Glacial Landforms

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Glacial Landforms
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Much of glacial erosion is exerted on the bottoms
and sides of alpine valleys that guide the flow
of glaciers.
The glacial erosion causes the bottom and the
sides of any glaciated valley to become both
wider and deeper over time.
Glacial erosion also results in a change in the
valley's cross-sectional shape.
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Glacial valleys tend to have a pronounced U-shape
that contrasts sharply with V-shape valley
created by stream erosion.
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Hanging Valley   A secondary valley that
enters a main valley at an elevation well above
the main valley's floor.
Hanging valleys are the product of different
rates of erosion between the main valley and the
valleys that enter it along its sides.
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Some of the other features associated with
glacier erosion in alpine regions are cirques,
horns, and arêtes.
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Cirque
Glacially eroded rock basin found on mountains.
Most alpine glaciers originate from a cirque.
The glaciers that occupy cirques are called
cirque glaciers.
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Cirque glaciers are framed on three sides by rock
walls.
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Horn   Pyramidal peak that forms when several
cirques erode a mountain from three or more
sides.
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Arête   Sharp topographic ridge that separates
cirques on a mountain that is or has been
glaciated.
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Ice sheet Landforms
The erosional landforms produced by continental
glaciers are usually less obvious than those
created by alpine glaciers.
Much of the Canadian Shield shows the effects of
abrasion and gouging which created glacial polish
and striations on bedrock surfaces.
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Glacial Deposits
Large quantities of sediment are picked up by
abrasion and plucking at the base of the ice.
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In alpine areas, sediment is added to the surface
of the glacier from the valley walls through
various types of mass movement.
Much of the debris that is added to the ice of
the glacier is eventually delivered to the snout
because of the continual forward flow of glacial
ice.
From the snout this material can be placed
directly from the ice or it can be deposited
through the action of flowing meltwater.
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The technical term used to describe material
deposited by the ice is called till or moraine.
All glacial deposits in general are known as
glacial drift.
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Till is a heterogeneous combination of
unstratified sediments ranging in size from large
boulders to minute particles of clay.
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When till is deposited along the edge of a
glacier it tends to form irregular hills and
mounds known as moraines.
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A terminal (end) moraine is a deposit that marks
the farthest advance of a glacier.
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The debris that falls from valley side slopes can
be concentrated in a narrow belt and cause a
deposit known as a lateral moraine.
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Moraine deposits created during halts in the
retreat of the glacier are called recessional end
moraines.
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When two glaciers flow together, two lateral
moraines can merge to form an interior belt of
debris, called a medial moraine.