100 Greatest Discoveries (2004) s01e04 Episode Script
Earth Sciences
A journey to the center of the earth, where temperature are thirteen thousands degrees Fahrenheit Hotter than the surface of the sun.
The most powerful force on the face of the planet.
Moving whole continents Creating mountains, exploding them apart.
And unimaginable winter of ice lasting a hundred thousand years.
Some of the greatest discovery in the history of science, have revealed what an incredibly complex and dynamic planet we live on.
Discoveries that opened our eyes, changing how we see the sky above and earth blow.
In March 1980, geologists detected a serious of small earthquakes here, beneath mountain St.
Helens in Washington State.
It was a signal that the long dormant volcano was waking up.
Finally on the morning of May eighteenth, it did.
Mountain St.
Helens had erupted with the force five hundred times the atomic bomb that was dropped on Hiroshima A cloud of hot ash roared fifteen miles into the atmosphere 230 square mile of forests were wiped out.
Six million trees, enough wood to build three hundred thousand two storey houses Throughout recorded history, civilization has lived with the threat of earthquakes and volcanoes But the cause of their destructed power remained elusive, shrouded in mystery.
It wasn't until our first great discovery that a picture of what was happening inside the earth began to emerge.
For centuries, most of what we knew the earth's interior came from mining operation like this one.
It wasn't until scientists began using seismograph to study earthquakes.
That they gained more accurate understanding of the insight of the earth.
When an earthquake occurred, seismograph measured the speed and intensity of the seismic waves that vibrated underground.
Using this method, scientists identified different layers inside the earth.
Each one characterized by changes and rock density.
For example, the first layer was the crust, a skin of rock covering the planet.
As for what was blow that A breakthrough discovery provided the first clue.
In 1906, British geologist Richard Altman was analyzing seismographic reading caused by a large earthquake.
When he saw something odd.
As the vibration from earthquake reverberated, they didn't arrive at the center of the earth as expected.
It was as if they hit an obstacle.
Altman realized the obstacle must be the inner most part of the earth.
A dense mass hard enough to reflected seismic waves from going all the way through.
Altman had discovered the earth's core.
It was a landmark discovery because it set the stage for the work of another scientist Who is about to help revolutionized our understanding of what was happening inside the earth.
With Altman's discovery, many believed that picture of the earth's core was complete.
But in the early 1930, Inge Lehmann wasn't so sure.
Lehmann was a Danish seismologist, who worked extensively in Denmark and Greenland.
Studding the velocity seismic waves from earthquakes In 1936, she was analyzing the seismic waves from an earthquake that had occurred several years earlier.
Seismological stations around the world had made recording of the same quake.
By comparing their readings, Lehmann calculated that the seismic waves had passed through the earth's core.
There was a change in their velocity.
As if they had encountered another boundary of some kind.
Then it occurred to her.
Something was missing from accepted structure of the earth's interior.
The core that Lehman had found was the earth's inner core.
Today, through precise seismic measurements, we know that it is made of solid iron.
Solid because gravity at center of the earth created a pressure The core that Richard Altman had discovered turned out to be the earth's outer core.
It's made of liquid iron and other elements.
A hot churning mass that generates electric currents, which in turn created the magnet field that, protects the earth from dangerous cosmic radiation.
Slightly larger than the planet mars.
I caught up with Doc.
Catherin Johnson, a professor of geophysics doing field research at a mine location in southern California.
What made the earth hotter at the first place The earth's original heat actually came from how the earth formed.
It formed through collisions of small bodies we call then planetesimals The collisions of these bodies released huge amounts of heat.
That came from astronomical distance.
It's right, just crashing to each other.
And turning all that kinetic energy into heat.
So, the heat is still here Yeah, and the heat is still here and there is also the heat with released actually during the formation of the earth's cores.
So all these bodies came together They are rocky.
They have bit of metals in them.
That metals settled within the earth to from.
Gravity.
Gravity, yes, just by gravity.
But the change in this gravitational energy going from near the surface of the earth to falling to the center, actually also released a lot of heat.
Why wasn't the earth cool off It hasn't cooled off because it actually cools very slowly.
That's seems perhaps surprising given hot But its original temperature was very very hot.
So it takes the earth's massive, so it takes a long time for it to cool.
It's why small planets like mars Even small like planetesimal bodies like moon have pretty much cooled off.
But here on earth, the cooling off the planet is perhaps billions of years away.
Thanks to the intense heat of the core, which acts as a kind of natural furnace.
What Altman and Lehmann didn't know was what else was this furnace was capable of.
And that's our next great discovery.
A meteorologist named Alfred Wegener was browsing through some books when something caught his eye.
A list of Atlantic plants and animal fossils that had been found on opposite sides of the Atlantic Ocean.
Wegener was intrigued.
How could the same species have gotten from one part of the world to another He examined the eastern coast of South America and the western coast of Africa.
And was struck out the shape of the two coastlines might fit together.
The more he looked the more links he found.
Species of land mammals and east Africa also inhabited in the island of Madagascar How did that happenDid the animals evolve at both places at once quiet please Or did they somehow cross from one land to the other, swimming hundreds of miles across the Indian Ocean.
And then Wegener saw all clearly He realized that all the continents in the world had once formed A giant single landmass that he called Pangaea from the Greek pangea meaning all earth.
It was in Pangaea that the plants and animals found on opposite sides of world had once shared the same home.
Then, over hundreds of millions of years, Pangaea had split apart And its jigsaw pieces had drifted to their present locations Wegener called his theory continental drift.
Wegener wasn't the first scientist to speculate that the earth had once been dominated by a super continent.
But he was the first to pore together all the evidence and make a strong case for it.
Unfortunately, his peers weren't very accept it.
There was no mechanism to explain how the continents might plow through the oceans Continental drift was just too incredible to believe.
As a result, his discovery was largely ignored.
Quiet down or get out of here.
World war two, German U-boat ran the proud To track them, the allied forced developed new sonar methods.
And scientists were enlisted to help survey the ocean floor.
When the United States entered the war, Harry Hess was a geology professor in Princeton University.
But he also happened to be a navy reservers.
