One of the world's great natural spectacles is the rupture of Argentina's Perito Moreno glacier, which happens after the moving ice blocks the Brazo Rico (Rico Arm) of Lago Argentino, in Parque Nacional Los Glaciares. Water builds up behind this natural "dam" until the ice can no longer hold the weight of the water behind it, and it explodes in a rush of ice and water toward the main glacial trough.
This happened 15 times in the 20th century, and most recently in 2004, when I missed it by just a couple days. It's always been a summer event, as optimum seasonal temperatures presumably weaken the ice, but authorities are expecting the glacier's first winter rupture at any time. Today I hope to consult a climatologist friend, who's worked on the glacier, to get his take on any link to global warming.
Only a handful of visitors, about 400, are on the scene, compared with the many thousands who visit the park every summer. There's a good report, with video footage, at the website of the Buenos Aires daily Clarín.