events located on the western slope of Cumbre Vieja. Two swarms on 21 January and 25 June 2021 had fewer events but similar depths and magnitudes to the earlier events.

Figure (see Caption) Figure 3. Comparison of seismic event depth and locations at La Palma from swarms during 2017, 2018, and 24 July-2 August 2020. Courtesy of IGN (06-08-2020 16:45 UTC, Final de la actividad en La Palma).

Renewed seismicity began on 11 September 2021. The number, frequency, and magnitude of the events all increased over the next several days, while the depth of the events grew shallower. On 13 September a multi-agency scientific committee raised the Alert Level to Yellow (the second lowest level on a four-color scale) for the municipalities of El Paso, Los Llanos de Aridane, Mazo, and Fuencaliente de la Palma. IGN noted a migration of the seismicity toward the W side of the island on 14 September (figure 4). The accumulated surface deformation between 12 and 14 September measured 1.5 cm from the island GNSS network. Seismic activity on 15 September continued to migrate slightly NW at depths of around 7-9 km; in addition, 20 shallow earthquakes of 1-3 km depth were recorded. The accumulated deformation had reached 6 cm by 15 September. As of 0930 on 16 September 50 shallow earthquakes between 1-5 km depth had been located and the maximum vertical deformation was around 10 cm in the area of the seismicity. During 16-18 September seismic activity decreased, but a 3.2 magnitude earthquake located at 100 m depth was felt by the local population. Intense surface seismicity (between 0-6 km) increased in the early hours of 19 September and numerous earthquakes were felt by the local population (figure 4). The maximum accumulated deformation increased to 15 cm in the area close to the seismicity by 1100 on 19 September, and the eruption began about five hours later.

Figure (see Caption) Figure 4. Seismic events at La Palma during 12-19 September 2021 showed distinct changes during those days. During 12-14 September (left) the seismicity migrated westward and was located at depths of about 7-13 km. The color scale on the left indicates the time of the events in hours before 0925 on 14 September, with red as the most recent. An abrupt increase in shallow seismicity on 19 September 2021 occurred a few hours before the eruption began, as shown by the bright orange dots in the right image. The color bar on the right represents the dates of the seismic events beginning on 11 September. Courtesy of IGN (left: 14-09-2021 09:30 UTC, right: 19-09-2021 11:00 UTC, Actualización de la información sobre la actividad volcánica en el sur de la isla de La Palma).

Eruption begins 19 September 2021. A fissure eruption began at 1510 local time (1410 UTC) on 19 September after the intense seismic and deformation activity that began on 11 September. Observers near the eruption site in the area of Cabeza de Vaca, in the municipality of El Paso, witnessed a large explosion with ejecta that produced a gas-and-ash plume. Strombolian activity was accompanied by phreatomagmatic pulses along two 100-m-long N-S fissures about 200 m apart. INVOLCAN scientists observed seven vents along the fissures during the initial stage of the eruption (figure 5). Multiple tall lava fountains fed flows downslope to the W, igniting fires. The PEVOLCA steering committee briefly raised the Alert Level to Orange, and then to Red by 1700 for high-risk municipalities directly affected by the eruption. About 5,500 people evacuated with no injuries reported, and authorities recommended that residents stay at least 2 km from the vents. INVOLCAN scientists determined an average flow rate of 700 m/hour and lava temperatures of around 1,075°C at the start of the eruption (figure 6).

Figure (see Caption) Figure 5. INVOLCAN scientists observed seven active vents along the fissure at the start of the La Palma eruption at Cumbre Vieja on 19 September 2021. Photo by Alba, courtesy of INVOLCAN.
Figure (see Caption) Figure 6. INVOLCAN scientists determined a flow rate for the new lava flows at La Palma on 19 September 2021 of 700 m/hour and a temperature of 1,075°C. Courtesy of INVOLCAN.

The Toulouse VAAC issued the first ash advisory for the La Palma eruption about 90 minutes after it began. They reported ongoing lava fountains and an ash plume to about 1 km altitude. The plume drifted SW at less than 1.5 km altitude, while SO2 emissions were reported drifting ESE at 3 km altitude. Later that day, they noted continuing intense lava fountains and ashfall in the vicinity of the volcano. The next day ash emissions drifted S at 2.4 km altitude. Sulfur dioxide emissions were measured by satellite instruments beginning on 19 September; they increased dramatically and drifted hundreds of kilometers E and SE toward the NE coast of Africa over the next few days (figure 7). Ongoing ash emissions rose to 4.6 km altitude later on 20 September. The first Sentinel-2 satellite images of the eruption appeared on 20 September showing a strong point source thermal anomaly partly covered by meteoric clouds (figure 8).

