Lake Tahoe References
Babcock, Heather, ????, Geology and Natural History of Lake Tahoe. http://ceres.ca.gov/tcsf/tahoe-local/geology.html
GeoMapApp. http://www.geomapapp.org
Lopez, Christopher T., Schweickert, Richard A., Lahren, Mary M., Howle, Jim, Kitts, Christopher, Ota, Jeffrey M., and Richards, Bob, 2004, Submarine Geology Within the Western Part of Lake Tahoe, California, GSA Bull.
Reisewitz, Annie, 2009, Scripps Studies Offer New Picture of Lake Tahoe’s Earthquake Potential: Scripps Institution of Oceanography/University of California, San Diego. http://ucsdnews.ucsd.edu/newsrel/science/04-09RenoQuake.asp
Schweickert, ????, R.A., Moore, J.G., Lahren, M.M., Lopez, C., Howle, J.F., Kitts, C., and Ota, J. Lake Tahoe Submarine Geology: Implications for Ancestral Lake, Landslides, and Faults. GSA Bull.
USGS. Selected Oblique Views of Lake Tahoe, CA-NV. http://walrus.wr.usgs.gov/pacmaps/lt-persp.html
Thursday, March 25, 2010
Figure 6: Boulder debris-flow and slope apron
View to west of western part of lake. Boulder-sized clasts in fan-shaped subaqueous debris flow in foreground, and subaqueous slope apron on steeper gradient in background. I would suspect that the debris flow deposits bypassed the apron. This is a quite large debris flow, possibly the result of tectonics or possibly glacial ice damming (see Schweickert, ???? for further discussion of debris flows in Lake Tahoe).
View to west of western part of lake. Boulder-sized clasts in fan-shaped subaqueous debris flow in foreground, and subaqueous slope apron on steeper gradient in background. I would suspect that the debris flow deposits bypassed the apron. This is a quite large debris flow, possibly the result of tectonics or possibly glacial ice damming (see Schweickert, ???? for further discussion of debris flows in Lake Tahoe).
Figure 5: Paleo-shoreline terrace with subaqueous debris flow.
NW corner of lake. 20 ft contour interval. Subaqueous shoreline terrace which may be the site of deltaic deposition as a shallow shelf. This is evidence of a previously lower lake level. A deep subaqueous debris flow occurs to the right, which may indicate a tectonic event, such as a pulse of uplift, earthquake, etc, or sudden influx of sediments/water by means of climatic increase in humidity.
NW corner of lake. 20 ft contour interval. Subaqueous shoreline terrace which may be the site of deltaic deposition as a shallow shelf. This is evidence of a previously lower lake level. A deep subaqueous debris flow occurs to the right, which may indicate a tectonic event, such as a pulse of uplift, earthquake, etc, or sudden influx of sediments/water by means of climatic increase in humidity.
Figures 1 - 4: Lake Tahoe, California-Nevada border, Western US
Shaded colors of satellite topography indicate elevation. 100 ft contour interval. The blue shaded region in Fig. 1 indicates lake surface. Fig. 2 is a bathymetric map of the lake. Drainage basin divides running roughly N-S are likely border faults. The eastern margin is much steeper than the western margin (Fig. 2-4). Abundant fluvial valleys exist on the western margin and on the southern (rift-axial) margin, and are not as abundant on eastern steep margin. Core and submersible data suggest that an extensive lacustrine system existed in the western part of the lake during Late Pliocene to Late Pleistocene, prior to the formation of the modern depocenter (Lopez, 2004). The northern margin is composed of andesitic intrusions following faults, which bisected and dammed a northern fluvial valley (Babcock). During glacial periods, the southern fluvial system was periodically dammed causing fluctuations of lake level of as much as 800 feet above modern lake level (Babcock). Ice-damming in several bays is attributed to be the cause for some boulder-sized debris flows (Babcock).
Shaded colors of satellite topography indicate elevation. 100 ft contour interval. The blue shaded region in Fig. 1 indicates lake surface. Fig. 2 is a bathymetric map of the lake. Drainage basin divides running roughly N-S are likely border faults. The eastern margin is much steeper than the western margin (Fig. 2-4). Abundant fluvial valleys exist on the western margin and on the southern (rift-axial) margin, and are not as abundant on eastern steep margin. Core and submersible data suggest that an extensive lacustrine system existed in the western part of the lake during Late Pliocene to Late Pleistocene, prior to the formation of the modern depocenter (Lopez, 2004). The northern margin is composed of andesitic intrusions following faults, which bisected and dammed a northern fluvial valley (Babcock). During glacial periods, the southern fluvial system was periodically dammed causing fluctuations of lake level of as much as 800 feet above modern lake level (Babcock). Ice-damming in several bays is attributed to be the cause for some boulder-sized debris flows (Babcock).
High-resolution bathymetric maps of Lake Tahoe provide a unique glimse at the subaerial and subaqueous nonmarine depositional systems in a half graben. This enables an examination of the relationships between gradient of a lake basin margin and depositional systems. Furthermore, many perched shorelines both subaerial and subaqueous preserve a record of lake-level fluctuation. Bathymetry of lakefloor is useful in that previous studies Lake Tahoe geology involved (subaerial) geologic mapping and core data.
Lake Tahoe lies within an asymmetrical half-graben, within the Basin-and-Range continental rift system of Western US. The lake basin has changed through time as a result of tectonic and climatic processes. Tectonic processes include rift-related faulting and magmatism. The region experiences magnitude 7.0 earthquakes (Reisewitz), which could produce debris flows. The lake responded to climatic forcing and glaciations by expanding and contracting.
Lake Tahoe lies within an asymmetrical half-graben, within the Basin-and-Range continental rift system of Western US. The lake basin has changed through time as a result of tectonic and climatic processes. Tectonic processes include rift-related faulting and magmatism. The region experiences magnitude 7.0 earthquakes (Reisewitz), which could produce debris flows. The lake responded to climatic forcing and glaciations by expanding and contracting.
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