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1. Smithsonian / USGS Weekly Volcanic Activity Report 26 September-2 October
2018
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Date: Thu, 4 Oct 2018 11:47:06 -0700
From: Sean Peters <speter24@xxxxxxx>
Subject: Smithsonian / USGS Weekly Volcanic Activity Report 26 September-2 October 2018
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From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: https://volcano.si.edu/reports_weekly.cfm
New Activity/Unrest: Kerinci, Indonesia | Langila, New Britain (Papua New
Guinea) | Piton de la Fournaise, Reunion Island (France) | Sarychev Peak,
Matua Island (Russia) | Semisopochnoi, United States | Soputan, Sulawesi
(Indonesia) | Veniaminof, United States
Ongoing Activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) |
Ebeko, Paramushir Island (Russia) | Etna, Sicily (Italy) | Ibu, Halmahera
(Indonesia) | Kadovar, Papua New Guinea | Karymsky, Eastern Kamchatka
(Russia) | Kilauea, Hawaiian Islands (USA) | Krakatau, Indonesia |
Manam, Papua New Guinea | Merapi, Central Java (Indonesia) | Sabancaya,
Peru | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica
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, notices of
volcanic activity posted on these pages 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 on various volcanoes are published monthly in the Bulletin of the
Global Volcanism Network.
Note: 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
Kerinci | Indonesia | 1.697°S, 101.264°E | Summit elev. 3800 m
Based on satellite and wind model data, the Darwin VAAC reported that
during 28-30 September and 2 October ash plumes from Kerinci rose to an
altitude of 4.3 km (14,000 ft) a.s.l. and drifted SW and W.
Geologic Summary. The 3800-m-high Gunung Kerinci in central Sumatra forms
Indonesia's highest volcano and is one of the most active in Sumatra.
Kerinci is capped by an unvegetated young summit cone that was constructed
NE of an older crater remnant. The volcano contains a deep 600-m-wide
summit crater often partially filled by a small crater lake that lies on
the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13
x 25 km wide volcano towers 2400-3300 m above surrounding plains and is
elongated in a N-S direction. The frequently active Gunung Kerinci has been
the source of numerous moderate explosive eruptions since its first
recorded eruption in 1838.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml
Langila | New Britain (Papua New Guinea) | 5.525°S, 148.42°E | Summit
elev. 1330 m
Based on analyses of satellite imagery and model data, the Darwin VAAC
reported that on 29 September an ash plume from Langila rose to an altitude
of 2.4 km (8,000 ft) a.s.l. and drifted NE.
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 eastern flank of the extinct Talawe volcano. Talawe is
the highest volcano in the Cape Gloucester area of NW New Britain. A
rectangular, 2.5-km-long crater is breached widely to the SE; Langila
volcano was constructed NE of the breached crater of Talawe. An extensive
lava field reaches the coast on the north 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 of Langila. 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
Piton de la Fournaise | Reunion Island (France) | 21.244°S, 55.708°E |
Summit elev. 2632 m
OVPF reported that the eruption at Piton de la Fournaise continued during
26 September-2 October, and tremor levels were stable. The cone continued
to grow; one vent was active and ejected spatter. Lava flows were mostly
confined to lava tubes, emerging 150-200 m downstream, S of the cone.
During a field inspection on 29 September OVPF staff observed a small lava
flow at the foot of the cone.
Geologic Summary. The massive Piton de la Fournaise basaltic shield volcano
on the French island of Réunion in the western Indian Ocean is one of the
world's most active volcanoes. Much of its more than 530,000-year history
overlapped with eruptions of the deeply dissected Piton des Neiges shield
volcano to the NW. Three calderas formed at about 250,000, 65,000, and less
than 5000 years ago by progressive eastward slumping of the volcano.
Numerous pyroclastic cones dot the floor of the calderas and their outer
flanks. Most historical eruptions have originated from the summit and
flanks of Dolomieu, a 400-m-high lava shield that has grown within the
youngest caldera, which is 8 km wide and breached to below sea level on the
eastern side. More than 150 eruptions, most of which have produced fluid
basaltic lava flows, have occurred since the 17th century. Only six
eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from
fissures on the outer flanks of the caldera. The Piton de la Fournaise
Volcano Observatory, one of several operated by the Institut de Physique du
Globe de Paris, monitors this very active volcano.
Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)
http://www.ipgp.fr/
Sarychev Peak | Matua Island (Russia) | 48.092°N, 153.2°E | Summit elev.
1496 m
KVERT reported that a thermal anomaly over Sarychev Peak was visible in
satellite images on 22 September. The Aviation Color Code remained at
Orange.
