Matthiessen's Giant Bath Tub EarthCache
Matthiessen's Giant Bath Tub
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Difficulty:
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Terrain:
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Size: 
(not chosen)
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A Dells area in a flat landscape. Requires desending stairs into the Dells, then more stairs into the bath tub. Difficulty based on number of stairs to climb.
The Dells area of this park was developed in St. Peter Sandstone. St. Peter is relatively pure, fine-grained sandstone made up of rounded grains of quartz. This rock has a soft sugary texture and is easily broken up with the hand. Overlaying this sandstone is Platteville Dolomite, which is made up of dolomite and dolomitic limestone.
During the retreat of the Wisconsinan Glacier that covered this are 75,000 to 10,000 years B.P. (before present time), the Illinois River to the North was cutting through the St. Peter sandstone. To the South, the Vermilion River was cutting through the overlaying Platteville dolomite.
Current waterfalls and rapids in this park are the result of head ward erosion up the small unnamed tributary of the Vermilion River that runs through the park. The head ward erosion of this tributary was controlled by the level of the Vermilion River until this tributary had cut down to the St. Peter sandstone. Because St. Peter sandstone is more resistant to head ward erosion than Platteville Dolomite, waterfalls and cascades developed.
Potholes are formed when strong currents swirl pebbles and stones in eddies at the base of waterfalls and cascades, grinding holes into the sandstone walls. The pebbles and stones are also ground down, and the resulting sand is flushed away by the strong current. The pothole will continue to enlarge as long as fresh pebbles and stones are available and the stream current is strong enough to flush away the sand. The Giant Bath Tub in Matthiessen State Park is such a pothole.
Resource:
Guide to the Geology of Buffalo Rock and Matthiessen State Parks Area, LaSalle County, Illinois. Nelson, R.S., Malone, D.H., Jacobson, R.J., and Frankie, W.T… ISGS Field Trip guidebook 1996C and 1997B, Illinois State Geological Survey: Champaign, IL. 1997.
This Geocache is placed on Illinois Department of Natural Resources managed property with permission. It is the visitor’s responsibility to orient themselves with the policies and rules pertaining to this Department managed site.
For your own safety and for the preservation of natural resources, STAY ON THE MARKED TRAILS.
At Waypoint N. 41° 17. 870 W. 089° 01. 507, the trail will split, and your GPS will tell you to go straight ahead. STAY ON THE TRAIL. You can get where you’re going either way, but it’s easier to the right. Under NO circumstances go straight.
In order to log this cache, email me the answers to the following questions:
1. What is the width of the Giant Bath Tub at its widest?
2. What is the height of the falls nearest you when you are at the botom tof the tub? (Assume the average height of each stair is 7")
3. Determine the overall depth of the Bath Tub. (You can use ither the stair method or your GPS.)
Additional Hints
(No hints available.)
Treasures
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