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The Grand Canyon-
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a colossal labyrinth of towering buttes
and deep sided canyons.
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For over a century,
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scientists have puzzled
over how one small river
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could cut such a deep slice
through the earth.
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The Grand Canyon formed
through processes deep within the earth
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invisible to the eye.
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Today new discoveries point towards
new answers-
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Scientists are on the brink
of understanding the geological forces
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that created one of the natural wonders
of the world- the Grand Canyon.
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It's a landmark so immense
that you can see it from space.
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277 miles long, up to 18 miles wide
and one mile deep-
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The Grand Canyon
is one of the deepest chasms on Earth.
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Its walls plunge sheer
into the Earth's crust.
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The Colorado River sliced through
2 billion years of our planet's history
in less than 5 million years,
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exposing layer after layer
of geological time.
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The first humans walked here
thousands of years ago.
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Since then the canyon has inspired awe.
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How did it come to be here
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and what secrets lie hidden in its walls?
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To many Native Americans
this land is sacred.
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They have revered the canyon
for centuries.
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The canyon is a very spiritual
and powerful place.
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Our legends say that we actually
came from the bottom of the canyon.
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Scientists like senior geologist
John Spencer
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consider the Canyon
a treasure- and a mystery.
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It's a bit startling,
because all around it it's very flat
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and you can be 100 feet
from the edge of the canyon
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and think this is a rather boring landscape
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And then you walk over
and look into the canyon
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and all of a sudden
there's this monster canyon in front of you
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The layers of rock in the canyon walls
formed over thousands of millions of years
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The deeper you go,
the further back in time you travel.
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At the top the newest rocks,
at the bottom the oldest.
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The Grand Canyon appears
to be upside down.
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On top, fossils from an ancient sea.
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At the bottom,
remains of an old mountain range.
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Karl Karlstrom, geology professor
at the University of New Mexico
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is an expert on the oldest rocks
of the canyon- one mile down.
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They reveal what the Southwestern US
looked like two billion years ago.
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We were interested in what's the oldest
chapter of Grand Canyon history.
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And these rocks
are so spectacularly exposed
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that we have the opportunity
to study the earliest history
in the Grand Canyon.
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What's strange about these rocks
at the bottom
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is that they are part
of an ancient mountain range-
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now buried under thousands
of feet of rock.
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They are the remains
of a range called the Vishnu Schist,
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a layer of metamorphosed rock that
dates from around 1.7 billion years ago.
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The human eye sees a line of rock.
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Karlstrom's instruments
see evidence of a mountain range
that once towered six miles above.
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His techniques bring the past back to life
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His clue is the minerals in the rocks
that change chemical composition
under pressure.
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More rock on top means
more pressure on the rock below.
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This forces a mineral in the rock, garnet,
to take up more calcium.
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The higher the calcium concentration
within the garnet
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the brighter it looks
under a microscope.
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This tells scientists
how deep a rock was buried.
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We have learned that these rocks
were buried to great depth
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and the amount of pressure
that they experienced
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was equivalent
to about six miles of rock above them.
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Karlstrom's findings
have helped other geologists
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visualise how this area
may have looked 1.7 billion years ago.
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Ron Blakey is a professor of geology
at Northern Arizona University in Flagstaff.
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He studies ancient continents
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and discovered that California
wasn't always America's West coast.
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It's very likely that
the coastline of North America
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at this period of time
was just south of Wyoming,
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perhaps along the Wyoming/Colorado border
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and extended up into the Lake Superior
region and then up into Canada.
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So I would say that perhaps only
half to two thirds of North America
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had been built at that period of time.
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The Vishnu mountains stretched across
a very different landscape-
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the south of North America
did not exist as we know it today.
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The mountains towered up
out of an ocean along the ancient coast.
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They eventually became part
of the North American continent
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and formed the basement rocks
of the Grand Canyon.
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I imagine
it looked like a bit of a train wreck
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where each of these island chains
was perched offshore.
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A series of island chains
that had substantial mountains
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but fairly high peaks like in the Aleutians
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Six miles beneath the summits
of these mountainous islands,
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the rocks were developing
that distinctive calcium signature.
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The mountains above didn't last long.
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In around 500 million years,
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erosion ground them down
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until all that was left
was this at the bottom-
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the Grand Canyon's most ancient layer.
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As we rise up the side of the canyon,
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we travel forward in time.
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Each foot takes us closer
to the present day-
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and each period
has its own history.
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Over hundreds of millions of years
the landmasses continually change shape.
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Forces deep inside the earth
cause continents to break apart,
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drift away and form new ones.
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Deep trenches open up beneath the ocean
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Sea levels change
and flood low-lying areas.
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At least eight separate seas
have flooded this area
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since erosion cut down
the Vishnu Mountains.
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They covered the land,
stayed for a few million years
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and retreated again.
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The evidence is here-
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nearly two and a half thousand feet
above the modern Colorado River
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and five and a half thousand feet
above present-day sea level...
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These are the remains of oyster beds
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that flourished here
nearly 100 million years ago.
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The Cretaceous sea stretched from Kansas
in the east to Nevada in the west,
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from Mexico in the south
to the Arctic in the north.
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It was a shallow seaway
that covered much of the continent.
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Sea creatures sank
to the bottom of the ocean
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and fossilized in a thick,
grey layer of mud.
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Scientists call it the Tropic Shale.
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Wayne Ranney is fascinated
by this region, rich in fossils.
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It gives him a clear idea
of this area's history.
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This oyster bed, which contains
millions of oysters
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is from a sea that
was a shallow sea that covered
the interior of North America
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between about 80 and 90 million years ago
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Oysters weren't the only creatures
living in this ancient sea.
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Life was abundant.
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Sharks, turtles and ammonites
also inhabited the waters.
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Today, as erosion slowly wears away
the layers of rock,
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new fossils appear.
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And in 2005,
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just 70 miles away
from the edge of the canyon,
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palaeontologists found the well-preserved
skeleton of a plesiosaur...
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a dinosaur-like, fish-eating reptile.
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For David Gillette
it was a dream come true.
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He is a curator of palaeontology
at the Museum of Northern Arizona
in Flagstaff.
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For a vertebrate palaeontologist,
like myself,
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finding plesiosaur skeletons
like we're finding in the Tropic Shale,
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is almost a once in a lifetime experience
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The one in front of me was a plesiosaur
that was about half-complete,
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we found the front half of the body
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and that's more exciting
almost than anything I can imagine.
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Plesiosaurs were sea-going reptiles.
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They were last seen
about 65 million years ago
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when a catastrophic mass extinction
hit the earth.
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Gillette's Plesiosaur
dates back much earlier.
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It lived around 90 million years ago.
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Clear proof that this area
was under the sea at that time.
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The seas left deposits of mud, sand
and the remains of living creatures.
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Sea currents moved this material
which then settled.
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And over time the deposits
turned into layers of sedimentary rock.
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Ron Blakey explains.
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What I am going to show you now
is a form of sedimentation.
