The Weekly Volcanic Activity Report: October 19 – 25, 2022

the weekly volcanic activity report

New activity/unrest was reported for 9 volcanoes from October 19 to 25, 2022. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Alaid, Kuril Islands (Russia) | Bezymianny, Central Kamchatka (Russia) | Cotopaxi, Ecuador | Kerinci, Central Sumatra | Langila, New Britain (Papua New Guinea) | Mauna Loa, Hawaiian Islands (USA) | Popocatepetl, Mexico | Taal, Luzon (Philippines) | Villarrica, Central Chile.

Ongoing activity: Aira, Kyushu (Japan) | Ebeko, Paramushir Island (Russia) | Great Sitkin, Andreanof Islands (USA) | Home Reef, Tonga Ridge | Kilauea, Hawaiian Islands (USA) | Krakatau, Sunda Strait | Lewotolok, Lembata Island | Merapi, Central Java | Pavlof, Alaska Peninsula, Alaska | Reventador, Ecuador | Sangay, Ecuador | Semeru, Eastern Java | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Whakaari/White Island, North Island (New Zealand).

New activity/unrest

Alaid, Kuril Islands (Russia)

50.861°N, 155.565°E | Summit elev. 2285 m

KVERT reported that the eruption at Alaid was ongoing during 14-20 October. An intense thermal anomaly was identified in satellite images during 13-16 and 20 October; weather clouds obscured views on the other days. Explosive activity during 13-16 October generated ash plumes that rose as high as 6.5 km (21,300 ft) a.s.l. and drifted 360 km E and SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago. Numerous pyroclastic cones dot the lower flanks of this basaltic to basaltic-andesite volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.

Bezymianny, Central Kamchatka (Russia)

55.972°N, 160.595°E | Summit elev. 2882 m

Activity at Bezymianny increased during 22-23 October characterized by incandescence at the summit, sometimes strong fumarolic activity, and an increasing temperature of a thermal anomaly identified in satellite images. KVERT raised the Aviation Color Code to Orange (the second highest level on a four-color scale). A strong explosive phase commenced and by 2340 local time on 23 October satellite images showed ash plumes rising to 10 km (32,800 ft) a.s.l. and drifting 10 km ENE. The Aviation Color Code was raised to Red. By 1005 local time on 24 October the phase was over, and the Aviation Color Code was lowered to Orange. Satellite images showed gas-and-steam plumes drifting NE and an intense thermal anomaly. The ash plumes from the day before had drifted as far as 1,915 km NE. At 2028 local time on 25 October KVERT lowered the Aviation Color Code to Yellow and noted that the intense thermal anomaly persisted. Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Cotopaxi, Ecuador

0.677°S, 78.436°W | Summit elev. 5911 m

IG reported minor eruptive activity at Cotopaxi. A low-amplitude tremor signal recorded by the seismic network from 1950 on 21 October to 0040 on 22 October was associated with gas-and-ash emissions. The emissions were not visible due to darkness and weather conditions, but minor ashfall and a sulfur odor was reported by mountaineers in the Refugio José Rivas, 2 km N of the summit crater; the mountaineers evacuated. The Washington VAAC reported that during 2150-2200 on 21 October ash plumes rose to 7.6-8.5 (25,000-28,000 ft) a.s.l. and drifted NE based on information from IG and the Guayaquil MWO, satellite images, and webcam views. The ash had dissipated by 0410 on 22 October. A second ash plume was identified in webcam and satellite images rising to 7 km (23,000 ft) a.s.l. and drifting W at 0700 on 22 October. Ash was no longer visible by 1250. IG noted that following the end of the tremor signal seismicity declined and plumes of gas-and-steam rose as high as 1 km above the summit and drifted W. Based on the reports from IG the Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) raised the Alert Level to Yellow (the second lowest level on a four-color scale) on 22 October.

Weather conditions at the volcano improved on 23 October and a layer of dark gray ash on the volcano, deposited the previous two days, became visible. Based on seismic data and media reports, small secondary lahars generated from the melted glacier beneath the ash deposit, were recorded during 1115-1300 and traveled short distances down the flanks. Weather clouds frequently prevented views of the volcano during 24-25 October, though steam emissions rising 200 m above the summit and drifting W were visible during a break in the cloud cover the morning of 25 October.

Geological summary: The symmetrical, glacier-covered, Cotopaxi stratovolcano is Ecuador’s most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. Smaller eruptions have been frequent since that time.

Kerinci, Central Sumatra

1.697°S, 101.264°E | Summit elev. 3800 m

PVMBG reported that white-and-brown or gray plumes from Kerinci rose as high as 750 m above the summit and drifted NE and NW during 18-24 October. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale). The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-km exclusion zone.

