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Earth, a 4.5- Billion-year-old planet,
still evolving.

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As continents shift and clash, volcanoes
erupt, glaciers grow and recede,

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the Earth's crust is carved
in numerous and fascinating ways,

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leaving a trail of
geological mysteries behind.

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In this episode, Loch Ness, in
the Highlands of Scotland, is explored.

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It holds more water
than any other lake in Britain,

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with a bedrock containing some
of the oldest rocks on the planet.

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Set in a landscape that was
once part of America,

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Loch Ness is a lake with an
enduring myth, the Loch Ness monster.

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A team of scientists investigate
how Loch Ness was made.

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The clues they uncover
also provide a window

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into the formation of the Earth itself.

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Deep, dark and full of mystery.

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This is Loch Ness
in the Highlands of Scotland.

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For a thousand years, there
have been claims that this vast lake

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hides a strange and terrible secret,
the fabled Loch Ness monster.

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A mythical beast, suggested by some
as a descendant of the dinosaurs

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which once roamed
this part of Scotland.

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Loch Ness would be the perfect
hiding place for a prehistoric monster.

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At 23 miles long, and a mile wide,
this vast freshwater lake

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covers the same area as
New York's Manhattan Island.

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And it's more than 700 feet deep.

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But the monster is not the only mystery
that surrounds Loch Ness.

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In the hills above the loch,
there is a type of rock

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whose origin baffled scientists for years.

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It's a sandstone,

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and it's the start of the investigation
into how Loch Ness was made.

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It's known
as the old red sandstone,

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and it's given that name
because it's red and it's a sandstone,

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and it's called old

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because
it's about 350 million years old.

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The old red sandstone runs down
one side of Loch Ness.

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But the most astonishing fact
about these rocks is not their age,

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but where they come from.

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These rocks actually belong
to my homeland of North America,

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because these rocks originated
on the North American continent,

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and then have separated
from North America.

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But in many ways this is almost a little
bit of home for me here in Scotland.

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But how do geologists know
that this old red sandstone

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comes from 3,000 miles away,
on the other side of the Atlantic Ocean?

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These rocks are identical
in age and character

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to the rocks that actually form
the Catskill Mountains,

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and so this part of Scotland belonged
to northeastern North America.

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For more than a thousand years,
old red sandstone has been used

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for building castles
in this part of Scotland.

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But it's also been quarried in the US

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and used for brownstone buildings
in New York City.

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Under the microscope,

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rocks from both continents
have an identical crystal structure,

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and chemical analysis has also proved
that they're exactly the same age.

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But how did part of America end up
on the shores of Loch Ness?

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To answer this crucial question,

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the investigation must go
much further back in time,

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to look for evidence in the ancient
bedrock of northern Scotland.

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It's here that the story
of Loch Ness begins.

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The trail starts north of Loch Ness,
where the bedrock comes to the surface.

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This landscape is full
of the extraordinary mysteries

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of an unimaginably ancient past.

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It's made of a type of rock
called Lewisian gneiss.

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Recent drilling and blasting for
a new road cut have exposed evidence

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which uncovers an amazing chapter
in Earth's history.

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The long straight lines are the drill holes
left in the rock face.

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Modern radioisotope dating
has given geologists the first clue

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to understanding the origin
and formation of these rocks.

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These rocks are very special
to geologists.

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They are some of the very
oldest rocks in the world.

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We see them in very few places,

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perhaps a dozen places across
the globe contain rocks of this age,

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talking about two and a half
to three billion years old.

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The origin of the grey Lewisian gneiss
lies in the first crust

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that cooled on the surface of the Earth.

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After its formation 4.5 billion years ago,
parts of this crust were mixed together

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with the earliest sediments,
buried, re-melted and forced back up,

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again and again,
for more than a billion years.

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These extraordinary rocks
are the result

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of that devastating period
in our planet's history.

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And there's more evidence
exposed in this road cut,

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revealing crucial information about the
early history of the Loch Ness region.

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This exposure contains

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three important pieces
of geological jigsaw puzzle.

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First, we have the grey gneiss,
2.5 to 3 billion years old.

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Secondly, we have
this black igneous material

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which has been intruded into the area.

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This is two billion years old.

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And thirdly, we have
this pink granitic intrusion

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that both intrudes the black material
and the gneiss,

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and this is 1.8 billion years old.

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This evidence reveals that after
the formation of the Lewisian gneiss,

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much younger rocks were then melted
and mixed into the ancient crust.

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But this process took
an incredible length of time.

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What we've got here

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are rocks that record over a billion years
of Earth history.

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Now, to put that into perspective,

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that is almost a quarter of the age
of the Earth recorded in this exposure.

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This is the bedrock of Loch Ness.

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It carries an extraordinary story
of a major part of Earth's history.

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And there are yet more secrets
hidden in these rocks.

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It looks very much because
of the temperatures and pressures

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that these rocks were under that they've
been to depths of perhaps 50 miles

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beneath the Earth's surface in the past.

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This suggests that these rocks
have been to hell and back

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two or three occasions
over a billion year period.

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Geologists now know that
the only force powerful enough

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to produce this extraordinary mix
of rocks is plate tectonics.

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Plate tectonics is the process by which
the giant plates of the Earth's crust

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are driven slowly across the planet's
surface by vast convection currents

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deep in the Earth's hot mantle.

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In the Loch Ness region,
the evidence in the road cut

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reveals that incredible pressures forced
the crust deep down into the earth,

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where it was melted, deformed,
mixed together,

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then finally brought back to the surface.

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After that, for another billion years, this
ancient land mass quietly eroded down

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to a rough, rolling landscape.

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But this wasn't the green terrain
we see now.

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There was much less oxygen
in the Earth's atmosphere than today,

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and the surface would have looked like
a lunar landscape - desolate and sterile.

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Incredibly, remnants of that billion year
old landscape are still preserved today.

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The clues are revealed
in another road cut,

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where the trained eye
can draw amazing conclusions

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from what looks like a jumble of rocks.

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At this road cut,
we can see Lewisian gneiss

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which is between two and a half
and three billion years old.

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But up here we have something
completely different.

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If I go up to this level
and look above it,

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we have horizontally bedded
red sandstones.

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This sudden change in rock type
helps to unravel the mystery

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hidden in these ancient formations.

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They're believed to have been laid down
in a continental environment by rivers.

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We've got river systems that laid down
horizontally bedded sedimentary rocks

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on an ancient landscape.

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So this simple outcrop reveals
that even in a world with little oxygen,

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the ancient bedrock of Scotland
was covered in rivers a billion years ago.

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And there's yet another
secret hidden here.

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There is a junction between these rocks
which are almost a billion years old

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and the rocks below that are two
and a half to three billion years old.

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This is a major time gap of between
one and a half and two billion years.

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The time gap revealed here
is extraordinary.

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It shows that after the traumas
of their early formation,

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the rocks of the Loch Ness region
went through a period of calm

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which lasted more than a third
of the age of the Earth.

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The investigation into how
Loch Ness was made

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has uncovered its first evidence.

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Identical old red sandstone
found on two continents

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proves that Scotland and America
were once joined together.

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Some of the oldest rocks in the world

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reveal that the bedrock
underlying Loch Ness

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was made during the primeval creation
of the Earth's crust.

