Big Splashes in a Little Bay

On July 9, 1958, an event occurred on the Alaska Panhandle that was so spectacular that it is still talked about among boaters and fisherman and the scientists who studied it. It was the generation of a wave that reached a level of over a quarter of a mile above sea level in Lituya Bay, about 100 miles northwest of Juneau. It was, by an enormous margin, the largest wave ever to have been documented in human history.

The magnitude 8.0 earthquake that shifted the opposite sides of the Fairweather fault (which passes near the head of Lituya Bay) by about ten feet was not extraordinary by Alaska standards. But the jolt dislodged an entire mountainside which crashed into the bay at 9:15 that evening and changed a lot of things. The trees around much of the coast of the bay were swept clear, and a new topography was created. Three small boats were in the harbor at the time, and some of the people who were in those boats are still around to tell the story. One of the boats was washed over the spit guarding the entrance, one rode the wave out at anchor, and the other was swept away, never to be seen again.

Of existing accounts, the story that probably tells it best is that of Mr. and Mrs. William Swanson, who were aboard the boat that was swept over the entrance spit and out to sea. Awakened by the violent motion, Mr. Swanson (aboard their boat, the Badger) noted the time in the pilot's house. A little more than a minute after the shaking was first felt, Swanson looked toward the head of the bay (toward the inland side of the bay through which the Fairweather fault passes, and where the slide was generated) and saw what he thought was the Lituya Glacier rising and shaking off chunks of ice. After a while, said Swanson, the glacier seemed to drop back, but there was a big wall of water going over the point nearby. As it developed, it was that "big wall of water" that denuded the slope opposite the rock slide to a height of 1740 feet.

The scientific account that best summarizes the effects of the 1958 earthquake and rock slide was written by Don Miller of the U.S. Geological Survey. (Miller was later drowned in the line of duty, and there is now a USGS research vessel bearing his name.) Miller estimated that you've got a l-in-9,000 chance of taking a beating if you anchor in Lituya Bay overnight. He based these odds on solidly substantiated evidence accumulated over the last two centuries.

As he has noted, it is not just the 1958 earthquake slide that sloshed into Lituya Bay that has made the place a chancy bet for an anchorage. Big waves have been created repeatedly over the years. The evidence for this can be found in "trim lines" of old forestation and can be dated by examining the tree rings of the uppermost trees that survived injuries from earlier splashes.

These trim lines show that similar, but smaller, waves occurred in Lituya Bay in 1853, 1874, and 1936. It is known that these were not all earthquake generated. The 1936 wave (which rose to a height of 490 feet) was not due to an earthquake: none was recorded, and an earthquake of significant magnitude would certainly have been detected even with the sparse seismographic coverage available at that time. It now appears most likely that the wave was due to the release of water from an impounded glacial lake. It's likely that water had backed up behind a glacial ridge "upstream" of the bay, and then had broken through and flooded all at once. (This type of "break-out" is not an uncommon occurrence in Alaska.) The flood then undermined the lower-lying land around Lituya Bay, and the mountainside gave way and fell in.

Eyewitness accounts tell of three separate waves, each increasing in height, which traveled across the bay at the relatively modest speed of 20 to 30 miles per hour.

Indian oral history describes earlier floods between 1850 and 1860. The flood of 1853 is substantiated by Indian legends of a village that was abandoned on the north shore of Lituya Bay because eight canoes filled with men were lost in the wave. Miller speculates that the wave also could have been triggered by a land slide, possibly under water, since there were no reports of an earthquake.

The message is clear. Lituya Bay is not a place to visit in your 13-foot boat with a 76-horsepower Evinrude.