Earth: The Inside Story

male narrator: EARTH...

THE ONLY PLANET ORBITING THE SUN

THAT HAS CONTINENTS,

OCEANS,

PLATE TECTONICS,

AND THE SOLE PLANET WITH AN ATMOSPHERE

THAT HAS SUSTAINED LIFE FOR BILLIONS OF YEARS.

HOW DID EARTH GET THIS WAY?

WHAT'S BEHIND THE POWER, THE VIOLENCE

THAT CRACKS SOLID ROCK IN AN INSTANT,

THAT SHATTERS BUILDINGS

AND SENDS TSUNAMIS RACING FOR THE SHORE,

THAT ERUPTS SEAS OF LAVA AND BILLOWING CLOUDS OF ASH?

EARTH HAS BEEN MAKING HEADLINES LATELY.

- POWERFUL IMAGES OF DESTRUCTION NEVER SEEN IN OUR LIFETIME.

narrator: PEOPLE ARE ASKING,

"HAS EARTH ENTERED A PERIOD OF INTENSE GEOLOGIC UPHEAVAL?"

SCIENTISTS HAVE NEW ANSWERS TO QUESTIONS ABOUT OUR HOME,

THE THIRD PLANET FROM THE SUN.

IT'S A STORY THAT, JUST A FEW DECADES AGO,

COULD NOT HAVE BEEN TOLD.

ABOUT 10 BILLION YEARS

AFTER THE BIG BANG CREATED THE UNIVERSE,

OUR SOLAR SYSTEM BEGAN TO FORM.

SCIENTISTS CALCULATE THAT THIS HAPPENED

4.567 BILLION YEARS AGO,

AND THAT WAS WHEN PLANET EARTH WAS CREATED.

- A LONG TIME AGO, ABOUT 4 1/2 BILLION YEARS AGO,

THE EARTH FORMED FROM THIS NEBULA AROUND THE SUN.

THE SUN IN THE CENTER, AND THE NEBULA SWIRLING AROUND,

AND THE BITS OF THE NEBULA ACCRETING,

THAT IS, STICKING TOGETHER AND COLLIDING WITH EACH OTHER,

AND IT WAS A VERY TURBULENT TIME.

AND THE EARTH GRADUALLY CAME TOGETHER,

AND AS IT BECAME MORE MASSIVE,

THE GRAVITATIONAL FORCE BECAME LARGER,

AND IT COULD ATTRACT MORE OF THE SMALL PIECES,

AND THE EARTH GREW AND GREW.

narrator: IT TOOK ABOUT 100 MILLION YEARS

FOR EARTH TO REACH ITS PRESENT SIZE,

BUT BEFORE IT DID,

OUR PLANET EXPERIENCED ITS LARGEST, MOST DRAMATIC EVENT.

- SO AFTER THE EARLY EARTH FORMED,

PROBABLY TENS OF MILLIONS OF YEARS AFTERWARDS,

YOU HAD A MARS-SIZED OBJECT THAT ACTUALLY HIT THE EARTH.

narrator: THE GIANT PLANETOID IMPACTOR WAS CALLED THEIA.

- THE MARS-SIZED IMPACTOR HIT THE EARTH,

AND IT SPEWED OFF A LOT OF THE MATERIAL FROM THE EARTH,

AND PART OF THAT FORMED THE SMALL--

THE MOON THAT WE NOW HAVE.

AND ALSO WE GENERATED A LOT OF HEAT FROM THIS IMPACT,

AND SO IT MIGHT HAVE REMELTED A LOT OF THE EARLY EARTH.

narrator: SCIENTISTS ONLY RECENTLY LEARNED

OF THIS MASSIVE IMPACT

BY STUDYING ROCKS COLLECTED ON THE MOON.

IT TURNED OUT THAT THE MOON ROCKS WERE VERY SIMILAR

IN COMPOSITION TO EARTH ROCKS.

AFTER THE IMPACT, THE MOON BECAME A SATELLITE,

WHILE THE EARTH WAS LEFT A MOLTEN BALL OF FIRE.

- AND SO THE EARLY EARTH WAS, LIKE, THIS MOLTEN MASS.

THAT MUST HAVE LOOKED LIKED MAYBE ONE GIANT VOLCANO

OR LAVA LAKE.

IT SLOWLY SOLIDIFIED AND FORMED THIS OUTER CRUST

THAT IS WHERE WE STAND TODAY.

narrator: AS THE CRUST FORMED,

COLLISIONS AND BOMBARDMENTS DIED DOWN,

BUT THE METEORITES CONTINUE TO FALL TO THIS DAY.

