Glacial landforms

• Erratics


  Ingleborough, Yorkshire dales

  An individual piece of rock is picked up and carried by the ice to be deposited in areas of completely different geology.

  Depositional landform.
• Drumlins


  E.g. Risebrigg Hill, North Yorkshire

  Smooth, elongated mounds of till (unsorted rock, clay and sand deposited by ice).

  The long axis runs parallel to the direction of ice movement.

  Can be 50 m high and over 1 km in length.

  They are smoothed by abrasion with a steep upstream side and a gently sloping downside. I a group they form a ‘swarm’.

  Depositional landform.
• Till sheets


  E.g. Minnesota, USA

  Often found behind a terminal moraine in low-lying areas.

  Wide areas of flat relief where this is a covering of glacial till (sand and gravel).

  They are significant because of their extent.

  They are variable in composition depending on the nature of the rocks over which the ice has moved.

  Depositional landform.
• Moraines

  E.g. Meade Glacier, Alaska

  created when debris carried by a glacier is deposited.

  Lateral; derived from frost shattering on the valley sides, carried at the edge of a glacier; on melting, a side embankment is formed.

  Push; form if the climate deteriorates and the ice advances

  Recessional; mark an interruption in the retreat of the ice.

  Terminal; a high mound extending across the valley to mark the maximum advance of the ice sheet.

  Medial; the merging of two lateral moraines.

  Depositional landforms.
• Corries / cirques


  E.g. Red Tarn Corries, Lake District

  Armchair shaped rock basins with a rock lip cut into mountains. Mostly occurin on north- and east- facing slopes where less insulation allows snow to accumulate.

  Formed via freeze-thaw weathering, abrasion and plucking.

  Can form tarn lake in the crevasse that is blocked off by the rock bar.

  Erosional landform.
• Arête


  E.g. Striding Edge above Red Tarn, Lake District.

  Formed where two corries lie back-to-back to form a sharp edge.

  Erosional landform.
• Pyramidal peak

  E.g. Machhapuchhre, Nepal

  If more than two corries back into each other on a mountain, the remaining central mass forms a spire.

  Erosional landform.
• Glacial troughs

  When glaciers flow down pre-existing river valleys, and erode the V shape into a U shape that are straight, wide-based, and steep-sided.

  Erosional landforms.
• Hanging valley

  the slower rate of erosion in between main glacier and the valley of a tributary results in the tributary valley being left ‘hanging’ when the ice melts.

  Often results in waterfalls that join the post-glacial river.

  Erosional landform.
• Roche moutonnée

  Occurs due to the areas of resistant rock on the valley floor are not completely removed.

  Has a smooth up-valley side created by abrasion and a jagged down-valley side due to the action of plucking.

  Erosional landform.
• Truncated spurs


  Areas of land protrude from the river valley side (spurs) are removed by the glacier.
• Striations


  Scratches or grooves made by debris embedded in the base of a glacier.
• Kames


  Undulating, winding mounds of unevenly deposited sand and gravel.

  Kame terraces are flat areas formed along the side of valleys.

  They follow the direction of ice advance.

  Glucio-fluvial landforms.
• Eskers


  Long narrow ridges of sorted, stratified, coarse sand and gravel. Deltaic deposits are left when meltwater flows into a lake trapped by moraine deposits.

  Glacio-fluvial landforms.
• Outwash plains (sandur)


  E.g. Skeidarár Sandur, Iceland

  Deposits by meltwater streams running out from the snout of the glacier.

  Composition is of coarse material, which is found near to the glacier, and finer clay, which is carried across the plain before bing deposited.

  Glacio-fluvial landforms
• Kettle holes

  Small depressions formed when blocks of ice that have been washed onto the plain melt and leave a gap in the sediment.

  Glacio-fluvial landforms.
• Patterned ground


  E.g. Barrow, Alaska

  Reflected the repeated cycles of freezing and thawing of the active layer. Rock particles are distributed in a system of polygons and circles.

  Frost heave pushes larger stones to the surface and because of the camber, stone move sideways.

  Periglacial landform.
• Ice wedges


  narrow, frost-formed cracks in the upper layers of the ground which fill with ice. They can be up to 10m in depth.

  Periglacial landform.
• Pingos


  E.g. Northern Canada

  dome-shaped, ice-cored mound of earth.

  closed system; in areas of continuous permafrost, develop beneath lake beds.

  Open system: in areas of discontinuous permafrost, found in valley bottoms.

  Periglacial landform
• Blockfields


  Scafell Ranges, Lake District

  Freeze-thaw action produces large amounts of scree which forms scree slopes. Formed in flat areas expansive areas of angular boulders.

  Periglacial landform.
• Solifluction


  E.g. Oglivie Mountains, Canada

  the slow flow of saturated regolith down a gradient which can be very gentle.