Spurs and Interlocking Spurs
Spurs, and interlocking spurs, are features found in the upper reaches of river valleys. They are erosional features, meaning that they are formed by water flowing over the land and eroding it as it moves.
Imagine two gently sloping hillsides forming the sides of a small valley. As rain falls on these valley sides, the water runs down hill (it's called run off) towards the bottom of the valley where it joins a small stream. The main process at work in the stream is the downward, or vertical, erosion of its bed.Aswell as eroding downwards, the stream twists and turns as it finds a way round obstacles such as areas of more resistant rock.
The water flows faster around the outside of the bends than it does round the inside of them, causing undercutting on the outside of the bends and deposition on the inside edges, or slip-off slopes. This eventually leads to the creation of spurs; ridges of land sloping down to the stream on either side of the valley.
Because the river meanders from side to side, the spurs form first on one side of the valley, then the other, so they alternate from bank to bank. This means that if you look along the valley the spurs seem to join together, or interlock. Hence they are called 'interlocking spurs'.
Photo of a section of ice sheet showing one of the few mountain tops that protrude above the ice |
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A satellite image from NASA showing the Antarctic ice sheet. |
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