You are about to step back ONE BILLION years. As you look up at the flag pole atop an outcropping (nappe) of rock, think about Earth in its early beginnings. These rocks and boulders are part of the Reading Prong stretching from New England and ending here at Mt. Penn. These are Pre-Cambrian rocks dating back ONE BILLION years (1000 mya) some of the oldest rocks in Pennsylvania. Australia may be able to claim older rocks dating back 4.5 BILLION years (4500 mya) the earliest beginnings of Earth. The rocks you will be seeing today are gneissic (from the German verb gneisto meaning to spark this type of rock glitters) and quartzite which is erosion resistant. Both are metamorphic rocks that have been transformed. The original rock is subjected to heat (temperatures > 150-200 degrees Celsius) and pressure (1500 bars = 100,000 Pascal). These rocks were likely formed by the tectonic process where plates collide within orogenic belts (the forces and events leading to the deformation or the Earth’s crust (lithosphere) during mountain building). Ensuing erosion and then deposits of sand were lithified (transformed sediments into stone under heat and pressure) creating the quartzite that is in abundance here. These ancient rocks were folded and thrust during the Taconic event 450 mya. The Reading Prong rocks (a nappe) are moved rocks over a thrust fault from its original position then deposited over carbonate rocks of limestone and dolomite in the valley below. The gneiss and quartzite stand as islands above the softer sedimentary rocks of the Great Valley.
You will take a short walk to the top of the nappe. Pause at the white bench to view the Great Valley below that is the City of Reading. You can see the Blue Mountains and South Mountain to the North and West on a clear day.
From the bench facing the Great Valley turn right and follow the rocky trail to the top of the nappe (stay to the right for an easier walk). At the top of the trail you will see a few large boulders with graffiti. Find the one with pink and black graffiti. (see photo below)
Standing in front of the boulder with graffiti looking at you:
1. What is the main color you observe of this boulder? Not the pink or black of the graffiti.
2. In your own words what does the boulder look like? Large, small, cracked, glittery, dull, etc.
3. In your own words how does the boulder feel? Hard, soft, smooth, rough, etc.?
4. Are there similar rocks nearby?
5. From the above lesson, how many years is 10 mya?
Please email or message me your answers do not put the answers in your log.
Photos are always welcome and this is a great spot for photos.
See if you can spot your neighborhood, the Reading Airport on the far right or the County Service Center tall building in the city. There are many hiking trails on Mt. Penn as well as a visit to the infamous Pagoda.
I hope you enjoyed this view of earth from ONE BILLION years ago (1000 mya).
As an FYI the access roads to this area is closed from dusk to dawn.