- WE START WITH SOME BREAKING NEWS THIS HOUR.

PEOPLE IN THE URALS IN RUSSIA

HAVE SEEN BURNING OBJECTS RAINING DOWN FROM THE SKY

AFTER A METEORITE EXPLODED ABOVE THE EARTH,

CAUSING A METEOR SHOWER.

EYEWITNESSES REPORTED SEVERAL BLASTS.

narrator: DESPITE THE SHOCK THAT A METEOR SHOWER CAN CAUSE,

METEORITES ARE EXTREMELY VALUABLE TO SCIENTISTS

WHO STUDY WHEN THE EARTH WAS CREATED.

THEY ARE COLLECTED AND STUDIED WORLDWIDE.

BUT THE BEST PLACE TO FIND THESE ROCKY ALIENS

IS ONE OF THE EARTH'S

ANTARCTICA.

ON THE SLEEK, BLUE ICE EXPANSE

OF THE CENTRAL ANTARCTIC ICE SHEET,

THE SURFACE IS SWEPT CLEAN BY RELENTLESS WINDS.

A METEORITE SITS EXPOSED FOR AN AVERAGE OF 20,000 YEARS,

SOMETIMES FOR SEVERAL MILLION YEARS,

BEFORE SCIENTISTS MIGHT SPOT IT AND COLLECT IT.

A TYPE OF METEORITE CALLED A CHONDRITE

CONTAINS THE SAME BASIC ELEMENTS

THAT MAKE UP THE SUN AND PLANETS,

SO THEY TELL US A GREAT DEAL

ABOUT WHERE WE ORIGINALLY CAME FROM

AND WHEN.

TO FIGURE OUT HOW OLD METEORITES AND THE EARTH

ACTUALLY ARE,

SCIENTISTS USE HIGH-PRECISION INSTRUMENTS

TO MEASURE THEIR RADIOACTIVE PROPERTIES.

BUT WHY MUST SCIENTISTS RELY ON METEORITES

TO FIGURE OUT HOW OLD THE EARTH REALLY IS?

WHY DON'T THEY SIMPLY STUDY THE OLDEST ROCKS

THAT WERE FORMED ON THE EARTH ITSELF?

- FROM THE EARTH'S FORMATION AROUND 4.6 BILLION YEARS AGO

UP TO ABOUT 3.8 BILLION YEARS AGO,

IS AN ERA CALLED THE HADEAN,

WHEN THE EARTH WAS UNDERGOING HEAVY BOMBARDMENT,

AND THERE'S VIRTUALLY NO ROCK RECORD

FROM THAT PERIOD OF TIME AT ALL ON THE EARTH REMAINING TODAY.

narrator: THE HADEAN ERA,

GREEK FOR UNDERWORLD, OR HELL.

NOTHING SURVIVED THIS INFERNO...

OR DID IT?

IT WAS A MISSING LINK HUNDREDS OF MILLIONS OF YEARS LONG

BETWEEN EARTH'S CREATION AND ITS OLDEST ROCKS,

LIKE THESE 3.6 BILLION-YEAR-OLD ROCKS FOUND IN AUSTRALIA.

BEAUTIFUL.

narrator: BUT BREAKTHROUGHS IN ANALYZING THESE ROCKS

FINALLY OPENED A WINDOW INTO THE HADEAN.

- INTERESTINGLY, WE DO HAVE SOME MATERIALS FROM THAT TIME.

THEY ARE SMALL ZIRCON GRAINS, 4.4 BILLION OR SO OF AGE.

narrator: ZIRCONS ARE THE OLDEST TERRESTRIAL MATERIAL

EVER FOUND ON EARTH.

BUT ROCKS CONTAINING ZIRCONS THAT ARE BILLIONS OF YEARS OLD

HAVE ONLY BEEN DISCOVERED IN A HANDFUL OF PLACES ON EARTH,

LIKE ANTARCTICA.

THE REST HAVE BEEN OBLITERATED.

STUDYING THOSE RARE VESTIGES OF THE EARLY DAYS OF EARTH,

SCIENTISTS WERE ASTONISHED TO FIND EVIDENCE

THAT VERY EARLY ON, EARTH DEVELOPED A CHARACTERISTIC

THAT IT AND NO OTHER PLANET IN THE SOLAR SYSTEM POSSESSES:

PLATE TECTONICS.

- PLATE TECTONICS HAS BEEN AROUND ON EARTH

FROM THE EARLY DAYS,

AT LEAST 2 1/2, 3 BILLION YEARS AGO.

