Smithsonian / USGS Weekly Volcanic Activity Report 15-21 September 2021

Rachel Holsteen-Bruyere <rbruyere@xxxxxxx> · Wed, 22 Sep 2021 12:55:09 -0700

2-2-2-2-2-2-2-2-2-2-2-2-2

From: "Kuhn, Sally" <KUHNS@xxxxxx>

Smithsonian / USGS Weekly Volcanic Activity Report
15-21 September 2021

Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx<mailto:kuhns@xxxxxx
>)
URL:
https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDkTmWq7g$

New Activity/Unrest: La Palma, Spain  | Semisopochnoi, Aleutian Islands
(USA)

The Weekly Volcanic Activity Report is a cooperative project between the
Smithsonian's Global Volcanism Program and the US Geological Survey's
Volcano Hazards Program. Updated by 2300 UTC every Wednesday, these reports
are preliminary and subject to change as events are studied in more detail.
This is not a comprehensive list of all of Earth's volcanoes erupting
during the week, but rather a summary of activity at volcanoes that meet
criteria discussed in detail in the "Criteria and Disclaimers" section.
Carefully reviewed, detailed reports about recent activity are published in
issues of the Bulletin of the Global Volcanism Network.

Note that many news agencies do not archive the articles they post on the
Internet, and therefore the links to some sources may not be active. To
obtain information about the cited articles that are no longer available on
the Internet contact the source.

New Activity/Unrest

La Palma  | Spain  | 28.57Â°N, 17.83Â°W  | Summit elev. 2426 m

An eruption began at La Palma after about a week of intensifying seismicity
that showed hypocenters becoming shallower and moving NW, and significant
related inflation. During 17-18 September the PEVOLCA (Plan de Emergencias
VolcÃ¡nicas de Canarias) steering committee (comprised of representatives
from multiple agencies, local authorities, and institutions) reviewed
mitigation, evacuation, and emergency plans. Helicopter and drone
overflights were conducted in areas thought to be at risk from an eruption.
IGN reported that during 17-18 September seismicity decreased, though an M
2 felt by local residents was located at 100 m depth, and vertical
deformation occurred near the earthquake epicenters.

IGN noted that seismicity intensified during the morning of 19 September,
with earthquakes located at 0-6 km depth; a M 4.2 event was recorded at
1116 and vertical deformation increased. Authorities evacuated about 50
residents with reduced mobility and their companions from Las Manchas de
Abajo, Jedey, San NicolÃ¡s and El ParaÃso (El Paso and Los Llanos de
Aridane), El Charco (Fuencaliente), La Bombilla (Los Llanos de Aridane and
Tazacorte), and El Remo and Puerto Naos (Los Llanos de Aridane). Residents
in an area prone to landslides were also evacuated. Other preparations
continued at the hospital, in neighborhoods, and at evacuation centers.

At 1510 on 19 September an eruption began in the area of Cabeza de Vaca, in
the municipality of El Paso. Observers near the eruption site observed a
large explosion that ejected material and produced a gas-and-ash plume;
volcanic tremor was recorded by the seismic network. Two 200-m-long
fissures aligned N-S opened about 200 m apart. INVOLCAN scientists observed
seven vents along the fissures during the initial stage of the eruption.
Multiple tall lava fountains fed flows downslope to the W, igniting forest
fires. Photos and video posted by IGN showed multiple pulsating fountains
fanning out from parts of the fissure. Ash plumes rose about 1.5 km and gas
plumes rose 3 km and drifted ESE. The PEVOLCA steering committee briefly
raised the Alert Level to Orange, and then to Red (the highest level on a
four-color scale) 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.
The La Palma airport briefly closed, livestock were evacuated, and
education centers were closed along with sections of multiple highways.
Later that day INVOLCAN scientists who measured an area of the flows
determined an average flow rate of 700 m per hour and temperatures around
1,075 degrees Celsius. By the next day a main cone had formed.

