GEOLOGY

Detailed explanation-1: -As the tsunami waves become compressed near the coast, the wavelength is shortened and the wave energy is directed upward-thus increasing their heights considerably. Just as with ordinary surf, the energy of the tsunami waves must be contained in a smaller volume of water, so the waves grow in height.

Detailed explanation-2: -A tsunami only becomes hazardous when it approaches land. As a tsunami enters shallow water near coastal shorelines, it slows to 20 to 30 mph. The wavelength decreases, the height increases, and currents intensify.

Detailed explanation-3: -As the wave encounters shallower water the speed of a tsunami wave slows and the height increases. In about 300 feet of water, a tsunami wave will slow to about 60 mph and in 30 feet of water the wave will slow to 20 mph.

Detailed explanation-4: -When the tsunami reaches shallow water near the coast, friction with the ocean floor causes the long wavelength to decrease suddenly. The wave height increases and the tsunami becomes a towering wall of water.

Detailed explanation-5: -Tsunamis generally reach a maximum vertical height onshore, called a run-up height, of no more than 100 feet above sea level. A notable exception was the 1958 tsunami triggered by a landslide in a narrow bay on Alaska’s coast. Its over 1, 700-foot wave was the largest ever recorded for a tsunami.