A team of geologists at the Illinois State Geological Survey (ISGS) is taking to the sky to peer beneath the Earth’s surface by flying a drone with a magnetometer attached to measure the magnetic intensity of objects found on and below the Earth’s surface.
Mitchell Barklage, an ISGS geophysicist, called the new approach “an idea that was born out of COVID-era restrictions.”
“We originally planned to tow a magnetometer behind a boat to gather this data, but we would not be able to maintain the six foot social distancing guidelines on a boat, so that no longer was a possibility,” Barklage said, “We had to come up with an alternative solution fast, and while I was playing with my child on the beach, I noticed that the sand grains were sticking to a magnet on my backpack and that’s when it occurred to me that we could deploy the magnetometer via drone.”
Prior to liftoff, geologists program a flight route for the drone based on the location of the intended survey. The magnetometer is then attached to the drone, and operates independently with GPS tracking for location and timing, a wifi connection to download data, and a solid state hard drive to store data.
The magnetometer helps geologists map very small variations in the Earth’s magnetic field, which indicates magnetic materials both above and buried beneath the surface.
For now, Barklage has his sights set on conducting geophysical surveys at Illinois State Beach Park. This isn’t the first time ISGS staff have used drones to survey this area. ISGS and the Illinois Department of Natural Resources (IDNR) Coastal Management Program (CMP) used drones to create high-resolution digital terrain models of the area to better understand shoreline dynamics along the Illinois coast.
“We are looking at geologic processes such as beach ridge and dune formation. There are active ridge forming processes going on at the coast, and up until now, we’ve never been able to acquire this type of data before,” Barklage said, “While we have complementary geophysical data from a helicopter-based survey from a few years ago, HTEM survey, this data provides much greater detail and resolution and will give us new insights into the processes that transform our coastline.”
“For example, we usually have a strip of data missing where the waves crash against the shoreline called the white ribbon, both because you get the churned white water of the waves and because of the white area shown on maps indicating no data coverage. Using a drone has helped us access areas that were previously inaccessible, allowing us to map the transition zone between the beach and offshore with no gaps,” Barklage said, “What we are learning about the future of the coastline is that it is dynamic and changing as lake levels continue to fluctuate with climate change.”
The ISGS team is mapping the upper 30 meters of the subsurface with a focus on the upper 10 meters, which has led to some discoveries that reveal evidence of an already felt environmental impact.
“At many of the areas that we are surveying, erosion has stripped away the land where homes used to be located, but there’s still buried infrastructure, such as gas lines from where those homes existed as far back as the 1930s,” Barklage said.
According to Barklage, the future is bright for this versatile technology.
“We can also use this technology as a tool to aid in environmental remediation by mapping subsurface contamination plumes at previously inaccessible locations. Additionally, we can use this technique as a reconnaissance tool prior to offshore construction and development to identify abandoned and buried infrastructure. We can also use it to see old buried fire pits on land, so it has some archaeological applications, as well,” Barklage said.
The Illinois State Geological Survey (ISGS) is a division of the Prairie Research Institute (PRI) at the University of Illinois Urbana-Champaign.
