A new color poster depicting features on the floor of Lake Ontario has been released by the Commerce Department's National Oceanic and Atmospheric Administration. This is the third Great Lake to be depicted with new, highly detailed bathymetry, following Lakes Michigan and Erie.

In addition to the main map, insets show details of bottom relief in part of the Rochester Basin, and in the vicinity of Charity Shoal. Also included are text explaining the geology and geomorphology of the main lake floor features, and a list of references.

The bathymetry was produced with data from the entire historic hydrographic sounding database from the United States and Canada. "These highly accurate data were collected over a period of more than 100 years for nautical charting purposes," said Troy Holcombe, a research scientist at NOAA's National Geophysical Data Center in Boulder, Colo.

Many earlier interpretations of Lake Ontario geomorphology are confirmed by the new bathymetry; and new ideas have emerged that have significant implications for a number of environmental concerns. Holcombe said that certain ridges on the floor of the Rochester Basin may record flow direction of advancing ice and/or subglacial meltwater. In addition, a small circular depression coincides with the feature referred to as Charity Shoal. Although the origin of the feature remains unknown, it bears a "striking" resemblance to a simple impact crater.

Data and imagery from Lake Ontario bathymetry are ready for incorporation into geographic information systems as base layers for various applications. High-resolution digital bathymetry makes possible meaningful quantitative estimates of ecological parameters such as available habitats for fish and other living organisms.

For more information, and to preview poster, visit: http://www.ngdc.noaa.gov/mgg/greatlakes/ontarioinfo.html