Castle Rock Earthcache EarthCache
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Castle Rock is a butte overlooking the Rock River. There is a staircase that leads to to top for a scenic view. But it is what makes up that butte that is worth noting.
Please do not wander off the boardwalk/stairs.
I use to explore this area as a child. The butte then had trails and you could wander all over the butte. Due to people damaging the sandstone by carving graffiti and increasing erosion, the state park has built a staircase and viewing area for the butte to ensure preservation of the area.
Over 450 million years ago, a blanket of sand was laid down in shallow seas covering much of what we now know as the United States. This deposit was known as St. Peters Sandstone. Taken from the St. Peters River in Minnesota where its occurrence was first documented. The source of the sand was pre-Cambrian crystals (more than 5000 million years old) together with other early Ordovician sandstones lying to the north of the area known as the Canadian Shield.
As the area gradually depressed to form a basin, sand continued to flow in covering limestone in a vast deposit. During the period of deposition, temporary beaches, sandbars, and sandy flats formed. Wind action and reworking of waves removed the clays, sorted, and rounded the grains. The sands were then covered by deposits of mud, skeletal debris and carbonates. Much later an area in Illinois was folded and subsequently (about 280 millions years ago) uplifted, where it became subject to erosion.
Beginning about 2-3 million years ago at least 2 continental ice sheets further eroded and later buried the St Peters outcrops under variable thickness of glacial till, a heterogeneous mixture of clay and gravel. More recent erosion has removed some of the glacial drift exposing outcrops of St. Peter's Sandstone.
St. Peter's Sandstone formation is very pure, white, quartz sandstone. It is often weakly cemented and will crumble in your hands. If the grains are well rounded and have a frosted look then they probably were blown about by wind.
At Castle Rock, a thin layer of glacial till covers this region and several distinctive plant species, remnants of the native forest and prairie, still exist. In one valley, 27 different types of ferns have been identified. The park is one of the largest significant natural areas in the northern part of Illinois. It also has a large outcrop of St.Peter's Sandstone.
There are only a few places in the state where St. Peter Sandstone comes to the surface, even though it underlies practically the entire state of Illinois. Castle rock is a great example of St. Peter's Sandstone. When you are at the top of the butte you can see the sandstone and how easily it has crumbled under natural occurrences and man-made occurrences.
To log this find……
1.) PLEASE BE CAREFUL GOING UP AND DOWN THE STAIRS
Measure the height of the butte. You can do this by taking a reading with your altimeter at the base of the butte.Next climb the stairs to the top of the butte and read the altimeter on your GPSr. Then subtract that number from the reading you get at the base of the butte from the number at the top of the butte. Or if you don't have an altimeter you can get the measurement by counting the steps up to the top and multiplying by 7.5 (the height of each step), then divide by 12. Do not post the answer here. E-mail me the answer.
2.) Include a photo of yourself and your GPSr at the sign describing Castle Rock which is located at the base of the butte when you log your find.
Failure to comply with all of the above instructions for logging this cache as a find will result in your log being deleted.
Additional Hints
(No hints available.)