Geography-Lithosphere-Coastal processes

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Geography-Lithosphere-Coastal processes
2011-04-05 12:36:37
Geography Lithosphere Coastal processes

Geography-Lithosphere-Coastal processes
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  1. Explain the formation of bays and headlands
    • Bays and headlands are found on discordant coastlines where there are alternating bands of hard rock (chalk) and soft rock (clay)
    • destructive waves erode the softer rocks more rapidly, forming bays
    • the harder rock is eroded more slowly forming jutting out headlands
    • this is known as differential erosion
    • headlands are exposed to erosion on three sides and form a point
    • headlands protect the bays, so deposition of sand occurs in the bays
  2. Explain the features of eroded headland
    Many features form on headlands these include, caves, arches, stacks and stumps

    • a cave is formed when hydraulic action widens the weakness in a rock. it is also eroded by abrasion and pounding
    • Arches are formed when waves cut through the cave by hydraulic action and abrasion. the arch is continually widened at its base. eventually the roof of an arch becomes too heavy to be supported and collapses leaving a stack(isolated portion of cliff)
    • the stack is then undercut and collapses leaving a stump
  3. explain the formation of a spit
    • A spit is a long narrow accumulation of sand or shingle, with one end attached to the land and the other end extending out into either a river estuary or the sea itself-eg Hurst Spit
    • It is formed by longshore drift and deposition
    • The sediment is moved along a coast by longshore drift in the direction of the prevailing wind.
    • when the sediment reaches a bay the velocity of the water decreases causing it to deposit the sediment.
    • The sediment continues to build up making the spit longer.
    • Occasionaly the wind direction changes. This alters the direction of the wave.
    • This makes sediment be deposited the other way causing a curve at the end of the spit.
    • spits are unable to grow as there is a river current that send the material out to sea.
    • Behind the spit a salt marsh is found where the water is protected