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male narrator:
EARTH...
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THE ONLY PLANET ORBITING THE SUN
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00:00:08,676 --> 00:00:10,676
THAT HAS CONTINENTS,
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OCEANS,
5
00:00:12,480 --> 00:00:14,046
PLATE TECTONICS,
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00:00:14,115 --> 00:00:16,582
AND THE SOLE PLANET
WITH AN ATMOSPHERE
7
00:00:16,650 --> 00:00:20,953
THAT HAS SUSTAINED LIFE
FOR BILLIONS OF YEARS.
8
00:00:21,022 --> 00:00:23,288
HOW DID EARTH GET THIS WAY?
9
00:00:23,357 --> 00:00:26,558
WHAT'S BEHIND THE POWER,
THE VIOLENCE
10
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THAT CRACKS SOLID ROCK
IN AN INSTANT,
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00:00:29,397 --> 00:00:31,830
THAT SHATTERS BUILDINGS
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00:00:31,899 --> 00:00:34,900
AND SENDS TSUNAMIS
RACING FOR THE SHORE,
13
00:00:34,969 --> 00:00:40,005
THAT ERUPTS SEAS OF LAVA
AND BILLOWING CLOUDS OF ASH?
14
00:00:42,710 --> 00:00:45,044
EARTH HAS BEEN
MAKING HEADLINES LATELY.
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- POWERFUL IMAGES OF DESTRUCTION
NEVER SEEN IN OUR LIFETIME.
16
00:00:48,682 --> 00:00:50,382
narrator:
PEOPLE ARE ASKING,
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00:00:50,451 --> 00:00:55,821
"HAS EARTH ENTERED A PERIOD
OF INTENSE GEOLOGIC UPHEAVAL?"
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SCIENTISTS HAVE NEW ANSWERS
TO QUESTIONS ABOUT OUR HOME,
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THE THIRD PLANET FROM THE SUN.
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IT'S A STORY THAT,
JUST A FEW DECADES AGO,
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00:01:05,599 --> 00:01:07,966
COULD NOT HAVE BEEN TOLD.
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ABOUT 10 BILLION YEARS
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00:01:19,146 --> 00:01:21,847
AFTER THE BIG BANG
CREATED THE UNIVERSE,
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00:01:21,916 --> 00:01:26,151
OUR SOLAR SYSTEM BEGAN TO FORM.
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SCIENTISTS CALCULATE
THAT THIS HAPPENED
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4.567 BILLION YEARS AGO,
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AND THAT WAS WHEN PLANET EARTH
WAS CREATED.
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- A LONG TIME AGO,
ABOUT 4 1/2 BILLION YEARS AGO,
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THE EARTH FORMED
FROM THIS NEBULA AROUND THE SUN.
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THE SUN IN THE CENTER,
AND THE NEBULA SWIRLING AROUND,
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AND THE BITS
OF THE NEBULA ACCRETING,
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THAT IS, STICKING TOGETHER
AND COLLIDING WITH EACH OTHER,
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AND IT WAS
A VERY TURBULENT TIME.
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[explosion]
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AND THE EARTH
GRADUALLY CAME TOGETHER,
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00:02:08,028 --> 00:02:10,095
AND AS IT BECAME MORE MASSIVE,
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00:02:10,164 --> 00:02:12,965
THE GRAVITATIONAL FORCE
BECAME LARGER,
38
00:02:13,033 --> 00:02:16,568
AND IT COULD ATTRACT
MORE OF THE SMALL PIECES,
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AND THE EARTH GREW AND GREW.
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narrator:
IT TOOK ABOUT 100 MILLION YEARS
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FOR EARTH TO REACH
ITS PRESENT SIZE,
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BUT BEFORE IT DID,
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OUR PLANET EXPERIENCED ITS
LARGEST, MOST DRAMATIC EVENT.
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- SO AFTER
THE EARLY EARTH FORMED,
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PROBABLY TENS OF MILLIONS
OF YEARS AFTERWARDS,
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YOU HAD A MARS-SIZED OBJECT
THAT ACTUALLY HIT THE EARTH.
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[explosion]
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narrator: THE GIANT PLANETOID
IMPACTOR WAS CALLED THEIA.
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- THE MARS-SIZED IMPACTOR
HIT THE EARTH,
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AND IT SPEWED OFF A LOT
OF THE MATERIAL FROM THE EARTH,
51
00:02:58,379 --> 00:03:00,012
AND PART OF THAT
FORMED THE SMALL--
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THE MOON THAT WE NOW HAVE.
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00:03:01,949 --> 00:03:04,483
AND ALSO WE GENERATED A LOT
OF HEAT FROM THIS IMPACT,
54
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AND SO IT MIGHT HAVE REMELTED
A LOT OF THE EARLY EARTH.
55
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narrator:
SCIENTISTS ONLY RECENTLY LEARNED
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OF THIS MASSIVE IMPACT
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BY STUDYING ROCKS
COLLECTED ON THE MOON.
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00:03:17,631 --> 00:03:20,132
IT TURNED OUT THAT
THE MOON ROCKS WERE VERY SIMILAR
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IN COMPOSITION TO EARTH ROCKS.
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AFTER THE IMPACT,
THE MOON BECAME A SATELLITE,
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00:03:27,208 --> 00:03:30,742
WHILE THE EARTH WAS LEFT
A MOLTEN BALL OF FIRE.
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00:03:32,413 --> 00:03:35,948
- AND SO THE EARLY EARTH
WAS, LIKE, THIS MOLTEN MASS.
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00:03:36,016 --> 00:03:40,586
THAT MUST HAVE LOOKED
LIKED MAYBE ONE GIANT VOLCANO
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OR LAVA LAKE.
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IT SLOWLY SOLIDIFIED
AND FORMED THIS OUTER CRUST
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00:03:47,795 --> 00:03:50,596
THAT IS WHERE WE STAND TODAY.
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narrator:
AS THE CRUST FORMED,
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COLLISIONS AND BOMBARDMENTS
DIED DOWN,
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BUT THE METEORITES
CONTINUE TO FALL TO THIS DAY.
70
00:04:00,574 --> 00:04:02,741
- WE START WITH SOME
BREAKING NEWS THIS HOUR.
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PEOPLE IN THE URALS IN RUSSIA
72
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HAVE SEEN BURNING OBJECTS
RAINING DOWN FROM THE SKY
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AFTER A METEORITE EXPLODED
ABOVE THE EARTH,
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CAUSING A METEOR SHOWER.
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EYEWITNESSES REPORTED
SEVERAL BLASTS.
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00:04:15,055 --> 00:04:17,823
[glass shattering]
77
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narrator: DESPITE THE SHOCK
THAT A METEOR SHOWER CAN CAUSE,
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METEORITES ARE
EXTREMELY VALUABLE TO SCIENTISTS
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WHO STUDY WHEN THE EARTH
WAS CREATED.
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00:04:28,535 --> 00:04:32,170
THEY ARE COLLECTED
AND STUDIED WORLDWIDE.
81
00:04:32,239 --> 00:04:34,673
BUT THE BEST PLACE
TO FIND THESE ROCKY ALIENS
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IS ONE OF THE EARTH'S
MOST UNEARTHLY PLACES:
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ANTARCTICA.
84
00:04:43,617 --> 00:04:45,450
ON THE SLEEK, BLUE ICE EXPANSE
85
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OF THE CENTRAL ANTARCTIC
ICE SHEET,
86
00:04:48,088 --> 00:04:52,324
THE SURFACE IS SWEPT CLEAN
BY RELENTLESS WINDS.
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00:04:52,393 --> 00:04:56,695
A METEORITE SITS EXPOSED
FOR AN AVERAGE OF 20,000 YEARS,
88
00:04:56,764 --> 00:04:59,364
SOMETIMES
FOR SEVERAL MILLION YEARS,
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00:04:59,433 --> 00:05:03,135
BEFORE SCIENTISTS MIGHT SPOT IT
AND COLLECT IT.
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00:05:05,005 --> 00:05:07,306
A TYPE OF METEORITE
CALLED A CHONDRITE
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CONTAINS THE SAME BASIC ELEMENTS
92
00:05:09,443 --> 00:05:12,144
THAT MAKE UP THE SUN
AND PLANETS,
93
00:05:12,212 --> 00:05:14,212
SO THEY TELL US A GREAT DEAL
94
00:05:14,281 --> 00:05:16,848
ABOUT WHERE
WE ORIGINALLY CAME FROM
95
00:05:16,917 --> 00:05:20,085
AND WHEN.
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TO FIGURE OUT HOW OLD
METEORITES AND THE EARTH
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ACTUALLY ARE,
98
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SCIENTISTS USE
HIGH-PRECISION INSTRUMENTS
99
00:05:27,594 --> 00:05:30,562
TO MEASURE
THEIR RADIOACTIVE PROPERTIES.
100
00:05:30,631 --> 00:05:33,799
BUT WHY MUST SCIENTISTS
RELY ON METEORITES
101
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TO FIGURE OUT HOW OLD
THE EARTH REALLY IS?
102
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WHY DON'T THEY SIMPLY STUDY
THE OLDEST ROCKS
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THAT WERE FORMED
ON THE EARTH ITSELF?
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- FROM THE EARTH'S FORMATION
AROUND 4.6 BILLION YEARS AGO
105
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UP TO ABOUT
3.8 BILLION YEARS AGO,
106
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IS AN ERA CALLED THE HADEAN,
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WHEN THE EARTH WAS UNDERGOING
HEAVY BOMBARDMENT,
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00:05:55,823 --> 00:05:58,023
AND THERE'S
VIRTUALLY NO ROCK RECORD
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FROM THAT PERIOD OF TIME AT ALL
ON THE EARTH REMAINING TODAY.
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narrator:
THE HADEAN ERA,
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GREEK FOR UNDERWORLD,
OR HELL.
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NOTHING SURVIVED THIS INFERNO...
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OR DID IT?
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IT WAS A MISSING LINK HUNDREDS
OF MILLIONS OF YEARS LONG
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00:06:19,413 --> 00:06:22,514
BETWEEN EARTH'S CREATION
AND ITS OLDEST ROCKS,
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LIKE THESE 3.6 BILLION-YEAR-OLD
ROCKS FOUND IN AUSTRALIA.
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- BEAUTIFUL.
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00:06:29,990 --> 00:06:32,257
narrator: BUT BREAKTHROUGHS
IN ANALYZING THESE ROCKS
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FINALLY OPENED A WINDOW
INTO THE HADEAN.
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00:06:37,431 --> 00:06:41,733
- INTERESTINGLY, WE DO HAVE
SOME MATERIALS FROM THAT TIME.
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THEY ARE SMALL ZIRCON GRAINS,
4.4 BILLION OR SO OF AGE.
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00:06:49,510 --> 00:06:51,643
narrator: ZIRCONS ARE
THE OLDEST TERRESTRIAL MATERIAL
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EVER FOUND ON EARTH.
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00:06:54,948 --> 00:06:58,950
BUT ROCKS CONTAINING ZIRCONS
THAT ARE BILLIONS OF YEARS OLD
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HAVE ONLY BEEN DISCOVERED
IN A HANDFUL OF PLACES ON EARTH,
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LIKE ANTARCTICA.
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00:07:04,458 --> 00:07:08,827
THE REST HAVE BEEN OBLITERATED.
128
00:07:08,896 --> 00:07:12,731
STUDYING THOSE RARE VESTIGES
OF THE EARLY DAYS OF EARTH,
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SCIENTISTS WERE ASTONISHED
TO FIND EVIDENCE
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00:07:15,602 --> 00:07:18,970
THAT VERY EARLY ON,
EARTH DEVELOPED A CHARACTERISTIC
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THAT IT AND NO OTHER PLANET
IN THE SOLAR SYSTEM POSSESSES:
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PLATE TECTONICS.
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00:07:28,382 --> 00:07:30,282
- PLATE TECTONICS
HAS BEEN AROUND ON EARTH
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00:07:30,350 --> 00:07:31,917
FROM THE EARLY DAYS,
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00:07:31,985 --> 00:07:35,187
AT LEAST 2 1/2,
3 BILLION YEARS AGO.
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00:07:35,255 --> 00:07:37,989
SO MORE THAN 3/4 OF THE LIFE
OF THE PLANET.
137
00:07:38,058 --> 00:07:42,060
narrator: MARS NEARLY DEVELOPED
PLATE TECTONICS,
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BUT FAILED.
139
00:07:44,164 --> 00:07:45,430
- MARS IS SMALLER THAN EARTH.
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IT COOLED FASTER.
