Geography Rivers

• Explain the formation of a Waterfall. (4)

  A waterfall is formed when a river flows over a layer of hard rock that is on top of a layer of soft rock.

  The soft rock is eroded more quickly, and undercuts the hard rock, creating a plunge pool. (1)

  This is done through the process of abrasion, (rocks scraping the river bed making it deeper.) (1)

  The hard rock is then left unsupported and eventually collapses due to gravity. (1)

  The process continues and over time the waterfall retreats to form a gorge. (1)
• Explain the formation of a Meander. (4)

  In it‘s middle and lower course, a river rarely flows in a straight line because water flows laterally, (side to side), over flatter land. (1)

  The water flows faster around the outside bend and so erosion carves out a river cliff. (1)

  Materials carried within the water are thrown against the river banks, wearing them away through the process of abrasion, (rocks scraping away at the river bed making it deeper.) (1)

  The water flows more slowly around the inside bend and so deposits a variety of materials which builds up a river beach. (1)
• Explain the formation of an Ox Bow Lake. (4)

  The faster water erodes the outisde bends of a meander whilst the slower water deposits material on the inside of a meander. (1)

  This causes the neck of the meander to get narrower When the river floods, the river breaks through the narrow neck and leaves the old meander abandoned. (1)

  The ends of the meander are sealed off due to deposition. (1)

  This leaves a crescent shape or ox-bow lake. Eventually the water left in the ox-bow lake may evaporate or become filled in with soil. (1)
• Explain the formation of a V Shaped Valley. (4)

  A V Shaped Valley is found in the upper course of a river where the land is steep and the river is fast flowing, so vertical erosion occurs. (1)

  Abrasion, (where rocks scrape away at the river making it deeper), deepens the valley floor. (1)

  The valley sides are exposed to freeze thaw weathering, (water enters cracks in the river bed, freezes, then expands.) (1)

  These processes widen and deepen the valley meaning the valley sides are left unsupported and collapse into the river. (1)