Icebergs break off pieces of themselves all the time. It's calling "calving", and it's part of the natural process of a glacier melting and refreezing. But it's one thing to read about it, and another to see it actually happening.

This is a chunk of Argentina's Upsala glacier, found in Argentina's Los Glaciares National Park. Yes, they have a national park just named "The Glaciers." Guess what you find there!

This video was taken by an amateur outdoorswoman as she was riding by on a catamaran. It really demonstrates the sheer power and strength of these massive ice cubes. It's extremely rare to see this powerful force of nature at work, mostly because these glaciers are huge and anybody sensible stays far, far away from this happening. So, thanks, Argentina, for risking your necks for our enlightenment and amusement!