2.4.6

Fluvioglaciation

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Fluvioglacial Processes

Glacial meltwater plays a significant role in glaciated landscapes. The meltwater may have been beneath (subglacial), within (englacial) or on top of (supraglacial) the glacier.

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Fluvioglacial processes

  • Meltwater can flow subglacially, often a high pressure, and can erode channel networks.
  • Most meltwater emerges either on the side of a glacier or at its snout.
  • The amount of water emerging from the snout can be large, especially in spring and summer.
  • Meltwater usually has a lot of sediment in it and appears cloudy.
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Glacial vs fluvioglacial

  • Glacial deposits tend to be unstratified (un-layered) whereas fluvioglacial are more stratified.
  • Glacial deposits are poorly sorted (into different particle sizes), whereas fluvioglacial deposits are well-sorted.
  • Glacial deposits have random long-axis alignment whereas fluvioglacial deposits tend to have dominant directions of alignment.
  • Glacial deposits show little sign of grading (deposition by size - larger particles first) but fluvioglacial deposits are well-graded, with sediment being smaller with distance from the glacier.

Eskers, Kames and Kame Terraces

A wide range of landforms are created by fluvioglacial processes.

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Eskers

  • Eskers are when subglacial, englacial or supraglacial river channels get filled with sediment.
  • When the ice melts away it leaves behind these long, thin ridges made of sand and gravel which can be up to 100 m in height and extend for many kilometres.
  • Supraglacial and englacial eskers often have beaded (flattened) shapes but subglacial eskers are often more peaked.
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Kames and kame terraces

  • Kames are features produced at the edges of a glacier or ice sheet.
  • They consist of irregular mounds of sands and gravels.
  • They are often found in a group and look like cones or deltas deposited unevenly along the edges of a melting ice sheet.
  • Where lots of kames occur together, they create ‘benches’ of deposits on valley sides called kame terraces.

Other Proglacial Features

Apart from eskers, kames and kame terraces, there are other proglacial landforms.

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Sandhur

  • Sandhur are large areas of sandy and pebbly material washed out of the ice by meltwater streams.
  • These streams carry a lot of debris in braided channels which leave the largest deposits nearest the ice front and carry finer particles further across the plain.
  • The deposits appear in layers showing the larger deposits occurring each spring with the increased meltwater.
    • E.g. there are lots of sandhur in coastal Iceland.
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Meltwater features

  • Pro-glacial lakes are lakes formed in front of an ice mass from meltwater.
  • Meltwater channels are eroded by streams draining away from the ice margin. These channels follow the slope of the land and are often wide and braided.
  • Kettle holes are small, often circular, lakes formed by the melting of ice blocks left by the retreating glacier.
    • E.g. in north Cheshire, seen from planes as you take off from Manchester Airport.

Jump to other topics

1Tectonic Processes & Hazards

2Option 2A: Glaciated Landscapes & Change

3Option 2B: Coastal Landscapes & Change

4Globalisation

5Option 4A: Regenerating Places

6Option 4B: Diverse Places

7The Water Cycle & Water Insecurity (A2 only)

8The Carbon Cycle & Energy Security (A2 only)

9Superpowers (A2 only)

10Option 8A: Health & Human Rights (A2 only)

11Option 8B: Migration & Identity (A2 only)

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