What a Gneiss Cache! EarthCache
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This EarthCache can be found on top of the Whitetop
Mountain. From the parking area, just follow the coordinates for a
pleasant 1 mile hike, but it is up hill on the return. The weather
can change very quickly so be prepared!
At this point, you may be wondering what the heck is that
cache name? I am not a geologist, actually I am far from it and I
didn’t play one on TV! I had to learn a little by various
readings and a little tutoring and an on-line course or two. In my
short ventures into geology, I have found that one of the rarely
seen and one oldest rocks found East of the Mississippi is
Cranberry Gneiss. Gneiss is pronounced as in the word
‘Nice’ which rhymes with ice! In other words, Gneiss is
Nice! Oh well, that enough of the word comparisons but at least you
know where the title came from and better yet, how to correctly
pronounce it!
One of the Rocks
Whole-rock radiometric age determinations were made on
Precambrian basement rocks from the Blue Ridge province of northern
North Carolina and adjacent areas of Tennessee and Virginia (Mount
Rogers Formation). Parts of the Cranberry Gneiss in North Carolina
and the Grayson Gneiss in Virginia have ages of 1,252 ± 45 m.y. and
1,174 ± 14 m.y., respectively. Thus far, these are the oldest rocks
found in the southern Appalachians. Yes, the rocks date back well
over 1 billion years!
You will hike past the Buzzard’s Rock which is
rhyolite and very young as compared to the Cranberry Gneiss. The
Buzzard’s Rock is also much more spectacular in size. The
rhyolite is a young 350 to 400 million years old. The rhyolite is
volcanic as are most of the Whitetop Mountain rocks. Being rhyolite
gives strong evidence to geologists of the ancient volcanoes that
existed from the Mount Rogers Mountain to here at Whitetop. This
stretch of mountains is referred to as the Mount Rogers Chain. The
volcanoes were formed when the mega continent known, as
Pangaea broke apart and the Appalachian Mountains were
thrust upward. During this upward thrust, lava spilled onto the
surface. The “lava” we find here is the rhyolite. These
volcanoes where not necessarily like Mount St. Helens and were
perhaps much more quiet as volcanoes go but they were volcanoes
none-the-less.
Rhyolite
Pangaea
Well beneath most of the external (extrusive) volcanic
activity was internal (intrusive) heat and fire. Out of this heat
and extreme pressures, Cranberry Gneiss was produced. The rhyoite
mentioned earlier, is an example of one of the three main groups of
rocks. It is an igneous rock. The other two are sedimentary and
metamorphic of which Cranberry Gneiss is an example of the latter.
Metamorphic rocks are rocks that have had their physical
characteristics changed by the heat and pressure. In other words,
metamorphic rocks began as almost any other of the igneous and/or
sedimentary rock but were very significantly changed. I am biased,
but Cranberry Gneiss is one of the more pretty examples of
metamorphic rock. It has a red/pink granite appearance. Over the
last several millions of years, the Mountain has eroded to expose
the Cranberry Gneiss, which once lied well beneath the
surface.
Just to keep the record straight, Cranberry Gneiss
didn’t get its name from its color, although it can have
cranberry tones, it got it name from Cranberry, North Carolina
where it was first observed/discovered. The Gneiss can be several
colors. There are very few places where Cranberry Gneiss can be
found and this is one of them.
When you arrive at the Cranberry Gneiss, you will observe
small outcrops that are far different in appearance than the
surrounding rhyolite structures. First, they are smaller and are of
a different color and texture than the rhyolite. Again, think of a
granite look. Most of us have observed pink marble and or granite
tombstones. These rocks would be similar, especially if they were
not in the natural rough state but were polished.
Another Nice Gneiss!
NOTE: in order for you to complete a find for this
EarthCache you must post a photo of you or your GPSr standing
and/or sitting beside or on one of the rocks. The rocks are
different from surrounding stones so we want to be sure you have
found and enjoyed one! Another approach would to lay your GPSr on
one of the rocks and take a close-up photo. The last requirement is
to email answers to the following questions: 1. What is the
height and width of the nearest (to the coordinates) rock?
2. What is the elevation at this point? 3. Within a
radius of 25 feet, how many Cranberry Gneiss outcrops do you
observe? Be sure to answer via email only and do not post the
answers. We sincerely hope you have enjoyed the hunt and
don’t forget other nearby EarthCaches.
P.S. There is a fun traditional cache that you will pass
either going to or coming from the Cranberry Gneiss. Also, don't
forget the Buzzard's Rock. You can't miss it!. Take care and take
care of Mother Nature’s creations.
This Earthcache was approved by the
Geological Society of America
| We have earned GSA's highest level: |
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Additional Hints
(Decrypt)
Ab cvpxvat gur Penaoreevrf!
Treasures
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