Great Falls Park

This guide to Great Falls Park opens with a question about the ground beneath the overlook, once part of a riverbed far larger than today's Potomac. You'll hear how geologists read the smoothed cobbles on a terrace forty to seventy-five feet above the water, trace the gray Mather Gorge bedrock back to a five-hundred-fifty-million-year-old ocean floor, and follow how ice-age meltwater found a hidden fault line running the length of the gorge. Look for the potholes drilled into the rock along the River Trail.