The Weekly Volcanic Activity Report: May 22 – 28, 2024


New activity/unrest was reported for 9 volcanoes from May 22 to 28, 2024. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Dempo, Indonesia | Ibu, Indonesia | Kelimutu, Indonesia | Reykjanes, Iceland | Sheveluch, Russia | Suoh, Indonesia | Tofua, Tonga | Ubinas, Peru | Whakaari/White Island, New Zealand.

Ongoing activity: Aira, Japan | Cotopaxi, Ecuador | Dukono, Indonesia | Ebeko, Russia | Fuego, Guatemala | Great Sitkin, United States | Kanlaon, Philippines | Kerinci, Indonesia | Lewotobi, Indonesia | Lewotolok, Indonesia | Marapi, Indonesia | Merapi, Indonesia | Purace, Colombia | Sabancaya, Peru | Santa Maria, Guatemala | Suwanosejima, Japan.

New activity/unrest

Dempo, Indonesia

4.016°S, 103.121°E; summit elev. 3142 m

PVMBG reported that an eruption at Dempo occurred at 0406 on 27 May. A video posted with the report showed a Surtseyan eruption at the crater lake with dark material being ejected 300 m from the center of the lake. Dense white-and-gray ash plumes rose around 500 m and drifted W. According to a news report, the crater lake water had been changing colors during the previous few weeks. The color changed from turquois-green to gray and white on 9 May, and a diffuse gas-and-steam plume was visible. A seismic signal indicating an emission was recorded at 1911 on 12 May. The water turned turquois-green again on 15 May and then to gray on 17 May. The Alert Level remained at 2 (on a scale of 1-4), and the public were reminded to stay 1 km away from the crater and as far as 2 km on the N flank.

Geological summary: Dempo is a stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3-km-wide amphitheater open to the north. The high point of the older Gunung Dempo crater rim is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within the older crater. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The active 750 x 1,100 m active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake at the far NW end. Eruptions recorded since 1817 have been small-to-moderate explosions that produced local ashfall.

Ibu, Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

PVMBG reported that the eruption at Ibu continued during 22-28 May. White steam-and-gas plumes rose 200-600 m above the crater rim and drifted in multiple directions during 22-25 and 28 May. White-and-gray ash plumes rose 200-500 m and drifted SW, W, and N on 26 May. At 0303 on 27 May an eruptive event produced a white, gray, and black ash plume that rose 6 km above the crater rim and drifted SW and W. According to a news article ash fell in residential areas and at the Ibu observation post (9 km W). Incandescent material was ejected as far as 1 km from the vent onto the NW, W, SW, and S flanks. The Alert Level remained at 4 (the highest level on a four-level scale) and the public was advised to stay 4 km away from the active crater and 7 km away from the N crater wall opening.

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.

Kelimutu, Indonesia

8.77°S, 121.82°E; summit elev. 1639 m

PVMBG reported that on 17 May the color of the crater lake water in Kelimutu’s Crater I (Tiwu Ata Polo) changed from green to dark green, water bubbles on the surface of the NE part of the lake were observed, and there was a weak sulfur odor. On 22 May the water color changed to a blackish-brown. The lake temperature dropped from 23 to 21 degrees Celsius during 17-22 May. At Crater II (Tiwu Koofai Nuwamuri) the water color was light blue on 17 May and had not changed color since the last visual observation. Golden-yellow sulfur deposits were scattered around the lake including in the central part and in areas to the NW, N, NE, E, and SE. Visual observations on 23 May revealed that the lake’s color had not changed, though sulfur deposits had shifted positions and had become more numerous. There was a swirling area of sulfur deposits on the water’s surface at the S part of the lake and a weak sulfur odor was noted. The lake temperature increased from 22 to 24 degrees Celsius during 17-23 May, indicating increased activity of the magmatic-hydrothermal system beneath it. The color of the lake water in Crater III (Tiwu Ata Bupu) was unchanged during 17-23 May. The changes in lake water color at Crater I, along with the changes in the floating sulfur deposits and increased water temperatures at Crater II, prompted PVMBG to raise the Alert Level to 2 (on a scale of 1-4) at 1300 on 24 May, and the public was warned to stay 250 m from the crater rims. According to a news article the Taman Nasional Kelimutu (Kelimutu National Park) restricted visitors from approaching the craters in accordance with the PVMBG guidelines. The last eruption was phreatic, and it occurred at Crater II during June 1968.

