Smithsonian / USGS Weekly Volcanic Activity Report 21-27 July 2021

Rachel Holsteen-Bruyere <rbruyere@xxxxxxx> · Wed, 28 Jul 2021 12:05:32 -0700

3-3-3-3-3-3-3-3-3-3-3-3-3

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

Smithsonian / USGS Weekly Volcanic Activity Report

21-27 July 2021

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

URL: https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTOCsipV0$ 
<https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjtK9KqEU$>

New Activity/Unrest: Great Sitkin, Andreanof Islands (USA)  |
Semisopochnoi, Aleutian Islands (USA)  | Sirung, Pantar Island (Indonesia)
| Suwanosejima, Ryukyu Islands (Japan)  | Taal, Luzon (Philippines)  |
Turrialba, Costa Rica  | Whakaari/White Island, North Island (New Zealand)

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

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

AVO reported that a satellite image of Great Sitkin acquired at 0932 on 22
July showed a small area of uplift, about 50 m in diameter, and elevated
surface temperatures associated with the feature. These observations
suggested magma rising near the surface, prompting AVO to raise the
Aviation Color Code and the Volcano Alert Level to Orange and Watch,
respectively. Small earthquakes were recorded during 23-25 July. A 26 July
satellite image confirmed that the feature was a lava dome, and that it had
grown to 130 m in diameter. Seismic data suggested that the dome probably
emerged sometime during 14-22 July.

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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTN3NKTMI$ 
<https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjsUCMpMI$>

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

AVO lowered the Aviation Color Code to Yellow and the Volcano Alert Level
to Advisory for Semisopochnoi on 22 July, noting that explosive activity
had not been detected since 12 July. Seismicity continued to be elevated
during 23-27 July. Robust steam emissions were visible in webcam views
during 22-24 July and sulfur dioxide plumes were identified in satellite
images on 23 July. Weather clouds obscured views during 24-27 July.

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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTN3NKTMI$ 
<https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjsUCMpMI$>

Sirung  | Pantar Island (Indonesia)  | 8.508Â°S, 124.13Â°E  | Summit elev.
862 m

PVMBG reported that a phreatic eruption at Sirung was recorded at 1644 on
21 July. A white-and-gray ash plume rose 2 km above the summit and drifted
N. The report noted that the event was preceded by an increase in tremor
amplitude that lasted about 10 hours; no volcanic earthquakes indicating
magma movement were recorded and tremor amplitude did not notably increase.
The Alert Level was raised to 2 (on a scale of 1-4), with visitors and
tourists prohibited within a 1.5 km radius of Sirung.

Geologic Summary. Sirung volcano is located at the NE end of a 14-km-long
line of volcanic centers that form a peninsula at the southern end of
Pantar Island. The volcano is truncated by a 2-km-wide caldera whose floor
often contains one or more small lakes. Much of the volcano is constructed
of basaltic lava flows, and the Gunung Sirung lava dome forms the high
point on the caldera's western rim. A number of phreatic eruptions have
occurred from vents within the caldera during the 20th century. Forested
Gunung Topaki, the high point of the volcanic chain, lies at the SW end and
contains a symmetrical summit crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTJMLeD8w$ 
<https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjBnzuzyk$>

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

JMA reported ongoing explosions at Suwanosejima's Ontake Crater during
19-26 July and that crater incandescence was visible on some nights. There
were 31 explosions recorded on 22 July after two days of no explosions. An
explosion at 1500 on 23 July produced an ash plume that rose 1.6 km and
ejected bombs 200 m. Eruption plumes during 23-26 July rose as high as 2.3
km; it was unknown if bombs were ejected from the crater due to weather
conditions. The Alert Level remained at 3 and the public was warned to stay
2 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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTh3hy9Z8$ 
<https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjwtkEqjc$>

Taal  | Luzon (Philippines)  | 14.002Â°N, 120.993Â°E  | Summit elev. 311 m

PHIVOLCS lowered the Alert Level for Taal to 2 (on a scale of 0-5) on 23
July, noting that no eruptions had been recorded since the period of
phreatomagmatic activity during 1-9 July. Additionally, an overall decrease
was evident in multiple monitoring parameters. Sulfur dioxide emissions
peaked at 22,628 tonnes/day on 4 July and declined to an average of 4,763
tonnes/day during 8-22 July. Steam plumes continued to be generated from
the lake, rising 10-1,000 m, and lake upwelling was generally less
vigorous. The DROMIC report stated that 794 people were in evacuation
centers or private residences by 26 July. PHIVOLCS reminded the public that
the entire Taal Volcano Island is a Permanent Danger Zone (PDZ).

