Sediment pulled from Lake LaSalle — the deepest natural lake fully in Minnesota — is giving researchers at the University of Minnesota Duluth (UMD) an estimated 10,000 years worth of climate data.

"The idea is to figure out how climate change is impacting extreme precipitation and flooding here in Minnesota, and using analysis of the sediment in lakes like LaSalle to do that," said Byron Steinman, PhD, a professor of Earth and Environmental Sciences at UMD.

Using a piston coring technique, the team collected a continuous, undisturbed core of sediment varves — or annually-deposited layers of sediment formed at the lake’s bottom. The core, collected this January, could date back “as far as 14,000 years, to when the glaciers retreated,” said Will Daniels, PhD, assistant professor of Earth and Environmental Sciences at UMD. 

“We more than doubled the depth of the previous coring effort,” Steinman said. “Lakes like La Salle are very rare.”

There are only an estimated 100 varved lakes in the world, and several are located in Minnesota. “Few of them are continuously varved from the present to thousands of years into the past,” Steinman said. “It's extremely rare for a lake to both form and preserve varves.”

Key Points:

• Varves are annual sediment layers in lakes, but they’re extremely rare.
• There are only an estimated 100 varved lakes in the world, and several of them are in Minnesota.
• Researchers collected a core from Lake LaSalle with an estimated 10,000 years worth of climate data.
• Climate data collected can help researchers improve flood frequency predictions and large precipitation events.

The team will now study the chemical composition of each sediment layer to reconstruct past climate history. This data could be used to improve flood frequency predictions and more accurately determine the likelihood of large precipitation events like a 100-year flood.

The research team includes Byron Steinman, PhD and master’s student Abe Underhill from the University of Minnesota Duluth; University of Pittsburgh faculty member Mark Abbott, PhD; and University of Pittsburgh students Cole Barrè (a UMD alum) and Adeel Jehangir.

Header image: Researchers prepare coring equipment on Lake LaSalle in January 2026. Images credit: University of Minnesota Duluth