The Making Of Mountains EarthCache
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This earthcache is placed along the Schkukyll Rail Trail. This is a family friendly walk/bike ride to the area of the earthcache. Our family enjoys earthcaches and all that we learn from them. I hope you find this one enjoyable.
When the earth was younger, about 480 million years ago, this area was covered by a shallow sea. Thick layers of sediment and carbon rock were deposited on the sea floor. Over the millennia, and due to alternating actions of climate change, receding seas, erosion and the shifting of large segments (tectonic plates) of the earth’s crust, the Appalachians were born. During the violent collisions of these moving plates, one plate would wedge itself under the other causing massive upheavals and folding of the earth across great distances. This wedging action is known as subduction.
450 Million Years ago deep ocean rocks are pushed vertical by compressional forces of the earth's crust.
435-405 Million Years ago new horizontal layers are deposited
285-225 Million Years ago the compressional forces of the earth's crust again push the shoreline and stream deposit rocks vertical.
The Principle of Original Horizontality was proposed by the Danish geological pioneer Nicholas Steno (1638-1686). This principle states that layers of sediment are originally deposited horizontally under the action of gravity. The principle is important to the analysis of folded and tilted strata.
From these observations is derived the conclusion that the Earth has not been static and that great forces have been at work over long periods of time, further leading to the conclusions of the science of plate tectonics; that movement and collisions of large plates of the Earth's crust is the cause of folded strata.
As one of Steno's Laws, the Principle of Original Horizontality served well in the nascent days of geological science. However, it is now known that not all sedimentary layers are deposited purely horizontally.
For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by the internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort. This is known as the angle of repose, and a prime example is the surface of sand dunes.
Similarly, sediments may drape over a pre-existing inclined surface: these sediments are usually deposited conformably to the pre-existing surface. Also sedimentary beds may pinch out along strike, implying that slight angles existed during their deposition.
Thus the Principle of Original Horizontality is widely, but not universally, applicable in the study of sedimentology, stratigraphy and structural geology and one should always bear the above caveats in mind before accepting original horizontality as a fact.
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To claim this earthcache you must do the following:
Email me do not post any of the answers on this page (do not use the encrypt either)
Some answers can be found on the placard at GZ.
1. What is the elevation at the location on the path?
2. In your estimation what is the degree is the angle of the mountain in front of you (answer will be 0-90 degrees)
3. What three time periods are talked about in the making of this mountain?
4. In your estimation how high is the mountain in front of you?
OPTIONAL: Please take a picture and post it of you/your group in front of the mountain holding your GPS.
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