Hello everyone this is Paul Cutlip I'm
one of the professors for earth science
and we're going to be doing something a
little bit different today, we're,
going to be going on a virtual field trip. So I am
down here in South Charlotte near the
town of Matthews and I'm gonna be
driving east and north to a place called
Morrow Mountain State Park. It is
extraordinary in that it is an ancient
volcanic mountain range right here in
North Carolina. If we look at what was
going on when these rocks initially
formed between five and six hundred
million years ago (I've dropped a pin on
our field site today) but you can see
that the southern United States was
riding along on a tectonic plate that
included Africa and Europe. It would not
be until Pangaea came together that this
slab of crust would be pasted onto North
America and then when North America, when
Pangaea rather, broke apart of course
this went with the rest of North America.
And so but that is a long way off, So for
now though this is an ocean-continent
convergent plate boundary. Not unlike
the Pacific Northwest of North America
where you have the little Juan de
Fuca plate here getting pushed
underneath North America, melting, magma
rising and making the volcanoes of our
Cascade Range. And so that's what was
going on you know in North Carolina
between five and six hundred million
years ago. So if we look at the USGS topo
maps for that area (takes a minute to
come up there we are) we can see now once
we get out there we can see these hills.
Let me know do a version of this I can
draw on. So we can see, you know, here's a
hill that's an ancient volcano right, you
know, here we go, you know. All of this is
this kind of ground down ancient volcano.
Now when we get out there it doesn't
look like volcanoes, they look like big
tree covered Hills. They don't
really look like volcanoes but that is,
that is, what they are. Now we're going to
be going up here. And don't you just hate
it when your
field area is in between two maps? But
let me show you a trick here. If we go
back to the USGS topo and we go down,
let's go down a bit, might take it a
second here to fill in but that's
alright. we're going to go, we want
actually off the map down here.
And there we go. So we've got a handy
little drawing down here that shows us
our map in the middle and it shows us
the maps there are around us, and
sure enough, directly to the north is the
Baden quadrangle and well there it is. So,
and so we're gonna come up here in
between fall mountain and Hathaway
mountain (let me go back to a version I
can draw on) we're going to park right
about there at that, where that 400 foot
contour is labeled. We'll walk down
around this river, we're gonna look at
some rocks and we're going to turn, we're
gonna follow the river and eventually
we're gonna make our way back up here
into the parking lot. and so that's the
plan. We want to go out we want to have a
look at these rocks from this ancient
volcanic mountain range. And so next time
I see you I will be in the field okay?
I'll see you in just a second.
Hey everyone so we're here. You can see
behind me we've got a really pretty
old-growth forest built on soil that's
been built over literally hundreds of
millions of years on top of the rock
from these ancient volcanoes. You also
see there's a lot of there's a lot of
dead trees behind me. Storms, there have been a
few storms come through and taken out
some trees. They wisely just left them
there, there's no reason to take them out
because as they decompose they will
return nutrients to the soil. Forest
ecologists call this big dead wood and
it's, it's a thing. So what we're gonna do
is I'm gonna actually go over and show you
something in the parking lot of all
things. And then we will move on and we
will have a look at a building, and then
we'll get down to some some rock in the
field. So next time you see me I'm gonna
be showing you something in the parking
lot okay.
So one of the things that we do as
geologists when we go into a new area is
just have a look at the rocks that
they're using. Have a look at the rocks
they're using to build with and whatnot. And I'm just here in the parking lot and
this is a rock that they're using to
edge the parking lot just the grass and
we can see that it's kind of interesting
looking
it's tending to break flat and it's got
this very distinctive layering in it. And
in particular if we pick up a piece of
it right here (and I swear I didn't break
that off or anything it was just sitting
there) but we can see that, you know, it's
wanting to break very very flat. And I
don't know if this is coming through on
the video or not but there's some really
interesting kind of shiny stuff going on
on the surface. And you know when we see
rock that it is doing this kind of
layered thing, we start thinking one or
two things, either
it's a fine-grained sedimentary rock,
something like a shale. Or maybe that's
foliation and it's a metamorphic rock.
Now notice that neither of those options
is really igneous, and yet we're in an
area that was volcanic hundreds of
millions of years. Ago in fact from the
parking lot if I turn and we look up
here we can see a pretty substantial
hill there. That is one of these, you know,
remnant ancient volcanoes. And yet this
rock is not volcanic. That is not
volcanic rock. At this point we can kind
of narrow it down to either sedimentary
or metamorphic. So we'll narrow it down a little bit more later.
I should stop moving it because it goes out of focus.
Ok, So I'm gonna show you a building, and then we're going to head down and find some rock in the wild.
Ok, let me throw this down and next time you see me I'll
be at a building.