So it wasn't long before he found himself command a tank transport ship in the pacific.
To help maneuver when coming in for a beach landing, Hass' ship was equipped with a depth sounder.
Still being a geologist at heart.
He used the sounder to measure the depth of the ocean floor whenever the ship was out to sea.
And what he discovered startled him Until the second would war, most scientists imagined the bottom of ocean look like this Flat wide with nothing but settlement.
Harry Hass discovered something else entirely.
Mountains, like these here in California with deep canyons and tranches Hundreds of high peeks that we now believe are once active volcanoes And all of these, at bottom of Pacific Ocean, surprisingly though, The discovery of the pacific mountain range was not made Harry Hass part of our great one hundred.
We will get to that in a minute.
To understand where all this headed.
Like to skip a height to another event that set the geology world buzzing For years, oceanographers surveyed the Atlantic Ocean.
And taken sonar readings that indicating there was something down there, something big.
They called it the Mid-Atlantic Ridge The reason it's so great To fills in, a paved a visit to Neal Driscoll.
A geologist at the Scripps institution of oceanography.
One of the big discoveries that was made was that there was this ridge of underwater volcanoes that stood high above the sea floor.
How high is the mountain in the mid-Atlantic The average sea floor depth around the order of about 4000-5000meters, mid-ocean ridge seize up about 2500 meters So, they about two half kilometers on average higher than the surrounding see floor that charly here in blue colors.
- So, that's over a mile high.
- Yes.
And that's where Harry Hass comes back into the story.
Analyzing course samples in sonar reading around mid-Atlantic ridge, Hass made an astonishing discovery.
A phenomena almost beyond comprehension.
The age of the Atlantic Ocean floor he determined was progressively older, the further moved away from the ridge Harry Hass has discovered that the sea floor was spreading.
He concluded that molten rock was being forced up from inside the earth.
And the ridge were then formed into new crust on the ocean floor.
Gradually was pushed away on either side as more molten rock continued pushing up from behind it.
Hass called his great discovery sea floor spreading.
Harry Hass was in a position that he could bring it altogether Things were spreading apart.
New earth was being generated But if you did this for long enough, the earth should grow And it doesn't.
Erath doesn't get any bigger.
No.
Harry appreciated the fact that if new earth was being generated in one area, There have to be consumed or recycled in another area The process that recycle the crust of the spreading ocean floor back inside the earth is called subduction.
But is our next great discovery revealed Is all part of a much larger process Perhaps most powerful forces on the face of the earth.
Hass's discovery that the sea floor was spreading Rescued Alfred Wegener's idea of Pangaea from obscurity.
Now there was the geological mechanism to explain continental drift.
That's simple.
Once you hear it, it does sound great.
By the nineteen sixties, both ideas were synthesized into a single theory, the science of plate tectonics A great discovery that revealed just how complex and dynamic our planet it is.
Several groups of scientists had concluded that not only is the earth's crust moving, but the surface of the planet is broken into large interconnected plates These plates are constantly in motion floating on the layer of molten rock in the earth's mantle.
This seems fantastic; I mean this seems just too crazy.
How could the whole world be sliding around.
I can see where people were suspecting.
Yes.
But it's the rates like your fingernail grow.
Not very fast.
I don't feel a thing.
That's right.
Accumulately, it's huge.
That here the thing is Geological time scales, it's what makes it so important because if you think of it over a year, you moved a few centimeters.
And think of millions of years, that you moving kilometers.
And they moving apart and they'll come back together.
Why they come back together Because the Pacific Ocean right now had subduction all around it.
And the plates is actually being consumed and recycled With the Atlantic ocean is spreading without much subduction.
So the Atlantic Ocean is kind of grow, the Pacific Ocean is kind of close And then will start getting closer, Asian and closing up the Pacific Ocean.
It's crazy.
.
It's pretty good One you hear it, it's hard to imagine geologist.
not believing it.
yes So once the theory and mechanism that was important contribution.
We can't believe it until yes So the plates are spreading.
They are not plowing , The understanding of the plate tectonics has given scientists new insights into the changing face of our planet.
A dynamic example of some of those changes can be seen here on the California coastline.
Where two of the earth's largest plates, the pacific and the North America, collide.
There are numbers of results.
But one we get volcanoes with the plates that subducted back into the earth.
These volcanoes happened because the plates get subducted, releases water And the water lowers the molten temperature of the overriding plates and Make it easier.
And we get volcanism, So that's really get to know Whitney, Mount Shasta, Mount.
Things like these, absolutely.
So the Andes are perfect example of this type of volcanoes.
Other places that you get the mid-ocean ridges, you get pieced of sea floor that were one to two kilometers higher than the surrounding sea floor.
These are underwater volcano chains that stretch the link of these ocean basins Other places you get large strike-slip fault So what's the strike-slip fault The strike-slip is when the plates move by one and another, and they don't do it without kinks and twists.
So, when the kinks and twists are, there can be places that lock And then they release and then they release quickly with a lot of energy and momentum Tipping over buildings and so on, causing a lot of shakings yes So, without earthquake, we'll never found all the stuff right Earthquakes are really important because they've allowed us to define the plate geometries.
They've allowed us to define the boundaries So, what about volcanoes Before volcanoes laid off, a lot of times there is a pre-eruptions seismic activities Shaking, yes And the magma access to the surface and causes stress and stresses released.
Do you see ever a plate tectonic right here Yes, we are looking at the sea cliffs These were the depositive.
This settlement was deposited about 500 meters blow the sea level.
And they've been uplifted.
So here, we are looking at the plate tectonic on its own backyard.
So far, we've explored the several great discoveries have revealed what's happening inside the earth.
The next discoveries opened our eyes to what's happening above.
With so much technology on our fingertips, it seems like predicting the weather should be more of an exact science.
But global weather patterns are so complex, so volatile Weather assumnevariables, it can change quickly.
Bring unexpected feral Enough energy to generate electricity for a major city for month Until our next great discovery.
A French meteorologist named Lyons Tessler de Boer conducted hundreds of unmanned balloon flights De Boer equipped each flight with a range of clock driven scientific instruments that continuously record the high altitude conditions.
