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The giant waves of Lituya Bay

One of the prettiest places in Southeast Alaska has felt some of nature's
most violent behavior.

Lituya Bay, on the Pacific coast about 100 miles southeast of Yakutat and 40
miles west of Glacier Bay, is the site of the largest splash wave ever
recorded. In 1958, a magnitude 8.3 earthquake triggered a tremendous
landslide into the ocean. The wave that followed reached 1,740 feet above
sea level on a hill opposite the slide. The slide also triggered a wave more
than 100 feet high that raced down the bay.

Neil Davis, a Fairbanks author, geophysicist, and emeritus professor at the
Geophysical Institute at the University of Alaska Fairbanks, flew over
Lituya Bay in a Super Cub two days after the earthquake.

"When I got there, it was a truly amazing sight," Davis said. "The bay was
filled with icebergs and trees, and there was a tongue of trees and ice
going out to sea outside the bay."

Seven miles long, two miles wide, and shaped like a T, Lituya Bay is the
only refuge for boats along a 100-mile stretch of the Southeast coast. The
bay, carved by a glacier and nestled within the snow-covered Fairweather
Range, impressed French explorer J. F. La Perouse so that he named it ³Port
of France² in 1798.

La Perouse soon witnessed the dark side of this beautiful place. The extreme
tidal current at the narrow mouth of the bay killed 21 of his men as they
explored in small boats. The current at the bay entrance reaches about 14
miles per hour, twice as fast as the Yukon River at Eagle. After a futile
search for bodies, La Perouse named the only island within the bay Cenotaph,
meaning "empty tomb."

The shallow entrance to the bay was the most predictable hazard at Lituya
Bay, but the absence of Native villages within the bay and distinct lines on
hillsides that separated old trees from newer growth hinted at the other.
The inland part of the bay lies dead on the Fairweather fault, a weak
section of Earth's crust, which, like the San Andreas fault, causes
earthquakes when it fails and slips from side to side.

The 1958 earthquake shook loose millions of cubic yards of dirt and rocks
from a 40-degree slope in the northeast corner of the bay. The rock mass
displaced a large body of water, causing both the splash wave that rose to
1,740 feet and a gravity wave that was 150 feet high at the head of the bay.
The waves sheared and stripped the bark from thousands of trees, some of
them four feet in diameter.

The late geologist Don Miller flew over Lituya Bay 12 hours after the
earthquake. Miller later interviewed the captains of two of three trolling
boats anchored in Lituya Bay at the time of the earthquake. He described
their experiences in the U.S. Geological Survey publication, The Giant Waves
of Lituya Bay.

The wave sunk one boat near the entrance to the bay, killing a husband and
wife. A second boat in mid-bay survived the wave by riding over its crest.
Moving about 100 miles per hour, the giant wave carried the third boat over
La Chaussee Spit and into the open ocean. The captain recalled riding the
wave "like a surfboard" and looking down on trees of the spit as the wave
carried him 80 feet above. The captain and his wife survived the trip
outside the bay, though their boat did not.

The July earthquake in 1958 was not the first time a giant wave had raced
through Lituya Bay. Miller dated the trim lines on the hills and confirmed
witnesses accounts of a several giant waves in 1936, and also found evidence
of similar waves in the 1850s and 1874. Despite the bay¹s violent history,
Miller didn't discourage people from visiting there. He estimated the odds
of a giant wave occurring in Lituya Bay on any given day as 9,000-to-1.

This column is provided as a public service by the Geophysical Institute,
University of Alaska Fairbanks, in cooperation with the UAF research
community. Ned Rozell is a science writer at the institute. This column
first appeared in 2002.

 

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