WAVES
- Ocean waves contain energy- sometimes a great deal of energy. Created by ocean winds, they carry energy vast distances across the Pacific Ocean. Acting like drills or buzz saws, the waves erode the solid rock of the coast into cliffs and caves. Waves also carry sediment that forms features such as beaches.
- HOW WAVES FORM: The energy in waves come from wind that blows across the water's surface. As the wind makes contact with the water, some of its energy transfers to the water. Large ocean waves are the result of powerful storms far out at sea. But ordinary breezes can produce waves in lakes or small ponds.
- The energy that water picks up from the wind causes water particles to move up and down as the wave goes by. But the water particles themselves don't move forward.
- A wave changes as it approaches land. In deep water, a wave only affects the water near the surface. But as it approaches shallow water, the wave begins to drag on the bottom. The friction between the wave and the bottom causes the wave to slow down. Now the water actually does move forward with the wave. This forward-moving water provides the force that shapes the land along the shoreline.
- EROSION BY WAVES: Waves are the major force of erosion along coasts. Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment.
- HOW WAVES ERODE AWAY: One way waves erode the land is by impact. Large wave scan hit rocks along the shore with great force. This energy in waves can break apart rocks. Over time, waves can make small cracks larger. Eventually, the waves cause pieces of rock to break off.
- Waves also erode by abrasion. As a wave approaches shallow water, it picks up sediment, including, sand and gravel. This sediment is carried forward by the wave. When the wave hits the rock its like sandpaper wearing away wood.
- Waves coming to shore gradually change direction. The change in direction occurs in different parts of a wave begin to drag on the bottom. The energy of these waves is concentrated on headlands. A headland is a part of the shore that sticks out into the ocean. Headlands stand out from the coast because they are made of harder rocks that resists erosion by waves. But , over time, waves erode the headlands and even out the shoreline.
- LANDFORMS CREATED BY WAVE EROSION:Eventually, waves may erode the base of a cliff so much that the rock above collapses. the result is a wave-cut cliff. Another feature created by wave is a sea arch. A sea arch is an arch that forms when waves erode a layer of softer rock that underlies a layer of harder rock. If an arch collapses, the result may be a sea stack, a pillar of rock rising above water.
- DEPOSITS BY WAVES: Waves shape a coast when they deposit sediment, forming coastal features such as beaches, spits, and barrier beaches. Deposition occurs when waves slow down, causing the water to drop its sediment.
- BEACHES: A beach is an area of wave-washed sediment along a coast. The sediment deposited on beaches is usually sand.
- As waves repeatedly hit the beach, some of the beach sediment moves down the beach with the current, in this process called longshore drift.
- SPITS: One result of longshore drift is the formation of spit. A spit is a beach that projects like a finger into the water. Spits form as a result of deposition by longshore drift. Spits occur where a headland or other obstacle interrupts longshore drift, or where the coast turns abruptly.