Robot explores Tahoe’s depths
Sure, you’ve put in hours of sub-committee work trying to save it, personalized your license plate for it and know it was formed between 22,000 and 7,000 years ago by a massive earthquake, tsunami wave and landslide.
You know its darkest mysteries and legends, from untold orchards of dead bodies to a Loch Ness-size rumor of schools of giant blind fish that would make Ahab squirm.
You also know that a Mars rover the size of a remote controlled car has discovered peaks and valleys and weather systems on a planet 34.65 million miles away – so why is it that the secrets of the lake you love have yet to be fully discovered?
A group of scientists from several nearby universities and a team from the United States Geological Survey last week, for the third straight year, explored with a similar robotic rover the shallow depths of Lake Tahoe – one of the deepest Alpine lakes in the world.
The scientists’ goal is to eventually create a topographical map of the natural floor bottom in moderate to deep water, but, along with any exploration comes the ubiquitous questions about the real mysteries Lake Tahoe holds.
“Yes, we do get all kinds of questions,” said Rich Schweickert, professor of Geology at UNR. “I mean, we’re there to explore the bottom of the lake, from a geographical point of view, but that doesn’t mean we don’t see other things.”
But more on that later.
Schweickert is just one member of a team of scientists, led by a crew from Santa Clara University, who’ve used the rover to, during the last week of May, explore the lake’s first “shelf.”
“We found supporting evidence of some of the things we saw last summer,” Schweickert said. “There’s a shallow shelf outward of Tahoe City, it’s very flat-bottomed and extends two miles both east and south.
“The shelf is only 40-feet deep, there are about 12 east/west trending ridges of boulders, about 6-feet high and 30 to 40-feet wide, and length goes for several thousand feet.”
Schweickert explained the topography of this shelf is similar to that of ripples of sand in a shallow creek caused by a steady flowing stream.
“Except orders of magnitude are thousands of times larger,” Schweickert said. “The boulders that make up this region are from fist to car-sized. They got organized into this even and uniform parallel rows of ridges.
“It would have taken very large water waves to go across the shelf. These would have been mega ripples.”
Scientists speculate that a giant tsunami wave just north of McKinney Bay on the West Shore was the epicenter of the tsunami wave which was caused by a landslide of at least 10 cubic kilometers with the ripple effect reaching south to Tahoma and Homewood, creating very flat, smooth lake-floor surfaces.
The topographical evidence and an ash layer in the lake that appears 7,000 years old suggests that this giant-wave event occurred about 5,000 B.C. – albeit that tells scientists nothing of the next such event to occur.
“The last thing we want to do is alarm readership,” Schweickert said. “Yes, there is potential that events like this could happen, but they are a very, very rare event. We know that they happened in the past, but more research needs to be done, more information needs to be (known) about the faults and how landslides occur and things like that.”
Michael Shulters, acting regional director of the USGS based in Menlo Park, Calif., said interpretations of the data can be used for other arenas.
“It becomes a road map of the lake bottom for other research and investigations,” Shulters said.
“There are items of the map that look like artificial artifacts, but it takes further investigations to interpret the data,” he said.
Archeologist Susan Lindstrom has studied the remains of ancient forests that thrived as long as 6,000 years ago on the lake’s pasts shorelines. They are buried under the water line. These forests are now just sporadic stumps, yet some of these stumps measure as high as 10 feet and measure 3.5 feet across.
Lindstrom wrote in the Journal of California and Great Basin Anthropology that more evidence of Native American occupation of Tahoe in prehistoric times could still be buried beneath the water.
Lindstrom said she’s concerned about the potential people scavenging the artifacts found in the depths of the lake for souvenirs. She said that robbing the lake of such artifacts is a disservice to everyone.
“The information that they contain should be preserved for the public,” she said. “It shouldn’t be within the power of certain individuals to rob the public of that information.”
Scientists like Schweickert agree, and while his comments about the nature of what’s been found on the near shelf of the lake are somewhat benign – “no dead bodies”; “no litter or treasure, just one empty beer can” and “no Tessie” – there is potential for finding more, both about the lake’s topography and, other mysteries.
And it comes down, surprisingly, to something seemingly very doable.
“Right now (we’re) limited by the length of the cable,” Schweickert said. “The cable is 700 feet in length, the deepest is 600 feet, the deepest part of the lake is a little over 1,500 feet. We have observed west and north (shores) but not east and south.
“We look forward to finding out more.”
Schweickert said his group is always looking for funding to continue the research and he can be contacted at firstname.lastname@example.org
– Former Bonanza reporter Merry Thomas contributed to this report.
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