The Weekly Volcanic Activity Report: May 1 - 7, 2024

New activity/unrest was reported for 6 volcanoes from May 1 to 7, 2024. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest

Poas, Costa Rica

10.2°N, 84.233°W | Summit elev. 2697 m

OVSICORI-UNA reported continuing and sometimes vigorous gas-and-steam emissions from vents on the crater floor at Poás during 30 April-7 May. Daily emissions at Boca C contained variable amounts of ash, with low ash content during 3-5 May and maybe none during 5-6 May. Plumes rose as high as 300 m and drifted E, SW, and W. Incandescence at both Boca A and Boca C was periodically visible at night.

Geological summary: The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world’s most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Purace, Colombia

2.32°N, 76.4°W | Summit elev. 4650 m

Observatorio Vulcanológico y Sismológico de Popayán, Servicio Geologico Colombiano (SGC) reported that the number of both volcanic tremor (VT) and long-period (LP) seismic events at Puracé increased during 23-29 April. The events had low magnitudes and were located at depths of 0-5 km; the VT events were located beneath the Puracé, Piocollo, and Curiquinga cones. Sulfur dioxide emissions had increased in the previous few weeks and carbon dioxide emissions continued to be above baseline levels at a fumarole on the N crater rim. Slow deformation which began in April 2022 between Puracé and Curiquinga was ongoing.

Both the number and intensity of earthquake events suddenly increased during 29-30 April. Seismicity continued to be elevated during 1-3 May and, along with continuing deformation and increases in gas emissions and other monitoring data, the activity was sustained at a higher level. On 3 May the Alert Level was raised to Orange (the second highest level on a four-color scale). During 3-4 May gas-and-steam emissions rose 1.4 km above the summit and drifted W. Seismicity during 3-6 May continued to increase; VT events were mainly located beneath Puracé at depths less than 4 km and LP events were located beneath the crater and the N flank at depths less than 1 km. Additionally, very low-magnitude events indicating rising magma were located at depths of 1-3.5 km beneath Piocollo and Curiquinga.

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.

Ruang, Sangihe Islands

2.3°N, 125.37°E | Summit elev. 725 m

PVMBG reported that seismicity at Ruang during 1-2 May was characterized by continuous tremors along with both deep and shallow volcanic earthquakes. The number of seismic events was decreasing based on a seismic station at the Ruang Post, 5 km from the crater; two closer stations, 1.5 and 2.7 km from the crater, had been damaged by eruptions. During 1-4 and 7 May white-and-gray ash plumes that were sometimes dense rose 100-700 m above the summit and drifted in multiple directions. Dense white steam-and-gas plumes rose 100-450 m above the summit and drifted NE, E, and S during 5-7 May.

On 5 May PVMBG reduced the exclusion zone from a 7 km radius around the active crater to 5 km. According to news reports a total of 5,849 residents of Tagulandang Island had been evacuated by 5 May; additional evacuations were halted after the exclusion zone was changed. The Sam Ratulangi International Airport (98 km SW in Manado, North Sulawesi) reopened on 5 May, though several airports remained closed including Djalaludin Airport in Gorongtalo, Siau Airport in the Sitaro Islands, Naha Airport in the Sangihe Islands, Lolakndi Bolaang Mongondow Airport, Miangas Airport, and Melonguane Airport in the Talaud Islands. The Alert Level remained at 4 (the highest level on a scale of 1-4).

Geological summary: Ruang volcano is the southernmost volcano in the Sangihe Island arc, north of Sulawesi Island; it is not the better known Raung volcano on Java. The 4 x 5 km island volcano is across a narrow strait SW of the larger Tagulandang Island. The summit contains a crater partially filled by a lava dome initially emplaced in 1904. Explosive eruptions recorded since 1808 have often been accompanied by lava dome formation and pyroclastic flows that have damaged inhabited areas.

Sheveluch, Central Kamchatka (Russia)

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

The Kamchatka Volcanological Station reported that seismicity at Sheveluch began increasing on 24 April. According to KVERT a new lava dome, named Karan-1, began to grow on the SW flank at around 0200 local time on 27 April based on the intensification of thermal anomalies detected in satellite observations. During 27 April-3 May intense steam-and-gas emissions rose from the active area and on 28 April an ash plume drifted about 25 km NW. Kamchatka Volcanological Station noted that an ash plume rose 2 km on 30 April. Lava-dome incandescence was occasionally visible during the week in webcam images and a daily intense thermal anomaly over the dome complex was identified in satellite images. 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.

