Ohio History Journal

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OVER 200,000,000 years ago coarse sand

and gravel from a slowly eroding moun-

tain range were washed into a shallow sea

that covered what is now south-central

Ohio. During the millions of years that

followed, the huge beds of sand that

formed along the edge of this ocean were

first compressed into solid rock, then were

slowly lifted above the sea level. This rock

formation, the Blackhand Sandstone, forms

the bedrock foundation beneath the Wah-

keena nature preserve in Fairfield County.

Exposed to the erosive forces of wind

and water, this sandstone was gradually

carved into hills and valleys. While this

sculpturing was going on, plants and ani-

mals from adjacent land areas moved into

the newly exposed area. Aquatic species

made their way into the streams that

drained the new-made land. Only those

plants and animals that could get to the

area entered it, and of those, only the few

able to live in this new environment es-

tablished populations there.

In the eons following, some of the early

species died out as the environment slowly

changed. Others were able to move into

the region as conditions became suitable

for their survival. Some of the descen-

dants of the early organisms changed in

such a way that succeeding generations

were able to survive under the new con-

ditions, but as somewhat different forms.

This process of change still continues in

both environment and organisms. Man, a

very recent invader, is having an ever-in-

creasing effect upon the nature and direc-

tion of the change.

During the last million years (only

yesterday, geologically speaking) Ohio and

its neighboring states were invaded by at

least three continental glaciers. These

enormous ice sheets pushed as far south as

Cincinnati in western Ohio, but the high

hills of eastern Ohio held back the ice. A

few glacial lobes projected into the lower

valleys along the edge of the hill country,

and one such icy "finger" apparently ex-

tended down the Hocking River valley to