Fascinating Sinkholes in Lake Huron Shed Light on Earth’s Condition Billions of Years Ago
Studies conducted by scientists in Lake Huron from the University of Michigan recently have shed light on some very interesting connections between sinkholes in Lake Huron and the development of life on Earth as we know it.
Let's go back in time: Billions of years
Nearly 3 billion years ago, in the Precambrian Era, the foundation for what eventually became the Great Lakes Basin was formed, according to Wikipedia. There was frequent volcanic activity at the time and other stresses which helped form the northern areas of the basin called the Canadian Shield.
Later, the glaciers we've all learned about began the process of repeatedly advancing over the Great Lakes region which flattened the surface and moved large boulders thousands of miles. Every time the glaciers retreated, melting ice turned to water and eroded valleys, rivers, and lake basins.
The actual Great Lakes began to form in the basin from 14,000 to 4,000 years ago when the last glacier retreated. They exposed the basins they had carved into the land filled with the meltwater from the ice.
Fast forward: Sinkholes discovered in 2001
In 2001, mysterious sinkholes were discovered in northern Lake Huron, not far from the Michigan coast and they almost immediately brought researchers from all around the world to investigate them. An interesting short documentary from PBS shed some light on the subject.
Observations during expeditions conducted the following year and in 2003 revealed groundwater actively seeping into three of the sinkholes, including the Middle Island, Misery Bay, and Isolated sinkholes. The groundwater vents at the bottom of these sinkholes, where groundwater seeps into the lake, contain unique biogeochemical conditions different from those found in typical lake water. This is what paved the way for a fascinating theory reported earlier this year.
A link to the past: Sinkholes provide a surprising clue to Earth's history
In August 2021, researchers published findings in the journal Nature Geoscience after studying the Lake Huron sinkholes.
The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.
Now an international research team is proposing that increasing day length on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.
Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.
The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its rotation rate. While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy. - Article from Jim Erickson on the University of Michigan website
So it turns out that this area of Lake Huron, just off Michigan's coast, is playing a big role as we continue to learn about the development of life on Earth. You can read and watch much more, and get deep into the science about this, in the links embedded throughout this article.