The sulfur dioxide gas emission rate was 6,000-11,500 tons per day during
19-20 September. Satellite data showed a plume of sulfur dioxide drifting
475 km SE and reaching the coastline of Africa by 20 September. A map
produced on 20 September by IGN in partnership with Copernicus Emergency
Management Service (EMS) showed that the main part of the lava flow had
traveled more than 3 km W and another branch extended about 1.5 km WSW. The
flows had covered about 1 square kilometer and destroyed an estimated 166
buildings. A news article noted that activity was concentrated at four main
vents, the last (and ninth) of which opened at 1956 on 20 September about
900 m from the main vents. Strong lava fountaining continued during 20-21
September and ash fell in the vicinity of the vents. Ash plumes rose
2.4-4.6 km (8,000-15,000 ft) a.s.l. and drifted as far as 55 km SW and S
according to the Toulouse VAAC. Sulfur dioxide gas plumes drifted W and E
at an altitude of 3 km (10,000 ft) a.s.l. 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 square kilometers. According to a
news report lava up to 12 m thick was advancing at a rate of 200 m per
hour. A few hundred more residents evacuated as lava advanced towards
Tacande; bringing the number of evacuees to about 5,700. The S lava branch
was advancing slowly, at a rate of 2 m per hour. Later that day INVOLCAN
stated that increased volcanic tremor amplitude reflected greater intensity
of Strombolian explosions at the vents.

Geologic Summary. 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.

Sources: Instituto GeogrÃ¡fico Nacional (IGN)
https://urldefense.com/v3/__https://www.ign.es/web/ign/portal__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDaJYqFnk$
 ;
Instituto VolcanolÃ³gico de Canarias (INVOLCAN)
https://urldefense.com/v3/__http://www.involcan.org/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD8cOGJuk$
 ;
Toulouse Volcanic Ash Advisory Centre (VAAC)
https://urldefense.com/v3/__http://www.meteo.fr/vaac/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDWBUfL3s$
 ;
Gobierno de Canaries
https://urldefense.com/v3/__https://www3.gobiernodecanarias.org/noticias/el-comite-director-del-pevolca-analiza-los-avances-en-los-planes-de-evacuacion-de-la-poblacion-afectada-en-la-palma/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD_bnhctc$
 ;
Gobierno de Canarias
https://urldefense.com/v3/__https://www3.gobiernodecanarias.org/noticias/el-hospital-de-la-palma-reorganiza-su-actividad-para-garantizar-la-atencion-sanitaria-ante-la-erupcion-volcanica/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDcelbEAQ$
 ;
Gobierno de Canarias
https://urldefense.com/v3/__https://www3.gobiernodecanarias.org/noticias/los-planes-de-evacuacion-del-pevolca-evitan-danos-personales-en-la-erupcion-volcanica-de-la-palma/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD3vcvvOI$
 ;
Advanced geospatial Data Management Platform (ADAM)
https://urldefense.com/v3/__https://adamplatform.eu/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD-dC4Z-U$
 ;
Cabildo de La Palma
https://urldefense.com/v3/__https://www.cabildodelapalma.es/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDCFMWpPs$
 ;
CartografÃa Digital
https://urldefense.com/v3/__https://www.cartografiadigital.es/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDe-H1YfU$
 ;
1-1-2 Canarias
https://urldefense.com/v3/__http://www.112canarias.com/web/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDTnnV_1E$
 ;
Aviation24.be
https://urldefense.com/v3/__https://www.aviation24.be/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDJm_Knfw$
 ;
El PeriÃ³dico
https://urldefense.com/v3/__https://www.elperiodico.com/es/sociedad/20210919/erupcion-volcan-lapalma-12093616__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDV5IprQk$
 ;
rtvc Ente PÃºblico Radio TelevisiÃ³n Canaria
https://urldefense.com/v3/__https://rtvc.es/el-volcan-engulle-casi-200-viviendas-en-su-avance-hacia-la-costa/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDv369b_4$
 ;
NOTICIAS 8 ISLAS
https://urldefense.com/v3/__https://noticias8islas.com/750-efectivos-trabajan-pevolca-seguridad-la-palma-ayuntamientos/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDpy-6ZAM$