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I have here a glass cylinder
that's filled with water and sediment,
mostly sand
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and what I'm gonna do
is shake this up,
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and the shaking up
provides energy
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that allows the sand grains
to move around this cylinder of water,
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and then when I set it down
that energy is removed
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and the grains
will immediately settle out.
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Let's see what happens...
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As you can see the coarsest grains
have already settled out
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and finer grains
and finer grains are settling,
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and now most of the sand is out,
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the water is still cloudy
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because there is some fine material
still in suspension within this cylinder.
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But all the energy of the system
has been removed
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and so now even the finest grains over time
will settle out to form a layer of sediment
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This process demonstrates how
sedimentary layers built the Grand Canyon
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Over the course of time,
the glass cylinder turned many times.
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And when the seas come and go
this is all that remains.
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Millions upon millions
of years of sediment
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compressed over time
to form layers of rock-
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the building blocks of the Canyon.
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But powerful forces
were building deep underground.
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Forces that would thrust
these rocks a mile into the sky.
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We are on a journey to discover
the geological processes
that created the Grand Canyon
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We are in the cretaceous period-
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where plesiosaurs
hunted in the shallow seas
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that covered the area near to
where the Grand Canyon is now.
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Seas flooded and retreated
over this area for millions of years,
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overlaying the ancient Vishnu Mountains
with two miles of sedimentary rock.
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Half of that has since eroded away,
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to leave today's canyon, one mile deep.
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The next major transformation will
push the land several thousand feet
into the air.
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Deep beneath the earth
a monumental force builds up.
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It is one of the greatest forces on earth-
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the gigantic power
of colliding tectonic plates.
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Over millions of years
the planet's surface changes.
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Scientists explain the process
using the theory of plate tectonics.
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The surface of the earth
is made up of a series of large plates.
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They float on the soft, plastic part
of the earth's mantle.
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The inner core of the earth
may reach over 12,000 degrees.
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00:13:21,300 --> 00:13:25,750
Heat escaping from the core
creates convection currents
in the next layer-
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the lower mantle-
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pushing the plates
slowly across the surface.
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Scientists call it continental drift.
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Over time, whole plates move apart
and crash back into each other,
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shaping and reshaping our world.
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Scientists believe that
these colliding tectonic plates
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were instrumental in creating
the Grand Canyon.
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Around 130 million years ago
193
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the oceanic plate began to collide
into the western edge
of the North American plate.
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Oceanic plates are 30-60 miles thick
and lie beneath the sea.
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They consist of dense basalt
and get pushed down.
196
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Continenal Plates
are mostly granite and lighter.
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Oceanic plates subduct underneath them
when they collide.
198
00:14:22,300 --> 00:14:26,050
So when the oceanic plate
hit the lighter north American plate,
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the oceanic plate moved
under the west coast of America.
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00:14:32,400 --> 00:14:37,750
Over tens of millions of years the
continental crust compressed and thickened
201
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As the oceanic plate thrust downwards,
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the whole of the west of America
lifted slowly upward.
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As the land rose, the sea retreated,
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creating the landmass we see today.
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The collision dragged down
portions of the leading edge
of the continental crust.
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Beneath the surface it melted
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and liquid rock pushed up
through the crust.
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00:15:02,600 --> 00:15:05,550
The Rocky Mountains formed in the north
209
00:15:06,400 --> 00:15:12,550
In the south a range of ancient mountains
the Mogollan Highlands grew higher.
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00:15:14,500 --> 00:15:17,850
The area that today
is the Colorado Plateau
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rose about one mile,
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lifting the ancient sea floor
to where it is today-
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00:15:23,800 --> 00:15:27,550
seven thousand feet
above our present sea level.
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00:15:30,200 --> 00:15:32,850
So what do we see when we
look in the Grand Canyon?
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00:15:34,200 --> 00:15:38,750
When we have marine rocks now
exposed at seven thousand feet
above sea level
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00:15:38,800 --> 00:15:41,050
there is a big question here,
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did the sea fall that far
or was the land uplifted that far?
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Well clearly after the marine rocks
were deposited in the sea
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that formed the rim of the Grand Canyon,
220
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the area had to be uplifted.
221
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The region of the Grand Canyon
was now high above sea level.
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But at this point
it was an unbroken plain.
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There was no canyon.
224
00:16:09,000 --> 00:16:14,350
Making the canyon took another force
of nature- erosion.
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00:16:14,400 --> 00:16:16,350
Even as the land rose up,
226
00:16:16,400 --> 00:16:21,250
a river flowed across the plain,
and began to cut down through the rock
227
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Here we have a colourful layer cake,
228
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which represents the rock formations
on the Colorado Plateau
in the Grand Canyon region
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00:16:29,100 --> 00:16:32,350
and the river itself
is represented by this knife.
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00:16:32,400 --> 00:16:35,450
Now as the Colorado Plateau
is uplifted
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the river chisels its way down through
and actually makes a cut,
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00:16:39,800 --> 00:16:43,550
which is... I made a canyon.
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00:16:44,400 --> 00:16:46,250
70 million years ago
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water and snowmelt flowed
from the Mogollan highlands
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00:16:50,000 --> 00:16:53,450
onto the surface
of the future Colorado Plateau.
236
00:16:53,500 --> 00:16:56,750
They began slowly cutting
into the plateau area.
237
00:16:57,500 --> 00:17:00,150
Ron Blakey demonstrates
how flowing water
238
00:17:00,200 --> 00:17:04,750
can cut through the layers
of sedimentary rock to make a canyon.
239
00:17:04,800 --> 00:17:07,350
When I cut a hole
in the side of the tub
240
00:17:07,400 --> 00:17:11,150
we are going to see the sediment
is going to be eroded.
241
00:17:11,200 --> 00:17:12,950
Let's see if this works.
242
00:17:14,700 --> 00:17:17,950
There you can see
the erosion taking place.
243
00:17:18,000 --> 00:17:20,350
As I lower the base level
244
00:17:20,900 --> 00:17:23,650
by cutting a part of the plastic tub
245
00:17:23,700 --> 00:17:28,050
you can see the water coming down
through the sediment and exposing it.
246
00:17:29,100 --> 00:17:31,350
So if erosion cut through the rock
247
00:17:31,400 --> 00:17:36,850
the next part of the puzzle
is to find the ancient river
that created the canyon.
248
00:17:38,300 --> 00:17:41,050
Some of the old riverbeds
are still visible.
249
00:17:41,100 --> 00:17:44,350
But they pose more questions
than the answer.
250
00:17:45,800 --> 00:17:51,250
Richard Young Professor of geology at
the State University of New York at Geneseo
251
00:17:51,300 --> 00:17:56,250
has been trying to solve the riddle
of the old river beds
since he was a grad student.
252
00:17:56,500 --> 00:17:59,050
Young pieces together
the history of rivers
253
00:17:59,100 --> 00:18:03,450
by looking at the shape and composition
of rocks found on river beds.
254
00:18:04,200 --> 00:18:08,250
The modern Colorado River flows
from the Rocky Mountains in the East
255
00:18:08,300 --> 00:18:11,950
to the Gulf of California
in the Southwest.
256
00:18:12,000 --> 00:18:14,750
But as Young investigated
the ancient canyons
257
00:18:14,800 --> 00:18:17,550
he found that something
just didn't add up.