Geological summary: Gunung Kerinci in central Sumatra forms Indonesia’s highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is 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. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Langila, New Britain (Papua New Guinea)

5.525°S, 148.42°E | Summit elev. 1330 m

The Darwin VAAC reported that on 20 October an ash plume from Langila rose 2.7 km (9,000 ft) a.s.l. and drifted NW. The plume had dissipated within 5 hours.

Geological 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.

Mauna Loa, Hawaiian Islands (USA)

19.475°N, 155.608°W | Summit elev. 4170 m

HVO reported continuing unrest at Mauna Loa during 19-25 October. The seismic network detected 10-46 daily small-magnitude (below M 3) earthquakes 3-5 km beneath Mokua’weoweo caldera and 6-8 km beneath the upper NW flank of Mauna Loa. Data from Global Positioning System (GPS) instruments at the summit and flanks showed continuing inflation, though data from tiltmeters at the summit did not show significant surface deformation over the past week. A M 3.1 earthquake was recorded at 2035 on 23 October at a depth of 4 km beneath Mokua’weoweo caldera. The Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale) and the Aviation Color Code remained at Yellow (the second lowest level on a four-color scale).

Geological summary: Massive Mauna Loa shield volcano rises almost 9 km above the sea floor to form the world’s largest active volcano. Flank eruptions are predominately from the lengthy NE and SW rift zones, and the summit is cut by the Mokuaweoweo caldera, which sits within an older and larger 6 x 8 km caldera. Two of the youngest large debris avalanches documented in Hawaii traveled nearly 100 km from Mauna Loa; the second of the Alika avalanches was emplaced about 105,000 years ago (Moore et al. 1989). Almost 90% of the surface of the basaltic shield volcano is covered by lavas less than 4000 years old (Lockwood and Lipman, 1987). During a 750-year eruptive period beginning about 1500 years ago, a series of voluminous overflows from a summit lava lake covered about one fourth of the volcano’s surface. The ensuing 750-year period, from shortly after the formation of Mokuaweoweo caldera until the present, saw an additional quarter of the volcano covered with lava flows predominately from summit and NW rift zone vents.

Popocatepetl, Mexico

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

CENAPRED reported that there were 27-62 steam-and-gas emissions, sometimes containing minor amounts of ash, rising from Popocatépetl each day during 19-25 October. Weather clouds often prevented visual observations of activity. The seismic network recorded daily periods of tremor lasting from 16 minutes to 10 hours and 35 minutes. One or two daily volcano-tectonic earthquakes were recorded. During 20-23 October daily periods of low-amplitude, high-frequency events varied between two hours and 19 minutes to five hours, and periods of harmonic tremor lasted from 11 minutes to five hours and 35 minutes. A small explosion was recorded at 0039 on 25 October. According to a news article a small new lava dome, about 60 m in diameter, had been growing on the crater floor since 7 October. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale).

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

Taal, Luzon (Philippines)

14.002°N, 120.993°E | Summit elev. 311 m

PHIVOLCS reported continuing unrest at Taal during 18-25 October. Daily white steam emissions rose as high as 3 km above the lake and drifted NE, NW, and SW. Upwelling gasses and hot fluids in the lake were periodically visible. Sulfur dioxide emissions averaged 6,702 tonnes per day on 20 October. The seismic network recorded 0-6 daily volcanic earthquakes and a few periods of volcanic tremor during 20-23 October. Webcam images showed increased activity during 21-22 October with 29 small phreatomagmatic bursts from a vent on the NE part of the lake, each lasting 1-5 minutes long. Some of the events produced 200-m-tall steam-rich plumes and very, short, dark ash plumes that immediately collapsed back into the water. Not all events generated detectable signals in the seismic and infrasound records. Ash plumes rose to 600 m (2,000 ft) a.s.l. on 21 October and drifted W according to the Tokyo VAAC. Two small phreatomagmatic bursts, each lasting 6-7 minutes long were recorded during 22-23 October. Sulfur dioxide emissions averaged 1,403 tonnes per day on 24 October. Ground deformation measurements continued to show slight inflation in the western half of the caldera and deflation in the eastern half. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).

