The Weekly Volcanic Activity Report: March 13 - 19, 2024

New activity/unrest was reported for 4 volcanoes from March 13 to 19, 2024. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Fernandina, Isla Fernandina (Galapagos) | Ioto, Volcano Islands | Masaya, Nicaragua | Reykjanes, Reykjanes Peninsula.

New activity/unrest

Fernandina, Isla Fernandina (Galapagos)

0.37°S, 91.55°W; summit elev. 1476 m

IG-EPN reported that the eruption at Fernandina that began on 2 March occurred from about 20 circumferential fissures within an area 4.3 km long on the upper SE flank, between 1,000-1,200 m elevation. Multiple lava flows descended the SE flank; the longest lobe traveled SE then curved S, reaching about 750 m elevation, and having a total length of 8-9 km. Activity declined on 6 March and only Fissure 13 continued to effuse lava. The characterization of the activity level was changed from high to moderate on 13 March. The lava flows from Fissure 13 were active during 13-19 March based on thermal anomalies identified in satellite images, gas emissions, and photos shared by the Parque Nacional Galápagos. Sulfur dioxide emissions detected by satellite fluctuated between 576 and 1,133 tons per day.

Geological summary: Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic “overturned soup bowl” profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Ioto, Volcano Islands

24.751°N, 141.289°E; summit elev. 169 m

The Japan Coast Guard conducted an overflight of Ioto (Iwo-jima) on 13 February and observed no eruptive activity. A remnant part of the island remained that was about 25 m wide and 10 m high and in the shape of an arch. White fumarolic activity occurred at the S end of the island and hot water over the main vent area was observed. Eruptive activity in an area adjacent to the island was observed during an overflight on 16 March. A video posted with the report showed a roughly circular area of disturbed whitish water with several steaming rocks located around the margins. The report urged nearby ships to use caution in the area.

Geological summary: Ioto, in the Volcano Islands of Japan, lies within a 9-km-wide submarine caldera. The volcano is also known as Ogasawara-Iojima to distinguish it from several other “Sulfur Island” volcanoes in Japan. The triangular, low-elevation, 8-km-long island narrows toward its SW tip and has produced trachyandesitic and trachytic rocks that are more alkalic than those of other volcanoes in this arc. The island has undergone uplift for at least the past 700 years, accompanying resurgent doming of the caldera; a shoreline landed upon by Captain Cook’s surveying crew in 1779 is now 40 m above sea level. The Motoyama plateau on the NE half of the island consists of submarine tuffs overlain by coral deposits and forms the island’s high point. Many fumaroles are oriented along a NE-SW zone cutting through Motoyama. Numerous recorded phreatic eruptions, many from vents on the W and NW sides of the island, have accompanied the uplift.

Masaya, Nicaragua

11.9844°N, 86.1688°W; summit elev. 594 m

According to the U.S. Embassy in Nicaragua the Parque Nacional Volcán Masaya continued to be closed on 12 March due to an increased potential for explosive activity due to the blocking of the lava lake from landslide deposits in Santiago Crater. A satellite image from 13 March showed a slightly larger thermal anomaly on the NE crater floor compared to an 8 March image. According to a 13 March news article, INETER reported that landslides from the inner SW and NW crater walls were continuing. In a 14 March news article, a resident that lived near the volcano noted that the typical gas emissions seen before the 2 March landslide were no longer observed.

Geological summary: Masaya volcano in Nicaragua has erupted frequently since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano’s molten “gold” until it was found to be basalt rock upon cooling. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of observed eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Recent lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Reykjanes, Reykjanes Peninsula

