Ice on the land summary.

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  • ICE ON THE LAND
    • Amount of Ice
      • The last ice age was in the Pleistocene period. around 18,000 years ago. Could have been up to 20 cold periods.
        • Ice spread over Britain as far south as Severn estuary and up to the eastern coast.
        • In the rest of the world, Canada, Scandinavia, Greenland and parts of Russia were covered in ice.
    • Glaciers
      • A glacier is a very slow moving mass of ice through a valley.
        • Accumulation: snow advances when more snow collects than melts.
        • Ablation: snow retreats when more snow melts than is collected.
      • Glaciers erode in 2 ways: plucking and abrasion.
        • Plucking is when ice freezes on a rock, so when the ice moves the rock moves with it.
        • Abrasion is when rocks and pebbles stuck in the ice grind over the valley floor and sides. Scratches the surface causing striations.
      • The glacier moves in different ways.
        • Freeze-thaw weathering is when water gets into the cracks in the rocks. The freezing and expanding causes it to break off.
        • In summer the ice melts more, which lubricates the glacier and allows it to slide downhill. This is called basal slip
        • In hollows where the movement is curved as the glacier moves downhill, this is called rotational slip.
        • Bulldozing is when the ice pushes material forward as the ice advances.
    • Moraine
      • Lateral moraine is carried by the side of the glacier.
      • Medial moraine is when two glaciers join so that lateral becomes medial in the middle.
        • Lateral moraine is carried by the side of the glacier.
      • Terminal moraine marks the furthest point the glacier has been.
      • Recessional is when the glacial deposits material behind, marking the retreat.
      • Ground moraine is moraine under the ice.
      • Englacial moraine is moraine trapped inside the glacier; eg. if  it falls into a cravats and new snow falls on top.
    • Features
      • A corrie is an arm-chair shaped hollow in the side of a mountain. Made mainly due to rotational slip
        • Tarn is the lake in the corrie when ice melts.
        • A pyramidal peak is when three corries back on to each other to form a pyramid-like point.
      • A glacial trough (U-shaped valley) has a flat valley floor and steep sides. This is from when the glacier forces it's  way through the valley. Leaves truncated spurs.
        • Truncated spurs are when the spurs are cut of the ice. Therefore, the valley floor may contain deposited material.

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