Tsunamis are long wavelength, low amplitude waves most commonly triggered by earthquakes, landslides, and volcanic eruptions that result in the rapid displacement of water on a massive scale. Although infrequent, fast-moving tsunamis can travel great distances and destroy coastal areas. The effects of a tsunami can range from unnoticeable to devastating. A tsunami may be unnoticed by ships at sea because of its low wave height and long wavelength in the open water. As the tsunami approaches land, the shallow water causes the tsunami to transform to a slower, turbulent wave with greater height. Large tsunamis are often preceded by the retreat of water away from the shoreline, luring unsuspecting beachgoers onto the exposed sea floor moments before the tsunami arrives.
Geologists work together with seismologists and oceanographers to study and understand tsunamis and the geologic forces that trigger them. The results of these studies are critical for identifying areas susceptible to tsunami inundation and for developing effective warning systems.
The animation to the left illustrates how the tsunami from the December 26, 2004 Sumatra-Andaman earthquake travelled across the Indian Ocean.
Image courtesy of NOAA
Recent Tsunami Events Back to top
Tsunamis from Solomon Island Earthquake of April 2, 2007: The Magnitude 8.1 earthquake occurred 40 km south of the Solomon Islands, an island chain located northeast of Australia, and resulted in the deaths of at least 34 people. The earthquake was located so close to the islands that the tsunami reached land before a warning to coastal residents could be issued. Additionally, the earthquake was located at a relatively shallow depth of 10 km, resulting in strong surficial shaking. Recent Tsunami Events Back to top
- The Solomon Island earthquake occurred along a South Pacific subduction zone where the Australia/Woodlark/Solomon Sea Plates are thrust under the Pacific Plate. The earthquake occurred within a portion of the subducting plate that had not produced a Magnitude 7.0 or larger earthquake since the early 20th Century (USGS, Geotimes, Earth Observatory, Earthquake Glossary).
Photographs of damage caused by the Solomon Island tsunami. Images courtesy of People's Daily Online.
- Tsunamis from Indian Ocean Earthquake of December 26, 2004: Also referred to as the Sumatra-Andaman Earthquake, this Magnitude 9.1 event triggered tsunamis that caused more casualties than any other in recorded history. In total, more than 157,577 people were killed, 26,763 are still listed as missing and 1,075,350 were displaced in South Asia and East Africa (USGS). Check out the interactive web page from NOVA's "Wave That Shook The World".
Historical Tsunami Events Back to top
Numerous tsunamis throughout the world have been recorded in human history. Some notable historical tsunami events include:
- Tsunamis from Alaskan Earthquake of March 28, 1964: The Magnitude 9.2 Alaskan Earthquake of 1964 generated a tsunami that devasted many towns along the Gulf of Alaska and caused damage at numerous locations in Hawaii and along the west coasts of Canada and the United States. The maximum wave height recorded was 67 meters (220 feet) at Valdez Inlet, Alaska (USGS)
- Tsunamis from Aleutian Earthquake of April 1, 1946: The Magnitude 8.1 Aleutian Islands earthquake caused only minor damage to buildings on nearby Unimak Island, Alaska, but the resulting tsunami devastated the island's Scotch Cap lighthouse and swept away its five occupants with a wave estimated to be about 35 meters (115 feet) high. The tsunami travelled on to Hawaii where it took 159 lives and caused $26 million (1946 dollars) in damage (USGS, Univ. of Washington, USC Tsunami Research Center)
Links to More Information Back to top
For more in-depth information about tsunamis and earthquakes, check out AEG's Technical References page. Back to top