Geologic Summary. Taal is one of the most active volcanoes in the
Philippines and has produced some of its most powerful historical
eruptions. Though not topographically prominent, its prehistorical
eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km
Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2
surface lies only 3 m above sea level. The maximum depth of the lake is 160
m, and several eruptive centers lie submerged beneath the lake. The
5-km-wide Volcano Island in north-central Lake Taal is the location of all
historical eruptions. The island is composed of coalescing small
stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in
area during historical time. Powerful pyroclastic flows and surges from
historical eruptions have caused many fatalities.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtT-IisRm0$ 
<https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjQOiZR_g$>
;

Disaster Response Operations Monitoring and Information Center (DROMIC)
https://urldefense.com/v3/__https://dromic.dswd.gov.ph/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTZhW--Ro$ 
<https://urldefense.com/v3/__https://dromic.dswd.gov.ph/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjnQVUbso$>

Turrialba  | Costa Rica  | 10.025Â°N, 83.767Â°W  | Summit elev. 3340 m

OVSICORI-UNA reported that a one-minute-long eruption at Turrialba was
recorded at 1130 on 23 July, though weather clouds prevented visual
confirmation of an eruption plume. Ash fell in areas 3.5 km W.

Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene
volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located
across a broad saddle NE of IrazÃº volcano overlooking the city of Cartago.
The massive edifice covers an area of 500 km2. Three well-defined craters
occur at the upper SW end of a broad 800 x 2200 m summit depression that is
breached to the NE. Most activity originated from the summit vent complex,
but two pyroclastic cones are located on the SW flank. Five major explosive
eruptions have occurred during the past 3500 years. A series of explosive
eruptions during the 19th century were sometimes accompanied by pyroclastic
flows. Fumarolic activity continues at the central and SW summit craters.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad
Nacional (OVSICORI-UNA) https://urldefense.com/v3/__http://www.ovsicori.una.ac.cr/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTfdJLTPk$ 
<https://urldefense.com/v3/__http://www.ovsicori.una.ac.cr/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjc1SwtG0$>

Whakaari/White Island  | North Island (New Zealand)  | 37.52Â°S, 177.18Â°E  |
Summit elev. 294 m

GeoNet reported that crater incandescence at Whakaari/White Island, first
seen on 30 June, continued to be visible in nighttime webcam images. The
incandescence was attributed to high-temperature gasses. Additionally, the
gas ratio of carbon dioxide to sulfur dioxide declined, indicating ongoing
degassing from a shallow magma source. The Volcanic Alert Level was raised
to 2 and the Aviation Color Code was raised to Yellow on 26 July.

Geologic Summary. The uninhabited Whakaari/White Island is the 2 x 2.4 km
emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty
about 50 km offshore of North Island. The island consists of two
overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater
is open at sea level, with the recent activity centered about 1 km from the
shore close to the rear crater wall. Volckner Rocks, sea stacks that are
remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826
have included intermittent moderate phreatic, phreatomagmatic, and
Strombolian eruptions; activity there also forms a prominent part of Maori
legends. The formation of many new vents during the 19th and 20th centuries
caused rapid changes in crater floor topography. Collapse of the crater
wall in 1914 produced a debris avalanche that buried buildings and workers
at a sulfur-mining project. Explosive activity in December 2019 took place
while tourists were present, resulting in many fatalities. The official
government name Whakaari/White Island is a combination of the full Maori
name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island
(referencing the constant steam plume) given by Captain James Cook in 1769.

