Ancient Geology of the Bull Run Mountain Natural Area

Bull Run Mountain is part of the complex of isolated monadnocks in the Virginia and Maryland Piedmont. This small outlying mountain was formed when a long synclinal ridge of Cambrian quartzite resisted erosion, while the softer surrounding rocks were eroded down. This resistant quartzite rock, standing almost on edge, forms striking and conspicuous outcroppings along the ridge of Bull Run Mountain.

The illustration "Ancient Lands" reveals the mountain that once was. Stretching from the Bull Run Mountain to Front Royal, Virginia, was a mountain range similar in size to Mt. Everest. The dramatic white quartzite seen from Route 66 is the remaining testimony to a mountain eroded by nature's force over millions of years.