Weeping Wall, Umnak Island

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Weeping Wall, Umnak Island

by | Nov 19, 2018

The Weeping Wall is a cliff on the northwest coast of Umnak Island, one of the Fox Islands in the Eastern Aleutians, Alaska. The descriptive name was given in 1939 by the U.S. Coast and Geodetic Survey for several cracks in the cliff rocks emitting spouts and waterfalls.

The cliff rocks are highly porous basalt scoria formed from cooled magma and pyroclastic flows emanating from the Okmok Caldera. This 5.8 miles (9.3 km) wide circular caldera truncates the top of a large shield volcano that forms the northern part of Umnak Island. Scoria is highly vesiculated lava formed when pressurized volcanic gases are released from cooling magma. The porosity of the basalt is determined by the size and number of vesicles, and connections among vesicles.

The porous rocks on Okmok create aquifers fed by rainfall and snowmelt. Typically the aquifer volume will peak during or shortly after a summer rain event when snowmelt is at a maximum. The natural waterfalls occur where the cliff face intersects the water table. Read more here and here. Explore more of Okmok Volcano and Umnak Island here:

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