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Bedded sandstones
lying on the ancient bedrock

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show that rivers flowed over
this landscape a billion years ago,

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during a long period of tranquillity.

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But the calm couldn't last forever.

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A major continental collision
was looming,

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and with it the union
between Scotland and England.

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The investigation
into how Loch Ness was made

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will next uncover
the geological structures

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which would eventually create
Loch Ness.

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The search for evidence begins
with a 19th-century scientific mystery.

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In the 1880s, geologists in Scotland
were baffled by a sequence of rocks

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they found north of Loch Ness.

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Here in a remote hillside
lay the problem.

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A huge mass of very old Lewisian gneiss
was lying on top of much younger rocks.

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But the 19th-century geologists
had never encountered this before.

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In their experience, younger rocks
always lay on top of older beds.

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Then, one scientist invented a novel
approach to try to solve the puzzle.

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A survey geologist back in
the Victorian age, 125 years ago,

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mapped this area
and his name was Henry Cadell.

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He went back to Edinburgh and he
worried about what he'd seen in the field

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and thought, "How do I replicate what
I've seen? How does this happen?"

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So he built a model and he attempted
then to show, using the model,

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what it was that he saw in the field.

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Cadell's model was simple.

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He suspected that some force
had squeezed the rocks horizontally

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to make this upside-down sequence,

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so he built an apparatus containing
layers of sand and clay to test his ideas.

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Professor Underhill is using
a replica of Cadell's equipment,

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filled with alternating layers
of black sand and plaster of Paris,

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to try and duplicate Cadell's experiment.

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Turning the screw
winds the block forward,

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imitating the horizontal pushing force
that Cadell thought was the culprit.

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00:12:52,135 --> 00:12:56,804
As the horizontal force increases,
the layers are pushed over each other

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along a shallow plane which geologists
now call a thrust fault.

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And we've got
the first thrust appearing.

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Oh, look at that, another thrust going in.

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The experiment showed Cadell
exactly how older layers,

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the ones on the bottom,

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are pushed over and on
top of the younger layers

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along the plane of the thrust fault.

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There's some beautiful
structures in here,

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there's a thrust fault running through
here which duplicates the white layer,

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and another one through here
and the final thrust fault

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which is at the lowest angle,
out here towards the left-hand side.

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A success in terms
of a simple model

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replicating what we see on the ground,
and I can see how Cadell and others,

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when attempting such things,

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began to understand what it was
that they saw in the field.

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They could replicate it
in a simple, crude model,

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but replicate it
in a very successful manner.

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Once Cadell and his colleagues
understood the principle of thrust faults,

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the apparently illogical sequence of the
rocks they saw in northwest Scotland

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began to make sense.

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Well, the slope
represents a thrust fault.

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00:14:18,104 --> 00:14:22,981
What we have underneath it is
a bedded younger quartzite succession

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which is pink.

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00:14:24,441 --> 00:14:28,234
Above it, the grey rock,
the rubbly grey hillside we see above

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is the Lewisian gneiss again.

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00:14:30,903 --> 00:14:33,738
And the surface in between,
which is putting older rock,

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00:14:33,738 --> 00:14:37,615
the grey material, onto the pink rock,
the younger material,

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is the thrust fault, just like in the model
that we saw before.

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Geologists now know that a thrust fault
is the smoking gun

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00:14:45,579 --> 00:14:48,455
that shows where
continents have collided.

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00:14:49,956 --> 00:14:54,125
But which continents were colliding
to make the thrust faults in Scotland?

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00:14:54,125 --> 00:14:57,169
And how were they involved
in making Loch Ness?

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The scientists' trail now led them
to another thrust fault,

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00:15:03,172 --> 00:15:04,799
the Moine Thrust.

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00:15:04,799 --> 00:15:09,551
The Moine Thrust is one of
the biggest thrust faults on Earth.

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00:15:09,551 --> 00:15:12,261
Running for 120 miles down
the northwest of Scotland,

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00:15:12,261 --> 00:15:15,305
it's mostly hidden from view,

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but Professor Underhill
has found one of the rare locations

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where the thrust can be seen
on the surface.

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This apparently insignificant join
between two rock layers

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is the actual line of the thrust,
and it reveals a geological bombshell.

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The dark layer above the thrust
comes from England,

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but the surprise lies
in the yellow limestone below it.

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00:15:42,446 --> 00:15:44,655
Just like the old red sandstone
at Loch Ness,

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00:15:44,655 --> 00:15:48,408
this rock comes from North America.

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00:15:48,408 --> 00:15:51,451
This one small piece of evidence
has enormous implications

227
00:15:51,451 --> 00:15:54,495
for the formation of Loch Ness.

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The amazing thing about this contact

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is that it's the meeting point
between two continents.

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So here we are on a wet Scottish hillside
on a Sunday afternoon

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00:16:02,875 --> 00:16:05,877
and I am touching
the contact between, effectively,

232
00:16:05,877 --> 00:16:10,088
America and northwestern Scotland
on one hand, and England on the other

233
00:16:10,088 --> 00:16:13,214
as was 425 million years ago.

234
00:16:18,635 --> 00:16:22,470
But how did these two
ancient continents collide?

235
00:16:22,470 --> 00:16:27,806
450 million years ago, a supercontinent
containing North America and Scotland

236
00:16:27,806 --> 00:16:30,225
lay deep in the southern hemisphere.

237
00:16:31,225 --> 00:16:34,644
At its margin was an ocean wider
than the present-day Atlantic.

238
00:16:34,644 --> 00:16:37,938
On the other side was
England and Europe.

239
00:16:37,938 --> 00:16:40,522
But the forces
of plate tectonics

240
00:16:40,522 --> 00:16:42,024
were slowly pushing

241
00:16:42,024 --> 00:16:44,817
the two land
masses together.

242
00:16:44,817 --> 00:16:48,403
Well, around 450 million
years ago there was a major ocean

243
00:16:48,403 --> 00:16:49,778
where we're standing now.

244
00:16:49,778 --> 00:16:51,988
It was called the lapetus Ocean

245
00:16:51,988 --> 00:16:55,740
and it separated America
and northwestern Scotland on one hand,

246
00:16:55,740 --> 00:16:59,534
from, effectively, southeastern Scotland
and England on the other hand.

247
00:16:59,534 --> 00:17:02,495
Now, what happened
in the 20 million years after that,

248
00:17:02,495 --> 00:17:06,288
that ocean closed,
and eventually was closed sufficiently

249
00:17:06,288 --> 00:17:09,499
that two continents collided
into each other.

250
00:17:12,583 --> 00:17:16,252
The collision between America and
Europe pushed massive layers of rock

251
00:17:16,252 --> 00:17:20,588
over each other,
forcing upwards a range of mountains

252
00:17:20,588 --> 00:17:23,924
higher than the Himalayas are today.

253
00:17:23,924 --> 00:17:28,719
Still firmly attached to America, Scotland
and England became fused together.

254
00:17:30,761 --> 00:17:34,054
But what did this collision have to do
with the making of Loch Ness?

255
00:17:34,054 --> 00:17:38,974
The loch itself provides
the most fundamental evidence.

