Geology of America's Great Circle/Loop

Geology of America's Great Circle/Loop

Well, that's a mouthful....let me start with a qualifier....yes I'm a geologist (earth scientist), most of what I say comes from my brain cells which are not perfect, I'm an observer not really a political or religious animal. As such, my thoughts, opinions and comments may be misinterpreted by some but rarely is that my intention. My perspective includes millions of years of earth history, geologically speaking which is a mouthful without getting into the size of this universe. Now let's go cure cancer.

1) Great Lakes and Inland Rivers

The North Channel starts this story as the first official part of our Loop. To those that have been there, they understand the beauty of those old rocks wiped clean by the weight of miles of ice over them. Hard rock for sure....old igneous rocks. As I recall, these are part of the Pre Cambrian Shield and represent some of the oldest rocks on earth....maybe an average of 2.5 Billion years old. This is the lower end of the shield which includes Hudson Bay and half of Canada. Anchoring in this area will be the highlight of many Loopers.....blueberries yes! ...mosquitoes yuck!

Those who detour into Lake Superior will also enjoy the splendor of the Canadian Shield along the North Shore and the South Shore including the Keweenaw Peninsula where my daughter was born. This area was known for the first copper boom where they mined native copper (formed before the earth had oxygen?) known as float copper too where the glaciers have knocked off a chunk of pure copper and moved it elsewhere. Locals also find native silver. Billions of pounds of copper have been mined there and when gold was found in the Yukon, many of those Gold Rush miners came from the Keweenaw.

Moving south along Lake Michigan, you will come to the largest deposit of freshwater sand dunes on earth. The western shore of the lake is more of an erosion area than the eastern shore which get's beat up by the prevailing northwesterly. The sand dunes along the eastern shore provide a nice sandy shoreline which moves back in forth with the changes of lake levels which has a range of about 2 feet most years and multiyear changes of about 4 to 5 feet. In the middle of the shoreline is Little Point Sable lighthouse which is the tallest lighthouse on the lake. You can now climb to the top for a spectacular view and some wind in your hair. I have a picture of this lighthouse in our boat to remind me of the view from our old cottage one klick south of that point. The most famous dunes are those of the Great Bear up by Traverse City. By the way, these sands are windblown so they are very fine and "squeak" when you walk on them.

Now, the Great Lakes themselves are a geological wonder. Largest deposit of freshwater in the world, one of every 5 gallons of freshwater is here! Carved out by the glaciers which moved back and forth across this land we live on. Only more recently about 10,000 years ago. How about that perspective compared to the Canadian Shield's 2,500,000,000 and our recorded history of just a couple thousand years. Think about a 2 mile thickness of glacier ice over your head! These are inland seas and can kick up some mean storms and waves too! I have seen foreigners (not from the Midwest) who have had to go to the shore and taste the water because they could not believe it wasn't salty. I've grown up most of my life living next to Ontario, Erie, Superior Huron and now Michigan and maintain a fascination for these waters....go watch them splash over the Niagara Escarpment at the Falls too!

Now we navigate inland moving south through Illinois. These inland rivers offer many spectacular lessons in the geological processes. Erosion and deposition in the fluvial environment. When the ice melts, the earth rebounds and rises. Rainfall and water erosion have produced natural rock outcroppings that make your jaw drop. Natural beauty developed through years of water running off the land and flooding down the river systems. I have taken pictures of these rocks all along the way. From the folded bluff at the top of the Little Tennessee River where you can anchor near the splendor of the Great Smokey Mountains, following the many cliffs at the twists and turns along the river, the White Cliffs along the Tenn. Tom, Chimney Rock was it? along the Mississippi near the whirlpool waters, the grand canyon of the TN south of Chattanooga.....too many sights for these feeble geological eyes! (I have yet to get to the real Grand Canyon...a trip postponed suddenly a few years ago)

About 100 ago Chicago opened a cut into Lake Michigan to help deal with municipal problems. (Insert Asian Carp story.) Ever since there has been a flow of water southward from Lake Michigan. One beautiful sight is these mountains made by man...the Chi town skyline....we enjoyed it at anchor in Chicago harbor and then brushed our hair on the bridges as we went through downtown with our top down. If you can't make the loop trip, take the time and effort to find the Chicago Architectural tour offered by the local Architectural Society...it leaves from the Michigan Avenue Bridge for a spectacular historical architectural river tour....starting the story by wiping the ground clean with the Great Chicago Fire. http://picasaweb.google.com/jimquince/ChicagoLoopPictures?authkey=Gv1sRgCOed9ve73ajfhQE#slideshow/5295567032326091298

Do not limit your geological studies along the Loop to the waterborne sights. There are nearby studies to be found all along the way! We did a few tours into the mountains of Alabama....yes, were surprised too! The tail of the Appalachian Mountains treated us this past summer to Cloudland Canyon, Lookout Mountain Parkway and DeSoto Falls, Little River Canyon, Noccalula Falls, Talladega Scenic Drive and Cheaha State Park, the highest point in Alabama! Amazing what geological processes can do to some old rocks. (These are the old mountains...about 1/2 billion, compared the youngsters, those Rockies at about 100 million years old!!!)

All this water coming down our inland river system of the heartland dumps into the Gulf and brings with it a huge load of sediment. The Mississippi Delta is a geological feature few will really see or understand. A huge natural dumping ground of everything solid that flows downstream. Our trip starts in Chicago, ties into the Illinois River, the Mississippi, turns up the Ohio, chooses the Cumberland, stalls briefly in Land Between the Lakes, then stalls out again on the Tennessee this past summer. What a lovely part of the Loop. We continue down the Tenn. Tom and the Black Warrior to meet Hurricane Ida in Mobile.

....what a trip it's been! The inland rivers have just been left behind by TWINS now as we've entered the Gulf of Mexico, a whole new chapter in our Loop stories. We just completed a 22.5 hour night crossing from Carrabelle to Clearwater. Salt water now licks at our boat....now Florida, the Keys and the Bahamas....2010 here we come!