Catoctin Mountain Park's Geology: Flood Basalts on the Blue Ridge's Eastern Edge

Catoctin Mountain Park covers the easternmost ridge of the Blue Ridge Mountains, about 89 km (55 mi) northwest of Washington, D.C., in Frederick County, Maryland. The National Park Service's Geodiversity Atlas — part of its Geologic Resources Inventory — gathers what is known about the park's rocks, minerals, sediments, fossils, landforms, soils and the processes that shape them, for teaching, geoconservation and managing the living and non-living parts of the ecosystem together.

The park

The park offers recreation in the Catoctin Mountains and serves as the setting and buffer for the presidential retreat, Camp David. It is an outstanding example of President Franklin D. Roosevelt's New Deal programs, protecting hardwood forest, historic buildings and camps, and clean streams, with wide views over the Monocacy Valley.

The rocks

Landscape. Rolling hills and narrow ridgetops, cut by steep valleys and ravines, on the eastern slopes of Catoctin Mountain — the eastern limb of the larger Blue Ridge–South Mountain anticlinorium.

Bedrock. Mostly metabasalt and metarhyolite of the Catoctin Formation, from the Neoproterozoic. These metamorphosed volcanic rocks are read as what remains of continental flood basalts that erupted as North America rifted apart and the Iapetus Ocean opened.

Younger rocks. In the southeast of the park lie Cambrian metamorphic rocks of the Chilhowee Group — the Loudoun, Weverton and Harpers formations.

Mountain building. The park and its surroundings show regional-scale deformation and metamorphism from the three major tectonic events that built the Appalachian Mountains: the Taconic, Acadian and Alleghenian orogenies.

Wolf Rock is made of metamorphosed river-deposited sediments of the Weverton Formation (Maryland Heights Member). NPS photo by Gregory Gusse

Maps and inventories

The Geologic Resources Inventory makes digital geologic maps and reports for more than 270 natural resource parks, and Catoctin has its own: a scoping summary of the mapping plan agreed by park staff and local geologists, GIS map data, a report on the park's geologic setting, features, management issues and history, and a poster of the map. A Soil Resources Inventory for the park is also complete. Both are on the NPS DataStore.

Image from the National Park Service's Geodiversity Atlas page for Catoctin Mountain Park

Image from the National Park Service's Geodiversity Atlas page for Catoctin Mountain Park

A safety note

Abandoned mineral lands can be valuable history and habitat, but many are dangerous to visitors and wildlife and harm water, landscapes and other resources. Near them: Stay Out and Stay Alive!

Sources

Based on "NPS Geodiversity Atlas—Catoctin Mountain Park, Maryland," National Park Service; a work of the United States government in the public domain.