A fast moving set of waves, at times hugely destructive, produced by an undersea destruction such as an earthquake, landslide or volcanic eruption. Tsunamis, also known as a tidal wave, means 'harbor wave', which actually have nothing to do with tides. An earthquake alone can create a tsunami, but the effect is thought to be greatly enhanced when an earthquake is followed by an underwater landslide, as was the case in July, 1998 when a set of three tsunami waves out of the sea of Bismark-one reported to be 30 feet high- suddenly roared into the northeast facing coast of Papa New Guinea killing more than 2,200.
These seismic sea waves can move through deep water at 600 miles per hour. They are barely perceptible until they approach shore at which point the grow tremendously as they slow down. Tsunami waves retain their power for thousands of miles. In 1960, 5000 Chileans were killed by a set of tsunami waves triggered just minutes earlier by an offshore earthquake of 9.4 magnitude: 14 hours later the waves reached Hilo Hawaii and killed 61. Nine hours later a tsunami hit Onagawa Japan and killed 150.
Surf lore contains a few stories involving tsunamis. In the 1860's, surfer/farmer A'a Holoua is said to have been swept out to sea along with his wooden house as the first set of tsunami waves hit the northeast coast of the Big Island. Ripping the door from his house Holoua rode back to shore while standing on his make shift surfboard
Maybe more credible, 1965 world champion surfer Felipe Pomer ventured into water at a surf break near Lima Peru with a friend on October 1974 about 1 hour after an earthquake. Not long after positioning themselves on the outside of 3 foot waves, Pomer and his friend were pulled out more than one mile as the water drained from the shore in a typical tsunami prologue. Both surfers then caught and rode separate 10 foot waves, one following the other, pulling out a few hundreds yards off the beach and watched as the waves exploded onto the shore.