Tofua, Tonga Ridge

19.75°S, 175.07°W | Summit elev. 515 m

Tonga Geological Services reported that unrest at Tofua continued during 1-7 May. Thermal anomalies with varying intensities were detected daily. Sulfur dioxide plumes from the 28 April emission event continued to be identified in satellite data during 1-2 May. The Aviation Color Code was raised to Yellow (the second lowest color on a four-color scale) on 2 May; the Maritime Alert Level remained at Orange (the second highest level on a four-color scale); mariners were advised to stay 2 km away from the island; 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 Ubinas main crater were identified during 5-6 May. At 0516 on 6 May an ash plume rose 2.1 km above the crater rim and drifted more than 10 km SE. Ashfall was reported in the towns of Ubinas (6.5 km SSE), Tonohaya (7 km SSE), Anascapa (11 km SE), San Miguel (10 km SE), Huarina, and Matalaque (17 km SSE). 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.

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 29 April-6 May with nighttime crater incandescence. A very small eruptive event was recorded on 3 May. An explosion at 2131 on 5 May ejected blocks 600-900 m from the vent and produced an ash plume that rose 1.3 km above the crater rim, drifted N, and merged into weather clouds. 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.

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 25 April-3 May According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 27-28 and 30 April, and 1-2 May, generated ash plumes that rose as high as 3 km (10,000 ft) a.s.l. and drifted SW, SE, and NE. A thermal anomaly was identified in satellite images on 30 April; 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.

Fernandina, Isla Fernandina (Galapagos)

0.37°S, 91.55°W | Summit elev. 1476 m

Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN) reported that the eruption at Fernandina continued. The amount of lava flowing into the ocean significantly increased during 25-30 April and the lava flows spread along 800 m of the coastline. During 30 April-7 May daily thermal anomalies from the lava flow were identified in satellite images and gas-and-steam emissions rose from the area where lava entered the ocean. Sulfur dioxide emissions, measured using satellite data, fluctuated between about 205 and 803 tons per day during the first half of the week.

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.

Fuego, South-Central Guatemala

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

INSIVUMEH reported that eruptive activity continued at Fuego during 30 April-7 May. Explosions were recorded daily, averaging 2-10 per hour on most days, when counts were reported. The explosions generated gas-and-ash plumes that rose as high as 1.2 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 were reported on most days. On a few of the days ashfall was reported 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). The explosions also ejected incandescent material up to 300 m above the summit on most days.

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 slow lava effusion in Great Sitkin’s summit crater was last confirmed in a 30 April radar satellite image; effusion likely continued during 30 April-7 May. Seismicity was low. Weather clouds fully or partly obscured satellite and webcam views, though minor steaming from the vent area was observed in satellite images during 30 April-2 May. 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.

Ibu, Halmahera

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

PVMBG reported that Ibu continued to erupt. A few notable eruptive events occurred during 24-29 April. On 24 April ash plumes rose 800-1,500 m above the summit and roaring was heard at the Ibu observation post (9 km W). On 26 April an eruptive event produced a dense gray ash plume that rose 2 km and drifted SW and W, incandescence that emanated about 700 m from the summit, a boom followed by a roaring noise, and ashfall in residential areas downwind. At 0037 on 28 April an ash plume rose 3.5 km and produced lightning in the plume. Booming and roaring was heard at the observation post and ash fell in residential areas to the W. At 2137 on 29 April a dense gray ash plume rose around 1 km and drifted W and NW; incandescent material was ejected 500 m NW, W, and SW. Booming and rumbling was heard at the observation post. During 1-2 and 5 May dense gray or gray-and-white ash plumes rose as high as 2 km and drifted in multiple directions. White steam-and-gas plumes rose as high as 300 m and drifted E, SE, and S on 4 May. An eruptive event was recorded by the seismic network on 6 May but was not visually confirmed. The Alert Level remained at 2 (the second highest level on a four-level scale) and the public was advised to stay 3.5 km away from the active crater.

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.

