Glacial Deposition

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Glacial Deposition

• Higher Geography Lithosphere

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Introduction

• Glaciation effected not only the major mountain
  or upland areas but also the great valleys and
  lowland plains.

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Deposition features include
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Glaciers transport materials in the following
ways

• Subglacial debris moved along the floor of the
  valley either by ice (as ground moraine) or by
  meltwater streams under the glacier.
• Englacial debris carried within the glacier
  itself.
• Supraglacial debris - carried on the surface of
  the glacier.

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Important

• The collective name for all the materials
  (boulders, sands, gravels, clays, etc.) deposited
  by glaciers is drift.

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Drift deposits can be classified into

• Ground moraine (or till) including unsorted
  materials directly deposited by ice.
• Fluvioglacial materials (or outwash) including
  sorted materials deposited by meltwater streams

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Classification

• Features of glacial deposition
• Erratics
• Moraines (terminal, lateral, medial)
• Drumlins

• Features of fluvioglacial deposition
• Outwash plains
• Eskers
• Kames
• Kettleholes

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Ground Moraine Landforms Resulting from Glacial
Deposition

• Higher Geography
• Lithosphere

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Features of glacial deposition

• Erratics
• Moraines
• Drumlins

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Erratics

• Glacially transported blocks of rock

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Moraines

• Moraines form due to
• The dumping of debris due to ablating ice.
• The pushing of loose, ground material by the ice.

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Types of moraine

• Terminal (or end) moraines
• Push moraines
• Lateral moraines
• Medial moraines
• Hummocky moraine?

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Terminal (or end) Moraines
Key points

• Ice bulldozes loose soil and rock in front of it.
• All the moraine was dropped where the ice melted,
  building up small ridges.
• Formed from poorly sorted till that runs across
  the valley at right angles to the direction of
  ice flow.
• Mark the maximum extent that the glacier has
  advanced.

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Push Moraines

• A terminal moraine marks the furthest point that
  the ice has reached.
• If a glacier retreats and then advances again it
  may create a push moraine between the glacier and
  the terminal moraine.

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Lateral Moraines
Key points

• Develop along the edge of an advancing glacier.
• Form from debris eroded by the advancing ice and
  especially from frost-shattered material loosened
  from the valley sides.
• When the supporting ice ablates, lateral moraines
  collapse.

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Medial Moraines

• Medial moraines form on active glaciers where two
  lateral moraines merge when two glaciers flow
  together.

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Drumlins

• Formed in the following ways
• Melting ice deposits large amounts of moraine.
• Forward movement of the ice moulds the moraine to
  form streamline mounds.
• These elliptical hills are made of boulder clay,
  with a steeper upstream side, are called
  drumlins.
• Drumlins are often found in one area as swarms.

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