Tyndall’s Trail of Bergs

The Southern Patagonian Icefield is the largest expanse of ice in the Southern Hemisphere outside of Antarctica. The mass of glacial ice extends hundreds of kilometers along the spine of the Andes, feeding dozens of dynamic outlet glaciers that grind their way down from higher elevations. Many of these rivers of ice terminate in the sea or in proglacial lakes.

An astronaut aboard the International Space Station photographed one of these glaciers—Tyndall Glacier in southern Chile—through a layer of ethereal clouds on May 10, 2026. Fragments of ice that had calved off its terminus were visible floating on Lago Geikie.

Like most Patagonian glaciers, Tyndall has been shrinking since the end of the Little Ice Age about 150 years ago. Lago Geikie formed at Tyndall’s terminus around 1940, according to glaciologist Mauri Pelto of Nichols College, and gradually expanded as the ice retreated. Part of the glacier previously terminated in Lago Tyndall to the east, but thinning ice cut off that outlet by 2010, Pelto said. (The ice’s retreat also exposed bedrock along its eastern edge that contains scores of ichthyosaur fossils.)

Along with thinning, ice calving off the glacier’s front has reduced its volume. Tyndall has lost 2.2 kilometers (1.4 miles) in length since November 2022, Pelto said, following about a decade of limited retreat with considerable thinning. A significant calving event in March and April 2023 contributed to the recent uptick in ice retreat. During that time, satellites observed several large icebergs breaking away from Tyndall’s terminus.

Austral autumn in 2026 was a time of active calving retreat at Tyndall (and some neighboring glaciers), Pelto said, albeit more incremental than three years prior. “The substantial crevasses crisscrossing the glacier near the calving front lead to many smaller icebergs,” he said. On the other hand, larger tabular icebergs tend to form when there are fewer deep crevasses near the terminus and the glacier’s ice is thinner.