Smithsonian / USGS Weekly Volcanic Activity Report 13-19 January 2021

Rachel Holsteen-Bruyere <rbruyere@xxxxxxx> · Wed, 20 Jan 2021 12:50:26 -0700

5-5-5-5-5-5-5-5-5-5-5-5-5-5

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

Smithsonian / USGS Weekly Volcanic Activity Report

13-19 January 2021

Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)

URL: https://volcano.si.edu/reports_weekly.cfm

Ongoing Activity: Aira, Kyushu (Japan)  | Dukono, Halmahera (Indonesia)  |
Ebeko, Paramushir Island (Russia)  | Etna, Sicily (Italy)  | Karymsky,
Eastern Kamchatka (Russia)  | Klyuchevskoy, Central Kamchatka (Russia)  |
Lewotolo, Lomblen Island (Indonesia)  | Ruapehu, North Island (New
Zealand)  | Sabancaya, Peru  | Semeru, Eastern Java (Indonesia)  |
Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  |
Sinabung, Indonesia  | Veniaminof, United States  | Yasur, Vanuatu

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

Kilauea  | Hawaiian Islands (USA)  | 19.421Â°N, 155.287Â°W  | Summit elev.
1222 m

HVO reported that low lava fountains from a vent on a cone on the inner NW
wall of Kilaueaâ??s Halema`uma`u Crater fed flows that traveled down a
channel into a perched lava lake during 13-19 January. The western half of
the lake deepened from 198 m to 202 m while the stagnant eastern half
remained a few meters lower. The lake was perched 1-2 m above the rim. On
13 January a small portion of the cone collapsed, causing a second vent to
open adjacent to the main vent and effuse lava for less than 20 minutes.
The islands remained stationary in the E part of the lake; the dimensions
of the largest island remained unchanged. The sulfur dioxide emission rate
was 4,700 tons/day on 14 January.

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

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
https://volcanoes.usgs.gov/observatories/hvo/

Langila  | New Britain (Papua New Guinea)  | 5.525Â°S, 148.42Â°E  | Summit
elev. 1330 m

Based on analyses of satellite imagery and wind model data, the Darwin VAAC
reported that on 13 January an ash plume from Langila produced an ash plume
that rose to 3 km (10,000 ft) a.s.l. and drifted WSW.

Geologic Summary. Langila, one of the most active volcanoes of New Britain,
consists of a group of four small overlapping composite basaltic-andesitic
cones on the lower E flank of the extinct Talawe volcano in the Cape
Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is
breached widely to the SE; Langila was constructed NE of the breached
crater of Talawe. An extensive lava field reaches the coast on the N and NE
sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes
accompanied by lava flows, have been recorded since the 19th century from
three active craters at the summit. The youngest and smallest crater (no. 3
crater) was formed in 1960 and has a diameter of 150 m.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml

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

BPPTKG reported that the â??2021 lava domeâ?? continued to emerge just below
Merapiâ??s SW rim during 8-14 January, producing a total of 128 incandescent
lava avalanches that traveled as far as 900 m down the Krasak River
drainage on the SW flank. A comparison of photos taken on 7 and 14 January
showed that the morphological changes in the summit area were attributed to
the emergence of new lava domes. The 2021 dome volume was an estimated
46,766 cubic meters on 14 January, with a growth rate of about 8,500 cubic
meters per day. Deformation continued, though at a lower rate; Electronic
Distance Measurement (EDM) data showed a distance shortening between points
in the NW at a rate of 6 cm per day. Seismic activity significantly
decreased compared to the previous week.

At around 0400 on 16 January a pyroclastic flow descended 1.5 km down the
Krasak drainage and produced an ash plume that rose 500 m. A pyroclastic
flow was visible in webcam images around 1700 on 16 January, though
somewhat obscured due to weather clouds, and traveled an estimated 1 km.
>From 1800 on 16 January to 0600 on 17 January there were a total of 56
incandescent lava avalanches that went a maximum distance of 1.5 km SW.
During the first six hours of 18 January six incandescent avalanches
descended 600 m SW. At 0543 a pyroclastic flow traveled about 1 km down the
Krasak drainage and produced an ash plume that rose 50 m above the summit
and drifted SE. The Alert Level remained at 3 (on a scale of 1-4), and the
public were warned to stay 5 km away from the summit.

