Continental and Alpine Glaciers Continental and Alpine

All glaciers form . . . All glaciers form when the annual snowfall in an area exceeds the annual snow melt Over many years, the snow accumulates, compacts and turns to ice

Glaciers on the move Glaciers “advance” as they get bigger. Advancing glaciers means that more snow and ice are building up than melting Glaciers “retreat” as they get smaller. Retreating glaciers are a sign that snow melt is greater than snow fall.

Glaciers and water Approximately 10% of all land area is currently covered by glaciers Remember: Only 30% of the Earth is land, so 10% of that is only 3% of the earth’s surface Approximately 70% of all fresh water is held in glaciers

Continental glaciers cover vast land areas Today they are only found near the poles in the Arctic and Antarctic

Former Ice sheets The continental glaciers that covered this part of Ohio started in Canada The dark line marks the terminal moraines – piles of till that mark the farthest point the glaciers reached

As glaciers move, they weather rock below them Frost wedging happens below the ice as water seeps into cracks in the rock and refreezes. When it refreezes, chunks of ice are broken off and stuck to the bottom of the glacier. This is known as plucking

Glaciers are agents of weathering, erosion, AND deposition Glaciers transport plucked rocks long distances and deposit them as erratics. Plucked rocks abrade the surface beneath the glacier

Till – deposited by moving ice Glacial deposits Till – deposited by moving ice heterogeneous mixture; sizes are all mixed together Moraines Terminal moraines Recessional moraines Ground moraines Stratified Drift - deposited by running water Stratified drift is made of layers of different sized particles Outwash plains Drumlins Eskers Kames

New York has drumlins! These long, low, teardrop shaped hills form under the moving glacier. In western NY state, there is a region known as the Finger Lakes that contains hundreds of drumlin hills. They have been observed forming under the ice in Antarctica

Glaciers can have tributaries too! As smaller glaciers join a larger one, they create a complex system of valleys At the bottom of the valley, the outwash plain is essentially the delta for the glacier where water runs out and drops its sediment.