Gold Mining Operations Earthcache
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in our disclaimer.
As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
This earthcache is located at the Rest Area on I-80 WESTBOUND. It is NOT accessible from I-80 eastbound. This earthcache is handicap accessible.
Logging Requirements:
Send the answers to #1-#5 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1. List the name “GC2623V Gold Mining Operations Earthcache” in the first line of your email. Also, list the number of people in your group.
Location 1:
2. In what year did Federal injunction stop the process described here?
Location 2: N 39 10.746 W 120 51.33.
This is the rock face visible from original spot to the NW of your cords, north of the exit lane for autos to re-access I-80.
3. Describe the color of the rock face in front of you
4. Why do you believe that the mining method described at the information panel in Spot 1 was successful in removing gold from rock faces such as this (think of the weight, hardness, grainularity etc. of the face in front of you!) OR how were people able to separate the gold from the gravel in these rocks?
5. Why is gold concentrated in “veins” rather than spread over an entire area in a “broadcast” distribution (see description).
6. (Now considered optional by GC.com...but if your answers to above questions leave me with questions...the picture sure does help verify the find!) Post a picture of yourself and your GPS with your log at EITHER spot 1 or spot 2. Feel free to be creative. If you are against posting a picture, simply list the DATE the plaque was placed.
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
History:
Hydraulic mining shaped the reddish cliffs along this highway corridor. From the 1850’s until THIS DATE (see logging requirement #2), jets of water were used to break down gold-laden gravel and to wash the material through separating devices called sluices. This practice was halted by Federal injunction. During those thirty-some years, it is estimated that hydraulic mining in the state yielded over $100 million in gold (1850’s value). That is, about 11 million ounces (340 troy) of gold is estimated to have been discovered in the by this mining method alone (this does not count placer “panning” mining, coyoteing, hard rock mining, or other sources), worth over $6.6 billion dollars in today’s money.
Geology:
So how did the gold get concentrated in such immense quantities in California? Well, like many features in California, it’s the fault of our faults! In the ages past, California lay at the bottom of a large sea that extended into what is now Southern Oregon. Volcanoes exploded across the region, depositing lava and minerals (including gold) onto the sea floor. Later, tectonic pressure pushed the sea floor beneath the North American Plate. As the Pacific plate “subducted” (that is moved under the N. American plate) its heated up into large molten masses of magma that was forced upward into what is now the Sierra Nevadas. These “veins” of mineral rich magma (containing quartz and gold) cooled as they rose, forming the rich tendrils that humans so eagerly search for. As you can see, because it was formed by magma, gold is concentrated in “veins” thus making the whole “gold mining” endeavor financially worthwhile.
Geological Impact of Mining:
A byproduct of these extraction methods was that large amounts of gravel, silt, heavy metals, and other pollutants went into streams and rivers. Many areas still bear the scars of hydraulic mining since the resulting exposed earth and downstream gravel deposits are unable to support plant life. The gravel is loose, the soil is “sterilized,” and the new “topsoil” is actually nutriet free rock crumbs from may feet underground, now deposited on top by the “shifting” process of mining. In addition, millions of tons of sediment, silt, metals, and other pollutants were washed down the streams and rivers of California, changing river systems all the way to the Bay. River diversion, flooding, habitat poisoning, and more are all results of these non-eco mining methods.
Congrads to Bykenut for FTF on April 9, 2010.
Resources:
Alt & Hyndman, Roadside Geology of Northern andCentral California. Mountain Press Publishing. Missoula: Montana. 2000.
Information Panel at location
Wikipedia "California Gold Rush: Geology"
Additional Hints
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