Landforms Made by Glaciers

Continental Glaciation

The main difference between the two forms of Glaciation (Alpine and Continental) is where they occur. However, there is also some distinction in the resulting landforms as well.

Moraine: Material transported by a glacier and then deposited

Drumlin: Drumlins are formed of till. They are elongated features that can reach a kilometer or more in length, 500m or so in width and over 50m in height. The Stoss end is the steeper of the two ends and used to face into the ice flow.

Esker: Produced as a result of running water in, on or under the glacier. They are linear mounds of sand and gravel that commonly snake their way across the landscape. They are the deposits of rivers and streams that flowed on, in or under a glacier .

To areas in the world experiencing an ice age at present are Greenland and Antarctica.

Glaciers scrape and scour

The features produced by Continental Glaciation

1. The Canadian shield: Scoured region; little soil cover, dotted with lakes occupying depressions formed by the scouring action of glaciers.

Striations: Glacial scratches on exposed rock.

Glacial till: Debris left by a glacier consisting of fragments and chips of earth (angular in shape and unsorted. (Note: River Deposits are generally rounded and sorted)

Ground moraine: Layer of till that covers the underlying bedrock (several centimeters or meters thick)

Erratics: isolated boulders or misfits left by a glacier

Terminal moraine: Line of hills marking the maximum extent of the ice sheet

Recessional moraine: Debris left by a glacier that maintained a constant position for a considerable length of time.

Interlobate moraine: Debris left between the space of two glaciers which closely approached each other.

Drumlins: Odd tear-shaped hills (7.5-30 m high). Steep end faces the direction the ice came from.

Features produced by the melting of ice

Outwash plain: Deposition of water at the end of the ice sheet.

Kettle lakes: Hollows filled with water.

Spillway: A valley formed by a river of melt water carving into the landscape.

Misfit streams: The streams found in a spillway. Very small in comparison to the size of the valley they are flowing in. The river that would have formed these valleys would have been much bigger.

Eskers: Long snake like formations consisting of sands and gravels left by glacial streams. Serve as road building materials.

Glacial Ponding: Body of water formed as a result of melt water not being able to flow away.

Note: The features shared by both Alpine and Continental Glaciation are: Till, Striations, Terminal Moraine, Erratics, Crevasses.

Significance of Glaciation in North America

• Glaciers removed fertile soil from the Canadian Shield, exposing bedrock containing valuable minerals
  
  
• Rivers and lakes that resulted from Glaciation act as a source of hydroelectric power.
  
  
• The Canadian Shield with its many lakes is a tourist attraction
  
  
• Glacial Till of South Ontario formed a gently rolling landscape with good drainage and easily cultivated soil.
  
  
• The till is derived from limestone bedrock, therefore it's a natural, built-in, fertilizer.
  
  
• The Great Lakes, surrounded by fertile plains of clay and sandy loams.
  
  
• Deepening of river valleys by glaciers allowed the Great Lakes to form along with the St. Lawrence seaway, which is one of the most important inland waterways in the world.
  
  
• Prairies received valuable soil deposits carried by glaciers.
  
  
• Alpine Glaciation:
  

  - Made the Rockies a big tourist attraction
  - Transportation routes in troughs left by the ice
  - Fjords act as sheltered harbours

  
  
  
• In parts of Canada, the land continues to rise after the glaciers have departed (i.e. Isostatic Rebound.) Around Hudson bay, this could eventually cause some rivers to switch their direction of flow from the north to the south.

Glacial Movement

Glacial Flow is caused by glacial creep and basal sliding.

Glacial Creep: Occurs due to the tremendous weight and pressure of the glacier, the ice becomes pliable and flows. It flows fastest in the middle of the glacier, where it is thickest.

Basal sliding: Movement along the bottom of the glacier, due to the warmth of the earth and internal streams.

The key to whether a glacier advances or retreats depends on the two opposing forces of accumulation and ablation. Ablation is the wasting or loss of material from the glacier.

if Accumulation > Ablation, the Tip of the glacier advances.
if Accumulation = Ablation, the Tip of the glacier is stationary.
if Accumulation < Ablation, the Tip of the glacier retreats.

Keep in mind that even when the tip of the glacier is retreating or stationary, the internal flow of the ice still goes throughout the glacier. The flow continues to move the ice forward, but the forward movement is offset by the loss of ice from ablation.

Glacial Erosion

Quarrying or Plucking: Caused by 'freeze-thaw' action.

Abrasion: Scraping or gouging by an ice sheet and debris it moves.