Media Alert: Low-level helicopter flights to image geology of Lake Superior Basin

The flights are a collaborative effort between the USGS, the Michigan Geological Survey, the Wisconsin Geological and Natural History Survey, and the Minnesota Geological Survey. The USGS Earth Mapping Resources Initiative is a national effort to modernize the nation's maps of geology and mineral resources, and to identify energy and groundwater resources and natural hazards.

"Earth MRI is mapping the critical minerals needed to drive the U.S. economy and bolster national security. By partnering with the state geological surveys of Michigan, Minnesota, and Wisconsin we are also adding to state knowledge of water resources and natural hazards," said Jamey Jones, science coordinator for the USGS's Earth MRI.

The regional airborne electromagnetic survey will yield geologic mapping of water resources and groundwater pathways over the nation's largest freshwater resource, as well as mineral resource potential for an area that has historically been one of the most important areas of mineral production.

These data will cover much of the Lake Superior Basin and will further support efforts to understand groundwater pathways and assist in land-use planning. The Lake Superior Basin is the largest freshwater resource in the country and holds about 10% of the Earth's surface freshwater. Two groundwater-focused projects supported by these flights will contribute to characterization and protection of that world-class resource.

"The new data from the USGS Earth MRI program will greatly improve our understanding of northern Wisconsin's geology, supporting better-informed water resource and land management decisions," said Sue Swanson, director of the Wisconsin Geological and Natural History Survey.

Airborne electromagnetic surveys map changes in the electrical conductivity of rocks beneath the surface, offering new insights into the geologic framework of the area. The survey will cover rocks that record the geologic history of the continent from over a billion years ago to the present.

"The USGS Earth MRI program has consistently improved our understanding of Minnesota's subsurface geology; these north-central Minnesota flights will provide critical information for both water resource and land management decisions in this part of the state," said Bob Tipping, director of the Minnesota Geological Survey.

The regional airborne electromagnetic survey will also yield geologic mapping of mineral resource potential in a historically important areas of mineral production, including for graphite, which is on the List of Critical Minerals maintained by the USGS as essential for the U.S. economy and national security. Graphite is used in batteries, steelmaking, and defense applications, and the United States is at present entirely reliant on imports, primarily from China.

The new geophysical data will be processed to develop high-resolution three-dimensional representations of near-surface geology from the surface to depths up to 1500 ft (roughly 500 meters) below the surface. The 3D models and maps derived from this project are important for improving our understanding of critical mineral resource potential, water resources, groundwater pathways near legacy mining areas, parameters for infrastructure and land use planning.

The helicopter will fly along pre-planned fight paths relatively low to the ground at about 100 - 200 feet (30-60 meters) above the land surface. The ground clearance will be increased as needed and will comply with Federal Aviation Administration regulations.

The USGS has contracted with NV5 and SkyTEM Surveys to collect data. A sensor that resembles a large hula hoop will be towed beneath the helicopter to measure small electromagnetic signals that can be used to map geologic features. None of the instruments carried beneath or on the aircraft pose a health risk to people, animals, or plant life. No photography or video data will be collected.

The aircraft will be flown by experienced pilots that are specially trained and approved for low-level flying. The survey company works with the FAA to ensure flights are safe and in accordance with U.S. law. The surveys will be conducted during daylight hours only. Surveys do not occur over densely populated areas and the helicopter will not directly fly over buildings at low altitude.

The flights will be based out of various Michigan, Wisconsin, and Minnesota airports. Flights and landing areas could shift with little warning to other parts of the survey area as necessary to minimize ferrying distances and avoid adverse flying conditions.

The survey fits into broader efforts by the USGS, the Michigan Geological Survey, the Wisconsin Geological and Natural History Survey, and the Minnesota Geological Survey and 42 other states to modernize understanding of the nation's fundamental geologic framework and mineral resources. The Earth Mapping Resources Initiative includes airborne geophysical surveys like this one, geochemical reconnaissance surveys, topographic mapping using LiDAR technology, hyperspectral surveys, and geologic mapping projects. The data collected will be made freely available to the public on the USGS ScienceBase website.