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How the Rocky Mountains were Made | How the Earth Was Made (S2, E5) | Full Episode | History — Transcript

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0:03earth
0:05a unique planet restless and dynamic
0:08[Music]
0:10continents shift and clash
0:13volcanoes erupt glaciers grow
0:17and recede titanic forces that are
0:20constantly at work
0:22leaving a trail of geological mysteries
0:25behind
0:28in this episode we investigate the
0:30formation of the rockies
0:32north american mountain range shrouded
0:35in mystery
0:36flanked by huge slabs of rocks with
0:39ancient sea fossils buried high in its
0:41slopes
0:42and crowned by jagged peaks that
0:44geologists believe
0:45were once double the height they are
0:47today
0:49scientists piecing together their story
0:52uncover evidence of massive ice sheets
0:55collapsing mountains and explosive
0:58volcanic eruptions
1:00a geological history that brings us one
1:03step closer to understanding
1:05how the earth was made
1:13the rockies a majestic mountain range
1:16towering high above the american west
1:20it's the longest chain in north america
1:22and the third longest in the world
1:25stretching over 3000 miles from new
1:28mexico
1:28through colorado wyoming and montana and
1:32north into canada
1:33[Music]
1:35for decades geologists have been puzzled
1:37about how this giant mountain range
1:40rose from the plains the investigation
1:43begins with a specific
1:44type of rock here we are in the heart
1:49of the rocky mountains we're an amazing
1:51place to begin with
1:53and right here at red rocks we're in the
1:56midst
1:56of an amphitheater of rock
1:58[Music]
2:0613 miles west of denver colorado
2:09two 300 foot high sandstone monoliths
2:12slope
2:1345 degrees into the sky each
2:16is taller than niagara falls together
2:19they form the walls of a unique musical
2:22venue
2:22[Music]
2:26but there is more to these rocks than
2:28fine acoustics
2:30these rocks tell the story of how the
2:33rocky mountains were made
2:36the story begins with a mystery eight
2:39thousand feet high in the colorado
2:41rockies
2:4260 miles northwest of boulder all kinds
2:45of strange impressions are found in
2:47rocks
2:48scattered over the landscape we find
2:50more than a hundred species of marine
2:53animals right here at this site we find
2:56sharks we find lobsters
2:58crabs we find beautiful fossil clams
3:00which are all over the place
3:02these fossils are crucial evidence of
3:04what existed here before the rockies
3:06emerged
3:09we're sitting at about 8 000 feet in the
3:11middle of the rocky mountains
3:13and so when these fossils were formed
3:15this was below the level
3:17of the ocean this was below sea level
3:21this area was covered by a vast inland
3:24sea
3:25it existed for over 30 million years and
3:29stretched from utah to missouri
3:31and from the gulf of mexico to the
3:33arctic sea
3:35and at this very site it would have been
3:37very warm almost tropical
3:39and so envisioned maybe a day on the
3:41beach in florida
3:43or something like that this warm climate
3:47attracted
3:47a unique type of creature that left
3:49behind large
3:51round imprints in the rocks these
3:54fossils would play an important part
3:56in the investigation this fossil here is
3:58a giant fossil ammonite
4:01and this animal this coiled shell right
4:03here is a relative of modern day squids
4:06so the closest living relatives today
4:07are squids nautoloids
4:09octopuses things like that so in this
4:11big coiled shell here the animal would
4:13have lived
4:14at this end and his tentacles would have
4:16stretched out right here
4:18and this animal is really quite
4:20remarkable it's about the size of a
4:22truck tire
4:22and this is incredible because most
4:24ammonites aren't this big
4:27nowhere else have scientists found a
4:29greater number of these prehistoric
4:31creatures than here
4:34miller has come up with a theory why so
4:36many of them came to this area
4:39we think this particular fossil here was
4:41a female ammonite
4:43we think that in part because male
4:45squids are smaller than
4:46female squids by a lot so just looking
4:49around the fossil deposits here we've
4:51found a male ammonite this small one
4:53here so compare the size of this guy
4:55to this very big one here and when we
4:58look across this landscape
4:59we find mostly these big ammonites and
5:02so we think that maybe all these females
5:04got together to spawn
5:05and then died after they spawned
5:10when the ammonites became extinct the
5:12map of north america looked completely
5:14different
5:16to the north the canadian rocky
5:18mountains already existed
5:21to the south the american rockies had
5:24yet to rise
5:25[Music]
5:28the date of the ammonites extinction
5:30holds a key
5:31to when they first emerged
