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Waves and Their Affair with Coastlines

The coast of all continents bear the marks of the sea. Some coastlines, like California's are narrow and rugged. Others, like the Atlantic coastal plain, rise gradually for hundreds of kilometers inland.

Breaking waves shape and form our coastlines. Waves can deposit (deposition) and carry away (erosion) sediment. As waves batter against the coast, they constantly erode and grind away the shore. Rocks and cliffs that are undercut by wave action fall into the sea where waves weather them into sand. Sometimes the eroded material is carried seaward where it is deposited--sometimes forming sand bars. The shape of the coastline is determined by the original materials (i.e. rock types) and their resistance to wave erosion. How quickly erosion along the shore takes place depends on several factors one of which is the amount of energy released by the waves as they approach the coast or shore. Not all waves expend their energy on the shore. They may break farther seaward on sand bars or reefs.

We've only touched the surface of the ocean (waves). You may want to expend (spend) more energy and surf the wave issue further. Some suggested topics for future investigation are: Types of waves (breaker, plunger, spiller, etc.), Kelvin and Rossby waves, types of coastlines and how they are formed, and human interactions that attempt to control erosion of coasts.

Questions that come to mind are:

1. Why do deep water waves sometimes break instead of just getting bigger?

2. If you were standing at the end of a pier with a stopwatch in hand, how would you measure the average wavelength of the waves that pass by?

3. In strong storms at sea, ships often alter their course for safety reasons. They will travel directly into the direction from which the waves and wind are coming from (even if this is not the direction they intended to go in). Why do you think it would be safer to travel into the wind and seas than at an angle across the direction?

4. In extreme (this is different than question 3) storms, ships may turn and travel in the same direction as the wind and waves are traveling (even if this takes them in the opposite direction they had planned to go). Why do you thing this may be safer than traveling into the wind and waves?

5. Why do successive (one after the other) waves that arrive at the beach have different heights?

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