COASTS

• FREEZE THAW (MECHANICAL) - Places where night temperatures reach below freezing. Water finds its way into small cracks in a rock, when the temperature drops to 0 water freezes as water freezes it expands exerting immense pressure on the rock, these forces cause the cracks to get bigger. When the temperature rises again the water thaws, this cycle occurs many times and the rock will break away.
• WETTING AND DRYING -

  • in warmer climates where the water doesn’t freeze, a similar process called wetting and drying occurs which works in the same way, just without the ice
  • This often occurs in the inter-tidal zone; the area is exposed at low tide but covered at high tide
  • Rocks expand when they are wet and contract again when dry 
• SALT CRYSTALLISATION - water collects in the rock cracks when it rains, when the sun shines water evaporates leaving salt crystals behind, these will grow over time and cause the rock to break due to stress.
• EXFOLIATION -

  • This occurs in hot climates 
  • When rocks warm up during the day, the rock expands, exerting outward pressure
  • At night, the rocks cool and contract 
  • Over time, this contraction and expansion causes very thin pieces of the rock to flake off 
• BIOLOGICAL WEATHERING - As plants grow the roots enter the cracks in the rock under the soil, as the plants and roots grow the roots cause the crack to get larger and the rock breaks away, small burrowing animals like rabbits also cause this.
• CARBONATION - slightly acidic rain reacts with carbonate rocks like limestone causing them to dissolve.
• OXIDATION - Iron minerals in the rock react with oxygen in the air causing it to rust and breakdown the rock
• SOLUTION - Other salt minerals in the rock are dissolved
• • Soil Creep:
  • Common in humid climates with movement of less than 1cm per year 
  • Soil expands when it freezes, gets wet or is heated up in the sun
  • As the soil expands, it lifts at right angles to the slope
  • When the soil shrinks, it falls straight back down
  • Soil creep takes a long time because the soil moves only a millimetre to a few centimetres at a time
• • Flow:
  • Occurs on slopes between 5° and 15° with speeds between 1 to 15km per year
  • Usually happens after the soil has become saturated with a flow of water across the surface
  • Vegetation is flattened and carried away with the soil
• • Slide:
  • A movement of material 'en masse' which remains together until hitting the bottom of a slope
• • Fall:
  • Slopes are steep and movement is rapid
  • Caused by a number of reasons:
  • Extreme weathering: freeze-thaw action can loosen rocks that become unstable and collapse
  • Rainfall: too much rain will soften the surface leading to the collapse of the slope
  • Earthquakes can dislodge unstable rocks 
  • Hot weather can dry out soil causing it to shrink, allowing rocks to fall
• • Slump:
  • Usually found on weaker rock types (i.e. clay), that become saturated and heavy
  • This is common at the coast and is also known as rotational slip
  • It involves a large area of land moving down the slope in one piece
  • Because of the way it slumps, it leaves behind a curved indented surface
• CORRASION - Bits of rock and sediment transported by the waves smash and grind against rocks and cliffs breaking bits and smoothing surfaces.
• HYDRAULIC ACTION - air in cracks and cliffs is compressed when waves crash in, the pressure exerted by the compressed air breaks off rock pieces.
• CAVITATION - Waves recede, compressed air expands violently, exerting pressure on the rock and causing pieces to break off
• Wave quarrying - energy of a wave as it breaks against a cliff and it detaches bit of rock.
• SOLUTION - soluble rocks get readily dissolved by sea water
• Attrition - bits of rock in the water smash against each other and break into smaller bits
• SOLUTION (TRANSPORTATION) - substances that can dissolve are carried along in the water
• SUSPENSION - very fine material such as silt and clay particles is whipped up by turbulence and carried along in the water
• SALTATION - larger particles such as pebbles or gravel are too heavy to be carried in suspension instead the force of the water causes them to bounce along the sea bed.
• Traction - very large particles such as boulders are pushed along the sea bed by the force of water.
• RAISED BEACHES - Fall in sea level leaves beaches above the high tide mark, over time beach sediment becomes vegetated and develops into soil, flat and covered with pebbles
• MARINE PLATFORM - Exposure of wave cut platforms leaving them raised above their former level, these are no longer eroded by the sea and get slowly covered by vegetation (relict cliffs).
• RIAS - river valleys are partially submerged, they have a gentle long crossprofile, wide and deep at their mouth, becoming narrower and shallower further inland they reach.
• FJORDS - drowned glacial valleys, relatively straight and narrow with very steep sides they have a shallow mouth caused by a raised bit of ground which is formed by deposition, theyre very deep further inland e.g Sognefjorden.
• DALMATIAN COAST - Valley lies parallel to the coast, am increase in sea level can form a dalmatian coast, valleys are flooded leaving islands parallel to the coastline.
• SEA WALL - A wall that reflects the waves back out to sea, preventing erosion of the coast, also acts a barrier to prevent flooding
• REVENTMENT - Slanted structures built at the foot of cliffs, when waves break against them they absorb the wave energy and so prevent cliff erosion
• GABIONS - Rock filled cages located at the foot of the cliff, they absorb wave energy
• RIPRAP - Boulders pilled up along the coast, they absorb wave energy and reduce erosion.
• GROYNES - Fences built at right angles of the coast thye trap beach material transported by longshore drift, this creates wider beaches which slows the waves and gives greater protection from flooding and erosion
• BREAKWATERS - Concrete block or boulders deposited off the coast, they force waves to break offshore which reduces their erosive energy before they reach coast
• EARTH BANK - Mounds of earth act as a barrier to prevent flooding
• TIDAL BARRIER - Built across river estuaries they contain retractable floodgates that can be raised to prevent flooding from storm surges.
• TIDAL BARRAGE - Dams built across river estuaries they generate electricity and trap water behind them at high tide and water release is controlled through turbines in the dam and also prevent flooding from storm surges.
• BEACH NOURISHMENT - Sand and shingle added to beaches from elsewhere this creates wide beaches which reduce erosion of cliffs.
• BEACH STABILISATION - Done by reducing the slope of an angle and planting vegetation or by sticking stakes and old tree trunks in the beach to stabilise the sand
• DUNE REGENERATION - Sand dunes created or restored by either nourishment or stabilisation of the sand and absorbs wave energy by providing a barrier between sea and land.