Glacial Boulder

Out-of-place boulders like this one and boulders bigger than your car, called an erratic, were deposited by a glacier. Glaciers result when, for a period of years, more snow falls in an area than melts. Once the snow reaches a certain depth, it turns into ice and begins to move under the force of gravity or the pressure of its own weight. During this movement, rocks are picked up and carried in the ice, and these rocks grind Earth’s surface. Ice and water erode and transport earth materials as well as rocks and sediments.