The Weekly Volcanic Activity Report: August 6-12, 2026

New activity/unrest: Esan, Japan | Etna, Italy | Fuego, Guatemala | Karangetang, Indonesia | Telica, Nicaragua | Tokachidake, Japan.

Ongoing activity: Aira, Japan | Ambae, Vanuatu | Bezymianny, Russia | Great Sitkin, United States | Ibu, Indonesia | Kanlaon, Philippines | Kilauea, United States | Krakatau, Indonesia | Krasheninnikov, Russia | Lewotobi, Indonesia | Lewotolok, Indonesia | Merapi, Indonesia | Poas, Costa Rica | Popocatepetl, Mexico | Purace, Colombia | Rincon de la Vieja, Costa Rica | Sabancaya, Peru | Semeru, Indonesia | Sheveluch, Russia | Suwanosejima, Japan.

New activity/unrest

Esan, Japan

41.805°N, 141.166°E; Elev. 617 m

The Japan Meteorological Agency (JMA) reported that volcanic earthquakes with hypocenters near the crater floor at Esan increased during 5 August through the next morning. The event count was 53 on 5 August, with an additional 6 through 1200 on 6 August. This was the first time since 31 March 2012 that the 24-hour maximum earthquake count exceeded 50 events at Esan. No volcanic tremor was recorded, and ground deformation and fumarolic conditions at the craters showed no changes. JMA stated that no signs of increasing volcanic activity were recognized. The Alert Level remained at 1 (on a 5-level scale).

Geological summary: Esan is a small volcanic complex of seven overlapping andesitic-to-dacitic lava domes on the eastern tip of the Oshima Peninsula across the Tsugaru Strait from Honshu. The complex consists of five late Pleistocene and two early Holocene lava domes, Esan and Misaki. A minor phreatic eruption in 1846 produced a mudflow that caused many fatalities. The latest activity was a small eruption in 1874. Active fumaroles occur at a thermal area on the upper NW flank.

Etna, Italy

37.748°N, 14.999°E; Elev. 3,357 m

The Sezione di Catania – Osservatorio Etneo (INGV) reported that a renewed stronger phase of activity occurred at Etna’s Voragine Crater (VOR) during 6-12 August, continuing the eruptive sequence described in previous reports. An explosion at the summit craters at 0250 on 6 August marked the onset of Strombolian activity at VOR, producing weak ash emissions and plumes that drifted ESE. Explosions of variable frequency ejected coarse material that fell mainly within the crater, weak ash emissions drifting SSW, and a lava flow spilling into the adjacent Northeast Crater (NEC). Beginning at 2230, the Strombolian activity intensified and evolved into lava fountaining, and the eruptive cloud drifted SE. The Aviation Color Code (ACC) was raised first to Orange and then to Red.

The lava fountain strengthened overnight during 6-7 August before gradually decreasing. Strong Strombolian activity at VOR continued to produce eruptive clouds that drifted S and SSW, and ashfall was recorded in Ragalna, Adrano, Piano Vetore, and Nicolosi. A new eruptive vent opened around 0930 on 7 August in the Valle del Leone (the upper sector of the Valle del Bove) at 2,750 m elevation, feeding lava flows whose fronts passed Monte Simone and reached 2,000 m elevation by 1500. The ACC fluctuated between Orange and Red several times during the week because of the variable activity.

Intense explosive activity on 8 August originated from at least three vents between VOR and the Southeast Crater. At about 1130 a new eruptive vent opened at 2,360 m elevation in the Valle del Bove near Monte Rittmann, accompanied by two small pyroclastic flows generated by the collapse and rapid mobilization of loose material. Field personnel reported another pyroclastic flow between Monte Simone and Monte Rittmann. Lava fields fed by the 2,750 and 2,360 m vents advanced through the Valle del Bove, with active fronts at elevations between 1,850 and 2,100 m.

During 9-10 August, explosive activity at VOR alternated between stronger and weaker phases. During the stronger phases, bombs fell in the summit area, and abundant ash was emitted, drifting SSE and SSW and falling on the S flank. By about 1900 on 10 August the most advanced flow front had passed Rocca delle Palombe and reached an elevation of 1,370 m.