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) http://www.merapi.bgl.esdm.go.id/

Pelee  | Martinique (France)  | 14.809Â°N, 61.165Â°W  | Summit elev. 1394 m

L'Observatoire Volcanologique et Sismologique de Martinique (OVSM) reported
that seismicity at PelÃ©e remained at significant levels during 8-15
January, though had slightly decreased compared to the previous week. The
seismic network recorded at least 22 high-frequency, volcano-tectonic
earthquakes with magnitudes less than 1, located at shallow depths between
600 and 1,000 m above sea level. Two low-frequency, long-period earthquakes
were also noted. The Alert Level remained at Yellow (the second lowest
level on a four-color scale).

Geologic Summary. Renowned Montagne PelÃ©e forms the northern end of the
island of Martinique. Three major edifice failures since the late
Pleistocene, the last about 9,000 years ago, have left large open calderas
breached to the SW inside which the modern volcano has been constructed.
More than 20 major eruptions have occurred here during the past 5,000
years. Extensive pyroclastic-flow deposits, incised by steep-walled
ravines, mantle the slopes of the volcano. The l'Etang Sec summit crater is
filled by two lava domes emplaced during the 1902 and 1929 eruptions.
Recorded eruptions date back to the 18th century; only two modest phreatic
or phreatomagmatic eruptions took place prior to 1902. The catastrophic
1902 eruption, which destroyed the city of St. Pierre, became the
type-example of Pelean eruptions and marked the onset of modern
volcanological studies of the behavior of pyroclastic flows.

Source: L'Observatoire Volcanologique et Sismologique de Martinique (OVSM)
http://www.ipgp.fr/fr/ovsm/lobservatoire-volcanologique-sismologique-de-martinique-ovsm-ipgp

Sarychev Peak  | Matua Island (Russia)  | 48.092Â°N, 153.2Â°E  | Summit elev.
1496 m

KVERT reported that a thermal anomaly over Sarychev Peak was identified
during 7-10 and 12-13 January. A gas-and-steam plume drifted 40 km NE on 12
January. The Aviation Color Code was raised to Yellow (the second lowest
level on a four-color scale) on 10 January.

Geologic Summary. Sarychev Peak, one of the most active volcanoes of the
Kuril Islands, occupies the NW end of Matua Island in the central Kuriles.
The andesitic central cone was constructed within a 3-3.5-km-wide caldera,
whose rim is exposed only on the SW side. A dramatic 250-m-wide, very
steep-walled crater with a jagged rim caps the volcano. The substantially
higher SE rim forms the 1496 m high point of the island. Fresh-looking lava
flows, prior to activity in 2009, had descended in all directions, often
forming capes along the coast. Much of the lower-angle outer flanks of the
volcano are overlain by pyroclastic-flow deposits. Eruptions have been
recorded since the 1760s and include both quiet lava effusion and violent
explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows
that reached the sea.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/index_eng.php

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

University of the West Indies Seismic Research Centre (UWI-SRC) and
National Emergency Management Organisation (NEMO) reported that the lava
dome in SoufriÃ¨re St. Vincentâ??s main crater continued to grow during 13-19
January.

Observations on 14 January revealed that the dome was growing taller as
well as expanding to the E and W. During an overflight on 15 January
scientists saw extensive vegetation damage on the E, S, and W inner crater
walls; damage previously noted along the upper part of the SW crater rim
had expanded downslope. The dome dimensions were estimated to be 340 m
long, 160 m wide, and 90 m high.

Scientists visited the dome on 16 January and collected rock samples from
the W part of the dome. They recorded temperatures around 590 degrees
Celsius from the expanding dome front. Gas emissions were most notable from
a small circular depression at the top of the dome. At night during 15-17
January residents to the W saw incandescence emanating from the crater, a
phenomenon likely to be more frequent as the dome grows higher. Gas
emissions were visible in the afternoon of 17 January rising from the top
of the dome as well as from areas of contact between the new and old domes.
An area of burnt vegetation extended from the dome along the W part of the
crater floor.

By the end of the week both new seismic and continuous GPS monitoring
stations had been installed and were transmitting data, bring the total
number of dedicated seismic stations to five. The Alert Level remained at
Orange (the second highest level on a four-color scale).

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.

Sources: University of the West Indies Seismic Research Centre (UWI-SRC)
http://www.uwiseismic.com/;

National Emergency Management Organisation (NEMO), Government of Saint
Vincent and the Grenadines http://nemo.gov.lc/

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

JMA reported that incandescence at Suwanosejimaâ??s Ontake Crater was visible
nightly during 11-15 January. Intermittent explosions produced ash plumes
that rose as high as 1.4 km above the crater rim and ejected bombs 400 m
away from the crater. The Alert Level was lowered to 2 (on a 5-level scale)
on 14 January; JMA noted that no large bombs were ejected more than 1 km
from the crater beginning on 29 December 2020.

