TAHOE CITY, Calif. – A massive underwater landslide in Lake Tahoe thousands of years ago caused a tsunami and left ripplelike stony ridges on the lake bottom, according to a new study.
Three scuba divers, a robot submarine and researchers from the University of Nevada in Reno and the U.S. Geological Survey spent two years surveying the bottom of Lake Tahoe to piece together the landslide's story.
Their findings are being published in the November issue of Geology magazine.
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The waves created by the slide traveled 12 miles and must have splashed tremendously high when they reached the lake's eastern shore, said survey leader James G. Moore of the Geological Survey.
The landslide weakened the Tahoe shore on the lake's west side where McKinney Bay is today, sending a cascade of boulders, rocks and soil plunging more than 1,500 feet to the lake bottom.
Researchers still haven't figured out what caused the McKinney Bay landslide. Moore speculated that a small-to-moderate earthquake could have triggered the slide.
Such an earthquake, he said, could happen again.
The scientists have not determined the date of the slide, but radioactive carbon dating and fossil evidence suggest it occurred between 7,000 and 15,000 years ago.
Other researchers have discovered at least two significant seismic faults on the lake floor.
They estimate the faults could trigger earthquakes with a magnitude as high as 7 that could generate waves 10 to 30 feet high.