Site is open during daylight hours only.
This EarthCache is located at the Seneca Rocks Visitor Center (U.S. Forest Service), Monongahela National Forest, near the base of the Seneca Rocks formation. The Seneca Rocks Visitor Center is open from 9:30 - 5:00 May through October. However, the car park and visitor center observation deck are open to visitors year round. Binoculars will be a helpful tool while completing this Earthcache.
Your task is to answer the following questions:
1. Observe the upper rock face of the mighty pinnacle before you. Describe the color of the rocks and any interesting features you observe.
2. Notice the cracks or joints in the rock layers. How do these contribute to the fin-like shape of the pinnacle?
3. Which term best describes the exposed rock layers and why do you think they are arranged this way?
A) mostly vertical B) mostly horizontal C) tilted at a 45° angle
4. In your log, please post a photo of yourself or a personal item with Seneca Rocks in the background.
You may go ahead and log your find. Please post your photo with your log and send your answers via the message link as soon as possible.
Tuscarora Quartzite
Seneca Rocks is one of the most striking geological features in the Appalachian Mountains. Rising nearly 900 feet above the North Fork of the South Branch of the Potomac River in Pendleton County, this jagged fin of rock is an example of Silurian-age Tuscarora Quartzite, formed over 440 million years ago.
During the Silurian Period (approximately 443–419 million years ago), much of what is now eastern North America was covered by a shallow tropical sea. Rivers carried vast amounts of sand from ancient highlands to the east and deposited them in this sea. Over time, these sands were buried, compacted, and cemented into a hard, erosion-resistant sandstone. This sandstone was later metamorphosed into quartzite due to heat and pressure created from the mountain-building event that occurred when continental plates collided.
Mountain-Building
The Tuscarora Formation, which includes the rock at Seneca Rocks, was transformed during the Paleozoic Era through a series of mountain-building events caused by tectonic collisions. The most significant of these was the Alleghenian Orogeny (about 300–250 million years ago), when the continents of Laurentia (ancient North America) and Gondwana (including Africa) collided to form the supercontinent Pangaea. This immense tectonic pressure tilted, folded, and uplifted the rock layers. Rocks near the Seneca Rocks Visitor Center are upended and rotated 90 degrees to form the west flank of the Wills Mountain Anticline. An anticline occurs when the rock layers are squeezed and bent into an arch-like shape.
Source: Lumen Learning, "Crustal Deformation" (Anticline)
Erosion over millions of years has stripped away the softer surrounding rocks (like shale and limestone), leaving behind the highly resistant Tuscarora Quartzite standing in dramatic relief. The steep, jagged ridges are a result of vertical jointing (natural fractures) in the quartzite, which allowed water and ice to exploit weaknesses and carve the rock into its present pinnacle form.
The elevation of Seneca Rocks varies depending on the specific peak or reference point. The South Peak of Seneca Rocks has an elevation of approximately 2,200 feet (671 meters). The North Peak is reported to be 2,160 feet (658 meters) high. The highest point in the formation, the South Peak, is noted as the tallest summit east of Devils Tower in Wyoming that can only be reached by expert climbers.
Seneca Rocks offers a variety of outdoor activities. It is a popular destination for geologists, rock climbers, and hikers and provides both recreational and scientific interest.
Sources:
appalachianforestnha.org
Stephanie Smith, chesapeakebay.net
therealwv.com
Venable, Norma Jean. "Seneca Rocks and Spruce Knob"
wvencyclopedia.org
Thanks to Park Ranger (and geocacher) Katelyn Frank for her assistance.