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Coastal Processes Presentation
Transcript of Coastal Processes Presentation
As waves enter shallow water the energy in the waves begins to interact with the sea floor thus decreasing its speed, shortens its wave length and increases its height. Eventually the wave peak travels faster than the base of the wave, causing it to break and release the contained energy. The broken wave forms the surf and swash zone. Waves Characteristics of Waves at Erosional Coasts Processes Formations Waves are formed by the action of waves blowing across the ocean. They first form ripples which form wavelets which then form waves. In the open ocean a swell forms. As waves travel towards the coast they take the natural wind energy with them. The wave speed and size are influenced by the strength of the wind and the length of the fetch. Fetch is the distance the wind travels over the ocean to form the wave. YouTube Video:
What is coastal erosion? Corrasion (abrasion) Wave-Cut Platform Typical Landforms
at Erosional Coasts Attrition Hydraulic Action Corrosion The act of waves crashing on rocks, which moves rocks and other material.
This breaks it the material into small pieces, which makes contact with the rock shelf, eroding it. The action of salt on minerals like iron (contained in rock), which weakens the rock and makes it susceptible to erosion. This diagram shows the chemical process.
The solution is water and air, and the metal is rock.
M is salt acting on ne, the mineral (e.g. iron) A form of erosion when rocks and other particles that are being transported by the current make impact with the bed and bed grains, causing break up of rocks.
This break up makes the rocks smoother and rounder. Here, the rocks are being flung against the rock by waves, causing abrasion. Here, attrition has caused the bed to become uneven. When waves enter cracks in rocks, which leads to air being compressed by the force of the water. This causes erosion and may cause blowholes. Parts of a wave Water has enter a crack in this rock, causing erosion and expansion of the crack Corrosion from waves on cliff causes undercutting, which eventually collapses to form a platform Headland As is indicated in the diagram and video, the key landforms seen at erosional coasts include:
Seastacks. Erosion Erosion from waves causes soft rocks to be broken up much faster than hard rocks, causing headlands and bays to form, over thousands of years Backwash - The motion of receding waves
Swash - rush of water up the beach after breaking of a wave Depositional Coasts Stack and Arch An arch occurs when two caves on a headland, formed by erosion, break through making a tunnel. When the pressure from above is too great, this collapses, forming a stack of rock on the side not attached to land. Coastal Erosion has a major impact on Depositional Coasts, as moving tides and coastal processes such as the Pacific Ocean currents. Diagrams above show how Sediment is pushed up/down coasts and river mouths through longshore drift to cause Sand Spits, Barrier Islands, Tombolos, Berms and Runnels. Blowhole and Cave Sea caves formed by erosion gradually grow upwards as the waves hit the rock. Once they erode to the surface, the water is blasted into the air. There are three main types of waves. They are:
- Spilling waves
These waves break far from the shoreline. They are characterised by white foam rolling over the front of the wave and up the gentle beaches onto which they break. Consequently, they are ideal waves for body surfing.
- Plunging waves
These waves break on moderately sloped beaches. They consist of the tubes which are popular amongst surfers.
- Surging waves
Surging waves occur on steep beaches. They are the main cause of erosion and roll up the beach instead of breaking onto it. Deconstructive waves Breakdown rock, remove sand
Create steep beaches Formations Beach Constructive waves Sand is formed by the abrasion of rocks by waves, and this is deposited, again by waves, onto the shore, forming beaches. Long-shore drift transports the sand and pebble along the shore. Deposit eroded material
Low energy and add to the beach Strong seasonal wind causes the waves to often hit the coast at oblique angles. This causes the waves to run up sand formations at slight angles, yet retract normally perpendicular to the beach due to gravity, this is a slight push that causes longshore drift. Aeolian Transport Spit Material is moved along the coastline by long-shore drift. The material is deposited to form a spit Tombolo A tombolo is essentially a spit that is formed between two landmasses, forming a bridge. Coastal Lagoon Formed when long-shore drift moves sediment across a coast, blocking patches of water if the coastline is concave. Coastal Sand Dune Sand dunes are formed when wind blows sand up on mound where it grows. The sand beyond this mound slips down, forming the distinct shape. Waves make the dune more distinguishable. Thank-you for Watching The End!