landforms characterized by relatively steep, mountainous sides and flat floors. The steep sides are created by displacement on faults such that the valley floor moves down relative to the surrounding margins, or, conversely, the margins move up relative to the floor. Differences in the elevations of valley floors and surrounding mountains or plateaus range from only several hundred metres to more than 2,000 metres in major rift valleys. The widths of tectonic valleys and basins vary from as little as 10 kilometres to more than 100 kilometres. Their lengths typically are hundreds of kilometres, but range from a few tens to thousands of kilometres.
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