Youtuber osibaruch, who captured this footage last month, sez:
This Iceberg was “calved” by Argentina’s Uppsala glacier. While we were passing by it with a catamaran, the huge berg lost a part of itself (look at the right side sinking) and then flipped over with a huge roar. In the process of melting this happens all the time, but it is seldom that it is captured on video WHEN it happens…