NARRATOR: Earth. A unique planet. Restless and dynamic. Continents shift and clash. Volcanoes erupt. Glaciers grow and recede. Titanic forces that are
constantly at work, leaving a trail of geological
mysteries behind. In this episode, we investigate
the formation of the Rockies, the North American
mountain range shrouded in mystery, flanked
by huge slabs of rocks with ancient sea fossils
buried high in its slopes and crowned by jagged peaks
that geologists believe were once double the
height they are today. Scientists piecing
together their story uncover evidence of massive ice
sheets, collapsing mountains, and explosive
volcanic eruptions. A geological history that
brings us one step closer to understanding how
the Earth was made. The Rockies-- a
majestic mountain range towering high
above the American West. It's the longest chain in North
America and the third longest in the world, stretching over
3,000 miles from New Mexico through Colorado, Wyoming, and
Montana, and north into Canada. For decades,
geologists have been puzzled about how this
giant mountain range rose from the plains. The investigation begins
with a specific type of rock. Here we are in the heart
of the Rocky Mountains. We're in an amazing
place to begin with. And right here at
Red Rocks, we're in the midst of an
amphitheater of rock. [music playing] 13 miles west of
Denver, Colorado, two 300-foot-high
sandstone monoliths slope 45 degrees into the sky. Each is taller
than Niagara Falls. Together, they form the walls
of a unique musical venue. [cheering and applause] But there is more to these
rocks than fine acoustics. These rocks tell the story of
how the Rocky Mountains were made. The story begins with a mystery. 8,000 feet high in
the Colorado Rockies, 60 miles northwest
of Boulder, all kinds of strange impressions are
found in rocks scattered over the landscape. We find more than 100
species of marine animals right here at this site. We find sharks. We find lobsters. Crabs. We find beautiful fossil clams,
which are all over the place. NARRATOR: These fossils
are crucial evidence of what existed here
before the Rockies emerged. We're sitting at about 8,000
feet in the middle of the Rocky Mountains. And so when these
fossils were formed, this was below the
level of the ocean. This was below sea level. NARRATOR: This area was
covered by a vast inland sea. It existed for over
30 million years and stretched from Utah to
Missouri and from the Gulf of Mexico to the Arctic Sea. And at this very site, it
would have been very warm, almost tropical. And so envision maybe a day
on the beach in Florida, or something like that. NARRATOR: This warm climate
attracted a unique type of creature that left
behind large, round imprints in the rocks. These fossils would
play an important part in the investigation. This fossil here is a
giant fossil ammonite. And this animal, this
coiled shell right here, is a relative of
modern day squids. So the closest living relatives
today are squids, nautiloids, octopuses, things like that. And so in this big
coiled shell here, the animal would have
lived at this end, and its tentacles would have
stretched out right here. And this animal is
really quite remarkable. It's about the size
of a truck tire. And this is incredible because
most ammonites aren't this big. NARRATOR: Nowhere else have
scientists found a greater number of these prehistoric
creatures than here. Miller has come up with a
theory why so many of them came to this area. We think this
particular fossil here was a female ammonite. And we think that in part
because male squids are smaller than female squids by a lot. So just looking around
the fossil deposits here, we found a male ammonite,
this small one here. So compare the size of this
guy to this very big one here. And when we look
across this landscape, we find mostly
these big ammonites, and so we think that maybe
all these females got together to spawn and then died
after they spawned. NARRATOR: When the
ammonites became extinct, the map of North America
looked completely different. To the north, the Canadian
Rocky Mountains already existed. To the south, the American
Rockies had yet to rise. The date of the
ammonite's extinction holds a key to when
they first emerged. These animals died about 70
million years ago in the middle of the Western interior seaway. And so we know at that time,
about 70 million years ago, this site was below sea level. So we know then that
the Rocky Mountains had to rise from that seaway
sometime after 70 million years ago. NARRATOR: All that is left
from the ancient sea floor are these fossilized remains
high in the Colorado Rockies. Next, geologists
needed to find out what pushed the seafloor up. The investigation
moves to these slabs of rock flanking the Rockies
just outside Denver, Colorado. They are known as the
Flatirons, and they are part of the same formation
