Glacial Systems, Processes and Landforms

What is a Glacier? Glaciers are large masses of snow, re-crystallized ice and rock debris that accumulate in great quantities and begin to flow outwards and downwards under the pressure of their own weight. Glaciers form when yearly snowfall in a region far exceeds the amount of snow and ice that melts in a given summer. In this way, massive quantities of material accumulate in relatively small periods of geologic time.

Ice field on high plateau Direction of Glacier Flow Downhill Inputs Inputs Direction of Glacier Flow Downhill Meltwater One of the many glaciers in Glacier Bay National Park

Glacier in Alaska Moraine Path of Glacier during the last ice age.

Meltwater Friction of moving ice on solid rock heats the base of the glacier causing a stream of water at the base of the glacier.

Walking on a glacier can be very dangerous. Why?

Glacial Landforms Arête is a steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge.

Glacial Landforms A Cirque is a semicircular or amphitheater-shaped bedrock feature created as glaciers scour back into the mountain. This is where the snow and ice forming the glacier first accumulates; it is the "headwaters" of a glacier.

Glacial Landforms A corrie starts as a snow patch on a cold mountain side. The temperatures must be low enough to allow the snow to remain all year round. Under these conditions snow can accumulate and the snow patch will grow in size and depth each year.

Glacial Landforms An icefield is an accumulation of snow ice that feeds at least three glaciers.

Glacial Landforms A Hanging Valley is a valley eroded by a small tributary glacier, such that the elevation of the valley floor is higher than the elevation of the valley floor that the hanging valley joins. The erosive power of glaciers is dictated by their size: the larger a glacier, the farther down into the landscape it can erode. Thus the valley floors of small tributary glaciers will be higher in elevation that the valley floor of the larger glacier that the small tributary glacier joins.

Glacial Landforms A Horn is a pyramid-shaped mountain peak created by several glaciers eroding away at different sides of the same mountain.

Glacial Landforms A col is a low spot or pass along a cirque or an arête.

Glacial Landforms A’U’ shaped valley is a valley that has been formed by the force of a glacier. It gets its name from its U shape.

Glacial Landforms What type of valleys are there? Rivers cause ‘V’ shaped valleys and ‘U’ shaped valleys are formed by glaciers.

Glacial Landforms Can you spot the following features; Cirques Horns Cols Arêtes Glacier

Glacial Processes Glaciers are responsible for large amounts of erosion. The first main type is ‘Abrasion’. This occurs when the material being carried by the glacier rubs against the valley floor like sand paper. This wears away the valley floor and sides making it deeper and wider. ‘Plucking’ occurs when the glacier freezes onto rocks and boulders carrying them along the glaciers path. At the base of each glacier is the build up of ‘moraine’.

Glacial Processes Stream flowing from the melt water Terminal Moraine Medial Moraine Lateral Moraine Stream flowing from the melt water

Glacial Processes

Test yourself Name the following features Icefield Glacier Arête Cirque Horn U Shaped Valley