The Weekly Volcanic Activity Report: October 5 – 11, 2022

the weekly volcanic activity report

New activity/unrest was reported for 8 volcanoes from October 5 to 11, 2022. During the same period, ongoing activity was reported for 20 volcanoes.

New activity/unrest: Alaid, Kuril Islands (Russia) | Chirinkotan, Kuril Islands (Russia) | Grimsvotn, Iceland | Mauna Loa, Hawaiian Islands (USA) | Mayon, Luzon (Philippines) | Nishinoshima, Izu Islands | Stromboli, Aeolian Islands (Italy) | Taal, Luzon (Philippines).

Ongoing activity: Aira, Kyushu (Japan) | Bulusan, Luzon (Philippines) | Ebeko, Paramushir Island (Russia) | Fuego, South-Central Guatemala | Great Sitkin, Andreanof Islands (USA) | Home Reef, Tonga Ridge | Ibu, Halmahera | Karymsky, Eastern Kamchatka (Russia) | Katmai, Alaska | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island | Merapi, Central Java | Nevados de Chillan, Central Chile | Pavlof, Alaska Peninsula, Alaska | Rincon de la Vieja, Costa Rica | Santa Maria, Southwestern Guatemala | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Central Chile | 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 a new lava flow descended Alaid’s S flank during 27-28 September and continued to be active at least through 6 October; a thermal anomaly was identified in satellite images throughout that same period of time. 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.

Chirinkotan, Kuril Islands (Russia)

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

SVERT reported that an ash plume from Chirinkotan was identified in satellite images at 1030 on 7 October rising 3.5-4 km (11,500-13,100 ft) a.s.l. and drifting 80 km ESE. The Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale).

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.

Grimsvotn, Iceland

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

Icelandic Meteorological Office (IMO) reported that recent GPS measurements indicated that the ice sheet had subsided about 3 m and the lake beneath the glacier at Grímsvötn had begun to drain, though the water had not reached the glacier’s margins. IMO forecasted a small jökulhlaup and raised the Aviation Color Code to Yellow (the second lowest level on a four-color scale) on 10 October. The report noted that neither seismicity nor gas emissions were elevated, though activity at the volcano had been increasing over time. Notably, a pulse of seismic tremor was recorded for about an hour during the previous week, and magmatic gases were measured in fumarolic plumes in 2020. By 12 October the outflow of water was about 300 cubic meters per second, with the onset of the jökulhlaup occurring slower than initially calculated, and the ice sheet had subsided a total of 7 m. The flooding was likely going to be equal to that seen during the summer and would likely not impact bridges or structures.

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 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.

Mauna Loa, Hawaiian Islands (USA)

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

On 5 October HVO noted recent increases in seismicity and deformation at Mauna Loa. The number of earthquakes increased from 5-10 per day in June to 10-20 per day during July-August. The number of daily earthquakes again intensified, to 40-50 per day, starting at about 0200 on 23 September, and peaks as high as 100 per day were recorded on 23 and 29 September. The small-magnitude (less than M3) earthquakes occurred beneath Moku‘aweoweo, the summit caldera, at depths of 2-3 km. Inflation accompanied the swarm and had also increased during the past two weeks.

Daily earthquake counts were relatively unchanged during 6-12 October. 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. Earthquakes were clustered beneath the summit caldera at depths of 3-5 km and below the NW flank at depths of 6-8 km. 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 the 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 since the Alert Level for Mayon was raised to 1 (on a 0-5 scale) on 21 August monitoring data had showed nothing notable. Changes in morphology of the dome and minor aseismic extrusion estimated at about 40,000 cubic meters was detected during 6 June-20 August based on daily visual and camera monitoring data. Based on these observations, the lava dome grew an additional 48,000 cubic meters by 4 October; re-mobilized light-colored ash had been deposited in Miisi Gully (S flank) beginning 2 October, likely derived from lava fragmentation during the extrusion process. Freshly extruded lava at the base of the summit lava dome was seen during an aerial survey conducted on 7 October. PHIVOLCS raised the Alert Level to 2 that same day. Daily white steam plumes were visible drifting down-flank and then to the W, WSW, and SSW during 8-10 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. Short-term inflation on the W to SW flanks and short-term deflation on the E and SE flanks had been detected since August.

