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Accumulated Fragments: A less than friendly wave

It's been 54 years since Lituya Bay and surrounding areas were swept away by a tsunami

Posted: January 8, 2012 - 1:01am
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A hat rests atop of the stump of a living spruce tree to show perspective, the tree was broken off by the giant wave at Harbor Point, mouth of Lituya Bay. The brim of hat is 12 inches in diameter. This tree is located about seven miles from where the wave originated.   Photo by D.J. Miller, United States Geological Survey.
Photo by D.J. Miller, United States Geological Survey.
A hat rests atop of the stump of a living spruce tree to show perspective, the tree was broken off by the giant wave at Harbor Point, mouth of Lituya Bay. The brim of hat is 12 inches in diameter. This tree is located about seven miles from where the wave originated.

On the outer coast of Alaska, halfway between Icy Strait entrance and Yakutat, is a small bay called Lituya.

The entrance to the bay is only 1,637 feet wide with a narrow navigable channel with a maximum sill depth of only 32 feet which separates it from the Gulf of Alaska between La Chaussee Spit and Harbor point. The bay, shaped like a long “T” is, at its deepest, about 720 feet, approximately two miles wide by nine miles long with a small island in the middle called Cenotaph. Looking at the cross bar at the top of the “T”, the south arm is the Crillon Inlet with the North Crillon Glacier dumping in at the South end of the inlet. The north arm of the “T” is Gilbert Inlet with the Lituya Glacier dumping in at the north end of the inlet. In the middle of the two inlets the Cascade Glacier dumps into Lituya Bay. Running north to south, cutting the Lituya Glacier and the North Crillon Glacier, is the Fairweather Fault, also known as the Fairweather Trench.

On July 9, 1958 an earthquake of magnitude 7.7 along the Fairweather Fault was felt over a large area of Southeast Alaska, as far south as Seattle, Wash., and east to Whitehorse, Yukon Territory, Canada. On Khantaak Island in Yakutat Bay, three were killed when the north end of the island slumped into the sea.

At Yakutat, bridges, docks, and oil lines were damaged, a water tower fell and a few cabins were destroyed. Many sand blows and ground fissures were observed on the low coastal plain southeast of Yakutat, and large landslides were reported in the mountains. A cabin collapsed and the ground was fissured at Dry Bay (East River); many sand blows and ground cracks occurred at Dry Bay (Akwe River); and submarine cables were severed in the Haines-Skagway area and at Lena Point (north of Juneau).

Slight damage also occurred at Auke Bay, Juneau, Pelican, and Sitka though the center of the earthquake was just north of Gilbert Inlet.

The earthquake along the fault loosened about 40 million cubic yards of rock that fell 3280 feet into the bay. The splash caused 1300 feet of ice along the entire front of the Lituya Glacier to jump up such that an eyewitness survivor, anchored in Anchorage Cove on the north shore near the entrance, saw it rise into the air and move forward so it was in sight.

“It seemed to be solid but was jumping and shaking; big cakes of ice were falling off the face of it and down into the water,” he said.

After a little while, the Glacier dropped back out of sight and there was a wall of water going over the point (the spur southwest of Gilbert Inlet). That wall of water has been measured at over 1720 feet. For comparison, the Empire State Building is 1470 feet high including its antenna spire. Everything — trees, soil, etc., — right down to bedrock was washed away.

Much of the timber was first growth Spruce measuring 6 feet in diameter at the base. The rock-fall impact in combination with strong ground movements, a 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 wave which swept the main body of the bay.

As the wave moved down the bay, it stretched completely across and up into the trees on both sides (from 30 to 200 feet) removing all trees and vegetation. By the time it had swept over Cenotaph Island the wave was moving approximately 600 miles per hour.

There were three fishing boats anchored close to the mouth of the bay. One was completely destroyed and both people on board died. The other two boats rode the wave and the people aboard survived. Among the survivors were Howard G. Ulrich, William A. Swanson and Adam Gray. The giant wave swept over Harbor Point, the mouth of the bay, La Chaussee Spit and out to sea, dissipating quickly.

One of the survivors, William A. Swanson, recorded that his boat, the Badger, was anchored in about 4 fathoms of water in Anchorage Cove on the north shore near the entrance to the bay. The boat was lifted up and carried across La Chaussee Spit, riding stern first just below the crest of the wave, like a surfboard. Swanson looked down on the trees growing on the spit and believes that he was about 80 feet above the tops as he passed over into the Gulf of Alaska.

This incident was the first direct evidence and eyewitness report of the existence of mega-tsunamis and is considered the world’s largest.

The Bay, a part of the Glacier Bay National Park and Preserve, is also famous for hosting three other recorded tsunamis over 100 feet: in 1854 at 395 feet high, in 1899 at 200 feet, and in 1936 at 490 feet.

The bay is known for its high tides, which have a range of approximately 9.8 feet, and tidal currents in the entrance reaching 5.1 mph. For that reason, the entrance is considered dangerous to navigate. There seems to be a couple tsunami every century in Lituya Bay so if you plan to visit, please take that into consideration, as it’s been 54 years since the last one.

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