5:35these animals died about 70 million
5:37years ago
5:38in the middle of the western interior
5:39seaway and so we know at that time about
5:4170 million years ago that this site was
5:43below sea level
5:45so we know then that the rocky mountains
5:47had to rise from that
5:49seaway sometime after 70 million years
5:52ago
5:54today all that is left from the ancient
5:56sea floor
5:57are these fossilized remains high in the
5:59colorado rockies
6:03next geologists needed to find out what
6:06pushed the seafloor
6:08up the investigation moves to these
6:11slabs of rock flanking the rockies just
6:13outside
6:14denver colorado they are known as the
6:18flatirons
6:19and they are part of the same formation
6:21that make up the redrock's amphitheater
6:25these slabs of rock are unusual because
6:28they contain
6:29holes holes that make the flatirons
6:32appealing to climbers
6:33and geologists alike so when we go
6:36climbing in the flatirons we're climbing
6:38on
6:39really nice hand holds in some cases
6:41handholds
6:42that have been formed either by the
6:44pebbles in the rock
6:45or by zones of fine-grained material
6:48that are easily removed by erosion the
6:51shales and the silt stones
6:53those layers get removed leaving
6:56a notch for the hands to go in and
6:59it makes for fantastic climbing the
7:02holes are a clue
7:03as to how these strangely tilted flat
7:05irons were formed
7:07the layers themselves the different
7:10grain sizes in the layers the
7:13silt the sand the pebbles
7:16this tells us that these are sedimentary
7:18rocks
7:20sediments form in water when sand and
7:23small pieces of rock settle on the
7:25ground
7:26over millions of years they get
7:28compressed into layers of rock
7:32taking a closer look lester can find out
7:34more about the surroundings they formed
7:36in
7:38these were not just deposited in any
7:39kind of sedimentary situation but they
7:41were deposited
7:42in rivers capable of transporting big
7:44particles
7:45and busting them up as it goes along
7:50sheets of sand and gravel built up a
7:52thick sedimentary bed
7:54like a layered cake but stream deposits
7:57are rarely more than a few degrees from
8:00horizontal
8:01these rocks you can see the layers and
8:03the layers and the flat irons behind me
8:04are 60 degrees
8:08something caused these vast slabs to be
8:11tilted
8:15the investigation moves 10 miles
8:18northeast to flagstaff mountain
8:20located in the outer ranges of the
8:22colorado rockies
8:24i'm standing here right next to a
8:26miniature flatiron it's tilted
8:28like the flatirons at about 60 degrees
8:30it's steep
8:32had to get that way if it was originally
8:34a stream gravel deposit
8:36the answer lies in the darker rock
8:39underneath
8:40it is granite and looks completely
8:42different to the flat iron rock above
8:46there's no layering in this rock unlike
8:48the flatiron rock which does have
8:50layering
8:50there's no pebbles in this rock unlike
8:52the flatiron rock which does have
8:54pebbles
8:56[Music]
8:58a close-up investigation of the granite
9:01reveals that it is full
9:02of minerals this offers another clue to
9:05how the rockies emerged
9:09so i've picked up this granite here and
9:11taking a look at it
9:12i see quartz and feldspar and a little
9:15bit of mica in here
9:17very characteristic of a rock like this
9:20that has cooled
9:21from a magma from a liquid rock
9:26among the minerals is iron it is
9:29responsible for the dark
9:30color of the rock the precise quantity
9:34of iron tells scientists the depth at
9:36which the rock was formed
9:39so we've taken this rock into the
9:40laboratory and we do the chemistry on
9:43this rock
9:44and we can actually determine that not
9:46only did it
9:47cool and crystallize at depth that depth
9:50we can estimate it about
9:5115 miles down
9:56it's now at the surface how did it get
9:59here
9:59it's been pushed up by the rise of the
10:01rocky mountains and in doing so
10:04look what it's done to the flatiron
10:07scientists
10:07investigating the rocky mountains have
10:09found two clues about their early
10:11history
10:13[Music]
10:14ammonites on a site eight thousand feet
10:16high are evidence that the area
10:18was once under the sea traces of iron in
10:22granite
10:22is evidence that rock pushed up from 15
10:25miles below the surface
10:27tilting the flat irons and it didn't
10:29just happen here but along approximately
10:32a thousand miles of the american rockies
10:35geologists now needed to find out what
10:38monumental forces were responsible
10:40for this massive upheaval
10:50lifted them up
10:52[Music]
10:56a force capable of that amount of heavy
10:58lifting would have to have been
10:59on a global scale geologists believe
11:03this force was caused by plate tectonics
11:07the earth's crust is broken up into a
11:09series of interlocking plates
11:12these plates are continuously on the
