Physical Geography 102
Glacial Landforms II

Glacial Erosion

Two primary processes
1) Abrasion - scraping action
2) Plucking - dislodgment or lifting action

Ice is a mineral - hardness of 1.5 on Mohs Scale of Hardness
Unable to scratch most rocks and minerals
Abrasion by glaciers is dependent on the sediment dragged along by the flow
Grinds away valley floors and walls
Scratches, striations, grooves and furrows are determined by size of sediment
Direction of striation is a good indicator of flow direction


Fractures must exist in the bedrock if plucking is to occur
Plucking lifts and removes rock from valley floor and walls by shear stress

Alpine Erosional Landforms

Cirque - bowl or amphitheater shaped depression
Arête - sharp, jagged ridge which develops between adjacent glaciers
Horn - sharp, 3-4 sided peak formed by erosion at the heads of at least 3 glacial cirques
Col - depression or low point in an arête; develops where two cirques meet
U-shaped Valley - only visible after the glacier has retreated develops in V-shaped valleys as erosion occurs primarily along the middle of the valley walls

Sediment and Transportation

Till - sediment carried and deposited by glaciers
Sediment is concentrated in 3 areas
1) along the bottom of the glacier
2) along the sides of the glacier
3) in vertical zones in the middle of the flow
Moraines - deposits of glacial till

Types of Moraines

Lateral Moraine - deposit along the sides of the glacier
Medial Moraine - located in the middle of the glacier, parallel to the sides
- formed by the merging of two lateral moraines when two adjacent glaciers merge
Ground Moraine - deposit along the bottom of a glacier
End Moraine - deposit that is being produced at the terminus of an active glacier
Terminal Moraine - an end moraine which marks the maximum advance of a glacier
Interlobate Moraine - lateral or end moraines formed along a line of junction between two glacial lobes

Continental Glacier Landforms

Kettle - steep-sided, basin or bowl-shaped depressions in glacial deposits
- Formed by the melting of a large, detached block of ice that has been completely or partially buried in glacial till
Kettle Lake - kettle that is filled with water
Drumlin - low, smoothly rounded, elongate or oval hill
- Built under the glacier and shaped by its flow
- Long axis is parallel to flow direction
- Composed of glacial till
Esker - long, narrow, sinuous ridge of glacial till
- Formed by streams flowing beneath the glacier
- Fed by melt water from the glacier's surface
Kame - low mounds or knobs (can be irregular in shape) of till deposited in a variety of ways:
- Alluvial fan or delta deposits at the edge of the glacier
- Ponded deposits on the surface of the ice
- Streams flowing on the surface of the ice
Outwash Plain - broad, gently sloping plain where meltwater deposits sediment
- Stratified drift - layered sediment deposited by glacial streams
- Braided streams are common in the outwash area