If you've ever looked at the road cuts in our
area, you know that Greene County sits upon layers of limestone and shale.
About 500 million years ago, we used to be at the bottom of a warm,
shallow sea. The geologic plate we are riding on was then south of the Equator
and our limestone was formed through the gradual buildup of billions of tiny
sea creatures that lived in a warm, shallow sea. This all got buried
until millions of years later when the Appalachian mountains began to form,
forcing these rock layers upward.
The local rivers ran northwest, eroding away the
upper layers until the limestone began to peek out here and there. Everything
went along easily for a few more millions of years after that, but just when
it looked like everything was always going to be the same, along came a really
cold winter. Then another ... and another ... until the winters barely
let up and there didn't seem to be any summer. The snow that fell one
winter just lay there all year and never melted. This was about 2 million
years ago.
As you can imagine, in a few years you've got a
pretty fair amount of snow on the ground. Snow when it gets really
thick starts to act a little less like a solid and a little more like
silly putty. In a few more hundreds of years, you can imagine that
the snow has gotten hundreds and hundreds of feet thick. The biggest pile
of ice and snow was in what is now Canada, and we were right in the path
of the ooze. A glacier.
Imagine the Eiffel Tower at King's Island. It’ s about 400 feet
tall, and about 12 or 13 of them end on end would be about a mile high.
That's how thick the snow had gotten. Every winter the front edge of
the glacier moved a few miles closer to our area. And every summer
it melted back a little.
The flow of the Teays River was dammed up by all
this ice and formed Lake Tight, which covered an area nearly as big as Lake
Erie in southern Ohio and parts of West Virginia and Kentucky. When
it became too full, all the backed up water began to flow southwest, forming
the beginnings of the Ohio River.
Meanwhile, the glaciers had bulldozed millions of tons of rock from
the face of Canada, scooped out the basins where the Great Lakes would eventually
puddle, and even bent the crust of the Earth down from the sheer weight of
the snow and ice. Then whatever was making it so cold changed.
The summers began to get warmer, the winters less killer cold, and the ice
that pushed forward in the winter managed to melt back by the end of each
summer.
All those tons and tons of rock had been ground down
to pebbles, sand and small boulders and with the glacier no longer pushing
them south, they had to end up somewhere. Take a look out your window
at the hills and rolling fields around you. That's glacial debris from
Canada. A ridge formed along the edges of a glacier is called a moraine.
The city of Moraine is named for them.
Drive north past Jamestown or Cedarville and you
will notice that the farm country is remarkably flat. A million ton
bulldozer had just scraped across the land. The Teays River was now
buried under many feet of gravel and silt and the great Ohio River was now
flowing South instead of North. This entire cycle took place at least
three times. The first was about 2 million years ago. the second around
200,000 years ago, and the most recent (and last, we hope) was over around
10 or 20,000 years ago.
Here's one explanation of geologic time that helps
to put these things in perspective. Imagine that you are about 50 years
old, and you were born about the time that the first primitive animals swam
in the seas. When you were 20, the world was covered in trees that
formed all the coal in Pennsylvania and Kentucky. Near your 30th birthday,
about 1980, dinosaurs began to roam around. Around 1994, something
fell from the sky, covering the Earth in clouds and dust. Most of the
plants died and the dinosaurs that depended on them became extinct.
In 1995, a few mammals began to appear, and by 1998
there were horses, apes, dogs, and bears. Last June, early humans arrived,
but their lives got tough when the first Ice Age started this March.
The last glacier just melted last night. The Pyramids were assembled
this morning. The “Little Ice Age” from 1200 to 1700 AD happened about
15 minutes ago. Xenia was founded and Ohio became a state about the
time you started reading this, and TV was invented about 3 minutes ago.
We talk today about global warming in relation to
the fossil fuels that we burn in our homes and automobiles. We worry
that we are causing a greenhouse effect and could alter the climate of the
Earth. In my lifetime, I have seen the weather in Xenia change dramatically.
But given the long view of geologic history, I'm not sure that anything we
do can compare with the formidable powers of our planet to change itself.
That doesn't mean we should continue to trash the planet, but sometimes it
helps to put things in perspective. © 2000 Alan
D. King