Semisopochnoi  | Aleutian Islands (USA)  | 51.93Â°N, 179.58Â°E  | Summit
elev. 1221 m

AVO reported that eruptive activity at Semisopochnoi's North Cerberus
crater continued during 15-21 September. Weather clouds obscured views of
the volcano on most days. Several small daily explosions were recorded by
local seismic stations; ash plumes were not visible in satellite images
suggesting that they remained below 3 km (10,000 ft) a.s.l. and did not
rise above the cloud deck. Overnight during 18-19 September small,
discontinuous, low-level ash plumes were visible drifting 100 km SE. Ash
emissions increased in frequency and intensity on 19 September. Ash clouds
rose as high as 4.6 km (15,000 ft) a.s.l. and continued to drift 100 km SE.
Sulfur dioxide emissions increased in the afternoon. AVO raised the
Aviation Color Code to Red and the Volcano Alert Level to Warning at 2158.
Explosions continued overnight and the next day, and ash plumes rose up to
4.6 km a.s.l. Plumes drifted 100 km NW. At 2012 on 20 September AVO lowered
the Aviation Color Code to Orange noting the frequency of discrete
explosions had decreased to a rate of about one per hour, though ash plumes
from these events were still rising to 4.6 km a.s.l. and drifting NW.
Sulfur dioxide plumes drifted N during 20-21 September.

Geologic Summary. Semisopochnoi, the largest subaerial volcano of the
western Aleutians, is 20 km wide at sea level and contains an 8-km-wide
caldera. It formed as a result of collapse of a low-angle, dominantly
basaltic volcano following the eruption of a large volume of dacitic
pumice. The high point of the island is Anvil Peak, a double-peaked
late-Pleistocene cone that forms much of the island's northern part. The
three-peaked Mount Cerberus was constructed within the caldera during the
Holocene. Each of the peaks contains a summit crater; lava flows on the N
flank of Cerberus appear younger than those on the south side. Other
post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the
caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake
in the NE part of the caldera. Most documented eruptions have originated
from Cerberus, although Coats (1950) considered that both Sugarloaf and
Lakeshore Cone could have been recently active.

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDi6IJCA4$

Ongoing Activity

Agung  | Bali (Indonesia)  | 8.343Â°S, 115.508Â°E  | Summit elev. 2997 m

PVMBG reported that activity at Agung was last observed on 13 June 2019 and
a thermal anomaly over the crater was last identified in satellite images
in October 2019. During the previous year deformation data indicated no
changes at the volcano and seismicity decreased. During 1 Janaury-13
September white gas-and-steam plumes rose 20-50 m above the summit. On 13
September the Alert Level was lowered to 1 (on a scale of 1-4).

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

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM)
https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDUc2aqkU$

Aira  | Kyushu (Japan)  | 31.593Â°N, 130.657Â°E  | Summit elev. 1117 m

JMA reported that an explosion at Minamidake Crater (at Aira Caldera's
Sakurajima volcano) at 1617 on 19 September produced an eruption plume that
rose 1 km above the crater rim. Crater incandescence was visible at night
during 20-21 September. The report noted that inflation around the summit
continued to be recorded. The Alert Level remained at 3 (on a 5-level
scale), and residents were warned to stay 2 km away from the crater.

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

Source: Japan Meteorological Agency (JMA)
https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDk50pKIs$

Chirinkotan  | Kuril Islands (Russia)  | 48.98Â°N, 153.48Â°E  | Summit elev.
724 m

SVERT and KVERT reported that volcanic activity at Chirinkotan was last
observed during 23-24 August. The Aviation Color Code was lowered to Green
in mid to late September.