There were thermometer, barometer and hygrometer to measure humidity.
From the information gathered by these instruments, De Boer was the first to discover that the atmosphere divided into layers.
Each characterized by distinctive meteorological conditions.
He named this layer the troposphere meaning sphere of change This is where clouds form and all our weather happens.
Above that, De Boer found the second layer, which he called the stratosphere meaning sphere of layers.
De Boer's discovery revolutionized our understanding of the atmosphere And help ushered the modern science of weather and climate studies.
Right now, there are 17 international satellites orbiting the earth, tracking the weather.
Why are these attentions to the weather Obviously a timely storm could save lives But it's also about the economy.
In united states alone, one third of the economy about two point seven trillion dollars depend on our now analysis what's happening with the weather.
And De Boer's hot air balloons helped to lead the way Just like our next great discovery.
They couldn't figure out what this radiation was coming from Until a physicist name Victor Hess made an important discovery.
Believing the radiation might be coming from the sky, Hess made a series of flight in the hot air balloon.
Collecting data with a variety instruments, including an electroscope which measures radioactive charge During one of the balloon flights, there was a total solar eclipse, when radiation level stayed the same, Hess knew that the radiation couldn't becoming from the sun, it had becoming form the cosmos.
With that insight, Victor has discovered cosmic radiation.
Electrically charged atomic particles, protons mostly.
Radiation form deep space, powerful enough to penetrate the earth's atmosphere And potentially dangerous too.
Capable of causing genetic mutations and cancer But the prize didn't shield him from the Nazis.
Hess's wife was Jewish And they were marked for entering the concentration camp Finally, a Gestapo officer warned them and they fled Austria before they could be arrested.
By 1946, they were American citizens.
And Hess treated his balloon flights for series of scientific tests atop the Empire State Building Instead of testing for cosmic rays, Hess now a professor in Ford university Went to the empire state building to measure another kind of radiation.
Working high above the New York sky land, Hess analyzed the radiation level in rain samples that collected at the of the top of the building.
Victor Hess was the first scientist test for radioactive follow-up from that blast in the United States.
The origin of cosmic rays is still not clear.
They probably come from supernova, exploding stars in deep space They may be left over the big bang, were the mass of all the stars that universe exploded at once.
Wherever it origin, we are fortunately that the magnetic field that surrounds our planet protects us From the most damaging effects of the radiation But is our next discovery reveals its magnetic field that is continually in flex, As we've already seen, the earth's magnetic fields access a shield, protecting our planet 's dangerous radiation.
from much of the sun But in 1906, a French geologist named Bernard Brundes made a startling discovery about the field.
Brundes was examining newly formed volcanic rocks near a lava flow in central France.
Lava from a volcano contains minerals from the deep earth.
Inside the molten lava, iron particles are freed to move But its flow began to cool and formed into rocks, the iron particles allied themselves according to the earth's magnetic field like a compass.
They become a fossilize snapshot of the earth's magnetic field in action.
But during his research, Brunhes found some of his research contained iron particles that were magnetized in the opposite direction.
Their compass niddle had flipped Pointing south instead of north.
This was the moment of discovery.
Brunhes realized that some point in the path It was a significant discovery.
It meant that the earth was a far more dynamic planet than many had imagined.
Constantly changing.
As every couple of thousands years or so.
And we may be going through a reversal right now.
Because the earth's magnetic field has decreased in shrinks about ten percent in only the last century and a half.
No one exactly sure what happens, but brunhes's discovery does raise a provocative question.
What happens when the earth's magnetic field goes to zero The answer may lie on mars Scientists had detected that the red planet once may had a magnetic field Powered by a furnace like a core, just like the one on earth.
But at some point in its past, the heat source of the mars core was extinguished.
Without its internal furnace, the planet died.
Its magnetic field disappeared and dangerous cosmic and solar rays bombarded the planet.
Wiping out any chances of life as we know it Could that happened here Well, the composition and size of the earth's core such that the earth will probably stay hot inside for billions of years.
But what happens when the earth's magnetic field reverses and goes to zero What will happen in the next thousands years or so there probably be humans' round scientists And they can measure cosmic rays and study their effects on living things.
Our next great discovery began with a puzzle.
Early in the nineteenth century, European scientists found that certain rock formations in low line areas Born striking resembles with rock normally found at much higher elevation further north.
How did they get there One idea put forth was that the rock has been moved by giant glaciers.
That once expanded out of the mountains then retreated to their present locations.
The theory of the ice age was born.
What could cased the ice age happened.
The question remained a mystery until around the First World War.
A Yugoslavia scientist named Milutin Milankovic developed a theory At the time, several mathematical models had been developed to explain subtle but significant variations in the earth's orbit around the sun The astronomers had calculated that the distance between the two and This effect was the sun's energy reaches the earth Using these and other measurements, Milankovic calculated with great mathematical precision How the orbital variations has caused major climate changes over the history of the earth.
The changes began when the subtle shift of the earth's orbit Produced cooler summers and colder winters.
This change created a domino effect.
That, year after year, century after century, Allowed the glaciers to expand and ice sheet to grow.
When the orbit of the earth eventually changed again, the ice retreated.
Milankovic had discovered a mechanism to explain the creation of the periodic ice ages.
Today, most of Milankovic's theories had been confirmed and accepted.
It's estimated that the earth may have experienced as many as 17 ice ages over the last several millions years.
With giant ice sheet covering as much as the third of the planet.
Our next great discovery has unfolded just a hundred years Which in geological terms makes it a catastrophic event.
More significant than the ice age and it's happening right now.
This is the national climatic data center in Asheville North Carolina.
Weather records from around the world were stored here.
But the weather of the last century that was particular interested to expert like Thomas Karl, director of the center.
The record indicate that over the past one hundred years, the surface temperature of the planet has increased about one degree Fahrenheit That may not sound like much.
But many believed that represents a significant warming trend in a relative short period of time The impacts of that warming are indeed substantial.
This is a major global problem Speculation about what causing the earth to heat up has long centered on the burning of fossil fuels.
While carbon dioxide and other gases occurred naturally in the earth's atmosphere.
