Plotting continental divides on a map can produce some interesting patterns. Here’s a web page John pointed me to that considers the Gulf/Atlantic divide and the drainage divides across Georgia. Note the many parallel linear drainages across the piedmont and coastal plain, I’m guessing because of the longevity of this pattern.
If you’re in the mood to wander the web, you might also be interested in this blog that looks at GIS, geospatial technology, and, okay, I admit it, their intersection with archaeology. The blogger, Matt, posted a link to this nifty site with images constructed of the last 550 million years of North America’s surface geography, like the one above. This is roughly the period when humans arrived in North America, and we’re hip deep in arguments about whether they took sea routes or arrived via a proposed ice-free corridor along the Rockies. Of course, some recent publications have argued for a Pacific Coastal route that was less blocked by ice than shown here and there was no ice-free corridor. Stay tuned to the relevant journals, as this discussion will likely continue over innumerable beers. However, if another golden oldies bunch is right, a wave of hardy vagrants, whose descendents may or may not survived to meet later waves of immigrants, arrived 50,000 to 70,000 years ago, and that would have been earlier than this image.