Source: GeoNet https://urldefense.com/v3/__http://www.geonet.org.nz/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTAYXD6pM$ 
<https://urldefense.com/v3/__http://www.geonet.org.nz/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjQv43yF0$>

Ongoing Activity

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

JMA reported that incandescence from Minamidake Crater (at Aira Calderaâ??s
Sakurajima volcano) was visible at night during 19-26 July. A very small
eruptive event was recorded on 19 July. The sulfur dioxide emission rate
was relatively elevated at 1,000 tons per day on 21 July. 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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTh3hy9Z8$ 
<https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjwtkEqjc$>

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 21-26 July ash plumes from Dukono rose to 1.8-2.1 km (6,000-7,000
ft) a.s.l. and drifted NE, E, and SE. 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)
https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTzw4h4XU$ 
<https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfj_lXE1qE$>
;

Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)
https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTJMLeD8w$ 
<https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjBnzuzyk$>

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 16-17 July produced ash plumes that rose
as high as 3 km (10,000 ft) a.s.l. and drifted E. Thermal anomalies were
identified in satellite images during 16 and 20-22 July. 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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTGO9dYms$ 
<https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjbi6TwXM$>

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 16 and 20-22 July and ash plumes were visible
drifting 100 km SE, NE, and N during 21-22 July. 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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTGO9dYms$ 
<https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjbi6TwXM$>

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

The fissure eruption in the W part of the KrÃ½suvÃk-TrÃ¶lladyngja volcanic
system, close to Fagradalsfjall on the Reykjanes Peninsula, continued
during 21-27 July. Lava fountaining and overflows from the fifth vent were
periodically visible, in between long pauses in the eruption, and lava from
the crater flowed in tubes as well as on the surface.

The Institute of Earth Sciences noted that during 2-19 July the lava
effusion rate averaged 7.5 cubic meters per second, which was notably lower
than averages in May and June. The area of the flow field had grown to
almost 4 square kilometers, and the total volume erupted was 96 million
cubic meters. Lava flowed into the Meradalir Valley and areas to the W, but
did not advance in the Geldingadalur, NÃ¡tthaga, and Sydri Meradalir (SE of
the fifth vent) valleys. The Aviation Color Code remained at Orange due to
the lack of ash and tephra emissions, though IMO warned of the potential
for lapilli and scoria fallout within a 650 m radius of the active vent.
Authorities warned of increased gas emissions hazards.

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 KrÃ½suvÃkâ??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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTVVeGEIU$ 
<https://urldefense.com/v3/__http://en.vedur.is/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfj92rsydQ$>;
Institute of Earth Sciences https://urldefense.com/v3/__http://www.earthice.hi.is/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtT4Pa6OgU$ 
<https://urldefense.com/v3/__http://www.earthice.hi.is/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjzca6GSg$>

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

PVMBG reported that daily white-and-gray plumes from Lewotolok rose as high
as 800 m and drifted in multiple directions during 20-25 July. The Alert
Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3
km away from the summit crater.

Geologic Summary. The Lewotolok (or Lewotolo) 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) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTJMLeD8w$ 
<https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjBnzuzyk$>

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

BPPTKG reported that the lava dome just below Merapiâ??s SW rim and the lava
dome in the summit crater both remained active during 16-22 July. The SW
rim lava-dome volume was an estimated 1.88 million cubic meters and
material continued to collapse down the flank. The volume of the summit
lava dome was 2.808 million cubic meters. Lava avalanches traveled a
maximum of 1.2 km SE (62 times), 1.8 km SW (101 times), 1.5 km W (two
times), and 1.5 km NW (one time). Avalanches of material that descended the
W flank originated from lava emplaced in 1992 and 1998, and material that
descended the NW flank is from 1948 lava. According to the Darwin VAAC ash
plumes rose to 3 km (10,000 ft) a.s.l. on 24 July and drifted WSW. The
Alert Level remained at 3 (on a scale of 1-4), and the public was 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.

Sources: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi
(BPPTKG) https://urldefense.com/v3/__http://www.merapi.bgl.esdm.go.id/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtT5vxmQgk$ 
<https://urldefense.com/v3/__http://www.merapi.bgl.esdm.go.id/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjF3jWcbw$>
;

Darwin Volcanic Ash Advisory Centre (VAAC)
https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTzw4h4XU$ 
<https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfj_lXE1qE$>

Nyiragongo  | DR Congo  | 1.52Â°S, 29.25Â°E  | Summit elev. 3470 m

According to a news article a collapse in Nyiragongoâ??s main crater on 24
July caused white-colored ash to fall in Goma. The ashfall caused no
notable damage, though there were health concerns related to water quality.
The director of Volcanological Observatory of Goma (OVG) noted that the
collapse was not due to eruptive activity.

