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

The new airborne geophysical survey data will be collected using a helicopter and will fly over parts of southwest Montana. The survey will begin in July and be completed in about four months, weather permitting.

The purpose of the survey is to support mapping to understand the regional geology of southwest Montana. The geophysical survey will focus near the town of Butte and extend northward over the Boulder Mountains and Flint Creek Range and to the south over the eastern Pioneer Mountains. The region is known for historic and current mineral exploration, and there are several areas that are of high interest for their mineral potential. This region also has incompletely understood earthquake hazards.

Image shows a map of Montana with the survey area marked with a red polygon
2023 Earth MRI Montana Airborne Geophysical Survey Area

Covering more than 2,700 square miles (7,000 square kilometers), the new geophysical survey will use the latest technological developments that will allow scientists to develop high-resolution three-dimensional representations of geology to depths more than 3280 feet (1 kilometer) below the surface.

The 3D models and maps produced from the survey can be used to understand the distribution of groundwater and mineral resources, as well as the potential for natural hazards. Data collected as part of this effort will be made public and used by the MBMG and the USGS to guide more detailed geologic mapping at local scales. 

The helicopter will fly along pre-planned flight paths relatively low to the ground at about 260-300 feet (80-100 meters) above the surface. The ground clearance will be increased to about 1,000 feet (300+ meters) over populated areas and will comply with Federal Aviation Administration (FAA) regulations. Flight line separation will range from 330 to 600 feet (100-200 meters) throughout the survey area. The USGS is contracting with Sander Geophysics Ltd. to collect data.

Low-level flight helicopter with  stinger
Helicopter conducting low-level flights. Image courtesy Sander Geophysics Ltd.

Instruments on the helicopter will measure variations in the Earth’s magnetic field and natural low-level radiation created by different rock types. This information will help researchers develop three-dimensional geologic maps.

The scientific instruments on the helicopter 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.

This survey fits into a broader effort by the USGS, the MBMG and many other state geological surveys, and other partners, including private companies, academics and State and Federal agencies to modernize our understanding of the Nation’s 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, hyperspectral surveys and geologic mapping projects.

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