A group of American Indians might have discovered ancient artifacts underwater, USA Today reported. They found odd circles of stones placed in the Straits of Mackinac that may date back 10,000 years. Ice Ages cause massive climate instability—and they leave signs.
According to USA Today, a nonscientist group of American Indians may have found a major scientific discovery. “A team of nonscientists may have inadvertently confirmed the most important finding in Great Lakes archaeology in at least a decade,” the article said.
“The group, made up mostly of Native American tribal citizens, utilized a remote-operated underwater vehicle in the Straits of Mackinac to take a look at Enbridge’s Line 5 oil and natural gas pipelines on the lake bottom. Among the things they found were stones they say appear arranged in linear and circular patterns on the lake floor.”
The article said that if the patterns were made by human hands, it would date back to at least when the Straits area was last above water—which was 10,000 years ago, near the end of the last ice age. There are several signs geologists could use to verify this timeframe.
The Cold Shoulder
How do we know when an ice age has occurred? Geologists look at a wide variety of evidence—especially changes in glaciers.
“Geologists deduce the timing and intensity of these changes because glaciers leave an unambiguous suite of sedimentary features,” said Dr. Robert M. Hazen, Clarence J. Robinson Professor of Earth Sciences at George Mason University in Fairfax, Virginia. “First and foremost of these glacial leftovers are thick, irregular layers of diagnostic rocks called ’tillites.’
“Tillites preserve chaotically jumbled piles of sediments that are carved out and concentrated by the action of ice flowing over rock—that includes sand and gravel as well as angular rock fragments and fine rock flour.”
In addition to tillites, Dr. Hazen said, glaciers alter their landscapes in diagnostic ways. For example, they leave behind long, rounded outcrops of bedrock that were shaped by so-called “rivers of ice.” These ice rivers also carried rocks that shaped and scratched the outcrops of bedrock in telltale ways that other meteorological phenomena don’t.
Sign of the Times
Dr. Hazen said that scientists don’t rely solely on tillites and bedrock outcroppings to give them clues about ice ages like the one that ended when the Mackinac stone alignments would have been made.
“Other geologic clues to glaciers are thick deposits of finely layered ‘varved sediments,'” he said. “Paper-thin, alternating light and dark layers represent seasonal runoff deposits into glacial lakes—coarser in the spring and finer in the fall. Added to these sedimentary features are erratic boulders and mound-like accumulations of gravel called ‘moraines.'”
One or two of these signs may not mean much on their own, but Dr. Hazen said that when they’re found in conjunction with one another, they provide ample evidence of glaciation, which helps scientists date ice ages. He provided additional insight into the matter.
“As a geologist, you’re trained to spot such evidence when you go into the field. And, indeed, field geologists around the world have discovered that these glacial features occur abundantly in rocks of ages between 580 and 740 million years old, just about everywhere they look around the world. These data have piled up for more than half a century.”
Scientists will study the findings of the Straits of Mackinac and determine their origins, possibly leading to new discoveries about the time of their construction.
Dr. Robert M. Hazen contributed to this article. Dr. Hazen is Clarence J. Robinson Professor of Earth Sciences at George Mason University in Fairfax, VA, and a research scientist at the Geophysical Laboratory of the Carnegie Institution of Washington. Professor Hazen earned his bachelor’s and master’s degrees in geology from the Massachusetts Institute of Technology. He earned a PhD in Earth Science from Harvard University.