63.817°N, 22.717°W; summit elev. 140 m

After about 40 minutes of increased seismicity and ground deformation, a fissure eruption within the Reykanes volcanic system began at 2023 on 16 March near the older Sundhnúkagígar crater row on the Reykjanes Peninsula, prompting IMO to raise the Aviation Color Code to Red (the highest level on a four-color scale). According to a news report about 700 people at the Blue Lagoon spa and the few people in Grindavík were evacuated within about a 30-minute period. IMO noted that the fissure quickly lengthened to 2.9 km and that the length and location was similar to the 8 February fissure eruption. The fissure was oriented roughly NE-SW and small fissure segments were aligned in the same orientation but offset at each end. A steam-and-gas-rich plume rose above 3 km; no ash was evident in the plume so IMO lowered the Aviation Color Code to Orange at 2122. Lava fountaining occurred along the length of the fissure and lava flows advanced E, SE, SW, and NW at a rate of about 1 km per hour. By 2210 the S flow was about 200 m from the earthen barriers constructed to protect the E part of Grindavík. Lava advanced NW, curved around the Stóra Skógfell cones, and then flowed SW; by 2220 lava was 700-800 m from Grindavíkurvegur (Road 43) and advancing towards the road at a rate of about 660 m per hour. At around 0030 on 17 March lava flowed W over the road, along the earthen barrier, and towards the water distribution pipe from the Svartsengi power plant; the flow slowed during the morning about 200 m from the pipe, only advancing minimally.

Eruptive activity decreased overnight during 16-17 March. Seismicity significantly decreased with only a few earthquakes recorded after 0300 on 17 March, coinciding with decreased tremor. Lava flows to the S were diverted from Grindavík along the barriers towards the SE. The effusion rate decreased substantially at around 0400, and lava was produced by a segment near the middle of the fissure that was 500 m long. By 1300 lava fountaining was concentrated at three areas along the fissure. The S flow advanced at a rate of about 12 m per hour during 1015-1630 and a few hours later the leading lobe was about 330 m from Suðurstrandarvegur, the main road along the S coast of the Reykjanes Peninsula. During the morning sulfur dioxide emissions peaked at 15,000 micrograms per cubic meter and emissions detected by satellite that day were the highest measured of the recent 2023-2024 eruptions. Sulfur dioxide fluxes were as high as 50 kilograms per second. A news articles noted that some small lava ponds formed near the Grindavík barriers and at the flow near Suðurstrandarvegur. The area of the flow field was an estimated 5.85 square kilometers based on a satellite image acquired at 1456 on 17 March.

The eruption continued at stable levels during 18-19 March. Lava activity was concentrated at a series of vents which had built cones at the S end of the fissure; occasional fountaining was observed. The lava flows that had crossed Grindavíkurvegur and stopped near Suðurstrandarvegur were slow moving. Deformation data suggested that magma continued to flow into the dyke system. According to Almannavarnadeild ríkislögreglustjóra (National Commissioner of the Icelandic Police and Department of Civil Protection and Emergency Management) Grindavík residents were permitted to return to town on 19 March, though it was not recommended that they stay overnight. The Blue Lagoon remained closed.

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Ongoing activity

Aira, Kyushu (Japan)

31.5772°N, 130.6589°E; summit elev. 1117 m

JMA reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 11-18 March with nighttime crater incandescence. Sulfur dioxide emissions were extremely high, averaging 3,100 tons per day on 12 March. During an overflight on 13 March emissions obscured views of Minamidake Crater, though observers noted no changes at the either the Showa Crater geothermal area or around the flanks of both craters. An explosion at 0536 on 13 March produced an ash plume that rose 1 km above the crater rim and drifted S and ejected large blocks 300-500 m from the vent. Eruptive events at 1345 on 13 March and at 0450 and 0538 on 15 March generated ash plumes that rose 1-2.9 km above the crater rim and drifted SE. An ash plume from an explosion at 2158 on 16 March rose 600 m above the crater rim and drifted NE; large blocks were ejected 600-900 m from the vent. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters.

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 caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76.

Dukono, Halmahera

1.6992°N, 127.8783°E; summit elev. 1273 m

PVMBG reported that the eruption at Dukono was ongoing during 13-19 March. Gray-and-white ash plumes rose as high as 1.9 km above the summit and drifted NW, NE, E, and S on most days; emissions were not observed on 14 March. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E; summit elev. 1103 m

KVERT reported that moderate explosive activity was ongoing at Ebeko during 8-14 March. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions on 12 March generated ash plumes that rose as high as 3 km (10,000 ft) a.s.l. and drifted E. Ashfall was reported in Severo-Kurilsk that same day. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are UTC; 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 in Great Sitkin’s summit crater during 13-19 March. Weather clouds obscured or partly obscured satellite and webcam views during most of the week. A radar satellite image acquired during 17-18 March showed advancement of the active NW lava flow, movement at the E lava flow, and uplift of the center of the lava dome above the vent. Seismicity was low and a few small earthquakes were recorded during 18-19 March. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger 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 older edifice and produced a submarine debris avalanche. Deposits from this and an even 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. Eruptions have been recorded since the late-19th century.

