72974
Glacial
erosional
landforms
- Cirques
- Armchair shaped hollow, steep back wall of
angle 60 degrees.
- Hollow itself is often overdeepened,
characterised by rock lip. Hollow may contain
a tarn.
- Red Tarn, Lake District
- Red Tarn, Lake District
- Examples: Cwm Idwal, Snowdonia.
- Formation
- Early stages of glaciation
- Corrie formation begins with enlargement of
small hollow on hillside. Where snow
accumulates year on year in small hollow,
nivation processes operate, enlarging hollow
and creating embryo corrie. As snow continues
to accumulate, firn ice created. Eventually
compressed to form true glacial ice.
- During glaciation
- Once critical depth of ice reached, ice
moves through hollow in rotational manner,
enlarging the hollow. Back wall is
steepened through plucking and
frost-shattering and base of corrie
overdeepened by abrasion.
- Abrasion is facilitated by frost
shattered material from back wall
falling down Bergschrund crevasse
at back. The thinner ice at front has
less erosive power and rock lip
develops at threshold of corrie.
- Lip of corrie may
be heightened
further by
deposition of
moraine as ice
moves out of the
glacier.
- Post glacial
- Once ice retreated,
corrie basin may become
filled with water creating a
tarn lake.
- Once ice retreated,
corrie basin may become
filled with water creating a
tarn lake.
- Post glacial
- Lip of corrie may
be heightened
further by
deposition of
moraine as ice
moves out of the
glacier.
- Abrasion is facilitated by frost
shattered material from back wall
falling down Bergschrund crevasse
at back. The thinner ice at front has
less erosive power and rock lip
develops at threshold of corrie.
- Once critical depth of ice reached, ice
moves through hollow in rotational manner,
enlarging the hollow. Back wall is
steepened through plucking and
frost-shattering and base of corrie
overdeepened by abrasion.
- During glaciation
- Corrie formation begins with enlargement of
small hollow on hillside. Where snow
accumulates year on year in small hollow,
nivation processes operate, enlarging hollow
and creating embryo corrie. As snow continues
to accumulate, firn ice created. Eventually
compressed to form true glacial ice.
- Early stages of glaciation
- Armchair shaped hollow, steep back wall of
angle 60 degrees.
- Arete
- Steep knife-edged ridge which
separates two corries or troughs.
- Example - Striding Edge, Lake District
- As two corries erode back to back, erosion
of headwalls due to plucking and abasion
results in formation of knife-shaped ridge
between the two corries.
- Steep knife-edged ridge which
separates two corries or troughs.
- Pyramidal peak
- An angular glaciated mountain peak with three or more
steep sides - usually back of corries.
- Each side is separated by a sharp knife-edged ridge known as an arete
- Each side is separated by a sharp knife-edged ridge known as an arete
- The Matterhorn (Swiss Alps)
- Form when three or more cores around a mountain top have eroded. Their headwalls
have retreated towards each other. The remaining mass between the cores is
steepened, forming a pyramidal peak
- The peak may be very sharp looking due to the action of frost shattering
- The peak may be very sharp looking due to the action of frost shattering
- An angular glaciated mountain peak with three or more
steep sides - usually back of corries.
- Diffluence Col
- A lower area of an arete or pass which breaches the watershed
- This is where a large accumulation of ice, overspills into
adjacent corrie, eroding a ''col' in the headwall, lowest part of
arete
- This is where a large accumulation of ice, overspills into
adjacent corrie, eroding a ''col' in the headwall, lowest part of
arete
- A lower area of an arete or pass which breaches the watershed
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