The data collection will be conducted through the USGS Earth Mapping Resources Initiative (Earth MRI), a partnership between the USGS and state geological surveys that is revolutionizing our understanding of the nation’s geology and critical mineral resources which are vital to the U.S. economy, national security, and clean energy technology.  

Lyndsay Ball, USGS geophysicist and co-technical lead for Earth MRI electromagnetic surveys, described the data collected through Earth MRI as foundational, with broad applications to multiple disciplines within the Earth sciences. 

“The data not only provide insight into mineral resources, but they’re also needed for understanding water resources, hydrogeology, geothermal systems, and even geologic hazards,” said Ball.  

These airborne geophysical surveys will collect electromagnetic data to provide cross section images of subsurface electrical resistivity that expand the fundamental knowledge of geology underpinning the areas in the following states and regions: 

• Nevada’s Great Basin 
• California’s western Mojave Desert 
• Illinois, Iowa, and Wisconsin Phosphorite Deposits 
• Wyoming’s Cheyenne Belt 
• Michigan’s Upper Peninsula 

The electromagnetic sensors penetrate the shallow subsurface to about 300 to 500 meters (approximately 1,000 to 1,650 feet) deep and measure electrical resistivity, or how well the rocks conduct electricity. This method is particularly useful in mapping variations in sediment and rock type as well as groundwater salinity, which are markers of critical mineral resources such as brine potentially containing lithium, or graphite and clay deposits. 

The various survey footprints were designed in close collaboration with respective state geological surveys with the aim of improving understanding of local geology and resources. 

Officials from the various state geological surveys are optimistic the electromagnetic surveys will complement data generated through other types of Earth MRI surveys, including magnetic, radiometric, and hyperspectral, as well as their own ongoing mapping projects. 

“This upcoming electromagnetic survey will focus on the tri-state area that has high prospectivity for critical mineral potential, and Earth MRI is the best tool to map the region,” said Ryan Clark, a geologist with the Iowa State Geological Survey. “The overlap in data will help us calibrate and validate the surveys through our own geochemical mapping.” 

“The electromagnetic data will be a great complement to our mapping because we can take what we’re seeing at the surface and combine it with the subsurface data to get a more detailed look at our state’s geology,” said Erica Key, senior geologist at the California Geological Survey Mineral Resource Program. 

The initial airborne geophysical surveys may be followed by additional investments, including new geologic maps, geochemical sampling, and other techniques to better understand the region’s geologic framework.

Since 2021, the Bipartisan Infrastructure Law has advanced scientific innovation through a \$320 million investment for the USGS to better map the Nation’s mineral resources, both still in the ground and in mine wastes, and to preserve historical geologic data and samples. Through the end of fiscal year 2024, more than \$160 million has been obligated for Earth MRI initiatives, propelling efforts to make “once-in-a-generation” advancements in the nation’s geologic and geophysical data collections and mapping.