256
00:17:38,974 --> 00:17:42,018
The one thing that's quite
striking about Loch Ness

257
00:17:42,018 --> 00:17:44,728
is that when you look at it,
particularly from this perspective,

258
00:17:44,728 --> 00:17:47,979
you can see that it runs straight,
almost straight as an arrow,

259
00:17:47,979 --> 00:17:52,232
and that straightness
goes on for about 20 miles.

260
00:17:52,232 --> 00:17:56,110
And as a geologist, that tells me
that there has to be a control

261
00:17:56,110 --> 00:17:58,278
on this topographic straightness,

262
00:17:58,278 --> 00:18:00,738
because nature doesn't produce things
in straight lines.

263
00:18:00,738 --> 00:18:02,780
And so there is a structure here

264
00:18:02,780 --> 00:18:05,699
that is controlling the overall shape
of Loch Ness itself.

265
00:18:05,699 --> 00:18:11,119
This structure is the Great Glen Fault,
a major geological fault line

266
00:18:11,119 --> 00:18:15,413
formed during the continental collision
425 million years ago.

267
00:18:16,831 --> 00:18:20,875
It runs for more than 300 miles
right across Scotland,

268
00:18:20,875 --> 00:18:23,042
slicing the country in two.

269
00:18:23,042 --> 00:18:28,088
Loch Ness exactly follows
the line of the Great Glen Fault.

270
00:18:28,088 --> 00:18:32,006
The Great Glen Fault is not
a thrust fault like the Moine Thrust

271
00:18:32,006 --> 00:18:33,841
where material has been
pushed up over,

272
00:18:33,841 --> 00:18:39,178
it's not a normal fault where material
drops down vertically, it's lateral motion.

273
00:18:42,220 --> 00:18:46,140
The Great Glen Fault is Scotland's
version of the San Andreas Fault,

274
00:18:46,140 --> 00:18:48,599
it's just 400 million years older.

275
00:18:48,599 --> 00:18:51,352
The Great Glen Fault is no longer active,

276
00:18:51,352 --> 00:18:54,478
but this giant split
in the Earth's crust has been a feature

277
00:18:54,478 --> 00:18:58,647
of the Scottish landscape
for more than 400 million years.

278
00:18:58,647 --> 00:19:03,442
It's the foundation of Loch Ness,
and without it the loch could not exist.

279
00:19:03,442 --> 00:19:08,444
Nor could the legend of
the Loch Ness monster.

280
00:19:08,444 --> 00:19:10,988
The investigation into how
Loch Ness was made

281
00:19:10,988 --> 00:19:13,156
has uncovered more evidence.

282
00:19:13,156 --> 00:19:16,867
The discovery of thrust faults
showed geologists what happens

283
00:19:16,867 --> 00:19:19,243
when continents collide.

284
00:19:19,243 --> 00:19:22,871
Yellow limestone from North America
found at the Moine Thrust

285
00:19:22,871 --> 00:19:24,622
proves that America and Scotland

286
00:19:24,622 --> 00:19:29,541
crashed into England
450 million years ago.

287
00:19:29,541 --> 00:19:32,710
And the shape of Loch Ness
reveals the straight line

288
00:19:32,710 --> 00:19:37,212
of the underlying Great Glen Fault,
formed during that continental collision.

289
00:19:38,547 --> 00:19:41,298
After the collision,
the forces of plate tectonics

290
00:19:41,298 --> 00:19:45,967
drove Scotland south
round the surface of the Earth.

291
00:19:45,967 --> 00:19:50,428
Now the investigation must
follow its amazing journey.

292
00:19:53,972 --> 00:19:57,850
The next step in the investigation
into how Loch Ness was made

293
00:19:57,850 --> 00:20:00,935
traces Scotland's journey
round the surface of the Earth,

294
00:20:00,935 --> 00:20:03,728
driven by the forces of plate tectonics.

295
00:20:03,728 --> 00:20:08,648
Understanding what the environment
was like in the past gives clues

296
00:20:08,648 --> 00:20:12,025
to the location of Loch Ness
millions of years ago.

297
00:20:13,317 --> 00:20:18,529
So the investigation now moves on
to the Jurassic period,

298
00:20:18,529 --> 00:20:21,822
165 million years ago.

299
00:20:23,573 --> 00:20:29,493
The trail leads to the Isle of Skye, an
island off the west coast of Scotland.

300
00:20:29,493 --> 00:20:33,537
At Staffin Bay there is
an incredible piece of evidence

301
00:20:33,537 --> 00:20:36,581
which sheds light on this period
in Scotland's past.

302
00:20:36,581 --> 00:20:42,209
Astonishingly, it lay in plain sight
but undiscovered until 1994,

303
00:20:42,209 --> 00:20:46,253
when an amateur geologist
made an extraordinary find.

304
00:20:46,253 --> 00:20:50,381
On the flat, rocky shoreline
of this popular beach,

305
00:20:50,381 --> 00:20:55,050
he discovered a fossilised footprint
of a giant dinosaur.

306
00:20:59,012 --> 00:21:04,973
Dr Anjana Khatwa has come to analyse
the details of this remarkable evidence.

307
00:21:04,973 --> 00:21:07,975
When you walk across these ledges,
it's just an incredible feeling

308
00:21:07,975 --> 00:21:12,686
to think that dinosaurs walked on the
same ledge that I'm walking on now,

309
00:21:12,686 --> 00:21:15,521
165 million years ago.

310
00:21:15,521 --> 00:21:19,274
This ledge, we've got this
wonderful megalosaurus footprint.

311
00:21:19,274 --> 00:21:23,609
The megalosaur was
a 25-foot high carnivorous dinosaur,

312
00:21:23,609 --> 00:21:26,569
quite a formidable predator
during Jurassic times.

313
00:21:27,946 --> 00:21:29,071
(ROARS)

314
00:21:29,071 --> 00:21:33,157
With some individuals standing
as tall as a football goalpost,

315
00:21:33,157 --> 00:21:36,534
megalosaurus was a fearsome monster.

316
00:21:37,534 --> 00:21:40,453
But how could something
as temporary as a footprint

317
00:21:40,453 --> 00:21:43,830
be preserved for 165 million years?

318
00:21:45,040 --> 00:21:46,540
The footprints
are so unique.

319
00:21:46,540 --> 00:21:52,502
What's happened is that a dinosaur has
travelled over a kind of sticky gooey mud

320
00:21:52,502 --> 00:21:54,879
and their impressions
have been left behind.

321
00:21:54,879 --> 00:21:59,048
That mud has dried off and
it's hardened and then, over time,

322
00:21:59,048 --> 00:22:02,674
wind-blown sand has come in
and covered that footprint over

323
00:22:02,674 --> 00:22:04,676
and then as further time has developed,

324
00:22:04,676 --> 00:22:07,928
we get layers of clay and sand
building up over that footprint

325
00:22:07,928 --> 00:22:10,722
and that footprint becomes fossilised
over time.

326
00:22:10,722 --> 00:22:13,223
Now, over a few million years,

327
00:22:13,223 --> 00:22:18,768
erosion occurs and those footprints
become exposed for us to see today.

328
00:22:18,768 --> 00:22:22,187
Dr Khatwa is making a plaster cast
of one of the footprints

329
00:22:22,187 --> 00:22:25,105
so she will be able to examine it
more closely.

