Lituya Bay

Lituya Bay is a fjord located at coord|58|38|N|137|34|W in the U.S. state of Alaska. It is 14.5 km (9 mi) long and 3.2 km (2 mi) wide at its widest point. The bay was discovered in 1786 by Jean-François de La Pérouse, who named it Port des Français. Twenty-one of his men perished in the tidal current in the bay.

The bay

The smaller Cascade and Crillon glaciers and the larger Lituya Glacier all spill into Lituya Bay. The bay is famous for its extremely high tides. The entrance of the bay is very narrow, and the tides going into and out of the bay through the entrance also cause very treacherous currents.

Lituya Bay is a part of Glacier Bay National Park and Preserve.

1958 tsunami

The same topography that leads to the heavy tidal currents also created the highest wave from a tsunami ever recorded anywhere in the world. An earthquake caused a landslide in the Crillon Inlet at the head of the bay on July 9, 1958, generating a massive mega-tsunami measuring 524 meters (~1,720 ft.) high. For comparison, the Empire State Building is 448m (1,472 ft) high including its antenna spire. The wave stripped trees and soil from the opposite headland and consumed the entire bay. There were three fishing boats anchored near the entrance of Lituya Bay on the day the giant waves occurred. One boat sank and the two people on board lost their lives. The other two boats were able to ride the waves. Among the survivors were William A. Swanson and Howard G. Ulrich, who each provided accounts of what they observed. When the wave reached the open sea, however, it dissipated quickly. This incident was the first direct evidence and eyewitness report of the existence of mega-tsunamis as a true natural disaster. [http://www.uwsp.edu/geo/projects/geoweb/participants/Dutch/LituyaBay/Lituya0.HTM Don J. Miller, Giant Waves in Lituya Bay, Alaska] ]

The giant wave runup of 1720 feet at the head of the Bay and the subsequent huge wave along the main body of Lituya Bay which occurred on July 9, 1958, were caused primarily by an enormous subaerial rockfall into Gilbert Inlet at the head of Lituya Bay, triggered by dynamic earthquake ground motions. The large mass of rock, acting as a monolith and thus resembling an asteroid, impacted with great force the bottom of the inlet. The impact created a crater which displaced and folded recent and Tertiary deposits and sedimentary layers. The displaced water and the folding of sediments broke and uplifted 1300 feet of ice along the entire front of the Lituya Glacier. Also, the impact resulted in water splashing action that reached the 1720 foot elevation on the other side of the inlet. The same rockfall impact, in combination with strong ground movements, the net vertical crustal uplift of about 3.5 feet, and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated, generated the giant solitary gravity wave which swept the main body of the bay.

Mathematical modeling studies conducted by Dr. Charles Mader, support this mechanism as there is a sufficient volume and an adequately deep layer of water in the Lituya Bay inlet to account for the giant wave runup and subsequent inundation. Because of the similarity to asteroid generated tsunami waves, full Navier-Stokes modeling, as suggested by Dr. Mader, could further verify this impulsive rockfall mechanism. Measurable output parameters derived from mathematical modeling and analysis of the Lituya Bay event, adjusted for scale, can be applied to the calibration, verification and validation of asteroid models of tsunami generation. Based on measured parameters of inundation, speed, and water particle velocities of the giant 1958 Lituya Bay waves, coefficients of friction can be derived empirically which may be used to estimate more realistically attenuation over a land mass, of an asteroid-generated tsunami as it travels chaotically past the sea-land boundary.

References

*Guinness World Records Ltd. (2005). Guinness World Records 2006: 84.
*Mega-tsunami: Wave of Destruction. Horizon. BBC Two 12 October 2000

External links

* [http://geology.com/records/biggest-tsunami.shtml World's Biggest Tsunami: The largest recorded tsunami with a wave convert|1720|ft|m tall in Lituya Bay, Alaska]
* [http://www.extremescience.com/BiggestWave.htm Photos of damage from the 1958 tsunami]
* [http://wcatwc.arh.noaa.gov/web_tsus/19580710/narrative1.htm Eyewitness reports of the tsunami]
* [http://web.mac.com/phfichetdelavault History of Lituya Bay, Tsunami and Laperouse (in French)]