El and Bill
New member
Warren asked about the speed of a tsunami in the open ocean. Tsunami waves usually have a wave speed of about 500 mph in the deep open ocean - this is approximately the speed of a modern commercial jet. It requires about 12-15 hours for a tsunami generated along the South American coast to reach Hawaii and about the same time to reach our Pacific NW.
Wave height in the open sea might be no more than a foot and usually is undetected by boaters. When a tsunami reaches shallow water near the coast it is slowed down by friction with the sea floor. The top of the wave moves faster than the bottom causing the sea to rise dramatically, and the energy that had been stored in velocity is translated to wave height.
Tsunamis do not necessarily make their final approach to land as a series of giant breaking waves. They are usually more like a very rapidly rising tide. This may be accompanied by much underwater turbulence, sucking people under and tossing heavy objects around.
The time between the arrival of wave crests may vary from 10 minutes to several hours.
In island areas, such as the San Juan and Gulf Islands, some of the energy of the tsunami is translated into huge currents between the islands, that abruptly reverse direction after the passage of the first wave.
Sediments on the coasts of the Atlantic, Caribbean, and Pacific margins of North America all bear evidence of massive past tsunamis. One large enough to bury most of Long Island and all of Manhatten Island occurred about 300 b.c. The Atlantic, Pacific and Indian Oceans now have warning systems.
Since Columbus landed on an island in the New World, there have been 37 documented tsunamis in the Caribbean. A tsunami warning system is planned to be installed here in 2010.
Wave height in the open sea might be no more than a foot and usually is undetected by boaters. When a tsunami reaches shallow water near the coast it is slowed down by friction with the sea floor. The top of the wave moves faster than the bottom causing the sea to rise dramatically, and the energy that had been stored in velocity is translated to wave height.
Tsunamis do not necessarily make their final approach to land as a series of giant breaking waves. They are usually more like a very rapidly rising tide. This may be accompanied by much underwater turbulence, sucking people under and tossing heavy objects around.
The time between the arrival of wave crests may vary from 10 minutes to several hours.
In island areas, such as the San Juan and Gulf Islands, some of the energy of the tsunami is translated into huge currents between the islands, that abruptly reverse direction after the passage of the first wave.
Sediments on the coasts of the Atlantic, Caribbean, and Pacific margins of North America all bear evidence of massive past tsunamis. One large enough to bury most of Long Island and all of Manhatten Island occurred about 300 b.c. The Atlantic, Pacific and Indian Oceans now have warning systems.
Since Columbus landed on an island in the New World, there have been 37 documented tsunamis in the Caribbean. A tsunami warning system is planned to be installed here in 2010.