Additional eruptive vents opened in the Valle del Bove near Monte Simone, at 1,900 m on 10 August and 2,090 m on 11 August. Effusive activity from the 2,750 m, 2,090 m, and 1,900 m vents, together with persistent explosive activity and ash emission at VOR, continued through 12 August. The most advanced active front, fed by the 1,900 m vent, was near Rocca Capra in the Valle del Bove around 1,365 m. Flows fed by the 2,360 m vent appeared to be cooling. The ACC was at Red as of 12 August.

Geological summary: Mount Etna, towering above Catania on the island of Sicily, has one of the world’s longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Fuego, Guatemala

14.4748°N, 90.8806°W; Elev. 3,799 m

The Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH) reported that a period of stronger activity at Fuego that had begun at 0830 on 3 August ended on 5 August, after 50 hours of activity. Pyroclastic density currents, causing erosion that altered the crater morphology; rockfalls and accumulations of erupted material were reported in the Seca (W flank) and Ceniza (SW flank) ravines. Ashfall primarily affected communities on the W and SW flanks within the municipality of San Pedro Yepocapa (Chimaltenango).

Lower-level eruptive activity continued through 12 August. Explosions recorded by the seismic network at rates of 4-11 per hour generated gas-and-ash plumes that rose as high as about 1 km above the summit and drifted as far as 25 km. Ashfall was reported in downwind areas, including San Pedro Yepocapa, Sangre de Cristo, and Finca Palo Verde. Weak-to-moderate degassing produced white to light-gray fumarolic emissions that rose 200-300 m above the crater. Rumbling sounds, shock waves, and sounds resembling a train locomotive were noted on some days and were audible in surrounding communities. Explosions ejected incandescent material, with pulses as high as 400 m above the crater accompanied by weak avalanches; incandescent block avalanches descended the Ceniza, Taniluyá, Seca, Santa Teresa, Trinidad y Las Lajas ravines and sometimes reached vegetated areas. On 9 August the Fuego Volcano Observatory (OVFGO) reported collapses of material from the crater rim.

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 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.

Karangetang, Indonesia

2.781°N, 125.407°E; Elev. 1,797 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Karangetang continued during 6-12 August. Dense white plumes rose 10-20 m above the summit daily. The seismic network recorded up to 21 avalanche events and 15-131 gas emission events per day, along with 1-47 harmonic tremor events and 3-33 non-harmonic tremor events. PVMBG noted increases in gas emission events and harmonic tremor on 7 August.

At around 2000 on 9 August, an effusive eruption began from the North Crater. Lava advanced from the crater and traveled about 700 m S into the saddle between the North and South (Main) craters, then advanced W for about 400 m and NNW for about 1 km, igniting vegetation fires. Incandescent lava avalanches occasionally descended the W to NW flanks on 10 August. PVMBG revised the hazard zone after the 9 August eruption to restrict access within 2.5 km on the N to W, and SW, sides of the North Crater. An eruption at 2343 on 11 August produced a moderately dense white-to-gray ash plume that rose 350 m above the summit and drifted E. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay 1.5 km away from the North and Main craters and outside the revised hazard zone.

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.

Telica, Nicaragua

12.606°N, 86.84°W; Elev. 1,036 m

The Washington Volcanic Ash Advisory Center (VAAC) reported that ash plumes at Telica were identified in webcam and satellite images on 11 August rising to 1.7-2 km (5,500-6,500 ft) a.s.l. and drifting SW and WSW as far as 140 km from the summit.

Geological summary: Telica, one of Nicaragua’s most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Tokachidake, Japan

43.418°N, 142.686°E; Elev. 2,077 m

The Japan Meteorological Agency (JMA) reported that volcanic activity at Tokachidake remains elevated, with active plumes emanating from Crater 62-2 and the Furikozawa fumarole group. Recent eruptions included a grayish-white plume rising 300 m above the crater rim. Thermal activity, volcanic gas emissions, and seismicity have increased since the spring of 2026, and further eruptions may affect areas within 1.5 km of Crater 62-2. The public is advised to remain vigilant for large volcanic rocks and ashfall, follow local authority instructions, and avoid dangerous areas. The volcano remains at Alert Level 2 (on a scale of 1-5).

