This is NOT what causes tsunamis.

What, where, and how?
A tsunami (Japanese for harbor wave, tsu meaning harbor and nami meaning wave) can be defined as a series of large waves produced by an underwater earthquake, underwater explosions, surface rock slides and land falls, or cosmic impacts. Thucydides, a Greek historian, wrote about what he believed to be the cause of tsunamis in 426 BC, "The cause, in my opinion, of this phenomenon must be sought in the earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen." Tsunamis happen when an underwater quake (or other causes) sends waves toward shore. For a tsunami to form, the magnitude of the underwater quake must be at least over 6.75 on the Richter Scale. Oceanic plates can cause underwater earthquakes that suddenly move large quantities of ocean water. Tsunamis are not just one wave, but a series of many waves together. In the middle of the ocean, Tsunamis cannot even be felt, but as the waves near shore, their wave height increases and the wavelength decreases dramatically as shown in the picture to the left. Tsunamis have much longer wavelengths than normal wind generated waves. Tsunamis can be as fast as 600 mph and be as tall as 1000 feet tall! Tsunamis can cross an entire ocean in as little as three hours. 80% of all tsunamis occur in the Pacific Ocean, but they are possible in other places, even lakes. Basically, tsunamis are like normal waves, except caused by something much larger than the normal wave and they are obviously much, much more powerful. Usually, the first wave to hit the coast is not the biggest wave. Larger, more powerful waves come later on as the water builds momentum as it nears shore. Tsunamis are not unusual occurrences in Japan, 195 of them (some more major than others) have been recorded there.

As tsunami waves near shore, the wave height increases and the wave length decreases.

Typical sign found on beaches that are prone to tsunamis.


Tsunamis are not as frequent as tornadoes and earthquakes (there have only been 6 major ones on record), but they can cause tons of damage. Tsunamis' massive waves can cause extreme damage not only to the coast it crashes into, but the area around as well. It's large amounts of water being spilled onto the land can cause immediate floods as well as floods that can be prolonged. Waves can topple over buildings and drown thousands of people on the coast and even further inland. Islands take a heavy toll from tsunamis, because they are right in the way of powerful tsunami waves. A recent tsunami occurred during February of 2010. Residents on the biggest island of Hawaii were warned of a potentially dangerous tsunami approaching. The people on the coast rushed to higher ground. the Hilo area was expected to get waves as tall as 7 and a half feet, while other areas got waves only as small as 1 and half feet. No major damage was dealt or lives lost, but the people of Hawaii consider to have "escaped by the skin of their teeth." The tallest tsunami ever recorded (as of 2010) was 1720 feet tall in Alaska. One of the highest death tolls recorded (once again, as of 2010) was the 2004 Indian Ocean Tsunami, which killed 295,600 people. The condition of the shore can minimize the tsunamis damage. Coconut trees and Mangroves can absorb the tsunamis energy. The village of Naluvedapathy, India only took minimal damage from a 2002 tsunami, due to the large wave hitting the 80,244 tree forest on the shore. Suggestions from environmentalists say that high tsunami risk shores should have many trees planted on them, that plan is a green way to go, but the trees also need lots of time to grow to a useful size.

Detection and Warning Systems
A tsunami monitoring system and how it works.

Tsunamis, like all other natural disasters, cannot be prevented or stopped. They can, however, be predicted. Warning systems alert people on the coasts t hat will be hit by a tsunami. Once the coast is alerted, people flee from the danger zones and take shelter on high land. Islanders and people who live on coasts know precautions to take during and after tsunamis.. Tsunamis are detected using pressure monitors, buoys at sea, and wave/tide gauges. Sudden sea level changes can be detected by satellites. Detection is a difficult process, however, as there are many false alarms. Detection and warning systems are extremely expensive- for 50 of them to be installed in the Pacific, it would cost a crippling thirty million dollars. An additional eight million is then needed annually for maintenance.

Tsunami Fail: During World War II, the country of New Zealand attempted to create small tsunamis as weapons artificially by throwing explosives into Shakespear Regional Park; of course, it failed.