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

Sources: Sakhalin Volcanic Eruption Response Team (SVERT)
https://urldefense.com/v3/__http://www.imgg.ru/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDyCLBtIA$
 ;
Kamchatkan Volcanic Eruption Response Team (KVERT)
https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD7NXdmPI$

Ebeko  | Paramushir Island (Russia)  | 50.686Â°N, 156.014Â°E  | Summit elev.
1103 m

According to volcanologists in Severo-Kurilsk (Paramushir Island), about 7
km E of Ebeko, explosions during 10-11 September produced ash plumes that
rose as high as 2 km (6,600 ft) a.s.l. and drifted S and SE. The Aviation
Color Code remained at Orange (the second highest level on a four-color
scale).

Geologic Summary. The flat-topped summit of the central cone of Ebeko
volcano, one of the most active in the Kuril Islands, occupies the northern
end of Paramushir Island. Three summit craters located along a SSW-NNE line
form Ebeko volcano proper, at the northern end of a complex of five
volcanic cones. Blocky lava flows extend west from Ebeko and SE from the
neighboring Nezametnyi cone. The eastern part of the southern crater
contains strong solfataras and a large boiling spring. The central crater
is filled by a lake about 20 m deep whose shores are lined with steaming
solfataras; the northern crater lies across a narrow, low barrier from the
central crater and contains a small, cold crescentic lake. Historical
activity, recorded since the late-18th century, has been restricted to
small-to-moderate explosive eruptions from the summit craters. Intense
fumarolic activity occurs in the summit craters, on the outer flanks of the
cone, and in lateral explosion craters.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD7NXdmPI$

Etna  | Sicily (Italy)  | 37.748Â°N, 14.999Â°E  | Summit elev. 3320 m

INGV reported that tremor amplitude at Etna began gradually increasing at
0420 on 21 September and then suddenly increased at 0440. Ash emissions
rose from the Southeast Crater (SEC) at 0815 and by 0855 Strombolian
activity was visible. An eruption plume rose 4.5 km above the summit and
drifted ENE. Within an hour lava fountaining began and the plume rose 9 km
and drifted ENE. Lava overflowed the crater and traveled SW. Lava
fountaining had ceased by 1130, though Strombolian activity within the
crater continued. Tremor amplitude decreased at 1250 and explosive activity
ceased.

Geologic Summary. 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.

Source: Sezione di Catania - Osservatorio Etneo (INGV)
https://urldefense.com/v3/__http://www.ct.ingv.it/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD8FD16UM$

Great Sitkin  | Andreanof Islands (USA)  | 52.076Â°N, 176.13Â°W  | Summit
elev. 1740 m

AVO reported that lava effusion continued at Great Sitkin during 15-21
September, though weather clouds often prevented webcam and satellite
views. Seismicity remained elevated and was characterized by small
earthquakes consistent with lava effusion. A radar image from 16 September
indicated that the lava dome had grown to 1,130 m E-W and 910 m N-S, and
was about 30 m thick. The edges of the dome touched the S and W rims of the
crater. Elevated surface temperatures were identified in satellite data
during 20-21 September. The Aviation Color Code and the Volcano Alert Level
remained at Orange and Watch, respectively.

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

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDi6IJCA4$

Karymsky  | Eastern Kamchatka (Russia)  | 54.049Â°N, 159.443Â°E  | Summit
elev. 1513 m

KVERT reported that a thermal anomaly over Karymsky was identified in
satellite images during 10-17 September. Ash plumes rose as high as 7 km
(23,000 ft) a.s.l. and drifted 180 km E and SE during 10 and 15-16
September. The Aviation Color Code remained at Orange (the second highest
level on a four-color scale).

Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern
volcanic zone, is a symmetrical stratovolcano constructed within a
5-km-wide caldera that formed during the early Holocene. The caldera cuts
the south side of the Pleistocene Dvor volcano and is located outside the
north margin of the large mid-Pleistocene Polovinka caldera, which contains
the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding
Karymsky eruptions originated beneath Akademia Nauk caldera, located
immediately south. The caldera enclosing Karymsky formed about 7600-7700
radiocarbon years ago; construction of the stratovolcano began about 2000
years later. The latest eruptive period began about 500 years ago,
following a 2300-year quiescence. Much of the cone is mantled by lava flows
less than 200 years old. Historical eruptions have been vulcanian or
vulcanian-strombolian with moderate explosive activity and occasional lava
flows from the summit crater.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD7NXdmPI$

Katmai  | United States  | 58.28Â°N, 154.963Â°W  | Summit elev. 2047 m

AVO reported that on 21 September strong winds in the vicinity of Katmai
and the Valley of Ten Thousand Smokes blew unconsolidated ash SE towards
Kodiak Island at an altitude up to 2.4 km (8,000 ft) a.s.l. The ash was
originally deposited during the Novarupta eruption in 1912. The Volcano
Alert Level remained at Normal and the Aviation Color Code remained at
Green.

Geologic Summary. Prior to 1912, Mount Katmai was a compound stratovolcano
with four NE-SW-trending summits, most of which were truncated by caldera
collapse in that year. Two or more large explosive eruptions took place
from Mount Katmai during the late Pleistocene. Most of the two overlapping
pre-1912 Katmai volcanoes are Pleistocene in age, but Holocene lava flows
from a flank vent descend the SE flank of the SW stratovolcano into the
Katmai River canyon. Katmai was initially considered to be the source of
the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km
wide caldera of 1912 is now known to have formed as a result of the
voluminous eruption at nearby Novarupta volcano. The steep walled young
caldera has a jagged rim that rises 500-1000 m above the caldera floor and
contains a 250-m-deep, still-rising lake. Lake waters have covered a small
post-collapse lava dome (Horseshoe Island) that was seen on the caldera
floor at the time of the initial ascent to the caldera rim in 1916.
Post-1912 glaciers have formed on a bench within Katmai caldera.

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDi6IJCA4$

Krysuvik-Trolladyngja  | Iceland  | 63.917Â°N, 22.067Â°W  | Summit elev. 360 m

The eruption from the fifth vent in the W part of the KrÃ½suvÃk-TrÃ¶lladyngja
volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula,
continued during 15-18 September. According to a news article lava ponded
for a few days in Geldingadalur, and during 14-15 September the crust
ruptured and sent a larger lava flow rapidly into the S part of the valley;
the flow then turned E into the NÃ tthagi valley. Authorities temporarily
closed the area due to the activity and the large number of tourists; the
Coast Guard rescued two people whose exit route had been cut off by the
flow. Lava continued to flow on this path during 16-17 September and
overtook the "A" hiking trail. Later that day at around 1800 the flow rate
decreased or paused, and only minor incandescence from the vent was visible.

The Institute of Earth Sciences reported that based on aerial photography
acquired on 17 September the area of the flow field had grown to 4.8 square
kilometers, and the total volume erupted was 151 million cubic meters. The
lava-flow rate during 11-17 September averaged 16 cubic meters per second.
IMO noted that 19 September marked six months since the eruption started.

Geologic Summary. The KrÃ½suvÃk-TrÃ¶lladyngja volcanic system is described by
the Catalogue of Icelandic Volcanoes as an approximately 50-km-long
composite fissure swarm trending about N38Â°E, including a 30-km-long swarm
of fissures, with no central volcano. It is one of the volcanic systems
arranged en-echelon along the Reykjanes Peninsula west of Kleifarvatn lake.
The Fagradalsfjall and KrÃ½suvÃk fissure swarms are considered splits or
secondary swarms of the KrÃ½suvÃk-TrÃ¶lladyngja volcanic system. Small shield
volcanoes have produced a large portion of the erupted volume within the
system. Several eruptions have taken place since the settlement of Iceland,
including the eruption of a large basaltic lava flow from the Ogmundargigar
crater row around the 12th century. The latest eruption, identified through
tephrochronology, took place during the 14th century.

