Places to see Indiana geology Visit the Fossil Beds of the Falls of the Ohio by John P. Roche
	Overview of the fossil beds at Falls of the Ohio State Park. Photo by John Day

Is the cold and snowy winter weather making you yearn for a warm, sunny vacation? Coral beds, amazing sea creatures, and tropical breezes await you. Expensive? Not at all. You just have to use your imagination and a little geologic time travel and you'll be snorkeling in a tropical sea about 15 degrees south of the equator right here in Indiana.

Falls of the Ohio State Park, in Clarksville, Indiana, offers one of the most impressive natural wonders in the world. The eroding action of the Ohio River has exposed a wide bed of limestone that was formed 380 million years ago, in the middle Devonian period. This rock is the remains of the floor of a tropical ocean. The ocean originally existed far to the south, but the shifting of the earth's tectonic plates moved what is presently Indiana north to its present position. This ancient ocean floor contains visible remains of a wide variety of undersea creatures that once lived there. But instead of viewing these fossils as simply dead remnants of the past, we can use them as a stepping stone into a lively ancient world.

On our imaginary snorkeling adventure in Indiana's Devonian sea, trilobites, arthropods that look like huge sowbugs (or pill bugs), abound. They crawl along the sea floor grazing for food, using their eyes to scan for predators. (They were the first animals to possess eyes.) You will see crinoids, stalked creatures that look like plants (hence their nickname "sea lilies"), but which actually are sedentary animals related to starfish. Covering the sea floor, extensive crinoid "flower beds" wave their arms gently in the ocean currents. The crinoids spread their arms out at right angles to the direction of the water current and trap tiny planktonic animals on small tube feet that cover their arms, then they transport the prey to their mouths with hair-like cilia. Large numbers of clam-like creatures called brachiopods litter the sea floor. Swimming sluggishly above the ocean bottom, ancient relatives of the octopus, nautiloids and ammonoids, feed on invertebrates. Fierce-looking armored predatory fish swim above the cephalopods, also looking for food.

The limestone of the sea floor is made up of the remains of the ancient corals. Coral is created by the action of sedentary species of cnidarians. These cnidarians, which include the familiar jellyfishes, are very primitive; they consist of a simple digestive sack with a mouth at one end. A ring of tentacles around a cnidarian's mouth traps tiny prey, and then immobilizes them with poison from stinging cells. In corals, a hard calcium carbonate skeleton is deposited around the digestive sack; it is these protective covers that you will see at the Falls of the Ohio. As you swim through a garden of coral, you will see many species--solitary corals, branching corals, and colonial corals. Horn corals, some of which are almost four feet long, as well as honeycomb coral and pipe organ coral, trap plankton from the passing currents of water. Before your journey to the Devonian fossil beds, make sure to visit the Falls of the Ohio State Park interpretive center. Here you can see a short film explaining the history of the fossil beds and the falls (which when covered by water are not technically falls at all, but rapids). There is also a fascinating series of displays on the history of the fossil creatures here that will further spark your imagination and interest.

The park is open every day, dawn to dusk, and the interpretive center is open Monday through Saturday from 9 a.m. to 5 p.m. and Sunday 1 p.m. to 5 p.m. Visit the Falls of the Ohio State Park web site to learn more. Photo by John Day