The Weekly Volcanic Activity Report: June 7 – 13, 2023

the weekly volcanic activity report

New activity/unrest was reported for 6 volcanoes from June 7 to 13, 2023. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Ahyi, Mariana Islands (USA) | Kilauea, Hawaiian Islands (USA) | Mayon, Luzon (Philippines) | Nyamulagira, DR Congo | Popocatepetl, Mexico | Rincon de la Vieja, Costa Rica.

Ongoing activity: Aira, Kyushu (Japan) | Cotopaxi, Ecuador | Ebeko, Paramushir Island (Russia) | Great Sitkin, Andreanof Islands (USA) | Karangetang, Sangihe Islands | Krakatau, Sunda Strait | Lewotolok, Lembata Island | Merapi, Central Java | Nyiragongo, DR Congo | Reventador, Ecuador | Semeru, Eastern Java | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Taal, Luzon (Philippines).

New activity/unrest

Ahyi, Mariana Islands (USA)

20.42°N, 145.03°E | Summit elev. -75 m

Unrest at Ahyi Seamount continued during 6-12 June. Possible hydroacoustic signal was detected by pressure sensors on Wake Island (2,270 km E) during 6-8 June, and multiple hydroacoustic signals were detected during 9-11 June. No surface activity was visible in partly cloudy and partly clear satellite images. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological summary: Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Kilauea, Hawaiian Islands (USA)

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

A new eruption at Kilauea began at 0444 on 7 June with the burst of tall lava fountains from a vent on the central part of the Halema’uma’u Crater floor. The Volcano Alert Level was raised to Warning (the highest level on a four-level scale) and the Aviation Color Code was raised to Red (the highest level on a four-color scale). Soon after, lava fountains were active along multiple fissures on the crater floor, and along one fissure that bisected the SW crater wall. Between 0800-0900 the sulfur dioxide emission rate was about 65,000 tonnes per day. Residents of Pahala, 30 km downwind of the summit, reported minor deposits of fine gritty ash and Pele?s hair. Lava flows inundated the crater floor (about 1.5 square km) and added about 6 m depth of new lava within a few hours. A small spatter cone had formed at the vent on the SW wall by midday, and lava from the cone was flowing into the active lava lake below. Fountain heights had decreased from the onset of the eruption and were 4-9 m high by 1600, with occasional higher bursts. Inflation switched to deflation and summit earthquake activity greatly diminished shortly after the eruption onset.

At 0837 on 8 June HVO lowered the Volcano Alert Level to Watch and the Aviation Color Code to Orange because the initial high effusion rates had declined, and no infrastructure was threatened. The lava lake had dropped by about 2 m likely due to gas loss by the morning of 8 June. The drop left a wall of cooled lava around the margins of the crater floor. Multiple lava fountains were active in the central E part of the lake and fountains rose as high as 10 m. The spatter cone continued to build over the SW wall vent; lava flows from the vent fed the SW part of the lava lake. The preliminary average effusion rate for the first 24 hours of the eruption was about 150 cubic meters per second, though the estimate did not account for vesiculated lava and variations in crater floor topography. The effusion rate during the very earliest phases of the eruption appeared to be significantly higher than the previous three summit eruptions based upon the rapid coverage of the entire crater floor.

During 8-9 June multiple lava fountains remained active and rose up to 10 m high. The SW wall vent continued to effuse lava into the crater lake which had increased in depth by about 1.5 m. Active lava and vents covered much of the W half of the crater floor, arranged in a broad horseshoe shape around a central uplifted area. This feature in the basin of the 2021-22 lava lake was described as the “western lava lake” from prior eruptions and had reactivated along with a smaller circular pool just SE of the lake. An active lava lake centered within the uplifted area was fed by a vent in its NE corner. A much smaller area of lava was active in the E portion of the crater floor. The sulfur dioxide emission rate was about 11,000 tonnes per day on 9 June and about 8,900 tonnes per day on 10 June.

During 10-12 June multiple lava fountains remained active and were up to 9 m high, and the SW wall vent continued to effuse lava into the crater lake. The active features in the E portion of the lake had stagnated during 10-11 June. Sulfur dioxide emissions averaged 7,400 tonnes per day on 11 June. The W part of the lake rose about 1 m during 11-12 June, likely due to the construction of a levee around the pond. Gas plumes rose to 2.4-3 km (8,000-10,000 ft) a.s.l. and were trapped under a weather inversion layer. Activity decreased during 12-13 June and only a few small lava fountains were active. The western lake and the smaller lava pond in the central portion of the crater floor remained active, along with the vent on the SW wall.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Mayon, Luzon (Philippines)

