The Other Great Alaskan Earthquake


Map of Lituya Bay, showing extent of damage from tsunami (USGS)

Map of Lituya Bay, showing extent of damage from tsunami (USGS)

Sixty years ago this month, on the quiet evening of July 9, 1958, the Fairweather Fault in Southeastern Alaska shifted 21 feet laterally and three feet vertically, a ML 7.8 earthquake. The violent shaking caused a massive landslide at the head of the Lituya Bay, on the northeasterly wall of Gilbert Inlet. From as high as 3,000 feet up, an estimated 90 million tons of rock and debris plummeted down the 40° slope in to Gilbert Inlet at the face of Lituya Glacier. The wave generated by the rockfall stripped Gilbert Point, on the other side of the Inlet, of trees and soil, down to bedrock, to an absolutely astonishing 1,720 feet above sea level. From there, the tsunami wave careened and ricocheted down Lituya Bay, ripping down trees six feet in diameter as far as 3,600 feet from the shoreline.

Portion of Gilbert Point, showing extent of wave scour and trimline

Portion of Gilbert Point, showing extent of wave scour and trimline (USGS)

There were three fishing boats in Lituya Bay that evening. One boat amazingly survived. One boat was wrecked on the spit at the mouth of the Bay but the people on board survived. The third vessel disappeared without a trace. The stories of the survivors are simply terrifying.

WC visited Lituya Bay aboard the R/V Acona in 1967, nine years later. The Bay was still full of dead tree trunks. In a wide swath all along the shoreline, the banks of the Bay were scrubbed to bedrock. And there was nothing at all growing on the towering rock at Gilbert Point.

Some very nice work by the late Don J. Miller,1 a U.S. Geological Survey geologist, who had done research in Lituya Bay before the earthquake and was on the scene the day after, documented the effects of the quake and the tsunami. Practically while the wave was still sloshing around in Lituya Bay.

His 1960 paper might be the best bit of Alaska geological writing, especially when you consider it was published about eight months after the quake. What might be even more amazing is the Miller carefully documents as many as four earlier, similar giant tsunami waves in Lituya Bay, going back to the early 1800s. He found “trimlines,” places where earlier tsunamis had stripped trees from the shore.

Now “trimline” is a serious understatement. Imagine a force that snaps off full grown Douglas Fir and Sitka Spruce trees at their bases, that scrubs mussels and barnacles off rocks and scours off a meter or more topsoil. That’s what Miller calls a “trimline.” And it’s happened multiple times on Lituya Bay. Part of the purpose for that geology paper was to defend the then-incredible claim that a tsunami wave had been 1,720 feet high, more than eight times the prior recorded height. Miller does so, not just with evidence from the 1958 event but by carefully documenting other, earlier events. It’s also about the most exciting geology paper you’ll ever read, with narratives from the four persons who survived.

If geology papers aren’t your thing, the USGS for this 60th Anniversary did a twitter stream of the event. It’s a fun read.

It turns out Lituya Bay is a natural splash tank, a place that might have been designed for huge waves. Steep-walled fjords, a lengthy major fault and repeated glaciation have created a gigantic deep-water, landslide-prone, tsunami-prone ripple tank.

There aren’t many harbors along the Gulf of Alaska coast between Icy Straits and Yakutat Bay. Lituya Bay might be the best of them. Just don’t be there in an earthquake.

 


  1. Sadly, Don Miller and a young assistant drowned in the Kiagna River while doing field work in 1961. 
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2 thoughts on “The Other Great Alaskan Earthquake

  1. Very interesting read. I remember well the 1964 Great Alaska Earthquake and the effects of that occurrence. I can’t imagine a wave of 1680 feet in height taller than the Empire State Building. Thank you for posting this information WC

  2. Thanks for the link to Millers paper. The review of previous wave events and possible causes was even interesting … yes I still have a bit of the geology hydrology bug after years of no practical application. And the eyewitness accounts from 1958 were amazing. I was imagining what it was like for 7 year old (I was 9 at the time) to ride out a wave that large with a “small” crest on top as big as the Columbia River bar when it is up and roaring. The biggest wave I have ever been on was about 50 feet on the Columbia River bar.

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