that make up the Red Rocks Amphitheater. These slabs of rock are unusual
because they contain holes-- holes that make the Flatirons
appealing to climbers and geologists alike. ALAN LESTER: So when we go
climbing in the Flatirons, we're climbing on
really nice handholds. In some cases, handholds
that have been formed either by the pebbles in the rock or
by zones of fine-grain material that are easily
removed by erosion-- the shales and the silt stones. Those layers get removed,
leaving a notch for the hands to go in. And it makes for
fantastic climbing. NARRATOR: The holes
are a clue as to how these strangely tilted
Flatirons were formed. The layers themselves,
the different grain sizes in the layers-- the silt, the
sand, the pebbles-- this tells us that these
are sedimentary rocks. NARRATOR: Sediments
form in water when and small pieces of rocks
settle on the ground. Over millions of years, they get
compressed into layers of rock. Taking a closer look,
Lester can find out more about the surroundings
they formed in. These were not just
deposited in any kind of sedimentary situation, but
they were deposited in rivers capable of transporting
big particles and busting them up
as it goes along. Sheets of sand and gravel built
up a thick sedimentary bed like a layered cake. But stream deposits are
rarely more than a few degrees from horizontal. These rocks, you
can see the layers and the layers in the Flatirons
behind me are 60 degrees. NARRATOR: Something cause
these vast slabs to be tilted. The investigation moves
10 miles Northeast to Flagstaff Mountain,
located in the outer ranges of the Colorado Rockies. ALAN LESTER: I'm
standing here right next to a miniature Flatiron. It's tilted like the
Flatirons at about 60 degrees. It's steep. How did it get that way if it
was originally a stream gravel deposit? NARRATOR: The answer lies in
the darker rock underneath. It is granite, and
looks completely different to the
flat iron rock above. There's no layering
in this rock, unlike the Flatiron rock,
which does have layering. There's no pebbles in this rock,
unlike the Flatiron rock, which does have pebbles. NARRATOR: A close-up
investigation of the granite reveals that it is
full of minerals. This offers another clue
to how the Rockies emerged. ALAN LESTER: So I've picked
up this granite here. And taking a look at it,
I see quartz and feldspar and a little bit
of mica in here. Very characteristic
of a rock like this that has cooled from a magma-- from a liquid rock. NARRATOR: Among the
minerals is iron. It is responsible for the
dark color of the rock. The precise quantity of iron
tells scientists the depth at which the rock was formed. ALAN LESTER: So we've taken
this rock into the laboratory. And we do the
chemistry on this rock. And we can actually determine
that not only did it cool and crystallize at depth-- that depth we can estimate
at about 15 miles down. It's now at the surface. How did it get here? It's been pushed up by the
rise of the Rocky Mountains, and in doing so, look what
it's done to the Flatiron. NARRATOR: Scientists
investigating the Rocky Mountains
have found two clues about their early history. Ammonites on a site
8,000 feet high are evidence that the area
was once under the sea. Traces of iron in
granite is evidence that rock pushed up from
15 miles below the surface, tilting the flat iron. And it didn't just happen here
but along approximately 1,000 miles of the American Rockies. Geologists now needed to find
out what monumentality forces were responsible for
this massive upheaval. A force capable of that
amount of heavy lifting would have to have
been on a global scale. Geologists believe this force
was caused by plate tectonics. The Earth's crust is broken up
into a series of interlocking plates. These plates are
continuously on the move. Over millions of years, they
collide and break apart, forming new continents
and geological features around the world. When the Rockies formed,
two of these plates smashed into each other at
the American West Coast. What we know is that at the
time of this granite uplift, on the Western margin
of North America, ocean crust and oceanic
plate was subducting beneath the North
American plate, and it was doing so at
a high rate of speed. As such, it was transferring
stress into the interior of the continent. NARRATOR: As the two plates
move towards each other, they squeezed the crust. Over millions of years,
it folded and buckled, forming tall mountains. This was the birth of
the American Rockies. But a mystery remained. How did the collision
of two tectonic plates at the Western edge
of North America caused the rise of the Rockies
500 to 1,000 miles inland? Mountain ranges that form
on the margins of continents are pretty easy to explain, or
where continents have collided. Where India slams into
Asia, we get the Himalayas. Where oceanic crust dives
beneath the continental margin in the Northwest, the Cascades. Or in South America,
