Like many, I am fascinated by fossils - proof positive that earth existed many millions of years ago in very different form.

Ohio, my birth state, was once covered by a shallow sea and is, now, a rich reservoir of the fossilized life that inhabited that ocean in eons past. Today, salt from that sea is mined beneath Lake Erie - one of the world's largest fresh water resources. The mined salt is used to melt ice on winter roads.

On my Ohio farm, I'd often walk the fields after a hard rain, looking for arrowheads - but was more apt to find cone-shaped coral fossils: evidence that what is now fertile Ohio farmland was once a seabed during the Devonian Period - 345- to 395-million years ago!

More ancient life locked in stone can be clearly seen in the foundation of the barn. The natural limestone blocks are infused with marine fossils of all kinds. At my aunt's farm in an adjoining county, my then-9-year-old son picked up a small object half-buried in the clay bank of the Sandusky River. "Is it a walnut?" he wondered.

It was not.

It was a one-inch-long perfectly preserved scallop-shaped marine fossil, a type of brachiopod that, according to the National Audubon Society (www.audubon.org), is widespread in North America during the Middle Ordovician through Upper Silurian period - up to 500-million years ago.

Another type of fossil, the trilobite, is said to be so numerous throughout Ohio that it's been named Ohio's "state fossil."

In Chicago when I was a reporter for WLS-TV, I once did a story on how to recognize stones likely to harbor a fossil (oblong or roundish, often worn smooth from being tossed around in those ancient oceans). To easily reveal the fossil, place the stone in water and let it repeatedly freeze and thaw. The stones, I was told, will eventually split in half, to reveal the fossilized fern, or leaf or fish inside. You can also crack them open with a hammer, but could risk damaging the fossil.

Along Lake Erie there stretches a series of islands and one, in particular, is fertile ground for fossil hunters. Kelley's Island was once extensively quarried to produce limestone gravel for building roads. During quarrying operations, someone happened to notice that the limestone was deeply grooved - and the grooves were full of corals and other fossils. Painstaking careful sweeping released the grooves - in some places many feet deep - from their years of built up debris.

Researchers said the grooves were formed by massive boulders trapped in ice, stuck to the bottom of the Wisconsin Glacier as it slowly ground its way south from Canada through Ohio's shallow sea. Dragged through the lime clay seabed, the boulders dug deep grooves, and the clay later hardened into limestone - now a permanent showcase for fossil marine life many millions of years old. Today, fossil lovers travel near and far to visit the Kelley's Island Glacial Grooves.

Kelley's Island offers early morning fossil hunting in its abandoned limestone quarry. For more information, visit www.kelleysisland.com. For more information on types of fossils, visit the San Diego Natural History Museum website, www.sdnhm.org/kids/fossils/index.htm.