40 Acre Rock Vein EarthCache
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FTF Prize: Go to N 34° 40.536 W 080° 31.406 and you will find a ready made cache that you can pick up and take with you. Please say in your log if you grabbed it.
Located in 40 Acre Park. Please be careful when hiking in the area as there are sheer drop offs from the rock in places and areas around 40 Acre Rock and open for hunting.
In geology, a vein is a distinct sheet like body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation.
Veins are classically thought of as being the result of growth of crystals on the walls of planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, and the crystal protruding into open space. This certainly is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock, especially several kilometers below the surface. Thus, there are two main mechanisms considered likely for the formation of veins: open-space filling and crack-seal growth.
Open Space Filling - Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space filling to take effect, the confining pressure is generally considered to be below 0.5 GPa. (measure of force per unit area) Veins formed in this way may exhibit a colloform, agate-like habit, of sequential selvedges of minerals which radiate out from nucleation points on the vein walls and appear to fill up the available open space.
(In layman's terms, think of this as a non-uniform hole in your backyard. You fill the hole with concrete. You have filled the open space.)
Crack-seal veins - When the confining pressure is too great vein formation occurs via crack-seal mechanisms. Crack-seal veins are thought to form quite quickly during deformation by precipitation of minerals within incipient fractures. This happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained; generally the space is in the order of millimeters or micrometers. Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface.
(In layman's terms, think of this as a tile floor. The grout between the tiles would be the vein.)
Here is an example of a crack-seal vein:
Here is an example of an open space filling:
At the posted coordinates you will see a vein.
To log this Earthcache you need to email the following information to my GC profile:
#1 – What is the width (at it's thickest point) of the Vein at the coordinates?
#2 – Which mechanism is most likely to have formed this vein?
#3 - What is the elevation at this vein?
Please email answers through my profile. Thanks!
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Additional Hints
(Decrypt)
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