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) http://www.jma.go.jp/jma/

Ongoing Activity

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

JMA reported that during 11-18 January incandescence from Minamidake Crater
(at Aira Calderaâ??s Sakurajima volcano) was often visible nightly. The
sulfur dioxide emission rate remained high, reaching 2,100 tons per day on
13 January. Five explosions and three eruptive events were recorded,
producing eruption plumes that rose 1.3-2 km above the crater rim and
ejecting bombs 500-900 m away from the crater. The Alert Level remained at
3 (on a 5-level scale).

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) http://www.jma.go.jp/jma/

Dukono  | Halmahera (Indonesia)  | 1.693Â°N, 127.894Â°E  | Summit elev. 1229 m

Based on satellite and wind model data, the Darwin VAAC reported that
during 13-14 January ash plumes from Dukono rose to 2.1 km (7,000 ft)
a.s.l. and drifted E and WSW. The Alert Level remained at 2 (on a scale of
1-4), and the public was warned to remain outside of the 2-km exclusion
zone.

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

Sources: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml;

Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
http://vsi.esdm.go.id/

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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of
Ebeko, observed explosions during 7-10 and 13-14 January; ash plumes rose
up to 4.5 km (14,800 ft) a.s.l. and drifted E. 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)
http://www.kscnet.ru/ivs/kvert/index_eng.php

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

INGV reported that during 11-17 January activity at Etna was characterized
by intra-crater Strombolian activity at Northeast Crater (NEC), occasional
ash emissions from the Voragine (VOR) and Bocca Nuova (BN) craters, and
Strombolian activity, lava effusion, and ash emissions at the Southeast
Crater (SEC). In general, the activity was similar to the pervious week,
though activity at SEC on 18 January was notable.

Lava effusion began around 0700 on 17 January but was confined to the SEC
summit cone. At around 0740 the lava breached the crater and lava flowed
down to the base of the cone. The effusion rate increased by 0819 and an
ash emission was possibly visible; the lava flow lengthened and had reached
an elevation of 3,000 m by 1000. Weather clouds moved in and prevented
visual observations until 1830 on 18 January when the lava flow was visible
again; it was no longer being fed and was cooling. Volcanic tremor
amplitude increased and Strombolian activity intensified at 2000. A new
lava flow emerged at 2015 and traveled towards the Valle del Bove, reaching
an elevation of 2,900 m. Low lava fountains were visible at 2130 and an ash
plume drifted ESE, causing ashfall on the downwind flank. Lava flows
descended the SE, E, and NE flanks of the SEC. Explosive activity
significantly decreased at 2200. Two distinct lava flows were visible, with
one heading N and the other moving towards the Valle del Bove. Tremor and
infrasound signals decreased to pre-episode levels by 2230. The the lava
flows were stable and cooling on 19 January.

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)
http://www.ct.ingv.it/

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

KVERT reported that a thermal anomaly over Karymsky was visible in
satellite images during 8-15 January. 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)
http://www.kscnet.ru/ivs/kvert/index_eng.php

Klyuchevskoy  | Central Kamchatka (Russia)  | 56.056Â°N, 160.642Â°E  | Summit
elev. 4754 m

KVERT reported that Strombolian and sometimes Vulcanian activity at
Klyuchevskoy continued during 8-15 January and lava advanced down the
Kozyrevsky drainage on the S flank. A large bright thermal anomaly was
identified daily in satellite images. Steam-and-gas plumes with some ash
rose to 6 km (19,700 ft) a.s.l. and drifted 90 km in multiple directions.
The Aviation Color Code remined at Orange (the second highest level on a
four-color scale).

Geologic Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's
highest and most active volcano. Since its origin about 6000 years ago, the
beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced
frequent moderate-volume explosive and effusive eruptions without major
periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen
volcano and lies SE of the broad Ushkovsky massif. More than 100 flank
eruptions have occurred during the past roughly 3000 years, with most
lateral craters and cones occurring along radial fissures between the
unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m
elevation. The morphology of the 700-m-wide summit crater has been
frequently modified by historical eruptions, which have been recorded since
the late-17th century. Historical eruptions have originated primarily from
the summit crater, but have also included numerous major explosive and
effusive eruptions from flank craters.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/index_eng.php

Lewotolo  | Lomblen Island (Indonesia)  | 8.274Â°S, 123.508Â°E  | Summit
elev. 1431 m

PVMBG reported that a Strombolian eruption at Lewotolo continued during
13-19 January. Gray-and-white ash plumes rose 200-700 m above the summit
daily and rumbling sounds were reported. Strombolian explosions ejected
material 100-500 m above the summit, and incandescent material was ejected
as far as 1.5 km SE from the crater. The Alert Level remained at 3 (on a
scale of 1-4) and the public was warned to stay 4 km away from the summer
crater.

