Seismic and Sidescan Sonar Survey in Lake Mead, Nevada

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Seismic and Sidescan Sonar Survey in Lake Mead, Nevada

By Dave Twichell
July 2000

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Ken Parolski, VeeAnn Cross, and Dave Twichell (Woods Hole Field Center) completed a one-week seismic and sidescan sonar survey in Lake Mead, Nevada, between June 1st and 7th aboard a 26-ft pontoon boat. The work was done in cooperation with Mark Rudin from the University of Nevada, Las Vegas (UNLV). The Edgetech sidescan system and new Knudsen chirp subbottom-profiling system were used and provided good results in shallow water. Even the 100- to 114-degree temperatures didn't deter the crew or gear.

This year's study focused on mapping delta deposits associated with ephemeral streams because the deposits are the source areas for pollutants entering the lake. The largest of the deltas extends about 1 km into the lake, is about 12 m thick, and has numerous slope-failure scars on the delta front. Beyond the delta, a thin layer of sediment partially fills the axis of the former streambed and has been traced continuously for 10 km into the deep part of the lake.

The deposits beyond the delta front appear to be associated with density flows and indicate that sediment and pollutants derived from the streams are more widely spread in the lake than was previously thought. Rick Rendigs, Ken Parolski, and Dave Twichell will be returning to Lake Mead in July to collect cores to see if there is any truth to the story, which at present is based purely on acoustics.

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July 2000

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in this issue: Snake Pond

Delmarva Inland Bays

Barataria Barrier-Shoreline

OBS Recovery

Lake Mead

Joint USGS/BRD/WRD Studies

SeaMap Program

Coastal Erosion

Woods Hole Field Center

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Marine Ecology Workshop

Southern California Academy of Sciences

Penrose Conference

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July Publications List