Diabase Rock
About 200 feet from the spring down the old railroad path is an exposure of diabase rocks on the left side of the hill.
Sandstone Rock
About 225 feet from the spring down the old railroad path is an exposure of sandstone rocks on the right side of the hill. About 245 feet from the spring down the old railroad path is an exposure of sandstone rocks on the left side of the hill.
Contact Point
About 300 feet from the spring down the old railroad path is an exposure of diabase rocks on top in direct contact with sandstone rocks underneath on the left side of the hill. There is a big tree on top of the hill with a sign saying, "Contact point."
Shale Rock
About 465-475 feet from the Contact Point down the old railroad path is an exposure of shale rocks on the right side of the hill. About 485-510 feet from the Contact Point down the old railroad path is an exposure of shale rocks on the left side of the hill.
Geologic History
Most of the rocks in Triassic Park are Triassic in age. The sandstone and shale are Early Triassic (about 245 million years ago) of the Shockton formation. The diabase is Late Triassic, or early Jurassic. The split up of the super-continent, Pangea, the separating of North America from Africa caused rifts to form at St. Peters, PA which allowed magna deep within the earth to flow up to form the diabase we see today. St. Peters lies in the great dinosaur valley that extends from Connecticut to Virginia. Dinosaurs roamed this valley. Dinosaur footprints were founded at the nearby Limerick Nuclear Power Plant during its construction.
John H. Barnes and W. D. Sevon in The Geological Story of Pennsylvania state:
During the Triassic Period, the gradual northward movement of North America carried Pennsylvania across the equator into the northern hemisphere. The climate was subtropical to tropical. Rainfall was seasonal, and much of the year was very dry. In addition to annual wet and dry cycles, long-term wet and dry cycles occurred over tens of thousands of years. The long-term cycles are believed to be related to fluctuations in the amount of solar energy received. Erosion was probably intense at times, and much sediment was carried west or northwest away from Pennsylvania. Sometime in the Late Triassic, possibly about 220 million years ago, the area where Africa and North America were joined together gradually began to separate. Convection currents in the mantle forced the continents apart and created new rock on the ocean floor that developed between them. This process is called seafloor spreading. As the separation of the continents took place, long, fault-bounded troughs, called rift basins, formed parallel to the margins of the continents. One of these rift basins is in southeastern Pennsylvania. All of the basins became sites for the deposition of sediments eroded from adjacent areas. During the wet part of the long climatic cycles, these basins were the sites of large lakes in which sediments were deposited. During the dry part of the cycles, the lakes dried up. The process of seafloor spreading also caused deep-seated magma to approach the surface very early in the Jurassic Period. The magma cooled near the surface as diabase, a dark, hard igneous rock. In Pennsylvania, the Mesozoic sediments and diabase are preserved in the Gettysburg-Newark basin of the Piedmont province. While all of this was happening, the area between North America and Africa widened to become the Atlantic Ocean. The Atlantic is still widening today by about 2 inches per year. Near its center, at the Mid-Atlantic Ridge, magma continues to be brought to the surface, filling the available space between the separating plates with new rock. Read the full story at http://www.dcnr.state.pa.us/topogeo/education/es4.pdf.
Links
French Creek State Park: Also gives the geologic history around St. Peters.
Pottstown Quadrangle: Shows the surface geology of the area around St. Peters.
"Trail of Geology" Park Guides: Pennsylvania's Trail of Geology.
Educational Resources
Most of the files on this page are in Adobe Portable Document Format (PDF).*
Educational Publications
- Rocks and Minerals of Pennsylvania ES 1
- Common Fossils of Pennsylvania ES 2
- The Geology of Pennsylvania's Groundwater ES 3
- The Geological Story of Pennsylvania ES 4
- Geology and the Gettysburg Campaign ES 5
- Pennsylvania and the Ice Age ES 6
- Coal in Pennsylvania ES 7
- Oil and Gas in Pennsylvania ES 8
- Landslides in Pennsylvania ES 9
- Earthquake Hazard in Pennsylvania ES 10
- Sinkholes in Pennsylvania ES 11
- The Nonfuel Mineral Resources of Pennsylvania ES 12
- Environmental Geology for Land-Use Planning EG 2
Page-Sized Maps
Most of the numbered maps listed below are available in classroom quantities.
Contact Jody Zipperer (717) 702–2073 to order copies.
- Geologic Map of Pennsylvania Map 7
- Oil and Gas Fields of Pennsylvania Map 10
- Distribution of Pennsylvania Coals Map 11
- Physiographic Provinces of Pennsylvania Map 13
- Limestone and Dolomite Distribution in Pennsylvania Map 15
- Glacial Deposits of Pennsylvania Map 59
- Earthquake Epicenter Map
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Quarterly Magazine: Pennsylvania Geology
PA Mineral Clubs: http://www.pennminerals.com/clubpage.htm