258
00:18:18,000 --> 00:18:20,650
It was a shock for a student
who just is getting started
259
00:18:20,700 --> 00:18:23,350
and you want to believe
what your professors are telling you,
260
00:18:23,400 --> 00:18:27,850
but everything you see
out in the field says that something
very different is happening.
261
00:18:31,900 --> 00:18:34,650
To us, these look like big pebbles.
262
00:18:34,700 --> 00:18:37,550
To geologists they're a missing link.
263
00:18:37,900 --> 00:18:40,450
We see two things,
we see how round they are,
264
00:18:40,500 --> 00:18:42,250
which indicates how far they have come
265
00:18:42,300 --> 00:18:45,650
and secondly the rock types
are completely foreign to this area
266
00:18:45,700 --> 00:18:48,550
and they come from at least
a hundred miles away from here.
267
00:18:49,000 --> 00:18:53,550
The old stream pebbles are not native
to the region where Young found them.
268
00:18:54,100 --> 00:18:58,450
They came from around 100 miles
southwest of the plateau.
269
00:18:59,500 --> 00:19:02,050
The old river
must have transported the pebbles
270
00:19:02,100 --> 00:19:06,550
from central Arizona
north and west to the Plateau region.
271
00:19:06,900 --> 00:19:09,650
The orientation of the pebbles
in the river bed
272
00:19:09,700 --> 00:19:12,450
shows the direction of the water flow.
273
00:19:12,700 --> 00:19:16,350
Rivers cause pebbles to tumble
in the river channels.
274
00:19:16,400 --> 00:19:20,450
They move until they reach this position
with the current flowing this way.
275
00:19:20,600 --> 00:19:23,350
That's a stable position,
just like the shingles on a roof.
276
00:19:23,400 --> 00:19:26,650
And that tells us that the river
was flowing in that direction.
277
00:19:27,000 --> 00:19:30,150
As the ancient pebbles settled
on top of each other-
278
00:19:30,400 --> 00:19:33,850
they left a lasting record
of how the river flowed.
279
00:19:34,800 --> 00:19:38,650
This was strong evidence that
the rivers had to have flowed northeast-
280
00:19:38,700 --> 00:19:41,350
the opposite direction to today.
281
00:19:42,600 --> 00:19:45,950
But not only did the water
flow in the opposite direction,
282
00:19:46,000 --> 00:19:51,150
it also in a different canyon
4 miles south of western Grand Canyon.
283
00:19:52,800 --> 00:19:55,350
The old channel is now empty.
284
00:19:55,700 --> 00:19:57,450
What happened?
285
00:19:59,600 --> 00:20:01,550
Deep within the earth's core,
286
00:20:01,600 --> 00:20:04,650
powerful forces
were about to shatter the surface
287
00:20:04,700 --> 00:20:07,750
of what will become the Grand Canyon.
288
00:20:10,800 --> 00:20:12,850
About 20 million years ago
289
00:20:12,900 --> 00:20:17,750
the Oceanic Plate began moving north
relative to the North American Plate.
290
00:20:24,200 --> 00:20:28,650
Heat built up under the Mogollan
Highlands south west of the Canyon.
291
00:20:34,500 --> 00:20:38,050
The earth's crust began stretching.
292
00:20:40,500 --> 00:20:45,450
Over millions of years,
vast areas of land deformed and cracked,
293
00:20:45,500 --> 00:20:48,650
sheared upward or snapped down.
294
00:20:49,100 --> 00:20:52,250
The Mogollan Highlands
fell thousands of feet.
295
00:20:52,300 --> 00:20:55,450
Huge basins appeared on low-lying land.
296
00:20:55,500 --> 00:20:59,850
Today geologists call it
the Basin and Range Province.
297
00:21:00,000 --> 00:21:03,150
Wayne Ranney uses dominoes to explain.
298
00:21:03,300 --> 00:21:08,150
Once faulting begins
we tilt all the fault blocks
down on individual faults
299
00:21:08,200 --> 00:21:12,350
and you can see the surface tilting back
in the Colorado Plateau edge.
300
00:21:15,200 --> 00:21:19,650
Rock layers that were once horizontal
are now almost vertical.
301
00:21:19,700 --> 00:21:22,150
The region tilted- and then collapsed.
302
00:21:22,200 --> 00:21:26,750
Ancient history is written
in the orientation of every outcrop.
303
00:21:27,500 --> 00:21:30,550
The collapse re-drew the topography
of the region.
304
00:21:31,100 --> 00:21:33,650
Before, the highlands to the south
305
00:21:33,700 --> 00:21:37,350
towered several thousand feet
over the Colorado Plateau.
306
00:21:38,300 --> 00:21:39,450
After the collapse
307
00:21:39,500 --> 00:21:43,350
the Basin and Range area
was almost half a mile lower.
308
00:21:43,800 --> 00:21:46,850
It was a major piece
in the scientific puzzle.
309
00:21:47,000 --> 00:21:51,950
The rivers may have changed direction
because the whole landscape changed
310
00:21:52,500 --> 00:21:56,350
When the basin and Range
faulting occurred it dropped that area,
311
00:21:56,400 --> 00:21:59,250
it made it actually lower
than the Colorado Plateau.
312
00:21:59,300 --> 00:22:02,450
And that's the reason that the rivers
were able to change direction
313
00:22:02,500 --> 00:22:05,350
and flow in the opposite direction
towards California.
314
00:22:06,900 --> 00:22:11,050
Scientists think they have solved
the mystery of how the rivers reversed
315
00:22:11,300 --> 00:22:15,350
But the river was still four miles away
from where the canyon is today.
316
00:22:15,600 --> 00:22:18,650
These ancient rivers did carve canyons-
317
00:22:18,700 --> 00:22:22,850
but not where today's canyon is,
and on nothing like the same scale.
318
00:22:23,600 --> 00:22:26,850
Sometime after the collapse
a new river formed-
319
00:22:26,900 --> 00:22:28,550
the Colorado River-
320
00:22:28,600 --> 00:22:30,350
and it took a new course.
321
00:22:30,400 --> 00:22:32,950
But when- and why?
322
00:22:33,600 --> 00:22:37,650
The challenge was to find
the earliest sign of this river.
323
00:22:37,900 --> 00:22:42,450
Surprisingly, a clue came
from outside the Grand Canyon.
324
00:22:42,700 --> 00:22:44,650
In the Lower Colorado river
325
00:22:44,700 --> 00:22:48,850
about 100 miles before the river
enters the Gulf of California
326
00:22:49,000 --> 00:22:52,150
scientists discovered a tiny fossil.
327
00:22:54,000 --> 00:22:58,250
Kristin McDougall, research geologist
with the US Geological Survey
328
00:22:58,300 --> 00:23:00,250
has studied these fossils.
329
00:23:00,300 --> 00:23:02,550
They are called Foraminifers.
330
00:23:02,600 --> 00:23:06,150
Foraminifers are like specks of dust.
331
00:23:06,200 --> 00:23:08,450
It's a microscopic seashell.
