Potomac Highlands Watershed School

Cacapon River Watershed Readings

Excerpts from

Portrait of a River:

The Ecological Baseline of the Cacapon River

Read the entire document: Portrait of a River: The Ecological Baseline of the Cacapon River (2.5 mb, PDF)


Geologic Origins

Weathered outcrops and boulder-strewn mountainsides of the Cacapon River basin offer clues to a geologic history hundreds of millions of years old.

About 250 to 300 million years ago, Appalachia underwent its last phase of mountain building. Peaks were thrust four to six miles above sea level, then slowly eroded into the rounded shapes we see today.

     This period of mountain building known as the Alleghenian orogeny also left massive folds and fractures in rocks of the Cacapon River basin.

     Today, the area is part of the Ridge and Valley Province. From the air or on a map you can see why: accordion-like folds have forced the Cacapon and other rivers into a series of straight, parallel drainages divided by ridges.

     Most Cacapon rocks are sedimentary made of tiny grains of rock that collected in water and then were compressed and cemented together. The presence of sedimentary rocks and the occasional trilobite fossil tell us that an ocean once covered the basin.

     The oldest rocks in the basin are over 500 million years old. Much younger, however, are some of the landscape features. Only 20,000 years ago huge landslides occurred. Look carefully along the east side of Lost River, just north of the town of Lost River, and you can find the remains of one of these prehistoric landslides. Approximately one million cubic feet of sandstone fell from the hillside and spilled into the valley.

(See "The Geology of the Cacapon River Basin" in the Summer 1992 issue ot Cacapon, the Lab's river journal.)

The Lost River

 A remarkable characteristic of the Cacapon River is that it disappears.

At the Route 55 bridge crossing the Lost River west of Wardensville, you'll find that a once robust river suddenly dries up. At 'The Sinks," you can sometimes hear the water disappear with a reverberating suck.

Where does the water go? It probably flows into cracks in the underlying rock. The area is underlaid with an unusually high amount of carbonated rock", such as limestone. As these rocks were uplifted millions of years ago, they were bent and fractured. Water began flowing through the cracks, dissolving the rock and enlarging the channels.

Today, as a result of this geologic history, the Lost River literally loses its water into the ground. For much of the year, no surface water can be seen for 2.5 miles.

No one knows how much water actually flows underground through the channels versus how much percolates through the riverbed. Whatever the answer, when the river reappears just above Wardensville, it has a new name: Cacapon.