Great Sitkin volcano news & activity updates:
Great Sitkin volcano (United States, Aleutian Islands) activity update
mardi nov. 28, 2017 12:05 | AUTEUR : T
Worldview-3 satellite image of the summit area of Great Sitkin volcano, November 21, 2017. The area of steaming indicated by the red arrow is the likely source of the volcanic emissions noted and photographed by local observers on Adak, November 19, 2017. The melt depressions on the east side of the 1974 lava flow were evident in a September 14, 2017 satellite image but not present in an April 18, 2017 image indicating that they likely formed during the spring-summer 2017. (image: Chris Waythomas / AVO / USGS)
Recent observations of a robust steam plume and a period of gradually increasing seismicity over several months at Great Sitkin prompted AVO to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory on 22 November.
Steaming from Great Sitkin Volcano as visible from the town of Adak (40 km or 25 miles to the SW) (image: Alain Beauparlant via AVO / USGS)
On 19 November local observers photographed a light-colored vapor plume rising about 300 m above the vent and drifting 15-20 km S.
A satellite image acquired on 21 November showed steam continuously jetting from a small fumarole on the W side of the 1974 lava flow within the summit crater, and at least one area where snow and ice had been melted.
Seismicity had fluctuated but increased overall since July 2016, most notably in June 2017. The seismic activity was characterized by earthquakes less than M 1, and occurred either just below the summit or just offshore the NW cost of the island, 30 km below sea level.
Possible explosion signals were recorded in seismic data on 10 January and 21 July 2017, but there were no confirmed emissions.
Source: Smithsonian / USGS Weekly Volcanic Activity Report 22-28 November 2017
vendredi, nov. 24, 2017
An increase in seismic activity and degassing prompted the Alaska Volcano Observatory (AVO) to raise the alert level of the volcano to yellow today: ... [details]