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.

Nishinoshima, Izu Islands

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

JMA reported that the eruption at Nishinoshima continued during 5-11 October. Ash plumes rose 2.2-3.5 km (7,200-11,500 ft) a.s.l. and drifted in multiple directions.

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 at Stromboli had been more intense in the past two weeks with a large explosion on 29 September, short-lived lava overflows of the craters during 3-4 October, and collapses with pyroclastic flows and lava flows on 9 October. At 1524 on 29 September an explosion at vent N2 in Area N (North Crater area) generated an ash plume that rose 300 m above the summit and ejected abundant lava fragments, lapilli, and bombs along the Sciara del Fuoco. Activity during 3-9 October generally consisted of ongoing explosions from three vents in Area N and at least two vents in Area C-S (South-Central Crater area). Low-intensity explosions from the N1 vent (Area N) ejected bombs and lapilli 80-150 m high every 10-20 minutes. Explosions ejecting coarse material, along with sometimes intense spattering, occurred at two N2 vents. Explosions from at least two vents in Area C-S, which were not visible due to the camera views, ejected ash and coarse material less than 150 m above the vent at a rate of 1-6 events per hour. At 1108 on 3 October a fissure opened on the outer flank of N2, within the Sciara del Fuoco, and produced a lava flow that traveled to the coast; the flow was cooling by 1800. At 1107 the next morning, 4 October, lava overflowed the N crater (likely N2) and unconsolidated lava rolled down the upper part of the Sciara del Fuoco.

Activity again intensified on 9 October beginning at 0921 when lava overflowed from an area in the N part of N2 and lava effused from the fissure that had opened on 3 October. At 0922 the rim of N2 collapsed and generated a pyroclastic flow that traveled down the Sciara del Fuoco, reached the sea within 30 seconds, and advanced over the water for a few hundred meters. Immediately afterwards a large amount of lava flowed down the Sciara del Fuoco in two main branches and reached the coast within a few minutes. Lava continued to flow to the coast during the rest of the day. The Dipartimento della Protezione Civile raised the Alert Level to Orange (the second highest level on a four-color scale). Collapses of material in the Sciara del Fuoco continued overnight, possibly due to erosion of the channels from lava flows. By 0919 on 10 October lava flows were only reaching part way down the Sciara del Fuoco, stopping about 400 m from the coast. Lava flows continued to stop part way down the flank during 10-12 October. Frequent collapses of material in the channel eroded by the lava flow and material from the lava flow itself descended to the coast. Spattering from Area N was visible.

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 5-11 October. Upwelling gasses and hot fluids in the lake continued to be visible. A small, three-minute-long phreatomagmatic burst occurred on 5 October; according to the Washington VAAC an ash plume rose to 600 m (2,000 ft) a.s.l. and drifted SW. White steam emissions rose 900 m above the lake, though during 10-11 October plumes rose as high as 2.4 km. 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 nine eruptive events and one explosion at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) were recorded during 3-10 October. Volcanic plumes rose as high as 1.5 km above the crater rim and large blocks were ejected 600-900 m 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.

Bulusan, Luzon (Philippines)

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

PHIVOLCS issued a special advisory for Bulusan on 7 October, noting that 29 volcanic earthquakes were recorded from 0500 on 6 October until the time the report was issued at 1500 on 7 October. Minor white steam emissions rose from vents in the crater and from NW vents. Data from continuous GPS and radial tilt measurements indicated short-term inflation on the S flanks since April 2022. The inflation and increased seismicity were likely caused by shallow hydrothermal processes. The Alert Level remained at 0 (on a scale of 0-5) and 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.

