Part of the "City of Rocks Geology"
series
This loop hike is called The Erosion
Tour
This
cache is found along a very nice 2 mile hiking loop,
around which I have placed three Earthcaches. The best
place to park is near campsite 31 and take the Flaming Rock hiking
trail. The entire loop should take about 1.5 hours,
but it is best to stretch it out a little longer because there are
so many interesting things to see. Please stay on established
trails for the entire loop. Resist the urge to follow your
GPSr straight to the next location. Stay on the trail that
takes you in the general direction of the cache. Sometimes it
may seem you are going the wrong direction but the trail will swing
around. All three Earthcaches can be found by staying on
the trail. Try clicking on "view map" on this page and then
click on "Topo". It gives a nice perspective of the area.
Take a reading at your vehicle.
If you do the entire loop you will find these three
caches in order:
1. Flaming Rock Window
2. The Clamshell
3. Building Blocks Jointing
Make your way to the coordinates listed
above and face northwest
to view the
Clamshell.
To get credit for this cache you must do the
following:
1.
Upload a photo taken from the listed coordinates of your
GPSr with the
Clamshell in the
background.
2. Send me the answer to the question “What
are the three main minerals in the City of Rocks
granite.”
Several different types of
weathering and erosion are responsible for the fantastic shapes
found at the City of
Rocks.
Exfoliation in geology is a
weathering process, mainly caused in arid areas by
differential heating and cooling of rock
surfaces.
Intrusive igneous rocks
such as granite are formed deep beneath the earth's surface.
They are under tremendous pressure because of the overlying rock
material. When erosion removes the overlying rock material, these
intrusive rocks are exposed and the pressure on them is released.
The outer parts of the rocks then tend to expand. The expansion
sets up stresses which cause fractures parallel to the rock surface
to form. Over time, sheets of rock break away from the exposed
rocks along the fractures. Pressure release is also known as
"exfoliation" or "sheeting"; these processes result in batholiths
and granite domes, an example of which is the Clamshell.
Continued erosion along weak zones produced the linear ridges
down the rock which gives the Clamshell its remarkable
resemblence to an actual
clamshell.
While
you are here you might want to check out my other City of Rocks
Geology caches.
Good
sources of information for City of Rocks geology are the Visitor
Center in Almo, the official park map, and climbing
guides.
Visit this
website to learn more about the City of
Rocks