Rocks, resources and scenery

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  • geological timescale- the period of geological time since life came abundant millions of years ago, divided into eras and periods
  • the periods are smaller than eras
  • igneous rock- formed by the cooling of magma(extrusion or intrusion) forms small and large crystals e.g.granite
  • sedimentary rock- formed by accumulation of sediment on sea floor under immense pressure and heat e.g. sandstone
  • metamorphic rock- rocks that have undergone change in their chemistry due to heat or pressure formed by previous sedimentary or igneous rock e.g. slate
  • GRANITE-formed 280 mill years ago
  • CARBONIFEROUS LIMESTONE- formed 340mill years ago
  • CHALK- formed during cretaceous period
  • CLAY- formed during cretaceous and jurassic period
  • rock cycle- 1) igneous rock broken down by weathering and transported to sea as sediment 2)deposition of sediment on sea bed forms layers and creates sedimentary rock by pressure 3) the sedimentary rock is put under extreme heat forming metamorphic rock 4)metamorphic rock is melted to form magma and crystalised either extrusively of intrusivley to form igneous rock
  • Weathering- disintergration or decay of rock in their original place at or close to the ground surface
  • BIOLOGICAL- caused by living organisms such as tree roots creating cracks in rocks and animals burrowing into soft rocks 
  • CHEMICAL- involves a chemical change taking place for example acid rain weathering away to create a limestone pavement
  • MECHANICAL- does not involve chemical change only physical break up of rocks for example freeze thaw weathering
  • freeze thaw weathering occurs when the water finds its way into cracks or joints, at night temperatures drop so the water freezes and expands: windening the crack. During the day the water melts and at night the process is repeated again until  rock fragment breaks off and collects at the foot of the rock face as scree (MECHANICAL)
  • exfoliation occurs mostly in places like the dessert when temperatures fluctuate because the skin of the rock expands during the hot temperatures in the day and then it contracts during the cold temperatures at night- this repeated process can lead too the skin peeling away from the rock. The presence of water is involved to weaken it and make it more vulnerable to flaking. (MECHANICAL)
  • Solution is the dissolving of rocks or minerals


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