11:15move
11:16over millions of years they collide and
11:19break apart
11:20forming new continents and geological
11:22features around the world
11:25when the rockies formed two of these
11:27plates smashed into each other
11:29at the american west coast what we know
11:32is that at the time of this granite
11:34uplift on the western margin of north
11:36america
11:38ocean crust an oceanic plate was
11:41subducting
11:42beneath the north american plate and it
11:44was doing so
11:45at a high rate of speed as such
11:48it was transferring stress into the
11:50interior of the continent
11:52as the two plates moved towards each
11:54other they squeezed the crust
11:57over millions of years it folded and
11:59buckled forming tall
12:01mountains this was the birth of the
12:04american rockies
12:06but a mystery remained how of the
12:09collision of two tectonic plates at the
12:11western edge of north america
12:13caused the rise of the rockies 500 to a
12:16thousand miles
12:17inland mountain ranges that form on the
12:19margins of continents are pretty easy to
12:21explain
12:22or where continents have collided where
12:24india slams into asia we get the
12:26himalayas
12:27where oceanic crust dives beneath the
12:29continental margin
12:30in the northwest the cascades or in
12:33south america the andes mountains
12:35but these mountains here in the middle
12:37of a continent
12:38are much harder to explain and they've
12:40been an enigma for
12:41decades only recently geologists have
12:45come up with a plausible theory
12:48they suspect the rockies formed along a
12:50line where the crust is very fragile
12:53what happens when the continent gets
12:55compressed especially if there's a weak
12:57zone or a zone that's prone to buckling
13:00it rises that's what's brought this
13:02granite to the surface
13:05geologists now understood how the
13:07rockies rose
13:09and they had a date for when it happened
13:12but what were these early mountains like
13:15how do they compare to the mountains of
13:17today
13:18on a site in the rockies 70 miles
13:20northwest of denver
13:22geologists find a clue
13:25mountains that we see here today aren't
13:27the mountains that were around millions
13:29of years ago they're always evolving
13:30rivers are shifting peaks are shifting
13:32it's a very dynamic process it's almost
13:34as if the mountains
13:35are alive themselves
13:38miller sets out to estimate the height
13:40of the early mountains
13:42but how can you measure something that
13:44is no longer there
13:46once more fossils provide the evidence
13:48he is looking for
13:51what's amazing about collecting fossil
13:53is that you're really the first person
13:54to see this when you crack open a rock
13:57it's the first time it sees light again
13:58after 60 million years
14:02has uncovered a 60 million year old
14:04fossilized leaf
14:07it's from a tree that grew here just 10
14:09million years after the rockies began to
14:11form
14:13and intriguingly this leaf holds a clue
14:16to the height
14:17of these early mountains or more
14:20precisely
14:20it's the edges of the leaf known as leaf
14:23margins
14:24botanists know that in colder
14:26temperatures the margins tend to have
14:28more teeth than leaves that grow in
14:30warmer areas
14:32leaves with teeth do better in colder
14:34climates because teeth are actually
14:36really advantageous and jump starting
14:38growth at the beginning of the growing
14:39seasons
14:39in this case you can see this beautiful
14:41fossil leaf here with teeth
14:43and each of the teeth are little hotbeds
14:45of photosynthesis so when that leaf
14:46first comes out of the bud
14:48it gets a jump start on leaves that
14:50don't have teeth
14:53miller uses this information to find out
14:56about the height
14:57of the young rocky mountains in a simple
15:00but powerful technique
15:01he compares the number of leaves with
15:03teeth to those without
15:06if you go to a particular area and you
15:07pick up all the species
15:09of leaves that are there from the trees
15:11that are growing in that area and you
15:12compare the number of species that have
15:14teeth
15:14to the number of species that have
15:16smooth margins
15:17that gives us some idea of what the
15:18temperature is
15:21so the higher the proportion of plants
15:23with jagged edges
15:24compared to plants with smooth edges the
15:26colder the temperature of the site
15:29and the colder the temperature the
15:31higher the mountain
15:33so if you got into a hot air balloon
15:36here today and you floated straight up
15:37into the atmosphere
15:38the temperature would decrease in a very
15:40predictable way it turns out that
15:42for about every mile you go up in the
15:44atmosphere you lose about 20 degrees
15:46fahrenheit so if we know how temperature
15:48changes with elevation we can back out