Geologic Summary. One of Africa's most notable volcanoes, Nyiragongo
contained a lava lake in its deep summit crater that was active for half a
century before draining catastrophically through its outer flanks in 1977.
The steep slopes of a stratovolcano contrast to the low profile of its
neighboring shield volcano, Nyamuragira. Benches in the steep-walled,
1.2-km-wide summit crater mark levels of former lava lakes, which have been
observed since the late-19th century. Two older stratovolcanoes, Baruta and
Shaheru, are partially overlapped by Nyiragongo on the north and south.
About 100 parasitic cones are located primarily along radial fissures south
of Shaheru, east of the summit, and along a NE-SW zone extending as far as
Lake Kivu. Many cones are buried by voluminous lava flows that extend long
distances down the flanks, which is characterized by the eruption of
foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities,
as did lava flows that inundated portions of the major city of Goma in
January 2002.

Source: Agence France-Presse (AFP)
https://urldefense.com/v3/__https://fr.africanews.com/2021/07/26/rdc-le-nyiragongo-crache-des-cendres-sans-eruption/?utm_medium=AfricanewsFR__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTDQ-2yl0$ 
<https://urldefense.com/v3/__https://fr.africanews.com/2021/07/26/rdc-le-nyiragongo-crache-des-cendres-sans-eruption/?utm_medium=AfricanewsFR__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjHpAMKTM$>

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

Instituto GeofÃsico del PerÃº (IGP) reported a daily average of 58
explosions at Sabancaya during 19-25 July. Gas-and-ash plumes rose as high
as 2.3 km above the summit and drifted S, SE, E, and NE. Nine thermal
anomalies originating from the lava dome in the summit crater were
identified in satellite data. Minor inflation continued to be detected near
Hualca Hualca (4 km N). 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) https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtT7Phhl3I$ 
<https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjAouBFhw$>

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 16-23 July. 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!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTGO9dYms$ 
<https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjbi6TwXM$>

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

PVMBG reported that white-and-gray plumes rose 100-300 m above Sinabung
during 20-21 July and drifted N, NE, E, and SE. During 21-27 July white
plumes rose as high as 400 m and drifted NE, E, and SE. At 1320 on 28 July
an eruption produced an ash plume that rose 4.5 km above the summit and
drifted E and S; the event lasted for about 12 and a half minutes. The
Aviation Color Code was raised to Red. 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. 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTJMLeD8w$ 
<https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjBnzuzyk$>

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

On 27 July the University of the West Indies Seismic Research Centre
(UWI-SRC) reported that seismicity at SoufriÃ¨re St. Vincent (often simply
referred to as â??La Soufriereâ??) had remained low since the last episode of
ash venting on 22 April. A few small daily earthquakes were recorded.
Steam-and-gas plumes rose from some areas inside the crater and thermal
anomalies persisted. The Alert Level remained at Orange.

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: University of the West Indies Seismic Research Centre (UWI-SRC)
https://urldefense.com/v3/__http://www.uwiseismic.com/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTnmC8k8g$ 
<https://urldefense.com/v3/__http://www.uwiseismic.com/__;!!IKRxdwAv5BmarQ!NjJTLpqLW3YmwkGO08fDkY0YlNGBaP6VUEoop1AEEVlgNB9woxJotvfjz8D6xdo$>

3-3-3-3-3-3-3-3-3-3-3-3-3

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PSU - https://urldefense.com/v3/__http://pdx.edu/__;!!IKRxdwAv5BmarQ!L5Da78VNDxEJ1Lg2PEKAoPCTp-JiftEdMZiMANFlj4TYJEv91bo1iJtTpMcETA0$ 

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End of Volcano Digest - 26 Jul 2021 to 28 Jul 2021 (#2021-70)
*************************************************************