When a glacier calves, it breaks off a large chunk of ice that falls into the ocean or a lake, creating icebergs. Picture a massive wall of ice at the edge of a glacier, towering over the water like a frozen cliff. Suddenly, with a thunderous crack that echoes for miles, a house-sized piece breaks away and crashes into the sea with an enormous splash. That's calving.

Scientists study glacier calving because it shows how glaciers are changing. Some calving is natural: glaciers flow slowly toward the ocean, and when the ice reaches the water's edge, pieces naturally break off. But the rate of calving can indicate whether a glacier is advancing or retreating.

Videos of glaciers calving are spectacular but also a bit frightening. The sound is like thunder mixed with cracking glass, and the splash can create waves that travel far across the water. Ships have to stay a safe distance away when they're near calving glaciers.

The word can also describe an iceberg splitting into smaller pieces, though this usage is less common.