Sources: Icelandic Meteorological Office (IMO)
https://urldefense.com/v3/__http://en.vedur.is/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDetobkw4$
 ;
Institute of Earth Sciences
https://urldefense.com/v3/__http://www.earthice.hi.is/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD8LCU8nQ$
 ;
Icelandic National Broadcasting Service (RUV)
https://urldefense.com/v3/__https://www.ruv.is/frett/2021/09/15/gekk-upp-a-gigbarminn-i-geldingadolum__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDw7PJ-Ec$
 ;
Icelandic National Broadcasting Service (RUV)
https://urldefense.com/v3/__https://www.ruv.is/frett/2021/09/19/gosid-hefur-vid-fagradalsfjall-i-halft-ar__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDILnqg-o$
 ;
Almannavarnadeild rÃkislÃ¶greglustjÃ³ra (National Commissioner of the
Icelandic Police and Department of Civil Protection and Emergency
Management)
https://urldefense.com/v3/__https://www.almannavarnir.is/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDGNFDPLA$
 ;
Dr. Evgenia Ilyinskaya (University of Leeds)
https://urldefense.com/v3/__https://environment.leeds.ac.uk/see/staff/1344/dr-evgenia-ilyinskaya__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDEAQ51sw$

Merapi  | Central Java (Indonesia)  | 7.54Â°S, 110.446Â°E  | Summit elev.
2910 m

BPPTKG reported that no morphological changes to Merapi's two lava domes,
situated just below the SW rim and in the summit crater, were detected
during 10-16 September. As many as 144 lava avalanches traveled a maximum
of 2 km SW. The Alert Level remained at 3 (on a scale of 1-4), and the
public was warned to stay 3-5 km away from the summit based on location.

Geologic Summary. 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.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi
(BPPTKG)
https://urldefense.com/v3/__http://www.merapi.bgl.esdm.go.id/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDrvzeHng$

Pavlof  | United States  | 55.417Â°N, 161.894Â°W  | Summit elev. 2493 m

AVO reported that periods of elevated seismic tremor with no clear
explosion signals were recorded at Pavlof during 14-18 September. Webcam
images were mostly obscured by weather clouds. Minor ash deposits on the
upper flanks and at least one minor ash emission was visible in a clear
webcam view on 18 September. Small low-level ash emissions that dissipated
quickly were noted by observers and visible in webcam images at 1500 on 19
September and at 0900 on 20 September. Ash deposits on the mid-flanks were
identified in satellite data. Seismicity remained elevated during 2021
September; an explosion was recorded early on the 21 September. The vent in
the crater continued to migrate N based on satellite data. The Volcano
Alert Level and Aviation Color Code remained at Watch and Orange,
respectively.

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

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDi6IJCA4$

Popocatepetl  | Mexico  | 19.023Â°N, 98.622Â°W  | Summit elev. 5393 m

CENAPRED reported that each day during 14-21 September there were 89-152
steam-and-gas emissions from PopocatÃ©petl. The plumes drifted mainly NW and
some contained ash. As many as five daily explosions were recorded during
14-19 September and some ejected incandescent material onto the flanks.
Explosions at 1818, 1839, and 2350 on 14 September produced ash plumes that
rose 1.2-1.5 km above the crater rim. Explosions at 1015 and 1441 on 15
September produced ash plumes that rose 1.8-2.2 km. During 15-17 September
minor ashfall was reported in the municipalities of Cuernavaca, Valle de
Chalco, Chiautla, Ixtapaluca, NezahualcÃ³yotl, La Paz, Ecatepec, Ayapango,
Temamatla, Tenango del Aire, Tlalmanalco, Amecameca, Tepetlixpa,
Tlalnepantla, and Acolman in the MÃ©xico State, and in Iztapalapa,
Xochimilco, and Tlahuac in MÃ©xico City. The Alert Level remained at Yellow,
Phase Two (middle level on a three-color scale).