Geological summary: Tokachidake volcano consists of a group of dominantly andesitic stratovolcanoes and lava domes arranged on a NE-SW line above a plateau of welded Pleistocene tuffs in central Hokkaido. Numerous explosion craters and cinder cones are located on the upper flanks of the small stratovolcanoes, with the youngest Holocene centers located at the NW end of the chain. Frequent historical eruptions, consisting mostly of mild-to-moderate phreatic explosions, have been recorded since the mid-19th century. Two larger eruptions occurred in 1926 and 1962. Partial cone collapse of the western flank during the 1926 eruption produced a disastrous debris avalanche and mudflow.

Ongoing activity

Aira, Japan

31.5772°N, 130.6589°E; Elev. 1,117 m

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera’s Sakurajima volcano) during 3-10 August. Sakurajima exhibited ongoing eruptive activity that began in early August 2026, with eruptions producing ash plumes up to 2.2 km above the crater, ejections of large ballistic rocks up to 600 m from the crater, and pyroclastic flows. Monitoring data indicated continuing ground deformation beneath the Aira Caldera as well as high sulfur dioxide emissions. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 2 km of both the Minimadake and Showa 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.

Ambae, Vanuatu

15.389°S, 167.835°E; Elev. 1,496 m

The Vanuatu Meteorology and Geohazards Department (VMGD) reported that minor eruptive activity continued at Ambae during July 2026. Persistent volcanic tremor and continuous volcano-seismic events were detected, and satellite imagery in July 2026 showed ongoing plume emissions from active vents, containing volcanic gases, steam, and ash. Lava effusion and flows within Lake Voui have significantly altered the crater’s geomorphology, resulting in the growth of the volcanic cone and the disappearance of the lake. Satellite data indicated continuous thermal anomalies, and high sulfur dioxide emissions confirmed ongoing degassing. The Alert Level remained at 3 (on a scale of 0-5), and the public was advised to stay outside Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to avoid streams during heavy rains due to lahar hazards from the remobilization of residual ash.

Geological summary: The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone with numerous scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Bezymianny, Russia

55.972°N, 160.595°E; Elev. 2,882 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that effusive activity of the volcano continued during 6-10 August. Lava flows were accompanied by powerful gas-steam emissions. A daily thermal anomaly was identified in satellite images. Dates and times are provided in Coordinated Universal Time (UTC); events are in local time only where specified.

Geological summary: The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Great Sitkin, United States

52.076°N, 176.13°W; Elev. 1,740 m

The Alaska Volcano Observatory (AVO) reported that lava continued to slowly erupt within the summit crater of Great Sitkin during the week of 6-12 August. A GNSS sensor on the NW shore of the island continued to record deflation, consistent with pressure reduction at depth because of the lava effusion. Satellite data showed gradual expansion of the lava dome toward the ESE and slightly elevated surface temperatures when cloud cover did not obscure the volcano. Seismic activity remained low, with only occasional small volcanic earthquakes and seismic signals associated with minor rockfalls detected. 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, Indonesia

1.4941°N, 127.6324°E; Elev. 1,357 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 6-12 August, with daily eruptive events recorded by the seismic network. Daily gray ash plumes rose 400-500 m above the summit. The Alert Level remained at 2 (the second lowest level on a four-level scale) and the public was advised to stay 2 km away from the active crater and 3.5 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.

Kanlaon, Philippines

10.4096°N, 123.13°E; Elev. 2,422 m

Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that Kanlaon remained at Alert Level 2 during 6-11 August. Moderate volcanic unrest during this time was characterized by 1-5 daily volcanic earthquakes, sulfur dioxide emissions fluctuating between 651 and 1,568 tons per day, plumes obscured due to cloud cover, and ground deformation showing inflation with short-term deflation. Authorities prohibited entry within a 4-kilometer radius (Permanent Danger Zone) and advised against flying near the summit due to risks of sudden steam-driven or phreatic eruptions and possible magmatic activity.

Geological summary: Kanlaon volcano (also spelled Canlaon) forms the highest point on the Philippine island of Negros. 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.

