Thursday, February 9, 2012

New Guinea's Karkar Volcano Spews Ash

The Smithsonian GVP (Global Volcanism Program) reports that an eruption from Karkar volcano island off the coast of New Guinea has erupted, sending a possible ash plume upwards of 10km. Karkar has had historical eruptions in the past, mainly from a cone constructed within a large caldera. Most eruptions have been restricted to the inner caldera, and most have been minor phreatic events, and cone building events, so highly explosive activity is somewhat new in terms of human observation.

Outside the caldera, you can find several tuff rings, maars, and cinder cones that are currently highly vegetated and probably very old. There have been no historical reports of flank eruption from this shield volcano.

The GVP report did not provide many details in regards to this eruption, but here is their statement nonetheless.

"KARKAR Northeast of New Guinea (SW Pacific) 4.649°S, 145.964°E; summit elev. 1839 m

Based on analyses of satellite imagery, the Darwin VAAC reported that a possible ash plume from Karkar rose to altitudes of 7.6-10.7 km (25,000-35,000 ft) a.s.l. and drifted NE and E on 1 February.

Geologic Summary.

Karkar is a 19 x 25 km wide, forest-covered island that is truncated by two nested summit calderas. The 5.5-km-wide outer caldera was formed during one or more eruptions, the last of which occurred 9000 years ago. The eccentric 3.2-km-wide inner caldera was formed sometime between 1500 and 800 years ago. Parasitic cones are present on the northern and southern flanks of basaltic-to-andesitic Karkar volcano; a linear array of small cones extends from the northern rim of the outer caldera nearly to the coast. Most historical eruptions, which date back to 1643, have originated from Bagiai cone, a pyroclastic cone constructed within the steep-walled, 300-m-deep inner caldera. The floor of the caldera is covered by young, mostly unvegetated andesitic lava flows."

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