A New Island Has Popped Up in Alaska

Glaciers along the coastal plain of southeastern Alaska are rapidly retreating, spilling meltwater into expanding proglacial lakes. One such lake—fed by the receding Alsek Glacier—has grown so much that it transformed a small mountain into a new island.

The Alsek Glacier once enveloped this rocky mound—known as Prow Knob—near its terminus. Over the past 40 years, both of the glacier’s arms have retreated more than 3 miles (5 kilometers), creating Alsek Lake. Landsat images captured in 1984 and 2025 document this transformation, showing that the glacier finally lost contact with Prow Knob this summer, according to a statement from NASA Earth Observatory. Now, the 2-square-mile (5-square-kilometer) landmass is completely surrounded by the waters of Alsek Lake.

According to Mauri Pelto