One of the most devastating and long-lasting natural ocean disasters is a hurricane, typhoon, or cyclone. Although there is no significant difference in the weather pattern that creates these storms, the names are different based on where the storm is located. However, the most devastating ocean disaster is not a hurricane, typhoon, or cyclone. A tsunami is the most destructive natural event that changes the wave action of the ocean and the shoreline. A tsunami can go onshore, and depending on the height of the wave, the elevation of the shoreline, it is possible for the tsunami to destroy homes, people, and the environment with long-lasting effects (NOAA National Weather Service, 2009).
On March 12, 2011, an 8.9 magnitude earthquake shook Japan. Afterward, two more earthquakes of 7.1 and 6.8 shook the island country. . It was not known the extent of the damage, especially the nuclear power plant, Fukushima, which began to leak. The result was a series of 30-50 foot waves that further destroyed homes, rice fields, and engulfed entire towns. The wake of the tsunami left little vegetation, or evidence of human activity near the shore. Barges, containers, and other shipping material were washed as far away as the Western Pacific shoreline. Boats, cars, and trucks were picked up by the massive waves and dropped far inland, ships were turned on their sides, and debris scattered for miles away from shore (NOAA National Weather Service, 2009).
Tsunamis are typically the reaction of the ocean to an underwater earthquake. Usually, the action occurs after one plate slides upward as the other plate is sliding toward the upward moving plate. This causes pressure in the fault line, called the epicenter. The water above the upward moving plate is displaced, which creates an upward wave. As the large wave travels toward the shore, the height of the wave actually stays the same, as the mass of the water contained in the wave is relatively the same height when it comes on shore as it was at the epicenter. The problem is that normal wave action disperses waves as they reach the shore, however the magnitude of the earthquake combined with the amount of water displaced at the epicenter will determine how tall the waves are when they reach land. The high or low tide is not a factor in how high or low the tsunami is. The height of a tsunami is determined by the displacement of ocean floor, the type of earthquake, and the magnitude of the earthquake. Underwater volcanoes and landslides can also cause a tsunami. There are other factors that may generate a tsunami, such as an underwater volcano, landslide, and the breaking of an iceberg (NOAA National Weather Service, 2009).
A tsunami does not necessarily change the wave action of the ocean, however just before a tsunami the ocean may recede and expose the ocean floor. Tsunamis have no connection with the tides as tides are aligned with the sun and moon action. For example, extreme low tide is usually at new moon, and extreme high tide is usually at full moon. The bulge of the ocean depends on where the moon is over the ocean, or more accurately, it depends on where the ocean and the moon are aligned. Tsunamis therefore are a part of terrestrial crust movement, not part of celestial gravitational pull (NOAA National Weather Service, 2009).
Normal waves are generated near the surface of the ocean. A tsunami is generated from the ocean floor to the surface. Normal waves are usually generated by weather patterns such as wind, tides, and currents and seem to have a gentle regular pattern of ebb and flow. According the NOAA National Weather Service (2009), “They [normal waves] have periods of 5-20 seconds, wavelengths of 100-200 meters (300-600 feet), and travel at speeds of 8-100 km per hour (5-60 miles per hour). Tsunami waves have much longer periods of 10 minutes to 2 hours, wavelengths of 100-500 km (60-300 miles), and travel at speeds of 800-1000 km per hour (500-600 miles per hour).” This is one of the main differences between the tsunami waves and normal waves. Tsunami waves can reach inland for at least a couple of miles, depending on the height of the wave or series of waves. The higher the wave, the more inland destruction may occur.
The environmental effects from a tsunami depend on the magnitude of the event, where the event began, how deep the event was in the ocean, and how far the wave travels across the land. Certainly, most tsunamis are in deep ocean environments, which rarely affect the shoreline. However, several large tsunamis have reached the shore, such as the 2010 Japanese tsunami, which Japanese officials are still working on stopping the leak at Fukushima. Ecosystems in the wake of large tsunamis are left devastated. However, nature has a way of healing from such oceanic natural disasters. Humans are the creatures that seem to have the most difficult time cleaning up the havoc and evidence that a tsunami has ravaged human belongings. Trees regrow, wildlife returns, and humans rebuild their lives after a tsunami.
- Pacific Tsunami Warning Center. (2009). NOAA National Weather Service. Retrieved from http://ptwc.weather.gov/faq.php