On July 9, 1958, an earthquake with an estimated magnitude of 7.7-8.3 triggered an enormous rockfall in a remote bay along the Gulf of Alaska. The seven miles long and two miles narrow Lituya Bay was protected from waves by two promontories, separating it from the open sea, and a popular fishing spot for locals at the time. Seen from above Lituya Bay and its two glaciers appears shaped like the letter T, a particular shape caused by the Fairweather Fault, crossing the end of the bay from southeast to northwest.
The earthquake occurred along this fault, triggering a rockfall from the mountains. Estimated 40 million cubic yards of rock fell for 3,000 feet hitting the Lituya Glacier. Ice and water from the glacier contributed to the tsunami generated by the sudden impact on the surface of the sea. Trees washed away be the wave along the slopes of the Gilbert Inlet, on the opposite shore, suggests a maximum wave height of 1,720 feet, taller than the Empire State Building in New York. Howard Ulrich, a fisherman visiting Lituya Bay with his 8-years-old son that day, at first heard a loud rumbling noise from up at the head of the bay, followed a moment later by what he describes as “an atomic explosion.” A “big wall of water,” according to Ulrich 50 to 75 feet high, swept through the bay washing away rocks and trees along the shores. The boat was carried by the wave above the trees and luckily washed back into the bay, both Howard Ulrich and his son survived. Another boat with two persons on board vanished without a trace into the open sea, carried away by the tsunami.
The Lituya Bay earthquake was powerful enough to generate a series of smaller landslides, both in the sea as on land, at a distance of 155 miles from the quake epicenter. Smaller tsunami, with a maximal wave height of 20 feet, were recorded in the Yakutat Bay, Disenchantment Bay, Dry Bay, Glacier Bay, Inian Island, Skagway and Dixon Harbor.
Geological evidence, historical observations, and even myths suggest that such megatsunami are quite common along the Gulf Of Alaska. Since 1853 at least four or five similar events are documented. French explorer Jean-François de La Pérouse who explored Alaska in 1786, noted that the shores of Lituya Bay “had been cut cleanly like with a razor blade,” suggesting that a tsunami occurred shortly before his arrival. Local legends record even earlier events, predating modern explorers and scientists by centuries. A tale told by the native Tlingit Indians locates a mysterious cave deep below Lituya Bay. In the cave lives the evil spirit qa-htu-‘a, similar in appearance to a great toad or frog. If someone dares to disturb its sleep, it will violently shake the land and the sea. Gigantic waves will catch the intruder, transforming it into a bear, common animals in the Alaskan wilderness. According to the legends, qa-htu-‘a still there, ready to send another deadly tsunami at any time.
