coastal 2

  • Created by: parker123
  • Created on: 28-12-17 18:24
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  • coastal erosion
    • beaches
      • formation of beaches
        • sandy beaches
          • 1--in sheltered bays, low energy constructive waves transport material onto the shore.
          • 3--when tide has gone out there is more material on beach than before
        • pebble beach
          • 1-- exposed beaches sometimes have large fetch.
          • 2--the plunging nature of destructive waves along with backwash means pebbles aren't moved far up beach, making beach profile steep
          • 3--a storm beach may form when wild, stormy weather and waves hit boulders and large pebbles to the back of beach.
        • a beach is a landform of coastal deposition that lies between the high & low tide levels, most beaches formed of sand & shingle or pebbles as fellas mud &  silt.
        • a beach that forms in a bay is crescent-shape, but shape is distorted by longshore drift so the beach is narrower updraft than downdrift
      • characteristics
        • sandy beach
          • gradient generally shallow, almost flat
          • waves mostly constructive
          • back of beach are sometimes sand dunes & beach stretches inland a long way
          • at low tide wet sand may have rippled appearance
        • pebble beaches
          • gradient is generally steep
          • waves are normally destructive
          • back of beach, (storm beach) large pebbles & beach stretches inlands not far.
    • sand dunes
      • formation of sand dunes
        • 1--are large leaps f sand that form on the dry backshore of a sandy beach
        • 2-- they need large flat beach, large supply of sand, onshore winds to move sand to the back of the beach & obstacles scubas driftwood to form against
        • 3-- sand continues t more up the windslope
        • 4--heights builds up until the structure becomes unstable
        • 5-- sand then slips down the leeward slope
      • characteristics of sand dunes
        • gentle slope on windward side
        • crests height vary up to approx 15m
        • unstable steep slip slope (30-34') on sheltered leeward slope
    • spits
      • formation of spits
        • 1--a sipit is a a sand & shingle beach that sis joined to the land but projects downdrift into the sea. spits form where coastline suddenly changes or at mouth of estuary.
        • 2-- where a coastline changes shape the waves begin to lose energy so there is proxominal end & the spit begins to grow out to sea
        • 3-- prevailing wind makes the swash at an angle to the shore. backwash is at right angle because of gravity. longshore drift therefore moves material in a zig-zag manner to beach
        • 4-- shingle or pebble spit the pebbles become smaller  more rounded towards the distal end due to attrition. they becomes smaller as longshore drift becomes weaker.
        • 5-- a dominant wind causes the distal end to hook towards the land& olde recurve (hook) marks a former env of spit.
      • characteristics of spit
        • proximal end (large pebbles)
        • hooked distal end (small pebbles)
        • mudflats, salt marshes & lagoon & recurves
    • bars
      • formation of bars
        • a bay bar (barrier beach bar)
          • is a ridge of sand or shingle that stretches from one side of bay to other forming a lagoon behind it
          • beach barrier formation is due to longshore drift transporting sediment from one side of bay to other
        • submerged bay
          • form in shallow waters where there is a lot of sediment on a beach, formed by transport of sediment off then back onto beach.
        • offshore bars
          • bar raised area of a seabed that lies a little offshore, in stormy weather destructive waves drag the beach material out to sea to form an offshore bar.
      • characteristics of bars
        • bay bar
          • at least some part of the barrier beach bar is visible at all times
        • submerged bars
          • often completely detached from land, can be serval metres long
        • offshore bars
          • completely detached from shore, it has salt marshes, sand dunes and mudflat

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