Welcome to Marshall Gold Discovery Park!
This earthcache is located along the South Fork of the American River. The South Fork is 87 miles long, shorter than the North Fork by 1 mile (the Middle Fork is 62 miles long). The South Fork also features the townsite of Coloma, where the gold rush began in California in 1848. Trout fishing and recreational gold panning are popular family activities on the South Fork. The American River eventually connects downstream with the Sacramento River, which continues to eventually empty into the San Francisco Bay, ultimately dumping into the Pacific Ocean.
This river is a narrow river, cutting away at and eroding the granite bedrock through which it runs, turning as it goes. These sharp curves constantly erode the outside bank.
The fastest moving water along a curve is naturally toward the outside bank, and likewise, the inner bank of the curve is home to very low-velocity water flow. The faster water erodes the outside bank and deposits the sediment on the inside. This results in a steeper bank on the outside, and a gradual slope on the inside. The constant erosion and pressure of the fast moving water widens the banks of the river over time.
Rivers can get so curvy over time by erosion that they form oxbow lakes.
An oxbow lake is a lake formed by a river that had bent back and touches itself, creating a more direct route for the river, ultimately cutting off the curve. The curve is now the oxbow lake.
Logging:
1) Name of this Earthcache and the number of people in your group
2) At this point in the stream, are you standing on the inside or outside of a curve?
3) What bank (near or far) is home to the most erosion?
4) Is this point close to creating an oxbow lake?
Sources
- http://www.sjvgeology.org/geology/groundwater/index.html
- http://www.onegeology.org/extra/kids/earthprocesses/meanderingRivers.html
- http://www.geocaching.com/geocache/GC1QN2P_yosemite-valley-river-meander
- http://en.wikipedia.org/wiki/American_River