Hey everyone,so here we are this is just a little
utility building out here at the at the
park. This park is interesting, during
the the 1930s the works progress
administration came out and did a bunch
of building just to give people jobs and
so um you have here (I'll show you this
old-growth forest while I'm talking a
bit here if you can see it through the
shadows) But anyway, it has a lot of
infrastructure, there's a pool out here
there's buildings, there's all kinds of
stuff. So like I said one of the best
strategies when you're doing this kind
of work, we're out in the field, maybe in
a new area is look at the rock that
they're using to do their construction
with. Now, don't go looking at fancy
buildings, you don't need to be looking
at someone's fancy imported marble, you
know their Italian marble or something
like that. Just look at the normal
buildings right? And we see the same
thing we saw in the parking lot, we see
this this rock with this kind of layered
structure, and we also see that it's
either being quarried along very flat
surfaces or it's just breaking along
flat surfaces. And we can see here that
we've got some some, a little bit of what
we would call concoidal fracture where it's
tending, if it's not breaking along here,
if it's breaking in another direction,
it's breaking in these curves. So that's
kind of interesting and is giving us a
little more of a clue as to what we
might be dealing with here. So you know
whenever you see a bunch of buildings
made of the same stone, what geologists
really want to do is go find the stone.
So let's see if we can find this rock in
the field.
I've been here before I know where the rock is let's go check it out.
Okay so I am about a hundred meters from that building and I've hiked down into a
stream bed. Geologists, we love our stream
beds. You can really only learn so much
walking along the quote-unquote surface.
If you can find a place that's cut down
through the rock, be it a stream bed, or a
road cut, or a railroad cut, or anything
like that, you get a much better idea
about what's going on. You can see here
that now in the natural world we have
the same kind of rock that's tending to
break very very flat. And then of course
the nice thing about stream beds
is they wash all kinds of rock. I'll go
upstream here give you a look at it,
there's all kinds of rock up there, and
then we can come past our flat breaking
rock here. And then there's what the
trail ahead of me looks like, just
crossing back and forth over this stream
bed. But you can also see, and I'll just
walk up to it and give you a little bit
better look, you can also see here where
we have a lot of rock broken off. Rock
obviously washes downstream. So when we look at an area like this with this
broken off rock that we call float, just
within this one area it gives us a
pretty good idea about what's going on.
We know all that rock had to wash
downstream, so it started upstream and so
without necessarily needing to move
around a lot you can get an idea about
what's going on. Now I only see two or
three different kinds of rocks in there,
so whatever is going on here is
pretty consistent from place to place.
But if I look right up here you can see
what practically looks like a wall it
looks like it was made by people but it
was not. That's a natural thing.
And so we can see, we continue to see
rock breaking very very flat along this
stream cut. And so I'll walk down here
and show you this other one and
then I'll pick up again a little bit
later. But we can see as we move along
here this rock here and it really does
look unnatural. It looks like, you know,
someone carved it. But they didn't, this
is very natural. This is just what this
rock looks like. And so it's it's really
phenomenal, it's really beautiful out
here. And so we have this, we have
this rock that's breaking very very flat,
and what's more it's breaking flat but
it's not breaking flat parallel to the
ground. So let's see if we can figure
out what's going on, and we're gonna walk
this way and we'll see if we can work this out.
Hey everyone look what I found.
It's the rock from the parking lot, if
we kind of zoom around here we can see
that there
is a lot of it actually. It goes all the way
over here, and I'll just give you a
little look around here. This is about 50 yards
from where we were before. Now the thing
you want to get used to here, or one thing
you want to get used to here is that it
doesn't look exactly like the rock in
the parking lot. It's a little bit
greener, you know, it's got
lichen growing on it. This is one of
the first things that geologists have
to get used to, is, you know, we learn
rocks one way in a lab or something like
that, and then we get out in the field
and there is a period of time during
which you are just lost. You're just
not getting what's going on because the
rocks don't look anything like what you
learn in the field, or rather in the lab.
But here you can see that you know we've
got that same thing going on. You can you
can see this one just making a brick for
us. We can see that tendency for the rock
to break in two directions one of them
this way,
and then the other one this way. And so
it really does tend to just break out
into very nice bricks. And this is where
they were quarrying the rock to do the
building. It's not far, you have to carry
it uphill a bit, but that's okay it's not
very far and it's a very reasonable
place to be getting building stones from.
