Having a keen interest in Geology I recently had the pleasure of being able to visit several rock outcrops in Tennessee. To those unfamiliar with field geology, a great many outcrops are found in a rather mundane locale: The great mountain cut-throughs made to make room for highways. If you’re very driving along anywhere outside the American Midwest, you will almost certainly see these great rock facades rising up on either side of the road as you whip by. If you take a closer look (and hopefully only if you’re a passenger), you might see the warped and stressed stratigraphy that tell the story of North America’s ancient geologic past.
The Appalachian mountains are old. Best you understand that first. They were created as the ancient plate boundaries beneath them subducted the now-disappeared Iapetus ocean and eventually had a rather powerful collision with what is now Africa. Several hundred million years of mountain building and erosion tends to create a rather dramatic landscape, and in their prime the Appalachians would have resembled the modern Himalayas, a view no doubt lost on the primitive reptiles and amphibians that wandered the earth at that time.
So now that you have a rough background (The mountains are very old), I can try and grant a new perspective on why a souvenir from this roadside expedition struck me as so significant. There is a layer of rock that formed the deepest bowels of the Appalachian mountains, the basement rock of a mountain range that has only recently begun to be exposed, cut out like the bones of the mountain by water, wind, and dynamite. One of the deepest sedimentary layers one can reach without a drill is called the Rome Formation, and it was here I made my find.
What looks to be a wave cast in stone is not entirely inaccurate. What once was sand has been solidified into sandstone, and the ripple pattern of rock tells us where this sand came from: the beach. Now, the beach tends to paint an image in one’s head, and what struck me about it, the importance of the piece, was just how wrong that image was, because this rock had its origins in a beach that was no less than half a billion years old.
Half a billion is one of those numbers humans can’t really conceive of very well, and I can paint a far more vivid image in comparison than I can with numbers.
First I will need for you to imagine a beach. Simple enough.
Now the easy part. Remove the people walking and lying on the sand, remove the people splashing in the water and the noise they generate from shrieking children to chatty adults. Nice isn’t it?
Now remove all of the secondary and tertiary signs of humanity. All the jetliners flying by and the low roar they make. Remove the cars obviously, and the parking lot they’re sitting in, as well as the lightposts, the lifeguard tower, any telephone poles or either signs that humans were here. All this sounds more like a resort than an ancient landscape, doesn’t it? Well hold on to that thought, because it’s about to get stranger.
Now remove the birds. The harping gulls and bellowing cormorants and whooping pelicans. Get rid of all that noise. The birds are old, but they’re Jurassic, and we’re going back much further than that. The beach has become that much quieter, and that much emptier, oh but we’re far from done.
Now our beach is rather quiet. Nothing but the wind blowing through the grasses and the trees. Well, guess what’s going next. All the land plants are gone. From the reeds to the grasses to the trees. At best you could hope for spores among the sand but don’t get your hopes up. There is nothing on the shore for the wind to blow through anymore.
Now we have something of the stark picture of a Cambrian beach. There is no sound and no life anywhere on land. There is nothing to hear and nothing to see save for the sand, the wind, and the water. This piece of rock pulled up along a highway in Tennessee tells a story of a soundless sea, where even the dream of life on land was millions and millions of years away. Before man, before the dinosaurs, before any land animal and even before most vertebrates as we could recognize them there was this beach on the shore of an ocean that no longer exists. A place where there was nothing to be heard or seen but sand, wind, and water.