The Weekly Volcanic Activity Report: October 12 – 18, 2022

the weekly volcanic activity report

New activity/unrest was reported for 8 volcanoes from October 12 to 18, 2022. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Alaid, Kuril Islands (Russia) | Bulusan, Luzon (Philippines) | Chikurachki, Paramushir Island (Russia) | Grimsvotn, Iceland | Kerinci, Central Sumatra | Nishinoshima, Izu Islands | Stromboli, Aeolian Islands (Italy) | Taal, Luzon (Philippines).

Ongoing activity: Aira, Kyushu (Japan) | Chirinkotan, Kuril Islands (Russia) | Ebeko, Paramushir Island (Russia) | Great Sitkin, Andreanof Islands (USA) | Home Reef, Tonga Ridge | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Mauna Loa, Hawaiian Islands (USA) | Mayon, Luzon (Philippines) | Merapi, Central Java | Nevados de Chillan, Central Chile | Pavlof, Alaska Peninsula, Alaska | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Central Chile.

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 7-14 October and a daily thermal anomaly was identified in satellite images. Explosive activity on 16 October generated ash plumes that rose to 3.7 km (12,100 ft) a.s.l. and drifted 293 km ESE. 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.

Bulusan, Luzon (Philippines)

12.769°N, 124.056°E | Summit elev. 1535 m

On 12 October PHIVOLCS raised the Alert Level for Bulusan to 1 (on a scale of 0-5) due to increased seismicity, inflation, and gas emissions. From 0500 on 11 October to 1500 on 12 October the seismic network detected 126 weak earthquakes located at depths of 0-5 km. Most of the events were concentrated beneath the NW flank and summit area and were indicative of rock-fracturing processes. Other data suggested increased hydrothermal activity and unrest including increased temperatures and carbon dioxide emissions at area hotsprings beginning earlier in the year, pronounced inflation of the SW and S flanks that began in September, and a sulfur odor reported by residents of Sitio Talistison in Barangay Mapaso (Irosin) and Barangay San Roque (Bulusan) during 10-11 October. Daily earthquakes totaled 164 during 13-14 October and 79 during 14-15 October; daily counts were 26-32 during 15-18 October. Sulfur dioxide emissions were 302-386 tonnes per day during 15-16 October. PHIVOLCS reminded the public not to enter the 4-km-radius Permanent Danger Zone (PDZ) nor the 2 km Extended Danger Zone (EDZ) on the SE flank.

Geological summary: Luzon’s southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Chikurachki, Paramushir Island (Russia)

50.324°N, 155.461°E | Summit elev. 1781 m

KVERT reported that an explosive eruption at Chikurachki began at around 0310 on 16 October. A dense ash plume identified in satellite images rose to 4.5 km (14,800 ft) a.s.l. and drifted 240 km ESE. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale). At 1011 and 1620 that same day ash plumes were visible in satellite images rising as high as 3.5 km (11,500 ft) a.s.l. and drifting ESE; by 1620 ash plumes from the eruption had extended as far as 523 km. KVERT noted that ash emissions were last seen at 0130 on 17 October and a thermal anomaly was visible at 0432. The Aviation Color Code was lowered to Yellow at 1223 on 18 October, and then to Green at 1428 on 19 October. Steam-and-gas emissions persisted. All times are local.

Geological summary: Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is a relatively small cone constructed on a high Pleistocene edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic Plinian eruptions have occurred during the Holocene. Lava flows have reached the sea and formed capes on the NW coast; several young lava flows are also present on the E flank beneath a scoria deposit. The Tatarinov group of six volcanic centers is located immediately to the south, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov centers are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of an eruption around 1690 CE from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Grimsvotn, Iceland

64.416°N, 17.316°W | Summit elev. 1719 m

Icelandic Meteorological Office (IMO) reported that the small jökulhlaup at Grímsvötn that began on 10 October had peaked on 16 October and then began to subside. The onset of the jökulhlaup was slower than forecasted, flowing in the Gigjukvisl River at about 300 cubic meters per second by 12 October. The ice sheet had subsided a total of 7 m. A M 2 earthquake was recorded on 13 October just NE of Grímsvötn but did not signal increased seismicity. By 14 October the outflow from the lakes was an estimated 500 cubic meters per second and subsidence has totaled 15 m. Four earthquakes, all under M 2.5, were recorded during 15-16 October. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale).

Geological summary: Grímsvötn, Iceland’s most frequently active volcano in recent history, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200-m-thick ice shelf, and only the southern rim of the 6 x 8 km caldera is exposed. The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam. Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world’s largest known historical lava flow in 1783. The 15 km3 basaltic Laki lavas were erupted over a 7-month period from a 27-km-long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.

