The Formation Of Granite Tors

The formation of granite tors for gcse geography 9 1.

The formation of granite tors.

Over time the material above the batholith was weathered and removed by rivers and glaciers. The formation of a granite tor. Tors are mostly less than 5 meters 16 ft high. The formation of tors on dartmoor.

Tors are seldom more than 15 metres 50 feet high and often occur as residues at the summits of inselbergs and at the highest points of pediments. Granite is an intrusive igneous rock which means it was formed in place during the cooling of molten rock. Alternate contraction and expansion of the rock cause the joints or cracks present in the rock to be widen. Granite tors start to form when magma that has intruded into the crust cools to form a batholith.

Tors are landforms created by the erosion and weathering of rock. Generally the slower the molten rock cooled the larger it s mineral crystals with k feldspar megacrysts forming in special circumstances greater than 5cm. At night due to radiate cooling effect the rocks are cooled rapidly and they contract. The granite seen on dartmoor originated as a granite batholith under the surface of the earth.

One clear consequence of frost action on the granite has been the formation of rock basins locality1a not only on the upper surfaces of the tor core stones but also on occasions on larger clitter blocks clearly indicating that basin formation must have occurred recently. There is often evidence of spheroidal weathering of the squared joint blocks. During daytime rocks are expose to the baking sun they expand due to the increase in temperature. Tors usually overlie unaltered bedrock and are thought to be formed either by freeze thaw weathering or by groundwater weathering before exposure.

Many hypotheses have been proposed to explain their origin and this remains a topic of discussion among geologists and geomorphologists and physical geographers. The softer rock above the batholith erodes away over time leaving the batholith exposed to the elements. Most commonly granites but also schists dacites dolerites ignimbrites coarse sandstones and others.