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 Editor: In the public interest and in accordance with Federal Aviation Administration regulations, the USGS is announcing this low-level airborne project. Your assistance in informing the local communities is appreciated. 

RESTON, Va. — Low-level airplane flights are planned over a broad region in central Minnesota to image geology using airborne geophysical technology. The survey will be conducted from Oct 2023 to Nov 2024 for approximately 7 months, weather and wildfire restrictions permitting, with a hiatus during the winter months.

Flights will cover an area of more than 10,000 square miles (28,000 square kilometers) and will include areas within St Louis, Carlton, Aitkin, Itasca, Hubbard, Cass, Crow Wing, Wadena, Morrison, Stearns, and Kandiyohi. 

Image shows a road map of Minnesota with a black polygon showing the location of the survey
A map of the survey area for the Minnesota Earth MRI airborne geophysical survey.

The flights will be based out of Alexandria Airport (Chandler Field) as well as the Brainerd Lakes Regional Airport and Grand Rapids-Itasca County Airport (Gordon Newstrom Field). The flights could shift with little warning to other parts of the survey area as necessitated by adverse flying conditions.  

The purpose of the survey is to provide images that expand the fundamental knowledge of geology the Cuyuna Iron Range, a region known for past production of iron and is also known to have unusually high concentrations of manganese.

The new geophysical data will be processed to develop high-resolution three-dimensional representations of bedrock composition and structure to depths more than 3,280 feet (1 kilometer) below the surface.  

The 3D models and maps 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, and potential risks of naturally occurring radon.  

The airplane will fly along pre-planned fight paths relatively low to the ground at more than 300 feet (100 meters) above the surface. The ground clearance will be increased to 1,000 feet (300+ meters) over populated areas and will comply with Federal Aviation Administration (FAA) regulations. Flights will follow north-south lines spaced about 650 feet (200 meters) apart and east-west lines about 3,280 feet (1 km) apart.  

The USGS is contracting NV5 Geospatial in association with EDCON-PRJ Inc., to collect the data. 

Image: Low-Flying Airplane Maps New Madrid Zone
An example of an aircraft specially modified for low-altitude geophysical surveys. The magnetic sensor (magnetometer) is located at the tip of the "stinger" attached to the rear of the airplane. The survey is designed to measure the magnetic field of the earth, which is related to rock formations that lie below the land surface. Image courtesy of EDCON-PRJ, Inc.

The survey will use a Cessna Grand Caravan C208B fixed-wing aircraft, equipped with an elongated “stinger” mounted to the underside of the cabin extending behind the airplane. Instruments in the stinger and inside the cabin will measure variations in the Earth’s magnetic field and natural low-level gamma energy created by different rock types.  

The scientific instruments on the airplane are completely passive with no emissions that pose a risk to humans, animals, or plant life. No photography or video data will be collected. The data collected will be made freely available to the public once complete. The aircraft will be flown by experienced pilots who are specially trained and approved for low-level flying. The 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.  

The survey fits into a broader effort by the USGS, the MGS and many other state geological surveys and other partners, including private companies, academics and State and Federal agencies to modernize our understanding of the Nations’ fundamental geologic framework and knowledge of mineral resources. This effort is known as the Earth Mapping Resources Initiative, and it includes airborne geophysical surveys like this one, geochemical reconnaissance surveys, topographic mapping using LiDAR technology, hyperspectral surveys, and geologic mapping projects.  

More information can be found here. To learn more about how the USGS is investing the resources from the Bipartisan Infrastructure Law, visit our website. To learn more about USGS mineral-resource and commodity information, please visit our website and follow us onTwitter

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