Glacial Deposits
Thousands of years ago, snow fell year-round over large areas of Asia, Europe, and North America. Over time, the weight of snow from the top added pressure below. Slowly, the snow turned to ice. Glaciers were formed.
The ice's weight became so great that it pushed and dented the land. These moving masses of ice were tremendous forces of erosion. Huge amounts of soil and rock were pushed ahead of the ice and carried along in the glacier's bottom layers. After thousands of years, the ice began to melt. As the ice melted, it left behind a changed landscape. |
The rock material deposited by a glacier is known as till. Till may be silt, sand, gravel, boulders, or sharp rocks. Some till is picked up as a glacier scrapes Earth's surface. The glacier drags till along its icy base.
A glacier also deposits till at its front, or snout. Such deposits are called moraines. Streams flowing through tunnels in melting glaciers deposit sand and gravel in ridges, too. These winding ridges are called eskers.
A glacier also deposits till at its front, or snout. Such deposits are called moraines. Streams flowing through tunnels in melting glaciers deposit sand and gravel in ridges, too. These winding ridges are called eskers.