the Andes Mountains. But these mountains here in
the middle of a continent are much harder to
explain, and they've been an enigma for decades. NARRATOR: Only recently,
geologists have come up with a plausible theory. They suspect the Rockies
formed along a line where the crust is very fragile. ALAN LESTER: What happens when
the continent gets compressed? Especially if there's a
weak zone or a zone that's prone to buckling, it rises. That's what's brought this
granite to the surface. NARRATOR: Geologists
now understood how the Rockies
rose, and they had a date for when it happened. But what were these
early mountains like? How do they compare to
the mountains of today? On a site in the Rockies 70
miles northwest of Denver, geologists find a clue. The mountains that
we see here today aren't the mountains that were
around millions of years ago. They're always evolving. Rivers are shifting. Peaks are shifting. It's a very dynamic process. It's almost as if the
mountains are alive themselves. NARRATOR: Miller sets out
to estimate the height of the early mountains. But how can you
measure something that is no longer there? Once more, fossils provide the
evidence he is looking for. What's amazing about
collecting fossil is that you're really
the first person to see this when you
crack open a rock. It's the first time
it sees light again after 60 million years. NARRATOR: Miller has uncovered
a 60-million-year-old fossilized leaf. It's from a tree that grew
here just 10 million years after the Rockies began to form. And intriguingly,
this leaf holds a clue to the height of
these early mountains. Or more precisely, it's the
edges of the leaf, known as leaf margins. Botanists know that in
colder temperatures, the margins tend to have
more teeth than leaves that grow in warmer areas. Leaves with teeth do
better in Colder climates because teeth are
actually really advantageous in jumpstarting
growth at the beginning of the growing seasons. In this case, you can see this
beautiful fossil leaf here with teeth, and
each of the teeth are little hotbeds
of photosynthesis. So when that leaf first
comes out of the bud, it gets a jumpstart on
leaves that don't have teeth. NARRATOR: Miller
uses this information to find out about the height
of the young Rocky Mountains. In a simple but
powerful technique, he compares the number of leaves
with teeth to those without. You go to a particular area
and you pick up all the species of leaves that are there from
the trees that are growing in that area, and you compare
the number of species that have teeth to the
number of species that have smooth margins. That gives us some idea of
what the temperature is. NARRATOR: So the
higher the proportion of plants with jagged
edges compared to plants with smooth edges, the colder
the temperature of the site. And the Colder the temperature,
the higher the mountain. So if you got into a
hot air balloon here today and you floated straight
up into the atmosphere, the temperature would decrease
in a very predictable way. It turns out that
for about every mile you go up in the atmosphere,
you lose about 20 degrees Fahrenheit. So if we know how temperature
changes with elevation, we can back out elevation from
those estimates of temperature. NARRATOR: To work out the
height of the early mountain, Miller needs to compare
samples from two areas. One at the base of the
mountain and one at the top. Fossils found at the
base of the Rockies near to present-day Denver
have an amazing story to tell. These ancient leaves are
incredibly similar to plants growing in the tropics today. So after the Rockies rose,
down in the area of Denver, it was subtropical
and tropical forests. We had palms and cycads
and canopies like we see in the tropics today. Up here, we had a forest
that looked probably more like a forest that grows
in North or South Carolina on the East Coast of the US. NARRATOR: By comparing
the ancient fossil leaves from the top of the
mountain with fossil leaves from the foot of the
mountain, Miller has come up with a surprising conclusion. Turns out that the fossil
leaves here are predominantly toothed as compared to those
that are in Denver, which are predominately smooth margin. And it turns out
the ones in Denver grow in a climate that was
about, on average, about 75 degrees Fahrenheit. The ones up here grown in
a climate that was probably about 50 degrees Fahrenheit. So if we know how temperature
changes with elevation, that means that this site when
these fossilized were deposited was about a mile
higher than Denver. Today, it's only a
half a mile higher. So 60 million years
ago, the mountains would be twice as high
as they are today. NARRATOR: After the Rockies
emerged from the sea, it took them 10
million years to rise. 60 million years ago, they
reached spectacular heights of 28,000 feet, rivaling
the Himalayas today. The deep history of
