Catalina Gneiss EarthCache
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Difficulty:
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Terrain:
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Size: 
(not chosen)
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As you drive up the Catalina Highway to get to this earthcache, you
will no doubt notice the color-banded rock that is exposed all
along the road. This rock is called gneiss, and it is the most
common rock type in the southern Santa Catalina mountains.
Gneiss is a metamorphic rock, which means that intense heat and
pressure caused minerals in parent rock to recrystallize to form
the gneiss. The gneiss in this area was formed from two different
parent rocks. One parent is the Oracle granite from the Precambrian
age. The other parent is the Wilderness Suite granite from the
Eocene age. The Wilderness Suite granite is unusual in that, in
addition to the minerals that are normally found in granite
(feldspar, mica, and quartz), it also contains crystals of red
garnet.
Between 35 and 20 millions years ago, the earth's crust in this
region was stretched and sheared in a northeast-southwest
direction. This movement introduced intense heat and pressure to
the parent granites, which were buried at that time at a depth of
seven to ten miles.
The heat and pressure deformed the granites. At temperatures of
600°F, the quartz crystals in the granite behaved like hot, soft
plastic, and smeared into long ribbons in the direction of the
crustal stretching. The feldspar crystals, which are more brittle
at that temperature, were crushed and smeared, also in the
direction of the stretching.
The long, aligned streaks of deformed minerals give the gneiss its
unique texture. The light colored bands are considered to be
deformed Wilderness Suite granite, while the dark colored bands are
considered to be deformed Oracle granite.
How To Complete This Earthcache:
Bring a tape measure!
The posted coordinates lead you to a spot in the Santa Catalina
mountains, where you will see some good exposure of the Catalina
gneiss.
To get there, you need to take the Catalina Highway, which is a
paved mountain road that runs north out of Tucson. There is a small
fee ($5 or so) for recreational use. You completing an earthcache
is recreational use.
At mile 4.5, you will reach the pullout for the Molino Canyon
Vista. Plenty of parking is available. You will probably notice the
exposed gneiss as you pull up to park. The elevation here is
somewhere between 4000 and 5000 feet.
Park the vehicle and walk over to the coordinates. There you will
see some very good examples of the gneiss.
Have Fun! Post A Photo Of Yourself.
Sometimes, things become misguided. Earthcaches and geocaches are
supposed to be all about the fun and the experience of the
location, and about performing simple tasks and getting into the
spirit of the earthcache. Try to embrace the original spirit of
this earthcache and use one of the most powerful tools available to
the field scientist - the camera. Try to take a photo of yourself
with the exposed gneiss appearing in the background, and post it
with your find log. A photo used to be listed as a requirement for
this earthcache (prior to 15 May 2011), and as the past logs show,
it was fully supported without any protest or controversy. It is a
simple task that has always been completely reasonable, with
everyone being supportive of it. However today, a photo is not
required, due to the poor administrative practice of levying
control over a small benign detail that affects nothing outside of
the individual earthcache.
For this earthcache, a photo is simply requested, and is in line
with the spirit of this earthcache.
Click here to see a photo example. I don't care about your GPSr
being in the picture.
LOGGING
REQUIREMENTS:
In order to claim this earthcache as a find, you must complete the
following tasks.
Requirement #1 - Measure And Estimate The
Ratio Of The Rock: At the exposure at the coordinates,
using your tape measure, measure the width of the light colored
bands in the gneiss. Measure the width at several spots and
determine the average. Then formulate answers to the following
questions:
a) What is the average width of the light colored bands at this
exposure?
b) You have seen a lot of exposed gneiss in roadcuts, etc. during
your drive to this spot. Do you think that width of the bands in
all the rock in this area is fairly constant and similar? Or is it
widely varied (very wide at some spots and very narrow at
others)?
c) From all the gneiss you have seen here, would you say that there
is more dark colored mineral or light colored mineral in the
gneiss? What would you say is the ratio of light to dark at the
exposure at the coordinates? Do you think this ratio is fairly
constant and similar for all the gneiss in the area, or does it
widely vary?
Requirement #2 - Inspect And
Compare: At the exposure at the coordinates, walk up and
feel the gneiss with your fingers. Touch both the light colored and
dark colored minerals. Get close and inspect both the light colored
and dark colored minerals with your eyes. Answer the following
questions:
a) What does the gneiss feel like? Be descriptive.
b) Can you feel a difference between the light colored mineral and
the dark colored mineral? If so, what difference?
c) With your eyes, what do you see up close in the rock? Different
particles? Different structure? Other than color, do you see a
difference between the two minerals, or do they appear exactly the
same other than color?
Requirement #3 - Email Me Your
Findings: Send me an email. Your email should provide
answers to the questions listed in the paragraphs above. Please be
descriptive. Do not post your answers in your on-line log.
Logs not accompanied by email within a reasonable amount of time
will be deleted per earthcache rules. I don't like doing that. So
please be careful to get done what you need to get done.
You need to complete the requirements. They are not difficult and
are designed so that anyone can fulfill them.
Remember Your Requirements:
Determine Amount And Ratio,
Inspect And Compare, and
Send Your Answers In Email.
And Please Photo Of Yourself If You
Can.
I hope you have fun.
Additional Hints
(No hints available.)