Geology topics

George B. Tate

Publications and source records attributed to George B. Tate.

3 recordsLinked to original sources

USGS1997

Near bottom velocity and suspended solids measurements in San Francisco Bay, California

Ability to accurately measure long-term time-series of turbulent mean velocity distribution within the bottom boundary layer (BBL) in addition to suspended solids concentration (SSC) is critical to understanding complex processes controlling transport, resuspension, and deposition of suspended sediments in bays and estuaries. A suite of instruments, including broad band acoustic Doppler current profilers (BB-ADCPs), capable of making very high resolution measurement of velocity profiles in the BBL, was deployed in the shipping channel of South San Francisco Bay (South Bay), California in an investigation of sediment dynamics during March and April 1995. Results of field measurements provide information to calculate suspended solids flux (SSF) at the site. Calculations show striking patterns; residual SSF varies through the spring-neap tidal cycle. Significant differences from one spring tide to another are caused by differences in tidal current diurnal inequalities. Winds from significant storms establish residual circulation patterns that may affect magnitude of residual SSF more than increased tidal energy at spring tides.

Conference Paper↗

USGS1994

Bottom stress estimates and sand transport on northern California inner continental shelf

Measurements of velocities and light transmission in the bottom boundary layer on the continental shelf off northern California demonstrate the importance of storms in the transport of sediment along the coast and offshore in this region. Time-series estimates of bottom stress obtained from a combined wave-current bottom boundary layer model in which wave and current measurements from the Geoprobe tripod were used as input show high stress values of 10 dynes cm −2 during two distinct storm events in early February and early March, 1991. These stresses induce significant offshore sediment transport, achieving maximum values of about 0.5 g cm −1 s −1 . The net transport over the entire measurement period from 30 January 1991 to 13 March 1991 was along the coast toward the north and offshore. This transport pattern explains slow migration of low amplitude, broad crescentic dunes along and across this portion of the inner continental shelf.

California↗

USGS1984

Rippled scour depressions on the inner continental shelf off central California

Side-scan sonar records taken during the recent Coastal Ocean Dynamics Experiment (CODE) show elongate, shore-normal rippled depressions of low relief on the inner continental shelf off central California between Bodega Bay and Point Arena. These features extend up to 2 km from the coast into water depths of up to 65 m. The proposed mechanism for their generation is storm-generated bottom currents associated with coastal downwelling during the late fall and winter which scour the surficial fine-sand sediment and expose the coarser-sand substrate in the depressions. The zones of most intense erosion and the irregular spacing of the features may be controlled by submerged rock ledges and other prominent coastal features. The large straight-crested ripples within the depressions (heights to 40 cm; wavelengths to 1.7 m) are probably formed by large-amplitude, long-period surface waves generated by winter storms.

California↗