Kilauea, United States

19.421°N, 155.287°W; Elev. 1,222 m

The Hawaiian Volcano Observatory (HVO) reported that the eruption within Kilauea’s Kaluapele summit caldera, characterized by episodic fountaining, incandescence, and intermittent spatter from craters along the SW margin of Halema`uma`u Crater, continued at variable levels during 6-12 August. Weak glow and intermittent incandescence were observed from the north vent, while the south vent appeared dark for most of the reporting period after 7 August. Incandescence persisted at the N end of a feature that had opened upslope of the south vent on 30 July. Overflight photographs on 11 August identified it as a collapse feature, which was 10 x 20 m based on measurements using satellite imagery. Flames and intensified glow from the vents and the collapse feature accompanied gas pistoning, which alternated with periods of continuous tremor throughout the week. Very minor spattering activity occurred within the north vent at about 2000 on 6 August and between 0430 and 0500 on 7 August.

Precursory low-level eruptive activity for episode 53 began at about 1120 on 12 August, with intermittent lava dome fountains and overflows from the north vent. Spattering was consistently observed beginning around 1104. Brief overflows, each lasting 1-4 minutes, began at 1120, 1135, 1145, and 1223. HVO raised the Volcano Alert Level to Watch and the Aviation Color Code to Orange at 1146. A fifth, sluggish flow began at about 1300 and became sustained, growing gradually for about 45 minutes. Output increased sharply at 1345 as summit tilt switched to deflation. A double dome fountain formed and fed a broad overflow that rapidly extended more than 600 m from the vent. Large overflows from the south vent began at 1526 and 1538 that lasted about 5-6 minutes each, and a small flow was visible from the collapse feature behind the south vent at 1531.

Lava fountaining increased gradually from the precursory dome fountaining, and episode 53 began from the north vent at 1545. Fountains reached 25-30 m high shortly after onset and reached a peak of about 150 m between 1700 and 1745. The plume rose to more than 5 km a.s.l. Fountaining ended abruptly at 0123 on 13 August after 9.6 hours of continuous activity, and HVO lowered the Volcano Alert Level to Advisory and Aviation Color Code to Yellow.

Geological summary: Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the Island of Hawai`i. 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 Halema`uma`u 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.

Krakatau, Indonesia

6.1009°S, 105.4233°E; Elev. 285 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Anak Krakatau during 6-12 August. White to gray plumes of variable density rose to approximately 10-150 m above the summit. Fog and cloudy weather obscured continuous observations. The Alert Level remained at 3 (on a scale of 1-4) and the public was advised to stay 3 km away from summit.

Geological summary: The renowned Krakatau (frequently misnamed as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older 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 the Rakata, Danan, and Perbuwatan cones 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 Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.

Krasheninnikov, Russia

54.596°N, 160.27°E; Elev. 1,816 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that the effusive activity at Krasheninnikov continued during 6-10 August. Lava flows advanced along the E flanks of the Northern Cone, and emissions of gas-and-steam, sometimes containing ash, were observed. Satellite data analyzed by KVERT showed a large bright thermal anomaly. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale). Dates and times are provided in Coordinated Universal Time (UTC); events are in local time only where specified.

Geological summary: The late Pleistocene to Holocene Krasheninnikov volcano is comprised of two overlapping stratovolcanoes within a 9 x 10 km Pleistocene caldera. Young lava flows from summit and flank vents descend both into the caldera and down its outer flanks, and older flows that covered much of the SE caldera rim extended downslope at least 7 km. Tephra deposits from the caldera-forming eruption directly overlie a 39,000 years before present (BP) tephra thought to be associated with the formation of Uzon caldera (Florenskii, 1988). The intra-caldera stratovolcanoes are situated along a NE-SW-trending fissure that has also produced zones of Holocene cinder cones extending 15-20 km beyond the caldera. Construction of the southern edifice began about 11,000 years BP and lasted for about 4,500 years; it has a summit crater about 800-900 m wide. The northern edifice was constructed during a cycle of similar length that began about 6,500 years ago; it has a summit crater about 1.5 km wide, within which is low cone with an 800-m-wide crater containing another small cone. An eruptive cycle during about 600-400 years BP (1350-1550 CE) produced the Pauk lava cone in the crater of the northern cone and the Yuzhny lava flow on SW flank outside the caldera, followed by the Molodoy flow from the upper SW flank (Ponomareva, 1987; Ponomareva and Tsyurupa, 1985; Ponomareva and Braitseva, 1990).