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

PHIVOLCS reported that the rate of lava-dome extrusion at Mayon’s summit crater increased, leading to an Alert Level increase and evacuations. Sulfur dioxide emissions were at or near baseline levels of 500 tonnes per day, averaging 574 and 332 tonnes per day on 6 and 7 June, respectively. The total number of rockfalls increased from 54 during 1-4 June to 267 during 5-8 June. Additionally, the volumes of the individual rockfall events became larger on 3 June. The rockfalls were generated by partial collapses of the growing lava dome and indicated an increasing extrusion rate. Three pyroclastic density currents (PDCs, or pyroclastic flows) were recorded at 0618, 0953, and 1100 on 8 June, each lasting 4-5 minutes based on the seismic signals. The PDCs traveled as far as 2 km down the Mi-Isi (S), Bonga (SE), and Basud (E) drainages and indicated that new, less degassed lava was collapsing from the summit dome. The Alert Level was raised to 3 (on a 0-5 scale) at 1200 on 8 June and recommended the evacuation of the 6-km radius Permanent Danger Zone.

Six PDCs generated by collapses at the lava dome and 199 rockfall events were recorded during 8-9 June, based on seismic data and visual observations. Material from the rockfalls and PDCs descended the S flank within 2 km. Steam-and-gas plumes from the dome rose 800 m and drifted S, and light-brown ash plumes from the rockfalls drifted S. Minor crater incandescence from newly extruded lava and incandescent rockfalls were observed through the night. Rockfall events continued during 9-10 June with total of 59. A new dome, contacting a part of the remnant dome on the SE part of the crater floor, was visible during the morning of 10 June. Sulfur dioxide emissions increased to moderate levels, averaging 1,205 tonnes per day that same day. The DROMIC report stated that 9,314 people from 21 neighborhoods (barangays) spanning six municipalities were in evacuation centers by 10 June.

A total of 177 rockfalls traveled as far as 700 m down the S and SE flanks during 10-11 June. Plumes of steam and gas from the dome and minor ash plumes from the rockfalls descended the flanks and then drifted E and SE. Incandescence from the dome and rockfalls was visible at night. Sulfur dioxide emissions averaged 642 tonnes per day on 11 June. Lava flows emerged at about 1947 on 11 June and produced two 500-m-long lobes; lava avalanches from the ends of the flows descended the Mi-Isi, Bonga, and Basud drainages within 2 km of the summit. Effusion of the lava flows was preceded by slight inflation at the upper flanks based on tiltmeter data and accompanied by minor seismicity. During 11-12 June the monitoring network recorded 260 rockfall events, and three collapses at the dome that produced PDCs (each lasting 2-4 minutes). The lava flows continued to be active. There were 14,360 people that had evacuated by 12 June; of those, 584 people were staying in places other than evacuation centers.

During 12-13 June the monitoring network recorded 221 rockfall events and collapses at the dome that produced PDCs (each lasting 2-4 minutes). Lava continued to slowly effuse at the summit crater and collapsed material traveled 1 km down the Mi-isi and Bonga drainages. One PDC lasting two minutes was observed and detected by the seismic network. Diffuse ash from the rockfalls and steam-and-gas emissions from the dome drifted downslope and then NE. Rockfalls exposed incandescent material at the summit. By 13 June a total of 16,152 people had evacuated; of those, 15,493 people were in evacuation shelters and 659 people were staying with friends and family.

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

Nyamulagira,DR Congo

1.408°S, 29.2°E | Summit elev. 3058 m

The Observatoire Volcanologique de Goma (OVG) reported that the eruption at Nyamulagira continued at low levels during 5-11 June based on satellite images.

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.

Popocatepetl, Mexico

19.023°N, 98.622°W | Summit elev. 5393 m

CENAPRED reported that there were 35-101 daily steam-and-gas emissions, sometimes containing minor amounts of ash, rising from Popocatépetl during 6-13 June. Daily minor or moderate explosions were recorded during 6-11 June. Periods of low-to-moderate amplitude, high-frequency tremor lasting from 34 minutes to just over six hours were recorded each day. A few volcano-tectonic earthquakes with magnitudes of 1.2-2 were recorded during 6, 8, and 11-12 June. According to the Washington VAAC daily ash plumes rose 5.8-7 km (19,000-23,000 ft) a.s.l., or around as high as 1.6 km above the summit, and drifted generally drifted SE, SSE, S, and SW. Minor ashfall was reported in Hueyapan (16 km SSW), Zacualpan de Amilpas (30 SSW), Temoac (32 SSW), Jonacatepec de Leandro Valle (43 SSW), and Tetela del Volcán (18 SW), all within the Mexican state of Morelos during 11-12 June, and in Hueyapan, Yecapixtla (30 km SW), Ayala (45 km SW), and Jantetelco during 12-13 June. The Alert Level remained at Yellow, Phase Two (the middle level on a three-color scale) and the public was warned to stay 12 km away from the crater.