141
00:07:46,967 --> 00:07:49,067
IT MAY WELL HAVE HAD A STYLE
OF PLATE TECTONICS
142
00:07:49,136 --> 00:07:54,005
EARLY IN ITS HISTORY,
BUT IT CLEARLY DOES NOT TODAY.
143
00:07:54,074 --> 00:07:56,908
narrator: VENUS, CONSIDERED
EARTH'S SISTER PLANET,
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00:07:56,977 --> 00:08:01,012
IS ALSO MISSING EARTH'S TRAIT
OF PLATE TECTONICS.
145
00:08:01,081 --> 00:08:03,982
- VENUS DOESN'T HAVE
PLATE TECTONICS
146
00:08:04,051 --> 00:08:05,917
IN THE STYLE THAT WE RECOGNIZE
147
00:08:05,986 --> 00:08:08,987
WITH VERY CLEAR, LINEAR
BOUNDARIES BETWEEN RIGID PLATES,
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00:08:09,056 --> 00:08:12,824
PERHAPS BECAUSE THERE'S NO WATER
ON THE SURFACE OF VENUS.
149
00:08:18,699 --> 00:08:20,298
narrator:
LIQUID WATER:
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00:08:20,367 --> 00:08:23,468
IT IS THE STRIKING AND
DISTINGUISHING CHARACTERISTIC
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00:08:23,537 --> 00:08:26,404
OF EARTH'S SURFACE,
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00:08:26,473 --> 00:08:30,008
AND SCIENTISTS ARE FINDING
THAT THIS SUBSTANCE IS THE KEY
153
00:08:30,077 --> 00:08:32,210
THAT STARTED EARTH'S EARLY CRUST
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00:08:32,279 --> 00:08:35,447
INTO CONSTANT,
EVER-CHANGING MOTION.
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00:08:37,117 --> 00:08:39,784
- ONE OF THE REASONS
WE HAVE PLATE TECTONICS,
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00:08:39,853 --> 00:08:41,419
WHICH WE DON'T SEE
ON ANY OTHER PLANETS,
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00:08:41,488 --> 00:08:44,523
IS THAT WE HAVE
A LOT OF WATER ON THE EARTH.
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SO WE HAVE WATER
NOT ONLY IN THE OCEANS,
159
00:08:47,294 --> 00:08:49,728
BUT THERE'S APPROXIMATELY
AN OCEAN'S WORTH OF WATER
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00:08:49,796 --> 00:08:52,964
LOCKED UP IN THE ROCKS IN, SAY,
THE UPPER 100 KILOMETERS
161
00:08:53,033 --> 00:08:53,865
OF THE EARTH.
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00:08:56,003 --> 00:08:57,969
WHEN YOU PUT WATER INTO A ROCK,
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00:08:58,038 --> 00:09:00,939
IT MAKES THE ROCK WEAKER
BY MAYBE A FACTOR OF 100
164
00:09:01,008 --> 00:09:05,343
THAN IT WOULD BE
WITHOUT THE WATER.
165
00:09:05,412 --> 00:09:07,312
WEAKER ROCKS
MAKE FOR PLATE TECTONICS
166
00:09:07,381 --> 00:09:09,848
BECAUSE YOU HAVE TO HAVE
PLATE BOUNDARIES
167
00:09:09,917 --> 00:09:11,983
WHERE ROCKS EITHER SLIDE
BY EACH OTHER,
168
00:09:12,052 --> 00:09:15,620
OR ONE GOES DOWN
UNDERNEATH THE OTHER.
169
00:09:15,689 --> 00:09:17,756
AND SO UNLESS YOU HAVE ROCKS
THAT ARE WEAK ENOUGH
170
00:09:17,824 --> 00:09:20,158
TO BE ABLE TO SLIDE
PAST EACH OTHER,
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00:09:20,227 --> 00:09:21,927
YOU'RE NOT GONNA HAVE
PLATE TECTONICS.
172
00:09:28,001 --> 00:09:30,101
narrator: BUT WHERE
DID EARTH'S VAST AMOUNT
173
00:09:30,170 --> 00:09:33,572
OF LIQUID WATER COME FROM?
174
00:09:33,640 --> 00:09:36,675
- IN THE EARLY HISTORY
OF THE EARTH,
175
00:09:36,743 --> 00:09:39,511
WHEN THERE WAS A LOT
OF VOLCANISM GOING ON,
176
00:09:39,580 --> 00:09:43,582
VOLCANOES ACTUALLY
BROUGHT GASES UP
177
00:09:43,650 --> 00:09:46,985
THAT CREATED
THE EARLY ATMOSPHERE.
178
00:09:47,054 --> 00:09:52,023
AND MAGMA HAS WATER
IN THE FORM OF VAPOR
179
00:09:52,092 --> 00:09:53,792
THAT IT CAN BRING UP.
180
00:09:53,860 --> 00:09:56,695
[rumbling]
181
00:09:59,533 --> 00:10:01,299
narrator:
ICY METEORITES AND COMETS
182
00:10:01,368 --> 00:10:03,201
WERE THE OTHER LIKELY SOURCE
183
00:10:03,270 --> 00:10:05,704
THAT INFUSED EARTH'S CRUST
WITH WATER
184
00:10:05,772 --> 00:10:08,873
AND GOT IT MOVING.
185
00:10:08,942 --> 00:10:11,276
AND ONCE PLATE TECTONICS
STARTED,
186
00:10:11,345 --> 00:10:13,278
IT NEVER STOPPED.
187
00:10:13,347 --> 00:10:16,881
IT HAS INFLUENCED EVERYTHING
THAT HAS HAPPENED ON THE SURFACE
188
00:10:16,950 --> 00:10:18,216
INCLUDING LIFE.
189
00:10:22,255 --> 00:10:25,290
- THE OXYGEN, THE MINERALS,
EVERYTHING THAT WE GET
190
00:10:25,359 --> 00:10:27,158
COMES FROM THE INTERIOR
OF THE EARTH.
191
00:10:29,896 --> 00:10:32,464
WE ALL HAVE INTERNALLY WITHIN US
192
00:10:32,532 --> 00:10:35,200
A WHOLE SUITE OF MINERALS
AND THINGS THAT--
193
00:10:35,268 --> 00:10:36,501
WE'RE FROM THE EARTH.
194
00:10:36,570 --> 00:10:40,739
ESSENTIALLY, THAT'S WHERE WE--
195
00:10:40,807 --> 00:10:42,307
OUR CHEMICAL MAKEUP
IS FROM THE EARTH.
196
00:10:44,978 --> 00:10:48,813
AND IF YOU HAD NO WAY OF GETTING
THAT OUTSIDE OF THE EARTH,
197
00:10:48,882 --> 00:10:51,282
THEN ESSENTIALLY YOU'D HAVE
A DEAD PLANET.
198
00:10:55,188 --> 00:10:57,288
narrator: PLATE TECTONICS
BECAME RECOGNIZED
199
00:10:57,357 --> 00:10:59,624
AS BEING A CRUCIAL INGREDIENT
FOR LIFE,
200
00:10:59,693 --> 00:11:02,994
AS IS WATER.
201
00:11:03,063 --> 00:11:04,696
THIS WAS AN IMPORTANT PIECE
OF KNOWLEDGE
202
00:11:04,765 --> 00:11:09,634
FOR SCIENTISTS WHO WERE STUDYING
EARTH'S ANCIENT ROCKS.
203
00:11:09,703 --> 00:11:12,303
IF THE CONDITIONS FOR LIFE
WERE PRESENT
204
00:11:12,372 --> 00:11:16,875
WHEN EARTH'S ANCIENT ROCKS
FORMED BILLIONS OF YEARS AGO,
205
00:11:16,943 --> 00:11:19,844
THEN WASN'T IT POSSIBLE
THAT LIFE ALSO TOOK HOLD
206
00:11:19,913 --> 00:11:24,215
IN THE EARLY DAWN
OF EARTH'S FORMATION?
207
00:11:24,284 --> 00:11:26,117
THE SEARCH WAS ON.
208
00:11:28,722 --> 00:11:33,458
SOME SCIENTISTS ZEROED IN ON
THE 3.5 BILLION-YEAR-OLD ROCKS
209
00:11:33,527 --> 00:11:36,928
IN THE OUTBACK
OF WESTERN AUSTRALIA.
210
00:11:36,997 --> 00:11:41,366
- AMAZINGLY, IT TURNS OUT
THAT FAIRLY SOON AFTER,
211
00:11:41,435 --> 00:11:44,502
PEOPLE STARTED DISCOVERING
SOME POTENTIAL SIGNS OF LIFE
212
00:11:44,571 --> 00:11:45,870
IN THOSE ROCKS,
213
00:11:45,939 --> 00:11:48,406
AND ONE OF THE MAJOR DISCOVERIES
214
00:11:48,475 --> 00:11:49,974
WAS STRUCTURES
CALLED STROMATOLITES.
215
00:11:54,281 --> 00:11:56,915
narrator: STROMATOLITES
ARE PECULIAR ROCKY STRUCTURES
216
00:11:56,983 --> 00:11:59,284
BUILT BY COLONIES
OF CYANOBACTERIA,
217
00:11:59,352 --> 00:12:02,554
OR BLUE-GREEN ALGAE.
218
00:12:02,622 --> 00:12:05,023
THEY ARE EXTREMELY RARE
ON EARTH TODAY,
219
00:12:05,092 --> 00:12:07,258
GROWING IN ONLY A FEW PLACES,
220
00:12:07,327 --> 00:12:11,162
LIKE LAGUNA BACALAR IN MEXICO.
221
00:12:11,231 --> 00:12:14,733
BUT THEY WERE THE FIRST
LIFE FORMS TO APPEAR ON EARTH,
222
00:12:14,801 --> 00:12:17,702
AND THEY GAVE RISE
TO ALL OTHER FORMS OF LIFE,
223
00:12:17,771 --> 00:12:20,105
INCLUDING PEOPLE.
224
00:12:20,173 --> 00:12:22,941
IT TOOK AWHILE, THOUGH.
225
00:12:23,009 --> 00:12:25,210
- STROMATOLITES DOMINATE
THE FIRST 3 BILLION YEARS
226
00:12:25,278 --> 00:12:27,112
OF THE HISTORY OF LIFE ON EARTH.
227
00:12:27,180 --> 00:12:30,348
SO FROM 3 1/2 BILLION YEARS AGO
228
00:12:30,417 --> 00:12:31,850
TO UP TO ABOUT
1/2 A BILLION YEARS AGO,
229
00:12:31,918 --> 00:12:34,319
THE FOSSIL RECORD CONSISTS
230
00:12:34,387 --> 00:12:36,321
ALMOST ENTIRELY
OF STROMATOLITES.
231
00:12:40,060 --> 00:12:43,661
narrator: STROMATOLITES LIVED
IN OCEANS AND LAKES.
232
00:12:43,730 --> 00:12:46,598
FOR THAT PERIOD,
NO FOSSILS HAVE BEEN FOUND
233
00:12:46,666 --> 00:12:48,900
OF CREATURES THAT LIVED ON LAND.
234
00:12:48,969 --> 00:12:51,803
DOES THAT MEAN
THERE WERE NO CONTINENTS
235
00:12:51,872 --> 00:12:55,907
FOR THE FIRST 3 BILLION YEARS
OF EARTH'S HISTORY?
236
00:12:55,976 --> 00:12:57,375
ONCE AGAIN,
237
00:12:57,444 --> 00:13:02,247
EARTH'S ANCIENT ROCKS
YIELDED CLUES TO THIS MYSTERY.
238
00:13:02,315 --> 00:13:04,415
- WE DON'T KNOW FOR SURE
WHEN PLATE TECTONICS STARTED,
239
00:13:04,484 --> 00:13:09,587
BUT WE DO KNOW FOR SURE
WHEN WE FIRST HAD CONTINENTS.
240
00:13:09,656 --> 00:13:12,624
WE HAVE INTACT AREAS
THAT WE CAN GO AND MAP IN
241
00:13:12,692 --> 00:13:15,593
THAT GO BACK AS FAR
AS 4 BILLION YEARS.
242
00:13:15,662 --> 00:13:19,063
THAT'S NEARLY 90%
OF THE AGE OF THE EARTH,
243
00:13:19,132 --> 00:13:21,466
SO WE'RE QUITE SURE
ABOUT THE FACT
244
00:13:21,535 --> 00:13:23,468
THAT WE HAD CONTINENTS
BACK THAT FAR.