Figure (see Caption) Figure 7. Sulfur dioxide emissions from the Cumbre Vieja eruption at La Palma were measured by the TROPOMI Instrument on the Sentinel-5P satellite beginning on 19 September 2021 (left); they increased dramatically over the next several days. The plume was detected by satellite over 400 km SE over the western Sahara on the NW coast of Africa by 20 September. The plume was reported as visible at Gomera Island (80 km SE) on 21 September, having increased significantly in area and mass from the previous day. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 8. Sentinel-2 satellite images of La Palma show a sharp contrast from a cloudless sky before any signs of surface activity on 10 September 2021 (left) to dense cloud cover on the lower slopes of La Palma with a strong thermal anomaly from the new fissure vent and flows with rising steam plumes drifting NE on 20 September (right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

The first map of the new flow on 20 September produced by IGN in partnership with Copernicus Emergency Management Service (EMS) showed that the main channel of the lava flow had traveled more than 3 km W. The flows had covered about 1 km2 and destroyed an estimated 166 buildings (figure 9). A report of the PEVOLCA Scientific Committee indicated that activity on 20 and 21 September was concentrated at four main vents that produced parallel flows with an average flow rate of 200 m/hour; the maximum flow thickness was 10-12 m (figure 10). Strong lava fountaining continued both days and ash fell in the vicinity of the vents. By 0814 on 21 September an updated Copernicus EMS map showed that 350 homes had been covered by lava and the flow field had expanded to 1.54 km2. A few hundred more residents evacuated as lava advanced towards Tacande; bringing the number of evacuees to about 5,700. One lava flow branch was advancing slowly S at a rate of 2 m/hour. An ash cloud was observed later that day on the W flank of the volcano slowly drifting SW at 2.4 km altitude. Sulfur dioxide emissions were present over the SE part of the island and were visible at Gomera Island, 80 km SE. Late in the day, ash was observed in satellite imagery about 50 km W of the volcano, while intense lava fountaining continued at the source vent (figure 11).

Figure (see Caption) Figure 9. The first map of the new lava flow at La Palma on 20 September 2021 was produced by the Copernicus Emergency Management Service (EMS) in partnership with IGN. It showed that the main channel of the lava flow shown in red had traveled more than 3 km W covering about 1 km2 and had destroyed an estimated 166 buildings. Courtesy of Copernicus EMS.
Figure (see Caption) Figure 10. INVOLCAN scientists collected lava fragments from the Cumbre Vieja flow front at La Palma on 21 September 2021. The average flow thickness was 10-12 m. Courtesy of INVOLCAN.
Figure (see Caption) Figure 11. Intense fountaining continued at the vent of the Cumbre Vieja eruption on La Palma during the night of 21 September 2021; multiple small flows descended the flanks of the growing pyroclastic cone. Courtesy of Cabildo La Palma.

Activity during 22-25 September 2021. Ash emissions during 22 and 23 September drifted SW and S from 0-3 km altitude, and NE and E from 3-5 km altitude (figure 12); ashfall up to 3 cm thick was reported downwind. An SO2 plume was also noted drifting NE in satellite imagery. PEVOLCA reported on 23 September that two relatively slow-moving lava flows continued to advance downslope from the vent (figure 13). The northernmost flow was moving at 1 m/hour and was 12 m high and 500 m wide in some places. The southern flow, which surrounded Montaña Rajada, was moving at 4-5 m/hour and about 10 m high. The overall flow was 3.8 km long and 2.1 km from the coast (figure 14). By late on 23 September reports indicated 420 structures had been destroyed and the flow covered just under 2 km2.

