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 Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and a news source reported that an eruption at Karangetang?s North Crater (Kawah Dua) continued during 27 August-2 September. Daily white plumes rose as high as 500 m above the summit and drifted in various directions. Incandescence at the North Crater and from lava flows and/or incandescent avalanches on the flanks was visible in some webcam images throughout the week. Seismicity remained at high levels and rumbling sounds were occasionally heard. 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 27 August-2 September. A daily thermal anomaly was identified in satellite images. Daily ash plumes rose as high as 7 km (23,000 ft) a.s.l. and drifted as far as 170 km NE and E during 27-30 August. 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 27 August-2 September. Ash-and-gas plumes that were a mixture of white, gray, and black colors rose 100-400 m above the summit and drifted mainly W, NW, N, and NE during 27-31 August. A webcam image on 27 August showed incandescent material being ejected above the crater. White plumes were visible rising as high as 200 m and drifting SW, W, and NW during 1-2 September. 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 Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported increased unrest at Ranakah. Following the M 7.7 tectonic earthquake that occurred off the N coast Flores Island on 15 August there was an increase in the overall number of daily tectonic events. The number of deep volcanic earthquakes also increased, up to 35 events per day. Seismicity declined but remained high towards the end of August, until 1 September when over 100 deep volcanic earthquakes were recorded. Drone overflights revealed denser plumes rising from the solfataras W of the lava dome on 25 August and more diffuse plumes rising from the same area on 1 September. No significant changes at the lava dome were observed during the overflights despite earthquake-triggered landslides occurring in several areas at Ranakah on 18 and 20 August. At 2300 on 1 September the Alert Level was raised to 2 (on a scale of 1-4) and the public was warned to stay 1 km away from the crater.

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that after a period of escalating unrest at Sinabung, which had been detected at least since May, a new eruption occurred on 31 August. During 1-30 August white-and-gray plumes rose as high as 1 km above the summit. Observers noted that the vegetation on the E flank yellowed and dried out. The seismic network recorded a total of one rockfall event, 14 earthquakes indicating emissions, two tornillo earthquakes, 29 low-frequency earthquakes, eight hybrid/multi-phase earthquakes, one shallow volcanic earthquake, and 141 deep volcanic earthquakes. On 28 August blue plumes descending the SE flank were observed. Prior to the eruption on 31 August a swarm was detected that consisted of 85 volcanic earthquakes, one earthquake indicating an emission, and one harmonic tremor. At 1017 a dense black ash plume rose around 3.5 km above the summit and drifted E and SE. The eruption lasted just over an hour based on seismic data. At 1230 the Alert Level was raised to 3 (the second highest level on a scale of 1-4). Though most of the exclusion zone remained at 3 km from the summit, it was increased to 6 km on the SE flank. Hotspots on the N flank were visible. According to a news source ashfall was reported in Berastagi City and residents were urged to wear masks while outside to avoid breathing in ash. Schools in high-risk areas implemented virtual learning for one day. Later that day, during 1800-2400, dense gray-and-brown plumes rose 200-500 m above the summit and drifted NE and E. On 1 September white-and-gray ash plumes rose as high as 600 m above the summit and drifted E, SE, and S, causing ashfall in areas to the SE. News sources reported that residents of Kuta Tengah Village and Payung Village (5 km SSW) were preemptively moved to evacuation centers following increased volcanic activity. Two flights on the Banda Aceh-Medan route were affected, one delayed and one canceled, due to ash in the air. At 0720 on 2 September a gray-to-brown ash plume rose about 1 km above the summit and drifted E and SE.

Sources: Antara News,Antara News,Antara News,Antara News,Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 24-31 August. Crater incandescence was visible in nighttime webcam images during 24-28 August. An explosion at 0951 on 25 August generated an ash plume that rose 400 n above the summit, into weather clouds. Volcanologists conducted a field survey on 27 August and measured very high sulfur dioxide emissions, averaging 3,400 tons per day. There were 22 eruptive events recorded during 28-31 August generating ash plumes that rose as high as 2 km above the crater rim. 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 Vanuatu Meteorology and Geohazards Department (VMGD) and the Wellington Volcanic Ash Advisory Center (VAAC) reported that the eruption at Ambae continued during 27 August-2 September. According to the VAAC multiple daily plumes during 27-30 August were identified in satellite data and webcam images rising 1.5-7.6 km (5,000-25,000 ft) a.s.l. and drifting W, SE, and E. An ash plume rose to 12.5 km (41,000 ft) a.s.l. on 1 September and drifted ESE. VMGD noted that the ash plume also contained very high amounts of sulfur dioxide. Ashfall was reported in areas to the N, E, and S parts of the island, and reached the N part of Pentecost Island. 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 Japan Meteorological Agency (JMA) reported that unrest at Asosan showed a downward trend since 17 August based on seismic and gas emission data. At 1600 on 1 September the Alert Level was lowered to 2 (on a scale of 1-5) and the public was warned not to enter the area around the crater.

Source: Japan Meteorological Agency (JMA)

The Sezione di Catania - Osservatorio Etneo (INGV) reported that eruptive activity at Etna?s summit craters during 24-30 August was characterized by gas emissions and periodic minor ash emissions at Northeast Crater, and minor gas emissions at Southeast Crater. The volcano Alert Level remained at Yellow (the second lowest level on a four-level scale) according to the Dipartimento della Protezione Civile.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkin?s summit crater during 27 August-2 September based on webcam and satellite images. The flow gradually expanded E. Minor earthquakes were detected daily, likely associated with rockfalls on the growing dome. Weather clouds 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 27 August-2 September, with daily eruptive events recorded by the seismic network. Gray ash plumes rose 300-800 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)

The Japan Meteorological Agency (JMA) reported that unrest at Iwatesan had ceased. Deformation detected by multiple methods had stopped and seismicity was at a low level. At 1100 on 27 August the Alert Level was lowered to 1 (the lowest level on a 1-5 scale).

Source: Japan Meteorological Agency (JMA)