Report on Kanaga (United States) — 15 February-21 February 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
15 February-21 February 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Kanaga (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 February-21 February 2012. Smithsonian Institution and US Geological Survey.
51.923°N, 177.168°W; summit elev. 1307 m
All times are local (unless otherwise noted)
AVO reported possible explosive activity at Kanaga on 18 February. Volcanic tremor detected during 0623-0627 was followed by about an hour of numerous small seismic events. Satellite images showed a detached ash plume, 8 km in length, which drifted 39 km NE. AVO raised the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory on 18 February. Elevated seismic activity continued on 19 February, and photographs taken by a local observer showed a small steam plume. Clouds prevented views of the volcano during 19-21 February.
Geological Summary. Symmetrical Kanaga stratovolcano is situated within the Kanaton caldera at the northern tip of Kanaga Island. The caldera rim forms a 760-m-high arcuate ridge south and east of Kanaga; a lake occupies part of the SE caldera floor. The volume of subaerial dacitic tuff is smaller than would typically be associated with caldera collapse, and deposits of a massive submarine debris avalanche associated with edifice collapse extend nearly 30 km to the NNW. Several fresh lava flows from historical or late prehistorical time descend the flanks of Kanaga, in some cases to the sea. Historical eruptions, most of which are poorly documented, have been recorded since 1763. Kanaga is also noted petrologically for ultramafic inclusions within an outcrop of alkaline basalt SW of the volcano. Fumarolic activity occurs in a circular, 200-m-wide, 60-m-deep summit crater and produces vapor plumes sometimes seen on clear days from Adak, 50 km to the east.