Glaciers What is a glacier Glaciers begin to

Glaciers

What is a glacier?

Glaciers begin to form when snow remains in the same area year-round and transforms into ice. There are two main types of glaciers: alpine glaciers and continental glaciers.

You can only see the effects of a glacier after the ice melts. We investigate past glaciated areas to find out what to expect from current glaciers. Learn more about these changes at Montana’s Glacier National Park…

Alpine Glaciers These glaciers can be recognized by mountains with jagged peaks and broad (U-shaped) valleys. The Rocky Mountains show evidence of valley glaciers.

Glaciers act as conveyor belts to transport sediment down valleys.

Lateral Moraine / Till: a ridge of glacial sediment along the sides of a glacier.

Medial Moraine: a ridge of till formed in the middle of the glacier when lateral moraines meet.

Crevasse: a deep crack in the surface of a glacier.

Snowline: the line where the accumulating snow meets the glacier.

Zone of Accumulation: coldest part of the glacier where snow falls but does not melt.

Zone of Ablation: the area where ice leaves the glacier.

Melting occurs all over the glacier. Calving, when large chunks of ice break off, only happens at the zone of ablation. See a glacier “give birth” to icebergs and watch people freak out…

Continental Glaciers These glaciers are also known as ice sheets and cover large parts of land flow in all directions. Greenland Antarctica are covered by continental glaciers. Continental glaciers smooth the landscape to produce gently rolling hills.

Creating A Glacier Model Materials: Dirty ice cube, paper plate, clay. Objective: Create a model of glacial erosion. Procedure: (1) Spread the clay into a layer across the bottom of the plate. (2) Scrape your glacier, gravel-side down, slowly over the clay IN ONE DIRECTION. Observations: Describe the impressions left in the clay. Is anything left behind after the “glacier” moves across the surface?

Ice Cube Model Analysis 1. Do you notice an features that look like crevasses? 2. How is the sediment distributed throughout the model? 3. How was the landscape affected by the sediment in the “glacier”?

Types of Glacial Erosion 1. 2. 3. * Freeze-thaw, which is the action of glacial water on cracks or hollows in rock surfaces. Water expands/freezes and contracts/thaws in the cracks, which eventually causes the rocks to break up. Plucking, which occurs when the glacier moves over land. Rocks freeze to the base and are picked up from the ground, proceeding to move with the glacier. Abrasion, which occurs when rocks at the base of the glacier rub against the bedrock and wear on the landscape. The processes do not necessarily happen in isolation; any two or all three can happen at the same time as a glacier advances.

Glacial / Ice Ages Periods of extreme global cooling when much of the planet is covered by continental glaciers. This causes sea levels to fall because most of the Earth’s fresh water is frozen as ice.

The last glacial/ice age only ended 15, 000 years ago. What are the glacial ages and what may cause them?