This is my primary field of
interest in geology (although I really like most other fields,
too! That's probably why I like Economic Geology so much - it
requires application of all of
other fields of geology combined.).
We toured geologic wonders of
Arizona for our spring break field trip - some of which are naturally
exposed, and some of which required a little digging to reveal.
We started by visiting the Grand
Canyon. A large open pit mine moves around 250,000 tons of rock
each day. It would take humans roughly 125,000 years to dig the
Grand Canyon at that rate! Here, Harley, Shane, and Anthony await
the sunset together.
Sunset Crater is a young (roughly
900 year old) cinder cone volcano in the San Francisco volcanic
field. The volcano is preserved as a national monument with a
nice trail that explores a beautiful a a lava flow.
Wupatki Ruins is the site of an
Ancestral Puebloan (Sinagua/Anasazi) village near Susnet Crater.
The integration of the buildings with the natural landscape is
remarkable. The people who built the village even took advantage
of the circulation of air in caves to provide air conditioning in the
Although hiking is forbidden on
Sunset Crater volcano itself, there are plenty of other cinder cones in
the area on National Forest land. Matt, Jeremy, and Dan here look
out over the broad Arizona landscape from the lip of the crater of one
Barringer Crater (aka Meteor
Crater) is the site of a meteorite impact crater that formed 40,000
years ago when 300,000 ton chunk of iron slammed into the Earth at a
speed of 45,000 miles per hour. The resulting explosion
overturned the sedimentary rock strata in the area and left a mile wide
hole. Standing on the rim of the crater really brings home the
reality of Earth's place in the bigger astronomical scheme of things -
especially when one considers this meteorite was only 50 meters in
diameter and the asteroid that allegedly wiped out the dinosaurs was
10,000 meters across!
Petrified Forest National Park is
extraordinary! Thousands of giant, silicified logs of wood lay
scattered across the desert floor, exhumed from their resting place by
erosion. The details of the wood are preserved right down to the
burrows dug by beetles beneath the bark.
petrified wood from the National Park is strictly forbidden (as it
should be!) The petrified wood deposits extend well beyond the
boundaries of the park onto private land, though, so shops near the
park sell legal petrified wood. Here, the gang poses with
dinosaurs in the parking lot of one of the biggest shops.
Blasted rock in the mine is hauled
to a primary crusher, which breaks rock down into fist-sized
chunks. A semi-autogenous
those chunks of rock down to sand sized particles for separation.
Once the mineral particles are small enough, the sand is mixed with a
frothy solution. The copper sulfide minerals stick to the bubbles
and rise to the surface where they spill over the lip of the vat and
are collected to be sent to the smelter.
Geologists determine the sequence of mineralization events by carefully
studying the veins in the rock. Younger veins crosscut older
veins. By deduction, we can learn how mineralization proceeded to
form the ore deposits that we rely on for all of our metal needs.
This is a photo of a copper mine
viewed from the visitor center. The dark splotches are just the
shadows of the clouds overhead. The mine is much too big to be
captured in one photo. One can see two large shovels and a giant
haul truck near the bottom of the picture. The benches in this
mine are 40 ft high.
More pictures to come soon!