erosional landforms

• what is a cirque/corrie? (erosional)

  A Corrie can be described as an armchair shaped hollow on a hillside above a glacial valley
• How is a cirque formed?

  1st Snow gathers in a hollow and begins to compress and turn into ice which further erodes the hollow on the side of a cliff. This is known as nivation

  2nd the ice gains a rotational movement under its weight enlarging the hollow further

  3rd the rotational movement also causes plucking of the back wall of the hollow making it steep

  4th the ice melts and leaves behind a large hollow in the side of a cliff
• what is an arete(erosional)

  An arete can be described as a narrow ridge between two corries
• how is an arete formed

  As two corries are enlarged back to back, the ridge between them becomes increasingly narrowed which is known as an arete
• what is a pyramidal peak? (erosional)

  A pyramidal peak is a sharp pointed hilltop where three or more corries develop around a hill to form a point
• how is a pyramidal peak formed?

  Occurs when several corries are eroded side to side
• what is a glacial trough? (erosional)


  Glacial troughs can be described as a steep-sided flat floored straight valley
• How is a glacial trough formed?

  Glaciers flow down pre-existing river valleys under gravity. It then erodes the sides and floor of the valley causing the shape to become deeper, wider and straighter. The mass of the ice has more erosive power than the river
• what are truncated spurs? (erosional)


  A truncated spur can be described as a steep and possibly rocky section of the side of a trough
• how are truncated spurs formed?

  They are created as preglacial interlocking spurs are eroded away by the power of a large glacier. This leaves behind steep sides which are known as truncated spurs
• what is a hanging valley (erosional)

  Can be described as a small tributary valley high above the floor of a glacial trough
• how is a hanging valley formed?

  A hanging valley is usually formed when the lower valley has a greater rate of erosion which can be caused by 2 glacial flows, one feeding the other.

  It could also be caused by soft rock layers being eroded being more quickly
• what is a ribbon lake? (erosional)

  A ribbon lake can be described as a long, narrow lake along the floor of a glacial trough
• how is a ribbon lake formed?

  Areas of increased plucking and abrasion by the valley glacier deepen part of the valley floor, as a result of either the confluence of glaciers or weaker rocks.

  As a glacier flows over the land, it flows over hard and softer resistant rock. The softer rock is more likely to be eroded by a glacier leaving behind a deeper trough. Melted water will begin to gather in this trough and form a ribbon lake
• what are striations? (erosional)

  Can be described as Scratches or grooves in rock
• how are striations formed?

  Striations are formed when debris embedded in the base of a glacier scratching the bedrock
• What is a roche moutonnee? (erosional)

  Can be described as asymmetrical, bare rock outcrop with a gently sloping side facing up-valley
• How is a Roche moutonnee formed?

  Projections or resistant rock are sometimes found on the floor of glacial trough. As advancing ice passes over them, there is localised pressure melting on the up-valley side area is smoothed and streamlined by abrasion. On the leeward side, pressure is reduced, refreezing occurs and plucking takes place, causing a steep jagged slope.
• what is an ellipsoidal basin? (erosional)


  Large shallow basins with planforms similar to an ellipse
• how is an ellipsoidal basin formed?

  Formed by subglacial activity.

  Is eroded by ice sheet with the surface also being lowered due to the weight of the ice mass