Satellite images show a new island has appeared in Alaska.

A landmass that was previously encased in the ice of Alaska's Alsek Glacier is now fully surrounded by water, forming a new island in the state, NASA satellite images reveal.

The nearly two-square-mile landmass was left surrounded by the waters of Alsek Lake after the glacier of the same name, which once encircled a small mountain known as Prow Knob near its terminus, lost contact with the mountain this summer.

The pair of images (shown in a comparison below), taken by NASA's Landsat satellites, show the extent of ice retreat and lake growth between July 5, 1984 and August 6, 2025.

The separation between the glacier and Prow Knob happened sometime between July 13 and August 6 this summer, according to the satellite imagery.

Water is rapidly replacing ice along the coastal plain of southeastern Alaska, where glaciers are thinning and retreating, with meltwater forming lakes off of their fronts, NASA says.

The "proglacial" lakes can form where ice dams the local drainage, or such is inhibited by bedrock or "moraines," accumulations of debris left behind by a moving glacier.

In the early 20th century, the Alsek Glacier terminated at Gateway Knob, around three miles west of Prow Knob, according to Mauri Pelto, a glaciologist at Nichols College and member of the science advisory board for NASA Earth Observatory, who first saw the glacier in 1984.

By mid-century, the ice had retreated eastward but still encompassed Prow Knob. While a portion of the perimeter of Prow Knob had been converted to lakeshore by 1984, the Alsek Glacier remained connected to the northern arm of the Grand Plateau Glacier.

However, by 1999, both glaciers retreated and the northern tongue of the Alsek Glacier detached from a narrow island, exposing the glacier's terminus to more calving, Pelto noted.

Following two decades of ice retreat, two tributaries to the north and south of the Alsek stopped feeding ice to the glacier. Alsek Lake also expanded significantly to the south, occupying the space left by the Grand Plateau Glacier, before ice pulled away from the Prow Knob this year, completing its transformation into an island.

Both arms of the Alsek Glacier have retreated more than three miles since 1984, according to Pelto, and that pattern is expected to continue. After losing contact with Prow Knob, the ice is less stable and more prone to calving, the space agency noted.

Since 1984, Alsek Lake has grown from around 17 square miles to around 29 square miles. Along with the neighboring proglacial Harlequin and Grand Plateau lakes, the three lakes have more than doubled in that period, according to NASA.

Source: www.newsweek.com

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