Melting glacier creates brand new island in Alaska
August 6, 2025. (Image credit: NASA)
A new island has appeared in southeastern Alaska after decades of glacier retreat, according to NASA scientists.
Prow Knob, a small mountain once encircled by the Alsek Glacier, is now fully surrounded by water in Alsek Lake. The roughly 2–square-mile (5–square-kilometer) landmass became an island this summer when the glacier "lost contact with it," scientists say.
Satellite images from Landsat show how dramatically the landscape has changed. In 1984, the ice was still connected with Prow Knob. By August of this year, the ice had retreated more than 3 miles (5 kilometers), leaving Prow Knob isolated in the growing lake.
(Image credit: NASA)
“Having lost contact with Prow Knob, the ice is less stable and more prone to calving,” said glaciologist Mauri Pelto of Nichols College, who first studied the Alsek Glacier in the 1980s. Pelto noted that he and the late glaciologist Austin Post had once estimated the separation would occur by 2020, but the glacier held on a few years longer than expected.
This is a photo shows a ground-level view of the lake and island taken in 2015, before the glacier had completely released. (Photo credit: WikiPedia/Long Bach Nguyen)
Alsek Lake itself has grown from 45 square kilometers in 1984 to 75 square kilometers in 2025. Combined with neighboring Harlequin and Grand Plateau lakes, the region’s proglacial waters have more than doubled in size in just four decades as ice continues to thin and melt.
NASA scientists say the transformation underscores the pace of glacial change in Alaska, where rising temperatures are rapidly replacing ice with water.
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