332
00:23:08,500 --> 00:23:14,150
The Cretaceous
planktic foraminifers that we find
333
00:23:14,200 --> 00:23:17,750
look like three golf balls
hooked together.
334
00:23:18,600 --> 00:23:20,350
Foraminifers are tiny-
335
00:23:20,400 --> 00:23:23,150
a hundred of them
could fit on a grain of salt-
336
00:23:23,200 --> 00:23:27,150
but they could show when the river
began cutting the canyon.
337
00:23:28,300 --> 00:23:31,950
The Foraminifers are not native
in the Lower Colorado River.
338
00:23:32,000 --> 00:23:34,650
Their home was much further north.
339
00:23:34,800 --> 00:23:40,450
The only way their fossil remains
could have been deposited in sediments
in the lower Colorado River
340
00:23:40,600 --> 00:23:43,650
is when the river transported them down
341
00:23:43,900 --> 00:23:49,150
They were originally deposited
in the Cretaceous shales
342
00:23:49,200 --> 00:23:52,850
on the Colorado Plateau
north of the Grand Canyon.
343
00:23:53,000 --> 00:23:55,250
And they were eroded
344
00:23:55,300 --> 00:23:59,550
and brought down along
the modern course of the Colorado River
345
00:23:59,600 --> 00:24:01,450
and re-deposited.
346
00:24:05,300 --> 00:24:10,850
Dating the sediments where
the fossils were re-deposited
helps to solve the mystery.
347
00:24:11,200 --> 00:24:15,550
The sediments seem to have formed
when the river took its present course-
348
00:24:15,600 --> 00:24:17,150
and geologically speaking,
349
00:24:17,200 --> 00:24:19,850
it happened just an eye-blink ago.
350
00:24:19,900 --> 00:24:27,150
These Cretaceous fossils
indicate that the Colorado River
became a through-flowing river
351
00:24:27,200 --> 00:24:30,050
by at least
four and a half million years ago.
352
00:24:30,300 --> 00:24:33,150
That's a very exciting find.
353
00:24:33,200 --> 00:24:36,650
Evidence indicates that
4.5 million years ago
354
00:24:36,700 --> 00:24:41,650
the river flowed along its present course
from the northeast to the southwest.
355
00:24:41,800 --> 00:24:45,750
Scientists think they solved the mystery
of the age of the river.
356
00:24:45,800 --> 00:24:48,750
But the solution raised a new question.
357
00:24:48,800 --> 00:24:51,050
They knew when the river had formed
358
00:24:51,100 --> 00:24:53,550
but they were still not certain how.
359
00:24:56,500 --> 00:24:59,650
Most rivers begin energetically
at their source.
360
00:24:59,700 --> 00:25:01,950
They rip through the terrain downwards
361
00:25:02,000 --> 00:25:04,150
eroding anything in their path.
362
00:25:05,000 --> 00:25:07,750
Downstream, things seem calmer.
363
00:25:08,300 --> 00:25:11,450
The water moves slower,
and the channel is wider.
364
00:25:13,200 --> 00:25:14,950
But back near the source,
365
00:25:15,000 --> 00:25:20,450
the river lengthens its channel upstream
as the rushing waters erode more rock.
366
00:25:21,500 --> 00:25:23,750
They cut their channel headward.
367
00:25:24,000 --> 00:25:28,650
One theory is that the Colorado River
got started this way.
368
00:25:28,800 --> 00:25:34,050
This headward erosion usually
happens where the steepness
of a riverbed rises.
369
00:25:34,100 --> 00:25:38,050
It gives the river more energy
to cut deeper into the rocks.
370
00:25:38,100 --> 00:25:42,050
The steeper the gradient
the more rainwater channels into the river
371
00:25:42,100 --> 00:25:44,850
and the faster it pulls down the slope
372
00:25:45,700 --> 00:25:48,350
The river eats into soil and rock
at the top
373
00:25:48,400 --> 00:25:51,250
and may also lengthens
its channel headward.
374
00:25:53,100 --> 00:25:55,650
Could headward erosion
have been the mechanism
375
00:25:55,700 --> 00:25:59,650
that made the Colorado River
head out across the plateau?
376
00:26:00,000 --> 00:26:05,950
We know that the Colorado plateau
rose about a mile above sea level
70 million years ago
377
00:26:06,000 --> 00:26:10,350
creating a steep slope towards
the present-day Gulf of California.
378
00:26:11,300 --> 00:26:14,750
It's a neat explanation
but it's controversial.
379
00:26:15,000 --> 00:26:19,850
The modern Colorado River
is only around 4 1/2 million years old.
380
00:26:19,900 --> 00:26:24,550
And the plateau rose 65
and half million years earlier.
381
00:26:25,400 --> 00:26:27,650
Perhaps there was another
more recent uplift
382
00:26:27,700 --> 00:26:30,750
that would explain how the river
crossed the plateau.
383
00:26:31,000 --> 00:26:32,750
Searching for clues
384
00:26:32,800 --> 00:26:37,550
scientists discovered
a layer of rocks downstream
in the lower part of the region
385
00:26:37,600 --> 00:26:39,450
called the Bouse formation.
386
00:26:40,800 --> 00:26:43,850
These rocks are around
six million years old,
387
00:26:43,900 --> 00:26:47,750
and some parts are nearly
2,000 feet above sea level.
388
00:26:48,000 --> 00:26:52,550
When scientists took a closer look
and discovered marine fossils in the rock
389
00:26:52,600 --> 00:26:55,750
they knew they were onto
something extraordinary.
390
00:26:58,000 --> 00:27:02,150
There are three key fossils
that we find in the Bouse Formation,
391
00:27:02,200 --> 00:27:04,350
the first is a planktic foraminifer
392
00:27:04,400 --> 00:27:07,450
which is one of the ones that
floats on the surface of the water
393
00:27:07,500 --> 00:27:10,850
and then there is a specimen
called ammonia
394
00:27:10,900 --> 00:27:13,150
and it's a very shallow water foram.
395
00:27:13,200 --> 00:27:18,150
And then there's a third kind
that lives much deeper in the ocean.
396
00:27:18,800 --> 00:27:23,250
The fossils meant the rock layer
is likely to have formed in seawater.
397
00:27:24,000 --> 00:27:25,950
For Dr. Ivo Lucchitta,
398
00:27:26,000 --> 00:27:29,150
the fossils led to a new theory
of what had happened here.
399
00:27:30,500 --> 00:27:33,850
He believes that when the Gulf
of California first opened up,
400
00:27:33,900 --> 00:27:38,350
it extended about 100 miles
further north than it does today.
401
00:27:39,000 --> 00:27:42,050
Dead marine organisms
sank to the sea bed
402
00:27:42,100 --> 00:27:45,550
and became entombed
in the white sedimentary deposit-
403
00:27:45,600 --> 00:27:46,950
the Bouse Formation.
404
00:27:47,500 --> 00:27:51,150
Yet today, the fossils
are hundreds of feet above sea level.
405
00:27:51,400 --> 00:27:54,150
That was the clue that
he had been searching for.