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Rincon de la Vieja, Costa Rica

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

OVSICORI-UNA reported that phreatic explosions continued at Rincón de la Vieja during 6-13 June, with multiple phreatic events recorded during 6-8 June. A 14-minute-long event that began at 0142 on 7 June was comprised of two pulses of gas-and-steam that rose 1 km above the crater rim. At 0942 on 8 June a plume of steam and gas rose 2.5 km above the crater rim, followed at 1810 by a moderate phreatic eruption that ejected lake water with sediment to less than 100 m above the crater rim and produced a white steam plume that rose 3 km and drifted W. Two events recorded at 0138 and 2037 on 9 June were similar in energy to the 8 June event at 1810. Gas emissions were visible on 10 June. Small phreatic events at 0357, 0521, and 0546 on 11 June produced white steam-and-gas plumes that drifted W. White steam-and-gas plumes from small phreatic events at 1031 and 1039 on 12 June rose as high as 1 km above the crater rim.

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

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported ongoing activity at both Minamidake Crater and Showa Crater (Aira Caldera’s Sakurajima volcano) during 5-12 June. Eruptive events at Showa were recorded at 0211, 0352, 0440, and 1436 on 5 June and generated ash plumes that rose as high as 1.5 km above the crater rim and sometimes drifted E and SE. Explosions at Minamidake produced ash plumes that rose 1.5 and 2.5 km above the crater rim at 0012 on 5 June and 1401 on 7 June, respectively, and ejected blocks 500-700 m from the vent. Ash-and-gas emissions were continuous with plumes rising as high as 1.5 km and then declining to 800 m during 1401-1505 on 7 June, and drifting SE. Since the volcano is so active, JMA noted that only emissions above a certain threshold of density and height get reported; at 1505 the emission characteristics declined to below that threshold. 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 Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu’s largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Cotopaxi, Ecuador

0.677°S, 78.436°W | Summit elev. 5911 m

IG reported that moderate eruptive activity continued at Cotopaxi during 6-13 June. Seismic activity was mainly characterized by long-period earthquakes and tremors associated with daily emissions; one volcano-tectonic event was recorded during 6-7 June. Small gas-and-steam emissions rose as high as 300 m above the crater rim during 6-9 June. A small lahar was detected by the seismic network on 8 June and descended the NW flank. Several daily ash-and-gas emissions were visible during 10-13 June and were continuous during part of 12 June. The plumes rose 200-600 m above the crater rim and drifted NW, W, and SW. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) maintained the Alert Level at Yellow (the second lowest level on a four-color scale).

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.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E | Summit elev. 1103 m

KVERT reported that moderate activity at Ebeko was ongoing during 1-8 June. A thermal anomaly was identified in satellite images during 2, 4, and 7-8 June. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E) explosions during 5-8 June generated ash plumes that rose as high as 3.5 km (11,500 ft) a.s.l. and drifted NE and SE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Great Sitkin, Andreanof Islands (USA)

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

AVO reported that slow lava effusion continued at Great Sitkin during 6-13 June, producing a thick lava flow confined to the summit crater. Seismicity remained low. Steam emissions were visible in satellite images during 7-8 June and slightly elevated surface temperatures were identified on 8 June; weather clouds prevented satellite and webcam observations on the other days. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Karangetang, Sangihe Islands

2.781°N, 125.407°E | Summit elev. 1797 m

PVMBG reported that daily white gas-and-steam plumes from Karangetang were visible rising as high as 200 m and drifting W, NW, and NE during 7-13 June. Webcam images published in the daily reports showed incandescence at Main Crater (S crater) and from material on the flanks of Main Crater at 2225 on 7 June and 2051 on 9 June. The Alert Level remained at 3 (on a scale of 1-4) and the public were advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks.

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia’s most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Krakatau, Sunda Strait

6.102°S, 105.423°E | Summit elev. 155 m

PVMBG reported that multiple dense ash plumes were visible rising above Krakatau’s summit during 8-11 June. On 8 June at 0746 a gray ash plume rose 500 m and drifted SW, and at 1537 a dark-gray ash plume rose 1 km and drifted SW. At 0746 on 9 June gray plume rose 800 m and drifted SW; a dark gray ash plume at 0846 rose 3 km and drifted SW. At 0423, 1431, and 1750 on 10 June gray ash plumes rose 1.5-3.5 km and drifted NW. A webcam image showed incandescent material being ejected above the crater at 0455. At 0030 on 11 June a dense gray ash plume rose 2 km and drifted NW. A webcam image about a half an hour later, at 0102, showed incandescent material being ejected above the crater. Diffuse white gas-and-steam plumes rose just 50 m during 12-13 June. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay at least 5 km away from the crater.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Lewotolok, Lembata Island

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

PVMBG reported that the eruption at Lewotolok continued during 7-13 June. Daily white-and-gray ash plumes rose as high as 700 m above the summit and drifted SW, W, and NW. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit crater in all directions.