Inielika, Flores Island

8.73°S, 120.98°E; summit elev. 1559 m

PVMBG lowered the Alert Level for Inielika to 1 (on a scale of 1-4) at 1100 on 16 March, noting that unrest had decreased based on visual observations, seismicity, and geochemistry data. The public was warned to stay at least 500 m away from the summit crater and to avoid solfatara zones and hot springs.

Geological summary: Inielika is a broad, low volcano in central Flores Island that was constructed within the Lobobutu caldera. The complex summit contains ten craters, some of which are lake filled, in a 5 km2 area north of the city of Bajawa. The largest of these, Wolo Runu and Wolo Lega North, are 750 m wide. A phreatic explosion in 1905 formed a new crater, and was the volcano’s only eruption during the 20th century. Another eruption took place about a century later, in 2001. A chain of Pleistocene cinder cones, the Bajawa cinder cone complex, extends southward to Inierie.

Kavachi, Solomon Islands

8.991°S, 157.979°E; summit elev. -20 m

On 8 March satellite data showed a plume of discolored water from the submarine Kavachi volcano extending N and curving E about 25 km before dissipating.

Geological summary: Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is located in the Solomon Islands south of Vangunu Island. Sometimes referred to as Rejo te Kvachi (“Kavachi’s Oven”), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported “fire on the water” prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Lewotolok, Lembata Island

8.274°S, 123.508°E; summit elev. 1431 m

PVMBG reported that the eruption at Lewotolok continued during 13-19 March. White steam-and-gas plumes rose 50-200 m above the summit and drifted E and SE on 15, 17, and 19 March; emissions were not visible on the other days. According to a news report the lava flows on the S and SE flanks remained at 600 m and 1.8 km long, respectively, and had not advanced, though lava effusion was ongoing. Strombolian explosions continued through at least 15 March, ejecting incandescent material as far as 500 m from the crater. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 2 km away from the vent and 3 km away from the vent on the S and 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.

Marapi, Central Sumatra

0.38°S, 100.474°E; summit elev. 2885 m

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 13-19 March. White-and-gray ash plumes rose 150-1,000 m above the summit and drifted E, SE, and SW during 13-14 and 16 March. White steam-and-gas plumes rose 100-200 m above the summit and drifted NE, E, and SE on 15, 17, and 19 March. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 4.5 km away from the active crater.

Geological summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra’s most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Merapi, Central Java

7.54°S, 110.446°E; summit elev. 2910 m

BPPTKG reported that the eruption at Merapi (on Java) continued during 8-14 March. Seismicity remained at high levels. The SW lava dome produced 91 lava avalanches that descended the SW flank as far as 1.8 km. Morphological changes to the SW lava dome identified in webcam images were due to continuing effusion and collapses of material. 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.

Nyamulagira, DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

The Observatoire Volcanologique de Goma (OVG) reported that lava effusion at Nyamulagira was continuing. Thermal anomalies in an area just NE of the central part of the caldera were identified in a 17 March satellite image. A larger thermal anomaly in the same area, though it extended farther SE, was evident in a 7 March image.

Geological summary: Africa’s most active volcano, Nyamulagira (also known as Nyamuragira), is a massive high-potassium basaltic shield about 25 km N of Lake Kivu and 13 km NNW of the steep-sided Nyiragongo volcano. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Documented eruptions have occurred within the summit caldera, as well as from the numerous flank fissures and cinder cones. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Recent lava flows extend down the flanks more than 30 km from the summit as far as Lake Kivu; extensive lava flows from this volcano have covered 1,500 km2 of the western branch of the East African Rift.