Kerinci, Central Sumatra

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

PVMBG reported that white-and-black plumes from Kerinci rose as high as 350 m above the summit and drifted NE during 15-16 October. Two VONAs were posted on 19 October; at 0620 on 19 October an ash plume rose 500 m above the summit and drifted NW, and at 0815 an ash plume rose 700 m and drifted NW. 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.

Nishinoshima, Izu Islands

27.247°N, 140.874°E | Summit elev. 25 m

JMA reported that on 12 October ash plumes from Nishinoshima rose 2.2-3.5 km (7,200-11,500 ft) a.s.l. and drifted NW and W.

Geological summary: The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E | Summit elev. 924 m

INGV reported that activity had decreased at Stromboli by 16 October following a week that included lava overflows at vent N2 (in Area N, North Crater), a partial collapse of the vent rim, and both pyroclastic and lava flows descending the Sciara del Fuoco. Lava flows continued to effuse from N2 during 10-15 October, though they gradually traveled to shorter distances through the week. Material from the eroded channel of the Sciara del Fuoco and collapses from the lava flows descended the channel, contacted the water and produced steam and ash plumes, and formed a delta of debris. By 15 October lava flows had rebuilt the N2 rim which prevented lava from flowing down the Sciara del Fuoco.

Explosive activity at N2 was variable from low levels to intense spattering that culminated into lava fountaining during 10-13 October. The activity abruptly decreased on 14 October, though minor spattering continued. Occasional low-intensity ash emissions were visible during the morning of 16 October and spattering had ceased. Activity at N1 during 10-16 October was characterized by low-intensity explosions ejecting bombs and lapilli less than 80 m high.

Geological summary: Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the “Lighthouse of the Mediterranean” in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Taal, Luzon (Philippines)

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

PHIVOLCS reported continuing unrest at Taal during 11-18 October. Upwelling gasses and hot fluids in the lake continued to be visible almost daily, and white steam emissions that generally rose as high as 1.5 km above the lake drifted in variable directions. Low-level background tremor and 1-9 daily volcanic earthquakes were recorded during 11-14 October. Sulfur dioxide emissions averaged 3,882 tonnes per day on 13 October. Activity increased during 14-15 October with six small phreatomagmatic bursts, each lasting 1-2 minutes long, and 26 volcanic earthquakes. Steam-and-gas plumes rose as high as 2.4 km and drifted NE and SE. Based on SIGMETS (Significant Meteorological statements) issued by the Ninoy Aquino International Airport, the Tokyo VAAC reported that during 14-15 October three ash plumes rose as high as 600 m (2,000 ft) a.s.l. and drifted NW. During 15-16 October one phreatomagmatic burst was recorded along with 12 volcanic earthquakes and nine periods of volcanic tremor, each 2-70 minutes long. Six periods of volcanic tremor, totaling almost 4.5 hours, were detected during 16-17 October, and sulfur dioxide emissions were 4,422 tonnes per day on 17 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.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that 10 eruptive events and four explosions at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) were recorded during 10-17 October. Volcanic plumes rose as high as 1.7 km above the crater rim and large blocks were ejected as far as 1.7 km from the vent. Incandescence at the crater was visible nightly. No notable changes at the summit were visible during an overflight on 12 October. Sulfur dioxide emissions were characterized as extremely high on 14 October at 4,000 tons per day. 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.

Chirinkotan, Kuril Islands (Russia)

48.98°N, 153.48°E | Summit elev. 724 m

SVERT lowered the Aviation Color Code for Chirinkotan to Green (the lowest level on a four-color scale) on 10 October; ash plumes were last detected on 7 October.

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

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 generated ash plumes that rose to 4 km (13,100 ft) a.s.l. and drifted E and SE during 7-13 October. Ashfall was reported in Severo-Kurilsk during 6-7 and 13 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 11-18 October. Satellite images were mostly cloudy, though continued slow growth of the flow field and steaming from a new flow margin were identified in satellite images on 12 October. Seismicity remained at low levels. 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 last eruptive event at Home Reef occurred at 0209 on 13 October, based on satellite images processed by VOLCAT (Volcanic Cloud Analysis Toolkit) software. A thermal anomaly was identified in satellite images at 0146 on 17 October. The Aviation Color Code remained at Yellow and mariners were advised to stay 4 km away from the volcano.

