Coasts

Coasts

1. Formation of a wave cut notch: The sea erodes a small hole in the bottom of the rock. The remaining rock weakens and falls off. The rock breaks down and a new wave cut notch is formed. The rocks are carried away by the sea and the process begins again.

   • Caves form in the side of the headland due to hydraulic action. Cave erodes backwards to form an arch. The top of the arch collapses to leave a stack and the stack is eroded to become a stump.
   • The waves carry the eroded material away, some carried to sea, but a lot along coastline. In this way hundreds of pebbles and sand get moved along the coastline every year. This is longshore drift. This is transportation.
     • Waves carry material on and off the land. If they carry more on than off a beach forms. Beaches form in sheltered areas. Low flat waves carry material up the beach and leave it there. Some beaches are made of sand and some are shingle (small pebbles).

2. Three jobs that waves do to shape the coastline: They erode the coast. Transport the eroded material away. Deposit material on and off the land.

   • In erosion: water is forced into cracks of rock to break it up. This is hydraulic action.
     • Dissolving soluble material from rock is solution.
       • Rocks form circular pebbles as the corners are worn off is attrition.
         • In abrasion sand and pebbles are flinged against rocks and worn away like sand paper.
   • Rain soaks into cliffs in severe erosion and weakens them. This is one form of weathering. Meanwhile the sea erodes the cliffs from below. Wooden barriers or revetments were meant to slow down erosion.
   • Groynes slow down erosion. They stop sand being carried away and the sand absorbs some of the waves energy, but they can't prevent it. Big rocks called rock amrmour protct cliffs.

3. Waves are caused by the wind dragging on the surface of the water. The length of water the wind blows over is called its fetch.

   • When waves roll to the sand is called the swash, and rolling back into the sea is the backwash.
     • If the backwash has more energy than the swash the waves drag the pebbles and sand away. This happens with high steep waves.
       • If the swash has more energy than the backwash the material is carried on to land and left there, which is what occurs with low flat waves.
         • The drop in sea level from high to low tide is called the tidal range. It keeps changing because the pull on the sea keeps changing as the moon moves around the earth and the earth around the sun.