It's known as "calving." A large chunk of ice breaks off the face of a glacier and thunders to the water below, generating a series of potentially dangerous waves.
Click play to view this amazing footage.
This video from Antarctica is rich for all of the elements it captures: the sounds of the glacier calving, the icy waves rolling ominously toward the camera, the kayakers paddling out of the break zone, a mother ship in the distance, inflatables pulled up on the beach, even the sounds of penguins.
Just another day at the bottom of the world.