Just a little east of the small town of Badin, in northeastern
Stanly County, is an archeological dig location known as the
Hardaway Site; and it has been a treasure trove for scholars and
enthusiasts for decades. Stone tools and weapon points by the
thousands have been excavated, and represent one of the most
extensive bodies of Native American stone work in existence. This
EarthCache is not about the archeology of the Site, however; it's
about the stone used to produce these objects. The Hardaway Site
has been referred to as "The Remington Arms Factory of 10,000 BC",
but the raw material for those weapon points and tools came
primarily from one location: The top of Morrow Mountain, about 5
miles away.
To understand why that rock was so suited for
knapping1, we have to understand more about what the
rock is, and for that we have to go back further in time than
thousands of years. In fact, we need to go back somewhere around
530-550 million years ago. What is now much of the eastern piedmont
of North and South Carolina was a volcanic island arc then, much
like Japan or Indonesia, and it was hundreds of miles southeast of
today's location on the east coast of North America.
A volcano in an island arc is fed with molten and semi-molten
rock (magma), from deep within the earth. As the magma rises, the
temperature and pressure surrounding it changes, causing changes in
the chemical makeup of the body. Finally, as the magma nears the
surface, the pressure increases tremendously, as water and other
"volatiles" are released from the magma, but the overhead rock
keeps everything inside the mountain. Eventually, the pressure
becomes so great that the top or side of the mountain explodes, and
the magma is released. The chemical composition of the magma
determines whether the release will be violent or subdued. Think of
the difference between Mount Saint Helens in 1980, and the on-going
burbling of Mauna Loa in Hawaii, respectively. The amount of silica
in the magma is largely the determining factor.
Morrow Mountain's magma had a lot of silica in it, making the
mix very viscous, or "sticky". The greater the viscosity, the
greater the pressure build up, and the greater the resultant
explosive eruption. The magma was just a little less sticky than
pure rhyolite, so the explosions were probably good things to be
far, far away from.
Rhyolite and granite are composed of the same mix of elements
and minerals, but granite forms deep within the mountain after all
eruptions have stopped. Over hundreds of thousands of years, the
body cools, and crystals form from its minerals, creating the
beautiful material for kitchen counter tops and bank building
exteriors common throughout the country.
Rhyolite is usually an extrusive form of the same mineral mix as
granite, but it doesn't look anything like it. [There are three
photos of samples of rocks from Morrow Mountain at the bottom of
this EarthCache listing.] It's a fairly uniform, dark gray to
almost black rock, and you need strong magnification to the see any
crystals. That's because, once very near the surface, or extruded
over it, the magma (now called lava, because it's outside of the
volcano) cools very rapidly. That rapid cooling doesn't allow time
for large crystals to form. And all of this blather brings us to
Morrow Mountain and those Native Americans.
But first, a technical note. There is less silica in the Morrow
Mountain rhyolite, and more iron and magnesium, than found in
"pure" rhyolite, but not so much that the rock would be the
equivalent of dacite. Therefore, it is more proper to refer to the
rock as rhyodacite. Further, during the period when the volcanic
island arc carrying the rocks of Morrow Mountain collided with
ancient North America some 450 million years ago, Morrow Mountain
and the surrounding Uwharrie Mountains were buried under thousands
of feet of rock and dirt, and the rocks within the long-extinct
volcano were lightly changed, or metamorphosed2, which
means that the rock should technically be called "metarhyodacite",
which is more than a mouthful, so we'll stick to "rhyolite" for
this EarthCache discussion.
The chemical and mineral composition of the rock, and the tiny
crystals within it, created a very hard rock that, when knapped,
yielded a conchoid fracture. That's a concave, circular
depression that has very sharp, hard edges.
For thousands of years, Native Americans mined the rhyolite at
the top of the mountain, and carried it to places such as Hardaway,
to work it into tools and weapon points. Over 20 ancient "quarries"
of rhyolite and other rocks have been discovered throughout the
Uwharrie region and other regions further east. Very complicated
geochemical analyses of the tools and points have enabled
scientists to determine where some of the original rock came from.
The vast majority of the work done at Hardaway used Morrow Mountain
rhyolite, even though there were other quarries closer to the Site.
Modern workers have demonstrated the superiority of Morrow
Mountain's rock, compared to other quarry locations.
Now, as you walk around the crest of the mountain, you see no
outcroppings of rhyolite. So where did all of that rock come from,
anyway. You don't see outcroppings because they're all gone; the
quarry was played out. It became easier to get rock from other
locations than to dig into the earth and extricate rhyolite, even
though that other rock might have less quality than Morrow
Mountain's.
From the coordinates, go over the wall and down the trail.
You'll shortly cross a fairly deep gully on a footbridge, and then
come to a junction in the trail. Take the sharp right and walk onto
another footbridge over the same gully. Look closely at the gully's
walls, which are close to 10 feet deep.
Besides dirt, you'll see chips and shards of grayish-blue rock.
Those humble rocks are Morrow Mountain rhyolite, and they are the
residue of the mining operation. Walk carefully over the ground off
the trail, and brush aside the leaves (be careful in this area, as
it is very steep in places, and the leaves are slippery). There are
shards of the rock everywhere. Indeed, it is estimated by Dr. Kevin
Stewart at the University of North Carolina in Chapel Hill that
millions of tons of such debris form the entire top of the
mountain.
Morrow Mountain’s rhyolite is, indeed, a very special rock.
A reminder, Morrow Mountain is in Morrow Mountain State
Park, and the taking of rock samples is prohibited.
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Footnotes:
1. Knap: To break or chip (stone) with sharp blows, as in
shaping flint or obsidian into tools. (Free OnLine Dictionary)
2. Metamorphis: Literally, to change the shape. (FOD and
Wikipedia)
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Logging Requirements:
Send me an e-mail -- not part of your log -- responding to the
following:
1. Make the subject of the e-mail "GC1PT46. Morrow Mountain's
Special Rock"
2. How many people are in your party?
3. Morrow Mountain, as well as the other mountains in the
Uwharries, is called an "inselberg " or "monadnock".
a. What type of mountain do these terms describe?
b. With respect to Morrow Mountain, are the terms applicable?
Why?
4. Post a picture of yourself on the lower footbridge over the
gully. Try to include you, a bridge railing, and the gully.
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References:
Bradley, P. Piedmont Geologist, North Carolina Geological
Survery. Personal communication, 2009.
Daniel Jr., I. R., and Butler, J. R. An Archaeological Survey
and Petrographic Description of Rhyolite Sources in the Uwharrie
Mountains, North Carolina, in Southern Indian Studies, Vol. 45.
1996.
Miller, B. V. Samarium-Neodymium Isotope and Trace-Element
Analysis of Metavolcanic Rocks from the Vicinity of Fort Bragg,
North Carolina: A Pilot Study of Artifact Source Quarry
Discrimination. Isotope Geochemistry Laboratory, University of
North Carolina - Chapel Hill. 2002
Stewart, K. G., and Roberson, M-R. Exploring the Geology of the
Carolinas. University of North Carolina Press, 2007
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