the Rocky Mountains is beginning to take shape. A weak line in the crust
explains why the Rockies rose 500 to 1,000 miles inland. Fossil leaves show that the
young Rocky Mountains were once nearly twice their size. Half of the rock that formed
them originally has vanished. Scientists are now trying to
unravel the processes that cut them down to the
size they are today. a a covered the area where
the American Rockies stand tall today. 70 million years ago,
the sea retreated as the Rockies began to rise. 60 million years ago,
the Rocky Mountains reached their pinnacle,
towering into the sky with peaks over 28,000 feet high,
rivaling the Himalayas. Since then, the
entire mountain range has lost nearly half its height. Geologists investigating
the history of the Rockies are trying to
discover what happened to the billions of tons
of rock that went missing. The investigation starts with
a mystery at the Owl Creek Mountains in the
Wyoming Rockies. The mountains are
sliced by a river that has formed a deep canyon. Well, the Wind River
is very perplexing. It chose to take a straight
path right through the core of a major mountain range. This is not the way that
rivers normally act. Usually, they'll take
the easiest route, which is downhill. But this river cut right
through a major mountain range and has been a mystery. It was a very perplexing
issue to early geologists in the region. This river led to
confusion as early as 1806 when Meriwether Lewis and
William Clark mapped the area during their famous expedition
to explore uncharted territory in the west. When they came to the area
around the Owl Creek Mountains, they assumed there
were two rivers. North of the mountain
flowed a river which they named
Big Horn, thinking it was different to
Wind River in the south. But later surveys showed that
the Bighorn and Wind River are, in fact, one river that
channeled through the mountain. Recently, geologists have come
up with a possible answer-- an answer that could
also explain what happened to the once towering
peaks of the Rockies. They proposed that millions
of tons of rock eroded away, filled in the valleys,
and covered the lower parts of the mountains. It completely
changed the terrain. FRED MCLAUGHLIN: At one
point in ancient history, the basins in Wyoming were
filled with sediments that had eroded off the mountains. This allowed the river to be
at a higher plane and meander wherever it wanted
to on its course. NARRATOR: As the
water flowed, it carved deep into the
sediments and rock underneath. FRED MCLAUGHLIN: Eventually,
it cut down a channel into the mountain and it
eventually excavated right through the mountain. NARRATOR: But this
is just a theory. Now, geologists needed to
find proof on the ground. The search is on
for the rock that eroded from the early Rockies. The investigation moves to a
series of 1,000-foot-tall hills in the Powder River
Basin in Wyoming. Known as the
Pumpkin Buttes, they stand tall in an otherwise
wide, empty landscape. Hidden behind the horizon
are the Bighorn Mountains, the nearest range
of the Rockies. These hills are not formed from
solid rock but a collection of rubble. This rock which we find all
over the top of the Pumpkin Buttes in Wyoming is granite. The closest granite
we find to this area is the Bighorn Mountains
nearly 100 miles to the west. NARRATOR: The round shape
of the granite rocks is further proof that
they traveled from afar. Tumbling downhill in
rivers and landslides rounded them on their journey
over millions of years. This was a crucial step
in the investigation, tracing the missing rock
from the early Rockies. Rock and cobbles eroded down
from the Bighorn Mountains and filled up the basin
to at least 1,000 feet, the height of the
Pumpkin Buttes. The Pumpkin Buttes
are unique because this used to be the actual surface
level of the basin itself. The rest has been eroded
away, 1,000 feet of sediment, to the basin that we see now. NARRATOR: But the rubble
found here is nowhere near enough to have covered
the Owl Creek Mountains. McLaughlin traveled
to Darton's Peak, 100 miles west in the
Bighorn Mountains. On a cliff 9,000 feet high,
he finds granitic cobbles that are strikingly similar to
the ones on the Pumpkin Buttes. They, too, are from the
core of the Rocky Mountains. The core of the rocky
mounds are made extensively of granite, much like
what you see here. These are from the Bighorns
that have been transported down, rolled, and smoothed along their
way to create these smaller boulders and cobbles. NARRATOR: This is
strong evidence that cobbles eroding
from the Rockies filled in the basins and
valleys to at least 9,000 feet, slowly burying the mountains
under their own debris. Where once the
mighty Rockies stood, there was now a
gray, barren plain with only the peaks of the old
mountains piercing the surface. The same process has happened
in other mountain chains, too. There is evidence that the