15:50elevation
15:51from those estimates of temperature
15:54to work out the height of the early
15:56mountain miller needs to compare samples
15:58from
15:59two areas one at the base of the
16:01mountain
16:02and one at the top fossils found at the
16:06base of the rockies near to present-day
16:08denver have an amazing story to tell
16:11these ancient leaves are incredibly
16:14similar
16:15to plants growing in the tropics today
16:19so after the rockies rose down in the
16:22area of denver it was subtropical and
16:24tropical forests we had palms and cycads
16:27and canopies like we see in the tropics
16:29today
16:30up here we had a forest that looked
16:32probably more like a forest that grows
16:33in north or south carolina on the east
16:35coast of the us
16:38by comparing the ancient fossil leaves
16:40from the top of the mountain with fossil
16:42leaves from the foot of the mountain
16:44miller has come up with a surprising
16:47[Music]
16:48conclusion
16:50turns out that the fossil leaves here
16:52are predominantly toothed
16:53as compared to those that are in denver
16:55which are predominantly smooth margin
16:57and it turns out the ones in denver grew
16:59in a climate that was about on average
17:01about 75 degrees fahrenheit
17:02the ones up here grew in a climate that
17:04was probably about 50 degrees fahrenheit
17:07so if we know how temperature changes
17:09with elevation that means that
17:10this site when these fossil leaves were
17:12deposited was about a mile higher
17:15than denver today it's only a half a
17:17mile higher so 60 million years ago
17:19the mountains would be twice as high as
17:21they are today
17:26after the rockies emerged from the sea
17:28it took them 10 million years to rise
17:3260 million years ago they reached
17:34spectacular heights of 28
17:36000 feet rivaling the himalayas today
17:42[Music]
17:44the deep history of the rocky mountains
17:46is beginning to take shape
17:49a weak line in the crust explains why
17:51the rockies rose
17:52500 to a thousand miles inland
17:56fossil leaves show that the young rocky
17:58mountains were once
17:59nearly twice their size
18:02half of the rock that formed them
18:04originally has vanished
18:06scientists are now trying to unravel the
18:08processes that cut them down to the size
18:11they are today
18:15[Music]
18:22100 million years ago a vast inland sea
18:25covered the area where the american
18:27rockies stand tall today
18:3070 million years ago the sea retreated
18:32as the rockies began to rise
18:3660 million years ago the rocky mountains
18:38reached their pinnacle
18:40towering into the sky with peaks over 28
18:42thousand feet high
18:44rivaling the himalayas since then
18:48the entire mountain range has lost
18:50nearly half its height
18:53geologists investigating the history of
18:56the rockies are trying to discover
18:58what happened to the billions of tons of
19:00rock that went missing
19:02[Music]
19:06the investigation starts with a mystery
19:09at the owl creek mountains in the
19:10wyoming rockies
19:13the mountains are sliced by a river that
19:15has formed a deep canyon
19:19well the wind river is very perplexing
19:21it chose to take a straight path
19:23right to the core of a major mountain
19:25range this is not the way that rivers
19:27normally act usually they'll take the
19:30easiest route which is downhill
19:32but this river cut right through a major
19:34mountain range
19:35and has been a mystery is a very
19:37perplexing issue to early geologists in
19:39the region
19:42this river led to confusion as early as
19:451806
19:46when meriwether lewis and william clark
19:49mapped the area during their famous
19:51expedition to explore
19:52uncharted territory in the west
19:56when they came to the area around the
19:58owl creek mountains
19:59they assumed there were two rivers
20:03north of the mountain flowed a river
20:05which they named bighorn
20:07thinking it was different to wind river
20:09in the south
20:10but later surveys showed that the
20:12bighorn and wind river are in fact
20:15one river that channeled through the
20:18mountain
20:21recently geologists have come up with a
20:23possible answer
20:24an answer that could also explain what
20:27happened to the once
20:28towering peaks of the rockies they
20:31proposed that millions of tons of rock
20:34eroded away filled in the valleys and
20:37covered the lower parts of the mountains
20:39it completely changed the terrain
20:42at one point in ancient history the
20:44basins in wyoming were filled with
20:46sediments that had eroded off the
20:48mountains
20:48this allowed the river to be at a higher
20:51plane and meander wherever it wanted to
20:53on its course
20:56as the water flowed it carved deep into
20:58the sediments and rock
21:00underneath eventually it cut down
21:03a channel into the mountain and