Figure (see Caption) Figure 12. Ash emissions rose as high as 4.6 km altitude on 22 September 2021 at La Palma. Up to 3 cm of ashfall was reported downwind. Courtesy of El Periodico de Cataluny, S.L.U.
Figure (see Caption) Figure 13. Slow moving lava flows at La Palma continued downslope from the vents on 22 and 23 September 2021. Many businesses and homes in the community of Todoque, shown here, were destroyed by the lava flows on 22 September. Photo by Bomberos de Canarias, courtesy of RTVE.
Figure (see Caption) Figure 14 The original flow at La Palma as of 1913 on 20 September is shown in red. The progression of the lava flows each day from 20-23 September 2021 is shown in different colors. Lava flows covered almost 2 km2 of La Palma by the end of the day on 23 September 2021, and reports indicated 420 structures and 15.2 km of roads had been destroyed. The flow was about 3.8 km long and still 2.1 km from the coast. Courtesy of Copernicus EMS.

Lava fountains rose hundreds of meters above the summit crater of the new cone early on 24 September 2021 (figure 15). IGN reported an increase in explosive activity on 24 September that was accompanied by a sharp increase in tremor amplitude. This was followed a short while later by the opening of two new vents on the NW flank of the cone; the fast-moving flows merged into one and produced a new flow over top of the earlier flows. Part of the upper section of the S flank of the cone collapsed on 24 September and briefly caused flow speeds to increase to 250-300 m/hour overnight before slowing to an average speed of 40 m/hour. Due to the fast-moving flow, an evacuation order was issued in the early afternoon for Tajuya, Tacande de Abajo, and part of Tacande de Arriba, affecting 300-400 people. Three airlines also suspended flights to La Palma. The Toulouse VAAC reported ash plumes throughout the day. Ash plumes drifted SW below 3 km altitude and E and SE at 3-5.2 km altitude and resulted in significant ashfall in numerous locations by the next morning (figure 16). Pilots also reported ash near Tenerife and over La Gomera.

Figure (see Caption) Figure 15. Lava fountains several hundred meters high rose from the growing pyroclastic cone at La Palma in the early hours of 24 September 2021, seen from Tajuya. Dense ash emissions continued throughout the day. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 16. Ashfall in El Paso on La Palma covered cars and flowers on the morning of 25 September 2021. Ash emissions produced ashfall in numerous places around the island over the next several days. Courtesy of Volcanes de Canarias.

By 25 September there were three active vents in the crater and one on the flank of the cone (figure 17), and two active lava flows. On 25 and 26 September dense ash emissions (figure 18) closed the airport and produced ashfall not only in the municipalities near the eruption, but also on the eastern slope of the island; it was reported in Villa de Mazo, Breña Alta and Breña Baja, and Santa Cruz de La Palma or Puntallana. Plumes were drifting SW at altitudes below 1.5 km and NE between 1.5 and 3.9 km altitude over a large area. Mapping by Copernicus EMS indicated that the ashfall covered an area of 13 km2 (figure 19).

Figure (see Caption) Figure 17. A new vent opened on the lower W flank of the pyroclastic cone at La Palma on 25 September 2021. Courtesy of INVOLCAN.
Figure (see Caption) Figure 18. Dense ash emissions on 25 September 2021 at La Palma forced closure of the island’s airport. Photo by Desiree Martin, AFT, courtesy of Corporación de Radio y Televisión Española (RTVE).
Figure (see Caption) Figure 19. A large area of La Palma, shown in blue, was affected by ashfall to the W and SW of the erupting vent on 25 September 2021. The extent of the lava flow as of 1913 UTC on 20 September is shown in red, and the extent of the flow by 1206 on 25 September is shown in orange. Courtesy of Copernicus EMS.

Activity during 26-28 September 2021. During the evening of 26 September jets of lava up to 1 km high were visible from La Laguna and some explosions were strong enough to be felt within 5 km of the vent (figure 20). The main, more northerly lava flow overtook the center of Todoque, in the municipality of Los llanos de Aridane, which had been evacuated several days earlier. It crossed the highway (LP-213) in the center of town and continued 150 m W. It was initially moving at about 100 m/hour, was 4-6 m high, and the front was about 600 m wide, but it slowed significantly after crossing through Todoque, and the height grew to 15 m; it was located about 1,600 m from the coast. The more southerly flow continued moving at about 30 m/hour and was about 2.5 km long.

