Rocks revision


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Rocks revision

  1. 1. Rocks & Landscapes By Mark Kendall
  2. 2. Igneous Rock Granite Dartmoor, Devon
  3. 3. Dartmoor, Devon, UK Latitude: 50.38N Longitude: 03.57W Rainfall: 1000mm+ PA. Avg. Night Time Temperature: 0ºC Igneous rocks are fire formed rocks. This is when magma from the Earths mantle cools and solidifies. Granite is an intrusive igneous rock, meaning that the magma has cooled within the Earths surface. Igneous rocks can also be extrusive, this is where the lava cools and solidifies on the surface. In Dartmoor the overlying rocks and soils have been weathered and eroded away over millions of years, leaving a granite surface. Igneous Rock Granite Dartmoor, Devon
  4. 4. The Cheesewring, Bodmin Moor Landscape and Surface Features The main surface feature of a granite landscape is a tor . These are often between 5 and 10m in height and are surrounded by weathered material. The main type of weathering that affects granite is freeze-thaw weathering, due to the low night time temperature. The landscape is often boggy/marshy due to poor drainage and there are often rugged uplands. Igneous Rock Granite Dartmoor, Devon
  5. 5. <ul><li>Granite Landscape Features </li></ul><ul><li>Tourism- Walking, Hiking, Viewing Tors, Pony Trekking etc. </li></ul><ul><li>Agriculture- Sheep grazing (not suitable for any other type of farming due to poor land and wet/cold climate) </li></ul><ul><li>Dartmoor Prison- Remote and Away from People, historically hard to escape from. </li></ul><ul><li>Uses of Granite </li></ul><ul><li>Kerb/Facing Stones </li></ul><ul><li>Decorative Building Pillars </li></ul><ul><li>Medicine (Kaoline) </li></ul><ul><li>Fireplaces, Flooring, Kitchen Work Surfaces </li></ul>Igneous Rock Granite Dartmoor, Devon Dartmoor Prison
  6. 6. Sedimentary Rock Limestone Malham, Yorkshire Dales
  7. 7. Malham, Yorkshire Dales, UK Sedimentary rocks are rocks made up from layers of sediments that have been compressed over thousands or years. Limestone is formed from the remains of sea creatures. Limestone is pervious meaning that water travels down the joints and along the bedding planes, but not through the rock itself. Rain water contains CO 2 which creates a weak carbonic acid. This reacts with the limestone and dissolves it creating a calcium carbonate solution. The formula for the limestone solution is: CaCO 3 + H 2 CO 3  Ca(HCO 3 ) 2 The limestone is then carried away as the calcium carbonate solution. This chemical weathering creates a distinctive scenery. Sedimentary Rock Limestone Malham, Yorkshire Dales
  8. 8. Landscape and Surface Features Limestone Pavement- consists of clints, the rectangular blocks which sit in between the grykes , the widened joints in the limestone. Swallow/Sink Holes- where the stream goes from impermeable rock to pervious limestone and the water disappears underground. Resurgence- where the underground stream meets the underlying permeable rock and reappears. Sedimentary Rock Limestone Malham, Yorkshire Dales
  9. 9. Underground Limestone Features Caverns- the limestone solution and chemical weathering forms underground caverns. Stalactites ↓ - where the water from the solution evaporates leaving a calcite deposit. This builds up over time forming a cone hanging from the ceiling. Stalagmites ↑ - where the water from drips from the ceiling, the water evaporates and leaves a calcite deposit. This builds up over time forming a cone rising from the floor. Column- where a stalactite and a stalagmite meet. Sedimentary Rock Limestone Malham, Yorkshire Dales
  10. 10. Chalk is a soft limestone that is porous. That means it contains millions of tiny holes that absorb water like a sponge. Due to this chalk is an aquifer as it stores water. The water can be pumped up and distributed to home is the S.East of England. Chalk is more resistant than clay so is more resistant to weathering and erosion. This means that the clay gets eroded away quicker than the chalk and escarpments are formed with dip (gentle) slopes and scarp (steep) slopes. There is a lack of surface water in chalk areas and settlements therefore tend to gather around springs. Springs can occur at the foot of scarp slopes where the chalk rests on an impermeable rock like clay (eg. South Downs) or on dip slopes where the water table reaches the surface. Sedimentary Rock Chalk South Downs Escarpment
  11. 11. Metamorphic Rock Marble Metamorphic rocks are formed when extreme heat and pressure acts on either sedimentary or igneous rocks altering their structure. For example, Limestone  Marble Pressure from Surface Pressure Heat Heat Metamorphic Rocks forming here