Sea-Floor Mapping Goes Inland, to Bear Lake in Utah and Idaho

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Sea-Floor Mapping Goes Inland, to Bear Lake in Utah and Idaho

By Steve Colman
Dec. 2002 / Jan. 2003

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Above: Sidescan-sonar mosaic and new bathymetry for Bear Lake generated from September 2002 operations.
Below: The research vessel Raphael heading out onto Bear Lake from the State Park Marina in Garden City, UT, in September 2002. Lake level is about 5 m below the lake datum, exposing much of the marina breakwater.

R/V Raphael

A team of researchers from the U.S. Geological Survey (USGS)'s Coastal and Marine Geology Program (CMGP) used sea-floor-mapping technology to map the floor of Bear Lake (Utah and Idaho) in September. Bear Lake is a medium-size (11 by 34 km) lake that occupies an active half-graben at the boundary between the Basin and Range Province and the Colorado Plateau. The lake is important as a recreational resource, a fisheries habitat, and a source of water for irrigation and power generation.

Since 1996, Steve Colman (USGS, Woods Hole, MA) has been working with scientists from the USGS' Earth Surface Dynamics Program in Denver, CO, to study the sediment of Bear Lake as a record of past climate and limnology. The primary scientific goals of this most recent survey were to look for evidence of sublacustrine spring discharge and to image possible fault scarps that cut the lake floor. Secondary objectives were to produce a sidescan-sonar mosaic and an updated bathymetric map of the lake. The sidescan-sonar mosaic has potential applications ranging from interpreting sedimentary environments to mapping fish habitats.

In addition to Colman, other members of the survey team were Dave Nichols and Jane Denny (USGS, Woods Hole, MA), Dana Wiese (USGS, St. Petersburg, FL), and volunteer Richard Goldberg (Coastal Carolina University).

The research vessel Raphael was hauled from Woods Hole to Bear Lake to serve as the data-collection platform. Geophysical systems included a sidescan-sonar (Edgetech DF-1000) system, a Chirp subbottom (Edgetech 424) profiler, and an interferometric swath-bathymetry (Submetrix 2000) system.

For the most part, the weather and equipment cooperated, and the results were a high-quality data set. Preliminary interpretation of the data has revealed new insights into the sedimentary environments of the lake, ranging from hemipelagic marl in deep water to debris-flow sand on the fronts of fan deltas. Major fault scarps on the lake floor were clearly imaged, although small-scale fault disturbances visible in subbottom data were obscured in the sidescan-sonar data. Many other features related to such things as spring discharge and the distribution of aquatic snail shells were also observed.

Coastal & Marine Geology Program
U.S. Geological Survey (USGS)

Earth Surface Dynamics Program
U.S. Geological Survey (USGS), Denver, CO

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Dec. 2002 / Jan. 2003

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in this issue: cover story:
USS Arizona

Adriatic Sea Sediment-Transport Cruise

Bear Lake Sea-Floor Mapping

Assateague Island Vegetation Mapping

Field-Testing New Portable Drilling System

Diamondback Terrapin

Transoceanic Dust Impacts

Woods Hole Field Center Open House

St. Petersburg Field Center Open House

Great American Teach-In

Fourth-Graders Tour St. Petersburg Field Center

Girl Scouts 90th Anniversary

GIS Day

Effects of Fishing Activities on Benthic Habitats

Planning Gas-Hydrates Research

Science and Politics in Ecosystem Decisions

Sea-Floor Mapping Techniques

GHASTLI Lab Visitors

Science Museum Board

Two New Scientists

Louisiana Coastal-Restoration Advisory Board

Air Medical Transport Center Tour

MRIB Programmer

New Webmistress

Dec./Jan. Publications List