Geological summary: The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano’s high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Merapi, Central Java

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

BPPTKG reported that the eruption at Merapi (on Java) continued during 2-8 June and seismicity remained at elevated levels. The SW lava dome produced 99 lava avalanches that traveled as far as 2 km down the SW flank (upstream in the Bebeng drainage). Morphological changes to the SW lava dome due to continuing collapses of material were evident in webcam images. 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.

Nyiragongo, DR Congo

1.52°S, 29.25°E | Summit elev. 3470 m

The Observatoire Volcanologique de Goma (OVG) reported that the eruption at Nyiragongo continued during 5-11 June and sulfur dioxide levels in the emissions remained low. Crater incandescence and gas emissions were visible at 1800 on 10 June

Geological summary: One of Africa’s most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes of a stratovolcano contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Reventador, Ecuador

0.077°S, 77.656°W | Summit elev. 3562 m

IG reported that the eruption at Reventador was ongoing during 6-13 June. Seismicity was characterized by explosions, long-period earthquakes, harmonic tremor, and tremor associated with emissions. Though weather clouds hindered visual observations of emissions during 6-7 June, several explosions overnight ejected incandescent material onto the flanks; some of the material rolled down the E flank. During 7-10 June several steam-and-ash emissions rose as high as 1 km above the crater rim and drifted W. Crater incandescence was visible during overnight hours and incandescent blocks sometimes rolled 400-500 m down the flanks. Crater incandescence was visible overnight during 11-13 June. Weather conditions prevented views on 11 June. Gas-and-ash plumes rose 600-800 m and drifted W during 12-13 June. Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) 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 about 1,300 m 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 constructed a debris plain on the eastern floor of the scarp. 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.

Semeru, Eastern Java

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

PVMBG reported that the eruption at Semeru continued during 7-13 June. A dense gray ash plume rose 500 m above the summit and drifted SW at 0534 on 8 June. White-and-gray ash plumes rose 300-400 m above the summit and rifted W and SW at 1214 on 8 June, 0942 on 9 June, and 0653 on 10 June. The Alert Level remained at 3 (third highest 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 the eruption at Sheveluch was ongoing during 1-8 June. Intense fumarolic activity at the active crater was likely associated with growth of Karan lava dome. A daily thermal anomaly over the active crater area was identified in satellite images. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka’s largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that the eruption at Suwanosejima’s Ontake Crater continued, though monitoring parameters had been showing a declining trend. Blocks had not been ejected more than 1 km from the crater after 15 February and the number of explosions had decreased since March. GNSS (Global Navigation Satellite Systems) deformation measurements did not indicate accumulating magma beneath the W part of the island and the number volcanic earthquakes in that area was low. Eruptive activity during 7, 9-10, and 12 June generated ash plumes that rose 1-1.5 km above the crater rim and drifted in multiple directions. An explosion at 1803 on 7 June produced an ash plume that rose 1.4 km and drifted E. Explosions were recorded at 0230 on 9 June and 1758 on 10 June, though details of any emissions were unknown. The Alert Level was lowered to 2 (on a 5-level scale) at 1100 on 9 June and the public was warned to stay 1 km away from the crater.

Geological summary: The 8-km-long island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. One of Japan’s most frequently active volcanoes, it was in a state of intermittent Strombolian activity from Otake, the NE summit crater, between 1949 and 1996, after which periods of inactivity lengthened. The largest recorded eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed, forming a large debris avalanche and creating the open Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Taal, Luzon (Philippines)

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

PHIVOLCS reported continuing low-level unrest at Taal during 6-13 June characterized by elevated seismicity, upwelling in the lake, and sulfur dioxide gas emissions. Volcanic tremor located at shallow depths along the Daang Kastila fissure was continuous with almost 166 hours recorded during 2-9 June; periods of volcanic tremor also took place 4-7 times each day during 9-12 June, each lasting 2-97 minutes. There were 1-11 volcanic earthquakes recorded on most days. Upwelling gasses and hot fluids in the lake continued to be visible almost daily, and voluminous white steam-and-gas plumes that rose as high as 3 km above the lake drifted NW, E, and SSE. Daily sulfur dioxide emissions averaged 2,941-6,884 tonnes per day. The steam-and-gas plumes produced voggy conditions in the caldera during 6-9 June, prompting an advisory to the public to be issued on 7 June. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).

Geological summary: Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.


Smithsonian / US Geological Survey Weekly Volcanic Activity Report – June 7 – 13, 2023 –
Managing Editor: Sally Kuhn Sennert


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