Purcell Knob is a spur of the

Blue Ridge Mountain Blue Ridge Mountain, also known as Blue Mountain, is the colloquial name of the westernmost ridge of the Blue Ridge Mountains in Northern Virginia and the eastern panhandle of West Virginia. The Appalachian Trail traverses the entire length of ...

Loudoun County, Virginia Loudoun County () is in the northern part of the Commonwealth of Virginia in the United States. In 2020, the census returned a population of 420,959, making it Virginia's third-most populous county. The county seat is Leesburg. Loudoun County ...

. The peak is just northeast of the main ridge at

Keyes Gap Keyes Gap or Keyes' Gap is a wind gap in the Blue Ridge Mountain on the border of Loudoun County, Virginia and Jefferson County, West Virginia. The gap is traversed by Virginia State Route 9/ West Virginia Route 9. The Appalachian Trail also c ...

and southeast of the village of Neersville. Purcell Knob is notable for exposure of the sericitic phyllite base of the

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

Loudoun Formation in its antiformal

syncline In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed ...

References

Mountains of Virginia Mountains of Loudoun County, Virginia Blue Ridge Mountains {{LoudounCountyVA-geo-stub