| Escarpments |
| An escarpment is an inland cliff. Escarpments
are steep slopes, often vertical, which border plateaux or uplands. Escarpments
or 'scarps' as they are also known can be formed by faulting, as blocks
of the Earth's crust are tilted or shear or simply by erosion as rivers
cut though soft layers of rock to form a valley with walls like Arizona's
Grand Canyon.
Escarpments are the steep slopes of buttes and mesas too. These are formed where a hard layer of rock like basalt, a fine grained volcanic rock, overlies a soft layer. Where the basalt occurs- perhaps in a wide strip emplaced by a flow of lava- the soft rock is protected, but where basalt is absent, erosion by wind and water can wear down the rock leaving a steep sided plateau.
Escarpments can be local or regional features, like the buttes and mesas of the American Midwest, or continental in scale like Africa's Great Escarpment. The Great Escarpment forms the southern border of South Africa's large interior upland, at the base of which lies a narrow strip of coastline. It extends southeast from Namibia and Angola through South Africa, along the northern edge of the Groot Karoo Plateau and runs northeast along the Lesotho border through the Drakensberg mountains and into Zimbabwe. In the Drakensberg mountains The Great Escarpment is a result of hard volcanic rock overlying soft sandstones, elsewhere the scarp is formed by the rapid downcutting action of rivers' headwaters. |
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