Los Vaqueros Concretions Earthcache EarthCache
Los Vaqueros Concretions Earthcache
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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 can be done from the comfort of your car and is thus completely handicap accessible. It is outside the entrance to the Los Vaqueros Watershed Reservoir (and thus no fee). PLEASE pull completely OFF THE ROAD before completing the requirements for this cache.
To get to the cache, you need the NORTH entrance towards the Los Vaqueros Watershed Reservoir (the two roads into the park do NOT intersect). To access the earthcache by car, drive south on Walnut Road, past Vasco Rd. It is about 5 miles from Brentwood to the Earthcache.
Logging Requirements:
Send the answers to #1-#4 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1.List the name “GC2A2P5 Los Vaqueros Concretions Earthcache” in the first line of your email. Also, list the number of people in your group.
2.List the number of concretions visible from the cords.
3.Estimate the DIFFERENCE in diameter between the smallest and largest of the concretions (or “how many times bigger” the largest concretion is)
4.Based on the information in the description and your observations, do you believe these concretions to be HARDER or SOFTER than the surrounding rocks/soil (where they were harvested from). Explain.
5. Post a picture of yourself and your GPS with your log that shows you with the nearby ROAD SIGN in the background. DO NOT show any of the concretions in your picture or your log may be deleted. OR tell me the COLOR of the sign posts on the sign amidst the "cannon balls."
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
Geology:
Concreations are formed by materials such as carbonates (calcite) or amorphous or microcrystalline forms of silicas (chert, flint, jasper). In some cases iron oxide is even present (or the main ingredient).
They are formed when sedimentary rocks, such as siltstone, mudstone, or sandstone are still being formed. One of the aforementioned materials “seep down” into the soil/rock and “coaless” around a “center,” often a fossil or shell and begin to form circular or oblong “blobs” such as the ones you see here. In effect, the mineral acts as a cement, filling in the pores between the sediment grains.
The local material here is mostly a reddish-brown Cenozoic mudstone that is present in several areas as far west as the Mendocino Coast and as far east as the foothills of the Sierras. In this area, it is easily visible in roadcuts and where landslides have left reddish scarring on the otherwise “bulbous” grass-covered hills. If you feel the grain size of the mudstone, your can tell that it is rather dense and if given the right “glue” (in this case the carbonates or silicas) could become “rock hard.” Concretions tend to “weather out” of a hillside or plain thanks to events such as erosion or landslides when the surrounding non-cemented rock/soil is removed leaving them exposed.
They vary in size from mere rounded pebbles that often go unnoticed on a beach, to large impressive bowling balls larger than a person (such as at Theodore Roosevelt National Park in North Dakota). If you wish to ask a ranger, they may be willing to show you other places within the park where concretions can be found.
Resources:
Alt & Hyndman, Roadside Geology of Northern andCentral California. Mountain Press Publishing. Missoula: Montana. 2000.
Wikipedia “Concretions” (visit link)
Park brochure
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Treasures
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