Geologic Summary. The Lewotolo (or Lewotolok) stratovolcano occupies the
eastern end of an elongated peninsula extending north into the Flores Sea,
connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is
symmetrical when viewed from the north and east. A small cone with a
130-m-wide crater constructed at the SE side of a larger crater forms the
volcano's high point. Many lava flows have reached the coastline. Eruptions
recorded since 1660 have consisted of explosive activity from the summit
crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) http://vsi.esdm.go.id/

Ruapehu  | North Island (New Zealand)  | 39.28Â°S, 175.57Â°E  | Summit elev.
2797 m

GeoNet reported that volcanic tremor at Ruapehu declined to low levels on
29 December 2020, and remained low; volcanic gas emissions returned to
background levels by the next day. Water chemistry had only slightly
changed compared to data collected a few weeks prior. Although the
temperature of the crater lake water remained high (40 degrees Celsius),
the period of heightened unrest was over; the Volcanic Alert Level was
lowered to 1 and the Aviation Color Code was lowered to Green on 11 January.

Geologic Summary. Ruapehu, one of New Zealand's most active volcanoes, is a
complex stratovolcano constructed during at least four cone-building
episodes dating back to about 200,000 years ago. The dominantly andesitic
110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded
by another 100 km3 ring plain of volcaniclastic debris, including the
Murimoto debris-avalanche deposit on the NW flank. A series of subplinian
eruptions took place between about 22,600 and 10,000 years ago, but
pyroclastic flows have been infrequent. A single historically active vent,
Crater Lake (Te Wai a-moe), is located in the broad summit region, but at
least five other vents on the summit and flank have been active during the
Holocene. Frequent mild-to-moderate explosive eruptions have occurred in
historical time from the Crater Lake vent, and tephra characteristics
suggest that the crater lake may have formed as early as 3,000 years ago.
Lahars produced by phreatic eruptions from the summit crater lake are a
hazard to a ski area on the upper flanks and to lower river valleys.

Source: GeoNet http://www.geonet.org.nz/

Sabancaya  | Peru  | 15.787Â°S, 71.857Â°W  | Summit elev. 5960 m

Instituto GeofÃsico del PerÃº (IGP) reported a daily average of 29
explosions at Sabancaya during 11-17 January. Gas-and-ash plumes rose as
high as 3 km above the summit and drifted in multiple directions. One
thermal anomaly over the crater was identified in satellite data. Minor
inflation continued to be detected in areas N of Hualca Hualca (4 km N) and
on the SE flank. The Alert Level remained at Orange (the second highest
level on a four-color scale) and the public were warned to stay outside of
a 12-km radius.

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

Source: Instituto GeofÃsico del PerÃº (IGP) http://www.igp.gob.pe/

Semeru  | Eastern Java (Indonesia)  | 8.108Â°S, 112.922Â°E  | Summit elev.
3657 m

PVMBG reported that during 1-15 January incandescent avalanches of material
from the Jonggring Seleko Crater at Semeru sometimes traveled 500-1,000 m
down the Kobokan drainage on the SE flank. Incandescent material was
ejected 10-30 m above the summit and white-and-gray plumes rose 200-300 m
and drifted N. Weather conditions often prevented visual observations. A
pyroclastic flow was detected at 1451 on 1 January, though weather clouds
prevented visual confirmation. At 1724 on 16 January incandescent
avalanches traveled as far as 1 km down the Kobokan drainage and a
pyroclastic flow traveled about 4-4.5 km down the same drainage. A large
ash cloud rose along the length of the pyroclastic flow to 2 km above the
summit and drifted NE and N. Ashfall was reported in areas to the N. During
18-19 January dense gray-white plumes rose 300-500 m above the summit and
drifted N. Rumbling was heard and incandescent material was ejected 30 m
high. The Alert Level remained at 2 (on a scale of 1-4), with a general
exclusion zone of 1 km and extensions to 4 km in the SSE sector.

