Dangerous Power of Nature : Powerful shock waves in lighthouses

Waves are the forward movement of the ocean's water due to the oscillation of water particles by the frictional drag of wind over the water's surface.

Waves have crests (the peak of the wave) and troughs (the lowest point on the wave). The wavelength, or horizontal size of the wave, is determined by the horizontal distance between two crests or two troughs. The vertical size of the wave is determined by the vertical distance between the two. Waves travel in groups called wave trains.

Waves can vary in size and strength based on wind speed and friction on the water's surface or outside factors such as boats. The small wave trains created by a boat’s movement on the water are called wake. By contrast, high winds and storms can generate large groups of wave trains with enormous energy.

In addition, undersea earthquakes or other sharp motions in the seafloor can sometimes generate enormous waves, called tsunamis (inappropriately known as tidal waves) that can devastate entire coastlines.

Finally, regular patterns of smooth, rounded waves in the open ocean are called swells. Swells are defined as mature undulations of water in the open ocean after wave energy has left the wave generating region. Like other waves, swells can range in size from small ripples to large, flat-crested waves.

Since ocean waves are one of the most powerful natural phenomena on Earth, they have a significant impact on the shape of the Earth’s coastlines. Generally, they straighten coastlines. Sometimes though, headlands composed of rocks resistant to erosion jut into the ocean and force waves to bend around them. When this happens, the wave’s energy is spread out over multiple areas and different sections of the coastline receive different amounts of energy and are thus shaped differently by waves.

One of the most famous examples of ocean waves impacting the coastline is that of the longshore or littoral current. These are ocean currents created by waves that are refracted as they reach the shoreline. They are generated in the surf zone when the front end of the wave is pushed onshore and slows. The back of the wave, which is still in deeper water moves faster and flows parallel to the coast. As more water arrives, a new portion of the current is pushed onshore, creating a zigzag pattern in the direction of the waves coming in.