Geology lesson

Last Saturday I went to Vicksburg with my design class. We met Robert Poore, in the center of the picture above, a landscape architect, who showed us three sites, two of which were his designs. The other one was this waterfall, which has some geological and historic significance. The solid band that is resisting erosion is Glendon limestone, created during the Pleistocene by millions of sea creatures, much like the Osborne pictures I showed you last week. Until very recently, by geological standards, Mississippi was underwater. Not much water, 30 or 40 feet or so, a shallow sea. When the land emerged, glaciers came and retreated many times, the organic layers created during the intervals were ground to powder, the Missouri and the Missippi Rivers ambled back and forth, and all that resulting silt and dust were blown by the winds across Arkansas and Louisiana to create the Loess bluffs, which run more or less continuously in a band just east of the delta all the way to Tennessee.

The loess bluffs are a very fine, slightly acidic clay, while the Glendon lime layer is coarser and more alkaline. In some places the loess soil is 60 feet deep, in other places the limestone layer is very near the surface. Obviously this has a big impact on what you can do with the land. Loess soil is not stable for building, and most ornamental and crop plants would just as soon not grow in limey soil (but prairie plants have adapted).
The historical significance comes from the fact that the pool at the bottom of the cascade was a source of water long ago. Especially during the battle and siege of Vicksburg, many soldiers on both sides lost their lives at that very spot. As we climbed about on the rocks, Robert Poore said, "if you fall and die, your ghost will join hundreds of Confederate and Union soldiers." This waterfall is within the bounds of the national battlefield park and is not marked, because the park service discourages visitors. We were told that you could reach under just about any rock and find belt buckles and bullets but of course it is forbidden to take anything out, even flowers. Everywhere Robert Poore took us, it was obvious that he had done a lot of research. I came home wondering why anybody would NOT want to be a landscape architect.