Geodiversity is the full variety of a park's natural geologic and soil resources and processes — rocks, minerals, sediments, fossils, landforms and the processes that shape them. The NPS Geodiversity Atlas, a product of the Geologic Resources Inventory, supports education, geoconservation, and management of a park's living and non-living parts together. This is its page for Manassas National Battlefield Park (MANA).
The Geologic Resources Inventory report for the park.
The park
MANA lies about 40 km (25 mi) west of Washington, D.C., in Fairfax and Prince William Counties, Virginia. Designated on May 10, 1940, it covers about 2,052 hectares (5,073 acres) and preserves the land of the First and Second Battles of Manassas — also called the First and Second Battles of Bull Run — of the Civil War.
| Battle | Date | What it meant |
|---|---|---|
| First Manassas | July 21, 1861 | one of the first major land battles of the war; a Confederate victory, with sobering losses on both sides. Confederate Brigadier General Thomas J. Jackson rose to prominence here and earned the name "Stonewall" |
| Second Manassas | August 28–30, 1862 | another Union defeat; the war moved from the gates of Richmond to the doorstep of Washington, opening the way for Robert E. Lee's first invasion of the North |
The park keeps the battlefield as it looked during the war: three Civil War–era houses, several post-war historic buildings, a Confederate cemetery, the reconstructed Stone Bridge over Bull Run, about 10 km (6 mi) of historic road traces, and archeological sites, cemeteries, trenches, earthworks, forests and open pasture.
The Stone Bridge over Bull Run.
The rocks beneath the battlefield
- Setting: the park is in the Culpeper Basin of the western Piedmont province — low relief, gently rolling hills and flat fields.
- The basin: one of a series of trough-like depressions that formed by extensional tectonics as the Atlantic Ocean opened, about 200 million years ago. It filled with Triassic and Jurassic sediments of the Newark Supergroup.
- Bedrock: mostly red siltstone, shale (mudstone) and lake clay of the Triassic Groveton Member of the Bull Run Formation.
- The west of the park: Triassic–Jurassic metamorphic rocks cut by diabase dikes and sills. The hot, molten diabase baked the red siltstone into gray hornfels where they met.
- On top: later uplift and erosion left younger low terrace deposits and wide spreads of alluvium.
Differences between these rocks made subtle but important differences in the land, which both battles used for defenses, troop movements and transport routes. The park shares its history and several of its formations with the wider Piedmont Province.
The park's geologic map from the Geologic Resources Inventory.
Maps and reports
The Geologic Resources Inventory makes digital geologic maps and reports for more than 270 natural resource parks:
| Product | What it holds |
|---|---|
| Scoping summaries | records of meetings where NPS staff and local geologists planned the park's mapping and report |
| Digital geologic maps | GIS files, a guide to the data and extra map information; newer ones add Google Earth and online map views |
| Reports | the park's setting, notable features and processes, management issues and geologic history |
| Posters | a PDF view of the map data, newer ones with aerial imagery or shaded relief |
| Projects | the program and every product available for the park |
The park's products are in the NPS DataStore. An NPS Soil Resources Inventory has also been completed for the park and is in the DataStore.
More: Manassas — geologic formations, physiography and hydrology, geology, and the Virginia Division of Geology and Mineral Resources.
Sources
Based on "NPS Geodiversity Atlas—Manassas National Battlefield Park, Virginia," National Park Service, drawing on Southworth and Denenny (2006), Thornberry-Ehrlich (2008) and National Park Service (2014); a work of the United States government in the public domain. The source's "Piedment" is corrected to Piedmont.
In these publicationsManassas National Battlefield Park
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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