Catoctin is part of the ancient Appalachian Mountains that were formed 250 million years ago.
Most of the rock visible in Catoctin dates from the Precambrian or Cambrian times
(500 million years ago or more) and was formed from a lava flow of molten rock.

The outlines of some metamorphic rocks, mosty Weverton quartzite and Catoctin
Greenstone, make up the main geology. These tough rocks can be easily
viewed at Chimney Rock, Wolf Rock, and Hog Rock in the park.

"In the eastern half of the park at Chimney Rock and Wolf Rock, the
rocks have been metamorphosed into a hard, weather-resistant rock called
quartzite. This area is part of the Weverton Formation. The Weverton Formation,
named for its formation near the town of Weverton, is the main ridge-making formation
in the eastern mountains in Maryland. The formation is composed of quartz cemented
together by a secondary, less developed quartz.”

Source: CATOCTIN MOUNTAIN PARK GEOLOGY