This is an EarthCache. In order to "find" this cache, you must first visit the site, read the following text , make observations (be a scientist!), and complete the tasks below.
Lone Rock is a large, singular block of dolomite from the Ordovician Period laid down approximately 450 million years ago. During the Ordovician time, Illinois was located at about 25 degrees south latitude and covered by a shallow tropical sea that was teeming with invertebrate animals and algae. Shells of these animals, such as corals, snails, brachiopods, bryozoans, trilobites and other organisms, along with mud accumulated on the sea floor. These sediments over time became thick beds of limestone (calcium carbonate). Later these beds of limestone were buried deeper by more sediments. Once deeply buried, hot groundwater that contained dissolved minerals slowly moved through the limestone altering the rock to dolomite (calcium magnesium carbonate).
About 250 million years ago, the seas receded and a long period of erosion began. The thick deposits above the dolomite of Lone Rock eroded away, exposing these rocks that were once an ancient sea. Erosion continues today. Over time, streams have carved away the surrounding dolomite following the vertical fractures (joints) in the rock, leaving Lone Rock to stand alone. More of the same formation of dolomite is exposed along the southern bluff of Willow Creek.
In order to claim credit for this EarthCache please answer the following from the viewing platform and/or stairs surrounding Lone Rock (no need to go off trail) and send me a message or email with your responses. I'm not looking for perfect answers - just your best effort.
1. Some portions of the Ordovician rock formations in the area contain fossils (including fossilized algae!) and some do not. Do you see any evidence of fossils that lived during the time Lone Rock was laid down?
2. Erosion caused by the stream channels including Willow Creek followed the vertical fractures (joints) in the surrounding bedrock. Do you note any fractures in Lone Rock? Briefly describe what you see.
3. In your own words, describe some of Lone Rock's features.
Feel free to post a photo, but this is not required.
Sources:
Guide to the Geology of Rock Cut State Park and Rockford Area, Winnebago County, Illinois by Wayne T. Frankie Dennis R. Kolata, and Richard C. Berg, 1999.
Geology of Illinois State Parks by Max W. Reams, 2013.
DNR Requirements:
-
Geocache is placed on Department managed property with permission.
-
Do not place the following items in any Geocache: Food items, inappropriate, offensive, or
hazardous materials.
-
It is the visitors responsibility or orient themselves with policies and rules pertaining to this
Department managed site.