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Geography
Geography - Coasts
Term | Definition |
---|---|
Coast | where the land meets the sea |
Waves are formed by | the wind blowing over the sea |
Fetch | the distance the wind blows across the sea |
Constructive waves | low waves that carry & deposit large amounts of materia |
Destructive waves | high waves that have a powerful backwash which removes material from the beach |
Weathering | the breakdown of rocks in their original place |
Mechanical weathering | break up of rocks & piles of rock fragments found at the bottom of the cliff |
Chemical weathering | rainwater (which is slightly acidic), very slowly dissolves certain types of rocks & minerals |
Freeze-thaw weathering | mechanical - water collects in cracks in the rocks, freezes & expands which makes the cracks bigger |
Salt weathering | mechanical - the salt in seawater leaves salt crystals in the cracks in the rocks which grow and cracks the rocks |
Carbonation weathering | chemical - rainwater absorbs CO2 from the air & becomes slightly acidic and has a chemical reaction with alkaline rocks causing the rocks to slowly dissolve |
Mass movement | the downward movement of material due to gravity |
Sliding | large rocks slide down the cliff as a landslide, often caused by heavy rainfall or earthquakes |
Slumping (or Slipping) | saturated or weak rock (e.g. clay) collapse |
Rock fall | fragments of rock break away from the cliff because of freeze-thaw weathering |
Scree | fragments of rock that fall to the bottom of the cliff |
Erosion | waves or rivers gradually wear away the rocks / cliffs / river banks |
Solution | the acids in the water slowly dissolve the rocks |
Attrition | rocks & material in the sea knock into each other making them smaller |
Abrasion | the waves throw sand & pebbles against the cliff face which erodes it |
Hydraulic Action/Power | water enters cracks in the cliff, air compresses, causing the crack to expand |
Transportation | a natural process by which eroded material is transported |
Traction | large pebbles dragged along the seabed by the force of the water |
Saltation | pebbles that bounce along the sea/river bed. |
Suspension | Particles carried within the water. Can make the water look dirty and ‘murky.’ |
Solution | Minerals dissolve in water and are carried along |
Longshore drift | the transport of sediment along a stretch of coastline |
What causes longshore drift? | waves approaching the beach at an angle |
Deposition | material carried by the waves/river are dropped and build up over time |