The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Thursday, these notices are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of eruptions during the week, but rather a summary of activity that meet selected criteria. Carefully reviewed, detailed reports are published in the Bulletin of the Global Volcanism Network.

The Vanuatu Meteorology and Geohazards Department (VMGD) reported that the eruption at Ambae continued during 21-26 August, with explosive activity producing tall ash plumes on 25 August. Continuous plumes of gas, steam, and ash were visible in satellite and webcam images drifting NW during 21-24 August and drifting NE on 25 August. Sulfur dioxide gas emissions were at moderate to high levels, and seismicity indicated high levels of activity. Thermal anomalies were identified in satellite data. The Wellington Volcanic Ash Advisory Center (VAAC) reported that ash plumes were significantly higher during 25-26 August. The eruption escalated at 2040 on 25 August, and by 2124 an ash plume had risen to 16.5 km (54,000 ft) a.s.l. and was drifting E based on satellite images. The ash plume altitude decreased to 15.2 km (50,000 ft) a.s.l. by 2153 and to 12.8 km (42,000 ft) a.s.l. by 0013 on 26 August. A strong sulfur dioxide signal was also detected. Ash plumes continued to be detected during the rest of the day on 26 August rising 3-4.6 km (10,000-15,000 ft) a.s.l. The Alert Level remained at 3 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone B, defined as a 3-km radius around the active vents in Lake Voui, and to stay away from drainages during heavy rains.

Sources: Vanuatu Meteorology and Geohazards Department (VMGD),Wellington Volcanic Ash Advisory Center (VAAC)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and a news source reported that an eruption at Karangetang?s North Crater (Kawah Dua) continued during 20-26 August. Daily white plumes rose as high as 400 m above the summit and drifted in various directions. Incandescence at both the North and South craters was visible in some webcam images throughout the week, but was stronger at North Crater. Seismicity was variable but at high levels, and rumbling sounds were occasionally heard. Incandescence at the North summit and from the lava flows on the flanks was visible in webcam images at 0019 on 26 August and at 0737 on 27 August. The Alert Level remained at 2 (on a scale of 1-4) and the public was advised to stay 1.5 km away from both craters, with an extension to 2.5 km on the NW and SW flanks of North Crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that the eruption at Klyuchevskoy continued at the summit crater during 20-26 August. A thermal anomaly was identified in satellite images on most days; weather clouds sometimes obscured views. Ash plumes periodically rose as high as 6 km (19,680 ft) a.s.l. and drifted as far as 500 km NE and E. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported ongoing eruptive activity at Krakatau during 20-26 August. Daily ash-and-gas plumes that were a mixture of white, gray, and black colors rose 100-400 m above the summit and drifted mainly NW, W, and SW. Several webcam images showed incandescent material being ejected above the crater. The Alert Level remained at 3 (on a scale of 1-4) and the public was advised to stay 3 km away from summit.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Servicio Nacional de Geología y Minería (SERNAGEOMIN) and the Servicio Geológico Minero Argentino (SEGEMAR) reported that a passive, low-altitude, and low-energy ash plume from Nevados de Chillán drifted S on 12 August. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned that an eruption may impact areas within 1 km. The Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED) maintained an ?Early Preventive Alert? for Pinto and Coihueco.

Sources: Servicio Geológico Minero Argentino (SEGEMAR),Servicio Nacional de Geología y Minería (SERNAGEOMIN),Sistema y Servicio Nacional de Prevención y Repuesta Ante Desastres (SENAPRED)

The Servicio Nacional de Geología y Minería (SERNAGEOMIN) reported that several episodes of minor explosive activity in Villarrica?s summit crater were observed beginning at 0239 on 21 August when a plume rose 40 m above the crater rim. Incandescence from the lava lake was visible overnight during 21-22 August. SERNAGEOMIN and Servicio Geológico Minero Argentino (SEGEMAR) noted that at 1232 on 22 August a small ash plume rose 60 m above the crater rim and drifted NE, based on webcam images. The Volcanic Alert Level remained at Green (the lowest level on a four-level scale).

