Mapping the Great Lakes Region in Three Dimensions

The Great Lakes Geologic Mapping Coalition is a partnership of the U.S. Geological Survey (USGS); the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin; and the Canadian province of Ontario. The states receive funding from the USGS National Cooperative Geologic Mapping Program; Ontario takes part without funding. Its mission is to produce three-dimensional geologic maps of the loose sediments and near-surface bedrock of the Great Lakes region. This page summarizes a USGS fact sheet on its work.

Why it matters

Geologic maps underpin most earth science and support exploration for energy, minerals and groundwater, hazard reduction, infrastructure and land-use planning — all of which feed economic development and national security.

Over the last few million years, glaciers repeatedly advanced across the region and retreated, leaving thick sediments, rich natural resources and lasting effects on the bedrock beneath. Bound by that glacial history, and by shared legacies of industrial agriculture and automotive, coal, steel and manufacturing industries, the member states work together to understand where these sediments lie in three dimensions, so policymakers can decide how to find, use and protect resources such as critical minerals, industrial materials and aquifers.

By the numbers:

• The region is home to 26% of the nation's population on 15% of its land.
• It produces 21% of the nation's natural sand and gravel, mined from glacial deposits at lower cost than material from elsewhere — though resources in the aquifers and recharge areas that supply cities such as New York and Chicago aren't counted.
• It contains 35% of the nation's Superfund sites, a legacy of its early industrial power, which makes geologic characterization all the more important.

How the Coalition works

Since it began in 1998, the Coalition has completed more than 100 mapping projects, emphasizing economic and water resources. Typical products are 3D maps and models of sediment thickness, often built from the elevation of the bedrock surface and borehole data, using fieldwork, subsurface modeling and analysis of rock and sediment cores. Member states work with scientists on related STATEMAP, EDMAP and FEDMAP projects, and Coalition scientists engage with Tribal Nations so Tribal interests are addressed.

Example: Minnesota

The Minnesota Geological Survey maps surface and near-surface sediments for its County Geologic Atlas program, which supports groundwater management, mineral development and engineering. With Coalition funding, its staff analyze and correlate sediment cores that anchor cross sections and geologic and groundwater models, and build detailed cross sections that help locate buried sand bodies that may act as aquifers. Since 1995 the Minnesota Department of Natural Resources has used these atlases to describe groundwater conditions and how sensitive aquifers are to contamination.

• The City of Motley, in Cass County, used the survey's subsurface data to site a municipal water well, saving more than $700,000 in drilling costs.
• Cross sections from the Washington County atlas fed groundwater models used to clean up aquifer contamination.
• The Red Lake Band of Chippewa Indians allowed drilling on Tribal land in Koochiching County, supporting subsurface models that could help the Tribe make land-use decisions.

Example: USGS glacial mapping

The USGS Quaternary Geologic Mapping of the Glaciated Regions Project works with the Coalition on the geologic framework of the glaciated United States. As of 2026 it was mapping at Fort Drum in Jefferson and Lewis Counties, New York, at 1:24,000 scale, and in Dodge and Jefferson Counties, Wisconsin, at 1:100,000. Its maps inform sand and gravel resources, aquifers, groundwater contamination pathways, potential critical-mineral placer deposits, landslide and slope-failure hazards and the shape of the bedrock surface, using geophysics, dating of sediments and laboratory analyses.

A USGS scientist examines an outcrop of sand and gravel at Fort Drum, New York. Photo by G. Colip, USGS.

Sources

• U.S. Geological Survey: "The Great Lakes Geologic Mapping Coalition—Working collaboratively to understand the geology of the Great Lakes Region," Fact Sheet 2026–3010.
• Works cited in the fact sheet include Swezey and others (2022); Rupp and others (2021); Lusardi and others (2018); U.S. Census Bureau (2022); U.S. Geological Survey (2025); and U.S. Environmental Protection Agency (2024).