Glacier Cave, Alaska.
The image below is of a cave carved out of a glacier at Resurrection bay, in Alaska.
Glacier caves are common, and are formed by the erosive action of water on the ice. The water finds pre-exisiting cracks and fissures in the ice, and over time the ice is chipped away forming vast caverns. Many caves do not, however end up submerged in part as the example below is.
-LL
To read more about glacier cave formation head here;
http://www.environmentalgraffiti.com/news-glacier-caves
Image; Doug Demarest
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