Tsunami-generated boulder ridges in Lake Tahoe, California-Nevada
Tsunami-generated boulder ridges in Lake Tahoe, California-Nevada
Geology (Boulder) (November 2006) 34 (11): 965-968
- acoustical methods
- algae
- bathymetry
- boulders
- California
- Cenozoic
- clastic rocks
- clastic sediments
- cobbles
- collapse structures
- cores
- depositional environment
- diatoms
- dredged samples
- erratics
- geologic hazards
- geophysical methods
- geophysical surveys
- glacial environment
- glaciated terrains
- image analysis
- lacustrine environment
- lake sediments
- Lake Tahoe
- landslides
- laser methods
- lidar methods
- marine environment
- mass movements
- microfossils
- Nevada
- Placer County California
- Plantae
- Pleistocene
- Quaternary
- radar methods
- sedimentary rocks
- sediments
- shelf environment
- siltstone
- slope stability
- slumping
- sonar methods
- surveys
- tsunamis
- United States
- upper Pleistocene
- video methods
- wave-cut platforms
- boulder ridges
- McKinney Bay
An array of east-trending ridges 1-2 m high and up to 2 km long occurs on the Tahoe City shelf, a submerged wave-cut bench <15 m deep in the northwest sector of the lake. The shelf is just north of the amphitheater of the giant subaqueous 10 km (super 3) McKinney Bay landslide, which originated on the west wall of Lake Tahoe. Images from a submersible camera show that the ridges are composed of loose piles of boulders and cobbles that lie directly on poorly consolidated, fine-bedded lake beds deposited in an ancestral Lake Tahoe. Dredge hauls from landslide distal blocks, as well as from the walls of the re-entrant of the landslide, recovered similar lake sediments. The McKinney Bay landslide generated strong currents, which rearranged previous glacial-derived debris into giant ripples creating the boulder ridges. The uncollapsed part of the sediment bench, including the Tahoe City shelf, poses a hazard because it may fail again, producing a landslide and damaging waves.
