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Maryland Geologic Map

Geologic Maps of the 50 United States


Maryland is a small state whose surprising variety of geology encompasses all the major geologic zones of the eastern United States. (more below)
Maryland's rocks

Image courtesy Maryland Geological Survey (fair use policy)

Click the map for a larger version
Maryland's territory stretches from the Atlantic coastal plain on the east, just recently emerged from the sea, to the Allegheny Plateau on the west, the far side of the Appalachian Mountains. In between, going west, are the Piedmont, Blue Ridge, Great Valley, and Valley and Ridge provinces, distinct geologic regions that extend from Alabama to Newfoundland. Parts of the British Isles have these same rocks, because before the Atlantic Ocean opened in the Triassic Period, it and North America were part of one continent.

Chesapeake Bay, the large arm of the sea in eastern Maryland, is a classic drowned river valley and one of the nation's preeminent wetlands. You can learn more detail about Maryland geology at the state geological survey site, where this map is presented in county-sized chunks at full fidelity.

This map was published by the Maryland Geological Survey in 1968. I have produced two versions that include the key to the different rock units, at 1200x850 pixels (500 KB) and 2050x1420 pixels (680 KB), which is 2.5 times as big on your screen as the paper original.

More about Maryland Geology

More Maryland resources on About.com:
About Baltimore
About Washington DC
Maryland Maps
Maryland Geography, State Symbols & Facts
Maryland Campgrounds
Maryland Attractions
Maryland National Parks
Maryland Fishing

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