| Lituya Bay | |
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| Location | North Pacific Ocean |
| River sources | Lituya Glacier Cascade Glacier Crillion Glacier |
| Countries | United States |
| Max. length | 14.5 km (9.01 mi) |
| Max. width | 3.2 km (1.99 mi) |
Lituya Bay ( /lɨˈtjuːjə/; Tlingit: Ltu.aa,[1] meaning "No Lake Within") is a fjord located on the coast of the Southeast part of the U.S. state of Alaska. It is 14.5 km (9.0 mi) long and 3.2 km (2.0 mi) wide at its widest point. The bay was noted 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.
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The smaller Cascade Glacier and Crillon Glacier glaciers and the larger Lituya Glacier all spill into Lituya Bay, which is a part of Glacier Bay National Park and Preserve. Cenotaph Island is located roughly in the middle of the bay. The entrance of the bay is approximately 500 m (0.31 mi) wide, with a narrow navigable channel.[2]
The bay is known for its high tides, which have a range of approximately 3 m (9.8 ft). Tidal currents in the entrance reach 9.4 km/h (5.1 kn). The entrance is considered dangerous to navigation, especially when the tidal currents are running, but the interior of the bay provides good protection to anchored ships.[2]
Lituya Bay is also famous for hosting four recorded tsunamis over 100 feet: in 1854 (395 feet high), 1899 (200 feet), 1936 (490 feet), and 1958 (1740 feet).[3][4]
The same topography that leads to the heavy tidal currents also created the highest wave from a tsunami in recorded history. On July 9, 1958, an earthquake caused a landslide in the Crillon Inlet at the head of the bay, generating a massive megatsunami measuring 524 m (1,719 ft). For comparison, the Empire State Building is 448 m (1,470 ft) high including its antenna spire. The wave possessed sufficient power to snap off all the trees up to 1,720 feet (520 m) high around the bay. Most of these were spruce, and most were 6 feet (1.8 m) thick. The wave stripped the soil down to the bedrock around the entire bay. There were three fishing boats anchored near the entrance of Lituya Bay on the day the giant wave occurred. One boat sank and the two people on board were killed. The other two boats were able to ride the waves. Among the survivors were Adam Gray, William A. Swanson and Howard G. Ulrich, who each provided accounts of what they observed. Based on Swanson's description of the length of time it took the wave to reach his boat after overtopping Cenotaph Island near the bay's entrance, the wave may have been traveling up to 600 mph. When it reached the open sea, however, it dissipated quickly. This incident was the first direct evidence and eyewitness report of the existence of megatsunamis.[3]
The 1,720-foot (520 m) wave runup at the head of Lituya Bay where the landslide occurred, and the subsequent large waves along the main body of the bay (measuring between 200 to 30 feet high) 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 and ice, acting as a monolith, impacted the bottom of the inlet with great force. 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 1,300 feet (400 m) of ice along the entire front of the Lituya Glacier. Also, the impact resulted in water-splashing action that reached the 1,720-foot (520 m) 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 (1.1 m), and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated, generated the giant 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.