Out West they call them Mesas. Places where thousands of square miles of land just pops up higher than everything around it. Abruptly! The edge of this geological entity looks for all the world like a giant layer cake sitting on the floor where it has been dropped. The eons lie exposed in cross section to be read like a 100 million year old book. It is usually the same story. Shale, limestone, sandstone, and conglomerate, layered according to the sordid past of our continent.
All kinds of things cause them. Here is the east, our Mesa has trees all over it, or did until humans got here. At one time, even before the mesa formed, the continent was rising up out of the sea that allowed the water creatures, such as diatoms, crinoids, scallops, etc. to make all that limestone for us to blast out of holes, grind up and put on our driveways. Tree ferns covered the emerging land in a super dense 150 foot thick blanket. The first time I saw a tree fern fossil, I thought it was some kind of dinosaur skin. I could see the scales, well delineated in the freshly fractured rock lying in the edge of the creek. Lepidodendron is the scientific name for what I was looking at... "Scaly tree". I like the idea of dinosaur skin but this will do. What does it look like to you?
In Brasil, I saw what's left of tree ferns growing as ornamental plants in people's yards. They were still pretty impressive. The largest one I saw was about 20 feet high. In some places in the world they get up to 50 feet. They have caused all sorts of consternation in today's world by being so prolific millions of years ago in what is called, the Carboniferous age. Today we mine dead sea creatures as limestone and dead tree ferns as...coal. Down at the creek you can pick up black rocks, rounded and smooth like any other well worn creek rock except that they are very light and easily broken. Yes, they will burn, but don't be dumb enough to put one in your campfire more than once. Coal stinks to high heaven. It is a dirty, dirty, fuel.
The edge of the mesa runs through my yard. On maps it is called Walden Ridge which is not the original name, but then Tennessee isn't the original name either. The land at the top of the ridge is called the Cumberland Plateau. It is about 80 miles wide and officially runs from Cumberland gap at the Kentucky border down to Chattanooga. All this appears to have been caused by the tectonic plate that gives us Africa bumping into the tectonic plate holding up North America, way back when. I think that's right, anyway. Somebody can correct me if not, but let's keep moving, shall we?
So there is this cosmic fender bender and the future home of giant land tortoises, giant sloths, mastodons, big bison, little bison, and things that eat things like that, pops up above the Tennessee Valley. All this goes very well until the Siberian tribes canoe across what is left of the Bering straight and walk, eat, and reproduce their way into what is now, my neck of the woods. They proceed to eat all of everything they can catch and kill, wiping out most of the big animals in a matter of five or six thousand years, until the only one left is the little bison. We now call this little beast, the Buffalo. We think of it as a large thing but it isn't really. At one point in my lifetime there were only about thirty of them still alive. The natural balance being what it was at the time, Conservatives had yet to come to power or they would have bid on and eaten the last few, and folks like Ted Turner decided to do what they could to save them from extinction, thank goodness. There's lots of them in some places, but they don't exactly "roam" like the song claims anymore.
Interestingly another relatively large animal does roam around Roane County now. There is at least one Elk here. He needs a girl friend.
OK, back to the mesa- plateau thing. Suddenly after this continental bonk, we have this upthrust land sitting on top of Walden ridge and it's pretty much flat. Looks that way from an airplane even today. Then the rain started. It had to go somewhere, and space being warped in the presence of a large mass like say, the Earth, that meant down hill, however slight that was in some places, there it went nonetheless. Confused at times, the water went where it could with no particular direction in mind. Things happened like Daddy's Creek going one way and just a little bit over Mammy's Creek goes the other. Eons passed and Mammy's creek joined Piney creek, Fall Creek, Basin Creek, Otter Creek, Sandy Creek, and White's Creek and cut the gorge I get to look at while wear my two fingers to nubs trying to type this.
Now picture this: A large flattish geological area drained by a watershed. Warms up in the daytime and cools off as soon as the sun goes down. The air on the plateau cools down too, and guess what? Cool air is denser (heavier) than warm air and it tries to do the same thing the water does, relieve the physical force imbalance caused by the warped space caused by the presence of a large mass which is the planet Earth, or, "Flows down hill" for the simple minded.
So on most nights there is a river of cold air flowing down the gorge. This morning we have a cloud coloring the air river, most folks call it fog, but I can see it flowing and swirling in eddies and currents this morning. The eagles don't seem to like to navigate in this kind of soup so they sit in the tops of the big white pines and warble to each other. Most of the time they make noxious noises like they need some kind of lubrication, but the sound is pleasant to the ear this morning.
Gotta go now.