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Constructive and Destructive Waves. Beach Formation and Profile. By Naomi Markham
Wave Formation Waves are created by the wind. Friction is created by between the sea and the air, this pushes the water in the direction of the wind. This effect creates waves. Waves do not stop until they reach on obstacle or the wind stops.
There are two main factors that affect the size and strength of the wave:
The strength of the wind
The distance the wind has travelled.
Destructive Wave There are two main types of waves: Destructive and Constructive. Destructive waves are created when the wind is strong and has travelled a long distance. There are many during and after a storm. These waves are tall in proportion to their length. On average 11-15 waves break a minute. The waves have a weak swash meaning that they push a small amount of material onto the beach. However, they have a strong backwash. This means that the waves generally erode away the coastline. These waves create steep sloping beaches as the waves carry the material away from the beach.
Constructive Wave Constructive waves are created when the wind is weak and has travelled a short distance. These waves are low in proportion to their length. On average there are less than 15 a minute. Common in the summer time. The waves have a strong swash meaning that they push a lot of material onto the beach. However, they have a weak backwash. This means that the waves generally build up the coastline. These waves create gently sloping beaches as the waves push the material onto the beach.
Waves KEY WORDS! Fetch – The distance a wave has travelled. Swash – movement of water up the beach. Backwash – movement of water down the beach.
Beach Formation Material from cliff erosion and rivers is transported along the coastline by longshore drift and deposited by constructive waves to create a beach.
Longshore drift is when waves approach the beach at an angle that depends on the direction of the prevailing wind.
The swash picks up sand and shingle and travels up the beach in the same direction as the wave.
Due to gravity, the backwash and any material comes straight down the beach.
The material is transported in a zigzag movement along the beach.
Beach Profile The size and shape of material on a beach changes from the base of the cliffs to the sea. At the base of the cliff the material is generally large, jagged boulders which have been deposited at a time of a storm. As you move closer to the shoreline, the size of the material gets smaller and rounder. So after the boulders there might be pebbles then small stones. On the shoreline the material is very small and round and is generally sand.