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

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)
https://urldefense.com/v3/__https://www.gob.mx/cenapred__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDqd4zA1Q$

Sheveluch  | Central Kamchatka (Russia)  | 56.653Â°N, 161.36Â°E  | Summit
elev. 3283 m

KVERT reported that a thermal anomaly over Sheveluch was identified in
satellite images during 10-17 September. The Aviation Color Code remained
at Orange (the second highest level on a four-color scale).

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

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YD7NXdmPI$

Soufriere St. Vincent  | St. Vincent  | 13.33Â°N, 61.18Â°W  | Summit elev.
1220 m

National Emergency Management Organisation (NEMO) reported that activity at
SoufriÃ¨re St. Vincent had been low over the previous few months. On 15
September the Alert Level was lowered to Yellow and remaining evacuees were
allowed to return home.

Geologic Summary. SoufriÃ¨re St. Vincent is the northernmost and youngest
volcano on St. Vincent Island. The NE rim of the 1.6-km wide summit crater
is cut by a crater formed in 1812. The crater itself lies on the SW margin
of a larger 2.2-km-wide caldera, which is breached widely to the SW as a
result of slope failure. Frequent explosive eruptions after about 4,300
years ago produced pyroclastic deposits of the Yellow Tephra Formation,
which cover much of the island. The first historical eruption took place in
1718; it and the 1812 eruption produced major explosions. Much of the
northern end of the island was devastated by a major eruption in 1902 that
coincided with the catastrophic Mont PelÃ©e eruption on Martinique. A lava
dome was emplaced in the summit crater in 1971 during a strictly effusive
eruption, forming an island within a lake that filled the crater. A series
of explosive eruptions in 1979 destroyed the 1971 dome and ejected the
lake; a new dome was then built.

Source: National Emergency Management Organisation (NEMO), Government of
Saint Vincent and the Grenadines
https://urldefense.com/v3/__http://nemo.gov.lc/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDwQnQh4w$

Suwanosejima  | Ryukyu Islands (Japan)  | 29.638Â°N, 129.714Â°E  | Summit
elev. 796 m

JMA reported that the number of daily explosions at Suwanosejima's Ontake
Crater increased on 16 September and remained elevated through 20
September. Eruption plumes rose as high as 2.4 km above the crater rim and
material was generally ejected 300 m away from the crater. Notably,
explosions at 2014 on 16 September and at 0212 on 17 September ejected
material almost 1 km S and SE, respectively. The Alert Level remained at 2
and the public was warned to stay 1 km away from the crater.

Geologic Summary. 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.

Source: Japan Meteorological Agency (JMA)
https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!OsSl_Z-fNhmbyhWMCrxUU1A1SheUA6cKwSRKbNnYjWm2BM46eQ2Iu4YDk50pKIs$

2-2-2-2-2-2-2-2-2-2-2-2-2

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PSU - https://urldefense.com/v3/__http://pdx.edu/__;!!IKRxdwAv5BmarQ!MwTgTEPTOTVZgCJ87nGL8yf8ITtQJcF5gddABePgq1TfnYWvc6Kr2ofZrlPI4nI$ 

GVP - https://urldefense.com/v3/__http://www.volcano.si.edu/__;!!IKRxdwAv5BmarQ!MwTgTEPTOTVZgCJ87nGL8yf8ITtQJcF5gddABePgq1TfnYWvc6Kr2ofZoFnk35Q$ 

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End of Volcano Digest - 17 Sep 2021 to 22 Sep 2021 (#2021-88)
*************************************************************