21:05eventually escalated right through the
21:07mountain
21:10but this is just a theory now geologists
21:14needed to find
21:14proof on the ground the search is on
21:18for the rock that eroded from the early
21:20rockies
21:23the investigation moves to a series of
21:25thousand foot tall
21:26hills in the powder river basin in
21:29wyoming
21:32known as the pumpkin buttes they stand
21:35tall
21:36in an otherwise wide empty landscape
21:41hidden behind the horizon are the
21:42bighorn mountains
21:44the nearest range of the rockies
21:48these hills are not formed from solid
21:50rock but a collection
21:52of rubble
21:58this rock which we find all over the top
22:00of pumpkin buttes in wyoming
22:02is a granite the closest granite we find
22:05to this area is the big horn mountains
22:07nearly 100 miles to the west
22:10the round shape of the granite rocks is
22:13further proof that they traveled
22:14from afar tumbling downhill in rivers
22:18and landslides
22:19rounded them on their journey over
22:21millions of years
22:24this was a crucial step in the
22:26investigation tracing the missing rock
22:29from the early rockies
22:30[Music]
22:32rock and cobbles eroded down from the
22:35bighorn mountains
22:36and filled up the basin to at least a
22:39thousand feet
22:40the height of the pumpkin buttes pumpkin
22:43buttes are unique because
22:45this used to be the actual surface level
22:48of the basin
22:49itself the rest has been eroded away
22:52a thousand feet of sediment to the basin
22:55that we see now
22:58but the rubble found here is nowhere
23:00near enough
23:01to have covered the owl creek mountains
23:05mclaughlin traveled to darton's peak 100
23:08miles west
23:09in the bighorn mountains on a cliff
23:129000 feet high he finds granitic
23:15cobbles that are strikingly similar to
23:18the ones on the pumpkin buttes
23:20they too are from the core of the rocky
23:23mountains
23:26the core of the rocky mountains are made
23:27extensively of granite
23:29much like what you see here these are
23:32from the bighorns that have been
23:33transported down rolled
23:35and smoothed along their way to create
23:37these smaller boulders and cobbles
23:41this is strong evidence that cobbles
23:44eroding from the rockies filled in the
23:46basins and valleys to at least
23:479 000 feet slowly burying the mountains
23:51under their own debris
23:53where once the mighty rockies stood
23:56there was now
23:57a gray barren plain with only the peaks
24:00of the old mountains piercing the
24:02surface
24:06the same process has happened in other
24:08mountain chains too
24:10there is evidence that the european alps
24:13were also cut in half
24:14by erosion at their base
24:18scientists found hills formed out of
24:20millions of tons of rock
24:22that had cascaded down and reduced their
24:25height
24:28but the story of the eroding rockies
24:30wasn't over yet
24:33after erosion turned the landscape into
24:36a gray cobble field
24:38another disruption happened evidence for
24:41this
24:41is a layer covering the top of the
24:44cobbles
24:46it's very light it's very fine grain
24:48it's actually a volcanic ash as you can
24:50see it's made of
24:50very very fine-grained sediments
24:52compared to this boulder conglomerate
24:55which is made of big hunks of rock it
24:58sits directly on top of this unit
25:00and it was laid horizontally from mostly
25:03asphalt
25:06this fine-grained ash suggests huge
25:09volcanic eruptions nearby
25:12they spewed out thick clouds of hot air
25:14ash
25:15and volcanic rock which settled on the
25:17ground
25:20radiocarbon dating the rock revealed
25:22that it happened 25 million years ago
25:26ash was deposited as it came out of the
25:29sky as plumes
25:30most of it came from the west and was
25:32deposited in
25:33basins across wyoming after the lower
25:36rockies were buried by their own rock
25:39volcanic ash settled on top and covered
25:42the area with a thick
25:43white sheet
25:47at the time of the deepest basin fill of
25:49this volcanic material
25:51all you would see in this area was be
25:52the very tops of the peaks exposed the
25:54rest would be large extensive
25:56lateral ash sheets
25:59erosion and volcanism completely
26:01transformed the terrain
26:03and buried the rockies but then
26:06over millions of years rivers flushed
26:09out the eroded rock
26:11most of it is thought to have ended up
26:13in the missouri and mississippi rivers
26:15from where it was transported into the
26:17sea
26:19what's left are the mountains we see
26:22today
26:24this also confirmed the theory
26:26geologists had about the formation of
26:28wind river canyon
26:30the incredible amount of infill buried
26:32the owl creek mountains
26:34wind river flowed on top and began
26:37carving into the mountains
26:38creating the canyon we see today
26:45the investigation into what happened to