Geological summary: Kelimutu is a small, but well-known, Indonesian compound volcano in central Flores Island with three summit crater lakes of varying colors. The western lake, Tiwi Ata Mbupu (Lake of Old People) is commonly blue. Tiwu Nua Muri Kooh Tai (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched, or Enchanted Lake), which share a common crater wall, are commonly colored green and red, respectively, although lake colors periodically vary. Active upwelling, probably fed by subaqueous fumaroles, occurs at the two eastern lakes. The scenic lakes are a popular tourist destination and have been the source of minor phreatic eruptions in historical time. The summit is elongated 2 km in a WNW-ESE direction; the older cones of Kelido (3 km N) and Kelibara (2 km S).

Reykjanes, Iceland

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

IMO reported that seismicity increased on 28 May in an area near the Sundhnúkagígar crater row and, along with continuing inflation, possibly indicated rising magma within the Reykanes volcanic system. According to news articles seismicity intensified during the morning of 29 May, prompting the evacuation of workers at the Svartsengi power plant, 35-38 residents of Grindavík (three remained), and visitors and residents at the Blue Lagoon spa area. At 1109 on 29 May IMO reported that the seismic swarm was likely related to a new dike intrusion. The Aviation Color Code was raised to Red (the highest level on a four-color scale) and then decreased back to Orange at 1115 because no additional geophysical data indicated significant changes. An effusive eruption began at 1246 near Sundhnúk, NE of Sýlingarfell, with the propagation of a 1-km-long fissure that produced lava fountains at least 30-50 m high and dense, gas-rich plumes rose along the fissure. Radar data indicated that particulates were present in the plume up to 2 km and gases rose as high as 3 km. By 1415 lava had advanced about 1 km W and to the S, towards Grindavík road. A second fissure opened just W of the main fissure and eruption plumes rose as high as 3.4 km. The extrusion rate was estimated to be 1,500-2,000 cubic meters per second. The fissure continued to propagate and by 1450 it was 3.4 km long. Lava surrounded Hagafell to the E and advanced S towards Melhólsnáma based on an overflight conducted by the Coast Guard. The southernmost part of the fissure was less than 1 km from the lava barriers N of Grindavík, and lava flowed over Grindavík road.

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.

Sheveluch, Russia

56.653°N, 161.36°E; summit elev. 3283 m

KVERT reported that the Karan-1 lava dome on Sheveluch’s SW flank continued to grow during 16-23 May. Thermal anomalies over both the new and older lava domes were identified in satellite images during 17, 19-21, and 23 May; the dome was obscured by weather clouds on the other days. 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.

Suoh, Indonesia

5.25°S, 104.27°E; summit elev. 1000 m

PVMBG reported that a phreatic eruption at Suoh’s Nirwana Crater occurred at 0830 on 24 May and produced a dense white steam plume; two more phreatic explosions occurred within the following half hour. According to BNPB the first event ejected sediment, the second event ejected sediment-laden water, and the third produced a dense black plume. Loud booming was heard within a radius of several kilometers. During a field visit, scientists noted that pebble-sized material had been ejected and temperatures around the vent were higher. The public was warned to stay 500 m away from Nirwana Crater and to avoid Suah’s craters and associated drainages due to potentially elevated levels of carbon dioxide. Very minor hydrothermal explosions took place in 1994; large phreatic explosions last occurred in 1933.

Geological summary: The 8 x 16 km Suoh (or Suwoh) depression appears to have a dominantly tectonic origin, but contains a smaller complex of overlapping calderas oriented NNE-SSW. Historically active maars and silicic domes lie along the margins of the depression, which falls along the Great Sumatran Fault that extends the length of the island. Numerous hot springs occur along faults within the depression, which contains the Pematang Bata fumarole field. Large phreatic explosions (0.2 km2 tephra) occurred at the time of a major tectonic earthquake in 1933. Very minor hydrothermal explosions produced two 5-m-wide craters at the time of a February 1994 earthquake.

Tofua, Tonga

19.75°S, 175.07°W; summit elev. 515 m

At 0900 on 23 May Tonga Geological Services reported that elevated activity at Tofua had ceased during the previous week. The characteristics of a thermal anomaly identified in a satellite image indicated a return to baseline levels. The Aviation Color Code was lowered to Green (the lowest color on a four-color scale), the Maritime Alert Level was lowered to Green (the lowest level on a four-color scale), and the Alert level for residents of Vava’u and Ha’apai remained at Green (the lowest color on a four-color scale).

