Explore Geology
geology fieldnotes title

Rock Creek


Washington D.C.

cover of park brochure

park geology subheading
Rock Creek in the fall
Rock Creek Park, Washington D.C.

Rock Creek, the fourth oldest national park, was created by Congress on September 27, 1890. The park was originally designed for the preservation “of all timber, animals, or curiosities…and their retention, as nearly as possible.” Previous names for the park include Meridian Hill Park (June 25, 1910), Montrose Park (March 2, 1911), Rock Creek & Potomac Parkway (March 4, 1913), and Dumbarton Oaks Park (December 2, 1940).

Rock Creek Park preserves a Piedmont stream valley in a heavily urbanized area and provides a sanctuary for many rare and unique species. The park is approximately 15 km (9.3 miles) long and up to 1.6 km (1 mile) wide. It extends southward from the Maryland – Washington, D.C., border to the Potomac River along Rock Creek valley.

Rock Creek runs approximately 53 km (33 miles) from its source near Laytonsville, Maryland, in Montgomery County. It connects with the Chesapeake and Ohio (C&O) Canal 0.40 km (0.25 miles) upstream from the Potomac River confluence. The Rock Creek watershed covers approximately 48,960 acres, nearly a quarter of which is located within Washington, D.C. The National Park Service administers 1754 acres of the basin as Rock Creek Park.

Rock Creek Park protects a portion of the upland section of the Piedmont Plateau. This is one of the geologically significant physiographic provinces in the eastern United States. The landscape of the park is comprised of a steep, craggy stream valley and rolling hills. Varied hydrological influences have resulted in a complex environment. These variations and seasonal flooding support a diversity of habitats. Rock Creek cuts through the deformed metamorphic crystalline rocks of the Piedmont Plateau. The park ends at the C&O Canal National Historic Park (NHP) and highlights the link between the Potomac River and American history. The park protects a variety of cultural and natural resources in a heavily developed urban area.

Rock Creek Park lies within the Potomac River watershed. The Potomac River is the second largest contributor to the Chesapeake Bay at 616 km (383 miles) in length. The Potomac watershed stretches across Maryland, Pennsylvania, Virginia, the District of Columbia, and West Virginia. This drainage includes 38,018 square km (14,679 square miles).

A general description follows of several of the different physiographic provinces of the Appalachian Mountains:

Atlantic Coastal Plain Province

The Atlantic Coastal Plain province is primarily flat terrain with elevations ranging from sea level to about 100 m (300 ft) in Maryland. It extends from New York to Mexico. Sediments eroding from the Appalachian highland areas to the west formed the province. The sediments were deposited intermittently in a wedge-shaped sequence of soft sediments during periods of higher sea level over the past 100 million years. The sediments are more than 2438 m (8000 ft) thick at the Atlantic coast. The deposits were reworked by fluctuating sea levels and the continual erosive action of waves along the coastline. The province continues as the submerged Continental Shelf province for another 121 km (75 miles) to the east.

The Coastal Plain province stretches from the Fall Line east to the Chesapeake Bay and Atlantic Ocean. Coastal Plain surface soils are commonly well-drained sandy or sandy-loams. Large streams and rivers in the Coastal Plain province, including the James, York, Rappahannock, and Potomac rivers, continue to transport sediment and to extend the Coastal Plain eastward.

Piedmont Plateau Province

The “Fall Line” or “Fall Zone” marks a transitional zone where the softer, less consolidated sedimentary rock of the Atlantic Coastal Plain to the east intersects the harder, more resilient metamorphic rock to the west, forming an area of ridges and waterfalls and rapids. This zone covers over 27 km (17 miles) of the Potomac River from Little Falls Dam, near Washington D.C., west to Seneca, Maryland. Examples of this transition are present in the Potomac Gorge of the C&O Canal National Historic Park and at Great Falls Park. The Piedmont Plateau physiographic province encompasses the Fall Line westward to the Blue Ridge Mountains.

The eastward-sloping Piedmont Plateau formed through a combination of folding, faulting, metamorphism, uplift, and erosion. The result was a landscape of gently rolling hills in the east starting at 60 m (197 ft) in elevation. The hills become gradually steeper westward toward the western edge of the province where they reach 300 m (984 ft) above sea level. The Piedmont Plateau is composed of hard, crystalline, igneous and metamorphic rocks including schists, phyllites, slates, gneisses, and gabbros. Soils in the Piedmont Plateau are highly weathered and generally well-drained.

A series of Triassic age extensional basins occur within the Piedmont. These basins were formed by normal faults during crustal extension. The faults open basins (graben), and these basins are rapidly filled with roughly horizontal layers of sediment. Examples include the Frederick valley in Maryland and the Culpeper valley of Northern Virginia.

Blue Ridge Province

The Blue Ridge province is located along the eastern edge of the Appalachian Mountains. The highest elevations in the province occur in the Appalachian Mountain system within the Great Smoky Mountains National Park in North Carolina and Tennessee. Precambrian and Paleozoic igneous, sedimentary, and metamorphic rocks were uplifted during several orogenic events to form the steep, rugged terrain.

Resistant Cambrian age quartzites form Blue Ridge, Bull Run Mountain, South Mountain, and Hogback Ridge in Virginia (Nickelsen, 1956). The elongate belt of the Blue Ridge stretches from Georgia to Pennsylvania. South Mountain and Catoctin Mountain, both anticlines, are two examples of the pervasive folding in the Blue Ridge province.

Eroding streams have narrowed the northern section of the Blue Ridge Mountains into a thin band of steep ridges, climbing to heights of approximately 1200 m (3937 ft). The Blue Ridge province is typified by steep terrain covered by thin, shallow soils that cause rapid runoff and low ground water recharge rates.

Valley and Ridge Province

Long, parallel ridges separated by valleys characterize the landscape of the Ridge and Valley physiographic province. The valleys formed where resistant sandstone ridges border more easily eroded shale and carbonate formations. The province contains strongly folded and faulted sedimentary rocks in western Maryland.

Areas dominated by carbonate formations exhibit karst topography. Karst describes landscapes dotted by sinkholes, caves, and caverns. The karstic eastern portion of the Ridge and Valley province is part of the Great Valley (Shenandoah Valley). The Ridge and Valley province connects to the Piedmont Plateau province by streams that cut through the Blue Ridge Mountains.

park maps subheading

The general park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

Two geology photo albums for this park are available and can be found here or here.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

geologic research subheading

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://nature.nps.gov/geology/parks/rocr/index.cfm   I  Email: Webmaster
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