26:48the early rocky mountains reveals
26:49two major clues granite found on the
26:53pumpkin buttes is evidence that the
26:55early rockies dumped their eroded rock
26:58into the basins wind river canyon
27:02cutting straight through the owl creek
27:04mountains
27:04is evidence that the rockies were buried
27:06by their own debris
27:09the once mighty rockies had now been cut
27:12down to nearly half their original size
27:15but the story was far from over
27:19before they became the mountains we know
27:21today they would have to endure an even
27:24greater assault
27:34years ago a great inland sea disappeared
27:37and the rocky mountains emerged from the
27:39sea floor
27:4160 million years ago they reached their
27:43peak height
27:44twice what it is today then
27:48for millions of years the rockies slowly
27:51eroded away to half their original
27:53height
27:53until three million years ago another
27:56dramatic chapter in their story began
27:59that would transform them into the
28:00mountains we know today
28:06[Music]
28:10geologist and photographer bob anderson
28:12takes to the air
28:14he is looking for clues that will tell
28:16him how the mountains have evolved
28:20first he flies over boulder canyon in
28:22the colorado rockies
28:25[Music]
28:26it is an area that has remained almost
28:28unchanged over millions of years
28:32so this is boulder canyon we're flying
28:33up right now
28:35and you can see how the river has in
28:38size
28:39maybe a few hundred feet down into
28:42otherwise relatively rolling
28:44terrain
28:48the mountain peaks that existed on the
28:50young rocky mountains were rounded off
28:53as rivers and streams eroded the rock
28:58it's this rolling terrain that that the
29:01landscape
29:01looked like in the aftermath of the
29:04mountain building event that ended about
29:0650 million years ago
29:10but as anderson climbs higher to long's
29:13peak in the rocky mountain national park
29:15the terrain changes instead of rolling
29:19hills
29:20there are rugged mountains with steep
29:22jagged cliffs
29:24it's evidence that another force has
29:26been at work
29:28the most famous of these cliffs is the
29:31diamond
29:32named for its shape it's a vertical wall
29:35with a sheer
29:36900-foot drop the summit
29:39about 45 000 square feet is the same
29:42size as a football field
29:45well we're flying beside long's peak
29:48one of the biggest climbing challenges
29:51in the rockies
29:52first century it's been a climbing mecca
29:56it's a gorgeous intact piece of rock
30:01this awesome wall is the most difficult
30:04climb
30:04in the whole of the rockies and since it
30:06was officially open to climbers in 1960
30:09has claimed over 50 lives
30:16back on the ground anderson is looking
30:18for evidence that will reveal the
30:20processes
30:21that shaped the jagged peaks
30:25on a hillside he finds mysterious large
30:28boulders scattered across the valley
30:30floor
30:33a closer look uncovers some secrets
30:36about their origin
30:39i'm standing in front of a rounded
30:41boulder that itself is sitting on
30:43a smooth bedrock outcrop
30:47both the boulder and the outcrop are
30:49covered in lichen here
30:51of green to black to gray colors
30:55and therefore i had to whack off a piece
30:57of the rock in order to see inside the
30:59rock
31:00and indeed it is different the minerals
31:02that i see and the texture of the rock
31:04is different from the underlying rock
31:06and therefore the rock is a foreign to
31:08this particular site
31:12anderson searches the ground for more
31:14clues as to how this massive boulder got
31:17here
31:18nearby he finds a smooth surface with
31:21very fine scratch marks
31:25i'm sitting on a polished surface this
31:28little piece right here
31:29is smooth to the touch and if i look at
31:32it in a certain way that the
31:34light glints off of it just right i can
31:36see that there are scratches running in
31:38this direction across the surface the
31:40only force
31:41that could have produced these fine
31:43parallel scratches on the rock
31:45is ice and lots of it
31:50it's a clue that a massive glacier once
31:53filled this valley
31:56and that tells me that the glacier came
31:58down valley came across this surface
32:01and eroded it each one of these
32:03scratches corresponds to a sand grain
32:06embedded in the sole of the ice
32:08that just like sandpaper smooths off the
32:10surface so
32:11zillions of sand grains over thousands
32:14of years
32:15will have eroded this surface smooth
32:19as glaciers flowed down the valley they
32:21picked up
32:22rocks and grit the ice
32:25pushed down on these cutting tools with
32:27the weight of over a thousand
32:29fully loaded garbage trucks
32:32it left scratch marks all over the
32:34rockies up to a thousand feet high
32:38this is evidence that a massive wall of
32:40ice
