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Coasts (Factors that affect wave energy (Fetch
Greater the fetch, the…
Coasts
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Coastal processes
Coastal erosion
Hydraulic action
Air may be trapped in joints and cracks
The trapped air is compressed repeatedly by oncoming waves.
This weakens the cliff and causes the rocks to break apart
Abrasion
Bits of rock and sand in the waves grind down cliff surfaces
They are hurled at cliffs and by the waves
This weakens the surface and breaks down the coasts
Attrition
Waves smash rocks and pebbles on the shore into each other
They break up and become smoother and rounder
Solution
Chemicals in the sea water can react and dissolve certain types if rocks
For example, Acid contained in the sea water dissolves some types of rocks like Chalk or limestone
Sediment transport
Beach drift
When the waves approach the beach at an angle, they break on the beach
Swash moves sediments up the beach at an angle
Backwash moves sediments perpendicularly down the beach
The zig-zag movements along the beach is called the beach drift
Longshore drift
When the waves approach the a coast at an angle, they produce longshore currents in the nearshore zone to transport sediments along the shore.
-Longshore currents are ocean currents flowing parallel to a coast
both the beach drift and the longshore current is called the longshore drif
Sediment deposition
involves adding materials to the coast
wave energy decreases, they are not able to carry sediments with them.
Large sediments are deposited first before the smaller sediments.
Sediments differ in shape and sizes, they produce a variety of beaches
Type of wave
Constructive wave
low energy and deposit materials on the coast
strong swash and weak backwash
Break gently over a long distance
Destructive wave
Break violently on the shore and have high energy
Common along steep sloping coasts
Weak swash and strong backwash
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Wave refraction
When wave approach the coastline from oceans, the water becomes shallower to cause the wave to start bending
The waves reach the headlines and converge due to refraction with greater amount of energy. They increase in height and have a greater erosion power as wave energy is concentrated. This causes more erosion at the headlands
The waves bend into the bays and diverge due to refraction with lesser amount of energy. They decrease in height and have a lower erosion power as wave energy is diffused. This allows more deposition to occur in bays
The process which the wave changes the direction when they approach a coast