406
00:27:54,300 --> 00:27:59,450
One day by looking at
the present distribution elevation
of remnants of the Bouse
407
00:27:59,500 --> 00:28:02,050
it occurred to me that
the Bouse and the land with it
408
00:28:02,100 --> 00:28:06,750
had been uplifted
as much as perhaps 1700 feet
in the last 5 million years.
409
00:28:10,200 --> 00:28:14,250
He believes that this area was uplifted
to its current elevation
410
00:28:14,300 --> 00:28:18,550
after the fossils were deposited
around 6 million years ago.
411
00:28:18,800 --> 00:28:23,850
And this second uplift
created an ideal scenario
for headward erosion.
412
00:28:23,900 --> 00:28:25,850
By uplifting the plateau
413
00:28:25,900 --> 00:28:31,750
you basically steepen
the gradient of the river
as it emptied into the Gulf
414
00:28:31,800 --> 00:28:34,550
and therefore allowed them
to erode more rapidly.
415
00:28:35,500 --> 00:28:38,350
The trouble is, not everyone agrees.
416
00:28:38,400 --> 00:28:41,950
The apparent existence of marine
fossils in the Bouse Formation
417
00:28:42,000 --> 00:28:44,050
1000 feet above sea level
418
00:28:44,100 --> 00:28:48,150
is not irrefutable evidence
that the area was uplifted.
419
00:28:48,400 --> 00:28:52,650
Senior geologist John Spencer
from the Arizona Geological Survey
420
00:28:52,700 --> 00:28:55,650
is not convinced
about the second uplift theory.
421
00:28:56,000 --> 00:29:00,350
I just was uneasy with the idea
that the Earth would just go
up and down like that,
422
00:29:00,400 --> 00:29:02,250
I call it trampoline tectonics.
423
00:29:02,400 --> 00:29:04,850
I didn't believe in trampoline tectonics
424
00:29:07,300 --> 00:29:11,350
Spencer and his team
examine the Bouse rocks in the lab.
425
00:29:11,400 --> 00:29:15,550
They are especially interested
in the levels of strontium isotopes.
426
00:29:16,400 --> 00:29:18,650
Strontium isotopes found in these rocks
427
00:29:18,700 --> 00:29:22,850
are irregular atoms undetectable
to conventional microscopes.
428
00:29:23,000 --> 00:29:25,750
They come in heavier and lighter forms.
429
00:29:27,000 --> 00:29:31,150
The relative concentration
of heavy and light forms varies.
430
00:29:31,200 --> 00:29:33,650
It depends on the origin of the water.
431
00:29:34,000 --> 00:29:39,850
River water usually has
a different strontium isotope
concentration than ocean water.
432
00:29:41,700 --> 00:29:43,550
Depending on the concentration
433
00:29:43,600 --> 00:29:45,550
scientists can often determine,
434
00:29:45,600 --> 00:29:49,450
if sediment was formed
in freshwater or in the sea.
435
00:29:52,300 --> 00:29:58,550
Spencer's graph of the isotope
concentration of the Bouse formation
confirms his suspicions.
436
00:29:59,500 --> 00:30:03,350
The green dots represent
isotopic concentrations of sea water,
437
00:30:03,400 --> 00:30:07,250
the blue dots represent
ratios typical for river water.
438
00:30:07,300 --> 00:30:10,450
The red dots are his readings
from the Bouse formation.
439
00:30:10,500 --> 00:30:12,550
They indicate freshwater.
440
00:30:13,600 --> 00:30:17,450
When we got our first results
it was immediately clear that
441
00:30:17,500 --> 00:30:22,950
we were seeing no marine signature
in any of the Bouse samples.
442
00:30:23,000 --> 00:30:24,550
We were a little surprised.
443
00:30:24,600 --> 00:30:29,250
We didn't expect that
every number would come out
looking like river water.
444
00:30:30,700 --> 00:30:36,350
These results question
the validity of the second,
more recent uplift theory.
445
00:30:37,400 --> 00:30:40,550
If the Bouse Formation
was never under the sea,
446
00:30:40,600 --> 00:30:43,050
the uplift theory couldn't apply-
447
00:30:43,200 --> 00:30:47,850
and headward erosion
along the lower Colorado
could not have happened.
448
00:30:48,800 --> 00:30:51,050
Scientists had to look for another model
449
00:30:51,100 --> 00:30:53,950
explaining how the river
cut across the plateau.
450
00:30:54,800 --> 00:30:58,450
About 250 miles west
of Grand Canyon village
451
00:30:58,500 --> 00:31:02,350
there is a canyon system
called the Lake Manix Basin.
452
00:31:03,100 --> 00:31:07,250
Norman Meek Professor of Geography
at Cal State San Bernardino
453
00:31:07,300 --> 00:31:11,950
believes this area may offer a clue
of how its bigger cousin got started.
454
00:31:12,800 --> 00:31:17,350
The Lake Manix Basin has sometimes
been called the Grand Canyon
of the Mojave River,
455
00:31:17,400 --> 00:31:21,250
because of the spectacular landscape
that's portrayed here,
456
00:31:21,300 --> 00:31:23,650
a miniature version
of the Grand Canyon.
457
00:31:24,000 --> 00:31:29,850
The site of Lake Manix Basin
is connected to Silver Soda Lake
via a canyon.
458
00:31:30,000 --> 00:31:33,050
Meek wondered if
the formation of this canyon
459
00:31:33,100 --> 00:31:36,250
could throw light on the formation
of the Grand Canyon.
460
00:31:36,400 --> 00:31:39,450
First he examined
the site of Lake Manix.
461
00:31:39,500 --> 00:31:42,050
Lake Manix is an extinct desert lake.
462
00:31:42,100 --> 00:31:46,250
It used to stretch over an area
of more than 90 square miles.
463
00:31:46,300 --> 00:31:49,950
Yet, many thousands of years ago
the lake disappeared.
464
00:31:50,900 --> 00:31:54,650
Meek wanted to find out
when and why the lake drained.
465
00:31:55,000 --> 00:31:56,750
At the edge of lake Manix
466
00:31:56,800 --> 00:32:00,350
he found sediments
of ancient shorelines from the old lake
467
00:32:01,200 --> 00:32:04,650
In the deposits
he found freshwater shells.
468
00:32:05,500 --> 00:32:09,550
He took them to a radiocarbon dating lab
to find out their age.
469
00:32:10,400 --> 00:32:14,450
Radio Carbon is an isotope
that occurs in all living creatures.
470
00:32:15,400 --> 00:32:18,850
Its half life is almost 6000 years,
471
00:32:18,900 --> 00:32:24,450
which means after around 6000 years
half of the original amount is gone.
472
00:32:26,900 --> 00:32:30,350
By measuring how much radio carbon
is left in the shells
473
00:32:30,400 --> 00:32:33,050
scientists can determine their age.
474
00:32:33,200 --> 00:32:35,950
Meek found that the shellfish
in the Manix basin
475
00:32:36,000 --> 00:32:38,650
were alive 19,000 years ago.
476
00:32:38,700 --> 00:32:40,950
But after that they died.
477
00:32:41,000 --> 00:32:43,650
At that point Lake Manix emptied.