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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E | Summit elev. 1513 m

On 15 October KVERT lowered the Aviation Color Code for Karymsky to Yellow (the second lowest level on a four-color scale), noting that strong explosions were last recorded on 7 August. Though a thermal anomaly continued to be identified in satellite images, the temperature of that anomaly had been decreasing since the explosions. Gas-and-steam emissions persisted, and in recent days snow sometimes covered the volcano.

Geological 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.

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 11-18 October entering the lava lake and flowing onto the crater floor. Part of the lake’s surface was continuously active. 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.

Lewotolok, Lembata Island

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

PVMBG reported that the Strombolian eruption at Lewotolok continued during 11-18 October. White emissions rose as high as 500 m above the summit almost daily and drifted in multiple directions. At 0351 on 14 October an eruptive event produced a dense gray ash plume that rose about 1.2 km above the summit and drifted SW. 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.

Mauna Loa, Hawaiian Islands (USA)

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

HVO reported continuing unrest at Mauna Loa during 12-18 October. The seismic network detected 22-65 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 pair of earthquakes, M 4.6 and M 5, were recorded at 0907 on 14 October. The first one was located S of Pahala, just offshore, at a depth of about 13 km. The second earthquake followed 24 seconds later and was located S of Pahala (beneath Highway 11) at a depth of 7.4 km. The earthquakes were followed by more than 150 aftershocks in the Pahala region over the next two days. Twenty of the aftershocks were greater than M 2.5 and four were M 3-4. HVO noted that the unrest was likely driven by accumulation of new magma 3-8 km beneath the summit. 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E | Summit elev. 2462 m

PHIVOLCS reported that white steam plumes from Mayon rose no higher than 500 m above the summit and drifted E. Sulfur dioxide emissions averaged 301 tonnes per day on 12 October. One volcanic earthquake was detected during 16-17 October. Electronic Distance Measuring (EDM), precise leveling, continuous GPS, and electronic tilt monitoring data showed that the volcano had been slightly inflated, especially on the NW and SE flanks, since 2020. The Alert Level remained at 2 (on a 0-5 scale) and the public was reminded to stay outside of the 6-km-radius Permanent Danger Zone.

Geological summary: Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi continued during 7-13 October and seismicity remained at high levels. The SW lava dome produced as many as seven lava avalanches that traveled as far as 1.5 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.

Nevados de Chillan, Central Chile

36.868°S, 71.378°W | Summit elev. 3180 m

SERNAGEOMIN reported continuing activity at Nevados de Chillán’s Nicanor Crater during 11-18 October. At 0043 on 12 October a long-period earthquake was recorded and was possibly associated with an emission, but weather clouds prevented visual confirmation. A long-period earthquake at 1504 on 13 October was followed by a dense gray-black ash plume that rose almost 2.3 km and drifted NNE. Pyroclastic flows descended the NNE flank. Another long-period event, at 2108 on 15 October, was followed by the ejection of incandescent material as high as 800 m above the crater rim and as far as 700 m NE onto the flank. Explosions at 1613 on 16 October produced a dense grayish-black ash plume that rose more than 400 m and drifted SE, though weather clouds inhibited views. A pyroclastic flow traveled more than 500 m NNE. The Alert Level remained at Yellow, the second lowest level on a four-color scale. Sistema Nacional de Prevención y Respuesta ante Desastres (SINAPRED) maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto and Coihueco, and reminded residents not to approach the crater within 2 km.

Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The dominantly andesitic Cerro Blanco (Volcán Nevado) stratovolcano is located at the NW end of the massif. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The Volcán Nuevo lava-dome complex formed during 1906-1945 on the NW flank of Viejo. The Volcán Arrau dome complex was then constructed on the SE side of Volcán Nuevo between 1973 and 1986, and eventually exceeded its height. Smaller domes or cones are present in the 5-km valley between the two major edifices.

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 11-18 October and seismic tremor continued. Multiple explosions were recorded in seismic and infrasound data almost daily. Clear webcam views captured very small ash emissions and lava in the immediate vicinity of the vent during 11-14 October, and incandescent rock fragments being ejected from the vent during 13-14 October. Elevated surface temperatures were identified in satellite images on most days during 13-18 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 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.

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 6-14 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 10-17 October. A total of 71 explosions produced eruption plumes that rose as high as 2 km above the crater rim and ejected blocks as far as 600 m from the vent. Crater incandescence was visible nightly. Occasional ashfall was reported in Toshima village (3.5 km SSW) during the first half of the week. 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.

Villarrica, Central Chile

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

POVI posted an 18 October photo of Villarrica showing incandescence above the crater rim and noted that crater incandescence had been visible on clear nights. 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.

Reference:

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

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