Geological 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 observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

Villarrica, Central Chile

39.42°S, 71.93°W | Summit elev. 2847 m

On 25 October SERNAGEOMIN reported that activity at Villarrica had been gradually increasing. Both the number and amplitude of long-period earthquakes increased during the month, and further increased the last week. Continuous tremor increased slightly. Webcams showed persistent gas emissions rising 460 m above the crater rim, and ash plumes drifting downwind on 2 and 23 October. Sulfur dioxide emissions averaged 535 (plus or minus 115) tonnes per day, peaking at 1,273 tonnes per day on 13 October. These values were within normal levels and were lower than in September. Crater incandescence increased in both frequency and intensity, consistent with reports from POVI and other collaborators, and likely indicated periodic Strombolian activity. On 14 October satellite images showed the active lava lake covering an area of 36 square meters in the E part of the crater floor. A partial collapse (less than 300 square meters) of the inner SSW crater rim was also evident.

POVI reported that lava fountaining and Strombolian explosions were visible in webcam images at 1917 on 18 October. The most intense thermal anomaly over the crater since September 2019 was detected in satellite images on 23 October, and crater incandescence was visible in webcam images. That same day tourists described seeing splashes of lava ejected from a depth of 80 m and hearing loud degassing sounds. Deposits of ejected tephra were visible around the crater rim and on the upper flanks on 24 October, and intense crater incandescence was visible in images on 25 October. The Alert Level remained at Green, the lowest level on a four-color scale.

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

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E | Summit elev. 1117 m

JMA reported that four eruptive events and seven explosions at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) were recorded during 17-24 October. Volcanic plumes rose as high as 2.4 km above the crater rim and large blocks were ejected as far as 1.3 km from the vent. Incandescence at the crater was visible nightly. The Alert Level remained at 3 (on a 5-level scale), and residents were warned to stay 2 km away from the crater.

Geological 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.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E | Summit elev. 1103 m

KVERT reported that moderate activity at Ebeko was ongoing. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions during 13-16 and 18 October generated ash plumes that rose to 4 km (13,100 ft) a.s.l. and drifted SE. Ashfall was reported in Severo-Kurilsk on 13 October and a thermal anomaly was identified in satellite images during 15-16 October. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological 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.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W | Summit elev. 1740 m

AVO reported that slow lava effusion continued at Great Sitkin during 19-25 October along with low levels of seismicity. Slightly elevated surface temperatures were identified in satellite images during 21-22 October. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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.

Home Reef, Tonga Ridge

18.992°S, 174.775°W | Summit elev. -10 m

The Tonga Geological Services reported that the eruption at Home Reef that began on 10 September was over. Satellite-based measurements showed that the island had not changed in size since 28 September, remaining at 268 m N-S, 283 m E-W, and 15-18 m high. A thermal anomaly was last observed on 17 October. On 22 October the Aviation Color Code was lowered to Green (the lowest level on a four-color scale) and the warning to mariners was lifted, though the public was prohibited from landing on the island.

Geological summary: Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, copious amounts of floating pumice, and an ephemeral island 500 x 1500 m wide, with cliffs 30-50 m high that enclosed a water-filled crater. Another island-forming eruption in 2006 produced widespread dacitic pumice rafts that reached as far as Australia.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W | Summit elev. 1222 m

HVO reported that lava continued to effuse from a vent in the lower W wall of Kilauea’s Halema`uma`u Crater during 19-25 October entering the lava lake and flowing onto the crater floor. The active part of the lake remained at a steady level all week. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Krakatau, Sunda Strait

6.102°S, 105.423°E | Summit elev. 155 m

PVMBG reported that multiple ash plumes were visible rising from Anak Krakatau during 24-25 October. Webcam views showed that at 1757 on 24 October a dense black ash plume rose about 150 m above the summit, and at 2111 a dense gray-to-black ash plume rose 150 m and drifted E. Dense gray-to-black ash plumes were visible on 25 October at 0727, 0956, and 1711 rising 150-200 m above the summit and drifting NE. An eruptive event was recorded at 1845 by the seismic network; a webcam photo showed incandescent material being ejected above the crater rim. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away from the crater.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that 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, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of 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.

Lewotolok, Lembata Island

8.274°S, 123.508°E | Summit elev. 1431 m

PVMBG reported that the eruption at Lewotolok continued during 18-25 October. Daily white emissions rose as high as 600 m above the summit and drifted in multiple directions. During 22-23 October white-and-gray plumes rose as high as 500 m and drifted W. 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 and 4 km away from the crater on the SE flank.

Geological 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.

Merapi, Central Java

7.54°S, 110.446°E | Summit elev. 2910 m

BPPTKG reported that the eruption at Merapi continued during 14-20 October and seismicity remained at high levels. The SW lava dome produced as many as five minor lava avalanches that traveled up to 1.8 km down the Bebeng drainage on the SW flank. No significant morphological changes to the central and SW lava domes were evident in drone photographs. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit based on location.

Geological 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.

