The sea as a sculptor

The power of the sea

The power contained in a breaking wave is immense. A wave may strike the shore with a force equal to the pressure of six thousand pounds per square foot. These waves can hollow out or pull down rock cliffs. In some parts of the British Isles they are eating away the coast at the rate of 15 feet a year.
  Storm waves tend to tear down the shores. Gentle waves are the builders, for they may leave numberless grains of sand against offshore bars to build up new beaches.
  Behind these new sheltering sand bars, tidal marshes grow up. They are built of sediment left by waves and washed down from the land by streams.
  Miles of new land like this are built along shorelines where the land has been lifted up so that a gentle slope of the continental shelf is now above water. There are many such beaches along the southeastern United States. For every cliff that crumbles under the hammering of the sea, somewhere a new beach is being built, a new coral reef is growing, or a new volcanic island being thrust up.
  The sea and its shores are ever changing. As glaciers grow or melt, they greatly change the amount of water in the seas. Earthquakes change the shapes of ocean basins. There was a time when much of North America was covered by sea. At other periods Alaska and Siberia were joined by a land bridge, and most of the East Indies were a part of Asia—so high did the land masses rise.
  There will be other changes in the future which we cannot foresee. We can only be sure that through the ages the sea will continue its miraculous labor.