330
00:22:26,814 --> 00:22:30,566
We take the cast in order
to have a record of the footprints

331
00:22:30,566 --> 00:22:33,777
so we can take them back to the lab
and have a look at them and understand

332
00:22:33,777 --> 00:22:36,737
how this creature used to live.

333
00:22:36,737 --> 00:22:38,821
As she carefully removes
the plaster cast,

334
00:22:38,821 --> 00:22:44,158
its shape reveals
a 165-million-year-old secret.

335
00:22:44,158 --> 00:22:47,618
One thing that really strikes me,
actually, is the deep impression

336
00:22:47,618 --> 00:22:52,038
that this front toe has made,
and how pointed it is,

337
00:22:52,038 --> 00:22:55,665
and this tells me that this dinosaur
was moving at a fast speed

338
00:22:55,665 --> 00:22:58,375
and really pushing down
on its front three toes,

339
00:22:58,375 --> 00:23:02,461
so it might have been chasing
some kind of prey.

340
00:23:04,254 --> 00:23:06,880
(SCREECHING)

341
00:23:06,880 --> 00:23:08,673
But megalosaurus
wasn't the only dinosaur

342
00:23:08,673 --> 00:23:13,884
to leave its footprints in these rocks
only 60 miles from Loch Ness.

343
00:23:18,179 --> 00:23:23,348
This the smallest dinosaur footprint that
anybody has ever found in the world.

344
00:23:23,348 --> 00:23:26,058
You can actually see
it's about the size of my fingernail.

345
00:23:26,058 --> 00:23:29,269
And we think it's a coelophysis,
and it's quite interesting

346
00:23:29,269 --> 00:23:33,062
because the small footprint here,
which we think is from a hatchling,

347
00:23:33,062 --> 00:23:36,190
is embedded in the larger one
here that you can see.

348
00:23:36,190 --> 00:23:37,899
What we think this tells us

349
00:23:37,899 --> 00:23:40,567
is that the young travelled
with their parents in groups

350
00:23:40,567 --> 00:23:44,652
and that most probably that adults
were looking after the young.

351
00:23:46,738 --> 00:23:49,364
Geologists have used
the amazing evidence

352
00:23:49,364 --> 00:23:52,240
of the footprints of coelophysis
and megalosaurus,

353
00:23:52,240 --> 00:23:54,617
together with the muddy rocks
they were found in,

354
00:23:54,617 --> 00:23:59,703
to better reveal the story of Loch Ness
in the Jurassic period.

355
00:24:01,246 --> 00:24:04,874
At the time, Scotland was
still attached to America.

356
00:24:04,874 --> 00:24:09,460
Plate tectonics had driven this land mass
much nearer the equator,

357
00:24:09,460 --> 00:24:12,420
2,000 miles further south than it is now.

358
00:24:12,420 --> 00:24:17,339
And that had a major effect on the
climate and environment of Loch Ness.

359
00:24:17,339 --> 00:24:18,882
Back during
the Jurassic times,

360
00:24:18,882 --> 00:24:22,843
the climate and the environment was
very, very different to what we see today.

361
00:24:22,843 --> 00:24:27,095
There would have been lush jungles
full of tropical vegetation

362
00:24:27,095 --> 00:24:30,389
and the dinosaurs would have been
living on the edge of these jungles,

363
00:24:30,389 --> 00:24:32,890
travelling over lagoonal type
of wetlands.

364
00:24:32,890 --> 00:24:36,100
This climate was ideal
for dinosaurs to live in,

365
00:24:36,100 --> 00:24:39,561
because it supported
a huge ecosystem of wildlife

366
00:24:39,561 --> 00:24:42,021
that they would have predated on.

367
00:24:44,063 --> 00:24:45,898
The bones of one more dinosaur

368
00:24:45,898 --> 00:24:48,649
have recently been found
on the Isle of Skye -

369
00:24:48,649 --> 00:24:51,109
the plesiosaur.

370
00:24:52,569 --> 00:24:56,613
But this discovery generated
a completely different kind of interest.

371
00:24:59,406 --> 00:25:03,367
Enthusiasts see a strong resemblance
between the shape of the plesiosaur

372
00:25:03,367 --> 00:25:06,327
and some descriptions
of the Loch Ness monster.

373
00:25:08,996 --> 00:25:11,413
Could a descendant
of the long-extinct plesiosaur

374
00:25:11,413 --> 00:25:14,624
really be the source of the legend?

375
00:25:14,624 --> 00:25:16,542
(GROWLS)

376
00:25:16,542 --> 00:25:19,626
The evidence to unravel the
extraordinary geological history

377
00:25:19,626 --> 00:25:21,753
of Loch Ness is getting stronger.

378
00:25:21,753 --> 00:25:25,922
The findings of megalosaurus
and coelophysis footprints

379
00:25:25,922 --> 00:25:31,300
prove that dinosaurs lived in Scotland
165 million years ago,

380
00:25:31,300 --> 00:25:34,553
and that Loch Ness was then
a sub-tropical paradise,

381
00:25:34,553 --> 00:25:38,055
2,000 miles further south
than it is today.

382
00:25:38,055 --> 00:25:40,139
But about 60 million years ago,

383
00:25:40,139 --> 00:25:43,808
five million years after
the dinosaurs became extinct,

384
00:25:43,808 --> 00:25:48,143
plate tectonics would tear
Loch Ness and America apart.

385
00:25:56,231 --> 00:25:59,150
The investigation into how Loch Ness
was made

386
00:25:59,150 --> 00:26:02,652
now moves forward to a time
60 million years ago.

387
00:26:02,652 --> 00:26:06,488
Scotland and America
are still firmly joined together.

388
00:26:06,488 --> 00:26:12,116
The next question is, when and how
did they become separated?

389
00:26:13,784 --> 00:26:16,911
On the Isle of Skye,
the landscape is full of evidence

390
00:26:16,911 --> 00:26:21,748
which can unlock the secrets of this
turbulent period in Scotland's past.

391
00:26:23,790 --> 00:26:28,085
At Talisker Bay, the massive
sea cliffs provide the first clue

392
00:26:28,085 --> 00:26:30,294
to the events that devastated the region.

393
00:26:30,294 --> 00:26:33,796
They're made entirely of volcanic lava.

394
00:26:34,255 --> 00:26:36,422
I'm standing here on a single lava flow,

395
00:26:36,422 --> 00:26:39,341
and this lava flow
is only about ten feet thick.

396
00:26:39,341 --> 00:26:46,054
But this whole cliff above me is made up
of lava flows, maybe 150 feet or more,

397
00:26:46,054 --> 00:26:49,430
and stretching for miles in all directions.

398
00:26:49,430 --> 00:26:52,224
Now, these lava flows
are composed of basalt,

399
00:26:52,224 --> 00:26:56,727
that's the same type of rock
that is being erupted today

400
00:26:56,727 --> 00:27:00,104
from modern volcanoes
like Hawaii or Iceland.

401
00:27:04,815 --> 00:27:09,109
Geologists have calculated
that these basalt lavas on Skye

402
00:27:09,109 --> 00:27:11,736
are about 60 million years old,

403
00:27:11,736 --> 00:27:14,946
but where is the volcano
which erupted them?