245
00:13:26,940 --> 00:13:28,940
narrator: NO ONE KNOWS
WHAT THE CONTINENTS WERE LIKE
246
00:13:29,009 --> 00:13:31,442
4 BILLION YEARS AGO
247
00:13:31,511 --> 00:13:33,545
OR WHY WE ENDED UP
WITH SEVEN CONTINENTS
248
00:13:33,613 --> 00:13:36,915
THAT RIDE AROUND
ON A DOZEN LARGE CRUSTAL PLATES
249
00:13:36,983 --> 00:13:40,752
AND MANY MICROPLATES IN BETWEEN.
250
00:13:40,821 --> 00:13:46,658
BUT THE QUESTION THAT PLAGUED
SCIENTISTS FOR YEARS WAS THIS:
251
00:13:46,726 --> 00:13:50,228
WHAT WAS THE PRIME FORCE
THAT MADE THE PLATES MOVE?
252
00:13:55,135 --> 00:13:57,936
THERE WERE
TWO CONTENDING FORCES.
253
00:13:58,004 --> 00:14:02,106
THE FIRST WAS DISCOVERED ABOARD
SEAFARING RESEARCH VESSELS
254
00:14:02,175 --> 00:14:06,444
MAPPING THE SEA FLOOR
DECADES AGO.
255
00:14:06,513 --> 00:14:08,413
SCIENTISTS LEARNED
THAT THE SEA FLOOR
256
00:14:08,481 --> 00:14:11,349
WAS SPREADING APART
IN THE MIDDLE OF THE OCEANS
257
00:14:11,418 --> 00:14:15,587
AT SUBMARINE MOUNTAIN RANGES
CALLED MID-OCEAN RIDGES.
258
00:14:15,655 --> 00:14:17,922
SUBMERSIBLES WERE SENT DOWN
259
00:14:17,991 --> 00:14:20,758
AND CAME BACK WITH FOOTAGE
OF HOT GASES WELLING UP
260
00:14:20,827 --> 00:14:23,795
IN THE RIFT ZONES.
261
00:14:23,864 --> 00:14:26,130
MAGMA WAS RISING
FROM BELOW HERE,
262
00:14:26,199 --> 00:14:28,132
AND IT WAS BELIEVED
THAT IT WAS PUSHING
263
00:14:28,201 --> 00:14:32,270
THE OCEANIC PLATES APART.
264
00:14:32,339 --> 00:14:36,808
THE KEY TO PLATE TECTONICS
WAS AT LAST DISCOVERED...
265
00:14:36,877 --> 00:14:40,278
OR WAS IT?
266
00:14:40,347 --> 00:14:44,015
SEISMIC EXPERIMENTS
OF EARTH'S DEEP CRUST AND MANTLE
267
00:14:44,084 --> 00:14:46,818
CHANGED SCIENTISTS' THINKING.
268
00:14:46,887 --> 00:14:49,587
A SECOND FORCE WAS DISCOVERED
269
00:14:49,656 --> 00:14:51,923
WHERE PLATES
COLLIDED HEAD-ON,
270
00:14:51,992 --> 00:14:55,627
AS THEY DO UNDER
THE ANDES MOUNTAINS OF ECUADOR.
271
00:14:55,695 --> 00:14:59,631
ONE PLATE WAS IMAGED DIVING
UNDERNEATH THE OTHER.
272
00:14:59,699 --> 00:15:03,234
THE WAS CALLED
A SUBDUCTION ZONE.
273
00:15:03,303 --> 00:15:05,904
THE SINKING SLAB
APPEARED TO BE PULLING
274
00:15:05,972 --> 00:15:07,872
THE REST OF THE PLATE BEHIND IT,
275
00:15:07,941 --> 00:15:11,309
MAKING THE ENTIRE PLATE MOVE.
276
00:15:11,378 --> 00:15:14,946
A GREAT DEBATE AROSE OVER
WHICH FORCE WAS MORE IMPORTANT
277
00:15:15,015 --> 00:15:17,916
IN DRIVING PLATE TECTONICS:
278
00:15:17,984 --> 00:15:23,821
PUSHING FROM THE RISING MAGMA
OR PULLING IN SUBDUCTION ZONES.
279
00:15:23,890 --> 00:15:27,825
THERE NOW APPEARS
TO BE A WINNER.
280
00:15:27,894 --> 00:15:31,162
- WHEN PEOPLE FIRST RECOGNIZED
MID-OCEAN RIDGE SPREADING
281
00:15:31,231 --> 00:15:33,765
AS THE KEY TO UNDERSTANDING
PLATE TECTONICS,
282
00:15:33,833 --> 00:15:38,202
THE VIEW WAS THAT THE MAGMA,
THE MANTLE,
283
00:15:38,271 --> 00:15:42,273
ROSE UP IN THE CENTER
AND FORCED THE PLATES APART.
284
00:15:42,342 --> 00:15:44,642
BUT THAT VIEW
HAS CHANGED OVER THE YEARS
285
00:15:44,711 --> 00:15:48,346
AND HAS LARGELY BEEN REPLACED
BY THE VIEW THAT IT'S THE PULL
286
00:15:48,415 --> 00:15:51,215
OF THE SUBDUCTION SLAB
THAT MATTERS MOST.
287
00:15:51,284 --> 00:15:54,852
- BOB, CAN YOU PLEASE HAND ME
THE PVC PIPE, PLEASE?
288
00:15:54,921 --> 00:15:57,255
- SURE.
289
00:15:57,324 --> 00:16:00,091
narrator: SO SCIENTISTS
LOOKED HARDER AT SUBDUCTION,
290
00:16:00,160 --> 00:16:06,164
AND AS THEY DID, MORE GEOLOGIC
WONDERS WERE UNCOVERED.
291
00:16:06,232 --> 00:16:10,001
FOR ONE, SEISMIC STUDIES
OF SUBDUCTION ZONES
292
00:16:10,070 --> 00:16:12,570
REVEALED THAT OCEANIC PLATES
ARE VERY THIN
293
00:16:12,639 --> 00:16:15,239
COMPARED TO CONTINENTS.
294
00:16:15,308 --> 00:16:18,810
THE SEA FLOOR
IS 3 TO 6 MILES THICK,
295
00:16:18,878 --> 00:16:21,713
WHILE CONTINENTS AVERAGE
30 MILES THICK
296
00:16:21,781 --> 00:16:26,517
AND SWELL UP TO 50 MILES
UNDER GREAT MOUNTAIN BELTS.
297
00:16:26,586 --> 00:16:28,586
THIS HAS A MAJOR INFLUENCE
298
00:16:28,655 --> 00:16:31,155
ON HOW THE PLATES
AFFECT EACH OTHER,
299
00:16:31,224 --> 00:16:34,292
ESPECIALLY IN SUBDUCTION ZONES.
300
00:16:34,361 --> 00:16:37,295
WHERE SUBDUCTING PLATES
MEET CONTINENTS,
301
00:16:37,364 --> 00:16:40,131
EARTH'S TALLEST MOUNTAINS
ARE BUILT:
302
00:16:40,200 --> 00:16:43,267
THE HIMALAYA OF ASIA,
303
00:16:43,336 --> 00:16:45,636
THE ALPS OF EUROPE,
304
00:16:45,705 --> 00:16:48,339
THE ANDES OF SOUTH AMERICA.
305
00:16:48,408 --> 00:16:51,009
SUBDUCTION CREATED THEM ALL.
306
00:16:53,146 --> 00:16:57,915
BUT SUBDUCTION CAN CREATE HAVOC
ON THE SURFACE.
307
00:16:57,984 --> 00:17:00,985
AS SEISMIC NETWORKS
IMPROVED AROUND THE WORLD,
308
00:17:01,054 --> 00:17:03,955
IT BECAME APPARENT
THAT SUBDUCTION WAS THE CULPRIT
309
00:17:04,024 --> 00:17:07,258
BEHIND EARTH'S
MOST POWERFUL EARTHQUAKES.
310
00:17:09,729 --> 00:17:13,331
- FIRST THE EARTHQUAKE ITSELF...
311
00:17:13,400 --> 00:17:15,233
[people screaming]
312
00:17:15,301 --> 00:17:18,669
A GROCERY STORE IN THE CAPITAL
AT THE MOMENT OF IMPACT.
313
00:17:18,738 --> 00:17:21,205
narrator:
THE TOHOKU EARTHQUAKE OF 2011
314
00:17:21,274 --> 00:17:23,775
WAS THE MOST POWERFUL
EVER KNOWN IN JAPAN
315
00:17:23,843 --> 00:17:27,412
AT MAGNITUDE 9.
316
00:17:27,480 --> 00:17:29,781
IT STRUCK
WHERE THE OCEANIC PACIFIC PLATE
317
00:17:29,849 --> 00:17:33,484
SUBDUCTS UNDER A PIECE
OF THE NORTH AMERICAN PLATE.
318
00:17:35,922 --> 00:17:37,955
- WHERE SUBDUCTION IS OCCURRING,
319
00:17:38,024 --> 00:17:42,894
YOU SEE A VERY WELL-DEFINED ZONE
OF EARTHQUAKES,
320
00:17:42,962 --> 00:17:46,764
ESSENTIALLY BETWEEN
THE DOWNGOING OCEANIC CRUST
321
00:17:46,833 --> 00:17:51,069
AND THE CONTINENTAL CRUST,
322
00:17:51,137 --> 00:17:53,371
AND IT FORMS A LINE
OF EARTHQUAKES
323
00:17:53,440 --> 00:17:56,941
WHERE THESE TWO CRUSTS
ARE IN CONTACT WITH EACH OTHER
324
00:17:57,010 --> 00:18:01,846
AND SLIPPING PAST EACH OTHER.
325
00:18:01,915 --> 00:18:05,149
[siren wailing]
326
00:18:05,218 --> 00:18:07,051
narrator: SUBDUCTION QUAKES
CAN ALSO GENERATE
327
00:18:07,120 --> 00:18:08,886
DEVASTATING TSUNAMIS
328
00:18:08,955 --> 00:18:11,422
BECAUSE OF THEIR PROXIMITY
TO COASTLINES.
329
00:18:11,491 --> 00:18:13,724
- ONE OF THE WORST
EARTHQUAKES EVER...
330
00:18:13,793 --> 00:18:17,395
- THE JAPANESE QUAKE AND
THE 2004 INDIAN OCEAN EARTHQUAKE
331
00:18:17,464 --> 00:18:20,431
OFF SUMATRA
ARE STRIKING EXAMPLES.
332
00:18:28,308 --> 00:18:31,042
EARTHQUAKES AND TSUNAMIS
ARE NOT THE ONLY ACTION
333
00:18:31,111 --> 00:18:33,778
SPAWNED BY SUBDUCTION.
334
00:18:33,847 --> 00:18:36,547
SUBDUCTION
ALSO CREATES VOLCANOES,
335
00:18:36,616 --> 00:18:41,319
AND THEY, TOO,
CAN BE LARGE AND DANGEROUS.
336
00:18:41,387 --> 00:18:45,123
- VOLCANOES IN THE SUBDUCTION
ZONES ARE FORMED
337
00:18:45,191 --> 00:18:50,828
BY MAGMAS THAT ARE MORE SILICIC,
OR MORE VISCOUS,
338
00:18:50,897 --> 00:18:54,599
AND THEY ARE
MUCH MORE EXPLOSIVE.
339
00:18:54,667 --> 00:18:58,069
SO THOSE ARE THE VOLCANOES
THAT CAN REALLY BE DANGEROUS
340
00:18:58,138 --> 00:19:00,138
AND REALLY CREATE TROUBLE.
341
00:19:04,611 --> 00:19:08,813
narrator: SUBDUCTION VOLCANOES
ARE EARTH'S MOST NOTORIOUS:
342
00:19:08,882 --> 00:19:12,416
MOUNT TUNGURAHUA IN ECUADOR,
343
00:19:12,485 --> 00:19:15,920
MOUNT VESUVIUS IN ITALY,
344
00:19:15,989 --> 00:19:18,723
MOUNT ASAMA IN JAPAN,
345
00:19:18,791 --> 00:19:21,626
MOUNT SAINT HELENS
IN THE U.S.
346
00:19:21,694 --> 00:19:25,530
ALL ARE KNOWN FOR EXPLOSIVE,
DESTRUCTIVE ERUPTIONS.
347
00:19:27,033 --> 00:19:29,967
THEY ALSO GROW TO GREAT HEIGHTS.
348
00:19:30,036 --> 00:19:31,869
THIS IS CHIMBORAZO,
349
00:19:31,938 --> 00:19:35,106
RISING 20,700 FEET
ABOVE SEA LEVEL
350
00:19:35,175 --> 00:19:38,876
IN THE ANDES MOUNTAINS
OF ECUADOR.
