Tidal waves or Tsunami have been always a truth with lot of speculation and is still under research. Tidal waves can be described as huge waves emanation from the ocean, which can literally destroy anything that comes under their way. The recently occurring Tsunami on December 26, 2004 in Indonesia and at some parts of India and Sri Lanka is the most dreaded and witnessed example.
From history, there is one episode occurring on August 27, 1883 in the island of Krakatoa in the Dutch which due a tremendous big volcanic explosion, huge waves ranging around hundred feet in the air literally wiped out hundreds of villages and killed a number of people. These waves have been documented to have traveled at the speeds up to 700 miles an hour and their terror was felt at the coast of Australia and California, thousands of miles away.
Similarly in 1946, there was an earthquake in the ocean floor near the Aleutian Islands, which set a big gigantic wave in less than five hours. The speed with which it traveled was around 2,000 miles to struck Hawaii Islands. It just uprooted houses, bridges, cars, bungalows etc in its way and threw them hundreds of meters away. A good number of people had drowned in that wake.
So such huge enormous waves are called Tidal waves or Tsunami which is a Japanese name for it. They are completely unlike the normal waves at sea or those along the shore and they are not at related to winds, cyclones or tides. These waves are usually caused due to disturbance in the ocean floor or mostly due to a big earthquake. Such an earthquake, high on the Richter scale at the bottom of the ocean produces a shock wave that travels through the water with the speed of sound slowly generating and developing in to big tidal waves with the disturbance caused by the earthquake on the ocean floor. The shock is so severe that actually a ship can feel as if being hit by a rock. During earthquakes, the ocean floor shifts or slights and creates a great depression causing an enormous amount of water built-up. This leads to the formation of tidal waves and they then began to move to the shore at very high speeds and washes of the coast within minutes almost generating a new coast.
The recently struck Tsunami of Indonesia, India and Sri Lanka is one of the biggest disasters in recent times to occur on this earth where millions of people died and a bigger number rendered homeless and helpless.