Coasts

When you sit on a beach, you can watch the waves crashing against the shore. After each wave, the water runs quickly back down the slope. The swirling water is seldom clear, because it is carrying and moving fine grains of sand. The sea also moves pebbles. If you stand in the sea, you can often feel the pebbles move under your feet. In bad storms, huge waves can shift great boulders. The sea hurls large rocks and pebbles at cliffs, battering them and dislodging big chunks of rock, which crash into the sea.
Beaches and coasts are always changing. Coastal erosion occurs when the sea is wearing away the land. Coastal deposition occurs when the sea piles up or deposits sand and pebbles to form new land.
In some places, where the rocks are hard, coastal erosion may be very slow. But in
Holderness, in Yorkshire, England, the sea is eroding the coast at an average rate of six or seven feet each year. Since Roman times, a strip of land about 2% miles wide has been eroded by the sea. Waves often erode caves in cliff faces. Sometimes the sea cuts caves into both sides of a headland and the caves meet to form a natural arch. If the arch collapses, a tall pillar of rock, called a stack, stands isolated from the coast. Some of the material worn from cliffs is swept out to sea. Some is moved along the coast and deposited to form new beaches and land areas. Sand, gravel and pebbles are sometimes piled up offshore to form long, narrow ridges called spits.
Coasts are also affected by rises and falls in the levels of the land and sea. If the sea level falls, then rocky areas once under the sea are permanently exposed. Coasts of this type are called coasts of emergence. If the sea-level rises, the sea floods coastal areas. Such coasts are called coasts of submergence. The fjords of Scandinavia were valleys once occupied by great glaciers. After the ice is melted, the sea level rose, flooding the valleys and forming deep, long and narrow sea inlets.

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