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 Wednesday, 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.

A small explosion from the summit lake region of Korovin, one of the volcanoes at the Atka volcanic complex, was detected at 1926 on 20 February, prompting the Alaska Volcano Observatory (AVO) to raise the Volcano Alert Level to Watch (the second highest level on a four-level scale) and the Aviation Color Code to Orange (the second highest color on a four-color scale). The event was brief (less than 10 seconds), probably phreatic, and likely ejected a small amount of ash that was deposited within the immediate vicinity of the lake, though ash was unconfirmed. A meteorological cloud deck at altitudes of 2.4-3 (8,000-10,000 ft) a.s.l. obscured direct satellite observations, but no ash emissions were observed above the clouds. Satellite data acquired later that evening showed no evidence of hot material at the surface. There were no further explosive events detected and no noticeable change in seismic activity; at 1114 on 21 February AVO lowered the Volcano Alert Level to Advisory and the Aviation Color Code to Yellow. This type of singular explosion was common at Korovin. Several small local seismic events were detected during 21-23 February, though the overall level of seismicity was very low. Satellite and webcam observations were obscured by weather clouds.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that a bright thermal anomaly over Bezymianny was identified in satellite images during 13-20 February. According to the Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS) occasional ash plumes rose as high as 1.2 km above the summit and drifted E and SE. On most days, debris avalanches were visible descending the SE and E flanks during dark hours; weather conditions sometimes obscured webcam and satellite views. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are reported in UTC; specific events are in local time where noted.

Sources: Institute of Volcanology and Seismology (IVS) of the Far Eastern Branch of the Russian Academy of Sciences (FEB RAS),Kamchatkan Volcanic Eruption Response Team (KVERT)

The Sezione di Catania - Osservatorio Etneo (INGV) reported that an eruption at Etna continued during 17-23 February. Activity observed through webcams and during field inspections on 19, 22, and 24 February was characterized by the effusion of a lava flow from a fissure, explosive activity at the summit, and gas emissions at several of the craters. Strombolian activity at SE Crater was variable, though no explosions were visible during 20-21 February and for most of 22 February. The explosions produced minor ash plumes that dispersed near the summit. Sporadic and moderate explosions from three vents were visible during the evening of 22 February. The activity slightly intensified during 23 February and into 24 February; during the morning of 24 February a fourth explosive vent was identified and at about 1323 a lava flow overflowed the S rim of the crater. The lava flow from the fissure that opened at the base of Bocca Nuova Crater on 8 February continued to effuse lava. The lava flow advanced down the SW flank, descending to 1,840 m elevation during 19-20 February; lava-flow activity was confined to an area between about 3,000 and 2,500 m elevation during the rest of the week. The total flow length was 4.3 km. Based on a 24 February field inspection, scientists determined that lava effusion was occurring at the main vent and also emerging from lava tubes at lower elevations. Lava flows branched from the main flow, widening the flow field, especially near the vent. They also observed a small lava flow effusing from a new vent about 150 m higher up the flank at about 3,070 m elevation.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

The Servicio Nacional de Geología y Minería (SERNAGEOMIN) reported increasing unrest at Láscar. Satellite images detected progressively increasing sulfur dioxide emissions since 6 February (188 tons per day) with an average of 1,191 tons per day (t/d) recorded on 20 February. Sulfur dioxide emissions measured with Differential Optical Absorption Spectroscopy (DOAS) instrumentation located at the Emú station, 6 km ESE, averaged 1,010 t/d on 22 February. Thermal anomalies occasionally detected in satellite data indicated increased temperatures on the crater floor during 6-23 February. Additionally, crater incandescence was visible in webcam images during 19 and 22-23 February. Seismicity during 19-24 February was characterized by a decrease in long-period earthquakes and an increase in signals indicating surficial activity such as landslides. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned to stay at least 1 km away from the crater.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity continued at Lewotobi Laki-laki. During 14-20 February the seismic network recorded decreasing seismicity, specifically there was a notable decrease in both deep and shallow volcanic earthquakes, though signals indicating emissions continued to fluctuate. Fumarolic plumes rose from cracks on the upper NW flank and eruptive events producing ash plumes were recorded on 17 February. The exclusion zone was reduced to a radius of 6 km in all directions from the center of Laki-laki. At 1200 on 20 February the Alert Level was lowered to 3 (on a scale of 1-4) and the exclusion zone was again reduced, to 5 km from the center of Laki-laki and 6 km in a semicircle counterclockwise from the NE to the SW. Several eruptive events per day during 21-22 and 24 February, and one event on 23 February, generated ash plumes that rose 0.4-2 km above the summit and drifted in different directions. Incandescence at the summit and reflected in the plume was visible in several of the webcam images posted with the reports.

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

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Lewotolok was ongoing during 19-25 February. Daily white-and-gray ash plumes rose as high as 300 m above the summit and drifted NW, E, and SE. Incandescence at the summit was visible in webcam images and in at least one of them (at 2201 on 19 February) incandescent material was being ejected above the summit. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the vent and 2.5 km away on the S, SE, and W flanks.

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

The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported that eruptive activity at Poás continued at variable levels during 18-20 February. Several small phreatic eruptions from the central part of the crater lake ejected sediment and gas-and-steam plumes as high as 100 m above the surface of the water. Weather clouds obscured views on 21 February.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

Based on webcam and satellite images, the Washington VAAC reported that on 19 and 22 February ash emissions at Telica rose as high as 1.5 km (5,000 ft) a.s.l. and drifted SW and W.

Source: Washington Volcanic Ash Advisory Center (VAAC)

Unrest at Ahyi Seamount continued during 13-21 February. A plume of discolored water in the vicinity of the seamount was identified in satellite images during 14-16 February, indicating possible submarine activity. No signals coming from the direction of Ahyi were identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi). 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).

Source: US Geological Survey

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 17-24 February. Nightly crater incandescence was visible in webcam images. Explosions at 0643 and 1944 on 21 February generated ash plumes that rose 1.4-1.6 km above the crater rim and drifted SE, and ejected large blocks 500-900 m from the vent. An ash plume from an eruptive event at 1510 on 21 February rose 1 km above the crater rim and drifted SE. An explosion at 0104 on 23 February generated an ash plume that rose 1.5 km above the crater rim and drifted SE. At 1924 on 24 February an explosion ejected blocks 500-700 m from the vent and generated an ash plume that rose 600 m above the crater rim and drifted S. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 km away from both craters.

Source: Japan Meteorological Agency (JMA)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono was ongoing during 19-25 February. White-and-gray ash plumes rose as high as 2 km above the crater rim and drifted in multiple directions during 19-22 and 24-25 February. White plumes rose 200-300 m above the crater rim and drifted SW, W, and NW on 23 February. Booming sounds were reported during 19 and 22-24 February. 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 Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick lava flow in Great Sitkin?s summit crater, confirmed by a 21 February radar image. The lava flow advanced along the NNE margin. Small daily earthquakes were detected by the seismic network. Typical minor steaming from the vent region was detected in a satellite image on 21 February and slightly elevated surface temperatures observed in satellite data during 23-25 February. Weather clouds sometimes obscured views of the volcano. 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)