Geological summary: The low, forested Tofua Island in the central part of the Tonga Islands group is the emergent summit of a large stratovolcano that was seen in eruption by Captain Cook in 1774. The summit contains a 5-km-wide caldera whose walls drop steeply about 500 m. Three post-caldera cones were constructed at the northern end of a cold fresh-water caldera lake, whose surface lies only 30 m above sea level. The easternmost cone has three craters and produced young basaltic-andesite lava flows, some of which traveled into the caldera lake. The largest and northernmost of the cones, Lofia, has a steep-sided crater that is 70 m wide and 120 m deep and has been the source of historical eruptions, first reported in the 18th century. The fumarolically active crater of Lofia has a flat floor formed by a ponded lava flow.

Ubinas, Peru

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

Instituto Geofísico del Perú (IGP) reported that thermal anomalies from the main crater floor at Ubinas were identified daily during 21-28 May, except during 22-23 May. Daily gas-and-steam plumes rose as high as 900 m above the crater rim. The Alert Level remained at Yellow (the second level on a four-color scale) and the public was warned to stay 2 km away from the crater.

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.

Whakaari/White Island, New Zealand

37.52°S, 177.18°E; summit elev. 294 m

GeoNet reported that a minor eruption at Whakaari/White Island occurred at around 0820 on 24 May and produced a vigorous steam-and-gas plume that rose 2-3 km high. There was no clear indication of ash in the plume at the time, based on webcam images. The Volcanic Alert Level was raised to 3 (on a scale of 0-5) and the Aviation Color Code was raised to Orange (the third level on a four-color scale). Steam emissions had returned to normal conditions by 1045. During an overflight of the island later that day scientists observed ash deposits downwind, on the N part of the island. Geysering at the crater lake that had been ongoing for months was stronger, ejecting material 20-30 m high for periods of several seconds. The vent area was obscured by gas-and-steam emissions. The level of the crater lake had subsided and exposed parts of the lake floor. The eruption was much smaller than the December 2019 eruption. At 1700 the Volcanic Alert Level was lowered back down to 2 and the Aviation Color Code was lowered back to Yellow. GeoNet noted that there were no instruments on the island and therefor a lack of real-time monitoring data; monitoring was conducted with a webcam located in Whakatane, satellite images, and observational and gas measurement overflights.

A second minor eruption occurred at 0810 on 25 May, again prompting GeoNet to raise the Volcanic Alert Level to 3 and the Aviation Color Code to Orange. The eruption produced a vigorous steam-and-gas plume that rose above the island, similar to the day before. There were no clear indications of ash in the plume based on the webcam view. According to the Wellington VAAC ash was not identifiable in a satellite image from 1107 on 25 May. In a statement issued at 1445, GeoNet noted that intermittent ejections of gas and steam continued to be visible throughout the day. No further activity was observed over the next few days; the Volcanic Alert Level was lowered to 2 and the Aviation Color Code was lowered to Yellow at 1500 on 29 May. GeoNet noted that analysis of data collected during a 27 May overflight indicated elevated levels of magmatic gas compared to previous observations in April and early May.

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.

Ongoing activity

Aira, 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 20-24 May with nighttime crater incandescence. A total of five eruptive events and two explosions were recorded. The first explosion, at 0121 on 20 May, produced an ash plume that rose 2.3 km above the crater rim and drifted W. Large blocks were ejected 800-1,100 m from the vent. The second explosion, at 1718 on 22 May, generated an ash plume that rose 3 km and drifted NW. Large blocks were again ejected 800-1,100 m from the vent. Eruptive events at 1442, 1520, 1615, and 1710 on 20 May and at 0823, 2110, and 2230 on 24 May generated ash plumes that rose 1-1.3 km and drifted SE, S, and SW. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 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.

Cotopaxi, Ecuador

0.677°S, 78.436°W; summit elev. 5911 m

IG-EPN reported that monitoring instruments began recording signals at 1510 on 23 May indicating that a moderately-sized secondary lahar was descending Cotopaxi’s NW flank. The public was advised to stay away from stream and river drainages within the vicinity of Parque Nacional Cotopaxi (Cotopaxi National Park).

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

Dukono, Indonesia

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

PVMBG reported that the eruption at Dukono was ongoing during 22-28 May. Gray-and-white ash plumes rose 100-1,100 m above the summit and drifted E, SW, and W on most days; weather conditions prevented views on 28 May. 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, Russia

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

KVERT reported that moderate explosive activity was ongoing at Ebeko during 17-23 May According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions on 17 May generated ash plumes that rose as high as 2 km (6,600 ft) a.s.l. and drifted NE. A thermal anomaly was identified in satellite images on 17 and 22 May; on other days either no activity was observed or weather conditions prevented views. 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.