404
00:27:16,822 --> 00:27:21,324
The clue comes from a range of
mountains on the southern tip of Skye,

405
00:27:21,324 --> 00:27:24,077
the Cuillin hills.

406
00:27:24,077 --> 00:27:26,786
It's the type of rock that
makes up these craggy peaks

407
00:27:26,786 --> 00:27:29,621
which provide the evidence.

408
00:27:29,621 --> 00:27:32,248
They're made
of a rock called gabbro.

409
00:27:32,248 --> 00:27:35,291
Now, these are
the same chemical composition

410
00:27:35,291 --> 00:27:38,335
as the basalt that's been
erupted on to the surface,

411
00:27:38,335 --> 00:27:39,919
but there's a difference.

412
00:27:39,919 --> 00:27:43,713
The basalt that was erupted
was cooled very quickly

413
00:27:43,713 --> 00:27:45,673
because it was exposed to the air.

414
00:27:45,673 --> 00:27:48,299
Geologists call that fine-grained.

415
00:27:48,299 --> 00:27:51,427
On the other hand,
the magma that was trapped

416
00:27:51,427 --> 00:27:55,220
maybe a mile down beneath the Earth's
surface, that cooled pretty slowly,

417
00:27:55,220 --> 00:27:57,596
it was kept warm
for quite a long time,

418
00:27:57,596 --> 00:27:59,722
and so you've got
very large crystals growing.

419
00:27:59,722 --> 00:28:01,933
And when you get a rock
with large crystals,

420
00:28:01,933 --> 00:28:04,059
that's what we call coarse-grained.

421
00:28:06,852 --> 00:28:10,772
The large crystals in the gabbro rocks
give away their origin.

422
00:28:10,772 --> 00:28:14,107
They tell geologists that the Cuillin hills
are the remains

423
00:28:14,107 --> 00:28:17,651
of an enormous magma chamber
deep below the volcano,

424
00:28:17,651 --> 00:28:21,986
where lava was stored
before being erupted on to the surface.

425
00:28:23,904 --> 00:28:26,530
But how much lava was there?

426
00:28:26,530 --> 00:28:28,574
We may be looking now

427
00:28:28,574 --> 00:28:30,450
at a beautiful green valley,

428
00:28:30,450 --> 00:28:34,036
but actually all these hills around here
are made up of rocks

429
00:28:34,036 --> 00:28:37,329
that were formed in a series
of massive volcanic eruptions,

430
00:28:37,329 --> 00:28:39,455
about 60 million years ago.

431
00:28:39,455 --> 00:28:43,666
And at that time, there were volcanoes
erupting all over Scotland.

432
00:28:43,666 --> 00:28:47,043
Here we are on Skye
and it's just one of those volcanoes.

433
00:28:50,170 --> 00:28:55,089
It's now known that an
incredible 500 cubic miles of lava

434
00:28:55,089 --> 00:28:58,133
was erupted on Skye alone.

435
00:28:59,634 --> 00:29:05,137
That's enough to cover the whole of
Texas with a layer of lava ten feet thick.

436
00:29:08,639 --> 00:29:10,932
But this was just the tip of the iceberg.

437
00:29:10,932 --> 00:29:15,602
The rocks themselves reveal that
volcanoes erupted all over Scotland

438
00:29:15,602 --> 00:29:17,103
on a massive scale.

439
00:29:18,145 --> 00:29:19,938
The evidence is here.

440
00:29:19,938 --> 00:29:23,023
Huge, regular columns in the lava flows,

441
00:29:23,023 --> 00:29:26,108
looking like they've been
carved out of the rock.

442
00:29:26,108 --> 00:29:31,528
In reality, these amazing formations are
made by gentle cooling of thick lavas.

443
00:29:32,612 --> 00:29:36,656
Exactly the same type of columns
are found in outcrops

444
00:29:36,656 --> 00:29:41,951
of basalt lava 80 miles away
off the west coast of Scotland,

445
00:29:41,951 --> 00:29:48,830
and as far away as the coast of Ireland,
150 miles from Skye.

446
00:29:48,830 --> 00:29:52,624
These lavas have all been
dated at about 60 million years old,

447
00:29:52,624 --> 00:29:56,627
and they were also part of the
same series of massive eruptions

448
00:29:56,627 --> 00:29:59,587
which spread out for hundreds of miles
in all directions.

449
00:29:59,587 --> 00:30:02,964
But what was the cause
of the eruptions?

450
00:30:02,964 --> 00:30:05,340
Dr Goodenough has found another clue

451
00:30:05,340 --> 00:30:07,883
which points to the origins
of these lavas,

452
00:30:07,883 --> 00:30:11,427
and their role in the creation
of Loch Ness.

453
00:30:11,427 --> 00:30:14,721
This is the ropey top
to a lava flow.

454
00:30:14,721 --> 00:30:16,889
In Hawaii they call it pahoehoe.

455
00:30:16,889 --> 00:30:22,517
And what happens is that the lava gets
a thin skin on its surface as it cools,

456
00:30:22,517 --> 00:30:24,935
but it's still flowing underneath that skin.

457
00:30:24,935 --> 00:30:28,021
And the thin skin wrinkles
and gets pushed forward,

458
00:30:28,021 --> 00:30:30,605
giving this ropey texture
that we can see here.

459
00:30:30,605 --> 00:30:34,149
But it's really quite rare to see them
like this in these old lava flows.

460
00:30:34,149 --> 00:30:37,025
But it tells us a lot
about the type of magma

461
00:30:37,025 --> 00:30:39,360
that was erupting from that volcano.

462
00:30:41,778 --> 00:30:46,115
Geologists know that this kind of magma
comes from deep within the Earth.

463
00:30:46,115 --> 00:30:48,408
It usually erupts on the surface

464
00:30:48,408 --> 00:30:51,785
when tectonic forces split
the Earth's crust apart.

465
00:30:51,785 --> 00:30:55,537
Is that what happened here,
60 million years ago?

466
00:30:55,537 --> 00:30:59,373
GOODENOUGH: At that time, Scotland
was still joined to North America,

467
00:30:59,373 --> 00:31:02,875
but the two continents
were being stretched and thinned,

468
00:31:02,875 --> 00:31:04,751
due to tectonic forces.

469
00:31:04,751 --> 00:31:09,212
And that allowed molten rock,
or magma, from deep within the Earth

470
00:31:09,212 --> 00:31:12,255
to well up and to be erupted
from those volcanoes,

471
00:31:12,255 --> 00:31:16,633
and eventually that volcanic activity
led to the development of a new ocean

472
00:31:16,633 --> 00:31:20,302
between Scotland and North America,
the Atlantic Ocean.

473
00:31:21,803 --> 00:31:24,262
So the lavas are the trail of evidence

474
00:31:24,262 --> 00:31:26,973
which show that the opening up
of the Atlantic Ocean

475
00:31:26,973 --> 00:31:31,266
began with volcanic eruptions
all over Scotland.

476
00:31:32,310 --> 00:31:36,436
As magma erupted under the ocean,
the sea floor spread out,

477
00:31:36,436 --> 00:31:40,898
slowly pushing Scotland
and America apart.

