Yesterday, my wife and I were driving north along Interstate 81, which runs along the Shenandoah Valley in Virginia. The valley runs in a SSE to NNE direction, and is located about mid-way along a line running east (from Iceland) to west (to California)—roughly in the middle of the North American plate. The drive is spectacular in that along the way, whether you look left (west) or right (east), mountainous ridges dominate the landscape, along with picturesque farms, and herds of cattle, and horses. It’s breathtaking. And you have about 300 miles of this beautiful landscape to enjoy.
But the ride is also interesting in that you are in the middle of series of mountains and valleys that were formed a long time ago—long before the Rockies or the Alps. And they were caused by the collision of two plates, just like the Himalaya Mountains, which were caused by the collison of India and Asia. If you look on a map of Virginia (see below), you will find a series valleys and ridges that run parallel to each other. It looks like rocks were squeezed together to form a series of parallel mountains and valleys. The mountains that run through Virginia have maximum peaks of 4,000 – 6,000 feet today, but a long time ago, before the Pangea split, they might have been 10,000 – 14,000 feet high! And interesting to note is that the plate is drifting to the west, very slowly, or about 2.5 cm per year—or about 10 yards since Jamestown was settled in 1607!
Plate tectonics theory suggests that Virginia was in the fast lane during the Paleozoic Era—The collisions created tall mountain ranges in Virginia that were followed by erosion that etched away those mountains and piled up layers of sediments. I should also add that the same mountains and valleys that I was driving in yesterday, extend to the Southeast all the way into Alabama, and I’ve spent alot of time in the valley and ridge province in Georgia, as well as the Blue Ridge Mountains, and yes, the mountains were just as tall in Georgia in the Paleozoic as they were in Virginia.
Tags: Geology, Shenandoah Valley