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
Semisopochnoi | United States | 51.93°N, 179.58°E | Summit elev. 1221 m
AVO reported that during 19-25 September seismicity at Semisopochnoi
remained elevated, alternating between periods of continuous and
intermittent bursts of tremor. Tremor bursts at 1319 on 21 September and at
1034 on 22 September produced airwaves detected on a regional infrasound
array on Adak Island; no ash emissions were identified above the low cloud
deck in satellite data, and the infrasound detections likely reflected an
atmospheric change instead of volcanic activity. The Aviation Color Code
(ACC) remained at Yellow and Volcano Alert Level (VAL) remained at Advisory.
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 1221-m-high Anvil Peak, a
double-peaked late-Pleistocene cone that forms much of the island's
northern part. The three-peaked 774-m-high Mount Cerberus volcano was
constructed during the Holocene within the caldera. Each of the peaks
contains a summit crater; lava flows on the northern flank of Cerberus
appear younger than those on the southern side. Other post-caldera
volcanoes include the symmetrical 855-m-high 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 historical eruptions have
originated from Cerberus, although Coats (1950) considered that both
Sugarloaf and Lakeshore Cone within the caldera could have been active
during historical time.
Source: US Geological Survey Alaska Volcano Observatory (AVO)
https://avo.alaska.edu/
Soputan | Sulawesi (Indonesia) | 1.112°N, 124.737°E | Summit elev. 1785 m
PVMBG reported that increased seismicity at Soputan was notable on 2
October, characterized by an increased number of signals indicating
emissions and avalanches (which began in September and mid-July,
respectively), increased RSAM values, and a higher number of volcanic
earthquakes (since September). Data from a thermal camera showed increased
summit temperatures, indicating the presence of lava. The Alert Level was
increased to 3 (on a scale of 1-4) on 3 October; residents and tourists
were advised not to approach the craters within a radius of 4 km, with an
additional expansion to 6.5 km in WSW direction due to increased risk from
a breach in the crater rim. An eruption commenced at 0847 on 3 October,
producing a dense ash plume that rose 4 km above the summit and drifted W
and NW. Based on seismic data the event lasted six minutes. Events at 1044,
1112, and 1152 produced ash plumes that rose 2 km, 2.5 km , and 5 km above
the crater rim, respectively. A thermal anomaly identified in satellite
data significantly increased, and incandescent ejecta at the summit was
clearly observed by residents. Avalanches of material traveled 2.5 km down
the NE flank.
Geologic Summary. The Soputan stratovolcano on the southern rim of the
Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of
Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano
rises to 1784 m and is located SW of Riendengan-Sempu, which some workers
have included with Soputan and Manimporok (3.5 km ESE) as a volcanic
complex. It was constructed at the southern end of a SSW-NNE trending line
of vents. During historical time the locus of eruptions has included both
the summit crater and Aeseput, a prominent NE-flank vent that formed in
1906 and was the source of intermittent major lava flows until 1924.
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/
Veniaminof | United States | 56.17°N, 159.38°W | Summit elev. 2507 m
AVO reported that the eruption at Veniaminof continued during 26
September-2 October, as evidenced by nighttime incandescence recorded by
the FAA web camera in Perryville (35 km S), elevated surface temperatures
in thermal satellite data, and elevated tremor levels. A gas plume was
occasionally visible during clear daytime conditions. On 26 September lava
fountains, visible in webcam images, rose from a second vent located 75 m N
of the vent producing lava flows. Minor ash emissions associated with lava
fountaining possibly rose as high as km (15,000 ft) a.s.l. and quickly
dispersed. The lava flow had traveled 1 km down the S flank of the summit
cone by 1 October. The Aviation Color Code remained at Orange and the
Volcano Alert Level remained at Watch.
Geologic Summary. Massive Veniaminof volcano, one of the highest and
largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled,
8 x 11 km, glacier-filled caldera that formed around 3700 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/
Ongoing Activity
Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m
JMA reported that occasional, very small, events at Minamidake crater (at
Aira Caldera’s Sakurajima volcano) during 25 September-1 October generated
plumes that rose 400 m above the crater rim. 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) | 1.693°N, 127.894°E | Summit elev. 1229 m
Based on satellite data, wind model data, and notices from PVMBG, the
Darwin VAAC reported that during 26 September-2 October ash plumes from
Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted
NW, N, NE, and E.
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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml
Ebeko | Paramushir Island (Russia) | 50.686°N, 156.014°E | Summit elev.
