Ice Ages and Glacial Processes

Ice Ages

• If spring were not scheduled for another 10 million years, it would be an ice age, characterized by a prolonged period of cold with glaciers covering much of the earth.

Glacial Erosion and Deposition

• Glaciers are huge moving mountains of ice that can directly affect the landscape in many ways.
• Glacial erosion is the process of carving and shaping the land beneath a moving glacier.
• As a glacier moves, it plucks up rocks and sediment, which then get stuck to its belly and go along for the ride.
• These particles act like sandpaper and scratch the bedrock below, creating new landscapes.
• Glacial erosion is responsible for creating glacial horns, cirques, and U-shaped valleys.
• Glaciers carve out basins within bedrock that later fill with water, forming lakes.

Glacial Deposition

• Glacial deposition is the settling of sediments left behind by a moving glacier.
• As the melting glacier drops all of the rocks and sediments it previously picked up, it spreads debris over vast areas.
• The unsorted materials moved and deposited by a glacier are known as till.
• Lines of till that form at the edges of past glaciers leave behind landforms known as moraines.
• Moraines form in lines and give a general idea of the boundaries and farthest point that the past glacier reached.
• Drumlins are elongated hills composed of glacial till.

Indirect Effects of Ice Age Glaciers

• One indirect effect is the creation of pluvial lakes, which are lakes that were at one time very large due to excessive rainfall associated with glaciation.
• Pluvial lakes formed in desert areas due to changes in air flows and weather patterns caused by the presence of ice-age glaciers.
• Another indirect effect is isostatic depression, which is the sinking of the earth's crust due to pressure from a heavy weight, such as glaciers.
• When the glacier eventually melts, the earth's crust rebounds, similar to a mattress rebounding when the weight is removed.
• Changes in sea level are also an indirect effect, resulting from the growing and melting of ice age glaciers.
• During the ice ages, water that once filled oceans was turned to ice, resulting in a drop in sea level and the uncovering of large land bridges.