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Rock outcroppings offer us a peek at the normally hidden, inner world of our planet. In the Maryland Piedmont good outcrops are few and far between. In Howard County they occur along the major rivers that border the county. Good exposures to the inner workings of the earth can also be found in the quarries at Savage (gabbro), Marriottsville (marble), and Old Ellicott City (granite). Collectively these outcrops provide us with a record of a long history of plate tectonic movements driven by major thermal convection cells deep in the mantle of the earth.

The black gabbro outcrops along the eastern edge of our county are remnants of oceanic (more…)