Ohio's Land Today is Because of What Happened Yesterday
Ohio's land is largely the result of glaciers that pushed down and scoured the land from Canada during previous ice ages, with the last one ended about 10,000 years ago after covering 2/3s of Ohio for about 2 million years with a sheet of ice that was estimated to be about 1 mile thick.
For some reason not known today, the climate began warming. Where Ohio had for 1000s of years been a 3-season climate with no summers, the summers began to warm as did the springs and falls. Glaciers that had covered much of Ohio began melting quickly forming lakes caused by valleys that had been blocked by stone and debris carried by the glaciers. In time the pressure from these valley lakes would be too much for the dams and they would burst causing a sudden rush of billions of gallons of water and ground up debris scoured the land south causing the deep valleys to fill up with debris. Where soft sandstone was near the surface, that stone would be quickly sculpted into dramatic structures that we see today in the Hocking Hills. The glaciers covering Ohio took 1000 of years to completely melt away, but when the giant lakes that formed from their melting broke loose, they completely transformed the land below them in a matter of decades.
Once the ice left the state, Ohio's landscape was comprised of 5 distinct physical regions, each with its own geological profile as well as the plants and animals that live in those areas.
LAKE PLAINS (yellow area on above map)
Once the bottom of a much larger ancient lake known as Lake Maumee, this region is an extremely flat plain
A narrow strip of land along the Lake Erie coast in northeastern Ohio, it broadens significantly west of Cleveland
As water levels rose and fell, sandy beach ridges and dunes formed along the shore
The northwestern area of the region was called the Great Black Swamp - marked by rich, black soils and poor drainage
GLACIATED APPALACHIAN PLATEAU (light green area on above map)
Carved by glaciers and ancient streams, this region is less hilly and lacks the rugged quality of the unglaciated landscape
Following glaciation, many streams reversed their flow, cutting new paths throughout the region
Evidence of the region's glacial past includes bogs, kettle lakes, and a landscape marked by small hills of sand and gravel called "kames"
Today, the area is marked by smaller tracts of forests, ranging from a few acres to hundreds of acres
TILL PLAINS (orange area on above map)
This fertile region located south of the Lake Plains is not as flat and is characterized by gently rolling hills
Most hills are a series of moraines, which are glacier-created mounds of rock and soil that are up to 100 feet high and 6 miles wide
A hilly belt of bedrock in Bellefontaine rises 1,549 feet above sea level - the highest point in the state, called Campbell's Hill
Glaciers created terraces along valley sides and new drainage patterns including today's Ohio River
UNGLACIATED APPALACHIAN PLATEAU (darker green area on above map)
Untouched by glaciers, this southeastern Ohio region features deep valleys, high hills and winding streams
Sandstone, resistant to erosion and common in the region, supports a variety of cliffs, gorges, natural bridges and waterfalls
Although the region has thousands of forested acres, the topography is rough and much of the soil is infertile
A long belt of high hills on the eastern edge, running from Monroe to Columbiana County, divides eastward and westward flowing streams
BLUEGRASS (pink area on above map)
A small, triangular region that reaches up into southern Ohio's Adams County from Kentucky
Flat-topped hills and uplands rimmed by cliffs define the area
Limestone, dolomite and shale bedrock are characteristic of the region and its landscape moves from gentle slopes to steep slopes, depending on erosion
Some uplands are marked by sink holes or depressions that formed in rocks composed mainly of chalk
Previous Ice Ages in Ohio
When scientists begin to look at our geologic past, it quickly becomes apparent that ice is a fluid that disappears when it melts. What scientists look at are the effects of that melting that is then covered over by centuries of flora adding organic matter. As succeeding ice ages come and go, the evidence from previous ice ages may be altered in ways that are not clear. Core samples taken can identify ages with more organic matter in the soil, compared with other layers that doesn't have as much. This provides a scientific means of measuring the ebb and flow of ice, but when we're considering the spans of millions of years, those factors become less accurate.
According to the Smithsonian National Museum of Natural History, there may have been as many as 20 different ice ages that covered Ohio and they happened about every 20,000 years or so. What causes these periodic fluctuations in temperature and moisture can't be identified at this point in time. We do know they are periodic and are a natural variation of our planet.