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 3.5 km (11,500 ft) a.s.l. and drifted E and NE during 29 September-6 October. Ashfall was reported in Severo-Kurilsk on 29 September and 6 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.

Fuego, South-Central Guatemala

14.473°N, 90.88°W | Summit elev. 3763 m

INSIVUMEH reported that 5-10 explosions per hour were recorded at Fuego during 4-10 October, generating ash plumes that rose as high as 1.2 km above the crater rim. The ash plumes drifted as far as 20 km NW, W, SW, and SSW causing almost daily ashfall in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Los Yucales (12 km SW), Sangre de Cristo (8 km WSW), El Porvenir (8 km ENE), San Pedro Yepocapa (8 km NW), Finca Palo Verde, La Rochela, and Ceilán. Daily shock waves rattled structures in communities around the volcano. Daily block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda, Las Lajas (SE), and El Jute (ESE) drainages, often reaching vegetated areas. Explosions ejected incandescent material as high as 350 m above the summit on some of the days. Lahars resulting from substantial rainfall descended the Las Lajas and El Jute drainages on the ESE flank on 11 October, carrying tree branches, trunks, and blocks as large as 1.5 m in diameter.

Geological summary: Volcán Fuego, one of Central America’s most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala’s former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that continuing slow lava effusion at Great Sitkin was confirmed by a 5 October satellite image and likely continued during 6-11 October. Seismicity remained at low levels, though it slightly increased during 5-6 October. Elevated surface temperatures were identified during 4-8 October; weather clouds prevented webcam and satellite views during 8-11 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 daily steam plumes from Home Reef were identified in satellite images during 4-11 October. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale) on 5 October. At 0040 on 6 October an ash plume rose as high as 3 km (10,000 ft) a.s.l. and drifted 5 km SE. Satellite-based measurements showed that the island had not changed in size between 28 September and 10 October, remaining at 268 m N-S and 283 m E-W. The island reached 15-18 m above the water surface, and was steeper on the E half but more gently sloped on the W. The daily emission count variable with about 8-19 events per day during 4-9 October and about 1-3 per day during 10-11 October. The Aviation Color Code was lowered to Yellow on 11 October. 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.

Ibu, Halmahera

1.488°N, 127.63°E | Summit elev. 1325 m

PVMBG reported that the eruption at Ibu continued during 4-11 October. Daily gray-and-white ash plumes of variable densities rose as high as 1 km above the summit and drifted in multiple directions. The Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Geological 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, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and 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. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

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 on 30 September and during 1-2 and 5-6 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: 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.

Katmai, Alaska

58.28°N, 154.963°W | Summit elev. 2047 m

AVO reported that on 9 October strong winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes blew unconsolidated ash SE across Shelikof Strait to Kodiak Island at an altitude up to 1.5 km (5,000 ft) a.s.l. The ash was originally deposited during the Novarupta eruption in 1912. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Geological summary: Prior to 1912, Mount Katmai was a compound stratovolcano with four NE-SW-trending summits, most of which were truncated by caldera collapse in that year. Two or more large explosive eruptions took place during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene, but Holocene lava flows from a flank vent descend the SE flank of the SW edifice into the Katmai River canyon. Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The steep walled young caldera has a jagged rim that rises 500-1,000 m above the caldera floor and contains a 250-m-deep, still-rising lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916. Post-1912 glaciers have formed on a bench within Katmai caldera.

Kilauea, Hawaiian Islands (USA)