351
00:19:38,945 --> 00:19:41,045
WHEN MEASURED FROM THE CENTER
OF THE EARTH'S CORE
352
00:19:41,114 --> 00:19:42,914
TO THE VOLCANO'S SUMMIT,
353
00:19:42,982 --> 00:19:45,983
CHIMBORAZO
IS EARTH'S TALLEST MOUNTAIN,
354
00:19:46,052 --> 00:19:50,288
SOARING OVER 7,000 FEET CLOSER
TO THE SUN THAN MOUNT EVEREST.
355
00:19:52,058 --> 00:19:55,159
THAT'S BECAUSE THE VOLCANO SITS
ON THE EQUATOR
356
00:19:55,228 --> 00:19:58,496
WHERE THE EARTH BULGES OUTWARD
FROM THE FORCE OF ROTATION.
357
00:20:03,870 --> 00:20:06,070
EARTH SCIENTISTS
HAVE GOTTEN A GOOD HANDLE
358
00:20:06,139 --> 00:20:08,172
ON THE FORCES
DRIVING PLATE TECTONICS,
359
00:20:08,241 --> 00:20:10,708
LIKE SUBDUCTION,
360
00:20:10,777 --> 00:20:13,377
BUT QUESTIONS REMAIN.
361
00:20:13,446 --> 00:20:17,448
ONE OF THE BIGGEST QUESTIONS
IS HOW PLATE TECTONICS IS LINKED
362
00:20:17,517 --> 00:20:20,885
TO PROCESSES OPERATING
DEEP BELOW EARTH'S CRUST.
363
00:20:23,356 --> 00:20:26,991
THE DEEPER WE LOOK,
THE LESS WE KNOW.
364
00:20:27,060 --> 00:20:29,894
BUT NEW RESEARCH
IS TURNING UP BIG SURPRISES
365
00:20:29,963 --> 00:20:32,763
LURKING IN THE CENTER
OF THE EARTH.
366
00:20:32,832 --> 00:20:34,865
- TUMBLE INTO CASCADING
SALT BEDS,
367
00:20:34,934 --> 00:20:38,269
ESCAPE FROM HISSING STEAM CAVES,
368
00:20:38,338 --> 00:20:41,939
BEHOLD THE STAGGERING
UNDERGROUND OCEAN.
369
00:20:42,008 --> 00:20:45,042
YOU WILL ENCOUNTER BREATHTAKING
DANGERS BEYOND BELIEF
370
00:20:45,111 --> 00:20:47,678
HERE AT THE CENTER OF THE EARTH.
371
00:20:47,747 --> 00:20:49,580
[thunder crashes]
372
00:20:49,649 --> 00:20:51,482
narrator:
THE INSIDE OF EARTH,
373
00:20:51,551 --> 00:20:53,985
AN OBJECT OF GREAT CURIOSITY,
374
00:20:54,053 --> 00:20:56,821
WILD CONJECTURE.
375
00:20:56,889 --> 00:20:59,590
AT THE CENTER OF IT ALL
IS THE EARTH'S CORE,
376
00:20:59,659 --> 00:21:05,396
WHICH WAS DISCOVERED
ACCIDENTALLY ONLY 140 YEARS AGO.
377
00:21:05,465 --> 00:21:08,332
- A HUGE EARTHQUAKE
IN THE 1880s WAS--
378
00:21:08,401 --> 00:21:10,001
THE WAVES FROM THAT EARTHQUAKE,
379
00:21:10,069 --> 00:21:11,569
TRAVELING THROUGH
THE EARTH'S CORE,
380
00:21:11,638 --> 00:21:13,904
BOUNCING OFF THE EARTH'S CORE,
381
00:21:13,973 --> 00:21:16,807
WERE RECOGNIZED AS ARRIVING
AT DIFFERENT TIMES
382
00:21:16,876 --> 00:21:18,409
FROM THE SEISMIC WAVES
383
00:21:18,478 --> 00:21:20,611
THAT TRAVELED THROUGH
THE OUTER LAYERS OF THE EARTH.
384
00:21:20,680 --> 00:21:23,481
AND WITH THAT,
THE EARTH'S CORE WAS DISCOVERED.
385
00:21:23,549 --> 00:21:26,050
IT TOOK UNTIL THE 1920s
TO RECOGNIZE
386
00:21:26,119 --> 00:21:28,619
THAT THE EARTH
HAD A SOLID INNER CORE
387
00:21:28,688 --> 00:21:32,156
INSIDE THE FLUID OUTER CORE.
388
00:21:32,225 --> 00:21:34,592
narrator: AT HALF THE SIZE
OF THE PLANET,
389
00:21:34,661 --> 00:21:40,231
THE EARTH'S CORE IS PECULIAR
IN THAT IT'S ALL MADE OF IRON.
390
00:21:40,300 --> 00:21:45,202
BUT ITS INNER HALF IS SOLID,
AND ITS OUTER HALF IS LIQUID.
391
00:21:45,271 --> 00:21:47,705
- THE EARTH'S OUTER CORE
IS MOLTEN
392
00:21:47,774 --> 00:21:49,940
BECAUSE IT'S VERY HIGH
TEMPERATURE, AND IT'S--
393
00:21:50,009 --> 00:21:51,676
THE TEMPERATURES ARE
ABOVE THE MELTING TEMPERATURE
394
00:21:51,744 --> 00:21:53,210
OF THIS IRON-RICH MATERIAL,
395
00:21:53,279 --> 00:21:55,446
BUT THE EARTH'S INNER CORE
IS ACTUALLY--CAN BE SOLID
396
00:21:55,515 --> 00:21:58,282
BECAUSE WE HAVE
EVEN HIGHER PRESSURES,
397
00:21:58,351 --> 00:22:00,785
SO GET TO OVER
3 MILLION ATMOSPHERES,
398
00:22:00,853 --> 00:22:03,921
SO 3 MILLION TIMES THE PRESSURE
AT THE SURFACE OF THE PLANET.
399
00:22:03,990 --> 00:22:05,489
AND AT THOSE HIGH PRESSURES,
400
00:22:05,558 --> 00:22:07,792
THEY CAUSE THE MATERIAL
TO ACTUALLY SOLIDIFY.
401
00:22:11,331 --> 00:22:14,265
narrator: FORTUNATELY FOR US
AND ALL LIVING THINGS,
402
00:22:14,334 --> 00:22:16,734
THE EARTH'S OUTER CORE IS FLUID,
403
00:22:16,803 --> 00:22:21,639
FOR IT GENERATES OUR PLANET'S
PROTECTIVE MAGNETIC FIELD.
404
00:22:21,708 --> 00:22:24,175
- IF WE DIDN'T HAVE THE EARTH'S
MAGNETIC FIELD TODAY,
405
00:22:24,243 --> 00:22:27,812
WE PROBABLY COULDN'T HAVE LIFE
ON THE SURFACE OF THE PLANET.
406
00:22:27,880 --> 00:22:30,681
THE SUN'S ALWAYS THROWING ALL
THESE PARTICLES AT THE PLANET,
407
00:22:30,750 --> 00:22:32,249
BUT THEN THE EARTH'S
MAGNETIC FIELD
408
00:22:32,318 --> 00:22:34,218
PROTECTS THIS NICE,
PROTECTIVE COATING
409
00:22:34,287 --> 00:22:36,787
THAT PROTECTS US
FROM THESE DAMAGING RAYS
410
00:22:36,856 --> 00:22:38,789
AND PARTICLE--
HIGH-ENERGY PARTICLES.
411
00:22:41,294 --> 00:22:42,960
narrator: THE EARTH IS UNIQUE
AMONG PLANETS
412
00:22:43,029 --> 00:22:45,763
IN HAVING A MAGNETIC FIELD.
413
00:22:45,832 --> 00:22:47,798
MARS HAD ONE EARLY ON,
414
00:22:47,867 --> 00:22:49,800
BUT ITS SMALL CORE
COOLED QUICKLY,
415
00:22:49,869 --> 00:22:52,803
AND IT WAS LOST AND, WITH IT,
416
00:22:52,872 --> 00:22:56,374
THE CHANCE FOR LIFE
TO TAKE HOLD ON ITS SURFACE.
417
00:22:56,442 --> 00:23:00,478
MEANWHILE, EARTH'S MAGNETIC
FIELD, FOR ALL ITS IMPORTANCE,
418
00:23:00,546 --> 00:23:04,181
IS NOT WELL UNDERSTOOD.
419
00:23:04,250 --> 00:23:07,251
WHAT IS GETTING CLEARER
IS WHAT IS ACTUALLY GOING ON
420
00:23:07,320 --> 00:23:09,353
IN THE EARTH'S CORE ITSELF.
421
00:23:09,422 --> 00:23:11,255
- OKAY.
LET'S PUT IT ON THERE.
422
00:23:11,324 --> 00:23:12,556
narrator:
THAT IS BECAUSE
423
00:23:12,625 --> 00:23:14,058
SCIENTISTS HAVE
FINALLY RE-CREATED
424
00:23:14,127 --> 00:23:17,595
THE CORE'S EXTREME CONDITIONS
IN THE LAB.
425
00:23:17,663 --> 00:23:21,665
3 MILLION ATMOSPHERES
AND 10,000 DEGREES FAHRENHEIT,
426
00:23:21,734 --> 00:23:24,869
THE SAME TEMPERATURE
AS THE SURFACE OF THE SUN.
427
00:23:28,040 --> 00:23:30,174
- SO YOU HAVE TO REACH
MILLIONS OF ATMOSPHERES,
428
00:23:30,243 --> 00:23:31,876
AND YOU HAVE TO REACH
THOUSANDS OF DEGREES,
429
00:23:31,944 --> 00:23:34,945
SO THAT'S A VERY CHALLENGING
TECHNOLOGICAL PROBLEM.
430
00:23:35,014 --> 00:23:35,946
OKAY, GREAT.
431
00:23:36,015 --> 00:23:38,849
LOOKS GOOD.
432
00:23:38,918 --> 00:23:41,218
SO ONE WAY TO REACH
THE VERY HIGH PRESSURES
433
00:23:41,287 --> 00:23:43,954
AND TEMPERATURES IN THE PLANET
IS TO COMPRESS MATERIALS
434
00:23:44,023 --> 00:23:45,823
BETWEEN THE TIPS
OF TWO DIAMONDS,
435
00:23:45,892 --> 00:23:49,126
AND SINCE DIAMOND IS THE HARDEST
MATERIAL ON THE PLANET,
436
00:23:49,195 --> 00:23:53,097
WE CAN GENERATE
VERY HIGH PRESSURES.
437
00:23:53,166 --> 00:23:54,498
AND THEN,
AT THE SAME TIME,
438
00:23:54,567 --> 00:23:56,867
WE CAN USE LASERS
TO HEAT THE SAMPLE
439
00:23:56,936 --> 00:23:58,702
AND TO REACH
THE SAME CONDITIONS
440
00:23:58,771 --> 00:24:02,873
WE THINK ARE INSIDE THE PLANET.
441
00:24:02,942 --> 00:24:07,511
narrator: THE CORE'S SUN-HOT
HEAT IS CRUCIAL TO UNDERSTAND.
442
00:24:07,580 --> 00:24:09,547
IT AFFECTS EVERYTHING
AT THE SURFACE,
443
00:24:09,615 --> 00:24:13,050
1,800 MILES ABOVE.
444
00:24:13,119 --> 00:24:14,351
TO GET UP HERE,
445
00:24:14,420 --> 00:24:18,422
IT TRAVELS THROUGH TWO LAYERS
OF SOLID ROCK.
446
00:24:18,491 --> 00:24:22,660
THE FIRST IS THE MANTLE,
EARTH'S BIGGEST LAYER BY FAR.
447
00:24:24,263 --> 00:24:25,863
AND THEN THE CRUST,
448
00:24:25,932 --> 00:24:29,733
REALLY JUST A THIN VENEER
ON THE EARTH.
449
00:24:29,802 --> 00:24:32,970
SCIENTISTS BELIEVE THAT
THE IMMENSE HEAT OF THE CORE
450
00:24:33,039 --> 00:24:36,173
MAKES THE MANTLE SO HOT
THAT IT ACTS LIKE A FLUID
451
00:24:36,242 --> 00:24:39,510
AND RISES
UNTIL IT HITS THE CRUST.
452
00:24:39,579 --> 00:24:43,581
SOME OF THE HEAT THEN CIRCULATES
ALONG THE CRUST'S UNDERSIDE
453
00:24:43,649 --> 00:24:47,852
UNTIL SUBDUCTING SLABS OF CRUST
TAKE IT DOWNWARD.