Scientists wonder if a buildup of industrial CO2 could be responsible for the climate change.
Finally, American geochemist David Keeling set out to measure just how much carbon dioxide might be up there.
In 1958, keeling took air samples 2 miles above the earth.
High atop among the Mauna Loa Hawaii.
Location was chosen because the air was mostly unpolluted.
Keeling collected the samples in flask and measured the CO2 levels of infra-red gas analyzer The results were astonishing.
Keeling found that the level of the carbon dioxide of the atmosphere It was a landmark moment.
Suddenly, the bateoverconnection between global warming and rising CO2 levels became more than academic issue.
Here were measurable data.
Today, the level of CO2 in the atmosphere continues to rise.
It's now the level some 30 percent greater than what experts believed was prior to the industrial revolution.
An increasing that many scientists believed is having a significant impact on climate around the world.
One of the most visible examples of climate change from global warming is here.
At the south cascade glacier in Washington states where the ice is melting.
According to surveys, the south cascade glacier has retreated by one point two miles over the last century.
And glaciers are shrinking worldwide.
reported that the volume of the ice decreasing at a significant rate.
While there is a general consensus among scientists that the earth climate is becoming warmer There is still some debate over how much carbon dioxide is to blame Regardless of the debate, researchers are tracking global warming more than ever Computer models have been developed to anticipate what may happen if the current warming trend continues.
From wide-spread flooding to the devastation of ecosystem around the world.
That's sounds like a lot Mostly from burning fossil fuels.
To equal the amount of CO2 emission that we produce From the creation of the ice ages to the effects of global warming The earth's climate is roller coast of changes And our next great discovery helped put it all in perspectives For centuries, people believed that the earth was shaped by catastrophes, like the biblical flood and revolutionized geology.
Lyell spent years traveling the world, studying overwhelming number of rock formations and fossil samples He had a brilliant eye for detail and piece by piece, he began to see the rock told different story.
While catastrophe such as volcanoes, earthquakes and floods occasionally affected the planet The greatest changes were the result of the incredibly slow and natural geological process.
A process driven by wind, water, erosion and the heating and cooling of the earth.
A record of those changes was contained in the layers of rock.
But here was Lyell's most radical insight.
The mechanism for that slow process of geological change was time, lots of time.
The earth Lyell argued was far older than was generally accepted And he presented proof of his finding and the landmark book called principles of geology.
Today, the publication is considered the birth of the modern geology.
Samuel Bowring is a professor of geology at MIT.
I think a very important in Lyell's development of far was a trip to see the volcanoes of Italy Vesuvius And set belief particular where he actually saw that the mountain was built up of successive flows And they had some of these, and he has good ideas one they were erupted, because here is historical And he was able to use that to extrapolate that the volcano itself must be hundreds of thousands years old.
And at that time, talking about hundreds of thousands years was revolutionary.
Others argued for a directionality in evolution that the earth on day one is not the same earth as today.
Some secular change has occurred.
This is the debate geologists have today.
Today, many considered Charles Lyell to be the Charles Darwin in geology.
In real life, the connection between the two men was significant.
Darwin took the first edition copy of the volume one of Lyell's treaties on his cruise with the Beagle And what he realized from reading this as he was also simultaneously worrying about revolution was here, was the solution to revolution We have limitless time.
Lyell's discovery set off a fire storming interest in determining the true age of the earth.
Until then, most everyone believed the planet was young.
But the publications of Lyell's seminal book Geologists want to know how young.
Our next great discovery provided an answer Exactly how old was the earth When an American chemist Bertram Boltwood discovered a way to make the rocks and minerals of the earth, provided an answer.
Scientists already knew that rocks contained naturally occurring radioactive elements such as uranium They also knew that each element decayed into other elements according to its own rates or clocks and that rate almost never changed.
While studying these rates of decay, Boltwood found that mineral samples of uranium always contain traces of lead It was indicationly believed that lead was the last element remaining from uranium slow process of decay.
Form this observation, Boltwood put all together.
If he measured the amount of lead contained in the uranium sample.
And calculated it by the m which uranium decays, he could determine the approximate age of the rock It was a breakthrough discovery.
Suddenly, scientists had an extraordinary and accurate new tool for calibrating the geological history of the earth.
It was called radiometric dating.
The great thing about radiometric dating is it allows us to determine the age of the rocks in great canyon with quiet bit of precision.
So we can understand the whole history of deposition of this rock before the canyon was carved.
So, without geochronology we would never know that we are missing Now, other places in the world have that history.
Here, we don't have that history.
It's important to remember geological record is remarkably incomplete So century ago, geochronology, time in the earth, Which, of course, was a huge breakthrough.
In terms of understanding how old the earth was but was only half of two ages of the earth.
To appreciate how much time that is, consider this.
Not even a tick of a clock.
So why is this so important when we look at the history of revolution.
History of revolution is punctuated by incredible extinction events.
So, the question is, was this sort of a gradual process or we saw an increasing amount of extinction and finally the last herald or was that catastrophic.
Was life wonderful on the Permian earth And suddenly everything went extinct.
The way to answer that question is through high precision geochronology And the date of the accumulation right now suggest that was a extremely rapid event So as to say rapid event, one model that we have works for well impact of the asteroid.
And recently, there has been some evidence put forth suggests there may have been an asteroid at that boundary impact the earth, The other aspect of the extinctions is really important, some people even more exciting than understanding the extinction itself.
Is, what happens to the ecosystem.
How long did it take to recover When you wipe everything out is like resetting the whole evolutionary clock.
And then you allowed new things to fill the ecosystem that was completely bleadered It could be that if that extinction, we wouldn't see the rise of the dinosaurs and then mammals We could live on a very different planet.
We wouldn't live here.
You look at this view and if you can insignificant inspect, right And the grandeurs of this astonishing And when you think about, What you can learn from it in another whole level.
And it's like a book.
There is lots of information, waiting for us to extraculate, The information that we haven't even thought about.
Asking the record to produce for there's a lot to do.
That's job security for science.
Yes The earth as a complex and dynamic planet The Crust is shifting The mantle is moving The atmosphere is constantly in flex All the species that live on the earth are changing along with it.