478
00:32:44,000 --> 00:32:46,250
When he looked at Silver Soda Lake
479
00:32:46,300 --> 00:32:50,650
he found that it existed
from around the time
when Lake Manix emptied.
480
00:32:50,700 --> 00:32:53,650
Could these two lakes be connected?
481
00:32:55,300 --> 00:33:00,250
Meek suggested the canyon here
was cut by a mechanism called spill over
482
00:33:00,900 --> 00:33:03,750
He theorized that 19,000 years ago
483
00:33:03,800 --> 00:33:07,250
heavy rainfall or snowmelts
filled up the lake
484
00:33:07,300 --> 00:33:10,250
until finally the water
spilled over the rim.
485
00:33:10,800 --> 00:33:13,150
The lake drained dramatically.
486
00:33:13,200 --> 00:33:14,950
Over a few thousand years
487
00:33:15,000 --> 00:33:17,850
it cut down through the rocks
carved a canyon
488
00:33:17,900 --> 00:33:20,350
and then created Silver Soda Lake.
489
00:33:20,500 --> 00:33:22,950
It's just like a reservoir breaking,
490
00:33:23,000 --> 00:33:24,350
there is a lot of energy,
491
00:33:24,400 --> 00:33:30,150
that energy rips away
the sediments and the bedrock
that make up the canyon
492
00:33:30,200 --> 00:33:32,450
and you get a through-flowing river
493
00:33:33,200 --> 00:33:34,850
Scientists speculated
494
00:33:34,900 --> 00:33:38,950
that if spill over explained how
a canyon formed in the Mojave desert,
495
00:33:39,000 --> 00:33:45,350
it could also explain
how the Grand Canyon formed
just 250 miles to the east.
496
00:33:45,400 --> 00:33:49,050
Now they just had to find the lake.
497
00:33:49,300 --> 00:33:51,350
Today there is no lake-
498
00:33:51,400 --> 00:33:54,950
but there are 200 feet
of green layered deposits-
499
00:33:55,000 --> 00:33:58,450
remnants of an ancient lake
called Lake Bidahochi.
500
00:33:58,500 --> 00:34:02,050
And so this green layer
right here reflects the idea
501
00:34:02,100 --> 00:34:07,550
that Lake Bidahochi was in existence
east of the Grand Canyon
between 16 and 6 million years ago.
502
00:34:08,400 --> 00:34:09,950
Over 10 million years
503
00:34:10,000 --> 00:34:17,650
a lake deposited fine-grained sediments
like silt, clay and sand
mixed with grey volcanic ash.
504
00:34:18,400 --> 00:34:21,150
The deposits indicate
the existence of a lake-
505
00:34:21,200 --> 00:34:25,150
but they don't show how the lake
overspilled and carved the Canyon.
506
00:34:26,300 --> 00:34:31,150
Jon Douglass, Geography professor
at Paradise Valley Community College in Arizona,
507
00:34:31,200 --> 00:34:33,850
wanted an effective way to test the theory
508
00:34:33,900 --> 00:34:36,250
He built a small scale model
of the Grand Canyon
509
00:34:36,300 --> 00:34:38,950
to demonstrate
how the lake could have overflowed.
510
00:34:40,300 --> 00:34:43,250
6 million years ago,
the canyon wasn't yet carved-
511
00:34:43,300 --> 00:34:46,550
but Lake Bidahochi
was full to the point of overflow.
512
00:34:47,400 --> 00:34:50,650
And then as the lake came in,
the lake filled.
513
00:34:50,800 --> 00:34:51,850
It filled and filled,
514
00:34:52,000 --> 00:34:55,550
higher and higher and higher
until it eventually spilled
across the lowest point;
515
00:34:56,100 --> 00:34:58,150
across the Kaibab plateau.
516
00:34:58,300 --> 00:35:00,650
And then water poured down
the other side;
517
00:35:00,700 --> 00:35:02,550
those waterfalls
continued to retreat back
518
00:35:02,600 --> 00:35:05,450
and the whole time
you're cutting Great Canyon.
519
00:35:07,000 --> 00:35:11,750
Douglass suggests that Lake Bidahochi
drained and formed a stream.
520
00:35:12,600 --> 00:35:17,150
The steep gradient of the riverbed caused
the stream to cut deep into the rock.
521
00:35:18,500 --> 00:35:21,650
Over time the size
of the stream increased
522
00:35:21,700 --> 00:35:24,350
and more and more water
poured out of the lake
523
00:35:24,400 --> 00:35:27,950
which in turn cut deeper and deeper
into the rock.
524
00:35:29,900 --> 00:35:32,450
But not all geologists agree.
525
00:35:33,000 --> 00:35:38,350
They say there is no evidence of
there ever being a lake large enough
to carve the Grand Canyon.
526
00:35:38,600 --> 00:35:42,050
So at present there is still
no definitive answer
527
00:35:42,100 --> 00:35:44,650
as to how the river came into existence
528
00:35:46,700 --> 00:35:48,150
What we do know
529
00:35:48,200 --> 00:35:52,250
is that when it began flowing
around 4.5 million years ago,
530
00:35:52,300 --> 00:35:55,650
it cut a one mile deep scar
in the surface.
531
00:35:56,500 --> 00:36:00,250
To cut that whole canyon
in 5 million years is a considerable feat
532
00:36:01,500 --> 00:36:04,950
How did the Colorado river
manage to cut the canyon.
533
00:36:05,700 --> 00:36:08,250
There are bigger rivers
in the United States,
534
00:36:08,300 --> 00:36:10,150
which haven't cut deep.
535
00:36:11,000 --> 00:36:14,150
The biggest and longest river
in North America
536
00:36:14,200 --> 00:36:17,450
is not the Colorado river
but the Mississippi.
537
00:36:18,500 --> 00:36:22,950
It flows nearly 2500 miles
from its source in Minnesota
538
00:36:23,000 --> 00:36:25,350
to its mouth at the Gulf of Mexico.
539
00:36:25,700 --> 00:36:29,450
It carries 10 times more water
than the Colorado.
540
00:36:30,100 --> 00:36:33,850
Yet, the Mississippi
did not carve a Grand Canyon.
541
00:36:35,600 --> 00:36:39,650
Evidently, volume of water
is not the only factor.
542
00:36:41,100 --> 00:36:45,650
Something else gave the Colorado River
its enormous cutting power.
543
00:36:48,200 --> 00:36:51,350
The Colorado River begins
in the Rocky Mountains-
544
00:36:51,400 --> 00:36:53,450
9000 feet above sea level.
545
00:36:53,900 --> 00:36:58,950
On its course it drops ten feet
for every mile it flows.
546
00:36:59,300 --> 00:37:03,350
The Mississippi on the other hand
begins its journey in Minnesota-
547
00:37:03,400 --> 00:37:06,550
almost 1500 feet above sea level
548
00:37:06,600 --> 00:37:08,850
dropping less than a foot per mile.
549
00:37:11,900 --> 00:37:14,850
Although the Mississippi
has 10 times more water
550
00:37:15,000 --> 00:37:17,350
it is a less erosive river,
551
00:37:17,400 --> 00:37:19,950
because it has a lower gradient.