454
00:24:47,920 --> 00:24:51,822
IT'S A GIANT RECYCLING TREADMILL
CALLED CONVECTION.
455
00:24:53,826 --> 00:24:55,226
THROUGH EXPERIMENTS,
456
00:24:55,294 --> 00:24:57,962
SCIENTISTS HAVE CALCULATED
THAT HEAT'S ROUND TRIP
457
00:24:58,030 --> 00:25:01,632
FROM THE CORE TO THE CRUST
AND BACK TO THE CORE AGAIN
458
00:25:01,701 --> 00:25:05,402
TAKES 300 MILLION YEARS.
459
00:25:05,471 --> 00:25:07,938
THIS CIRCULATION OF HEAT
IS KEPT ALIVE
460
00:25:08,007 --> 00:25:09,940
BY THE SINKING
OF COLD, HEAVY PLATES
461
00:25:10,009 --> 00:25:12,676
INTO THE HOT MANTLE BELOW.
462
00:25:12,745 --> 00:25:14,078
IN OTHER WORDS,
463
00:25:14,146 --> 00:25:17,615
THOSE SLABS CAUSE
QUITE A STIR AS THEY DESCEND.
464
00:25:19,585 --> 00:25:21,819
- WE CAN TRACK THOSE SLABS
WITH TOMOGRAPHY
465
00:25:21,888 --> 00:25:24,388
DOWN AT LEAST
INTO THE MIDDLE MANTLE.
466
00:25:24,457 --> 00:25:26,524
AND PROBABLY THOSE SLABS
REACH ALL THE WAY
467
00:25:26,592 --> 00:25:28,425
TO THE CORE-MANTLE BOUNDARY,
468
00:25:28,494 --> 00:25:32,897
AND THERE'S A SLAB GRAVEYARD
THAT SITS ABOVE THE CORE.
469
00:25:32,965 --> 00:25:37,301
THAT SLAB GRAVEYARD
MAY IN TURN HELP DRIVE
470
00:25:37,370 --> 00:25:39,970
THE CONVECTION CELLS
IN EARTH'S MANTLE
471
00:25:40,039 --> 00:25:42,072
THAT IN TURN THEN REACH UP
472
00:25:42,141 --> 00:25:44,375
AND DRIVE THE PATTERN
OF PLATE TECTONICS
473
00:25:44,443 --> 00:25:46,243
AND THE SHIFTING PLATES
AT EARTH'S SURFACE.
474
00:25:48,347 --> 00:25:51,382
narrator: THE SINKING SLABS NOT
ONLY DRIVE HEAT IN THE MANTLE;
475
00:25:51,450 --> 00:25:54,385
THEY HAVE RADICALLY CHANGED
THE MAKEUP OF THE MANTLE
476
00:25:54,453 --> 00:25:58,856
OVER THE COURSE
OF GEOLOGIC TIME.
477
00:25:58,925 --> 00:26:03,060
- THE MANTLE IS A VERY
COMPLICATED MIXTURE OF THINGS
478
00:26:03,129 --> 00:26:05,329
THAT HAVE BEEN STIRRED
INTERNALLY
479
00:26:05,398 --> 00:26:07,565
AND THINGS THAT HAVE COME UP
TO THE SURFACE,
480
00:26:07,633 --> 00:26:11,368
BEEN OCEAN FLOOR FOR A WHILE,
AND THEN TAKEN BACK DOWN.
481
00:26:13,739 --> 00:26:16,540
IN THE 4.5 BILLION-YEAR HISTORY
OF THE EARTH,
482
00:26:16,609 --> 00:26:20,911
THE ENTIRE MANTLE HAS BEEN
CIRCULATED ABOUT ONCE.
483
00:26:20,980 --> 00:26:23,147
VIRTUALLY NOTHING
AT THE EARTH'S SURFACE
484
00:26:23,215 --> 00:26:25,449
OR IN THE INTERIOR IS PERMANENT.
485
00:26:25,518 --> 00:26:26,584
THINGS ARE CHANGING
ALL THE TIME.
486
00:26:31,357 --> 00:26:33,290
narrator:
HEAT RISING UP FROM THE CORE
487
00:26:33,359 --> 00:26:36,527
DOES NOT ALWAYS
RECYCLE BACK DOWN.
488
00:26:36,596 --> 00:26:39,964
SOMETIMES IT ESCAPES
ITS EARTHLY CONFINES
489
00:26:40,032 --> 00:26:44,902
AS VOLCANIC ERUPTIONS.
490
00:26:44,971 --> 00:26:46,670
EARTH IS BY FAR
491
00:26:46,739 --> 00:26:51,442
THE SOLAR SYSTEM'S MOST
VOLCANICALLY ACTIVE PLANET.
492
00:26:51,510 --> 00:26:56,313
VOLCANOES ARE NATURE'S MOST
VIOLENT AND DESTRUCTIVE FORCE.
493
00:26:56,382 --> 00:26:58,015
BUT IRONICALLY,
494
00:26:58,084 --> 00:27:01,752
THIS FORCE EMANATING FROM
THE EARTH'S MANTLE DEEP BELOW
495
00:27:01,821 --> 00:27:05,222
IS AT THE VERY ROOT
OF THE CREATION AND MAINTENANCE
496
00:27:05,291 --> 00:27:08,092
OF LIFE ON EARTH'S SURFACE.
497
00:27:09,862 --> 00:27:12,963
- VOLCANOES HAVE CERTAINLY
INFLUENCED LIFE ON EARTH.
498
00:27:13,032 --> 00:27:16,033
AND THAT'S NOT JUST WHEN
THEY HAVE A BIG ERUPTION
499
00:27:16,102 --> 00:27:17,334
AND PEOPLE DIE.
500
00:27:17,403 --> 00:27:22,506
BUT THEY ALSO MAY HAVE CREATED
LIFE ON EARTH.
501
00:27:22,575 --> 00:27:24,775
IN THE LAST FEW DECADES,
502
00:27:24,844 --> 00:27:28,412
HYDROTHERMAL VENTS WERE
DISCOVERED DEEP IN THE OCEAN,
503
00:27:28,481 --> 00:27:32,683
AND MINERALS ARE COMING OUT
THAT CAN ACTUALLY FEED LIFE
504
00:27:32,752 --> 00:27:34,385
AROUND THOSE VENTS,
505
00:27:34,453 --> 00:27:38,288
AND A VERY SURPRISING FIND
WAS THAT LIFE COULD EXIST
506
00:27:38,357 --> 00:27:41,392
AT SUCH DEPTH IN THE OCEAN.
507
00:27:45,531 --> 00:27:48,032
narrator: VOLCANOES WERE
THE ORIGINAL ARCHITECTS
508
00:27:48,100 --> 00:27:49,833
OF OUR ATMOSPHERE,
509
00:27:49,902 --> 00:27:52,836
UNLOCKING CO2 AND WATER
FROM THE MANTLE'S ROCKS
510
00:27:52,905 --> 00:27:54,905
AND TAKING THEM TO THE SURFACE.
511
00:27:56,976 --> 00:27:58,509
ONE OF THE LARGEST
CONCENTRATIONS
512
00:27:58,577 --> 00:28:02,012
OF ACTIVE VOLCANOES
ON EARTH IS IN JAPAN--
513
00:28:02,081 --> 00:28:04,081
MORE THAN 100.
514
00:28:04,150 --> 00:28:07,618
MOUNT FUJI
IS JAPAN'S LARGEST VOLCANO,
515
00:28:07,687 --> 00:28:11,755
RISING 12,400 FEET HIGH.
516
00:28:11,824 --> 00:28:15,859
THIS GRACEFUL PEAK IS
A MASSIVE SUBDUCTION VOLCANO,
517
00:28:15,928 --> 00:28:20,364
BUT THE LARGEST VOLCANOES
ON EARTH ARE 100 TIMES BIGGER.
518
00:28:22,101 --> 00:28:24,068
THEY BELONG TO A RARE CLASS
OF VOLCANO
519
00:28:24,136 --> 00:28:28,105
KNOWN AS A MANTLE PLUME VOLCANO,
520
00:28:28,174 --> 00:28:30,674
AND THE LARGEST OF ALL
ARE ON HAWAII.
521
00:28:33,979 --> 00:28:36,914
LAVA HAS BEEN ERUPTING
FROM THIS SPOT IN THE PACIFIC
522
00:28:36,982 --> 00:28:41,018
FOR AT LEAST 75 MILLION YEARS.
523
00:28:41,087 --> 00:28:46,190
IT BUILT MAUNA LOA, EARTH'S
LARGEST VOLCANO BY VOLUME.
524
00:28:46,258 --> 00:28:51,995
BUT MAUNA LOA IS NOT THE BIGGEST
VOLCANO IN THE SOLAR SYSTEM.
525
00:28:52,064 --> 00:28:54,098
- THE LARGEST VOLCANO
IN THE SOLAR SYSTEM
526
00:28:54,166 --> 00:28:58,035
IS OLYMPUS MONS ON MARS.
527
00:28:58,104 --> 00:29:00,904
IT'S ABOUT 26 KILOMETERS HIGH
528
00:29:00,973 --> 00:29:06,043
AND AROUND
600 KILOMETERS ACROSS.
529
00:29:08,214 --> 00:29:09,713
narrator:
COMPARED TO HAWAII,
530
00:29:09,782 --> 00:29:14,251
OLYMPUS MONS IS VASTLY BIGGER
IN ALL RESPECTS.
531
00:29:14,320 --> 00:29:18,822
WHY ARE EARTH'S VOLCANOES
SO MUCH SMALLER?
532
00:29:18,891 --> 00:29:21,291
- ON MARS,
THERE'S NO PLATE TECTONICS,
533
00:29:21,360 --> 00:29:26,497
SO THE SAME, LET'S SAY, HOT SPOT
CAN BUILD UP A VOLCANO
534
00:29:26,565 --> 00:29:30,501
IN THE SAME LOCATION FOR VERY,
VERY LONG PERIODS OF TIME.
535
00:29:33,906 --> 00:29:36,006
ON THE EARTH,
WE CAN'T HAVE THAT SITUATION
536
00:29:36,075 --> 00:29:39,176
BECAUSE THE PLATES ARE MOVING,
SO YOU GET, FOR EXAMPLE,
537
00:29:39,245 --> 00:29:43,313
HOT SPOT LIKE THE ONE THAT
FORMED THE HAWAIIAN VOLCANOES,
538
00:29:43,382 --> 00:29:47,484
BUT THE PLATE IS MOVING OVER IT,
SO IT PUNCHES ONE VOLCANO,
539
00:29:47,553 --> 00:29:48,919
BUT THEN THE PLATE MOVES,
540
00:29:48,988 --> 00:29:53,323
AND THE VOLCANO MOVES
SOMEWHERE ELSE.
541
00:29:53,392 --> 00:29:58,061
SO ON EARTH, WE DON'T REALLY
BUILD THOSE SIZES OF VOLCANOES.
542
00:29:59,732 --> 00:30:02,566
[fire roaring and crackling]
543
00:30:02,635 --> 00:30:05,502
narrator: THE SOURCE THAT FEEDS
EARTH'S GIANT VOLCANOES
544
00:30:05,571 --> 00:30:08,105
IS THOUGHT TO BE
A NARROW CYLINDER OF HOT ROCK
545
00:30:08,174 --> 00:30:11,141
THAT REACHES DEEP
INTO THE MANTLE.
546
00:30:11,210 --> 00:30:14,077
HOW DEEP IS A MATTER OF DEBATE.
547
00:30:14,146 --> 00:30:16,647
BUT RECENT SEISMIC STUDIES
OF THE HAWAIIAN CHAIN
548
00:30:16,715 --> 00:30:18,949
IMAGED FOR THE FIRST TIME
549
00:30:19,018 --> 00:30:22,219
A HOT PLUME REACHING HALFWAY
TO THE EARTH'S CORE.
550
00:30:24,356 --> 00:30:27,758
CHEMICAL ANALYSIS OF LAVAS
RETRIEVED IN DRILL CORES
551
00:30:27,827 --> 00:30:30,394
TRACES THE PLUME EVEN DEEPER,
552
00:30:30,462 --> 00:30:33,864
ACTUALLY EXTENDING
TO THE EARTH'S CORE ITSELF.
553
00:30:36,769 --> 00:30:39,336
THE DEEPEST REACHES
OF OUR PLANET, THEN,
554
00:30:39,405 --> 00:30:40,938
ARE INTIMATELY CONNECTED
555
00:30:41,006 --> 00:30:44,174
WITH GEOLOGICAL ACTION
AT THE SURFACE.
