The bike trail project area is situated in the Nittany Valley whose bedrock geology consists primarily of sedimentary rock of Ordovician (ca. 450 million years old) and Cambrian (ca. 530 million years old) age. The rock is of marine (oceanic) origin, and many of the formations are composed of the remains of various kinds of shellfish (limestones and dolomites) or of sands and gravels (sandstones, quartzites, and conglomorates). The bike trail project area sits atop two Ordovician formations: the Nittany (primarily dolomite) and the Axeman (primarily limestone). There are several SE to NW oriented faults located beneath and near the project area and the site. Faults are cracks in the sedimentary rock produced by movement of the earth’s crust and deep subterranean pressure. The project area is situated along the edge of a northwest to southeast trending narrow valley. This valley is likely a graben, a geologic term for a valley formed by a pair of parallel faults that produce a subsidence in the bedrock.
This geology has direct and very significant implications for the interpretation of the Hatch site. Without a doubt, the most significant of those implications is the association of the local geologic formations with a mineral known to geologists as goethite. Goethite is formed as hot subterranean water containing dissolved silica infiltrates iron rich formations such as the limestones and dolomites found in the Nittany Valley, through geologic faults. The nodules that precipitate from this hydrothermal reaction are a hydroxide of iron. The nodules that are richest in iron are known as bog iron, a type of iron ore. Goethite ores were used extensively in the 19th century iron industry that flourished in and near modern State College. The nodules that are richest in silica are jasper.
In this part of the Spring Creek Valley, those nodules appear as yellowish chunks of often smooth, even glassy material. The First Pennsylvanians discovered these jasper nodules at least 12,000 years ago, and exploited them until the arrival of the Europeans. The quarries where the nodules were mined from the soil are about a half mile away from the Hatch site, at the other end of the graben valley. The Hatch site is on relatively flat, well drained ground close to a tributary of Spring Creek, an ideal place to encamp and begin the process of converting chunks of jasper into tools.
At the Hatch site, understanding the geology helps us understand the site. While we rarely think about it, local and regional geology plays an equally important role in understanding our own communities today. Many towns and cities in northeastern and southwestern Pennsylvania exist because of their proximity to the roughly 300-million-year-old Pennsylvanian Epoch Anthracite and Bituminous coal deposits of the Middle Atlantic Appalachians. Limestone valleys (karst topography to a geologist) like the Nittany and Cumberland valleys have stable, valuable and reliable streams and very rich high PH soils that produced important agricultural market towns like Bellefonte and Carlisle. Iron-rich sedimentary and metamorphic rock and limestone and dolomite formations produced Pennsylvania’s innumerable 18th, 19th and 20th century iron furnaces and foundries, and the hundreds of communities large and small that grew up around them.
How we use and occupy the land here in Pennsylvania is largely a product of what lies beneath that land: the complicated and durable Appalachian geology beneath our feet. As the former residents of the Hatch site are teaching us, that’s been true for a very long time.