Our ancestors did we wouldn't be here.
The earth is challenging all living things.
And so far, life has been apt to the challenge.
The most powerful force on the face of the planet.
Moving whole continents Creating mountains, exploding them apart.
And unimaginable winter of ice lasting a hundred thousand years.
Some of the greatest discovery in the history of science, have revealed what an incredibly complex and dynamic planet we live on.
Discoveries that opened our eyes, changing how we see the sky above and earth blow.
In March 1980, geologists detected a serious of small earthquakes here, beneath mountain St.
Helens in Washington State.
It was a signal that the long dormant volcano was waking up.
Finally on the morning of May eighteenth, it did.
Mountain St.
Helens had erupted with the force five hundred times the atomic bomb that was dropped on Hiroshima A cloud of hot ash roared fifteen miles into the atmosphere 230 square mile of forests were wiped out.
Six million trees, enough wood to build three hundred thousand two storey houses Throughout recorded history, civilization has lived with the threat of earthquakes and volcanoes But the cause of their destructed power remained elusive, shrouded in mystery.
It wasn't until our first great discovery that a picture of what was happening inside the earth began to emerge.
For centuries, most of what we knew the earth's interior came from mining operation like this one.
It wasn't until scientists began using seismograph to study earthquakes.
That they gained more accurate understanding of the insight of the earth.
When an earthquake occurred, seismograph measured the speed and intensity of the seismic waves that vibrated underground.
Using this method, scientists identified different layers inside the earth.
Each one characterized by changes and rock density.
For example, the first layer was the crust, a skin of rock covering the planet.
As for what was blow that A breakthrough discovery provided the first clue.
In 1906, British geologist Richard Altman was analyzing seismographic reading caused by a large earthquake.
When he saw something odd.
As the vibration from earthquake reverberated, they didn't arrive at the center of the earth as expected.
It was as if they hit an obstacle.
Altman realized the obstacle must be the inner most part of the earth.
A dense mass hard enough to reflected seismic waves from going all the way through.
Altman had discovered the earth's core.
It was a landmark discovery because it set the stage for the work of another scientist Who is about to help revolutionized our understanding of what was happening inside the earth.
With Altman's discovery, many believed that picture of the earth's core was complete.
But in the early 1930, Inge Lehmann wasn't so sure.
Lehmann was a Danish seismologist, who worked extensively in Denmark and Greenland.
Studding the velocity seismic waves from earthquakes In 1936, she was analyzing the seismic waves from an earthquake that had occurred several years earlier.
Seismological stations around the world had made recording of the same quake.
By comparing their readings, Lehmann calculated that the seismic waves had passed through the earth's core.
There was a change in their velocity.
As if they had encountered another boundary of some kind.
Then it occurred to her.
Something was missing from accepted structure of the earth's interior.
The core that Lehman had found was the earth's inner core.
Today, through precise seismic measurements, we know that it is made of solid iron.
Solid because gravity at center of the earth created a pressure The core that Richard Altman had discovered turned out to be the earth's outer core.
It's made of liquid iron and other elements.
A hot churning mass that generates electric currents, which in turn created the magnet field that, protects the earth from dangerous cosmic radiation.
Slightly larger than the planet mars.
I caught up with Doc.
Catherin Johnson, a professor of geophysics doing field research at a mine location in southern California.
What made the earth hotter at the first place The earth's original heat actually came from how the earth formed.
It formed through collisions of small bodies we call then planetesimals The collisions of these bodies released huge amounts of heat.
That came from astronomical distance.
It's right, just crashing to each other.
And turning all that kinetic energy into heat.
So, the heat is still here Yeah, and the heat is still here and there is also the heat with released actually during the formation of the earth's cores.
So all these bodies came together They are rocky.
They have bit of metals in them.
That metals settled within the earth to from.
Gravity.
Gravity, yes, just by gravity.
But the change in this gravitational energy going from near the surface of the earth to falling to the center, actually also released a lot of heat.
Why wasn't the earth cool off It hasn't cooled off because it actually cools very slowly.
That's seems perhaps surprising given hot But its original temperature was very very hot.
So it takes the earth's massive, so it takes a long time for it to cool.
It's why small planets like mars Even small like planetesimal bodies like moon have pretty much cooled off.
But here on earth, the cooling off the planet is perhaps billions of years away.
Thanks to the intense heat of the core, which acts as a kind of natural furnace.
What Altman and Lehmann didn't know was what else was this furnace was capable of.
And that's our next great discovery.
A meteorologist named Alfred Wegener was browsing through some books when something caught his eye.
A list of Atlantic plants and animal fossils that had been found on opposite sides of the Atlantic Ocean.
Wegener was intrigued.
How could the same species have gotten from one part of the world to another He examined the eastern coast of South America and the western coast of Africa.
And was struck out the shape of the two coastlines might fit together.
The more he looked the more links he found.
Species of land mammals and east Africa also inhabited in the island of Madagascar How did that happenDid the animals evolve at both places at once quiet please Or did they somehow cross from one land to the other, swimming hundreds of miles across the Indian Ocean.
And then Wegener saw all clearly He realized that all the continents in the world had once formed A giant single landmass that he called Pangaea from the Greek pangea meaning all earth.
It was in Pangaea that the plants and animals found on opposite sides of world had once shared the same home.
Then, over hundreds of millions of years, Pangaea had split apart And its jigsaw pieces had drifted to their present locations Wegener called his theory continental drift.
Wegener wasn't the first scientist to speculate that the earth had once been dominated by a super continent.
But he was the first to pore together all the evidence and make a strong case for it.
Unfortunately, his peers weren't very accept it.
There was no mechanism to explain how the continents might plow through the oceans Continental drift was just too incredible to believe.
As a result, his discovery was largely ignored.
Quiet down or get out of here.
World war two, German U-boat ran the proud To track them, the allied forced developed new sonar methods.
And scientists were enlisted to help survey the ocean floor.
When the United States entered the war, Harry Hess was a geology professor in Princeton University.
But he also happened to be a navy reservers.
So it wasn't long before he found himself command a tank transport ship in the pacific.
To help maneuver when coming in for a beach landing, Hass' ship was equipped with a depth sounder.