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

HVO reported that by 5 October about 111 million cubic meters of lava had erupted from the vent in the lower W wall of Kilauea’s Halema`uma`u Crater since the current eruption began on 29 September 2021, raising the crater floor by 143 m. Lava continued to enter the lake during 5-11 October. The active part of the lake stayed at a relatively steady level through the week, varying only slightly. 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: 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 5-11 October. Daily white emissions rose as high as 500 m above the summit and drifted W, NW, and NE. White-and-gray plumes rose as high 200 m and drifted NW and W during 9-10 October. Webcam images posted with the daily observatory reports often showed incandescence above the crater rim. 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 30 September-6 October and seismicity remained at high levels. The SW lava dome produced as many as five lava avalanches that traveled as far as 1.8 km down the Bebeng drainage on the SW flank, and one that traveled 800 m down the W flank upstream of upstream of Kali Putih. No significant morphological changes to the central and SW lava domes were evident in drone photographs, though both domes continued to grow. 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 the 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 during 16 September-11 October. Dome 4 in Nicanor Crater grew until mid-September, coincident with thermal anomalies seen in satellite images, which decreased and were not present during the second half of the month. Explosions during 16-30 September and into early October produced ash plumes that generally rose no higher than 1 km above the crater rim. Notably, an explosion on 19 September produced an ash plume that rose 1.1 km and drifted SE, and ejected blocks 500 m from the crater rim. An incandescent ash plume from a second explosion rose 1.7 km and drifted SE, causing ashfall on that flank. The explosions that day partially destroyed the dome.

At 1906 on 8 October a long-period earthquake signal was followed by an ash plume that rose 1.7 km and drifted NNE. An explosion at 1926 on October generated a dense ash plume that rose 2.5 km and drifted NNW. Pyroclastic flows traveled short distances down the NNW flank. 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 4-11 October. Seismic tremor continued. Strongly elevated surface temperatures were identified in satellite images during 5-6 October and incandescence was visible in nighttime webcam images. Discolored snow near the vent was visible in webcam views during the morning of 7 October suggesting low-level explosive activity; a small explosion was recorded at 1503 that same day though cloudy conditions prevented visual confirmation. Two small explosions were detected during 8-11 October. Very small ash emissions and lava near the vent were visible in occasional clear webcam images during 10-11 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.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W | Summit elev. 1916 m

OVSICORI-UNA reported continuing eruptive activity at Rincón de la Vieja characterized by occasional small phreatic explosions. A small explosion at 1923 on 4 October lasted two minutes but was not visually observed due to darkness and weather conditions. Small gas-and-steam emissions were recorded at 1647 on 8 October and 0940 on 9 October; at least the first emission was seen rising above the crater rim.

Geological summary: Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the “Colossus of Guanacaste,” it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Santa Maria, Southwestern Guatemala

14.757°N, 91.552°W | Summit elev. 3745 m

INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 4-11 October. Effusion from Caliente cone fed lava flows that descended the San Isidro and El Tambor drainages on the W and SW flanks. Block avalanches from the dome, and from both the ends and sides of the flows, descended the S, SW, and W flanks. The avalanches sometimes generated minor ash plumes. Incandescence from the dome and the lava flows was often visible at night or during early mornings. Explosions during 6-7 October ejected incandescent material onto all flanks. A sulfur odor was reported in Mirador de Samriaguito. Small explosions were recorded during 9-10 October.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after the construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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 29 September-6 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 3-10 October. A total of 55 explosions produced eruption plumes that rose as high as 2.4 km above the crater rim and occasionally merged into weather clouds. The explosions ejected large blocks as far as 700 m from the vent. Crater incandescence was visible nightly. 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 reported increased activity at Villarrica on 10 October. A thermal anomaly was identified in satellite images and was the most intense anomaly recorded since January 2021. Incandescence above the crater rim was visible in a webcam image. 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.

Whakaari/White Island, North Island (New Zealand)

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

On 10 October GeoNet reported continuing unrest at Whakaari/White Island during the previous week based on webcam views, overflights, and satellite images. Very vigorous steam-and-gas plumes were seen rising from the active vent in webcam images throughout the week. Sometimes minor amounts of ash were included in the plumes from collapses of the vent walls. On 5 October the temperature of the emissions was 165 degrees Celsius and sulfur dioxide gas flux was low at 200-234 tonnes per day, measured during an overflight. Sulfur dioxide emissions had not been detected in satellite images since 18 September. The Aviation Color Code 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 5 – 11, 2022 – Managing Editor: Sally Kuhn Sennert

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