SO MORE THAN 3/4 OF THE LIFE OF THE PLANET.

narrator: MARS NEARLY DEVELOPED PLATE TECTONICS,

BUT FAILED.

MARS IS SMALLER THAN EARTH.

IT COOLED FASTER.

IT MAY WELL HAVE HAD A STYLE OF PLATE TECTONICS

EARLY IN ITS HISTORY, BUT IT CLEARLY DOES NOT TODAY.

narrator: VENUS, CONSIDERED EARTH'S SISTER PLANET,

IS ALSO MISSING EARTH'S TRAIT OF PLATE TECTONICS.

- VENUS DOESN'T HAVE PLATE TECTONICS

IN THE STYLE THAT WE RECOGNIZE

WITH VERY CLEAR, LINEAR BOUNDARIES BETWEEN RIGID PLATES,

PERHAPS BECAUSE THERE'S NO WATER ON THE SURFACE OF VENUS.

narrator:

IT IS THE STRIKING AND DISTINGUISHING CHARACTERISTIC

OF EARTH'S SURFACE,

AND SCIENTISTS ARE FINDING THAT THIS SUBSTANCE IS THE KEY

THAT STARTED EARTH'S EARLY CRUST

INTO CONSTANT, EVER-CHANGING MOTION.

- ONE OF THE REASONS WE HAVE PLATE TECTONICS,

WHICH WE DON'T SEE ON ANY OTHER PLANETS,

IS THAT WE HAVE A LOT OF WATER ON THE EARTH.

SO WE HAVE WATER NOT ONLY IN THE OCEANS,

BUT THERE'S APPROXIMATELY AN OCEAN'S WORTH OF WATER

LOCKED UP IN THE ROCKS IN, SAY, THE UPPER 100 KILOMETERS

OF THE EARTH.

WHEN YOU PUT WATER INTO A ROCK,

IT MAKES THE ROCK WEAKER BY MAYBE A FACTOR OF 100

THAN IT WOULD BE WITHOUT THE WATER.

WEAKER ROCKS MAKE FOR PLATE TECTONICS

BECAUSE YOU HAVE TO HAVE PLATE BOUNDARIES

WHERE ROCKS EITHER SLIDE BY EACH OTHER,

OR ONE GOES DOWN UNDERNEATH THE OTHER.

AND SO UNLESS YOU HAVE ROCKS THAT ARE WEAK ENOUGH

TO BE ABLE TO SLIDE PAST EACH OTHER,

YOU'RE NOT GONNA HAVE PLATE TECTONICS.

narrator: BUT WHERE DID EARTH'S VAST AMOUNT

OF LIQUID WATER COME FROM?

- IN THE EARLY HISTORY OF THE EARTH,

WHEN THERE WAS A LOT OF VOLCANISM GOING ON,

VOLCANOES ACTUALLY BROUGHT GASES UP

THAT CREATED THE EARLY ATMOSPHERE.

AND MAGMA HAS WATER IN THE FORM OF VAPOR

THAT IT CAN BRING UP.

narrator: ICY METEORITES AND COMETS

WERE THE OTHER LIKELY SOURCE

THAT INFUSED EARTH'S CRUST WITH WATER

AND GOT IT MOVING.

AND ONCE PLATE TECTONICS STARTED,

IT NEVER STOPPED.

IT HAS INFLUENCED EVERYTHING THAT HAS HAPPENED ON THE SURFACE

INCLUDING LIFE.

- THE OXYGEN, THE MINERALS, EVERYTHING THAT WE GET

COMES FROM THE INTERIOR OF THE EARTH.

WE ALL HAVE INTERNALLY WITHIN US

A WHOLE SUITE OF MINERALS AND THINGS THAT--

WE'RE FROM THE EARTH.

ESSENTIALLY, THAT'S WHERE WE--

OUR CHEMICAL MAKEUP IS FROM THE EARTH.

AND IF YOU HAD NO WAY OF GETTING THAT OUTSIDE OF THE EARTH,

THEN ESSENTIALLY YOU'D HAVE A DEAD PLANET.

narrator: PLATE TECTONICS BECAME RECOGNIZED

AS BEING A CRUCIAL INGREDIENT FOR LIFE,

AS IS WATER.

THIS WAS AN IMPORTANT PIECE OF KNOWLEDGE

FOR SCIENTISTS WHO WERE STUDYING EARTH'S ANCIENT ROCKS.

IF THE CONDITIONS FOR LIFE WERE PRESENT

WHEN EARTH'S ANCIENT ROCKS FORMED BILLIONS OF YEARS AGO,