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

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) http://vsi.esdm.go.id/;

Badan Nacional Penanggulangan Bencana (BNPB) http://www.bnpb.go.id/;

The Jakarta Post
https://www.thejakartapost.com/index.php/news/2021/01/16/mount-semeru-spews-clouds-of-gas-ash.html?src=mostviewed

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 8-15 January. 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)
http://www.kscnet.ru/ivs/kvert/index_eng.php

Shishaldin  | Fox Islands (USA)  | 54.756Â°N, 163.97Â°W  | Summit elev. 2857 m

AVO reported that several outages affected GPS, seismic, and infrasound
stations used to monitor Shishaldin. On 15 January AVO changed both the
Aviation Color Code and the Volcano Alert Level to Unassigned, reflecting
the lack of this data to detect unrest. The volcano continued to be
monitored with local webcams, satellite data, and remote infrasound,
seismic, and lightning networks.

Geologic Summary. The beautifully symmetrical Shishaldin is the highest and
one of the most active volcanoes of the Aleutian Islands. The
glacier-covered volcano is the westernmost of three large stratovolcanoes
along an E-W line in the eastern half of Unimak Island. The Aleuts named
the volcano Sisquk, meaning "mountain which points the way when I am lost."
A steam plume often rises from its small summit crater. Constructed atop an
older glacially dissected volcano, it is largely basaltic in composition.
Remnants of an older ancestral volcano are exposed on the W and NE sides at
1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its
NW flank, which is blanketed by massive aa lava flows. Frequent explosive
activity, primarily consisting of Strombolian ash eruptions from the small
summit crater, but sometimes producing lava flows, has been recorded since
the 18th century.

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://avo.alaska.edu/

Sinabung  | Indonesia  | 3.17Â°N, 98.392Â°E  | Summit elev. 2460 m

PVMBG reported that the eruption at Sinabung continued during 13-19
January, though weather conditions often prevented visual conformation.
White-and-gray ash plumes rose as high as 500 m above the summit during
14-15 January, and avalanches of material traveled 700-1,000 m down the SE
flank. Dense white-and-gray ash plumes rose 500 m during 17-18 January. The
Alert Level remained at 3 (on a scale of 1-4), with a general exclusion
zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE
sector.

Geologic Summary. Gunung Sinabung is a Pleistocene-to-Holocene
stratovolcano with many lava flows on its flanks. The migration of summit
vents along a N-S line gives the summit crater complex an elongated form.
The youngest crater of this conical andesitic-to-dacitic edifice is at the
southern end of the four overlapping summit craters. The youngest deposit
is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at
740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric
activity was seen at the summit and upper flanks in 1912. No confirmed
historical eruptions were recorded prior to explosive eruptions during
August-September 2010 that produced ash plumes to 5 km above the summit.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) http://vsi.esdm.go.id/;

Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml

Veniaminof  | United States  | 56.17Â°N, 159.38Â°W  | Summit elev. 2507 m

AVO reported that seismic data for Veniaminof had not been received since 8
December 2020 due to a problem with the satellite link at Port Heiden. Both
the Aviation Color Code and the Volcano Alert Level were changed to
Unassigned on 15 January, reflecting the lack of available seismic data to
detect unrest.

Geologic Summary. Veniaminof, on the Alaska Peninsula, is truncated by a
steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700
years ago. The caldera rim is up to 520 m high on the north, is deeply
notched on the west by Cone Glacier, and is covered by an ice sheet on the
south. Post-caldera vents are located along a NW-SE zone bisecting the
caldera that extends 55 km from near the Bering Sea coast, across the
caldera, and down the Pacific flank. Historical eruptions probably all
originated from the westernmost and most prominent of two intra-caldera
cones, which rises about 300 m above the surrounding icefield. The other
cone is larger, and has a summit crater or caldera that may reach 2.5 km in
diameter, but is more subdued and barely rises above the glacier surface.

Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://avo.alaska.edu/

Yasur  | Vanuatu  | 19.532Â°S, 169.447Â°E  | Summit elev. 361 m

Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that an
ash-and-gas emission rose above Yasurâ??s crater rim at 1734 on 18 January.
The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents
and tourists that hazardous areas were near and around the volcanic crater,
and that volcanic ash and gas could reach areas impacted by trade winds.

Geologic Summary. 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.

Source: Vanuatu Meteorology and Geo-Hazards Department (VMGD)
http://www.geohazards.gov.vu/

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End of Volcano Digest - 15 Jan 2021 to 20 Jan 2021 (#2021-6)
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