European alps were also cut in half by erosion. At their base, scientists found
hills formed out of millions of tons of rock that
had cascaded down and reduced their height. But the story of the eroding
Rockies wasn't over yet. After erosion turned the
landscape into a gray cobble field, another
disruption happened. Evidence for this
is a layer covering the top of the cobbles. It's very light. It's a very fine grain. It's actually a volcanic ash. As you can see, it's made
of very, very fine-grained sediments compared to this
boulder conglomerate, which is made up of big hunks of rock. It sits directly on
top of this unit, and it was laid horizontally
from mostly ash fall. NARRATOR: This
fine-grained ash suggests huge volcanic eruptions nearby. They spewed out thick clouds of
hot air, ash, and volcanic rock which settled on the ground. Radiocarbon dating the rock
revealed that it happened 25 million years ago. FRED MCLAUGHLIN: Ash was
deposited as it came out of the sky as plumes. Most of it came from the
West and was deposited in basins across Wyoming. NARRATOR: After the
lower Rockies were buried by their own rock,
volcanic ash settled on top and covered the area
with a thick white sheet. At the time of
the deepest basin fill of this volcanic material,
all you would see in this area was be the very tops
of the peaks exposed. The rest would be large,
extensive, lateral ash sheets. NARRATOR: Erosion and
volcanism completely transformed the terrain
and buried the Rockies. But then, over
millions of years, rivers flushed out
the eroded rock. Most of it is thought to
have ended up in the Missouri and Mississippi rivers from
where it was transported into the sea. What's left are the
mountains we see today. This also confirmed
the theory geologists had about the formation
of Wind River Canyon. The incredible amount of infill
buried the Owl Creek Mountains. Wind River flowed
on top and began carving into the
mountains, creating the canyon we see today. The investigation into what
happened to the early Rocky Mountains reveals
two major clues. Granite found on
the Pumpkin Buttes is evidence that the early
Rockies dumped there eroded rock into the basins. Wind River Canyon, cutting
straight through the Owl Creek Mountains, is evidence that
the Rockies were buried by their own debris. The once mighty Rockies
had now been cut down to nearly half
their original size, but the story was far from over. Before they became the
mountains we know today, they would have to endure
an even greater assault. and the Rocky Mountains
emerged from the seafloor. 60 million years ago, they
reached their peak height, twice what it is today. Then, for millions of
years, the Rockies slowly eroded away to half
their original height, until 3 million years ago,
another dramatic chapter in their story began
that would transform them into the mountains
we know today. Geologist and photographer
Bob Anderson takes to the air. He is looking for clues
that will tell him how the mountains have evolved. First, he flies over Boulder
Canyon in the Colorado Rockies. It is an area that has remained
almost unchanged over millions of years. So this is Boulder Canyon
we're flying up right now. And you can see how the river
has incised maybe a few hundred feet down into otherwise
relatively rolling terrain. NARRATOR: The mountain peaks
that existed on the young Rocky Mountains were rounded off
as rivers and streams eroded the rock. It's this rolling terrain that
that the landscape looked like in the aftermath of the
mountain-building event that ended about 50
million years ago. NARRATOR: But as
Anderson climbs higher to Long's Peak in the Rocky
Mountain National Park, the terrain changes. Instead of rolling hills,
there are rugged mountains with steep, jagged cliffs. It's evidence that another
force has been at work. The most famous of these
cliffs is the Diamond. Named for its shape,
it's a vertical wall with a sheer, 900-foot drop. The summit, about
45,000 square feet, is the same size as
a football field. Well, we're flying
beside Long's Peak, one of the biggest climbing
challenges in the Rockies. For a century, it's
been a climbing mecca. It's a gorgeous,
intact piece of rock. NARRATOR: This awesome wall
is the most difficult climb in the whole of the Rockies. Since it was officially
open to climbers in 1960, it has claimed over 50 lives. Back on the ground, Anderson
is looking for evidence that will reveal the processes
that shaped the jagged peaks. On a hillside, he finds
mysterious, large boulders scattered across
the valley floor. A closer look uncovers some
secrets about their origin. Well, I'm standing in
front of a rounded boulder that itself is sitting on
a smooth bedrock outcrop. Both the boulder
and the outcrop are covered in lichen here of
green to black to gray colors. And therefore, I had to
whack off a piece of the rock in order to see inside the rock. And indeed, it is different. The minerals that I see
