With a maximum depth of 925 feet, the vast waters of Lake Michigan have always held a sense of mystery and intrigue. Recent research expeditions have revealed a mysterious new surprise: a series of huge craters scattered across the lake floor, first detected in 2022.

The craters were first discovered during a mission to map the bottom of a lake in the reserve, where many shipwrecks have been found. These strange circles that appeared in the sonar images pointed to natural formations rather than anything man-made.

“Any new discovery in the Great Lakes is exciting,” said Russ Green, who led the mapping project. “But these features really stand out; as far as we can tell, they are deeper and were previously unknown.”

Brendan Baylod, a dedicated shipwreck hunter, also noticed the flats while searching for a sunken cargo ship. He was convinced that the circles were craters.

“We had dozens in our search table,” Baylod said. “Most were between 500 and 1,000 feet in diameter and irregular in shape.”

Hidden Craters in Lake Michigan

After processing the data from the initial mapping project, Green and Baylod turned to scientists at the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory (GLERL) for peer review.

The teams joined forces to further investigate the mysterious circles. In 2022, they conducted a detailed survey using a remote-controlled vehicle and determined that each circle was a natural, massive crater. About 40 have been counted, and all the craters extend southward from a point southeast of Sheboygan, Wisconsin, toward Port Washington.

GLERL researcher Steve Ruberg described the craters as “perfect little circles” at the bottom of the lake. However, the team believes there may be more craters deep within Lake Michigan.

Funnels or craters?

These formations bear a striking resemblance to sinkholes previously discovered at the bottom of Lake Huron on the border of Michigan and Canada.

Sinkholes usually form when groundwater melts bedrock, causing the upper layer to collapse. Given the melt-prone limestone bottom of Lake Michigan, the consensus is that these features are karst sinkholes. But some researchers, like Baylod, prefer the term “crater” until more empirical evidence becomes available.

“I think it would be more accurate to call them craters, which are formed in deep bottom sediments by the rise of water from the bottom up or by the release of trapped hydrocarbons,” says Baillod.

A recent investigation found no signs of water leaking from the wells. This shows that groundwater is circulating at the bottom of the lake.

Meaning of craters

Underwater life thrives in these craters, with small fish, freshwater shrimp and invasive quagga mussels “doing their thing in the dark,” Ruberg says.

The exact effects of these craters on Lake Michigan and its ecosystem are not yet clear. But there is still an atmosphere of expectation and curiosity among researchers.

“We will be studying them over the next few years to learn more about how they got here and the role they play in the Lake Michigan ecosystem,” Green said.

Meaning of Lake Michigan

Lake Michigan is the only Great Lake located entirely within the United States and is a vital element of the ecological and cultural heritage of North America. Spanning 22,000 square miles, it spans four states (Wisconsin, Illinois, Indiana, and Michigan) and supports a rich and complex ecosystem.

While native species such as lake trout and whitefish thrive here, invasive quagga mussels challenge the lake’s ecological balance. Formed by glaciers approximately 10,000 years ago, the lake’s limestone basin tells the story of a dynamic geological past.

Future Great Lakes Survey

Recent discoveries of Lake Michigan, particularly the large craters at its bottom, shed new light on its ancient formation and evolution and offer interesting clues as to how this huge body of freshwater came to be. Lake Michigan’s importance is not limited to its geology. It serves as a lifeline for millions of people, supports recreation, commerce, and serves as an important source of freshwater.

The mysteries hidden deep within Lake Michigan highlight its dynamic and changing nature, and there is much more to learn. In fact, only 15 percent of the bottom of all five Great Lakes has been mapped at high resolution. Scientists say we know more about the surface of Mars than the bottom of the Great Lakes.