552
00:37:20,800 --> 00:37:23,150
All rivers want to run downhill
553
00:37:23,200 --> 00:37:25,350
It is the golden rule of gravity.
554
00:37:25,600 --> 00:37:28,750
Two rivers can have
the same amount of water,
555
00:37:28,800 --> 00:37:31,850
but for every one degree
of extra gradient,
556
00:37:31,900 --> 00:37:35,750
the steeper river
gets a one percent increase in power.
557
00:37:37,700 --> 00:37:42,750
My observations have been that
this river and even some of
its little tributary streams
558
00:37:42,800 --> 00:37:48,150
have enough power that they cut though
any kind of rock like butter.
559
00:37:49,000 --> 00:37:53,750
The speed and depth of cutting also
depends on the rock it is carving into.
560
00:37:55,200 --> 00:37:58,050
Hard rock like granite is much tougher
561
00:37:58,100 --> 00:38:00,550
so the river cuts a narrow gorge.
562
00:38:01,700 --> 00:38:06,050
Soft rock like shale
is easy for water to cut through-
563
00:38:06,100 --> 00:38:08,550
so the river carves a broad canyon.
564
00:38:09,800 --> 00:38:13,450
With soft rock, as the sides erode away
565
00:38:13,500 --> 00:38:15,450
the canyon widens.
566
00:38:16,600 --> 00:38:21,150
Joel Pederson geomorphologist
at Utah State University
567
00:38:21,300 --> 00:38:26,450
is on a quest to discover
how the river cut away the canyon walls
568
00:38:27,500 --> 00:38:29,850
The information that we collect
from this what we are doing,
569
00:38:29,900 --> 00:38:31,650
we're relating it
to the history of the river
570
00:38:31,700 --> 00:38:34,650
and so what the river
is doing in the past,
571
00:38:34,700 --> 00:38:39,450
as it's eroding
it is also stopping sometimes
and depositing sediment.
572
00:38:40,100 --> 00:38:44,350
Pederson is interested in finding out
how fast the canyon erodes.
573
00:38:44,400 --> 00:38:47,850
He uses a technique
called luminescence dating.
574
00:38:49,200 --> 00:38:52,550
This uses light
to measure the age of a rock.
575
00:38:52,600 --> 00:38:57,250
It works on sediments containing
minerals such as quartz or feldspar
576
00:38:57,300 --> 00:38:59,250
that have been buried in the dark.
577
00:38:59,300 --> 00:39:03,950
As sediment builds up
it is gradually sealed away from the sun
578
00:39:04,300 --> 00:39:09,950
Pederson measures the amount of
luminescence a sample gives off
when exposed to light.
579
00:39:10,700 --> 00:39:13,050
This method can date sediments
580
00:39:13,100 --> 00:39:17,150
between a few hundred
to several hundred thousand years old.
581
00:39:17,200 --> 00:39:20,050
We're collecting sediment
that hasn't yet seen light,
582
00:39:20,100 --> 00:39:22,350
and the metal tube
prevents it from seeing light.
583
00:39:22,400 --> 00:39:25,450
And we pull the tube out
and take it back to the laboratory.
584
00:39:27,600 --> 00:39:28,950
In the laboratory
585
00:39:29,000 --> 00:39:32,250
scientists expose the samples
of ancient river sediments
586
00:39:32,300 --> 00:39:34,650
to specific wavelengths of light.
587
00:39:35,500 --> 00:39:38,750
This energy excites
the electrons in the sediment-
588
00:39:38,800 --> 00:39:43,050
some respond by releasing
their own energy, in the form of light-
589
00:39:43,100 --> 00:39:45,550
and this minute signal is measured.
590
00:39:45,900 --> 00:39:50,250
The greater the response from the
particles the longer they spent buried
591
00:39:52,300 --> 00:39:56,050
So it's telling us that moment in time,
how many years ago it was,
592
00:39:56,100 --> 00:39:58,550
that the river actually
deposited that sediment
593
00:39:58,600 --> 00:40:02,350
and then buried it under more sediment
so it couldn't see light any more.
594
00:40:06,600 --> 00:40:10,850
When Pederson measured the incision rates
along the whole length of the river
595
00:40:10,900 --> 00:40:13,250
he found something unexpected.
596
00:40:14,700 --> 00:40:20,350
179 miles downstream
the canyon appeared less deep.
597
00:40:20,800 --> 00:40:24,250
Something changed and
lessened the river's cutting power.
598
00:40:24,300 --> 00:40:29,650
Could it be that the river
lost its power due to changes
beneath the land itself?
599
00:40:29,900 --> 00:40:34,550
It was an intriguing puzzle
scientists were desperate to solve.
600
00:40:36,700 --> 00:40:38,850
3 and a half million years ago
601
00:40:38,900 --> 00:40:44,150
the Colorado plateau ruptured and
created a deep chasm across the canyon
602
00:40:44,200 --> 00:40:46,750
It's called the Toroweap fault.
603
00:40:47,600 --> 00:40:53,350
Tectonic activity along the fault
slowly lowered the land
of the plateau to the west.
604
00:40:53,600 --> 00:40:55,450
And as the land fell away,
605
00:40:55,500 --> 00:40:58,950
it weakened the cutting power
of the river flowing over it.
606
00:40:59,800 --> 00:41:03,050
Karl Karlstrom explains
with a loaf of bread.
607
00:41:03,100 --> 00:41:07,150
We'll imagine this loaf of bread
as a stack of rocks
608
00:41:07,200 --> 00:41:11,450
that is going to be incised
by the river to be the Grand Canyon.
609
00:41:11,500 --> 00:41:16,350
And we'll imagine this knife
as the Colorado River itself,
610
00:41:16,400 --> 00:41:21,850
which over time can erode through even
the hardest rocks to form a canyon.
611
00:41:21,900 --> 00:41:25,750
But many times there's a break
in the crust called fault.
612
00:41:25,800 --> 00:41:29,550
And so if I incise the river
at the same time
613
00:41:29,600 --> 00:41:32,550
that I am moving one block down,
614
00:41:32,600 --> 00:41:35,950
and I think you can see this
if I turn it up like this,
615
00:41:36,000 --> 00:41:38,950
and you can see that
on one side the canyon is quite deep
616
00:41:39,000 --> 00:41:40,950
and on the other much less deep.
617
00:41:42,800 --> 00:41:44,950
Scientists had their answer.
618
00:41:45,000 --> 00:41:46,850
The river stayed the same
619
00:41:46,900 --> 00:41:50,750
but the land
west of the Toroweap Fault sank lower
620
00:41:50,800 --> 00:41:54,250
and so escaped
the full cutting force of the water.
621
00:41:55,500 --> 00:41:59,050
The Colorado river
has cut a masterpiece of a canyon.
622
00:41:59,100 --> 00:42:01,650
But water doesn't only destroy rock-
623
00:42:01,700 --> 00:42:05,150
amazingly it can also create it.
624
00:42:05,900 --> 00:42:12,150
Scientists are intrigued
by new rocks within the canyon
that are still growing.