Lewotobi, Indonesia

8.542°S, 122.775°E; Elev. 1,703 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Lewotobi Laki-laki during 6-12 August. Ash plumes ranged from 200-800 m above the summit, drifting mostly toward the N, SW, W, and NW. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the center of Laki-Laki.

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; Elev. 1,431 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported ongoing eruptive activity at Lewotolok during 6-12 August. Daily white plumes rose as high as 200 m above the summit and drifted in multiple directions. Ash plumes rose 200-600 m above the summit and drifted SE, SW, and W during 7-11 August. Incandescent material was periodically ejected above the summit, notably on 8-11 August. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the summit.

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, Indonesia

7.54°S, 110.446°E; Elev. 2,910 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Merapi (on Java) continued during 6-12 August with lava avalanches produced by the active lava dome on the upper SW flank. The seismic network recorded 4-19 lava avalanches per day that traveled as far as 2 km down the SW flank. Two pyroclastic flows were detected on 10 August, one of which was also observed descending the SW flank, and single flows were detected on 11 and 12 August. 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.

Poas, Costa Rica

10.2°N, 84.233°W; Elev. 2,697 m

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported that Poás remained active during 8-12 August, with occasional eruptive events that were restricted to the crater area. The Volcanic Alert Level remained at 2 (the second lowest level on a four-level scale).

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.

Popocatepetl, Mexico

19.023°N, 98.622°W; Elev. 5,393 m

The Centro Nacional de Prevención de Desastres (CENAPRED) reported that daily exhalations at Popocatépetl continued during 6-12 August, accompanied by water vapor, volcanic gases, and ash; daily counts ranged from 35 to 74. Six minutes of tremor were recorded during 5-6 August. Emissions of water vapor and volcanic gases were visible from the crater each morning and drifted generally W to NW. Cloud cover restricted visibility of the crater on 9-10 August. From 11 August the ash content of the exhalations was described as occasionally light rather than continuous.

The Washington VAAC reported ash plumes on 6-8 August. Plumes rose to about 1 km above the summit on 6 August and drifted SW and then W, extending approximately 45 km WNW of the summit. On 7 August a plume rose to about 2.2 km above the summit and drifted N, though strong winds spread ash towards the W to NNE, causing ashfall within about 20 km of the summit. The Centro Nacional de Comunicaciones (CENACOM) reported light ashfall on 7 August in Cuernavaca, Tlayacapan, Yautepec, Totolapan, and Jiutepec, all in Morelos. On 8 August a plume rose to about 1.6 km above the summit and drifted W, and ash emission activity was characterized as high. Ash was no longer identifiable in satellite imagery later that day, when only water vapor and gas were observed emitting from the summit. No further advisories were issued through 12 August. 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.

Purace, Colombia

2.3095°N, 76.3948°W; Elev. 4,650 m

The Servicio Geológico Colombiano (SGC) reported that eruptive activity at Puracé continued during 6-12 August, with episodes of continuous tremor and long-period (LP) events located beneath the crater at depths of less than 1 km. Seismicity related to rock-fracturing remained very low in both number and magnitude and occurred 1-2 km beneath the crater. Sulfur dioxide flux stayed above the average baseline level, measuring 2,100 tonnes per day on 6 August, 1,900 tonnes per day on 7 August, and 2,100 tonnes per day on 8 August. Plumes dispersed NW except for on 8 August when they dispersed W. Soil carbon dioxide concentrations continued to rise throughout the reporting period. Ash emissions occurred daily. A single emission was recorded on 5 August at 1440 and another at 1014 on 7 August; adverse weather prevented webcam views, though residents of Cristales reported loud sounds coinciding with both events. Six emissions were recorded during 7-8 August, with notable events at 1757 on 7 August and at 0912 on 8 August that resulted in reported ashfall in Coconuco, Cristales and Cobaló, and Popayán. The Alert Level remained at Orange (the second highest level on a four-color scale).

