interlocking spurs

• interlocking spurs are an example of erosion
• interlocking spurs

  projections of high land that alternate from either side of a valley and project into the valley floor
• where are interlocking spurs found

  the upper course where rocks are hard, eg Afon Duas Valley, a tributary of the river severn
• characteristics of interlocking spurs:

  • a steep gradient
  • convex slopes
  • project from alternate sides of the valley
  • separated by a narrow valley floor mostly taken up by the river channel
  • sometimes wooded
• stage 1

  in the upper course of a river, the rivers water volume and discharge are low. the river uses most of its energy overcoming friction with the channel. what energy it has left over is used by hydraulic action to deepen the channel (vertical erosion)
• stage 2

  in upland areas, the geology is composed of hard rock such as granite or slate. however, freeze-thaw weathering (when water gets into cracks in rocks and freezes at night and thaws by day) gradually broadens it out. this gives the valley a steep, V-shaped cross profile. repeated weathering weakens the rock so fragments break loose and tumble down the hillside as scree, which the river then removes
• stage 3

  the winding path taken by the river is due to obstacles of harder rock in its path. the river takes the easiest route over the land. this results in projections of high land entering the valley from alternate sides. these projections are interlocking spurs
• 1= very steep V-shaped valley, river takes up most of the valley floor

  2 = freeze-thaw weathering widens the valley a little

  3= spurs of high land enter valley floor from alternate sides of the valley which are interlocking spurs

  A) 1

  B) 2

  C) 3