Hello. I'm M. Jackson. I am a glaciologist. I study glaciers around the world. A glacier is a moving river of ice. It flows over Earth's surface. When a glacier flows into water, the ice can calve, or break off.

A serac is a ridge of ice on the surface of a glacier. These stick up like shark fins. They can be fun to climb. A crevasse is a crack in a glacier. I fell in one, once. Luckily, my team fished me out of the deep, icy crack.