I’m At The Bottom Of A Lake

I grew bored one day back in 2005 and so typed in “glacial lake algonquin” at Google to find out the age of a stone.

During my summer 2005 trip to Mackinac Island, my route took me atop the Turtle’s Back, the highest point of the island. According to tradition, the island is named for the Ojibwa Great Turtle, Michinimakinak, a snapping turtle who both served as an intermediary between men and spirits and provided a resting place for the new world after the old was destroyed in a flood. Michilimackinac, a corruption of Michinimakinong, meant the Place of the Great Turtle–i. e., Mackinac Island and its environs. In another old tale, the name possibly came from a now-extinct tribe who once lived there, known as the Mishinimaki, all of whom but two, a man and a woman, were killed off by an enemy tribe in the distant past. The survivors told their woeful tale to a group of visiting natives, then fled the island and were rumored to have become two spirits who still watch over people from the wilderness. Seeing as the island rests upon the Great Turtle’s back, this is why its highest point, also known as Ancient Mackinac Island, is called the Turtle’s Back.

Thousands of years ago, the part of the island that includes Fort Holmes–the highest point–and Point Lookout was the only part which stood above the waters of the great glacial Lake Algonquin, a monster lake which formed what would later become Lakes Michigan, Huron, and part of Superior. It covered the Straits of Mackinac, part of the northern Lower Peninsula, and part of the Upper Peninsula. As the lake began to drain away with the land’s uplift–the land “rebounding” after the retreat of the glaciers, similar to a sponge puffing back up after being squeezed–it shrank into the Nipissing Great Lakes, which themselves shrank, leaving behind the upper Great Lakes (Superior, Michigan, and Huron) and various inland lakes such as Mullett Lake, Black Lake, and Burt Lake.

As this happened, the rest of Mackinac Island was also exposed, though the tiny part known as the Ancient Island was once all that stood above the waves. Caves that are now situated far inland, such as Skull Cave and Cave of the Woods, are actually sea caves, and were formed long ago when lake wave action carved away the softer rock within them. This means that Skull Cave, which rests just at the bottom of the Turtle’s Back and atop a steep rise, and Sugar Loaf Rock itself, and all of the island’s other natural formations, once stood near the shore of the island–different shores, the more the lake level dropped. The thought of water once lapping at all of these now-inland locations is a strange one.

I was busily tramping my way through the woods atop the Turtle’s Back when it occurred to me exactly where I was–on the most ancient part of the island itself. I immediately stopped to look around myself. It looked like regular woods, not even the thick deep kind that I prefer–these were younger trees, as the island was long ago practically deforested. Yet during this trip I’d noticed something I’d never paid attention to before–almost every dirt trail I wandered showed traces of limestone beneath it. If I looked down long enough, I’d see hunks of the rock peeping out of the soil as I walked over them. I had never noticed these before. I knew the island was mostly limestone but I never knew it was that prevalent. I had just assumed that all of this was dirt and the limestone was mainly contained in the rock formations. I realized I was practically walking along the top of a gigantic hunk of stone and that these very rocks once peeped above the surface of Lake Algonquin so long ago that I couldn’t even imagine it.

The wind was gusting in the trees overhead and I shut my eyes briefly. It sounded almost exactly like waves crashing on the shore. I could almost picture this tiny bit of bluff being buffeted by waves in the distant past, everything that would someday be Skull Cave and Cave of the Woods and Arch Rock and Sugar Loaf still being underwater, and not existing in their current forms just yet. The feeling was an eerie one.

I picked up a rock that was sitting on the trail and looked at it. It was just a normal, plain little hunk of brecciated limestone, worn almost smooth along one side, jagged on the other, even with a trace of a few tiny crystal fragments embedded within it. Nothing much to see. This piece of waterworn limestone, from the oldest part of the island, had once been touched by the very waters of Glacial Lake Algonquin itself. It was upon this island for the War of 1812’s Battle of Mackinac Island, for Pontiac’s Rebellion, for the legendary existence of the Mishinimaki, and likely for the island’s formation itself. It was only much later, when I grew bored one day near the end of the year, that I thought to wonder over what its age must have been.

Stanley’s Prehistoric Mackinac Island gave the date of Lake Algonquin as around 14,000 BC, making the rock at least around 16,000 years old. Other, perhaps more up-to-date sources placed the existence of Lake Algonquin as around 10,000 years ago, give or take a millennium. So at the very least, the rock was likely about 10,000 years old (this not taking into account the processes involved in forming the rock, which would have been considerably longer). It was impressive thinking over all the things this rock could have seen, if a rock were able to see. What did the Ancient Island look like as waters lapped at the base of Skull Cave, for example, or when they eroded the land between Point Lookout and Sugar Loaf Rock?

My curiosity didn’t end there. Seeing the maps of Lake Algonquin’s reach, I got to wondering about my own home, here in Cheboygan. Did this prehistoric lake have any bearing on where I myself live? I noticed that Mullett Lake, which is not within physical view but is within walking distance of my home, is in fact a remainder of the Nipissing Great Lakes, which were a remainder of Glacial Lake Algonquin. Could that mean that the spot of land we now live on was once a lakebottom? I had read that Cheboygan was long ago part of an archipelago, but it’s a big county, and I wasn’t sure where in it we were.

I plugged in our address at Yahoo! Maps and took screen captures of the results. Our home was placed near the northeast corner of Mullett Lake…right in the basin of the Nipissing Great Lakes, according to one of the topographical maps…a basin which itself must have been part of the basin of Glacial Lake Algonquin. Since Mullett Lake still exists, it seems likely it was once one of the lowest points of these prehistoric lakes. According to a comparison of the Yahoo! map, a topographical lake level map from MSU, and an artistic rendering of a Lake Algonquin “satellite image” from the same site, it looks like our house, surrounded by roads and woods and relatively level land without any water within view, now stands on what was once a glacial lakebottom.

http://www.geo.msu.edu/geogmich/glacial.html

http://www.geo.msu.edu/geogmich/glaciallake_algonq.html

http://www.geo.msu.edu/geogmich/glaciallake_nip.html

http://sitemaker.umich.edu/umbs/files/profileoftheland.htm

http://www.fishweb.com/maps/cheboygan/index.html

http://www.fishweb.com/maps/cheboygan/mullett/index_north.html

So that was what I learned of where I now live, and why I’m now writing this from the bottom of a lake. What other surprising things could we learn about where we live, were we to just look backward far enough?

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