32:41covered this part of the rockies and
32:43shaped the mountains
32:45the ice ripped out the rock from the
32:47valley walls and left behind the jagged
32:50cliffs
32:51and rugged edges
32:56the last few million years perhaps three
32:58million years glaciers have come
33:00and gone from the rocky mountains and
33:02every time they come across the
33:04landscape
33:04they're capable of eroding that
33:06landscape at rates that are
33:08perhaps fractions of an inch per year
33:12meaning that over the course of one
33:13glacial
33:15cycle you perhaps erode 10
33:1820 feet of rock
33:21ice also created the broad canyons
33:25with every ice age new glaciers ground
33:27their way down v-shaped river valleys
33:30and turned them into broad u-shaped
33:32canyons
33:37for the glacier the whole valley is its
33:39channel
33:40so any place where the glacier touches
33:42the wall it's capable of eroding it
33:45and therefore the walls will be made
33:47more vertical on the edges
33:49and be flattened on the base until it
33:51gets to now a u-shape
33:53which then propagates downward
33:56ice also explains the presence of these
33:59boulders
34:01they hitchhiked at the bottom of a
34:03glacier down the frozen
34:05valley when the last ice age came to an
34:08end
34:09and the glaciers melted about 10 000
34:11years ago
34:12the boulders were left behind
34:17scientists had found two pieces of
34:20evidence that were responsible for the
34:22jagged looks of the rockies today
34:24a solitary boulder foreign to the area
34:27could have only been transported here by
34:29ice
34:31striations showed scientists that a
34:33glacier at least a thousand feet thick
34:36covered the rockies ice was responsible
34:39for the dramatic shape of the rockies
34:41today
34:42but the mountains keep evolving recently
34:45scientists discovered
34:47alarming evidence that they may collapse
34:49into a deep rift
35:03compression erosion and ice have
35:05sculpted the rocky mountains to their
35:07present formation
35:09but the geology that created this
35:11impressive mountain range
35:13has also the potential to destroy it
35:17over the last 25 million years a
35:19gigantic rift
35:21has been opening up at the southern end
35:22of the rocky mountains
35:25it stretches over 160 000 square miles
35:28and is known as the rio grande valley
35:32geologists are eager to investigate how
35:34this giant rifting valley could affect
35:37the future of the rockies
35:41they find their first lead in san ysidro
35:44new mexico
35:45north of albuquerque
35:48the area is dominated by bright yellow
35:51porous rock
35:52known as travertines
35:56curiously geologists think this rock
35:58forms from
35:59water this water has some uh
36:04unusual characteristics that is this
36:06this water is capable of
36:07precipitating or depositing a new rock
36:10called travertine
36:11it's like kind of like the scale in your
36:13teapot
36:16travertine rock is made out of calcite
36:19the same material that builds up lime
36:21scale
36:24these rocks grow very rapidly some
36:27enlarge by a few inches per month
36:30about a liter of the water will be able
36:32to drop out
36:33or precipitate a little pile of calcite
36:36about as big as an aspirin tablet
36:40like lime scale building up in a hot
36:42water kettle
36:43travertines form around warm springs
36:46[Music]
36:48measurements confirm that water
36:50temperature around the travertines is
36:52roughly 77 degrees
36:56besides the ability to build rock this
36:59hot water has
37:00more secrets to tell
37:04laura crossy and carl carlstrom have a
37:07hunch that the water is warmed up
37:09by heat from the earth's interior rising
37:12up through cracks in the rock
37:15they form as the rift valley pulls apart
37:20climbing down a cave 25 feet below the
37:22surface
37:23they are hoping to find further evidence
37:26[Music]
37:28the water contains microbes they are
37:32microscopically small
37:33organisms most of them consist of only
37:36one
37:37cell when scientists analyze their genes
37:41in the lab
37:41they found something remarkable what we
37:44found in springs like this
37:46by doing the dna analysis is that the
37:48microbes that are coming up these
37:50faults are much more like what we find
37:53at mid-ocean ridges
37:54than like the rivers and streams we
37:56would expect in a continental setting
37:59mid-ocean ridges are very long mountain
38:02chains
38:02under the sea just like the rift valley
38:05they also form in geologically active
38:08areas
38:09where lava constantly erupts and builds
38:11up
38:12new crust any living organism
38:15surviving down there has to be able to
38:17cope with these hot conditions
38:21the springs here and the mid-ocean ridge
38:23settings are also characterized by the
38:25upwelling of deep
38:26hot fluids from within the earth
38:28indicating that these both are