Still being a geologist at heart.
He used the sounder to measure the depth of the ocean floor whenever the ship was out to sea.
And what he discovered startled him Until the second would war, most scientists imagined the bottom of ocean look like this Flat wide with nothing but settlement.
Harry Hass discovered something else entirely.
Mountains, like these here in California with deep canyons and tranches Hundreds of high peeks that we now believe are once active volcanoes And all of these, at bottom of Pacific Ocean, surprisingly though, The discovery of the pacific mountain range was not made Harry Hass part of our great one hundred.
We will get to that in a minute.
To understand where all this headed.
Like to skip a height to another event that set the geology world buzzing For years, oceanographers surveyed the Atlantic Ocean.
And taken sonar readings that indicating there was something down there, something big.
They called it the Mid-Atlantic Ridge The reason it's so great To fills in, a paved a visit to Neal Driscoll.
A geologist at the Scripps institution of oceanography.
One of the big discoveries that was made was that there was this ridge of underwater volcanoes that stood high above the sea floor.
How high is the mountain in the mid-Atlantic The average sea floor depth around the order of about 4000-5000meters, mid-ocean ridge seize up about 2500 meters So, they about two half kilometers on average higher than the surrounding see floor that charly here in blue colors.
- So, that's over a mile high.
- Yes.
And that's where Harry Hass comes back into the story.
Analyzing course samples in sonar reading around mid-Atlantic ridge, Hass made an astonishing discovery.
A phenomena almost beyond comprehension.
The age of the Atlantic Ocean floor he determined was progressively older, the further moved away from the ridge Harry Hass has discovered that the sea floor was spreading.
He concluded that molten rock was being forced up from inside the earth.
And the ridge were then formed into new crust on the ocean floor.
Gradually was pushed away on either side as more molten rock continued pushing up from behind it.
Hass called his great discovery sea floor spreading.
Harry Hass was in a position that he could bring it altogether Things were spreading apart.
New earth was being generated But if you did this for long enough, the earth should grow And it doesn't.
Erath doesn't get any bigger.
No.
Harry appreciated the fact that if new earth was being generated in one area, There have to be consumed or recycled in another area The process that recycle the crust of the spreading ocean floor back inside the earth is called subduction.
But is our next great discovery revealed Is all part of a much larger process Perhaps most powerful forces on the face of the earth.
Hass's discovery that the sea floor was spreading Rescued Alfred Wegener's idea of Pangaea from obscurity.
Now there was the geological mechanism to explain continental drift.
That's simple.
Once you hear it, it does sound great.
By the nineteen sixties, both ideas were synthesized into a single theory, the science of plate tectonics A great discovery that revealed just how complex and dynamic our planet it is.
Several groups of scientists had concluded that not only is the earth's crust moving, but the surface of the planet is broken into large interconnected plates These plates are constantly in motion floating on the layer of molten rock in the earth's mantle.
This seems fantastic; I mean this seems just too crazy.
How could the whole world be sliding around.
I can see where people were suspecting.
Yes.
But it's the rates like your fingernail grow.
Not very fast.
I don't feel a thing.
That's right.
Accumulately, it's huge.
That here the thing is Geological time scales, it's what makes it so important because if you think of it over a year, you moved a few centimeters.
And think of millions of years, that you moving kilometers.
And they moving apart and they'll come back together.
Why they come back together Because the Pacific Ocean right now had subduction all around it.
And the plates is actually being consumed and recycled With the Atlantic ocean is spreading without much subduction.
So the Atlantic Ocean is kind of grow, the Pacific Ocean is kind of close And then will start getting closer, Asian and closing up the Pacific Ocean.
It's crazy.
.
It's pretty good One you hear it, it's hard to imagine geologist.
not believing it.
yes So once the theory and mechanism that was important contribution.
We can't believe it until yes So the plates are spreading.
They are not plowing , The understanding of the plate tectonics has given scientists new insights into the changing face of our planet.
A dynamic example of some of those changes can be seen here on the California coastline.
Where two of the earth's largest plates, the pacific and the North America, collide.
There are numbers of results.
But one we get volcanoes with the plates that subducted back into the earth.
These volcanoes happened because the plates get subducted, releases water And the water lowers the molten temperature of the overriding plates and Make it easier.
And we get volcanism, So that's really get to know Whitney, Mount Shasta, Mount.
Things like these, absolutely.
So the Andes are perfect example of this type of volcanoes.
Other places that you get the mid-ocean ridges, you get pieced of sea floor that were one to two kilometers higher than the surrounding sea floor.
These are underwater volcano chains that stretch the link of these ocean basins Other places you get large strike-slip fault So what's the strike-slip fault The strike-slip is when the plates move by one and another, and they don't do it without kinks and twists.
So, when the kinks and twists are, there can be places that lock And then they release and then they release quickly with a lot of energy and momentum Tipping over buildings and so on, causing a lot of shakings yes So, without earthquake, we'll never found all the stuff right Earthquakes are really important because they've allowed us to define the plate geometries.
They've allowed us to define the boundaries So, what about volcanoes Before volcanoes laid off, a lot of times there is a pre-eruptions seismic activities Shaking, yes And the magma access to the surface and causes stress and stresses released.
Do you see ever a plate tectonic right here Yes, we are looking at the sea cliffs These were the depositive.
This settlement was deposited about 500 meters blow the sea level.
And they've been uplifted.
So here, we are looking at the plate tectonic on its own backyard.
So far, we've explored the several great discoveries have revealed what's happening inside the earth.
The next discoveries opened our eyes to what's happening above.
With so much technology on our fingertips, it seems like predicting the weather should be more of an exact science.
But global weather patterns are so complex, so volatile Weather assumnevariables, it can change quickly.
Bring unexpected feral Enough energy to generate electricity for a major city for month Until our next great discovery.
A French meteorologist named Lyons Tessler de Boer conducted hundreds of unmanned balloon flights De Boer equipped each flight with a range of clock driven scientific instruments that continuously record the high altitude conditions.
There were thermometer, barometer and hygrometer to measure humidity.
From the information gathered by these instruments, De Boer was the first to discover that the atmosphere divided into layers.