Geological summary: Puracé is an active andesitic volcano with a 600-m-diameter summit crater at the NW end of the Los Coconucos Volcanic Chain. This volcanic complex includes nine composite and five monogenetic volcanoes, extending from the Puracé crater more than 6 km SE to the summit of Pan de Azúcar stratovolcano. The dacitic massif which the complex is built on extends about 13 km NW-SE and 10 km NE-SW. Frequent small to moderate explosive eruptions reported since 1816 CE have modified the morphology of the summit crater, with the largest eruptions in 1849, 1869, and 1885.

Rincon de la Vieja, Costa Rica

10.8314°N, 85.3364°W; Elev. 1,729 m

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported that two energetic phreatic eruptions at Rincón de la Vieja were recorded by the seismic and infrasound networks at 1717 and 1725 on 11 August. The events had acoustic magnitudes of 4.1 and 4.5, respectively, and produced a lahar. Cloud cover obscured the crater, but webcam video showed two white plumes rich in water vapor and gases rising about 1 km above the summit and drifting W. No ashfall was reported. A possible eruption was recorded at 0318 on 12 August but was not confirmed. The Alert Level remained at 3 (Caution) and the Aviation Color Code remained Orange.

Geological summary: Rincón de la Vieja is a volcanic complex in the Guanacaste Range of NW Costa Rica. Sometimes referred to as the Rincon de la Vieja-Santa María Volcanic Complex, it consists of a slightly arcuate 20-km-long ridge of 12 craters and pyroclastic cones 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. The Santa María cone, the highest peak of the complex, is located on the E side of the ridge and has a lake within the 400-m-diameter 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 reported eruptions possibly dating back to the 16th century, have been from the active crater, near the center of the complex, with an acidic 300-m-diameter lake.

Sabancaya, Peru

15.787°S, 71.857°W; Elev. 5,960 m

The Instituto Geofísico del Perú’s (IGP) Centro Vulcanológico Nacional (CENVUL) reported continuing eruptive activity at Sabancaya during 3-9 August. Forty-three earthquakes associated with the movement of magmatic fluids were recorded, along with events related to internal rock fracturing; no volcanic explosions occurred during the period. Emissions of water vapor, gas, and ash rose as high as 1.7 km above the summit, dispersing predominantly N and NW, affecting areas within 10 km of the vent. No significant deformation of the edifice was detected. Moderate sulfur dioxide (SO₂) emissions averaged 766 tonnes per day, and 13 thermal anomalies (each less than 2 MW) associated with the lava dome were identified. 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 from the summit.

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.

Semeru, Indonesia

8.108°S, 112.922°E; Elev. 3,657 m

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 6-12 August, with daily eruptive events recorded by the seismic network. Daily white-to-gray or gray ash plumes rose 300-1,100 m above the summit and drifted multiple directions. The Alert Level remained at 3 (the second lowest level on a scale of 1-4) and the public was advised to stay at least 5 km from the summit crater, where incandescent ballistic material could fall, to avoid all activity within 13 km of the summit along the Besuk Kobokan drainage in the SE sector, and beyond that distance to stay 500 m from the riverbanks, where pyroclastic flows and lahars could extend as far as 17 km from the summit.

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, Russia

56.653°N, 161.36°E; Elev. 3,283 m

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported continuing lava effusion and explosive activity at the lava domes along the N crater floor of Young Sheveluch (on the SW flank of Old Sheveluch) during 6-10 August. Growth continued along the N part of the main lava dome. A thermal anomaly was identified in satellite images on most days; weather clouds occasionally obscured views. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC; 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, Japan

29.638°N, 129.714°E; Elev. 796 m

The Japan Meteorological Agency (JMA) reported that eruptive activity at Suwanosejima’s Otake Crater continued during 31 July-7 August. White plumes rose as high as 400 m above the crater rim, and crater incandescence was observed at night with a high-sensitivity camera. The Alert Level remained at 2 (the second level on a five-level scale) and the public was warned to be cautious within 1.5 km of 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 – GVP – August 6-12, 2026 – Managing Editor: Sally Sennert