1103 m
Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of
Ebeko, observed explosions during 21-28 September that sent ash plumes to 4
km (13,100 ft) a.s.l. Satellite images showed a thermal anomaly over the
volcano on 23 and 27 September, and ash plumes drifting as far as 68 km SE
during 23-24 and 26-27 September. 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) | 37.748°N, 14.999°E | Summit elev. 3295 m
INGV reported that during 24-30 September activity at Etna was
characterized by gas emissions at the summit craters, with periodic
Strombolian activity from vents in Bocca Nuova, Northeast Crater (NEC), and
New Southeast Crater (NSEC). Strombolian activity at the N vent in Bocca
Nuova (BN-1) ejected incandescent material almost as high as the W crater
rim. No eruptive activity was observed at BN-2, though it produced
explosions deep in the crater. A new high-temperature vent producing gas
emissions was noted on 1 October in the same place a fumarole had been
observed the previous week. Ash emissions from NSEC were sometimes
accompanied by ejected incandescent material. Gas emissions increased at
Voragine Crater from a vent that formed on 7 August 2016 on the E rim of
the crater. NEC produced frequent brown-gray ash emissions, and ejected
blocks and bombs, from a vent located in the W part of the crater floor.
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/
Ibu | Halmahera (Indonesia) | 1.488°N, 127.63°E | Summit elev. 1325 m
Based on satellite images and wind model data, the Darwin VAAC reported
that on 28 and 30 September ash plumes from Ibu rose to 1.8 km (6,000 ft)
a.s.l. and drifted NE and N.
Geologic Summary. The truncated summit of Gunung Ibu stratovolcano along
the NW coast of Halmahera Island has large nested summit craters. The inner
crater, 1 km wide and 400 m deep, contained several small crater lakes
through much of historical time. The outer crater, 1.2 km wide, is breached
on the north side, creating a steep-walled valley. A large parasitic cone
is located ENE of the summit. A smaller one to the WSW has fed a lava flow
down the W flank. A group of maars is located below the N and W flanks.
Only a few eruptions have been recorded in historical time, the first a
small explosive eruption from the summit crater in 1911. An eruption
producing a lava dome that eventually covered much of the floor of the
inner summit crater began in December 1998.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml
Kadovar | Papua New Guinea | 3.608°S, 144.588°E | Summit elev. 365 m
An ash plume from Kadovar was visible in satellite images on 28 September
drifting SE at an altitude of 2.1 km (7,000 ft) a.s.l. On 1 October an ash
plume rose to 2.7 km (9,000 ft) a.s.l. and drifted W.
Geologic Summary. The 2-km-wide island of Kadovar is the emergent summit of
a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the
Schouten Islands, and lies off the coast of New Guinea, about 25 km N of
the mouth of the Sepik River. The village of Gewai is perched on the crater
rim. A 365-m-high lava dome forming the high point of the andesitic volcano
fills an arcuate landslide scarp that is open to the south, and submarine
debris-avalanche deposits occur in that direction. Thick lava flows with
columnar jointing forms low cliffs along the coast. The youthful island
lacks fringing or offshore reefs. No certain historical eruptions are
known; the latest activity was a period of heightened thermal phenomena in
1976.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml
Karymsky | Eastern Kamchatka (Russia) | 54.049°N, 159.443°E | Summit
elev. 1513 m
KVERT reported that a thermal anomaly over Karymsky was identified in
satellite images during 22-24 September, and ash plumes were visible
drifting 365 km E during 22-23 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)
http://www.kscnet.ru/ivs/kvert/index_eng.php
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev.
1222 m
HVO reported no significant incandescence from a collapse pit in the
central part of Kilauea’s Fissure 8 cone during 26 September-2 October,
though a small amount of fuming was visible during the day. Seismicity and
ground deformation remain low at the summit, and small aftershocks from the
M 6.9 earthquake in early May were located along faults on the south flank.
Sulfur dioxide emissions from the summit and the LERZ were low. On 1
October a rockfall at Pu'u 'O'o produced a small ash plume. The Volcano
Alert Level remained at Watch and the Aviation Color Code remained at
Orange.
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/
Krakatau | Indonesia | 6.102°S, 105.423°E | Summit elev. 813 m
Based on satellite data, wind model data, and notices from PVMBG, the
Darwin VAAC reported that during 25 September-2 October ash plumes from
Anak Krakatau rose to altitudes of 1.2-2.1 km (4,000-7,000 ft) a.s.l. and
drifted W, WSW, and SW. The Alert Level remained at 2 (on a scale of 1-4);
residents and visitors were warned not to approach the volcano within 2 km
of the crater.
Geologic Summary. The renowned volcano Krakatau (frequently misstated as
Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of
the ancestral Krakatau edifice, perhaps in 416 CE, formed a 7-km-wide
caldera. Remnants of this ancestral volcano are preserved in Verlaten and
Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were
formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse
during the catastrophic 1883 eruption destroyed Danan and Perbuwatan
volcanoes, and left only a remnant of Rakata volcano. This eruption, the
2nd largest in Indonesia during historical time, caused more than 36,000
fatalities, most as a result of devastating tsunamis that swept the
adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km
across the Sunda Strait and reached the Sumatra coast. After a quiescence
of less than a half century, the post-collapse cone of Anak Krakatau (Child
of Krakatau) was constructed within the 1883 caldera at a point between the
former cones of Danan and Perbuwatan. Anak Krakatau has been the site of
frequent eruptions since 1927.