Figure (see Caption) Figure 20. Jets of lava rose to nearly 1,000 m high at La Palma as seen from La Laguna on the evening of 26 September 2021. The lava flow remained active on the NW flank of the cone. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

The PEVOLCA Scientific Committee determined that the volume of erupted material from the beginning of the eruption on 19 September until 27 September was about 46.3 m3. By early on 27 September the front of the flow was close to the W side of Todoque Mountain (figure 21), and reports indicated that 589 buildings and 21 km of roads had been destroyed by the 2.5 km2 of lava. A seismic swarm on the morning of 27 September was located at about 10 km depth in the same area of the previous seismicity below the vent. In addition, pulses of tremor coincided with pulses of ash emissions. A new flow appeared on the N flank of the cone during the afternoon and partly covered previous flows through the center of Todoque, reaching about 2 km from the coast (figure 22). Ash emissions were more intermittent on 27 and 28 September, drifting SW to 1.5 km altitude and NE to 4.3 km altitude in sporadic pulses associated with lava fountains.

Figure (see Caption) Figure 21. The growth of the lava flow at La Palma during 20-27 September 2021 is shown in different colors. The flow as of 1913 on 20 September is shown in red. The extent of the flow as of 1206 on 25 September is shown in orange. The extent of the flow as of 1158 on 26 September is shown in blue, and the extent of the flow as of 0650 on 27 September is shown in green, nearly reaching Todoque Mountain by early on 27 September 2021. Reports indicated that 589 buildings and 21 km of roads had been destroyed from the 2.5 km2 of lava. Courtesy of Copernicus EMS.
Figure (see Caption) Figure 22. A new flow appeared on the N flank of the cone at La Palma during the afternoon of 27 September 2021 from a reactivated vent; it traveled rapidly downslope reaching the center of Todoque. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.

The new flow moved through the upper outskirts of Todoque and had reached the road to El Pampillo on the border of the municipalities of Los Llanos and Tazacorte, about 1 km from the coast, early on 28 September (figure 23). A plume with moderate to high ash concentration rose to 5.2 km altitude and extended up to 25 km W. The altitude of the plume increased to 6.1 km drifting E later in the day. A significant SO2 cloud was clearly identifiable in satellite imagery in a 75 km radius around the island. In addition, satellite instruments measured very large plumes of SO2 drifting hundreds of kilometers E, S, and N over the next several days (figure 24).

Figure (see Caption) Figure 23. The new flow at La Palma moved through the upper outskirts of Todoque on 28 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 24. The TROPOMI instrument on the Sentinel-5P satellite measured very large plumes of SO2 hundreds of kilometers E, S, and N of La Palma during 28, 29, and 30 September 2021. In addition, plumes of SO2 were visible in satellite imagery in a 75 km radius around the island. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during 28-30 September 2021. Effusive activity continued with a sharp decrease in tremor during the day on 28 September. By evening, sustained fountaining was continuing at the N flank vent, while pulsating jets from three vents within the main crater produced strong effusion into both lava flows. The volume of the cone that had formed at the vent was estimated by PEVOLCA to be 10 million m3. Around 2300 local time on 28 September the main lava flow passed on the S side of Todoque Mountain and entered the sea in the area of Playa de Los Guirres in Tazacorte. A continuous cascading flow of lava fell over the cliff (figure 25) and began to form a lava delta. By dawn on 29 September the delta was growing out from the cliff, producing dense steam explosions where the lava entered the sea (figure 26).

Figure (see Caption) Figure 25. A continuous cascade of lava fell over the cliff near El Guirre beach in Tazacorte at La Palma around midnight on 28-29 September 2021. Photo by Angel Medina/EFE, courtesy of RTVE.
Figure (see Caption) Figure 26. By dawn on 29 September 2021 the delta was growing out from the cliff producing dense steam explosions where the lava entered the sea in Tazacorte, La Palma. Image taken from Tijarafe. Photo by Borja Suarez/Reuters, courtesy of RTVE.

By nightfall on 29 September vigorous Strombolian activity was continuing at the pyroclastic cone, and the main lava flow was active all the way to the sea, with a growing delta into the ocean. Ash emissions continued on 29 and 30 September, rising in pulses to 5.2 km altitude and drifting SE, changing to S, SW, and finally NW. Sentinel-2 satellite imagery comparing 25 and 30 September showed the growth of the lava flow during that interval (figure 27). Strombolian and flow activity continued at the fissure vent on 30 September with new surges of activity sending fresh pulses of lava over existing flows (figure 28). The ocean delta continued to grow and reached a thickness of 24 m by the end of 30 September. Mapping of the flow indicated that 870 buildings had been destroyed and the flow covered 3.5 km2 by midday on 30 September (figure 29).

