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Welcome to geology! First of all, you
might be wondering, "What is geology?"
Well geology is the study of rocks! It's
the study of the Earth's surface,
underneath Earth's surface and basically
anywhere where there's rocks. So we have
lunar geologist people that study moon
rocks and we also have geologists that
study rocks from Mars.
Aeolian geologists, right? All of these
different types of geologists are all
studying rocks and there's really only
three basic types of rocks. And do you
happen to know what they are? I'll fill
you in
they are igneous, metamorphic, and
sedimentary. So igneous rocks are formed by molten rock like if you were to take
this chunk of rock here and heat it up
it would melt down into a liquid so that
you could pour it. Sometimes this molten
rock occurs underground and it cools and
it forms giant crystals and this rock
tends to be very hard when it gets
exposed to the surface this often forms
the basis of mountains. We also have
igneous rock that can form on the
surface these are better known to most
folks as volcanoes. That's right
volcanoes erupting out onto the surface
of the earth. And here in western
Colorado we're lucky because we have
both of those types of rocks right
around here. On top of the Grand Mesa we
have igneous rocks that are the remnants
of old lava flows that covered a high
plateau area. And we also have igneous
rocks that can be found deep down in the
gorges of our national conservation
areas that have intruded into old rock,
and they also form the basis of
mountains like the San Juan Mountains
further south of here so we have all
those different types of igneous rock
right here in western Colorado. The
second type of rock is metamorphic rock.
These metamorphic rocks are formed under intense heat and pressure, but not so hot
that the rock starts to melt. This is
sort of an intermediate phase in between
rocks from the surface or rocks
underground that haven't started to melt
and rocks that are melted. They undergo
metamorphosis, hence the name metamorphic
rock. Think about a butterfly! It
undergoes metamorphosis, right? Goes from
a little caterpillar that's inching
along to a beautiful butterfly
flying away; that's metamorphosis.
Metamorphic rocks undergo a transition
that is no less astounding than that of
the caterpillar as they turn solid rock
into completely different chemical
makeups. The elements detach from one
another their bonds break and they
reform into new structures and they can
be twisted and warped, just like you
would bend around a hot piece of plastic
or you can bend around paper or any
other soft malleable substance. These
rocks can get twisted and folded up.
Those dark gorges on the inside of
McInnis Canyons National Conservation
Area in the Black Rocks area or if you
go up into Dominguez-Escalante National
Conservation Area, look at the waterfalls
in there or if you're down in Gunnison
Gorge National Conservation Area in the
deep gorge all of those black rocks are
metamorphic. They formed the basis of a
giant mountain range that existed here
over a billion years ago and this
mountain range was so massive that it
warped and twisted those rocks because
it was so heavy. All that pressure
pushing those rocks. Well most of the
rock types that we have in our landscape
here are our sedimentary rocks. So when
you're looking out at these this
landscape what you'll see oftentimes
most people remark about is how that you
can see all these different layers of
rocks and that's usually a really good
hallmark for sedimentary rocks in a
landscape especially if you're just
looking at it from say an overlook.
Everything is relatively horizontal. You
do see some interesting features out
there that maybe suggest something else
is going on but generally the the rocks
are horizontal and you see different
layers in there. Those layers are
differentiated between themselves
by the color by the fact that
some of them make more slopes instead of cliffs. Indicating different types of
rocks and their ability to resist
weathering. Mostly what you see behind me
is Jurassic in age. That's starting
off with the red rocks down near the
river those- that's called the Entrada
Formation and that is Jurassic in age and
formed and
desert environment not too dissimilar
from the Sahara today. And as you go
upward from there you see a variety of
different other rocks that make a
variety of either cliffs or ledges or
slopes. And the slopes are generally
mud rocks or shales. Those are mixed in
with some sandstone ledges, and those
ledges were formed in river systems.
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