From Ohio History Central
File:Doane Rock at Cape Cod National Seashore.jpg|
Doane Rock at Cape Cod National Seashore
Glacial erratics are rocks carried by glaciers from their area of outcrop and deposited when the ice melted. Some erratics are sedimentary rocks displaced by miles from their outcrop but the most notable ones found in Ohio are of igneous and metamorphic rocks carried far south from Canada. Rounded pebbles of these rocks are common in glacial outwash (or gravel in driveways) but some erratics are large boulders that may be several feet in diameter and weigh many tons. Such large erratics are commonly used in landscaping. Small flakes of gold and rare diamonds occasionally found in Ohio’s glacial deposits are erratics carried by ice from Canada.