Tsunami, Japanese word meaning “harbor wave,” used as the scientific term for a class of abnormal sea wave that can cause catastrophic damage when it hits a coastline. Tsunamis can be generated by an undersea earthquake, an undersea landslide, the eruption of an undersea volcano, or by the force of an asteroid crashing into the ocean. The most frequent cause of tsunamis is an undersea earthquake. When the ocean floor is uplifted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km (24,000 mi) long, which encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian
MAJOR TSUNAMI DISASTER The worst tsunami disaster in history occurred in December 2004 when a magnitude 9.0 undersea earthquake, centered in the Indian Ocean off the northwestern coast of the Indonesian island of Sumatra, generated a tsunami that struck the coasts of 14 countries from Southeast Asia to northeastern Africa. The International Committee of the Red Cross reported a death toll of more than 250,000 people as a result of the tsunami and the earthquake, with nearly two-thirds of the deaths occurring in Indonesia. High death tolls were also reported in India, Sri Lanka, and Thailand. Geologists calculated that the ocean floor at the epicenter was thrust upward 9 m (30 ft) as a result of the quake
In North America the worst known tsunami occurred in 1964 when an earthquake off the coast of Anchorage, Alaska, created a tsunami that killed 115 people in Alaska, Oregon, and California. Scientists also believe that a magnitude 9.0 quake occurred along the Cascadia fault off the coast of Washington and Oregon in 1700 and generated a massive tsunami. Scientists believe the quake and tsunami converted vast spruce tree forests into saltwater tidal flats.
TSUNAMI HITS THAILAND Ocean water submerges coastal buildings on Thailand’s Phi Phi Island after the worst tsunami in history killed people in 14 countries rimming the Indian Ocean in December 2004. The death toll reached more than 250,000 people. It far eclipsed the death toll caused by the second worst tsunami, which destroyed Lisbon, Portugal, in 1755 and killed 60,000 people.
TSUNAMI DISASTER OF 2004 On December 26, 2004, the world’s most powerful earthquake in 40 years struck deep under the Indian Ocean. The magnitude 9.0 earthquake was centered off the northwestern coast of the Indonesian island of Sumatra. The earthquake triggered a tsunami (massive waves), which spread across the Indian Ocean and crashed into the coasts of 14 countries from Southeast Asia to the eastern coast of Africa. Killer waves hit the coast of Sri Lanka about two hours after the quake. Due to the absence of a tsunami early warning system in the Indian Ocean, coastal communities in the region were not forewarned of the impending disaster. The tsunami was the deadliest in recorded history. The International Committee of the Red Cross reported a death toll of more than 250,000 people as a result of the tsunami and the earthquake. Indonesia, nearest the epicenter of the quake, suffered the largest loss of life. Sri Lanka was the second hardest-hit country, with more than 30,000 people reported dead or missing