Figure (see Caption) Figure 27. The lava flow at the La Palma eruption traveled downslope to the W between 25 (left) and 30 (right) September 2021. It reached the ocean and began building a delta into the sea late on 28 September. Image uses Atmospheric penetration rendering with bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 28. Fresh pulses of lava flowed over earlier flows at La Palma on 30 September 2021. Photo by Tom Pfeiffer, courtesy of Volcano Discovery.
Figure (see Caption) Figure 29. Continued mapping of the lava flow at La Palma indicated that by midday on 30 September 2021 it covered about 3.5 km2 and 870 buildings had been damaged or destroyed. The progress of the flow at different dates is shown in different colors. The status of the flow as of 1913 on 20 September is shown in red. The status as of 1206 on 26 September is shown in green. The status as of 1136 on 29 September is shown in orange, and the status as of 1217 on 30 September is shown in purple. Courtesy of Copernicus EMS.

Late on 30 September 2021 two new vents emerged about 600 m NW of the base of the main cone. They created a new flow about 450 m away from, and parallel to, the main flow that crossed a local highway by the next morning and continued moving W (figure 30). Multiple vents also remained active within and on the flank of the main cone. As of 1 October, the front of the delta was 475 m out from the coastline and 30 m deep. IGN concluded that the volume of material erupted through the end of September was approximately 80 million m3.

Figure (see Caption) Figure 30. Two new vents opened about 600 m NW of the base of the cone late on 30 September 2021. The new flows joined and headed W parallel to the main flow. Drone footage of the new vent was taken on 1 October by the Bristol Flight Lab, courtesy of INVOLCAN.

Geologic Background. The 47-km-long wedge-shaped island of La Palma, the NW-most of the Canary Islands, is composed of two large volcanic centers. The older northern one is cut by the massive steep-walled Caldera Taburiente, one of several massive collapse scarps produced by edifice failure to the SW. The younger Cumbre Vieja, the southern volcano, is one of the most active in the Canaries. The elongated volcano dates back to about 125,000 years ago and is oriented N-S. Eruptions during the past 7,000 years have formed abundant cinder cones and craters along the axis of Cumbre Vieja, producing fissure-fed lava flows that descend steeply to the sea. Eruptions recorded since the 15th century have produced mild explosive activity and lava flows that damaged populated areas. The southern tip of the island is mantled by a broad lava field emplaced during the 1677-1678 eruption. Lava flows also reached the sea in 1585, 1646, 1712, 1949, and 1971.

Information Contacts: Instituto Geographico Nacional (IGN), C/ General Ibáñez de Íbero 3, 28003 Madrid – España, (URL: https://www.ign.es/web/ign/portal, https://www.ign.es/web/resources/volcanologia/html/CA_noticias.html); Instituto Volcanologico de Canarias (INVOLCAN) (URL: https://www.involcan.org/, https://www.facebook.com/INVOLCAN, Twitter: INVOLCAN, @involcan); Steering Committee of the Special Plan for Civil Protection and Attention to Emergencies due to Volcanic Risk (PEVOLCA), (URL: https://www3.gobiernodecanarias.org/noticias/los-planes-de-evacuacion-del-pevolca-evitan-danos-personales-en-la-erupcion-volcanica-de-la-palma/); NASA 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/); Copernicus EMS (URL: https://emergency.copernicus.eu/, https://twitter.com/CopernicusEMS ); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Cabildo La Palma (URL: https://www.cabildodelapalma.es/es/algunas-de-las-imagenes-de-la-erupcion-volcanica-en-la-palma); El Periodico de Cataluny, S.L.U. (URL: https://www.elperiodico.com/es/fotos/sociedad/erupcion-palma-imagenes-12093812/12103264).Corporación de Radio y Televisión Española (RTVE) (URL: https://rtve.es, https://img2.rtve.es/imagenes/casas-todoque-alcanzadas-lava-este-miercoles-22-septiembre/1632308929494.jpg); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Volcanes de Canarias (URL:https://twitter.com/VolcansCanarias/status/1441711738983002114); Agence France-Presse (AFP) (URL: http://www.afp.com/ ); Bristol Flight Lab, University of Bristol, England (URL: www.https://flight-lab.bristol.ac.uk, https://twitter.com/UOBFlightLab).

Atmospheric Effects

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

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc Reports

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

Additional Reports  False Reports