And so what is it? Well, the locals call
it rhyolite and this points to some
danger in, you know, just kind of going
what the locals call it because rhyolite
is an igneous rock and this is not
igneous. It is a, here we go guys, a metarhyodacite.  Not really important, it's a
metamorphic rock right? This tendency for
it to break along this plane right here
is the foliation. That's that layering
that metamorphic rocks develop. Now the
cool thing about foliation is that the
direction that the pressure that made
the metamorphic rock came from is
perpendicular to the direction of
foliation. So if our direction of
foliation is running this way, then we
know that the
pressure was running this way. Was actually
running in this secondary breakage
direction. And so you know metamorphic
rocks are useful because you can use
them to reconstruct ancient tectonics
and in this case we're going to use it
to reconstruct the direction that that
pressure was is running. and now you know.
We could get out a fancy instrument and,
you know, actually measure that angle and
do all kinds of cool math and stuff like
that. But for our purposes, you know, we
just know that okay yeah you know the
main direction that rock is breaking is
foliation so the pressure was
perpendicular to that. And so for our
purposes today what that does is that
makes really nice building stones. You
can just pull them out and build a
building with them they're not quite the
right size wack em just right and they'll
break very flat for you so it makes a
very good, very good building stone. This
the same foliation is is why we make, a
lot of times, we'll make a tile out of
the metamorphic rocks slate. Even roofing
tile because it does, it breaks very very
flat along that one plane. Okay so this
place is beautiful so I'm gonna hike in
that direction for a bit and I'll be
back with you soon okay. Hello so there's
some rock, and it looks like the same
rock we've been looking at all day and
if we were doing work out here to try to
reconstruct the tectonic we might be
inclined to take some measurements on it
so that we could get the direction of
the foliation and the direction of the
pressure and all of that. But don't be
fooled that rock is float, it's been
broken off right? Once it's broken off
and moved around it's useful but it's
not useful for that. And it's obvious I'm
kind of cheating a little bit here. If I
go upward you can see how that's part of
some rock that they placed there to
shore up the trail. But it's very
important that when they're doing this
work on tectonics and you're working out
the orientation of the foliation it
needs to be attached to the bedrock
right? you can't just pick up any ole rock and do that.
It's not always easy, there can be some
really big pieces of rock that are still
not attached to the bedrock we call that
float
Float is useful for some things, not for
orientation purposes. Not for either
bedding or foliation or anything like
that. Not useful, like I said, this was
kind of obviously placed here to shore
up the trail so that's pretty easy, but
it's not always that easy. So you want to
be very careful when you're out here and
you're doing geology if you want the
orientation of something make sure it's
not float. Okay, moving along.
So here we are just down a bit from that
outcrop and I just kind of wanted to
show you guys something. I'm hiking along
the stream, you can see it down there and
if I look downstream we can see a pretty
substantial stream valley that's been
carved by a pretty small stream. This is
called an under fit stream this is a
stream that is really currently too
small for the valley that it occupies.
Now, you know, some of this is time. That
stream has had plenty of time, you know,
to cut down through and make this pretty
big stream valley for the size of the
stream. But another thing to keep in mind
any time you're doing geology, let's say
north of Long Island New York you have
to keep in mind that that area was
covered by glaciers until a few thousand
years ago. And then any time you're doing
geology or what we would call
geomorphology looking at landscapes in
the lower two-thirds you have to
understand that when those glaciers
melted, they sent ... all kinds of water
south. So we have a lot of under fit
streams in the southern two-thirds of
the United States because of glacial
melting. And so this stream used to be a
lot bigger than it is now because it
used to be getting fed by melting
glaciers. It's not anymore so what's left
is a relatively small stream just being
fed by rain water around here.
So you always have to keep in mind
what came before when you're looking at
landscapes and when you're trying to
sort out what
going on here. Under fit
streams are very common in like the
lower two-thirds of the United States.
okay
hiking on.
Hey,  so I'm about to turn left and hike up out of this stream Valley
so I figured I'd do my little wrap-up
down here. so this is what geologists
do, you know, we go into the field we pay
attention to what's going on and in this
case we're dealing with metamorphic
rocks so we would be, you know, measuring
that foliation to get an idea about
tectonic pressure, tectonic stresses, and
whatnot back when these rocks were
metamorphosed. And so if it was
sedimentary we'd be doing something a
little bit different, if it was igneous
we'd be doing something a little
different. But but you know what we do is
we go into the field we look at the
rocks and we figure out what happened
right? And that's that's the fun part.
We're not just looking to give it a name
the name was secondary right? The
interesting part is, you know, what
happened out here to make it look like
this? In the case of the rocks what
happened? But you know in the case of the
under fit stream  what happened? There's
all kinds of things going on and this is
what geologists do, we go into the field
and we sort it all out.
Okay you have a handout, go ahead and do
it and stick it in the drop box and
that'll be done. This is gonna count
as a lab, so go ahead and do that and
if you need to go back and watch the
video again go back and watch the video
again. All right, okay you guys take care
bye-bye
