Take a day trip to the Caledonia State Park area
Many folks in this area travel west on the historic U.S. Route 30 through Gettysburg to Chambersburg, stop at Caledonia State Park for a picnic or even a weekend outing. Perhaps those who do not like the traffic situation in the Civil War town will even take Pa. Rte. 234 through Ardentsville and the scenic “Narrows” to arrive at the same destination.
As a child, I remember many trips my family took to Caledonia to camp for a weekend, to swim in the pool or to have a family picnic along the hemlock-covered stream valley. What good times they were, as we were always treated to a game of miniature golf or an ice cream cone at the intersection in Caledonia!
Little did I know at that time in my life that my career would lead me to concentrate on the study of the Earth and local history. I have come to realize that southeastern Pennsylvania is loaded with history, much of which is well-hidden from the eyes of most. Let’s expand upon several of these historic features in the Caledonia State Park area.
I have written before in this space about Caledonia geology, but I will refresh some of your memories. The park and adjacent Michaux State Forest are located within the South Mountain area, a northern extension of the famous Blue Ridge Mountains of Tennessee, North Carolina and Virginia. The oldest rocks in South Mountain, Pa., are volcanic in origin, known as metabasalt and metarhyolite. “Meta” refers to the fact that these rocks have been through several periods of heat and pressure and have changed from their original appearance.
These two volcanic rocks date back to a time about 600 million years ago, when the continents were beginning to split apart from the supercontinent known as Rodinia. The metabasalt was formed on the ocean floor while the metarhyolite came from volcanic activity related to the splitting of the continental crust. South Mountain contains the largest exposure of igneous rocks in Pennsylvania. After Rodinia split apart, the Iapetus Ocean covered this area, forming sedimentary rocks such as limestone, sandstone and conglomerate. Later collisions with other landmass pieces caused metamorphism, which slightly changed these sedimentary rocks. Sandstone, for example, changed into quartzite.
That is Geology 101 about Caledonia State Park.
I believe in giving credit where credit is due. Donna Bromley recently agreed to work with
Jones Geological Services on programs and field trips and accepted a challenge to find the features described below. We had no time to evaluate Donna’s navigational skills or GPS usage, as we were right off onto the mountain to find several hidden treasures.
(With her background in English, Donna is credited with making this blog somewhat interesting.)
Our first adventure took us to an area I had visited a number of times on other
field trips. Carbaugh Run Preservation Area, just off of District Road south of Caledonia State Park, hosts one of the best-preserved, prehistoric quarry sites in the state. Here, starting about 8,500 years ago, prehistoric people began to quarry the metarhyolite for the production of their stone tools. There are few archaeological sites throughout Pennsylvania, eastern Ohio, Delaware, and Maryland that do not contain artifacts composed of metarhyolite. On top of Snaggy Ridge, numerous shallow pits can be seen where this quarrying took place. According to the research conducted here by the Pennsylvania Historical and Museum Commission, the rock was quarried from the top of the ridge, transported down the hill to Carbaugh Run and flintknapped there into the final products (or at least into manageable sizes) for transport.
What brought us here was not the quarry site, but a report of associated rock shelters at the north end of Snaggy Ridge. A rock shelter is a small “cave” created by the tectonic breaking and subsequent weathering of the rock that often creates a small shelter. After traveling to the quarry site, we walked out the top of the ridge about 400 feet to an outcrop of metarhyolite. With the hyolite on Snaggy Ridge dipping to the southeast, the weathering of the rock had produced two small shelters with a western exposure. Not wholly convinced that these were the shelters documented by several earlier writers, we ventured to the northern “nose of the ridge”. Wow, what a huge outcrop of metarhyolite we found, with at least five shelters, several of which were large enough to crawl into and disappear. Donna, being the new person on the block (and also smaller than myself), volunteered to crawl into one and indicated that the shelter extended another 6 feet in. With a little digging the opening section could be dug out, thus increasing the height of the shelter. Erosion had certainly filled in the entrance over the course of history. It can be postulated that prehistoric people used these northern-facing shelters as a temporary place to get out of the weather. You can imagine the possibilities that this bedrock formation provided, and just let your mind speculate about the prehistoric people who once roamed here.
As a reminder, Carbaugh Run Preserve is on the property of Michaux State Forest. Collecting any natural materials, including rocks or artifacts, is prohibited. Forest rangers have been known to visit the site or to be waiting at the parking area when you return to your automobile.
Let’s travel from prehistoric days to a more recent era and subsequent feature.