38:30connected to that deep tectonic setting
38:33the microbes suggest deep tectonic
38:36forces
38:36are at work but there is even more
38:39compelling
38:40evidence carlstrom and crossy find an
38:43unusually
38:44high amount of gas bubbling up through
38:46the water
38:47these samples are kind of fun because it
38:49looks like an empty glass vial but it
38:51started out full of water
38:52and then we filled up the turn it upside
38:54down in the water and the gas
38:56displaced the water until it's full of
38:58gas a lab analysis identifies the gas
39:01as helium this is the conclusive
39:03evidence that deep tectonic forces are
39:05at work here
39:07the helium is the is the interesting
39:09most interesting gas for us it's the
39:11smoking gun of evidence for for
39:14where these fluids have come from
39:16there's two forms of helium but it's the
39:18helium-3 that we're most interested in
39:21and that
39:21form of helium is only derived from the
39:24earth's mantle
39:26the mantle is a part of the earth's
39:28interior 30 miles below the surface
39:30it is made up of hot molten rock
39:34in areas where magma moves up pressure
39:37on top of it decreases
39:38and gases such as helium are released
39:43they find their way through faults and
39:44cracks until they reach the surface
39:49so helium gas is conclusive proof that
39:52geological forces deep under the earth
39:54are building up
39:56and the effect it will have on the
39:58rockies is devastating
40:01the rio grande rift is an area that's
40:04tectonically active
40:05in a different way than you think of
40:07building of mountains this area is
40:10the next stage in the life sometimes of
40:12a mountain belt where it
40:14starts to collapse it starts to extend
40:17as hot magma surges upwards from 30
40:20miles below the surface
40:21it forces the area on top to spread
40:25the surface stretches and thins and
40:28opens up a deep chasm
40:31as the rift opens the mountains to each
40:33side crumble
40:34into the valley
40:38you can think of a piece of taffy that's
40:41being stretched and it might break on
40:42the top
40:43and those breaks would lower uh pieces
40:46of the they would drop down
40:48and then once you have a uh what's
40:50called a fault valley
40:52then the sediments wash in from the high
40:55mountains it's an immense structure it's
40:57it's about six miles deep it's about as
41:00deep as mount everest is high
41:02but it it's when you drive across it or
41:04you look at it
41:05from any vantage point it's you don't
41:08see that entire
41:10depth because it's all been filled with
41:11sand and gravel progressively as
41:13the extension took place today the rio
41:16grande rift
41:17stretches over 160 000 square miles
41:21from mexico in the south where it's
41:23broadest to colorado in the north
41:26where it's only just begun to open up
41:28this rift is propagating northwards
41:30into the higher colorado rockies what's
41:33going to happen to colorado those
41:35mountains will
41:36probably collapse by rifting as the rift
41:39propagates
41:40zippers northward and you can you can
41:42visualize that
41:43what's now in colorado is more similar
41:46to what was in new mexico
41:48before the rio grande rift opened and
41:50before the mountains
41:51collapsed looking ahead in the distant
41:55future there could be challenging times
41:58the tectonic forces that created the
42:00rockies could eventually lead to their
42:02destruction
42:04when we think about the great
42:05continental rifts of east african and
42:08rio grande rift the question arises is
42:11the continent going to split apart here
42:13is that if this rifting carries on are
42:14we going to have beachfront property
42:17right here in new mexico and the
42:20realtors are very interested in this but
42:22so are the geologists
42:24the formation of the rocky mountains is
42:26a remarkable story
42:3070 million years ago the death of
42:32ancient ammonites marked the rise of the
42:34rocky mountains from the retreating
42:36inland sea 60 million years ago
42:40leaves with jagged margins grew on the
42:42mountains that were twice
42:44as high as today ten thousand years ago
42:48a solitary boulder marked the retreat of
42:50the last glacier
42:51that sculpted the rockies and helium gas
42:55in the rio grande valley today is a clue
42:57that the area deep under the surface is
43:00active again
43:04if rifting continues and the rio grande
43:07valley widens
43:08the area of the rocky mountains could
43:10one day rip apart
43:13a new sea would move in like the vast
43:16inland sea that covered the area 70
43:19million years ago
43:21the rocky mountains the great backbone
43:24of north america
43:25would slowly disappear and the continent
43:29would once more
43:30split living proof that the earth
43:34is never at rest
43:58you

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