DETROIT – Plenty of secrets hide under Lake Michigan’s waters, including a 9,000-year-old ‘Stonehenge.’ Now, scientists have found something else that’s raised plenty of questions among geologists. Around 40 massive depressions were found beneath Lake Michigan’s surface; what are they, and how did they form?
Researchers from the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory (GLERL) found roughly 40 huge circular holes at the very bottom of Lake Michigan.
These range from 300 to 600 feet in diameter and are located at a depth of about 500 feet. They were found about 14 miles southeast of Sheboygan, a city in Wisconsin. From here, they extend in a linear pattern towards Port Washington.
According to experts, the depressions have a temperature of about 38℉ and almost lack oxygen. Only a few creatures can live in such harsh conditions. Some of these include certain bacteria, opossum shrimp, deepwater sculpin fish, and quagga mussels.
How Were The Lake Michigan Depressions Discovered?
The huge holes were found in 2022 when researchers embarked on a mission to map the Wisconsin Shipwreck Coast National Marine Sanctuary’s lakebed. This protected area contains 36 known shipwrecks, but some speculate there may be even more. In fact, Lake Michigan is home to its own ‘Bermuda Triangle’ where plenty of ships have disappeared over the years.
During the expedition, NOAA researchers spotted these unusual circular depressions at the bottom of the lake. Commenting on the discovery, Russ Green, a maritime archaeologist who took part in the mapping project, declared:
Any kind of new discovery in the Great Lakes is exciting (…). But these features really stand out — they are in deeper water (500 feet [150 meters] ish) and weren’t known before, as far as we can tell.
However, the NOAA researchers were not the only ones who found these unusual holes in 2022. During the same period, Brendon Baillod, a local shipwreck hunter, also spotted these depressions. In an interview with the media, he declared:
There were dozens of them in our search grid.
Despite the initial excitement, researchers could only recently conduct further analyses to better understand what was found. On August 21, 2024, a remotely operated vehicle was used to investigate the matter. Scientists came up with two hypotheses about how the depressions were formed.
How Were The Lake Michigan Depressions Formed?
We’re all scratching our heads wondering what could these things be. (…) This is a whole new avenue of research. I mean, there’s now a geological question in mind. How did they form? Why are they there, specifically in the bedrock?
One of the most likely hypotheses embraced by several experts is that researchers have stumbled upon sinkholes. These are depressions formed by water infiltrations in the lake’s bedrock. Lake Michigan’s bedrock is made of limestone, which can be eroded quite easily compared to other rock types.
If that’s what actually happened, the water infiltrations may have slowly eroded the limestone, forming caverns that might have eventually collapsed and created the sinkholes that can be observed today.
A more recent hypothesis, however, suggests glaciers may have formed the holes thousands of years ago. Lastly, some speculate the holes may be craters. Brendon Baillod, the local shipwreck hunter who discovered the depressions, declared in an interview with Live Science:
I think they might be more accurately called craters, which have formed in the deep bottom sediment due either to water upwelling from below or trapped hydrocarbon off gassing.
But consensus on these holes remains elusive.
