Potomac River and Catoctin Mountain at Point of Rocks, MD - Places of Geologic Significance on Waymarking.com

Near the unincorporated village of Point of Rocks in Maryland and Louden County in Virginia is where the Potomac River slices through the Catoctin Mountain.

The best place to start is at the C&O Canal parking area and boat ramp just south of the U.S. Route 15 Bridge truss bridge over the river. From U.S. 15, turn onto MD Route 28, then turn right a short distance down to the C&O Canal parking area. The C&O Canal National Historic Park is all along the north shore of the Potomac River, where the original C&O Canal used to float freight. This is one of those access points by car. There is a path that takes you along the canal at this stretch. Head north under the bridge to a clearing that shows the railroad. Also, go to the boat ramp to see the river and the gap. There are other locations, too that I did not explore.

The Potomac River is a wide but shallow river here. It is not navigable by large boats. The river runs roughly in a SE-NW direction here, then turns sharply north upstream. The mountain is a large hump both north and south of the river. Running along the edge of the mountain on the northern shore is the CSX Railroad, which has two tracks, the east bound track runs around the mountain while the west bound track runs through a tunnel in the mountain. Traces of the C&O Canal are visible along the railroad.

The geology is relatively complex. The source used is from a school field trip curriculum (link at the end). It covers the entire mid Maryland-Virginia region. The concepts are summarized here - I recommend reading the entire document.

From Catoctin Mountain west is the Appalachian Province. Mountains of this region include Elk Ridge and South Mountain. These are the eroded remnants of a much taller chain of mountains. Between the old mountains (the anticlimes), the valleys gathered sediment. The great mountains were eroded, early in the Cenozoic Era the entire Blue Ridge Mountain area began to lift. The Potomac, which existed already and thus is an antecedent river, started to carve its way through the folding land. Also, the sediments were pressed together, forming quartzite, which is resistant to erosion. Eventually, only the valleys remain, which are the present mountains. Underlying the quartzite is these mountains, is ryolite igneous rock, and the Loudon Formation - which is unusual since it is green in color. Supporting all of this is metabasalt - a formerly igneous rock that has been subjected to heat and pressure over this time. The ground has also slipped, forming faults. Within these areas iron deposits formed. In the region iron was mined and iron furnaces were built to make iron ore into usable iron.

The canal and the railroad used materials from the area to create the bed for the railroad and the walls for the canal.

Sources:

National Park Service (C&O Canal National Historic Park):
(visit link)

College of William and Mary (Department of Geology):
(visit link)

gigapan.com (Exposure of Catoctin Mountain Basalt Metabasin):
(visit link)

Waymark is confirmed to be publicly accessible: yes Access fee (In local currency): .00 Requires a high clearance vehicle to visit.: no Requires 4x4 vehicle to visit.: no Public Transport available: yes Website reference: [Web Link] Parking Coordinates: Not Listed

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Date Logged Log User Rating   07/29/2022 Don.Morfe visited it 07/06/2013 Searcher28 visited it

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