556
00:30:47,246 --> 00:30:49,313
WITHOUT THESE
DEEP-SEATED FORCES,
557
00:30:49,381 --> 00:30:54,818
LIFE WOULD HAVE NOT GAINED
A FOOTHOLD ON OUR PLANET,
558
00:30:54,887 --> 00:30:56,286
AND IT WOULDN'T HAVE FLOURISHED
559
00:30:56,355 --> 00:30:59,489
AND EVOLVED INTO COUNTLESS
WONDROUS FORMS
560
00:30:59,558 --> 00:31:02,492
WITHOUT SOMETHING ELSE:
561
00:31:02,561 --> 00:31:05,929
A REMARKABLY STABLE,
PRECISELY TUNED CLIMATE.
562
00:31:11,770 --> 00:31:14,204
FOR MOST OF EARTH'S EXISTENCE,
563
00:31:14,273 --> 00:31:16,807
THE TEMPERATURE AT THE SURFACE
HAS RARELY WAVERED.
564
00:31:18,677 --> 00:31:22,079
WHY THIS IS
IS A GREAT MYSTERY.
565
00:31:22,147 --> 00:31:26,917
THE GLOBAL MEAN TEMPERATURE
IS A COMFORTABLE 59 DEGREES.
566
00:31:26,986 --> 00:31:29,253
INCREASE THAT
BY JUST 18 DEGREES,
567
00:31:29,321 --> 00:31:33,690
AND ICE AT THE POLES WOULD MELT.
568
00:31:33,759 --> 00:31:36,159
DECREASE IT BY 18 DEGREES,
569
00:31:36,228 --> 00:31:38,962
AND THE ENTIRE WORLD
WOULD FREEZE OVER.
570
00:31:40,666 --> 00:31:43,767
OTHER PLANETS
ARE FAR FROM HABITABLE.
571
00:31:43,836 --> 00:31:47,170
VENUS,
WITH 200,000 TIMES MORE CO2
572
00:31:47,239 --> 00:31:49,106
IN ITS ATMOSPHERE THAN EARTH,
573
00:31:49,174 --> 00:31:53,176
IS RAVAGED BY TEMPERATURES
REACHING 900 DEGREES FAHRENHEIT.
574
00:31:55,915 --> 00:31:59,950
MARS, LONG AGO STRIPPED OF ITS
ATMOSPHERE AND MAGNETIC SHIELD,
575
00:32:00,019 --> 00:32:05,188
IS DEEPLY FROZEN TO AN AVERAGE
OF 70 DEGREES BELOW ZERO.
576
00:32:05,257 --> 00:32:08,292
[lively music]
577
00:32:08,360 --> 00:32:12,663
¶ ¶
578
00:32:12,731 --> 00:32:16,066
EARTH'S CLIMATE IS KEPT MODERATE
BY A LITTLE UNDERSTOOD INTERPLAY
579
00:32:16,135 --> 00:32:20,404
OF GEOLOGIC AND BIOLOGIC FORCES.
580
00:32:20,472 --> 00:32:24,207
VOLCANIC ERUPTIONS SPEW CO2
INTO THE AIR.
581
00:32:24,276 --> 00:32:27,177
PLATE TECTONICS BUILDS MOUNTAINS
582
00:32:27,246 --> 00:32:30,714
AND RIFTS APART OCEAN BASINS.
583
00:32:30,783 --> 00:32:33,250
THEN WEATHER ERODES THE LAND,
584
00:32:33,319 --> 00:32:35,018
CAPTURING CO2
585
00:32:35,087 --> 00:32:38,221
AND LOCKING IT AWAY
IN SEDIMENTS.
586
00:32:38,290 --> 00:32:42,859
LIVING ORGANISMS ADD
THEIR ALTERATIONS INTO THE MIX.
587
00:32:42,928 --> 00:32:46,830
ALL IS BUILT INTO A SYSTEM
OF GLOBAL CHECKS AND BALANCES.
588
00:32:50,903 --> 00:32:52,602
THERE HAVE BEEN ONLY A FEW TIMES
589
00:32:52,671 --> 00:32:56,807
WHEN EARTH'S CLIMATE TIPPED
WELL BEYOND ITS COMFORT ZONE.
590
00:32:56,875 --> 00:33:02,312
EARTH'S COLDEST EXTREME HAPPENED
ABOUT 750 MILLION YEARS AGO
591
00:33:02,381 --> 00:33:05,983
AND PROBABLY SEVERAL TIMES
BEFORE THAT.
592
00:33:06,051 --> 00:33:10,087
IT WAS CALLED SNOWBALL EARTH.
593
00:33:10,155 --> 00:33:12,756
- SNOWBALL EARTH REFERS
TO A TIME IN THE EARTH'S HISTORY
594
00:33:12,825 --> 00:33:16,193
WHEN THE EARTH
WAS ENTIRELY COVERED WITH ICE.
595
00:33:16,261 --> 00:33:18,862
THAT MEANS GLACIERS
ON THE CONTINENTS
596
00:33:18,931 --> 00:33:21,198
AND SEA ICE COVERING
MOST OF THE OCEANS
597
00:33:21,266 --> 00:33:24,668
ALL THE WAY DOWN TO THE EQUATOR.
598
00:33:24,737 --> 00:33:26,370
narrator:
DURING SNOWBALL EARTH,
599
00:33:26,438 --> 00:33:28,305
THE TEMPERATURE
AT THE EQUATOR PLUNGED
600
00:33:28,374 --> 00:33:31,208
TO MINUS 4 DEGREES FAHRENHEIT.
601
00:33:31,276 --> 00:33:34,144
LIFE, STILL IN
ITS PRIMITIVE BACTERIAL STAGE,
602
00:33:34,213 --> 00:33:37,714
SURVIVED THE DEEP FREEZE
AS IT DOES TODAY:
603
00:33:37,783 --> 00:33:40,884
BELOW ICE SHELVES
AND EVEN BELOW GLACIERS.
604
00:33:43,589 --> 00:33:46,723
SCIENTISTS THINK THAT
THE TRIGGER FOR SNOWBALL EARTH
605
00:33:46,792 --> 00:33:52,062
WAS THE BUNCHING
OF CONTINENTS AT THE EQUATOR.
606
00:33:52,131 --> 00:33:54,598
THE GIANT LAND MASS
ATTRACTED MOISTURE,
607
00:33:54,666 --> 00:33:57,601
AND GREAT STORMS ENSUED.
608
00:33:57,669 --> 00:34:00,771
RAIN STRIPPED CO2
FROM THE ATMOSPHERE
609
00:34:00,839 --> 00:34:05,242
AND LOCKED IT
IN ERODING SEDIMENTS.
610
00:34:05,310 --> 00:34:08,612
AS CO2 LEVELS DROPPED,
SO DID THE TEMPERATURE.
611
00:34:14,920 --> 00:34:18,722
VOLCANIC ERUPTIONS EVENTUALLY
OVERPOWERED SNOWBALL EARTH
612
00:34:18,791 --> 00:34:23,427
BY INJECTING CO2
BACK INTO THE ATMOSPHERE.
613
00:34:23,495 --> 00:34:25,328
AS THE CLIMATE RESTABILIZED,
614
00:34:25,397 --> 00:34:28,932
THE SURVIVING BACTERIAL
LIFE FORMS MULTIPLIED,
615
00:34:29,001 --> 00:34:30,667
PHOTOSYNTHESIZED,
616
00:34:30,736 --> 00:34:33,036
AND FILLED THE AIR WITH OXYGEN,
617
00:34:33,105 --> 00:34:36,073
A REQUIREMENT
FOR MORE COMPLEX LIFE.
618
00:34:37,743 --> 00:34:41,711
FINALLY, 550 MILLION YEARS AGO,
619
00:34:41,780 --> 00:34:44,714
LIFE BRANCHED OUT AND BEGAN
ITS EXTRAORDINARY JOURNEY
620
00:34:44,783 --> 00:34:47,717
OF DIVERSIFICATION
AND EVOLUTION.
621
00:34:50,722 --> 00:34:54,357
WHY THIS HAPPENED
IS STILL A MYSTERY,
622
00:34:54,426 --> 00:34:56,960
BUT THE EXTREME HIT
THAT LIFE TOOK
623
00:34:57,029 --> 00:34:58,495
DURING SNOWBALL EARTH
624
00:34:58,564 --> 00:35:03,100
MAY HAVE ACTUALLY BEEN
PART OF THE REASON.
625
00:35:03,168 --> 00:35:05,001
- ONCE LIFE WAS ESTABLISHED
ON THE EARTH,
626
00:35:05,070 --> 00:35:08,004
IT CONTINUED TO SHOW EVIDENCE
THAT IT WAS EXTREMELY ADAPTABLE,
627
00:35:08,073 --> 00:35:11,408
THAT WHATEVER HARSH CONDITIONS
WERE THROWN AT IT,
628
00:35:11,477 --> 00:35:15,612
THAT IT WAS ABLE TO ADAPT
TO FIND A WAY TO SURVIVE.
629
00:35:15,681 --> 00:35:18,482
SO EVEN THROUGH PERIODS
LIKE SNOWBALL EARTH,
630
00:35:18,550 --> 00:35:21,585
LIFE WOULD ADAPT TO THOSE
CONDITIONS AND REEMERGE.
631
00:35:21,653 --> 00:35:24,821
AND IN FACT, THOSE SORTS OF
CONDITIONS WERE MAJOR FACTORS
632
00:35:24,890 --> 00:35:26,857
DRIVING THE EVOLUTION
OF LIFE ON EARTH.
633
00:35:31,230 --> 00:35:34,397
narrator: THE NEXT TIME EARTH'S
CLIMATE WAS KNOCKED OFF BALANCE
634
00:35:34,466 --> 00:35:38,034
WAS AT A TIME WHEN EARTH
EXPERIENCED ITS BIGGEST UPHEAVAL
635
00:35:38,103 --> 00:35:41,771
SINCE THE EARLY DAYS
OF ITS FORMATION.
636
00:35:41,840 --> 00:35:44,908
- ABOUT 250 MILLION YEARS AGO,
637
00:35:44,977 --> 00:35:48,211
95% OF LIFE ON EARTH
DISAPPEARED.
638
00:35:50,849 --> 00:35:53,517
WE THINK THAT'S BECAUSE
OF VERY LARGE ERUPTIONS
639
00:35:53,585 --> 00:35:56,720
IN THE SIBERIAN TRAPS.
640
00:35:56,788 --> 00:36:00,023
[clacking]
641
00:36:00,092 --> 00:36:04,060
narrator: EARTH SCIENTISTS HAVE
MAPPED 800,000 SQUARE MILES
642
00:36:04,129 --> 00:36:06,997
OF SIBERIA THAT WERE COVERED
BY LAVA FLOWS
643
00:36:07,065 --> 00:36:10,467
UP TO 12,000 FEET THICK.
644
00:36:10,536 --> 00:36:14,538
THEY CALL THIS PROVINCE
THE SIBERIAN TRAPS.
645
00:36:14,606 --> 00:36:17,908
- THOSE ERUPTIONS
WOULD HAVE PUT A LOT OF DUST,
646
00:36:17,976 --> 00:36:21,077
A LOT OF SULFUR
IN THE ATMOSPHERE,
647
00:36:21,146 --> 00:36:23,713
COOLED THE TEMPERATURE.
648
00:36:23,782 --> 00:36:27,851
SO THIS KILLED
A LOT OF LIFE ON EARTH.
649
00:36:27,920 --> 00:36:32,389
narrator: THE CLIMATE RECOVERED
EVENTUALLY, AND SO DID LIFE.
650
00:36:32,457 --> 00:36:33,957
BUT 90 MILLION YEARS AGO,
651
00:36:34,026 --> 00:36:38,595
THE HOTTEST PERIOD EVER KNOWN
ENVELOPED THE EARTH.
652
00:36:38,664 --> 00:36:42,032
DINOSAURS ROAMED
WHAT ARE NOW THE ICY REALMS
653
00:36:42,100 --> 00:36:44,034
OF THE ARCTIC CIRCLE.
654
00:36:44,102 --> 00:36:49,172
AROUND THEM WERE FELLOW
SWAMP-DWELLERS LIKE ALLIGATORS.
655
00:36:49,241 --> 00:36:53,009
WHAT WERE THEY DOING
AT THE EARTH'S POLES?
656
00:36:53,078 --> 00:36:57,180
SCIENTISTS FIGURED OUT THAT
PLATE TECTONICS WAS THE CULPRIT.
