With a rumble, and then a roar, an enormous ice bridge connected to a glacier in Argentina crashed into the lake below it, creating a mini-tidal wave, but delighting the tourists who happened to witness the event.
In January, a few visitors to the Perito Moreno glacier were able to document the collapse through video and photos. The piece that broke off was part of a massive ice tongue that intersects a part of the Lago Argentino.
Amateur photographer Christian Grosso wrote about the experience for the Earth Science Picture of the Day blog:
The blocked water slowly builds up pressure undermining the ice and eventually forming a cave or tunnel. Over a period of 10 to 50 months, the resulting ice bridge fails crashing into the frozen lake and upon its shore. This phenomenon repeats itself at irregular intervals, with the last two major ice collapses occurring in 2012 and 2008. I was one of perhaps 20 privileged people in Los Glaciares National Park this midsummer day to witness the spectacle.
The Perito Moreno is one of the largest glaciers in Patagonia, according to NASA's Earth Observatory. It extends down from the cold Andes Mountains into the more temperate region around Lago Argentino. NASA notes that the ice dam periodically caused by the Perito Moreno has made it one of the most famous glaciers in the region.
From NASA's Earth Observatory:
The glacier advances right across the lake until it meets the opposite shoreline, and the ice tongue is “grounded” (not floating) so that it forms a natural dam. The ice dam prevents lake water from circulating from one side to the other, which in turn causes muddier and “milkier” water to concentrate in Brazo Rico. Water flows down under the glacier from the mountains, not only carrying the mud into the lake but also helping lubricate the glacier’s downhill movement.
Speaking with OurAmazingPlanet, NASA scientist Jim Foster said the phenomenon is actually quite rare.
"Most glaciers don't have such trajectories, so bridging and tunneling, at least at this scale, is rather rare," he said.
The Perito Moreno previously collapsed in March of 2012, according to The Telegraph. At that time, more than 2,000 people were on hand to watch the ice fall into the lake below.