rift valley
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The subsidence of rock resulting from two or more parallel rocks moving apart is known as a graben. When this happens on a large scale, with tectonic plates moving apart, a rift valley is created.
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A river runs through a steep-sided rift valley at Thingvellir, in Iceland. In this area, the North American plate is pulling away from the European plate at an annual rate of 2 cm/0.8 in. It is part of the Mid-Atlantic Ridge, a constructive plate boundary where new material is formed by the cooling of lava.
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A steep rift-valley wall at Thingvellir, Iceland. Rift valleys are created when tectonic plates pull apart, and part of the Earth's crust subsides. The Mid-Atlantic Ridge can be seen in action here at Thingvellir, where the North American plate is pulling away from the European plate.
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A river runs through a steep-sided rift valley. This valley was formed as a result of the movement of tectonic plates on the Mid-Atlantic Ridge at Thingvellir, Iceland.
Valley formed by the subsidence of a block of the Earth's crust between two or more parallel faults. Rift valleys are steep-sided and form where the crust is being pulled apart, as at mid-ocean ridges, or in the Great Rift Valley of East Africa. In cross-section they can appear like a widened gorge with steep sides and a wide floor.
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