CONTACT: Patricia Viets FOR IMMEDIATE RELEASE
Troy Holcombe October 28, 1996
NOAA National Geophysical Data Center
A group of oceanographers studying the Great Lakes has developed topographic maps of the floors of Lake Michigan and western Lake Erie that show features more accurately than ever before, as well as some features that have never been seen before.
The scientists are conducting a Great Lakes data rescue project, using the entire historic hydrographic data base of the United States and Canada -- which consists of several million water depth measurements -- to complete topographic maps of the lake floors (a process called bathymetry). Consequently, a new reconstruction of lakefloor topographic features is emerging as more and more data are rescued.
This project is significant because new bathymetry is needed for environmental decision-making in the heavily populated and industrialized Great Lakes region; for modeling of water circulation and various climate change scenarios; and as a base map for scientifically and environmentally related field work. New bathymetry also builds upon the wealth of geological knowledge from the lands surrounding Lake Michigan and becomes, at once, an important contribution to the geology of the region.
The data rescue project, sponsored by the Commerce Department's National Oceanic and Atmospheric Administration, will be described in a poster session at the annual meeting of the Geological Society of America in Denver on Oct. 28. The session, "Contributions to the Geomorphology of the Great Lakes," will be presented by Troy Holcombe of NOAA's National Geophysical Data Center, and David Divins of the University of Colorado's and NOAA's Cooperative Institute for Research in Environmental Sciences.
Examples of features seen for the first time include: coalescing channels in the deep basins of Lake Ontario; channels excavated by propeller wash in the western basin of Lake Erie; a former delta of the Detroit River; a drowned headland and spits (narrow points of land) in western Lake Erie; and bedrock ledges in the deep basin of Lake Ontario.
Examples of features seen more clearly are: a fault scarp (deep slope) or fault-line scarp in Eastern Lake Erie; karst (an area of irregular limestone altered by erosion) topography in northeastern Lake Michigan; the Mackinac Channel connecting Lake Michigan with Lake Huron; a channel in Green Bay and a submerged delta in Lake Michigan which are records of drainage from Lake Superior during the Chippewa Lowstand; and flat-topped ridges in the islands area of Lake Michigan.
This new bathymetry highlights the need for geographic names for lakefloor features. Although a number of names for Great Lakes lakefloor topographic features have been used informally, up until now none of these lakefloor ridges, plateaus, fans, and channels were officially named. As an adjunct to this project, names that are new or used before for these features are being proposed to the U.S. Board on Geographic Names (BGN). Names for the larger lakefloor features in Lake Michigan and western Lake Erie are now approved by BGN for official use.
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