in the texture of the rock is different from
the underlying rock. And therefore, the
rock is foreign to this particular site. Anderson searches the ground
for more clues as to how this massive boulder got here. Nearby, he finds a smooth
surface with very fine scratch marks. I'm sitting on a
polished surface. This little piece right
here is smooth to the touch. And if I look at it
in a certain way, the light glints off
of it just right, I can see that
there are scratches running in this direction
across the surface. NARRATOR: The only force
that could have produced these fine parallel
scratches on the rock is ice, and lots of it. It's a clue that a
massive glacier once filled this valley. And that tells me that the
glacier came down valley, came across this surface,
and eroded it. Each one of these scratches
corresponds to a sand grain embedded in the sole of the
ice that, just like sandpaper, smooths off the surface. So zillions of sand grains
over thousands of years will have eroded
this surface smooth. NARRATOR: As glaciers
flowed down the valley, they picked up rocks and grit. The ice pushed down
on these cutting tools with the weight of over 1,000
fully loaded garbage trucks. It left scratch marks
all over the Rockies up to 1,000 feet high. This is evidence that
a massive wall of ice covered this part of the Rockies
and shaped the mountains. The ice ripped out the
rock from the valley walls and left behind the jagged
cliffs and rugged edges. For the last few million
years, perhaps 3 million years, glaciers have come and gone
from the Rocky Mountains. And every time they come
across the landscape, they're capable of eroding
that landscape at rates that are perhaps fractions
of an inch per year, meaning that over the
course of one glacial cycle, you perhaps erode
10, 20 feet of rock. Ice also created
the broad canyons. With every ice age, new
glaciers ground their way down V-shaped river
valleys and turn them into broad, U-shaped canyons. For the glacier, the
whole valley is its channel. So any place where the
glacier touches the wall, it's capable of eroding it. And therefore, the walls will be
made more vertical on the edges and be flattened on the base
until it gets to now a U-shape which then propagates downward. NARRATOR: Ice also explains
the presence of these boulders. They hitchhiked at the
bottom of a glacier down the frozen valley. When the last ice
age came to an end and the glaciers melted
about 10,000 years ago, the boulders were left behind. Scientists had found
two pieces of evidence that were responsible for the
jagged looks of the Rockies today. A solitary boulder
foreign to the area could have only been
transported here by ice. Striations showed scientists
that a glacier at least 1,000 feet thick covered the Rockies. Ice was responsible for the
dramatic shape of the Rockies today. But the mountains keep evolving. Recently, scientists
discovered alarming evidence that they may collapse
into a deep rift. For thhave sculpted the years,
compresRocky Mountainsan to their present formation. But the geology that created
this impressive mountain range has also the potential
to destroy it. Over the last 25 million
years, a gigantic rift has been opening up at the
southern end of the Rocky Mountains. It stretches over
160,000 square miles and is known as the
Rio Grande Valley. Geologists are
eager to investigate how this giant, drifting
valley could affect the future of the Rockies. They find their first lead in
San Isidro, New Mexico, north of Albuquerque. The area is dominated by
bright yellow porous rock known as travertines. Curiously, geologists think
this rock forms from water. This water has some
unusual characteristics. That is, this water is capable
of precipitating or depositing a new rock called travertine. It's like kind of like
the scale in your teapot. NARRATOR: Travertine
rock is made out of calcite, the same material
that builds up limescale. These rocks grow very rapidly,
some enlarged by a few inches per month. About a liter
of the water will be able to drop
out or precipitate a little pile of calcite about
as big as an aspirin tablet. NARRATOR: Like limescale
building up in a hot water kettle, travertines form
around warm springs. Measurements confirm
that water temperature around the travertines
is roughly 77 degrees. Besides the ability
to build rock, this hot water has
more secrets to tell. Laura Crossy and Carl Carlstrom
have a hunch that the water is warmed up by heat from the
Earth's interior rising up through cracks in the rock. They form as the rift
valley pulls apart. Climbing down a cave 25
feet below the surface, they are hoping to
find further evidence. The water contains microbes. They are microscopically
small organisms. Most of them consist
of only one cell. When scientists analyzed
their genes in the lab, they found something remarkable. What we found in springs like