657
00:36:58,650 --> 00:37:00,417
100 MILLION YEARS AGO,
658
00:37:00,485 --> 00:37:02,252
THE CONTINENTS
HAD WRENCHED APART,
659
00:37:02,321 --> 00:37:05,255
AND SEA LEVEL ROSE.
660
00:37:05,324 --> 00:37:07,557
MOUNTAIN BUILDING SLOWED DOWN,
661
00:37:07,626 --> 00:37:11,294
AND SO DID RAINFALL AND EROSION.
662
00:37:11,363 --> 00:37:13,763
BUT CO2-SPEWING
VOLCANIC ERUPTIONS,
663
00:37:13,832 --> 00:37:19,436
ESPECIALLY IN THE MID-OCEAN
RIFT ZONES, DID NOT.
664
00:37:19,504 --> 00:37:21,204
- WHEN CONTINENTS
ARE SPLITTING APART
665
00:37:21,273 --> 00:37:23,240
AND YOU HAVE MORE SEA FLOOR
SPREADING,
666
00:37:23,308 --> 00:37:25,675
YOU'RE ADDING MORE CO2
TO THE ATMOSPHERE,
667
00:37:25,744 --> 00:37:28,478
AND IT'S NOT BEING REMOVED
AS QUICKLY
668
00:37:28,547 --> 00:37:32,048
BY WEATHERING OF THE CONTINENTS,
669
00:37:32,117 --> 00:37:34,584
SO IT'S WARMER
DURING THOSE PERIODS.
670
00:37:34,653 --> 00:37:36,586
[bird cawing]
671
00:37:36,655 --> 00:37:39,189
narrator: TEMPERATURES ROSE
TO A BALMY 54 DEGREES
672
00:37:39,258 --> 00:37:42,892
AT THE NORTH AND SOUTH POLES.
673
00:37:42,961 --> 00:37:45,395
THE CLIMATE SO AGREED
WITH THE DINOSAURS
674
00:37:45,464 --> 00:37:49,399
THAT THEY DOMINATED LIFE
ON EARTH FOR MILLIONS OF YEARS.
675
00:37:51,336 --> 00:37:54,537
THEN,
65 MILLION YEARS AGO,
676
00:37:54,606 --> 00:37:58,308
A MASSIVE METEORITE IMPACT
SUDDENLY ENDED THEIR REIGN.
677
00:37:58,377 --> 00:38:01,211
[explosion]
678
00:38:05,384 --> 00:38:07,884
THE METEORITE GOUGED OUT
A HUGE CRATER
679
00:38:07,953 --> 00:38:09,586
OVER 100 MILES ACROSS
680
00:38:09,655 --> 00:38:13,223
WITH THE TOWN OF CHICXULUB,
MEXICO, AT ITS CENTER.
681
00:38:16,461 --> 00:38:19,963
THE CITY OF MERIDA
ALSO LIES WITHIN THE CRATER,
682
00:38:20,032 --> 00:38:23,800
WHICH WAS BURIED BY SEDIMENT
MILLIONS OF YEARS AGO
683
00:38:23,869 --> 00:38:27,203
AND ONLY DISCOVERED BY CHANCE
AS GEOLOGISTS EXPLORED FOR OIL
684
00:38:27,272 --> 00:38:29,105
IN THE 1970s.
685
00:38:34,046 --> 00:38:36,780
THE CRATER AND ITS SURROUNDINGS
ARE ALSO THE SITE
686
00:38:36,848 --> 00:38:40,216
OF THE GREAT CITIES
BUILT BY THE ANCIENT MAYA.
687
00:38:40,285 --> 00:38:43,086
BUT NONE OF THE HUMAN DRAMA
PLAYING OUT IN THIS REGION
688
00:38:43,155 --> 00:38:44,688
WOULD HAVE BEEN POSSIBLE
689
00:38:44,756 --> 00:38:46,723
IF IT WEREN'T
FOR THE KILLER METEORITE
690
00:38:46,792 --> 00:38:48,458
THAT STRUCK HERE,
691
00:38:48,527 --> 00:38:51,761
WIPING OUT THE DINOSAURS.
692
00:38:51,830 --> 00:38:54,531
THEIR EXTINCTION OPENED
AN EVOLUTIONARY DOOR
693
00:38:54,599 --> 00:38:57,267
FOR MAMMALS LIKE US TO EVOLVE.
694
00:39:00,405 --> 00:39:02,639
BUT 65 MILLION YEARS AGO,
695
00:39:02,708 --> 00:39:04,708
THE EARTHLY STAGE
WAS FAR FROM SET
696
00:39:04,776 --> 00:39:07,744
FOR THE ENTRANCE OF PEOPLE.
697
00:39:07,813 --> 00:39:12,182
CO2 LEVELS AND TEMPERATURES
WERE MUCH TOO HIGH.
698
00:39:12,250 --> 00:39:16,519
LUCKILY FOR US, PLATE TECTONICS
BUILT THE MOST MASSIVE STRUCTURE
699
00:39:16,588 --> 00:39:20,490
ON EARTH TO MAKE
THE CLIMATE HUMAN-FRIENDLY:
700
00:39:20,559 --> 00:39:25,128
THE GREAT HIMALAYA RANGE.
701
00:39:25,197 --> 00:39:29,499
ABOUT 60 MILLION YEARS AGO,
INDIA, ONCE A MASSIVE ISLAND,
702
00:39:29,568 --> 00:39:33,169
RAMMED ASIA, AND THE BUILDING
OF THE HIMALAYA BEGAN.
703
00:39:35,841 --> 00:39:37,741
AS THE HIMALAYAS GREW,
704
00:39:37,809 --> 00:39:42,112
A GREAT BLOCK OF LAND
ROSE UP BEHIND THE RANGE.
705
00:39:42,180 --> 00:39:44,247
IT FORMED THE TIBETAN PLATEAU
706
00:39:44,316 --> 00:39:48,184
AND EVEN RAISED THE LAND
AS FAR TO THE NORTH AS MONGOLIA,
707
00:39:48,253 --> 00:39:51,654
MORE THAN 1,000 MILES AWAY.
708
00:39:51,723 --> 00:39:55,392
SINCE THEN, THE EARTH'S CLIMATE
HAS NEVER BEEN THE SAME.
709
00:39:59,264 --> 00:40:02,132
- THERE'S A REAL BELIEF
AMONGST GEOLOGISTS
710
00:40:02,200 --> 00:40:05,402
THAT THE GROWTH OF THE HIMALAYA
IN TIBET
711
00:40:05,470 --> 00:40:08,471
OVER THE LAST 60 MILLION YEARS
712
00:40:08,540 --> 00:40:11,174
HAS LED TO MAJOR CHANGES
IN THE GLOBAL CLIMATE.
713
00:40:13,578 --> 00:40:16,479
THE INDIAN MONSOON IS CREATED
714
00:40:16,548 --> 00:40:19,449
WHEN WARM AIR
FROM THE INDIAN OCEAN
715
00:40:19,518 --> 00:40:21,518
MEETS THE MOUNTAINS
OF THE HIMALAYA
716
00:40:21,586 --> 00:40:25,588
AND DUMPS THE RAIN
ON THAT MOUNTAIN FRONT.
717
00:40:25,657 --> 00:40:28,691
PRIOR TO THE FORMATION
OF THE HIMALAYA IN TIBET,
718
00:40:28,760 --> 00:40:30,360
THERE WAS NO MONSOON.
719
00:40:30,429 --> 00:40:33,096
THERE WAS NO BARRIER
TO THE NORTHWARD PROGRESS
720
00:40:33,165 --> 00:40:35,231
OF THE MOIST INDIAN OCEAN AIR.
721
00:40:38,804 --> 00:40:41,471
narrator: THE NEW MONSOON
BEGAN DUMPING RAIN AND SNOW
722
00:40:41,540 --> 00:40:45,141
ON THE GROWING MOUNTAINS
OF ASIA.
723
00:40:45,210 --> 00:40:48,077
THIS ERODED THE ROCKS
AND CHANGED THE CHEMICAL BALANCE
724
00:40:48,146 --> 00:40:51,481
IN THE ATMOSPHERE.
725
00:40:51,550 --> 00:40:55,084
MASSIVE AMOUNTS OF CO2
WERE REMOVED FROM THE AIR,
726
00:40:55,153 --> 00:40:58,788
SO MUCH THAT THE GLOBAL CLIMATE
BEGAN TO COOL.
727
00:41:01,426 --> 00:41:04,494
IT WAS THE FIRST TIME IN
HUNDREDS OF MILLIONS OF YEARS
728
00:41:04,563 --> 00:41:09,032
THAT THE EARTH'S CLIMATE
COOLED SO DEEPLY.
729
00:41:09,100 --> 00:41:12,068
BUT BEFORE WE HUMANS
MADE OUR APPEARANCE,
730
00:41:12,137 --> 00:41:15,505
PLATE TECTONICS HAD A FEW MORE
MODIFICATIONS TO MAKE.
731
00:41:18,343 --> 00:41:20,009
- ALL RIGHT, HERE.
HERE WE GO.
732
00:41:20,078 --> 00:41:21,544
narrator:
IN ANTARCTICA,
733
00:41:21,613 --> 00:41:24,914
SCIENTISTS MADE
THE STARTLING DISCOVERY
734
00:41:24,983 --> 00:41:27,450
THAT THIS LONELY CONTINENT
AT THE BOTTOM OF THE WORLD
735
00:41:27,519 --> 00:41:31,554
WAS ONCE CONNECTED TO AUSTRALIA.
736
00:41:31,623 --> 00:41:34,491
THEN 40 MILLION YEARS AGO,
737
00:41:34,559 --> 00:41:37,160
THE LAND MASSES RIFTED APART,
738
00:41:37,229 --> 00:41:41,965
COMPLETELY CHANGING
OCEAN CURRENTS IN THE REGION.
739
00:41:42,033 --> 00:41:43,733
- OVER THE LAST
40 MILLION YEARS,
740
00:41:43,802 --> 00:41:46,903
ANTARCTICA BECAME AN ISOLATED
CONTINENT DOWN THERE,
741
00:41:46,972 --> 00:41:51,808
AND SO THE CIRCUM-ANTARCTIC
CURRENT FORMED,
742
00:41:51,877 --> 00:41:54,878
WHICH ISOLATED THAT CONTINENT
SO IT COULD COOL
743
00:41:54,946 --> 00:41:56,613
AND START TO GROW AN ICE SHEET.
744
00:42:00,252 --> 00:42:01,384
narrator:
FOR THE FIRST TIME,
745
00:42:01,453 --> 00:42:03,553
ANTARCTICA BECAME FROZEN
WITH ICE,
746
00:42:03,622 --> 00:42:06,189
UP TO 15,000 FEET THICK,
747
00:42:06,258 --> 00:42:10,727
DROPPING GLOBAL TEMPERATURES
EVEN MORE.
748
00:42:10,795 --> 00:42:13,463
AND THEN,
3 MILLION YEARS AGO,
749
00:42:13,532 --> 00:42:17,367
A NEW LAND BRIDGE WELDED SOUTH
AND NORTH AMERICA TOGETHER.
750
00:42:19,604 --> 00:42:22,038
BEFORE THAT, THE TWO CONTINENTS
WERE SEPARATED
751
00:42:22,107 --> 00:42:25,875
BY THE ANCIENT PANAMA SEAWAY.
752
00:42:25,944 --> 00:42:28,611
AS PLATE TECTONICS
JOINED THEM TOGETHER,
753
00:42:28,680 --> 00:42:33,149
OCEAN CURRENTS WERE RADICALLY
REROUTED ONCE AGAIN.
754
00:42:33,218 --> 00:42:36,653
- THE GULF STREAM, INSTEAD OF
GOING INTO THE PACIFIC OCEAN,
755
00:42:36,721 --> 00:42:40,857
IT ACTUALLY WAS THEN REDIRECTED
UPWARD IN THE ATLANTIC,
756
00:42:40,926 --> 00:42:46,529
BRINGING MORE MOISTURE
UP INTO THE NORTH ATLANTIC,
757
00:42:46,598 --> 00:42:48,932
AND THAT'S A SOURCE
OF MOISTURE FOR ICE
758
00:42:49,000 --> 00:42:53,202
ON THE CONTINENTS UP THERE.
