Why This Massive Glacial Arch Collapses Like Clockwork

Like semi-reliable clockwork, tourists visiting Los Glaciares National Park in Argentina can expect that the Perito Moreno glacier arch will fall.

Every two to four years, the large arch of blue and white ice thunderously collapses into the glacial Lake Argentino below. Around mid-March, tourists flock to see the spectacle in the national park, which is in southwest Argentina on the border with Chile, in the Patagonia region.

On Sunday, the glacier evaded the public eye by collapsing in the middle of the night. The park had been closed because of a storm, leaving tourists disappointed.

In 2016, the Perito Moreno put on a more dramatic show in front of thousands of tourists. Then, it collapsed during the day and was caught on camera.

What Causes the Collapse?

Argentina's famous cyclical monument has a demise fueled by its own creation. Collapse begins when the melt from the glacier drains into a lake, which rises and eventually begins forming a tunnel through the glacier. It follows what's known as Archimedes's principle, local research center Glaciarium told the AFP in 2016. (The principle holds that the force exerted on an object in water is equal to the fluid that's displaced.)

Despite this year's missed opportunity, tourists should get another chance to watch the glacier collapse in two to four years. Perito Moreno is one of the only glaciers in the world that is growing instead of shrinking. Exactly why the glacier is growing while others around the world are shrinking is a bit mysterious. Scientists suspect the glacier's steep angle may be making it more resilient.

Natural Wonders

In addition to the large, nearly 200-foot-tall glacier, the Argentinian park is home to an abundance of natural wonders, including two other large glaciers. Near Lake Argentino, Lake Viedma is also fed by the melting waters. The park is a UNESCO World Heritage Site that spans 600,000 hectares and contains an enormous freshwater reservoir.

The park's large glaciers are fed by the South Patagonia Ice Field, and it's surrounded by the Patagonian Andes.

Its remoteness and relatively pristine environment allows visitors a rare glimpse at a largely untouched ecosystem.

To reach Los Glaciares, the park's website recommends traveling from the nearest town El Calafate, which sits on the southern edge of Lake Argentino. Tour groups offer day trips into the park to see the Perito Moreno glacier.