478
00:31:40,898 --> 00:31:43,774
The birth of the Atlantic Ocean
had a direct effect

479
00:31:43,774 --> 00:31:45,734
on the making of Loch Ness.

480
00:31:45,734 --> 00:31:50,111
As the ocean grew, the huge
forces involved reawakened

481
00:31:50,111 --> 00:31:54,072
the 400-million-year-old
Great Glen Fault.

482
00:31:54,072 --> 00:31:56,241
So faults
like the Great Glen,

483
00:31:56,241 --> 00:31:58,825
these are zones of weakness
in Earth's crust

484
00:31:58,825 --> 00:32:02,327
and they're like scars or wounds,
they can reopen.

485
00:32:02,327 --> 00:32:04,829
And in the case of the Great Glen,

486
00:32:04,829 --> 00:32:08,248
it was reactivated
when the Atlantic began opening

487
00:32:08,248 --> 00:32:10,082
50 to 60 million years ago.

488
00:32:10,082 --> 00:32:15,168
And this is why you see this feature
now present in today's landscape,

489
00:32:15,168 --> 00:32:18,170
even though the fault itself
is 400 million years old.

490
00:32:18,170 --> 00:32:21,172
The massive geological
movements shattered

491
00:32:21,172 --> 00:32:23,465
and weakened the rocks along the fault.

492
00:32:23,465 --> 00:32:25,758
Along this line of weakness,

493
00:32:25,758 --> 00:32:28,635
a river started cutting down
through the shattered rocks,

494
00:32:28,635 --> 00:32:30,595
slowly carving out a valley.

495
00:32:32,470 --> 00:32:34,972
For the next 55 million years,

496
00:32:34,972 --> 00:32:38,683
the landscape of Scotland
weathered and eroded.

497
00:32:38,683 --> 00:32:40,809
The outlines of the mountains softened,

498
00:32:40,809 --> 00:32:44,769
and the coastline began
to take on its present shape.

499
00:32:44,769 --> 00:32:50,648
Loch Ness became a long river valley,
following the line of the Great Glen Fault.

500
00:32:52,566 --> 00:32:55,985
The investigation is close to
uncovering the final stages

501
00:32:55,985 --> 00:32:58,778
in the story of how
Loch Ness was made.

502
00:32:58,778 --> 00:33:04,323
Huge lava flows on the Isle of Skye
reveal that massive volcanic eruptions

503
00:33:04,323 --> 00:33:07,449
60 million years ago
were the start of the separation

504
00:33:07,449 --> 00:33:10,410
of Scotland and America.

505
00:33:10,410 --> 00:33:14,579
The sharp outline of the
400-million-year-old Great Glen Fault

506
00:33:14,579 --> 00:33:19,957
shows that the fault was reawakened as
Scotland and America were torn apart.

507
00:33:21,250 --> 00:33:25,961
But there was one final
land-changing event to come.

508
00:33:25,961 --> 00:33:27,878
Nature wasn't finished with Loch Ness,

509
00:33:27,878 --> 00:33:32,548
and it was this event
that created the lake we see today.

510
00:33:36,301 --> 00:33:40,512
Tracing a violent history
that lasted for three billion years,

511
00:33:40,512 --> 00:33:42,971
the investigation into how Loch Ness
was made

512
00:33:42,971 --> 00:33:48,683
now moves forward to the recent past,
only 10,000 years ago.

513
00:33:49,767 --> 00:33:53,019
The final link in the chain
of evidence is to discover

514
00:33:53,019 --> 00:33:56,437
how the wide, deep waters
of Loch Ness were finally made,

515
00:33:56,437 --> 00:33:59,565
and whether a descendant
of the dinosaurs

516
00:33:59,565 --> 00:34:01,190
could possibly have survived there

517
00:34:01,190 --> 00:34:04,567
to create the myth
of the Loch Ness monster.

518
00:34:05,818 --> 00:34:08,945
A vital clue was uncovered
in the 19th century

519
00:34:08,945 --> 00:34:12,864
by one of the greatest scientific minds
the world has ever known,

520
00:34:12,864 --> 00:34:15,324
Charles Darwin.

521
00:34:15,324 --> 00:34:18,201
In 1838, Darwin came to Scotland

522
00:34:18,201 --> 00:34:20,619
to investigate a mystery
in the remote valley

523
00:34:20,619 --> 00:34:24,621
of Glen Roy, about 20 miles
from Loch Ness.

524
00:34:26,456 --> 00:34:28,082
For hundreds of years,

525
00:34:28,082 --> 00:34:31,626
people had been baffled
by three extraordinary parallel lines

526
00:34:31,626 --> 00:34:34,877
which run round both sides
of the valley -

527
00:34:34,877 --> 00:34:41,423
strange horizontal cuts in the hillside,
in some places more than 30 feet wide.

528
00:34:41,423 --> 00:34:44,842
These Parallel Roads,
as they are called,

529
00:34:44,842 --> 00:34:47,718
run exactly level for more than 20 miles.

530
00:34:47,718 --> 00:34:49,762
What could have made them?

531
00:34:51,513 --> 00:34:53,639
Dr Pete Nienow is following
in Darwin's footsteps

532
00:34:53,639 --> 00:34:58,850
to the Glen Roy Parallel Roads
and the story they reveal.

533
00:34:59,976 --> 00:35:02,352
Their creation was a mystery
for a very long time

534
00:35:02,352 --> 00:35:04,687
and initially people, you know,
just thought they were,

535
00:35:04,687 --> 00:35:08,147
you know, perhaps created by giants,
a thing of myth or legend.

536
00:35:08,147 --> 00:35:11,816
And then in the... in the 19th century,
a number of scientists came here,

537
00:35:11,816 --> 00:35:14,568
including Charles Darwin,
and when he saw them,

538
00:35:14,568 --> 00:35:16,611
he thought they were exactly the same

539
00:35:16,611 --> 00:35:18,862
as features he'd seen
in South America,

540
00:35:18,862 --> 00:35:22,656
where earthquakes had uplifted
old marine shorelines

541
00:35:22,656 --> 00:35:24,824
and left them abandoned
higher up from the sea.

542
00:35:26,742 --> 00:35:28,243
Darwin was so convinced

543
00:35:28,243 --> 00:35:31,036
the Parallel Roads were
the remains of old seashores

544
00:35:31,036 --> 00:35:33,371
that he published a paper
with his results,

545
00:35:33,371 --> 00:35:35,413
and the world of science believed him.

546
00:35:37,332 --> 00:35:40,834
But for once, Darwin was wrong.

547
00:35:40,834 --> 00:35:44,378
In 1840, two years after Darwin's visit,

548
00:35:44,378 --> 00:35:48,171
a Swiss scientist named Louis Agassiz
came to Glen Roy.

549
00:35:49,922 --> 00:35:52,299
Agassiz had spent a lifetime
studying glaciers

550
00:35:52,299 --> 00:35:56,926
and the effects of glaciation
on the landscape of the Swiss Alps.

551
00:36:01,263 --> 00:36:03,430
When he examined the parallel roads,

552
00:36:03,430 --> 00:36:06,849
Agassiz realised that
they were ancient shorelines,

553
00:36:06,849 --> 00:36:09,726
but that the valley had been
filled not by the sea,

554
00:36:09,726 --> 00:36:12,686
but by a freshwater lake.

