(MOW) Coastlines Lesson

Coastlines

Beachfront property is often a hot commodity, but many do not consider how living along the shore can be challenging and sometimes outright dangerous. Ocean waves, tides, changing sea level, and natural hazards can really put a damper on oceanside living conditions.

First, it is important to consider that the shape of a beach is constantly changing. Waves usually approach the shore at an angle and cause beach erosion at one end but simultaneously build it up at the other end. Every time a wave breaks on the shore, it carries sand to different locations causing different patterns and shapes unique to each beach. 

Tides influence the shore in the natural rise and fall of the sea level along the coast. As previously stated, the tidal cycle can range from 1 to 15 meters. Organisms that live along the coast must adjust for these types of changes. Plants and animals must adapt to the extreme temperature changes associated with high and low tide, and humans must consider the amount of water that will influence coastal activity.

Another important consideration for living along the coast is the constant change in sea level. Although sea level has been at its current location for about 2,500 years, there are several contributors to consistent changes in sea level. One contributor is the tectonic motion of the continental plates. As the plates move up or down as they adjust to one another, the corresponding sea level along the shore will change. Additionally, storm surges, seiches, El Nino, and other effects can contribute to sea level changes.

Yet perhaps the most commonly recognized influences to the coastlines of the world are natural hazards such as tsunamis, cyclones, typhoons, and hurricanes. Tsunamis are caused when earthquakes transmit the energy from the moving earth to the water causing large ocean waves. A tsunami in deep water may have a very small wavelength, but when the wave reaches the shore, the friction from the ocean floor causes the tsunami to grow suddenly and crash on the beach at heights reaching 20 meters. 

Cyclones, typhoons, and hurricanes are all masses of warm, humid, rotating air. The only difference between the three is the location. In the North Atlantic, cyclones are called hurricanes. In the Eastern Pacific, they are called typhoons, and in the Indian Ocean, they are referred to as tropical cyclones. Even in the waters near Australia, they have a unique name, "willi-willis." As the name suggests, all cyclones appear as circular spirals caused by warm air and warm water. Although scientists are not completely clear on how these large tropical storms begin, they do know that as the warm moist air rises from the ocean, it encounters cooler air that causes the warm water vapor to condense. This condensation creates storm clouds which release more latent heat warming the cool air above and a cycle of warming and condensation continues.

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