Fuego, Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

INSIVUMEH reported that eruptive activity continued at Fuego during 21-28 May. Explosions were recorded daily, averaging 1-10 per hour on most days, when counts were reported. The explosions generated gas-and-ash plumes that rose as high as 1.1 km above the crater rim and drifted as far as 30 km W, SW, and S. Frequent block avalanches descended various drainages including the Ceniza (SSW), Seca (W), Taniluyá (SW), and Las Lajas (SE), Honda (E), and Trinidad (S), and sometimes reached vegetated areas. Weak rumbling sounds and shock waves that rattles nearby houses and buildings were reported on most days. Ashfall was reported on almost all days in areas downwind including El Porvenir (11 km SW), El Rodeo, Finca Palo Verde, Sangre de Cristo (8 km WSW), Santa Sofía (12 km SW), Los Yucales (12 km SW), Panimaché I and II (8 km WSW), and Morelia (9 km SW), Finca La Asunción (12 km SW), La Rochela (8 km SSW), Finca Ceilán (9 km S), and San Andrés Osuna (11 km SSW). Ashfall was forecasted for areas downwind during 26-27 May. The explosions also ejected incandescent material up to 400 m above the summit on most days. Weather conditions sometimes prevented visual observations.

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, United States

52.076°N, 176.13°W; summit elev. 1740 m

AVO reported that slow lava effusion in Great Sitkin’s summit crater was last confirmed in a 22 May radar satellite image with continuing inflation over the vent and advancement of the NW lava lobe. Lava was filling in a crack just SW of the vent. Effusion likely continued during 23-28 May. Seismicity was low and characterized by small, long-period and volcano-tectonic earthquakes. Weather clouds fully or partly obscured satellite and webcam views on most days. 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.

Kanlaon, Philippines

10.412°N, 123.132°E; summit elev. 2435 m

In a special notice for Kanlaon, PHIVOLCS stated that the seismic network detected 24 volcano-tectonic earthquakes during 1335-1630 on 26 May with local magnitudes of 0.8-2.3 and depths of 0-6 km beneath the W flank. Sulfur dioxide gas emissions from the summit crater had been elevated since 1 January, averaging 1,291 tonnes/day (t/d); the most recent measurement was 2,003 t/d, recorded on 26 May. Ground deformation data from continuous GPS and electronic tilt data had been recording inflation at the volcano since March 2022. The Alert Level remained at 1 (on a scale of 0-5) and PHIVOLCS reminded the public to remain outside of the 4-km-radius Permanent Danger Zone.

Geological summary: Kanlaon volcano (also spelled Canlaon) forms the highest point on the island of Negros, Philippines. The massive andesitic stratovolcano is covered with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller but higher active vent, Lugud crater, to the south. Eruptions recorded since 1866 have typically consisted of phreatic explosions of small-to-moderate size that produce minor local ashfall.

Kerinci, Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

The Darwin VAAC reported that at 1040 on 28 May an ash plume from Kerinci was identified in a satellite image drifting SW at 5.8 km (19,000 ft) a.s.l., or 2 km above the summit. PVMBG noted that white steam-and-gas plumes rose 200 m above the summit that same day. The Alert Level remained at 2 (on a scale of 1-4) and the public was reminded to stay 3 km away from the crater.

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.

Lewotobi, Indonesia

8.542°S, 122.775°E; summit elev. 1703 m

PVMBG reported that eruptive activity at Lewotobi’s Laki-laki volcano continued during 22-28 May. Gray-and-white ash plumes rose 100-800 m above the summit and drifted N, SW, and W during 22-25 May. White steam-and-gas plumes rose as high as 100 m above the summit and drifted W and SW during 26-27 May. The seismic network recorded daily eruptive events during 23-28 May, though there was no visual confirmation. The Alert Level remained at 2 (the second lowest level on a scale of 1-4) and the public was warned to stay outside of the exclusion zone, defined as a 2-km radius around Laki-laki crater, 3 km to the NNE, and 5 km on the NE flanks.

Geological summary: The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the “husband and wife”). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.

