The Formation Of Granite Tors

Granite is an intrusive igneous rock which means it was formed in place during the cooling of molten rock.

The formation of granite tors.

Most commonly granites but also schists dacites dolerites ignimbrites coarse sandstones and others. While the rock is cooling it starts to contract causing cracks these also occur when the batholith is exposed and pressure is released. Granite tors start to form when magma that has intruded into the crust cools to form a batholith. The formation of granite tors for gcse geography 9 1.

The granite seen on dartmoor originated as a granite batholith under the surface of the earth. 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. At night due to radiate cooling effect the rocks are cooled rapidly and they contract. A batholith is an area of molten rock that has cooled very slowly within the crust creating a rock with large crystals.

The formation of a granite tor. The processes resulting in the formation of the dartmoor tors started about 280 million years ago as the granite forming dartmoor cooled and solidified from molten rock at a. Alternate contraction and expansion of the rock cause the joints or cracks present in the rock to be widen. Many hypotheses have been proposed to explain their origin and this remains a topic of discussion among geologists and geomorphologists and physical geographers.

Tors are mostly less than 5 meters 16 ft high. Generally the slower the molten rock cooled the larger it s mineral crystals with k feldspar megacrysts forming in special circumstances greater than 5cm. The formation of tors on dartmoor. The softer rock above the batholith erodes away over time leaving the batholith exposed to the elements.

Tors usually overlie unaltered bedrock and are thought to be formed either by freeze thaw weathering or by groundwater weathering before exposure. There is often evidence of spheroidal weathering of the squared joint blocks. Over time the material above the batholith was weathered and removed by rivers and glaciers.