Each characterized by distinctive meteorological conditions.
He named this layer the troposphere meaning sphere of change This is where clouds form and all our weather happens.
Above that, De Boer found the second layer, which he called the stratosphere meaning sphere of layers.
De Boer's discovery revolutionized our understanding of the atmosphere And help ushered the modern science of weather and climate studies.
Right now, there are 17 international satellites orbiting the earth, tracking the weather.
Why are these attentions to the weather Obviously a timely storm could save lives But it's also about the economy.
In united states alone, one third of the economy about two point seven trillion dollars depend on our now analysis what's happening with the weather.
And De Boer's hot air balloons helped to lead the way Just like our next great discovery.
They couldn't figure out what this radiation was coming from Until a physicist name Victor Hess made an important discovery.
Believing the radiation might be coming from the sky, Hess made a series of flight in the hot air balloon.
Collecting data with a variety instruments, including an electroscope which measures radioactive charge During one of the balloon flights, there was a total solar eclipse, when radiation level stayed the same, Hess knew that the radiation couldn't becoming from the sun, it had becoming form the cosmos.
With that insight, Victor has discovered cosmic radiation.
Electrically charged atomic particles, protons mostly.
Radiation form deep space, powerful enough to penetrate the earth's atmosphere And potentially dangerous too.
Capable of causing genetic mutations and cancer But the prize didn't shield him from the Nazis.
Hess's wife was Jewish And they were marked for entering the concentration camp Finally, a Gestapo officer warned them and they fled Austria before they could be arrested.
By 1946, they were American citizens.
And Hess treated his balloon flights for series of scientific tests atop the Empire State Building Instead of testing for cosmic rays, Hess now a professor in Ford university Went to the empire state building to measure another kind of radiation.
Working high above the New York sky land, Hess analyzed the radiation level in rain samples that collected at the of the top of the building.
Victor Hess was the first scientist test for radioactive follow-up from that blast in the United States.
The origin of cosmic rays is still not clear.
They probably come from supernova, exploding stars in deep space They may be left over the big bang, were the mass of all the stars that universe exploded at once.
Wherever it origin, we are fortunately that the magnetic field that surrounds our planet protects us From the most damaging effects of the radiation But is our next discovery reveals its magnetic field that is continually in flex, As we've already seen, the earth's magnetic fields access a shield, protecting our planet 's dangerous radiation.
from much of the sun But in 1906, a French geologist named Bernard Brundes made a startling discovery about the field.
Brundes was examining newly formed volcanic rocks near a lava flow in central France.
Lava from a volcano contains minerals from the deep earth.
Inside the molten lava, iron particles are freed to move But its flow began to cool and formed into rocks, the iron particles allied themselves according to the earth's magnetic field like a compass.
They become a fossilize snapshot of the earth's magnetic field in action.
But during his research, Brunhes found some of his research contained iron particles that were magnetized in the opposite direction.
Their compass niddle had flipped Pointing south instead of north.
This was the moment of discovery.
Brunhes realized that some point in the path It was a significant discovery.
It meant that the earth was a far more dynamic planet than many had imagined.
Constantly changing.
As every couple of thousands years or so.
And we may be going through a reversal right now.
Because the earth's magnetic field has decreased in shrinks about ten percent in only the last century and a half.
No one exactly sure what happens, but brunhes's discovery does raise a provocative question.
What happens when the earth's magnetic field goes to zero The answer may lie on mars Scientists had detected that the red planet once may had a magnetic field Powered by a furnace like a core, just like the one on earth.
But at some point in its past, the heat source of the mars core was extinguished.
Without its internal furnace, the planet died.
Its magnetic field disappeared and dangerous cosmic and solar rays bombarded the planet.
Wiping out any chances of life as we know it Could that happened here Well, the composition and size of the earth's core such that the earth will probably stay hot inside for billions of years.
But what happens when the earth's magnetic field reverses and goes to zero What will happen in the next thousands years or so there probably be humans' round scientists And they can measure cosmic rays and study their effects on living things.
Our next great discovery began with a puzzle.
Early in the nineteenth century, European scientists found that certain rock formations in low line areas Born striking resembles with rock normally found at much higher elevation further north.
How did they get there One idea put forth was that the rock has been moved by giant glaciers.
That once expanded out of the mountains then retreated to their present locations.
The theory of the ice age was born.
What could cased the ice age happened.
The question remained a mystery until around the First World War.
A Yugoslavia scientist named Milutin Milankovic developed a theory At the time, several mathematical models had been developed to explain subtle but significant variations in the earth's orbit around the sun The astronomers had calculated that the distance between the two and This effect was the sun's energy reaches the earth Using these and other measurements, Milankovic calculated with great mathematical precision How the orbital variations has caused major climate changes over the history of the earth.
The changes began when the subtle shift of the earth's orbit Produced cooler summers and colder winters.
This change created a domino effect.
That, year after year, century after century, Allowed the glaciers to expand and ice sheet to grow.
When the orbit of the earth eventually changed again, the ice retreated.
Milankovic had discovered a mechanism to explain the creation of the periodic ice ages.
Today, most of Milankovic's theories had been confirmed and accepted.
It's estimated that the earth may have experienced as many as 17 ice ages over the last several millions years.
With giant ice sheet covering as much as the third of the planet.
Our next great discovery has unfolded just a hundred years Which in geological terms makes it a catastrophic event.
More significant than the ice age and it's happening right now.
This is the national climatic data center in Asheville North Carolina.
Weather records from around the world were stored here.
But the weather of the last century that was particular interested to expert like Thomas Karl, director of the center.
The record indicate that over the past one hundred years, the surface temperature of the planet has increased about one degree Fahrenheit That may not sound like much.
But many believed that represents a significant warming trend in a relative short period of time The impacts of that warming are indeed substantial.
This is a major global problem Speculation about what causing the earth to heat up has long centered on the burning of fossil fuels.
While carbon dioxide and other gases occurred naturally in the earth's atmosphere.
Scientists wonder if a buildup of industrial CO2 could be responsible for the climate change.
Finally, American geochemist David Keeling set out to measure just how much carbon dioxide might be up there.
