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Shishaldin and Isanotski Volcanoes, Unimak Island
On Unimak Island, in the Aleutian Islands of Alaska, the following volcanoes form a chain oriented from west to east: Pogromni (2002m a.s.l.), Shishaldin (2857m a.s.l.), Isanotski (2446m a.s.l.) and Roundtop Mountain (1871m a.s.l.).
Rainbow at Cold Bay airport; our piper aircraft is ready for takeoff for a flight to Unimak Island.
The perfect cone of Shishaldin rises high above a deck of stratocumuls clouds. Pogromni volcano far right.
The chain of volcanoes on Unimak, from left to right: Roundtop Mountain, Isanotski, Pogromni and Shishaldin.
Whereas Shishaldin is a superb example of a young, symmetric stratovolcano, the much older Isanotski is irregular and deeply eroded.
Except for the topmost part Shishaldin's uppermost flanks are covered by glaciers. Their fast flow leads to intensive crevassing.
Runoff from the Shishaldin's glaciers feeds into rivers meandering through coastal plains towards the Pacific Ocean (upper right).
Despite steam and gas from fumaroles within the crater, fresh snow, which fell during recent storms, covers most of the inside and outside of the crater.
Whereas Shishaldin's summit cone is very steep, its lower flanks are much flatter. Isanotski and Roundtop Mountain in the background.
Note the fresh ice covering the andesitic lava flows erupted during the last activity of 1999.
Note massive frost deposits around Shishaldin's crater (left). Crevasses indicate where glaciers begin to erode troughs into the volcano's flanks.
The nearer half of Isanotski's summit crater rim has collapsed. The crater is now occupied by a glacier of considerable size.
Isanotski from the north: Note how the rock pinnacles forming the summit ridge are encrusteed by big frost deposits.
A lateral cone on the north flank of Roundtop Mountain has collapsed in a similar way to Isanotski and is also occupied by a glacier.
A valley glacier on Isanotski displays ogives and a remarkable patch of moraine probably caused by a landslide (below cloud lower middle).
Isanotski (left) and Shishaldin (right) rise over the cloud deck covering the Bering Sea shoreline.
After leaving Unimak Island a storm begins. As heavy rain sets in it's a good time to be back and land at Cold Bay airport.
|Photos by Marco Fulle, taken on a two hour charter flight on 23 Sept 2007, starting at 11 am, during a brief pause between strong storms. The sun was shining from the SSE; this may help to understand the orientation of the photos.|