Glaciers

Chapter 8 Section 4

Kinds of Glaciers Glacier- any large mass of ice that moves

slowly over land Valley glacier- a long, narrow glacier that

forms when snow and ice build up high in a mountain valley

Continental glacier- covers much of a continent or large island; much larger than valley glaciers

Ice Ages How Glaciers Form & Move

Ice ages- times in the past when scientists believe continental glaciers have covered large parts of Earth’s surface

Glaciers form in an area where more snow falls than melts

The pressure of the weight of more and more snow compacts the snow into ice

Valley glaciers move slowly while surging glaciers can move several miles a year

Glacial Erosion Glacial Deposition

The movement of glaciers changes the land beneath it

Plucking- process in which a glacier flows over the land and picks up rock

When a glacier melts, it deposits the sediment it eroded from the land, creating various landforms

Till- mixture of sediments of clay, silt, sand, gravel, and boulders that a glacier deposits directly on the surface

Moraine- the ridge formed at the edge of a glacier as till is deposited

Glacial Deposition Retreating glaciers create kettles Kettles are small depressions that form when

a chunk of ice is left in glacial till Kettles often fill with water to create lakes

Review How are valley glaciers and continental glaciers different?

Valley glaciers are found in high mountains, and the sides of the mountains keep these glaciers from spreading out. Continental glaciers cover much of a continent or large island.

What are two types of glacial erosion?Plucking and abrasion

Describe three features formed by glacial deposition.Moraine, prairie pothole, kettle, drumlin, or glacial lake

Driving through the countryside in Michigan, you and your family come upon a series of small, round lakes. Explain the process that formed these features.These lakes are kettle lakes, which form when a chunk of glacier is left behind in glacial till. When the ice melts, a depression called a kettle remains in the ice. A kettle filled with water is called a kettle lake.