essay 4 mechanical weathering

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mechanical weathering is the physical disintegration of rock brough about by the sun and frost.It causes the rock to crumble.It does not alter the chemical composition of rock

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Mechanical weathering occurs i n areas with little or no vegetation cover e.g deserts or areas of extreme climate.Mechanical weathering is prevalent in sedimentary rocks which posseses strata

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4 types of mechanical weathering are freeze thaw action ,exfoliation ,pressure release, salt crystilisation

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freeze thaw action is most prevalent in mountainous areas where tempature fluctuates above/below freezing point

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rain enters cracks in the rocks freezes and increases in volume by 10 percent the ice splits the rocks and melted ice goes further into cracks

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process continues until rock is completely broken down. Producing rock fragments called regolith which can be seen on the side of the mt

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freeze thaw action

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exfoliation is due to temp changes in cloudless regions e.g Sahara. Rock expands during day and contracts at night due to absence of cloud cover.

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expansion and contraction weakens rock eventually leading to destruction.If the rock breaks down into large rectangular pieces is called block disitegrstione.g Monument Valley Arizona

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Outer layer will expand more than inner layer cuasing it to peel off this is called exfoliation, common in the sahara

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Pressure release is associated with igneous rock such as granite.These rocks are formed beneath the earths surface

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they are subjected to huge pressure from the overlying ock e.g sandstone.When the overlying rock is eroded underlying rock is exposed

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pressure from overlying rock is removed the underlying rock is subjected to weathering which results i disentegration of rock occurs on the wicklow mts

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Salt crystilisation is associated with hot arid climates and salt solution e.g the mediteranean where evaporation rtaes are high.Water containing salt enters the rock

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Water evaporates leaving salt behind when salt is heated it expands causing it the rock to disintergrate