It dams a lake until the lake breaks through the ice
Until recently this was one of the very few glaciers on Earth roughly in balance, thirty kilometres long and 250 square kilometres of ice, gaining about as much as it lost while almost everything else retreated; since 2020 it has been going backwards too. The spectacle is the dam. The glacier pushes across the Brazo Rico arm of Lake Argentino and seals it off, the water behind rises, sometimes 30 metres above the main lake, and eventually forces a tunnel through the ice which collapses in a rupture that can discharge 8,000 cubic metres a second. The cycle runs anywhere from yearly to less than once a decade, and people travel a long way on short notice to see one. Boardwalks, boat trips and guided ice treks from El Calafate, 78 km away.
Los Glaciares National Park, Argentina
See it on the map
