Complex Geology of Tahoe Basin, Emerald Bay


Alex Wierbinski's picture

By Alex Wierbinski - Posted on 19 March 2019

 

HIGH SIERRA GEOLOGY

Lake Tahoe, Emerald Bay, and the Sierra Crestline
Emerald Bay, Lake Tahoe, USA, Credit to GSA & R.A. Schweickert et al.

Emerald Bay, Lake Tahoe, USA, Credit to GSA & R.A. Schweickert et al, large. Map.

 

Complex Geology of Tahoe Basin, Emerald Bay

Underwater surveys in Emerald Bay reveal the nature and activity of Lake Tahoe faults,
Geological Society of America, March 16, 2019.

MAIN POINTS

Tahoe Basin
“...Lake Tahoe region is rife with active faults, many of which have created the dramatic and rugged landscapes. The Lake Tahoe region lies between the Sierra Nevada microplate to the west and the Basin and Range Province to the east. Northwestward movement of the Sierra Nevada microplate creates stresses that may produce both strike slip (horizontal) and vertical movement on faults.”

Two Key Faults
“Two of these faults—the Tahoe-Sierra frontal fault zone (TSFFZ) and the West Tahoe-Dollar Point fault zone (WTDPFZ)—stretch along the western side of Lake Tahoe, but their continuity across landscapes and the nature of their movement has been debated for nearly two decades.”

Boundaries Unknown
“...location and geometry of the boundary between the Sierra Nevada microplate and the transtensional Walker Lane belt of the Basin and Range Province in the Lake Tahoe area have been debated.”

Focus: Emerald Bay
“We found plenty of evidence for scarps (i.e., faults) that cut the glacial moraines all along the west side of Lake Tahoe, in particular around Emerald Bay.”

“Emerald Bay, a famous scenic locality at the southwest end of Lake Tahoe, is at the juncture between the TSFFZ and the WTDPFZ.”

Going Deep
“Using a remotely operated vehicle, or ROV, and previously published multibeam echo sounder imagery, the team created a detailed map of the bathymetry (depth and shape) and geology in Emerald Bay. ”

Young Faults
“...evidence of scarps cutting across submerged glacial deposits and lake sediments, along with landslide deposits that toppled into the bay after the glaciers melted. Based on the age of nearby moraines, Schweickert says the scarps in most cases are younger than about 20,000 years old.”

Different Directions
Up & Down
“After studying the ROV, bathymetry, and LiDAR data, the team noted that over the past 20,000 years, the TSFFZ and WTDPFZ were moving vertically, with no strike slip motion.”

To the Northwest
“Ten to 15 years of satellite GPS measurements show a northwest movement for the Lake Tahoe region, relative to the interior of North America. But the TSFFZ and WTDPFZ don’t reflect that direction of movement—at least not recently. ”

Desolation Wilderness
“...landforms around Emerald Bay, thought to be roughly 100,000 years old, look like they experienced right lateral, strike slip movement sometime in the past.”

Dancing Rock
“Faults can move in different directions over long periods of time,” he says. “Just because we see some them doing something right now doesn't mean that they didn't have a more complex history in the not too distant past.”

Final Answer, for Now...
“This study clearly demonstrates that the TSFFZ is the active structural boundary of the Sierra Nevada microplate and that the TSFFZ has a higher rate of slip than the WTDPFZ. ”

 

Earlier GSA Research

High Sierra Geology: The Genesis of Lake Tahoe: Ancient Lava Dams

 

 

Informative

USGS

Lake Tahoe Faults

USGS in the Tahoe Basin

Tahoe Facts

 

 

LTBMU

Geology of the Lake Tahoe Basin

 

 

Trail Guide

Backpacking Map
Southwestern Tahoe Basin, TYT, PCT, & TRT

 

 

History of Lake Tahoe

Early Tahoe: First Trans-Sierra trips & First Observation by White Boy

History of Tahoe National Forest

Mark Twain's Sierra Nevada: Quotes from Roughing It

 

Photographs

William M. McCarthy Photograph Collection,
1905-1938

 

 

High Sierra Geology

March 2019 News of Man & Nature

 

 

 

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