We are pretty lucky here in Delaware County. This county is picturesque with its colorful mix of conifer and deciduous trees, pastures with sleek horses and well fed cows, meandering rivers and serene lakes, along with productive fields of corn and soybeans. Our county is also scenic in a way that is not obvious to many of us. We have cool things under the ground — rocks.
Rocks are constantly being formed, worn down, and then formed again in a never-ending cycle. Rocks are made up of two or more minerals. A mineral is composed of the same substance throughout and is inorganic, meaning it doesn’t come from a plant or animal. Some common examples are talc, copper, silver, gold, and halite (rock salt). If you recall high school geology, there are three kinds of rocks: sedimentary, metamorphic, and igneous.
Igneous rocks are formed when molten lava cools and turns to solid rock. Sedimentary rocks are formed from the sediments that settle out of streams and rivers when the water slows. Metamorphic rocks were once igneous or sedimentary but have changed due to intense pressure or heat from movement of the earth’s crust.
Delaware County is underlain by sedimentary rock such as sandstone, limestone, and shale. Sandstone is a stone that is made when sand grains cement together. Limestone is made of calcium carbonate and/or microscopic shells and often contains many fossils. Shale is clay that has hardened and turned into rock and often breaks apart in flat pieces. The Olentangy River makes a rough boundary between the limestones of the western portion of the county and the shales and sandstones in the eastern half.
There are so many places to see our local geology. Between Preservation Parks of Delaware County and Columbus and Franklin County Metro Parks, you don’t have to drive too far to see local geology exposed or to find an informative presentation about the secrets under your feet. Check out geology programs and hikes at www.preservationparks.com and www.metroparks.net.
Stream channels and road cuts are two easy ways to see what lies below the surface. Drive east on 36/37 toward Sunbury and you will see Ohio Shale on the east side of Alum Creek Lake. Columbus Limestone can be seen at the junction of Mill Creek and the Scioto River at Bellpoint. The Ohio Statehouse is constructed of this limestone.
If your head is full of rocks, and I mean that in a positive way, download the new free app Rockd. This app taps into databases on geology and fossils while offering users a chance to contribute to geologic knowledge or to look for answers to questions about a particular site.
Use it as a portable, GPS powered field guide and then add what you see through observations and photos. According to the developers, Rockd serves both amateur rock lovers, students, and professional geologists.
The app was created by Shanan Peters, a professor at the University of Wisconsin-Madison, and Patrick McLaughlin, formerly at the Wisconsin Geological and Natural History Survey. For information about our natural resources visit us at www.delawareswcd.org or find us on Facebook.
Bonnie Dailey is Deputy Administrator, Delaware Soil & Water Conservation District.