At the turn of the 20th Century, the B&O Railroad ran along the Cassleman River, cutting through and exposing millions of years of geologic history. By the turn of the 21st Century, the railroad was gone and the throughway had been converted to bike trail. Geologists from the Bureau of Topographic and Geologic Survey, the DCNR, the Somerset County Rails to Trails Association and local educators developed a K-12 geology course plan for the 7 miles of trail between Rockwood and Garrett.
From Rails to Trails to Rocks: Student Trail Guide
Accessing the Trail
The objective of this cache is approximately midway between Rockwood and Garret so you can begin from either end. From Somerset, follow the "BicyclePA Route S" signs south on SR3015. At Route 653, turn right if you want to go to Rockwood or left to go to Garrett. The parking area at Rockwood (N39 55.630 W79 9.661) has a water fountain and a portajohn, Garret (N39 51.733 W79 3.812) only has a portajohn. The trail to the cache site is a fine crushed limestone and is quite level. One could easily walk from either parking area to the cache site and back in a matter of hours but a bicycle is recommended, allowing you to get to the cache site in 20 minutes.
Wymps Gap Fossil Quarry - F-GR5 (N39 53.281 W79 7.394)
During the Mississippian Period about 330 Million Years ago Western Pennsylvania was the shore of a shallow sea. The exposed limestone layers are a fairly thin band of fossil bearing rock sandwiched between layers of shale.
Unlike other EarthCaches, feel free to bring a rock hammer and dig for fossils. The Rockwood Borough Water Authority periodically comes through with a backhoe to expose more layers of rocks for easy access by students on geology field trips. The bulk of the fossils seem to be brachiopods but fossil hunters have found crinoids and trilobites.
Common Fossils of Pennsylvania
DCNR Fossil Plates
| To log this find, you need to e-mail the cache owner with the information located on a small tag attached to the back of the wooden post marking the site. |
But wait, there's more!
There are many other posts along the trail, each pointing out another geologic interest.
Pottsville Sandstone Boulders - M-GR1 (N39 52.182 W79 4.082)
The rocks making up these boulders formed about 310 Million years ago during the Pennsylvanian Period. At the time, the Appalachian Mountains were granite monsters, higher than the Himilayas are today. Erosion washed the mountains into the shallow sea that once was here where the granite bonded in the silica-rich waters to form a very strong 200 ft thick layer. 100 Million years later, the Alleghenian orogeny created a new mountain range on the grave of the old. The harder Pottstown survived the weathering much better than the softer surrounding stone. These particular boulders broke free of the layer during the last ice age and from 24,000 to 18,000 years ago had been working their way down the slope.
Missippian Mauch Chunk Formation - K-GR2 (N39 52.276 W79 4.640)
Several hundered feet below the Pottsville Sandstones are thinly layered, olive-grey siltstones, sandstones and limestones, or reddish-brown silty claystones. Something else you will notice is the disappearance of Rhododendrons. These plants flourish in the acidic soils derived from the Allegheny Formation, Pottstown limestones and the upper parts of the Mauch Chunk Formations. But the lower parts of the Mauch Chunk are more alkaline and the Rhododendrons don't do so well here.
Cassleman River Gorge Landslide - L-GR2A (N39 52.500 W79 5.099)
A "colony" of Rhododendron marks the location of an ancient landslide that brought Pottsville Limestone and upper Mauch Chunk Formation down from over 300 feet up the hillside some 10,000 years ago.
Festooned Crossbedding - I-GR3 (N39 52.795 W79 5.603)
The thick grey sandy limestone is known as the Loyalhanna Member of the Mauch Chunk Formation. The ripples are essentially petrified sand dunes and the abrupt changes in directions were caused by weather differences, the wind blowing the waves in another direction, re-aligning the sand beneath the waves.
Anticlinal Axis - H-GR4 (N39 52.700 W79 6.363)
200 Million years ago when North America ran into Africa, what is now the east coast folded up like an accordion, (The Alleghenian orogeny) creating the current generation of the Allegheny Mountains. This point would mark the high point of the Negro Mountain fold along the trail except that Lick Run has eroded away the hundreds of feet of rock to reveal the oldest rock along this section of trail. You'll see that the layers of the Burgoon Sandstone in the creek bed lie horizontally.
Burgoon Sandstone - G - (N39 52.779 W79 6.803)
Another stream bed that has cut down to expose the oldest layers along the trail. While it is difficult to see, it's not as far off the trail to see these stones.
Mauch Chunk Formation - E - (N39 53.357 W79 7.465)
Off the trail is a section of the Mauch Chunk Formation that sits just above the Wymps Gap Limestone layer.
Pottsville Limestone - D-GR6 (N39 54.280 W79 8.459)
The curve of the anticline brings the bed of the Homewood Formation of the Pottsville Limestone and the associated rhododendrons back down to trail level. Fossil Sigillaria, large scaly trees, can be found in the lower layers of this bed.
Gob Pile - C-GR7 (N39 54.735 W79 9.041)
The large pile of dark material is waste rock produced during mining on the Lower Kittanning coal seam.
Penelec Mine #3 - B-GR8 (N39 54.727 W79 9.229)
The rusty-colored stream is polluted mine runoff. AMD or Acid Mine Drainage is caused by water and oxygen reacting with pyrite exposed during the mining process. The acidic content of the water is similar to that of lemon juice.
Lower Kittanning Coal Seam- A-GR9 (N39 54.698 W79 9.475)
Some 300 Million years ago, Pennsylvania was much further south than it is now, almost at the equator. This whole region was a costal-plain delta with peat swamps. These thick layers of peat were covered and compressed into this fairly narrow layer of coal. Even though it was difficult to mine, the Industrial Revolution's appetite for coal pushed miners to work this seam in spaces no higher than that under your desk.