625
00:42:15,900 --> 00:42:19,350
The Colorado river
has been a great destroyer.
626
00:42:20,200 --> 00:42:22,750
In the last 4.5 million years
627
00:42:22,800 --> 00:42:26,850
it has excavated
over 800 cubic miles of rock.
628
00:42:28,000 --> 00:42:30,650
It created a gorge so big
629
00:42:30,900 --> 00:42:33,350
that all of the river water in the world
630
00:42:33,400 --> 00:42:36,450
would fill the canyon
to just over a third.
631
00:42:37,100 --> 00:42:39,650
But the river can also create rocks.
632
00:42:39,700 --> 00:42:41,550
At certain points in the canyon
633
00:42:41,600 --> 00:42:45,650
scientists have discovered
new rocks forming today.
634
00:42:48,600 --> 00:42:52,450
Laura Crossey, Professor
at the University of New Mexico
635
00:42:52,500 --> 00:42:56,550
is an expert on these rocks...
the youngest in the canyon.
636
00:42:56,600 --> 00:43:00,050
The big story of Grand Canyon
is the carving of this beautiful place,
637
00:43:00,100 --> 00:43:05,150
there are other processes such as
travertine that cause changes to occur
638
00:43:05,200 --> 00:43:08,150
and the younger rocks
to form inside that very canyon.
639
00:43:09,700 --> 00:43:11,850
These travertines are special
640
00:43:11,900 --> 00:43:16,150
because they are created from water
saturated in carbon dioxide
641
00:43:16,400 --> 00:43:20,250
and they are actually formed
at the bottom of the canyon itself.
642
00:43:21,100 --> 00:43:24,850
The carbon dioxide
comes from deep inside the earth.
643
00:43:25,500 --> 00:43:27,650
It leaks out to the surface.
644
00:43:29,900 --> 00:43:32,350
Here, it dissolves in water,
645
00:43:32,400 --> 00:43:37,450
acidifying it and giving it the power
to dissolve limestone.
646
00:43:40,100 --> 00:43:42,650
The carbon dioxide
escapes from the water,
647
00:43:42,700 --> 00:43:45,250
forming bubbles like fizzy soda.
648
00:43:46,000 --> 00:43:50,150
As the gas escapes,
it leaves behind calcium carbonate,
649
00:43:50,300 --> 00:43:52,650
which coats objects in its path.
650
00:43:54,500 --> 00:43:58,150
In some places
it forms stone waterfalls.
651
00:43:58,200 --> 00:44:02,250
In others it covers sticks and twigs.
652
00:44:02,300 --> 00:44:06,050
So these are just small examples
of the coatings of travertine
653
00:44:06,100 --> 00:44:10,050
that form on every stick and twig and
cobble that comes down the stream-bed
654
00:44:10,200 --> 00:44:12,550
It accumulates into
vast piles of sediment
655
00:44:12,600 --> 00:44:16,550
which are instantly formed into rock,
the youngest rocks in the Grand Canyon.
656
00:44:18,900 --> 00:44:23,450
Every drop in the river has in some ways
shaped the landscape here.
657
00:44:24,300 --> 00:44:28,250
But water does far more than
destroying rocks and building them.
658
00:44:28,300 --> 00:44:29,850
Without the river-
659
00:44:29,900 --> 00:44:33,850
the current plant and animal life
would struggle to survive.
660
00:44:34,000 --> 00:44:38,350
And it was the river
which attracted early settlers here.
661
00:44:38,400 --> 00:44:44,250
When the ancestors of the Hualapai
arrived in the Grand Canyon
about seven hundred years ago
662
00:44:44,300 --> 00:44:48,850
they celebrated the Colorado River
as an important source for life.
663
00:44:48,900 --> 00:44:51,150
And it remains that today.
664
00:44:51,300 --> 00:44:54,850
The river's all source of life out here.
665
00:44:54,900 --> 00:45:00,950
The canyon to me personally
is something that our ancestors,
they fought hard to retain.
666
00:45:01,000 --> 00:45:03,450
Because they knew the importance of it.
667
00:45:04,100 --> 00:45:10,250
Our wish is to maintain it
in its natural state or its beauty.
668
00:45:11,400 --> 00:45:14,150
Modern visitors of the canyon
are mesmerized
669
00:45:14,200 --> 00:45:17,950
as the first Native Americans would
have been several hundred years ago.
670
00:45:19,400 --> 00:45:22,750
It's one of the natural wonders
of the world.
671
00:45:24,400 --> 00:45:29,350
A monument to the age-old,
colossal forces that created it.
672
00:45:36,200 --> 00:45:39,750
1.7 billion years ago it began.
673
00:45:41,900 --> 00:45:45,050
Layers of flat-lying,
stratified sediments
674
00:45:45,100 --> 00:45:47,350
build up high canyon walls.
675
00:45:47,800 --> 00:45:53,150
Uplift elevates the plateau
and rivers cut deep into the rocks.
676
00:45:53,700 --> 00:45:56,350
And the climate today is arid.
677
00:45:56,400 --> 00:45:58,050
Nothing is lost.
678
00:45:58,100 --> 00:46:00,150
Everything is visible.
679
00:46:00,600 --> 00:46:04,150
It is difficult to find a canyon
as impressive as this one:
680
00:46:04,800 --> 00:46:07,350
Possibly in South-eastern Tibet,
681
00:46:07,400 --> 00:46:10,950
home of the biggest, longest
and deepest canyon.
682
00:46:11,700 --> 00:46:14,450
The Yarlung Tsangpo Great Canyon.
683
00:46:15,100 --> 00:46:19,550
The climate is different and the area
is covered with dense vegetation.
684
00:46:20,400 --> 00:46:24,550
The Euphrates is a very large river
running through arid Iraq,
685
00:46:24,600 --> 00:46:27,150
a climate not dissimilar to Arizona.
686
00:46:27,400 --> 00:46:31,150
But this area never uplifted
and formed a canyon.
687
00:46:32,900 --> 00:46:37,950
The Grand Canyon might not be
the biggest and longest canyon on earth
688
00:46:39,500 --> 00:46:43,350
But the powerful forces
that created it and made it unique
689
00:46:43,400 --> 00:46:45,350
are still hard at work.
690
00:46:46,600 --> 00:46:49,850
Nobody can predict
how much uplift there will be.
691
00:46:49,900 --> 00:46:52,050
But if the river stays on course
692
00:46:52,100 --> 00:46:55,250
then the future
of the Grand Canyon looks good.
693
00:46:56,100 --> 00:47:00,550
And if you think this is grand-
you ain't seen nothing, yet.
694
00:47:00,600 --> 00:47:03,150
Stick around for another
million years or two
695
00:47:03,200 --> 00:47:08,550
and the canyon
might be even deeper with walls
just as sheer as they are today.
696
00:47:08,600 --> 00:47:12,850
The Grand Canyon
is just getting grander.
697
00:47:14,100 --> 00:47:19,100
www.mvgroup.org
698
00:47:22,100 --> 00:47:26,100
Preuzeto sa www.titlovi.com
63501
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