Hickory Run Boulder Field

Geology Field Trip Study Guide

Deep in the heart of Hickory Run State Park in the Pocono Mountains of eastern Pennsylvania lies the largest boulder field in the Appalachians. There is no other formation quite like this, an enormous field of boulders seemingly placed smack in the middle of a forest. How did it get there? Standing at its edge, it is impossible to resist the urge to walk out and explore.

The boulders are exposed and eroded blocks of sandstone broken away from the Catskill Formation, which forms the top layer of rock under the Eastern US mountain and valley region.

The field covers 16 square acres, or roughly 12 football fields. It lies atop an ancient stream bed, and the boulders are piled loosely on top of one another to a depth of 6-8 feet. The boulders vary in size from about 2 feet to 30 feet in length. The field is surrounded by a deep evergreen forest, and the boundary between the forest and field is full of interesting plants and trees, especially mosses, bushes, and ferns.

Hickory Run State Park is 230 miles north of the DC area. By car, it is roughly a 4 hour trip one way, which puts it at the extreme edge of a day trip. Other interesting places to visit along the route are the Gettysburg Civil War Battlefield, and Hershey Park. Eastern Pennsylvania has many state parks and historical attractions, so there is an abundance of lodging, camping, and other accommodations should you want to make a weekend of it.

Allow 1-2 hours to visit the Boulder Field itself. Scrambling from the edge of the field to the center and back will take about an hour if you take it slowly (as you should). Hiking boots are a must, the boulders are loosely piled on top of one another, and there are no paths into the field. There is a risk of a twisted ankle, and you should definitely bring a box of band-aids for the inevitable scraped knees!

How To Get There

Via: Google Maps

Pre-Trip Research

• Hickory Run State Park Wikipedia entry
• Pennsylvania Trail of Geology Guide entry on Boulder Field
• Pennsylvania State Park Boulder Field brochure

Post-Trip Discussion Questions for Students

1. Why are the boulders in the field rectangular in shape? Why are some more angular than others?
2. The boulders are made of sandstone. What is sandstone? How is it formed?
3. Why hasn't the boulder field been filled in with dirt? Why is there soil in the forest surrounding the field, but none in the field itself?
4. How old is the boulder field? How do we know?
5. The boulder field was formed by periglacial processes. Define "periglacial".
6. What other types of landforms were created through glacial processes?
7. Can you think of any examples of man-made boulder fields?