Sources: Servicio Geológico Minero Argentino (SEGEMAR),Servicio Nacional de Geología y Minería (SERNAGEOMIN)

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 17-24 August. Crater incandescence was visible in nighttime webcam images. An eruptive event at 2029 on 17 August generated an ash plume that rose as high as 1.9 km above the summit. An ash plume from an explosion at 0538 on 19 August rose as high as 1.3 km above the summit and drifted NW. Very small eruptive events were recorded during 21-24 August. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to be cautious within 1 km of both the Minimadake and Showa craters.

Source: Japan Meteorological Agency (JMA)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Dukono continued during 20-26 August. White-and-gray ash plumes rose as high as 1.4 km above the summit and drifted in various directions on most days; weather conditions obscured views on 26 August. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Sezione di Catania - Osservatorio Etneo (INGV) reported eruptive activity at Etna?s summit craters during 17-23 August characterized by weak explosive activity and ash emissions at Voragine Crater (VOR), Bocca Nuova (BN) Crater, and Northeast Crater (NEC), and effusive activity from two vents within the Valle del Bove. Weak and intermittent explosive activity at VOR persisted during most of the week with diffuse ash emissions dissipating around the summit. Diffuse, ongoing emissions at BN and NEC craters were recorded by webcams. Lava effusion continued from the vent at 1,900 m elevation during most of the week. Active and overlapping flows did not extend below 1,500 m elevation. The Aviation Color Code (ACC) was lowered to Orange (the second highest color on a four-color scale) on 18 August because explosive activity was decreasing. A new vent opened at 3,060 m elevation on 18 August, produced a 600-m-long lava flow, and was inactive by 19 August. Lava was no longer flowing from VOR into NEC by 19 August. The leading lava flow had reached an elevation of 1,315 m in the vicinity of Rocca Musarra by 19 August, but by 23 August the vent at 1,900 m elevation was no longer active. The ACC was lowered to Yellow on 24 August and to Green on 26 August. The volcano Alert Level remained at Yellow (the second lowest level on a four-level scale) according to the Dipartimento della Protezione Civile.

Sources: Dipartimento della Protezione Civile,Sezione di Catania - Osservatorio Etneo (INGV)

The Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity at Fuego continued during 19-26 August. Daily explosions recorded by the seismic network, at rates of 2-10 per hour when reported, generated gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted as far as 60 km SW, W, and NW. Explosions produced shock waves and rumbling or jet engine sounds that were reported daily and sometimes caused roofs and structures to vibrate. Explosions occasionally ejected incandescent material as high as 400 m above the summit and onto the flanks, causing incandescent block avalanches; notably avalanches descended the Seca (W), Taniluyá (SSW), Ceniza (SSW), Trinidad (SSW), and Las Lajas (SE) drainages, sometimes reaching vegetated areas. Ash fell in areas on the W flank during 19-20 August. Ashfall was reported in Sangre de Cristo (8 km W), San Pedro Yepocapa (8 km NW), Pochuta, and surrounding areas during 20-21 August, in San Pedro Yepocapa during 22-24 August and in Panimaché (8 km SW), Morelia (10 km SW), Santa Sofia (12 km SW), El Porvenir (11 km SW), San Pedro Yepocapa, Sangre de Cristo, and other nearby communities during 23-24 August.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin?s summit crater during 19-26 August based on webcam and satellite images. The flow gradually expanded E. Minor earthquakes were detected daily, likely associated with rockfalls on the growing dome. Slightly elevated surface temperatures were identified in satellite images during 24-25 August. Weather clouds often obscured webcam and satellite views during most of the week. 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).

Source: US Geological Survey Alaska Volcano Observatory (AVO)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity at Ibu continued during 20-26 August, with daily eruptive events recorded by the seismic network. Gray or white-to-gray ash plumes rose 300-1,000 m above the summit and drifted in multiple directions, especially towards the N, NE, and SE. Incandescence at the summit was visible in some nighttime webcam images. 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)