The Geology of Ross County

Part 2

• The Bedrock Foundation
• A New Land
• The Ancient Rivers

The Ice Age

As the climate cooled about 2 million years ago, snow built up in the polar regions, creating ice miles thick. Under its own weight the ice sheets began to flow southward, creeping across the land as continental glaciers. At its fastest pace the ice moved a mile a century. Northern plants crept south ahead of the glaciers, and some still live in cooler valleys in the area.

As the glacier crossed rivers, lakes formed. The Teays River created Lake Tight, which covered parts of Ohio, Kentucky and West Virginia, coating the land with lake sediment and floating boulders on icebergs into Kentucky. Some streams broke through divides and cut new channels.

The glacier's weight carved out soft rock, ground it up, and then oozed it out as concrete-like clay, called till. Hard rocks or soft rocks carried a short distance, and even trees, remained intact. Farther north, the Great Lakes were scooped out, but here where the ice was thinner, it barely altered the bedrock hills, even preserving ancient soils.

When the ice began to melt, meltwater washed out clay, sand and gravel like a conveyor belt, creating a hill of gravel called a kame. Where streams flowed through the ice, they left beds of gravel that settled into sinous ridges after the ice disappeared, called eskers. Sediment from the melting glaciers filled the river valleys, creating wide, level outwash terraces.

Wind blew dust up from the bare land and deposited it as loess, which formed the rich foundation for young soils. The dust of limestone rocks from the north fertilized the poorer soil in Ross County, creating better farmland. The ancient forest pushed south by the glaciers gradually retook the land.

Several glaciers over the last million years covered two-thirds of Ohio, leaving sheets of deposits, ridges of hills, valleys coated with lake clay, and reworked rivers.	Named after an early geologist who studied its remains, Lake Tight was the size of Lake Erie and lingered for eons, filling valleys and leaving hilltop islands in southern Ohio, eastern Kentucky, and western West Virginia, until waters found their way out through low divides and replumbed the waterways in the region.

The North Fork of Paint Creek is a waterway completely created by the glaciers. Taking the drainages of a few smaller streams, it flows right across them in a row and then through an old diversionary valley of Paint Creek, slicing a cliff face off the side of 'Hawk Hill' along the way.

The North Fork of Paint Creek cuts into a bank and exposes glacial till beneath layers of outwash gravel and sand. The grey till is hard as concrete when dry and stiffer then pottery clay when soaked. A much younger North Fork spread the outwash across the top of the till as the glacier melted back from the area. (My camera bag with a ruler is on the edge of the creek in the forground for scale.)

Remnants of the Ice Age

The glaciers left some of the most dramatic and fascinating terrain behind, and in that terrain some of the most provacative evidence of their comings and goings.