Again, a gentleman who had been studying South Mountain history for many years told me about this feature. Knowing it best to visit in the winter because of the lack of foliage and underbrush, we set the coordinates in the GPS and off we went in search of the navigational concrete arrow that was used in aviation. No, it isn’t a geological feature, but it is still interesting.
These 60-foot long concrete arrows were developed in 1923 as part of the U.S. Air Mail system. Because pilots in the early 1920s were flying only with a compass, altimeter and a map showing railroad systems, these arrows were developed to allow them to follow routes across the country from San Francisco to New York. A 51-foot beacon tower was placed on top of the arrow. The beacon contained a 1 million-candlepower-light pointing the direction of flight. These beacons could be seen from a distance of 40 miles away and were placed every 10 miles along the route. Two smaller color-coded lights were placed on the arrow flashing a Morse code letter that identified which beacon it was. By around 1925, over 1550 beacons were in place and in use by the Air Mail Service. By the early 1970s, all of the towers were dismantled.
After arriving at an area with the GPS, we conducted an organized search across the hilltop. Amazingly, within 60 feet of our arrival point on the ridge, Donna was standing on a flat slab of concrete covered with moss and two 1-inch reinforcement rods sticking upwards. This was the western side of the arrow as the eastern half was quite weathered and falling apart. Several electrical insulators were also found in the area of the arrow, and we were able to comfortably say that “we found it.” The GPS and Donna’s sharp eyes saved the day. You see, I had trouble keeping my eyes off of the wonderful exposures of quartzite surrounding the arrow.
Our last stop was a landmark still seen by many travelers. Sitting on the northeastern corner of the intersection of Route 30 and Pa. Rte. 233, is the Caledonia Furnace. Thaddeus Stevens and James Paxton originally constructed this, which began operating in 1837. Caledonia Furnace was one of three iron operations within Michaux State Forest. The other two were Pine Grove and Mont Alto furnaces. Thaddeus Stevens overcame a childhood of poverty and prejudice to graduate from Dartmouth College and become a successful lawyer. In later years, he became the father of the public school system in Pennsylvania, a statesman, and a fervent abolitionist. His strong anti-slavery beliefs were a leading cause in the destruction of the furnace in 1863 by the invading Confederate troops heading to Gettysburg, led by Colonial J. A. Early.
The Caledonia Furnace and a forge were later rebuilt by furnace manager John Sweeney and continued in operation until the early 1870s. However, some documentation suggests that the furnace was never rebuilt. In 1927, the Alpine Club reconstructed the furnace stack, on a reduced scale, and the blacksmith shop across the street from the furnace.
Make sure you check out the historic plaques around the furnace. They discuss how iron ore, limestone and charcoal were needed to operate a furnace, water power to operate the waterwheel and manpower to make the products.
If you continue up the stairs and go toward the Thaddeus Stevens Historic Trail, you will discover a wooden platform adjacent to the furnace race. This is where the giant waterwheel, which used the water flow from the stream to work the bellows for the furnace, was situated. As a child, I loved to see the waterfall spilling down toward the road. At the bridge, you have a choice of two trails. The Thaddeus Stevens Historic Trail is a flat trail that takes you out to the furnace dam where the stream’s flow was stopped to regulate the amount of water into the furnace race. Along the hillside, before arriving at the dam, structures reproducing a charcoal hearth are found.
One of the amazing facts about a 19th-century iron furnace is the charcoal
production. It took roughly eight to 10 days to burn an acre of wood from the forest to produce charcoal. A furnace working at normal temperature burned this amount of charcoal in 24 hours. If you would like to see the location of all 4 charcoal hearths during the operational period, continue on the Charcoal Hearth Trail up the hill. The hearths are well marked.
Check out the soil and see how black it is from the charcoal. The Charcoal Hearth Trail continues uphill and completes a 3-mile loop back to the furnace. There are no historic features past the first hearth close to the top of the hill, but have fun walking across
Graefenburg Hill with an elevation of 1522 feet above sea level. Just a note to those who want to try the Charcoal Hearth Trail — it is marked “most difficult” for a reason. The trail climbs nearly straight up for about fifteens before finally leveling off, and on the way down the other side of the loop, be prepared to brake frequently! It is not for the faint of heart, but is well worth the effort.
Obviously, seeing Carbaugh Run, the concrete arrow and Caledonia Furnace will take more than one day, but prioritize your visit and enjoy the trip. Those hills are alive with history and waiting for you to uncover them.