Pavlof, Alaska Peninsula, Alaska

55.417°N, 161.894°W | Summit elev. 2493 m

AVO reported that a minor eruption at a vent on Pavlof’s upper E flank was ongoing during 18-25 October and nearly continuous seismic tremor was recorded. Multiple daily explosions were detected in seismic and infrasound data. Sequences of small explosions during 18-20 October were accompanied by incandescence near the summit in webcam views. Webcam images from the afternoon of 20 October showed a new dark flow of lava and debris extending about a third of the way down the E flank. Elevated surface temperatures were identified in satellite images on almost all days. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Reventador, Ecuador

0.077°S, 77.656°W | Summit elev. 3562 m

IG described the ongoing eruption at Reventador as moderate during 18-25 October. Daily seismicity was characterized by 9-45 explosions, 2-67 long-period earthquakes, 4-25 signals that indicated emissions, and during 20-25 October there were 2-6 periods of harmonic tremor. Gas, steam, and ash plumes, observed almost daily with webcams or reported by the Washington VAAC, rose as high as 1.3 km above the summit and drifted SW, W, and NW. Weather clouds sometimes prevented visual observations. Crater incandescence was occasionally visible and the lava flow on the NE flank was active. Sulfur dioxide emissions averaged 52-83 tons per day during 19-23 October.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Sangay, Ecuador

2.005°S, 78.341°W | Summit elev. 5286 m

IG reported a high level of activity at Sangay during 18-25 October. Daily seismic counts ranges were 230-734 explosions, 39-86 tremor events indicating emissions, and 1-2 lahar events; 10-23 long-period events were recorded during 22-23 October. Daily ash-and-gas plumes were identified in IG webcam images and/or visible in satellite images according to the Washington VAAC. Plumes generally rose as high as 2.1 km above the volcano and drifted NW, W, and SW. Almost daily thermal anomalies were identified in satellite images, though weather clouds sometimes prevented views. Sulfur dioxide emissions averaged 363-1,716 tons per day during 18-25 October. Incandescence at the summit and from a new lava flow on the SE flank was visible during 18-19 October; incandescence from lava-flow activity continued to be periodically visible the rest of the week. Servicio Nacional de Gestión de Riesgos y Emergencias lowered the Alert Level to Yellow (on a four-color scale) during 20-21 October.

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador’s volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Semeru, Eastern Java

8.108°S, 112.922°E | Summit elev. 3657 m

PVMBG reported that the eruption at Semeru continued during 19-24 October. Eruptive events at 0454 and 0633 on 20 October, 0451 on 21 October, 0634 on 23 October, and 0554 on 24 October produced ash plumes that rose 500 m above the summit and drifted mainly S and W. The Alert Level remained at 3 (on a scale of 1-4). The public was warned to stay at least 5 km away from the summit, and 500 m from Kobokan drainages within 17 km of the summit, along with other drainages originating on Semeru, including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards.

Geological 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.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E | Summit elev. 3283 m

KVERT reported that the ongoing eruption at Sheveluch was characterized by explosions, hot avalanches, and lava-dome extrusion during 14-20 October. A daily thermal anomaly was identified in satellite images. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. 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 occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. 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.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E | Summit elev. 796 m

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued during 17-24 October. Crater incandescence was visible nightly. A total of 119 explosions during 17-21 October produced eruption plumes that rose as high as 2 km above the crater rim and ejected blocks as far as 800 m from the vent. Occasional rumbling noises and ashfall were reported in Toshima village (3.5 km SSW). Only one explosion was reported during 21-24 October. Plumes rose as high as 1.5 km and blocks were ejected as far as 200 m from the vent. Ashfall was reported in Toshima village. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

Geological summary: The 8-km-long 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. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded 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 open 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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E | Summit elev. 294 m

On 26 October GeoNet reported continuing unrest at Whakaari/White Island characterized by persistent gas-and-steam emissions and intermittent, minor, passive ash emissions during the previous two weeks. Sulfur dioxide gas emissions were low, averaging around 217 tonnes per day when measured during an overflight on 7 October. During an observation overflight on 19 October scientists saw gas-and-steam plumes rising from several vents on the NW and W sides of the lake. The temperature of the emissions was 145 degrees Celsius, slightly less than the 165 degrees measured on 5 October. The Aviation Color Code was remained at Yellow (the second lowest level on a four-color scale) and the Volcanic Alert Level remained at 2 (on a scale of 0-5).

Geological 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.

Reference:

Smithsonian / US Geological Survey Weekly Volcanic Activity Report – October 12 – 18, 2022 – Managing Editor: Sally Kuhn Sennert

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