This Earthcache is located in Montana at the Lewis & Clark Caverns State Park. For Non-Residents there is a $5.00 entrance fee to the park. For more information about the park click on the “Related Web Page” link near the top of the page.
The four-mile long Jefferson River Canyon was cut into the Tobacco Root Mountains between LaHood Park and Lewis and Clark Caverns State Park relatively recently in geologic time. The canyon exposes rocks that span over a billion years of geologic history. The rocks indicate times when the area was covered by shallow seas in which fine-grained sediment was deposited, and other times when rocks were exposed and eroded. The rocks also record times of volcanic activity and when stresses in the earth caused rocks to contort into folds or break into complex and significant faults. Entering the canyon from the east will take you backward in time. Most of the rocks at the east end of the canyon are sedimentary and volcanic rocks from the age of dinosaurs and younger. Gray cliffs of Madison limestone mark the entrance to the canyon, and from its walls for about a mile and a half to the west. Lewis and Clark Caverns developed in this limestone. A short distance beyond a northward bend in the highway, a steeper canyon is developed in dark-colored rocks of the LaHood Formations that are much older than a billion years. In the outcrops of the LaHood Formation, chunks of lighter-colored rock as much as 100-feet long are apparent within the dark rock of the canyon walls. They are boulders that broke off an ancient cliff produced by a major fault.
To log this Earthcache please send me an email with the text "GC2BZ3D Jefferson River Canyon” on the first line and the answers to the following questions (The answers can be found on the informational sign. Please do not post answers in your log.)
1. What was the high-quality Madison limestone used for in the Butte smelters?
2. What was discovered about a mile and half upstream from the entrance to Lewis and Clark Caverns?
3. What caused the limestone to dissolve along the cracks forming the caves of Lewis and Clark Caverns?
After sending your email go ahead and log this Earthcache as a find. I will only respond if you have incomplete logging requirements. Any logs submitted without completing the additional logging requirements will be DELETED.