Chadwick Preserve POI C1 Spy Rock
Introduction
Text-to-speech Audio
Begin you tour by proceeding up and around the start of Mediation Trail for about 25 yards. You will see a large flat rock outcropping on your left. This is Spy Rock. It faces north, and at one time likely provided a view of Ridley Creek upstream and down, the Minquas Trail going east-west. Long time residents who explored Long Point in their youth called it Spionkop.
Images
Spy Rock from Meditation Trail
Spy Rock close up. Note the moss.
Backstory and Context
Text-to-speech Audio
The Dutch likley named Spionkop, their word meaning lookout hill. The most famous Spionkop are in South Africa (Boar War) and Nottinghamshire, England. We don't know whether it was the Minquas or traders who watched out over the valley. The indigenous people were known to set camp in protected locations with good views, such as a ridge, where they would be less susceptible to attack.
Southeastern Pennsylvania is part of the Appalachian Piedmont, mostly gneiss and schist. The age of these rocks is a geological concept that generally indicates the length of time they've been in their current mineralogical state. For metamorphic rocks such as schist and gneiss, age means the approximate length of time since they were transformed by heat and pressure from some other kind of rock — in the case of these, mudstone or shale, which are sedimentary rocks — into their current form.
Recent work by geologists at West Chester University and others indicate that our rock is around 390 million years old. Both are formed at high pressures and temperatures, but gneiss is formed at higher pressures and temperatures than schist. If you look closely, particularly on the next rock scramble below Spy Rock, you can find traces of mica within the layers of gneiss there. Further on, to the right at the top of the last switchback, you will find quartz.
Some of the boulders in Chadwick have veins of white quartz and many of the smaller rocks on the surface throughout the borough are chunks of quartz, ranging in color from white to orange to brown. The orangish color comes from minute amounts of iron in the quartz, which oxidizes when exposed to air and water into rust. If you break the orange quartz rocks, they're usually white or even clear in the middle.
Sources
Metamorphic Rock: Pressure, Heat, Transformation, Britannica.com - science. Accessed September 29th, 2023.
County Rock-Type Maps of PA., PA Department of Conservation & Natural Resources. Accessed September 29th, 2023.
EarthHow Geology, Earth Guideline: A Guide to Earth's Geological History, Dec, 2018