Lewotobi, Flores Island

8.542°S, 122.775°E | Summit elev. 1703 m

PVMBG reported that gray-to-white ash plumes rose 100-500 m above the summit of Lewotobi’s Laki-laki volcano and drifted in multiple directions during 30 April-5 May. The plumes were sometimes dense. Eruptive events were recorded by the seismic network on 6 May, though no emissions were reported. 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, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 1-7 May. White steam-and-gas plumes rose 100-700 m above the summit and drifted W and NW on most days. Gray-to-black ash plumes rose 300-500 m and drifted W on 6 May. 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, Central Sumatra

0.38°S, 100.474°E | Summit elev. 2885 m

PVMBG reported that eruptive activity at Marapi (on Sumatra) was ongoing during 1-7 May. White steam-and-gas plumes rose 200-300 m above the summit and drifted multiple directions almost every day. White-and-gray ash plumes rose 250-300 m above the summit and drifted E and SE on 6 May. 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 26 April-2 May. Seismicity had declined compared to the previous week. The SW lava dome produced 113 lava avalanches that traveled as far as 2 km down the SW flank. Morphological changes to the SW lava dome were due to continuing effusion and collapses of material. The volume of the SW dome was an estimated 2,171,300 cubic meters and the dome in the main crater was stable at an estimated 2,358,200 cubic meters based on a 24 April drone survey and webcam images. The highest temperature of the SW dome was around 215 degrees Celsius, higher than the previous measurement. 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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W | Summit elev. 5279 m

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 30 April-6 May. The number of seismic events associated with fluid movement remained stable at low-to-moderate levels, though the signal increased in magnitude. Some of these signals were associated with pulsating emissions of ash and gas; ash plumes rose as high as 2 km above the summit on 30 April and drifted NW and WNW. Seismicity associated with rock fracturing was stable in both the number and magnitude of events; these earthquakes at depths less than 5 km below the summit were primarily located within 5 km of Arenas Crater, particularly to the E. The largest event was an M 1.2 which was detected at 1842 on 1 May. Several thermal anomalies on the crater floor were identified in satellite data, though weather conditions often inhibited views. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America’s deadliest eruption.

Reykjanes, Reykjanes Peninsula

63.817°N, 22.717°W | Summit elev. 140 m

On 7 May IMO reported that the cone just E of Sundhnúk and along the fissure within the Reykanes volcanic system continued to erupt lava, though activity had decreased during the previous few days. Lava flowed short distances from the vent; no significant changes were observed at the S part of the flow field near the earthen barriers at Grindavík. Inflation from magma accumulation beneath Svartsengi was first detected at the beginning of April and the rate of inflation was unchanged for the past few weeks based on modeling of GPS and satellite data. Seismicity increased steadily during the past week. Most of the earthquakes were below M 1 and located N of the vent between Sundhnúk and Stóra Skógfell, S of Mt. Thorbjorn in a valley near Grindavík, and in an area between the vent and Grindavík.

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.

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 29 April-5 May with a daily average of 36 explosions. Gas-and-ash plumes rose as high as 2.5 km above the summit and drifted less than 10 km E, SE, 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). Sulfur dioxide emissions were at moderate levels, averaging 478 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, Southwestern 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 30 April-7 May with a lava extrusion and blocks avalanches at the Caliente dome. 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 (1-5 per hour on most days) generated gas-and-ash plumes that rose 600-1,400 m above the summit and drifted as far as 25 km W, SW, S. The explosions produced block avalanches on the dome’s flanks and generated occasional short-range pyroclastic flows that descended multiple flanks. Block avalanches from collapses at the dome and at the margins of the upper part of the lava flow were sometimes audible several kilometers from the volcano. Ashfall caused hazy conditions around the volcano during 2-3 April. Minor ashfall was reported in San Marcos Palajunoj (8 km SW) and Finca Pauwlonias (S) during 3-4 and 6-7 April.

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.

Semeru, Eastern Java

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

PVMBG reported that eruptive activity continued at Semeru during 1-7 May and seismicity remained at high levels. One incandescent lava avalanche traveled 800 m down the Besuk Kobokan drainage on the S flank. Eruptive events were recorded by the seismic network during 1-2 May, though plumes were not visually confirmed. Daily white-and-gray ash plumes rose 100-1,000 m above the summit and drifted in multiple directions on the other days of the week. The plumes were dense during 5-6 May. 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.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that eruptive activity at Suwanosejima’s Ontake Crater continued during 29 April-6 May. Crater incandescence was observed nightly in webcam images. Emissions rose as high as 600 m above the crater rim and blocks were ejected as far as 300 m from the crater’s center; no explosions were detected. 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.

References:

¹ Smithsonian Institution / US Geological Survey Weekly – Volcanic Activity Report – May 1 – 7, 2024 – Managing Editor: Sally Sennert.

Featured image credit: The Watchers

Related by tag and category
Related by tag
Related by category