555
00:36:14,896 --> 00:36:17,231
From his knowledge of glaciers
in the Alps,

556
00:36:17,231 --> 00:36:19,899
Agassiz was able to show
that a freshwater lake

557
00:36:19,899 --> 00:36:21,483
had once filled the valley.

558
00:36:23,150 --> 00:36:28,238
The lake was kept full by a huge glacier
which blocked the end of the valley.

559
00:36:28,238 --> 00:36:31,489
As the glacier melted and froze again
three times,

560
00:36:31,489 --> 00:36:35,366
the water in the valley emptied
and filled up to a different level,

561
00:36:35,366 --> 00:36:38,410
carving out the three relic beaches.

562
00:36:39,452 --> 00:36:41,912
Initially, Agassiz wasn't believed,
'cause people believed Darwin,

563
00:36:41,912 --> 00:36:45,206
and then over time it became clear
that Agassiz was correct

564
00:36:45,206 --> 00:36:48,416
and Darwin claimed, you know,
it was one of his great embarrassments

565
00:36:48,416 --> 00:36:50,793
that he'd got something
so terribly wrong,

566
00:36:50,793 --> 00:36:52,544
which sort of shows that, you know,

567
00:36:52,544 --> 00:36:54,420
even great scientists
can make mistakes.

568
00:36:55,629 --> 00:36:58,589
The evidence at Glen Roy convinced
Agassiz that many features

569
00:36:58,589 --> 00:37:02,216
in the Scottish landscape
must have been made by glaciers.

570
00:37:02,216 --> 00:37:06,135
And that led him to the startling
conclusion at the time,

571
00:37:06,135 --> 00:37:09,512
that the whole of Scotland
had once been covered by ice.

572
00:37:11,389 --> 00:37:13,264
The moment
you make that leap

573
00:37:13,264 --> 00:37:15,724
that what you've got here
was created by glaciers,

574
00:37:15,724 --> 00:37:17,600
you've instantly got to make the leap
to the fact

575
00:37:17,600 --> 00:37:20,060
that we must have had
a very cold climate here in the past,

576
00:37:20,060 --> 00:37:24,146
cold enough for... for ice sheets
and glaciers to... to build up.

577
00:37:24,146 --> 00:37:26,439
This site is... is of... of world importance

578
00:37:26,439 --> 00:37:29,399
in terms of the understanding
of glaciations

579
00:37:29,399 --> 00:37:31,484
and the... you know,
the... the fact that, in the past,

580
00:37:31,484 --> 00:37:35,444
ice covered a much larger proportion
of the planet than it currently covers.

581
00:37:36,653 --> 00:37:41,615
This extraordinary investigation led
eventually to the idea of the Ice Age,

582
00:37:41,615 --> 00:37:45,617
periods in the geological past when
much of the northern hemisphere

583
00:37:45,617 --> 00:37:48,869
was covered in glaciers and ice sheets.

584
00:37:50,329 --> 00:37:55,164
Since Agassiz's discoveries, scientists
have been investigating the role of ice

585
00:37:55,164 --> 00:37:56,915
in making Loch Ness.

586
00:37:56,915 --> 00:38:00,417
About two and a half million years ago,
the global climate started to cool

587
00:38:00,417 --> 00:38:03,712
and since then we've had a series
of repeated glaciations,

588
00:38:03,712 --> 00:38:06,505
roughly about once every 100,000 years.

589
00:38:08,089 --> 00:38:11,591
Each time the ice advanced,
temperatures plummeted.

590
00:38:11,591 --> 00:38:15,551
Average winter temperatures were
at least 30 degrees colder than today.

591
00:38:15,551 --> 00:38:19,513
As the ice built up, it reached
extraordinary thicknesses.

592
00:38:20,722 --> 00:38:22,764
The ice sheet over
the centre of Scotland

593
00:38:22,764 --> 00:38:24,974
would have been three
or four thousand feet thick.

594
00:38:24,974 --> 00:38:26,641
And here in Loch Ness,

595
00:38:26,641 --> 00:38:30,019
it would have certainly been
a couple of thousand feet thick.

596
00:38:30,019 --> 00:38:32,687
You might have seen a few
of the highest mountains

597
00:38:32,687 --> 00:38:34,480
just peeking out the top of the ice sheet,

598
00:38:34,480 --> 00:38:36,564
but in the main,
the whole of the landscape

599
00:38:36,564 --> 00:38:38,982
would have just been
blanketed by... by ice.

600
00:38:40,859 --> 00:38:46,362
But what effect did this vast weight of ice
have on the creation of Loch Ness?

601
00:38:46,362 --> 00:38:49,989
The loch itself is difficult to investigate,
because it's full of water.

602
00:38:49,989 --> 00:38:53,783
But there's another location
where the evidence is clear.

603
00:38:53,783 --> 00:38:58,536
Just 20 miles from Loch Ness
is the forbidding valley of Glencoe.

604
00:39:00,662 --> 00:39:03,122
Glencoe is a legendary place
in Scottish history,

605
00:39:03,122 --> 00:39:07,958
as it was here that an infamous
massacre took place in 1692,

606
00:39:07,958 --> 00:39:10,918
when the MacDonald clan
were murdered in their beds

607
00:39:10,918 --> 00:39:12,545
by the Campbells.

608
00:39:14,504 --> 00:39:19,048
The shape of this valley sheds light
on the way Loch Ness was made.

609
00:39:19,048 --> 00:39:22,133
If you could actually drain
the water out of Loch Ness,

610
00:39:22,133 --> 00:39:26,595
what you'd actually end up with
is a valley with this sort of shape.

611
00:39:26,595 --> 00:39:28,179
And looking down Glencoe

612
00:39:28,179 --> 00:39:31,931
you can see it's a very, very steep-sided,
flat-bottomed valley

613
00:39:31,931 --> 00:39:35,058
and it's basically been created
by glaciers

614
00:39:35,058 --> 00:39:37,184
repeatedly flowing down the valley,

615
00:39:37,184 --> 00:39:41,062
eroding it and basically gouging out
what was originally a V-shaped valley

616
00:39:41,062 --> 00:39:43,355
and turning it into
an over-deepened U-shaped valley.

617
00:39:45,231 --> 00:39:48,274
Glaciers are extremely efficient
at eroding the landscape.

618
00:39:48,274 --> 00:39:50,525
They pick up vast amounts
of rock debris,

619
00:39:50,525 --> 00:39:53,736
which is carried along at the base
of the glacier.

620
00:39:53,736 --> 00:39:57,155
With the weight of millions
of tons of ice on top of it,

621
00:39:57,155 --> 00:40:00,907
this rock debris grinds away the bedrock
like sandpaper,

622
00:40:00,907 --> 00:40:05,117
scouring and deepening the valleys
to a characteristic U shape.

623
00:40:07,328 --> 00:40:09,203
Across Scotland,
there are hundreds of valleys

624
00:40:09,203 --> 00:40:10,954
with this distinctive U shape,

625
00:40:10,954 --> 00:40:14,040
bearing witness
to the huge number of glaciers

626
00:40:14,040 --> 00:40:17,083
which once covered this whole region.