Reventador, Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

IG-EPN reported that a moderate eruption at Reventador was ongoing during 12-19 March. Seismicity was characterized by 23-48 daily explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Ash-and-gas plumes rose as high as 1.3 km above the crater rim and drifted in multiple directions on most days. Weather conditions sometimes prevented views; emissions were not visible during 14-15 March. Avalanches of incandescent material were visible most overnights, descending the flanks as far as 900 m from the summit. Minor crater incandescence was visible during 14-15 March. The weather was occasionally rainy during the week; a seismic signal indicating a lahar was recorded at 0210 on 19 March. Secretaría de Gestión de Riesgos maintained the Alert Level at Orange (the second highest level on a four-color scale).

Geological summary: Volcán El 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 stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded 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.

Sabancaya, Peru

15.787°S, 71.857°W; summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported that the eruption at Sabancaya continued at moderate levels during 11-17 March with a daily average of 29 explosions. Gas-and-ash plumes rose as high as 2.2 km above the summit and drifted less than 10 km W, SW, and S. Thermal anomalies over the lava dome in the summit crater were identified in satellite data. Slight inflation was detected near the Hualca Hualca sector (4 km N). The Alert Level remained at Orange (the third level on a four-color scale) and the public were warned to stay outside of a 12 km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning “tongue of fire” in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Sangay, Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

IG-EPN reported that high levels of eruptive activity continued at Sangay during 12-19 March. The seismic network recorded 61-319 daily explosions during 12-18 March, though there were 3,838 explosions during 18-19 March with most of the events attributed to a period of heightened activity. Inclement or cloudy weather prevented views on most days, though incandescent material was visible descending the SE flank as far as 2 km during dark hours on most days. Crater incandescence was sometimes visible. A series of explosions began at 1540 on 18 March and lasted several hours. The explosions produced ash-and-gas plumes that rose as high as 2.5 km above the crater rim and drifted W and SW. Ashfall was reported in several towns including Palmira (46 km W), Alausí (60 km SW), and Achupallas (56 km SW) in the province of Chimborazo. Incandescent material was ejected above the crater and descended the upper SE flanks. Pyroclastic flows traveled as far as 1.8 km down the SE flank. During the afternoon and into the night roaring noises and vibrations were reported in areas surrounding the volcano. Secretaría de Gestión de Riesgos (SGR) maintained the Alert Level at Yellow (the second highest level on a four-color scale).

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 eruptive activity continued at Semeru during 13-19 March. Eruptive events were recorded at 0047 on 15 March and at 1653 on 17 March by the seismic network, though emissions were not observed. At 0625 on 19 March a dense white-and-gray ash plume rose 500 m above the summit and drifted NE. The Alert Level remained at 3 (the third highest level on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages 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 eruptive activity at Sheveluch continued with a thermal anomaly identified in satellite images on 7, 9, and 13 March. Weather clouds obscured views on the other days during 7-14 March. The Aviation Color Code remained at Orange (the third 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 11-18 March. Crater incandescence was observed in webcam images nightly and large blocks were sometimes ejected up to 600 m from the vent. An explosion at 0501 on 18 March generated an ash plume that rose 900 m above the crater rim and drifted SE. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 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 active summit craters. The summit is truncated by a large breached crater extending to the sea on the E 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 covered 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 an open collapse scarp extending 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.

Tinakula, Santa Cruz Islands

10.386°S, 165.804°E; summit elev. 796 m

A thermal anomaly extending from the summit of Tinakula down the W flank to the coast was identified in satellite images on 11 March. Images acquired on 6 and 16 March were cloudy or mostly cloudy.

Geological summary: The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. It has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The Mendana cone is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Recorded eruptions have frequently originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Ubinas, Peru

16.345°S, 70.8972°W; summit elev. 5608 m

Instituto Geofísico del Perú (IGP) reported that lahars on the SE flank of Ubinas descended through the Volcánmayo drainage towards the Ubinas River at 1507 on 13 March and at 1454 on 17 March. The public was warned to stay away from the drainage and to avoid driving on the Querapi-Ubinas-Huarina highway.

Geological summary: The truncated appearance of Ubinas, Perú’s most active volcano, is a result of a 1.4-km-wide crater at the summit. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45°. The steep-walled, 150-m-deep summit crater contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

References:

¹ Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report – March 13 – 19, 2024 – Managing Editor: Sally Sennert

Featured image credit: TW

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