Tsunami is commonly referred to as a sea monster. It cuts across the sea with an awesome speed. On reaching land, it sucks most of the water out of the harbor; then, the creature may rise more than 100 feet tall and flatten whole villages. Often before a tsunami hits, there is a giant vacuum effect, and water is sucked from harbors and beaches. People see the bare sea bottom littered with flopping fish and stranded boats. This is because waves are made out of crests, or high points, and troughs, or dips between crests, and when a trough hits land first, the water level drops drastically. Usually another wave blasts ashore after 15 minutes, to be followed by succeeding waves, for two hours or more.
Tsunami, a most destructive waves and often wrongly called tidal waves, is not caused by tides or even by the wind, but by underwater earthquakes, landslides or volcanic eruptions. These disturbances cause the seabed to move rapidly, and shift a large amount of water, disrupts the sea surface. A train of waves is set in motion traveling away from the source of disturbance.
Some tsunami many reach heights of 100 feet or more and can race across the ocean at 500 miles an hour. Oddly, in deep water, the waves are only a few feet high but upon approaching shore, this increase in energy and height.
Do you ever wonder what causes waves of this magnitude? Approximately four out five tsunamis occur within the "Ring of Fire," a zone of frequent earthquakes and volcanic eruptions roughly matching the borders of .
the Pacific Ocean. Along the ring's edges, giant slabs of the earth's crust, called tectonic plates, grind together. Sometimes the plates are stuck, and pressure builds, causing the plates to suddenly come apart and slam into a new position. This jolt causes an earthquake. If an earthquake lifts or drops part of the ocean floor, the water above it moves strongly to trigger a tsunami.
Rarely but possible, cosmic collisions can cause a tsunami.