Lewotolok, Indonesia

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

PVMBG reported that the eruption at Lewotolok continued during 22-28 May. White steam-and-gas plumes rose 200-700 m above the summit and drifted W and NW. On 25 May white-and-gray ash plumes rose as high as 500 m and drifted W and NW. At 0635 on 27 May a dense gray-to-black ash plume rose 300 m and drifted W. According to a news report the lava flow on the W flank advanced 100 m to a total length of 1.3 km by 27 May; the advancement rate had slowed during the period weeks. The Alert Level remained at 3 (on a scale of 1-4) and visitors and residents of Lamawolo, Lamatokan, and Jontona were warned to stay 2 km away from the vent and 3 km away from the vent on the S and SE flanks.

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, Indonesia

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

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 22-28 May. White gas-and-steam plumes rose 200-300 m above the summit and drifted SW, S, and SE on most days; no emissions were visible on 22 May. At 0350 on 26 May a dense gray ash plume rose around 1 km above the summit and drifted S. A webcam image showed incandescence at the crater. 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, Indonesia

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

BPPTKG reported that the eruption at Merapi (on Java) continued during 17-23 May. Seismicity had decreased compared to the previous week. The SW lava dome produced 138 lava avalanches that traveled as far as 1.9 km down the Bebeng drainage on the SW flank. Morphological changes to the SW lava dome 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.

Purace, Colombia

2.32°N, 76.4°W; summit elev. 4650 m

Observatorio Vulcanológico y Sismológico de Popayán, Servicio Geologico Colombiano (SGC) reported that seismic activity at Puracé decreased during 21-24 May and continued to be at pre-29 April levels. Both volcanic tremor (VT) associated with rock fracturing and long-period (LP) events associated with fluid movement were located less than 2.5 km beneath Puracé crater and had low magnitudes. Gas emissions from the crater and the N flank fumarole were occasionally visible in webcam views. Both the number and magnitude of LP events increased during 24-25 May. The events may have been associated with gas emissions with minor amounts of ash, but weather conditions prevented visual confirmation. Later that afternoon gas emissions from the crater and the fumaroles on the upper N flank were visible in webcam images. During 25-26 May LP events decreased in both number and size and seismicity associated with rock fracturing slightly increased. The earthquakes were located at depths of less then 3 km. LP seismicity was at stable levels and VT seismicity slightly decreased during 26-27 May, and both types of seismicity decreased during 27-28 May; events were located at depths less than 2 km. Gas emissions were observed in webcam views. Both carbon dioxide and sulfur dioxide emissions remained above baseline levels during the week. The Alert Level remained at Orange (the second highest level on a four-color scale).

Geological summary: Puracé in Colombia consists of an andesitic stratovolcano with a 500-m-wide summit crater constructed over a dacitic shield volcano. It lies at the NW end of a volcanic massif opposite Pan de Azúcar stratovolcano, 6 km SE. A NW-SE-trending group of seven cones and craters, Los Coconucos, lies between the two larger edifices. Frequent explosive eruptions in the 19th and 20th centuries have modified the morphology of the summit crater. The largest eruptions occurred in 1849, 1869, and 1885.

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 20-26 May with a daily average of 40 explosions. Gas-and-ash plumes rose as high as 2.5 km above the summit and drifted less than 10 km E and NE. 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). Sulfur dioxide emissions were at moderate levels, averaging 541 tons per day. The Alert Level remained at Orange (the third level on a four-color scale) and the public was 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 observed eruptions date back to 1750 CE.

Santa Maria, Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava-dome complex during 21-28 May with continuing lava extrusion and block collapses and avalanches at the Caliente dome. Sometimes the avalanches are audible several kilometers away. Incandescence from the dome was visible during most nights and early mornings, and occasional incandescence was also present along the upper parts of the lava flow on the WSW flank. Daily explosions (a few per hour) generated gas-and-ash plumes that rose 700-1,400 m above the summit and drifted E, SE, SW, and W. The explosions produced block avalanches on the dome’s flanks and generated occasional short-range pyroclastic flows that descended multiple flanks. The ash plumes caused hazy conditions around the volcano during 22-23 and 27-28 May.

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 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 E 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.

Suwanosejima, Japan

29.638°N, 129.714°E; summit elev. 796 m

JMA reported that eruptive activity at Suwanosejima’s Ontake Crater continued during 20-27 May. Crater incandescence was observed nightly in webcam images. An explosion at 0019 on 22 May generated an ash plume that rose 900 m above the crater rim and drifted W. The Alert Level remained at 2 (on a 5-level scale) and the public was warned to stay at least 1.5 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.


1 Smithsonian Institution / US Geological Survey – Weekly Volcanic Activity Report – May 22 – 28, 2024 – Managing Editor: Sally Sennert.


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