this by doing the DNA analysis is that the microbes that are
coming up these faults are much more like what we find in
mid-ocean ridges than like the rivers and streams we
would expect in a continental setting. NARRATOR: Mid-ocean ridges
a very long mountain chains under the sea. Just like the rift
valley, they also form in geologically
active areas where lava constantly erupts
and builds up new crust. Any living organism
surviving down there has to be able to cope
with these hot conditions. LAURA CROSSEY: The springs
here and the mid-ocean ridge settings are also
characterized by the upwelling of deep, hot fluids
from within the Earth, indicating that these
both are connected to that deep, tectonic setting. NARRATOR: The microbes suggests
deep tectonic forces are at work, but there is even
more compelling evidence. Carlstrom and Crossy find an
unusually high amount of gas bubbling up through the water. These samples are
kind of fun because it looks like an empty glass vial. But it started out full of
water, and then we fill it up. You turn it upside
down in the water, and the gas displaces the
water until it's full of gas. NARRATOR: A lab analysis
identifies the gas as helium. This is the conclusive evidence
that deep tectonic forces are at work here. The helium is there is
the interesting, the most interesting gas for us. It's the smoking gun of evidence
for where these fluids have come from. There's two forms of
helium, but the helium-3 that we're most interested
in and that form of helium is only derived from
the Earth's mantle. NARRATOR: The mantle is a part
of the Earth's interior 30 miles below the surface. It is made up of
hot molten rock. In areas where magma moves
up, pressure on top of it decreases and gases such
as helium are released. They find their way
through faults and cracks until they reach the surface. So helium gas is
conclusive proof that geological forces
deep under the earth are building up. And the effect it will have
on the Rockies is devastating. The Rio Grande Rift
is an area that's tectonically in a different
way than you think of building of mountains. This area is the next
stage in the life sometimes of a mountain belt where
it starts to collapse. It starts to extend. NARRATOR: As hot
magma surges upwards from 30 miles below the surface,
it forces the area on top to spread. The surface stretches and thins
and opens up a deep chasm. As the rift opens, the
mountains to each side crumble into the valley. You can think of a piece of
taffy that's being stretched, and it might break on the top. And those breaks would lower
pieces of the-- they would drop down And then once you have
what's called a fault valley, then the sediments wash in
from the high mountains. It's an immense structure. It's about 6 miles deep. It's about as deep as Mt. Everest is high. But when you drive across it or
you look at it from any vantage point, you don't see
that entire depth because it's all
been filled with sand and gravel progressively as
the extension took place. NARRATOR: Today,
the Rio Grande Rift stretches over 160,000 square
miles from Mexico in the south where it's broadest to
Colorado in the north where it's only just
begun to open up. This rift is propagating
northwards into the higher Colorado Rockies. What's going to
happen to Colorado-- those mountains will probably
collapse by rifting as the rift propagates, zippers northward. And you can visualize that
what's now in Colorado is more similar to
what was in New Mexico before the Rio
Grande Rift opened and before the
mountains collapsed. NARRATOR: Looking ahead
in the distant future, there could be
challenging times. The tectonic forces
that created the Rockies could eventually lead
to their destruction. When we think about the
great continental rifts of east African and Rio Grande
Rift, the question arises, is the content going
to split apart here? if this rifting
carries on, are we going to have beach front
property right here in New Mexico? And the realtors are
very interested in this, but so are the geologists. NARRATOR: The formation
of the Rocky Mountains is a remarkable story. 70 million years ago, the
death of ancient ammonites marked the rise of
the Rocky Mountains from the retreating inland sea. 60 million years ago,
leaves with jagged margins grew on the mountains that
were twice as high as today. 10,000 years ago,
a solitary boulder marked the retreat of
the last glacier that sculpted the Rockies. And helium gas in the
Rio Grande Valley today is a clue that the area
deep under the surface is active again. If rifting continues and the
Rio Grande Valley widens, the area of the Rocky Mountains
could one day rip apart. A new sea would move in like
the vast inland sea that covered the area 70 million years ago. The Rocky Mountains, the great
backbone of North America, would slowly disappear, and
the continent would once more split-- living proof that the
Earth is never at rest.
