Tsunami
From ArticleWorld
A tsunami is a natural hazard, created when a large amount of water is displaced by an event like an earthquake, landslide or volcanic eruption.
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Causes
A tsunami can range from unnoticeable events, to devastating disasters. A series of waves is created, when large amounts of water are displaced, by some other event. Undersea earthquakes are the most common cause of tsunamis. Even small undersea earthquakes can cause a tsunami if it creates an undersea landslide. Undersea volcanic activity is another common cause of tsunamis. A volcanic eruption can lift a column of water, creating large waves. Meteor impacts, as well as land-based earthquakes, landslides, and volcanic activity have also been known to cause tsunamis,
Characteristics
Unlike a regular wave that has air behind it, a tsunami is more like a fast moving, very high tide. It raises the entire depth of the ocean, not just the surface. The huge amount of energy, behind this wall of water, is enough to carry large ships for miles inland, or scrape the bare earth down to its bedrock. A single tsunami may be many waves of varying heights. Compared to typical wind-generated waves, tsunamis usually have very long periods of time between waves, and the waves are much longer, up to several hundred kilometers. A regular wave is usually about 150 meters.
Warning signs
Although tsunamis cannot be predicted with certainty, there are some warning signs of pending danger. One of the earliest warning signs may come from animals. Nearby animals often sense danger and flee to higher ground long before the water arrives. The characteristics of the waves themselves can also give an idea of how destructive the tsunami might be. Of course, for low-lying coastal areas, any earthquake is a major warning sign of a possible tsunami. Additional danger lies in thinking the danger has passed, before all the waves have hit. The long period between waves can lull people into a false sense of security.
Shaping our world
The effects of tsunamis, and the events that cause them, continually change and shape the face of the earth. Throughout history, landforms and human settlements have been altered or destroyed. The National Weather Service Forecast Office speculates that the Chesapeake Bay may have been formed by a huge meteor impact, and resulting tsunami. Coastlines around the world have been subjected to the force of tsunamis, and no method of prevention is in sight.