In 1958, keeling took air samples 2 miles above the earth.
High atop among the Mauna Loa Hawaii.
Location was chosen because the air was mostly unpolluted.
Keeling collected the samples in flask and measured the CO2 levels of infra-red gas analyzer The results were astonishing.
Keeling found that the level of the carbon dioxide of the atmosphere It was a landmark moment.
Suddenly, the bateoverconnection between global warming and rising CO2 levels became more than academic issue.
Here were measurable data.
Today, the level of CO2 in the atmosphere continues to rise.
It's now the level some 30 percent greater than what experts believed was prior to the industrial revolution.
An increasing that many scientists believed is having a significant impact on climate around the world.
One of the most visible examples of climate change from global warming is here.
At the south cascade glacier in Washington states where the ice is melting.
According to surveys, the south cascade glacier has retreated by one point two miles over the last century.
And glaciers are shrinking worldwide.
reported that the volume of the ice decreasing at a significant rate.
While there is a general consensus among scientists that the earth climate is becoming warmer There is still some debate over how much carbon dioxide is to blame Regardless of the debate, researchers are tracking global warming more than ever Computer models have been developed to anticipate what may happen if the current warming trend continues.
From wide-spread flooding to the devastation of ecosystem around the world.
That's sounds like a lot Mostly from burning fossil fuels.
To equal the amount of CO2 emission that we produce From the creation of the ice ages to the effects of global warming The earth's climate is roller coast of changes And our next great discovery helped put it all in perspectives For centuries, people believed that the earth was shaped by catastrophes, like the biblical flood and revolutionized geology.
Lyell spent years traveling the world, studying overwhelming number of rock formations and fossil samples He had a brilliant eye for detail and piece by piece, he began to see the rock told different story.
While catastrophe such as volcanoes, earthquakes and floods occasionally affected the planet The greatest changes were the result of the incredibly slow and natural geological process.
A process driven by wind, water, erosion and the heating and cooling of the earth.
A record of those changes was contained in the layers of rock.
But here was Lyell's most radical insight.
The mechanism for that slow process of geological change was time, lots of time.
The earth Lyell argued was far older than was generally accepted And he presented proof of his finding and the landmark book called principles of geology.
Today, the publication is considered the birth of the modern geology.
Samuel Bowring is a professor of geology at MIT.
I think a very important in Lyell's development of far was a trip to see the volcanoes of Italy Vesuvius And set belief particular where he actually saw that the mountain was built up of successive flows And they had some of these, and he has good ideas one they were erupted, because here is historical And he was able to use that to extrapolate that the volcano itself must be hundreds of thousands years old.
And at that time, talking about hundreds of thousands years was revolutionary.
Others argued for a directionality in evolution that the earth on day one is not the same earth as today.
Some secular change has occurred.
This is the debate geologists have today.
Today, many considered Charles Lyell to be the Charles Darwin in geology.
In real life, the connection between the two men was significant.
Darwin took the first edition copy of the volume one of Lyell's treaties on his cruise with the Beagle And what he realized from reading this as he was also simultaneously worrying about revolution was here, was the solution to revolution We have limitless time.
Lyell's discovery set off a fire storming interest in determining the true age of the earth.
Until then, most everyone believed the planet was young.
But the publications of Lyell's seminal book Geologists want to know how young.
Our next great discovery provided an answer Exactly how old was the earth When an American chemist Bertram Boltwood discovered a way to make the rocks and minerals of the earth, provided an answer.
Scientists already knew that rocks contained naturally occurring radioactive elements such as uranium They also knew that each element decayed into other elements according to its own rates or clocks and that rate almost never changed.
While studying these rates of decay, Boltwood found that mineral samples of uranium always contain traces of lead It was indicationly believed that lead was the last element remaining from uranium slow process of decay.
Form this observation, Boltwood put all together.
If he measured the amount of lead contained in the uranium sample.
And calculated it by the m which uranium decays, he could determine the approximate age of the rock It was a breakthrough discovery.
Suddenly, scientists had an extraordinary and accurate new tool for calibrating the geological history of the earth.
It was called radiometric dating.
The great thing about radiometric dating is it allows us to determine the age of the rocks in great canyon with quiet bit of precision.
So we can understand the whole history of deposition of this rock before the canyon was carved.
So, without geochronology we would never know that we are missing Now, other places in the world have that history.
Here, we don't have that history.
It's important to remember geological record is remarkably incomplete So century ago, geochronology, time in the earth, Which, of course, was a huge breakthrough.
In terms of understanding how old the earth was but was only half of two ages of the earth.
To appreciate how much time that is, consider this.
Not even a tick of a clock.
So why is this so important when we look at the history of revolution.
History of revolution is punctuated by incredible extinction events.
So, the question is, was this sort of a gradual process or we saw an increasing amount of extinction and finally the last herald or was that catastrophic.
Was life wonderful on the Permian earth And suddenly everything went extinct.
The way to answer that question is through high precision geochronology And the date of the accumulation right now suggest that was a extremely rapid event So as to say rapid event, one model that we have works for well impact of the asteroid.
And recently, there has been some evidence put forth suggests there may have been an asteroid at that boundary impact the earth, The other aspect of the extinctions is really important, some people even more exciting than understanding the extinction itself.
Is, what happens to the ecosystem.
How long did it take to recover When you wipe everything out is like resetting the whole evolutionary clock.
And then you allowed new things to fill the ecosystem that was completely bleadered It could be that if that extinction, we wouldn't see the rise of the dinosaurs and then mammals We could live on a very different planet.
We wouldn't live here.
You look at this view and if you can insignificant inspect, right And the grandeurs of this astonishing And when you think about, What you can learn from it in another whole level.
And it's like a book.
There is lots of information, waiting for us to extraculate, The information that we haven't even thought about.
Asking the record to produce for there's a lot to do.
That's job security for science.
Yes The earth as a complex and dynamic planet The Crust is shifting The mantle is moving The atmosphere is constantly in flex All the species that live on the earth are changing along with it.
Our ancestors did we wouldn't be here.
The earth is challenging all living things.
And so far, life has been apt to the challenge.