The energy in a wave comes from the wind that blows across the waters surface. As the wind touches the water it transfers its energy. The energy that the water picks up makes the water particles move up and down, but they don't move forward.
A wave changes as it moves closer to land. In deep water only the surface is affected by a wave, but once they get to more shallow water, the waves start to drag on the bottom. Now that the wave has friction, the wave starts to slow down. Not until now do the water particles actually move, and can shape a shoreline.
Erosion By Waves
Waves are the major cause of erosion along the coast. Waves shape the coast through erosion by breaking down rock and moving sand and other sediment.
How Waves Erode
One way waves erode the land is by impact. Large waves hit rocks with lots of force. The energy in waves can break apart rocks. Over time waves make small cracks bigger. Eventually the wave causes the rock to chip off. Waves can also erode rock by abrasion. As a wave comes to shallow water it picks up sediment. Once the wave crashes against land the sediment wears the rock down.
As a wave approaches land it usually changes direction due to the way the wave drags on the bottom. When these waves change direction they can create a headland. A headland is a part of the shore that sticks out into the ocean. The headland sticks out from the shoreline because it is made from harder rock than the rest of the coast, making the shore erode before the headland.
This is a Headland
Landforms Created By Wave Erosion
The softer rock along the coastline erodes first. Sometimes waves can erode a hollow area called a sea cave. Over time waves can also erode the base of a cliff so much that it makes the rock above it collapse, creating a wave cut cliff. Another landform that is created by waves is called a sea arch. A sea arch forms when waves erode a layer of soft rock that is underneath a layer of hard rock. If a sea arch collapses it creates a seastack, which is a large stack of rock in the middle of the water.
This is a Seacave
Deposits By Waves
Waves shape a coast when they deposit sediment, which can form beaches, spits and barrier beaches. Deposition occurs when the waves slow down, causing the water to drop the sediment. This process is similar to the deposition that occurs in a river.
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