627
00:40:19,418 --> 00:40:21,753
At Loch Ness,
underwater mapping has revealed

628
00:40:21,753 --> 00:40:24,671
that the loch
has this signature U shape.

629
00:40:24,671 --> 00:40:28,632
It's flat-bottomed, with very steep sides.

630
00:40:28,632 --> 00:40:31,341
In some places only 50 feet
from the shoreline,

631
00:40:31,341 --> 00:40:33,385
the water is over 500 feet deep,

632
00:40:33,385 --> 00:40:38,471
further proof that Loch Ness was made
by a glacier.

633
00:40:38,471 --> 00:40:40,514
There was already a long river valley

634
00:40:40,514 --> 00:40:42,515
which had formed
along the line of weakness

635
00:40:42,515 --> 00:40:46,517
created by the shattered rocks
along the Great Glen Fault.

636
00:40:46,517 --> 00:40:49,436
Then, during the last Ice Age,

637
00:40:49,436 --> 00:40:54,981
a giant glacier flowed down the valley,
slowly carving out Loch Ness.

638
00:40:54,981 --> 00:40:58,400
As ice flows down it, it scours it out,
deepens it

639
00:40:58,400 --> 00:41:00,693
and over a... over
a series of glaciations

640
00:41:00,693 --> 00:41:04,987
it deepens it to the extent that it's now,
you know, a loch 750 feet deep.

641
00:41:06,946 --> 00:41:10,741
The investigation is now faced
with two final questions.

642
00:41:10,741 --> 00:41:13,992
How did Loch Ness
fill up with freshwater?

643
00:41:13,992 --> 00:41:15,536
And what keeps it full?

644
00:41:16,744 --> 00:41:21,205
Loose rock and boulders found
on a huge ridge 250 feet high

645
00:41:21,205 --> 00:41:24,624
at the head of the loch
could provide the answer.

646
00:41:26,375 --> 00:41:30,210
The immediately obvious thing
about these large rocks

647
00:41:30,210 --> 00:41:32,670
is that they're extremely smooth
and well-rounded

648
00:41:32,670 --> 00:41:35,923
and that indicates that they've
been transported by... by water.

649
00:41:35,923 --> 00:41:39,425
They're also very large, this is very
heavy, so you need a lot of energy,

650
00:41:39,425 --> 00:41:42,468
so that tells you that you've got
a lot of meltwater that's carried it

651
00:41:42,468 --> 00:41:45,470
and then subsequently dumped it
where we are now.

652
00:41:47,304 --> 00:41:50,848
This evidence, combined
with discoveries about climate change,

653
00:41:50,848 --> 00:41:52,974
shows what happened here.

654
00:41:52,974 --> 00:41:57,685
About 10,000 years ago,
global temperatures rose rapidly,

655
00:41:57,685 --> 00:42:01,396
the ice began to melt,
and the glaciers retreated.

656
00:42:01,396 --> 00:42:05,899
Glaciers down there would
have been eroding Loch Ness,

657
00:42:05,899 --> 00:42:07,691
bringing up large amounts
of sediment

658
00:42:07,691 --> 00:42:11,027
and that sediment is then
being transported in this direction

659
00:42:11,027 --> 00:42:14,696
by the... by the flowing ice
and also by flowing meltwater.

660
00:42:16,363 --> 00:42:21,075
As the ice melted, a huge river
formed under the Loch Ness glacier,

661
00:42:21,075 --> 00:42:24,076
carrying with it vast amounts
of rock debris.

662
00:42:24,076 --> 00:42:28,204
And then what we've got here, what
we're standing on is in effect the zone

663
00:42:28,204 --> 00:42:30,664
where the glacier is now
dumping that sediment.

664
00:42:32,039 --> 00:42:35,167
Millions of tons of rocks
created an enormous plug

665
00:42:35,167 --> 00:42:39,460
which dammed the river
and stopped the water from escaping.

666
00:42:39,460 --> 00:42:42,962
As the ice melted,
the valley filled up,

667
00:42:42,962 --> 00:42:46,631
finally making the lake
we know as Loch Ness.

668
00:42:47,966 --> 00:42:50,968
Loch Ness is only 10,000 years old,

669
00:42:50,968 --> 00:42:55,303
but the investigation into its history
has revealed an amazing story.

670
00:42:55,303 --> 00:42:58,680
Old red sandstone rocks
show that Scotland and the US

671
00:42:58,680 --> 00:43:00,556
were once joined together.

672
00:43:00,556 --> 00:43:04,476
The shape of Loch Ness
is controlled by the Great Glen Fault,

673
00:43:04,476 --> 00:43:08,061
formed when Scotland and America
crashed into England

674
00:43:08,061 --> 00:43:11,146
more than 400 million years ago.

675
00:43:11,146 --> 00:43:15,357
Fossilised dinosaur footprints
place Loch Ness near the equator

676
00:43:15,357 --> 00:43:17,900
during the Jurassic period.

677
00:43:17,900 --> 00:43:22,362
Lava flows reveal that massive
volcanic eruptions 60 million years ago

678
00:43:22,362 --> 00:43:26,406
began the separation
of Scotland and America.

679
00:43:26,406 --> 00:43:28,115
And the profile of Loch Ness

680
00:43:28,115 --> 00:43:32,284
proves that it was carved out
by glaciers 10,000 years ago,

681
00:43:32,284 --> 00:43:36,495
finally creating the Loch Ness
we know today.

682
00:43:36,495 --> 00:43:40,122
But what of the Loch Ness monster?

683
00:43:40,122 --> 00:43:43,624
The iconic image
is now known to be a fake.

684
00:43:43,624 --> 00:43:46,126
But is there any way
that the mythical beast

685
00:43:46,126 --> 00:43:49,169
could be a descendant of the dinosaurs?

686
00:43:49,169 --> 00:43:52,046
We have two
geological facts

687
00:43:52,046 --> 00:43:53,881
that tell us that Loch Ness

688
00:43:53,881 --> 00:43:56,299
could not be inhabited by a dinosaur -

689
00:43:56,299 --> 00:44:00,385
one is the dinosaurs died a long, long,
long time ago,

690
00:44:00,385 --> 00:44:04,303
and the loch itself, geologically,
is very young.

691
00:44:04,303 --> 00:44:07,347
Dinosaurs went extinct
65 million years ago.

692
00:44:07,347 --> 00:44:12,058
So, 65 million years to 10,000 years,

693
00:44:12,058 --> 00:44:16,519
it's a long time distance and there is
no chance at all that you would have,

694
00:44:16,519 --> 00:44:19,563
preserved in this loch,
an ancient monster

695
00:44:19,563 --> 00:44:21,605
from times millions of years ago.

696
00:44:21,605 --> 00:44:23,273
The loch's too young.

697
00:44:23,273 --> 00:44:25,816
(GROWLS)

698
00:44:26,900 --> 00:44:30,152
So the geological evidence
proves that Loch Ness

699
00:44:30,152 --> 00:44:33,904
could not be home to a dinosaur
that somehow survived there

700
00:44:33,904 --> 00:44:36,364
since the Jurassic.

701
00:44:36,364 --> 00:44:42,660
The awesome geological history of Loch
Ness has thrown up many mysteries.

702
00:44:42,660 --> 00:44:46,537
But for science, the Loch Ness monster
is not one of them.