The caves at the edge of Iceland’s Svinafellsjokull glacier were formed by highly pressurized glacier ice that contains few air bubbles. Without air, the cave’s ice absorbs all colors but blue, which is refracted and visible to onlookers after rain removes the ice’s surface layer. People can access the cave through a 22-foot entrance that funnels down to a limited, 4-foot opening. Since glaciers are highly active, one can hear loud cracks and groans created by the shifting ice.
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