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
Manam | Papua New Guinea | 4.08°S, 145.037°E | Summit elev. 1807 m
RVO reported that pale-gray-to-brown ash plumes rose from Manam’s Southern
Crater during 20 September-1 October. Activity was most intense on 24
September, with an increased amount of ash emissions, and occasional weak
roaring and rumbling noises. Based on seismic data an eruption at Main
Crater began during 0100-0130 on 1 October, peaked around 0200, and ended
at 1200 (though a sharp decline was recorded at 1215). Ash plumes rose at
least several hundred meters above the crater rim, though darkness obscured
visual observations. Islanders described loud roaring and rumbling noises,
as well as loud banging noises. Residents of Tabele on the SW side of the
island observed bright summit incandescence, which was also visible from
the Bogia Government Station on the mainland (22 km SSW). Scoria and minor
amounts of ash fell in Jogari and villages to the N.
Geologic Summary. The 10-km-wide island of Manam, lying 13 km off the
northern coast of mainland Papua New Guinea, is one of the country's most
active volcanoes. Four large radial valleys extend from the unvegetated
summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its
lower flanks. These "avalanche valleys" channel lava flows and pyroclastic
avalanches that have sometimes reached the coast. Five small satellitic
centers are located near the island's shoreline on the northern, southern,
and western sides. Two summit craters are present; both are active,
although most historical eruptions have originated from the southern
crater, concentrating eruptive products during much of the past century
into the SE valley. Frequent historical eruptions, typically of
mild-to-moderate scale, have been recorded since 1616. Occasional larger
eruptions have produced pyroclastic flows and lava flows that reached
flat-lying coastal areas and entered the sea, sometimes impacting populated
areas.
Source: Rabaul Volcano Observatory (RVO)
Merapi | Central Java (Indonesia) | 7.54°S, 110.446°E | Summit elev.
2910 m
PVMBG reported that during 21-27 September the new lava dome in Merapi’s
summit crater continued to slowly grow. By 27 September the volume of the
lava dome was an estimated 129,000 cubic meters, and the growth rate was
1,000 cubic meters per day (slower than the previous week). White emissions
of variable density rose a maximum of 450 m above the summit. The Alert
Level remained at 2 (on a scale of 1-4), and resident were warned to remain
outside of the 3-km exclusion zone.
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 2000 years ago, leaving a large arcuate scarp cutting the
eroded older Batulawang volcano. Subsequently growth of the steep-sided
Young Merapi edifice, its upper part unvegetated due to frequent eruptive
activity, began SW of the earlier collapse scarp. Pyroclastic flows and
lahars accompanying growth and collapse of the steep-sided active summit
lava dome have devastated cultivated lands on the western-to-southern
flanks and caused many fatalities during historical time.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known
as CVGHM) http://vsi.esdm.go.id/
Sabancaya | Peru | 15.787°S, 71.857°W | Summit elev. 5960 m
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio
Vulcanológico del INGEMMET (OVI) reported that explosions at Sabancaya
averaged 21 per day during 24-30 September. Hybrid earthquakes were
infrequent and of low magnitude. Gas-and-ash plumes rose as high as 3.7 km
above the crater rim and drifted 50 km E, SE, and SW. The MIROVA system
detected six thermal anomalies, and on 29 September the sulfur dioxide gas
flux was high at 3,250 tons/day. The report noted that the public should
not approach the crater within 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.
Sources: Instituto Geológico Minero y Metalúrgico (INGEMMET)
http://www.ingemmet.gob.pe/;
Instituto Geofísico del Perú (IGP) http://www.igp.gob.pe/
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit
elev. 3283 m
KVERT reported that a thermal anomaly over Sheveluch was identified in
satellite data during 20, 23, and 27 September; weather clouds prevented
views on the other days during 21-28 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)
http://www.kscnet.ru/ivs/kvert/index_eng.php
Turrialba | Costa Rica | 10.025°N, 83.767°W | Summit elev. 3340 m
OVSICORI-UNA reported that at 0915 on 27 September an event at Turrialba
produced a passive ash plume that rose 200 m above the crater and drifted
NW. During 30 September-1 October ash emissions rose as high as 500 m above
the crater rim and drifted NW and NE.
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 Irazú 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) http://www.ovsicori.una.ac.cr/
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End of Volcano Digest - 1 Oct 2018 to 4 Oct 2018 (#2018-102)
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