759
00:42:53,271 --> 00:42:55,805
narrator:
BY 2 1/2 MILLION YEARS AGO,
760
00:42:55,874 --> 00:43:00,043
TEMPERATURES PLUNGED SO MUCH
THAT THE PLEISTOCENE ICE AGES
761
00:43:00,111 --> 00:43:03,146
WERE TRIGGERED,
762
00:43:03,214 --> 00:43:05,148
AND IN THIS ICE AGE WORLD,
763
00:43:05,216 --> 00:43:07,684
WHEN FREEZING GLACIAL PERIODS
ALTERNATED
764
00:43:07,752 --> 00:43:10,620
WITH MUCH WARMER INTERGLACIALS,
765
00:43:10,689 --> 00:43:13,022
THE STORY OF HUMAN EVOLUTION
UNFOLDED
766
00:43:13,091 --> 00:43:15,091
IN THE EAST AFRICAN RIFT.
767
00:43:17,963 --> 00:43:21,130
[women conversing]
768
00:43:21,199 --> 00:43:23,633
HUMANS HAVE LIVED
THROUGH EIGHT MAJOR ICE AGES
769
00:43:23,702 --> 00:43:26,402
OVER THE PAST MILLION YEARS.
770
00:43:26,471 --> 00:43:30,139
THE LAST GLACIAL PERIOD
ENDED 10,000 YEARS AGO,
771
00:43:30,208 --> 00:43:35,044
AND WE ARE NOW AT THE TAIL END
OF AN INTERGLACIAL.
772
00:43:35,113 --> 00:43:38,047
THE CLIMATE HAS BEEN
WARM ON AVERAGE,
773
00:43:38,116 --> 00:43:41,117
BUT WITH ENOUGH VARIATION
TO PROFOUNDLY AFFECT PEOPLE
774
00:43:41,186 --> 00:43:45,355
AND EVEN CIVILIZATIONS.
775
00:43:45,423 --> 00:43:48,925
- ONCE WE ENTERED
THE WARM PERIOD WE'RE IN NOW
776
00:43:48,994 --> 00:43:51,861
THAT STARTED
ABOUT 10,000 YEARS AGO,
777
00:43:51,930 --> 00:43:54,998
THE CHANGES IN CLIMATE
HAVE BEEN RELATIVELY SMALLER
778
00:43:55,066 --> 00:43:57,300
THAN THE ICE AGES,
779
00:43:57,369 --> 00:43:58,968
BUT THEY'VE BEEN BIG ENOUGH
780
00:43:59,037 --> 00:44:03,306
THAT THERE WERE DROUGHTS
AND FLOODS AND COLD PERIODS
781
00:44:03,375 --> 00:44:05,408
AND LITTLE MINI ICE AGES.
782
00:44:05,477 --> 00:44:07,443
AND THAT PEOPLE
WERE STILL MIGRATING
783
00:44:07,512 --> 00:44:10,380
AND STILL HAVING TO ADAPT.
784
00:44:12,684 --> 00:44:16,386
narrator: RESEARCHERS STUDYING
PAST CLIMATE CHANGES
785
00:44:16,454 --> 00:44:18,955
IN GUATEMALA FOUND
THAT LONG DROUGHTS OCCURRED
786
00:44:19,024 --> 00:44:21,557
AT THE HEIGHT OF
THE ANCIENT MAYA CIVILIZATION,
787
00:44:21,626 --> 00:44:26,663
FROM 3,000 TO 1,000 YEARS AGO.
788
00:44:26,731 --> 00:44:28,464
THIS MAY HAVE BEEN A BIG FACTOR
789
00:44:28,533 --> 00:44:31,601
IN THE MAYA CIVILIZATION'S
MYSTERIOUS COLLAPSE.
790
00:44:36,975 --> 00:44:40,510
BECAUSE GLOBAL WARMING IS
AGAIN CREATING SERIOUS PROBLEMS
791
00:44:40,578 --> 00:44:42,645
FOR PEOPLE AND ECOSYSTEMS,
792
00:44:42,714 --> 00:44:45,848
SCIENTISTS ARE ENGAGED
IN AN URGENT EFFORT
793
00:44:45,917 --> 00:44:48,217
TO STUDY PAST CLIMATE CHANGES
794
00:44:48,286 --> 00:44:53,356
IN ORDER TO PREDICT
WHAT MIGHT HAPPEN IN THE FUTURE.
795
00:44:53,425 --> 00:44:56,359
ONE OF THEIR BEST TOOLS
IS THE STUDY OF GASES
796
00:44:56,428 --> 00:44:58,528
THAT CAUSE GLOBAL WARMING,
797
00:44:58,596 --> 00:45:03,266
ESPECIALLY CARBON DIOXIDE,
OR CO2.
798
00:45:03,334 --> 00:45:06,936
THESE GASES ARE DETECTED
IN ANCIENT GLACIAL ICE
799
00:45:07,005 --> 00:45:10,073
HUNDREDS OF THOUSANDS
OF YEARS OLD IN ANTARCTICA.
800
00:45:12,410 --> 00:45:15,211
- ATMOSPHERIC GASES
GET TRAPPED IN THE ICE,
801
00:45:15,280 --> 00:45:18,114
AND YOU GET THESE TRAPPED
BUBBLES OF ATMOSPHERE
802
00:45:18,183 --> 00:45:19,982
THAT ARE PRESERVED,
803
00:45:20,051 --> 00:45:22,685
AND SO WHEN YOU TAKE
THE ICE CORE,
804
00:45:22,754 --> 00:45:27,724
YOU HAVE THIS SORT OF
ANCIENT ATMOSPHERE.
805
00:45:27,792 --> 00:45:31,327
AND SO THEY CAN RELEASE THAT
AND MEASURE THE AMOUNT OF CO2
806
00:45:31,396 --> 00:45:32,962
THAT WAS AROUND.
807
00:45:33,031 --> 00:45:36,933
AND ALSO HOW IT CHANGED
SINCE THE LAST ICE AGE.
808
00:45:38,737 --> 00:45:42,772
SO WE KNOW FROM THE ICE CORES
THAT THE NATURAL LEVEL OF CO2
809
00:45:42,841 --> 00:45:45,341
SHOULD BE
ABOUT 280 PARTS PER MILLION,
810
00:45:45,410 --> 00:45:48,678
AND TODAY IT'S
ABOUT 390 PARTS PER MILLION,
811
00:45:48,747 --> 00:45:52,615
AS HUMANS HAVE BEEN BURNING
FOSSIL FUELS AND RELEASING CO2.
812
00:45:56,488 --> 00:45:58,121
THAT'S A REALLY BIG RISE.
813
00:45:58,189 --> 00:46:02,091
WE'VE NEVER SEEN THIS RAPID
A RISE OF CO2
814
00:46:02,160 --> 00:46:03,726
IN THE ATMOSPHERE
815
00:46:03,795 --> 00:46:06,462
OVER, YOU KNOW,
100 MILLION YEARS.
816
00:46:10,435 --> 00:46:13,836
narrator: SO IT APPEARS
THAT ONE NATURAL EARTH SYSTEM,
817
00:46:13,905 --> 00:46:15,238
THE CLIMATE,
818
00:46:15,306 --> 00:46:18,341
MAY INDEED BE ENTERING
A PERIOD OF INTENSE UPHEAVAL.
819
00:46:20,178 --> 00:46:23,012
[rumbling]
820
00:46:26,284 --> 00:46:28,751
WHAT ABOUT THE OTHER
NATURAL EARTH SYSTEMS,
821
00:46:28,820 --> 00:46:32,688
LIKE THOSE THAT CAUSE
EARTHQUAKES AND VOLCANOES?
822
00:46:32,757 --> 00:46:36,225
- ICELAND'S MOST ACTIVE VOLCANO
HAS STARTED ERUPTING.
823
00:46:36,294 --> 00:46:37,460
narrator:
HAVE ANY OF THESE
824
00:46:37,529 --> 00:46:39,862
BEGUN A PERIOD
OF INCREASED ACTIVITY?
825
00:46:39,931 --> 00:46:43,366
- HAS BEEN SPEWING ASH AND SMOKE
12 MILES INTO THE AIR.
826
00:46:45,069 --> 00:46:46,969
narrator:
LOOKING BACK 100 YEARS,
827
00:46:47,038 --> 00:46:49,438
THE NUMBER OF VOLCANIC ERUPTIONS
EACH YEAR
828
00:46:49,507 --> 00:46:52,542
HAS ACTUALLY HELD STEADY.
829
00:46:52,610 --> 00:46:56,078
- IN GENERAL, THE PUBLIC ONLY
HEARS ABOUT VOLCANIC ERUPTIONS
830
00:46:56,147 --> 00:47:00,383
WHEN THEY'RE PARTICULARLY BIG,
WHEN THEY KILL PEOPLE,
831
00:47:00,451 --> 00:47:04,654
BUT, IN FACT, THERE ARE USUALLY
COUPLE DOZEN VOLCANIC ERUPTIONS
832
00:47:04,722 --> 00:47:07,557
GOING ON EVERY MONTH.
833
00:47:07,625 --> 00:47:11,527
AND SOME VOLCANOES HAVE BEEN
ERUPTING FOR DOZENS OF YEARS,
834
00:47:11,596 --> 00:47:13,196
LIKE KILAUEA--
835
00:47:13,264 --> 00:47:17,466
OR EVEN HUNDREDS
OR THOUSANDS OF YEARS
836
00:47:17,535 --> 00:47:20,503
LIKE AETNA IN ITALY.
837
00:47:20,572 --> 00:47:22,705
SO THERE IS A LOT OF VARIATION
838
00:47:22,774 --> 00:47:27,210
IN TERMS OF SOMETIMES WE HAVE
REALLY BIG VOLCANIC ERUPTIONS,
839
00:47:27,278 --> 00:47:32,281
AND THEN WE MIGHT GO FOR MONTHS
OR YEARS WITHOUT ONE OF THOSE.
840
00:47:32,350 --> 00:47:34,417
BUT, IN FACT,
VOLCANOES ARE ERUPTING
841
00:47:34,485 --> 00:47:36,485
AROUND THE EARTH ALL THE TIME.
842
00:47:42,160 --> 00:47:45,127
narrator: A SIMILAR SCENARIO
HOLDS FOR EARTHQUAKES.
843
00:47:49,167 --> 00:47:52,201
THE NUMBER OF BIG QUAKES
GREATER THAN MAGNITUDE 7
844
00:47:52,270 --> 00:47:54,036
AVERAGES 18 PER YEAR.
845
00:47:54,105 --> 00:47:56,205
- AT LEAST 250 PEOPLE HAVE DIED
846
00:47:56,274 --> 00:47:59,075
AFTER A MAJOR EARTHQUAKE
HIT SOUTHWESTERN PAKISTAN.
847
00:47:59,143 --> 00:48:00,309
narrator:
ONE OF THESE QUAKES
848
00:48:00,378 --> 00:48:02,945
IS HIGHER THAN MAGNITUDE 8
EACH YEAR.
849
00:48:05,116 --> 00:48:10,620
THIS NUMBER HAS HELD STEADY
SINCE THE YEAR 1900.
850
00:48:10,688 --> 00:48:13,589
BUT IT MAY SEEM THAT EARTHQUAKES
HAVE BECOME MORE FREQUENT
851
00:48:13,658 --> 00:48:15,124
FOR SEVERAL REASONS.
852
00:48:15,193 --> 00:48:16,525
- YO!
853
00:48:16,594 --> 00:48:17,994
EXCUSE ME!
854
00:48:18,062 --> 00:48:21,931
narrator: FIRST, MORE ARE BEING
RECORDED AND PINPOINTED.
855
00:48:22,000 --> 00:48:26,936
MORE THAN 8,000 STATIONS
LISTEN FOR QUAKES WORLDWIDE.
856
00:48:27,005 --> 00:48:32,441
IN 1931,
THERE WERE JUST 350.
857
00:48:32,510 --> 00:48:34,577
EARTHQUAKES ALSO SEEM
MORE NUMEROUS
858
00:48:34,646 --> 00:48:36,612
BECAUSE OF THE SOARING
POPULATION
859
00:48:36,681 --> 00:48:40,116
AND NEAR-INSTANT REPORTING
OF NEWS WORLDWIDE.
860
00:48:43,321 --> 00:48:48,157
- THE EARTHQUAKE THAT KILLED
1/4 MILLION PEOPLE IN HAITI
861
00:48:48,226 --> 00:48:51,827
WOULD ONLY HAVE KILLED
1/10 THAT NUMBER 100 YEARS AGO,
862
00:48:51,896 --> 00:48:53,329
AND WE WOULDN'T HAVE KNOWN
ABOUT IT.
863
00:48:53,398 --> 00:48:55,865
- THIS IS SOME OF WHAT I SAW
ON THE STREETS.
864
00:48:55,934 --> 00:48:57,867
- NOW WE HEAR
ABOUT THESE THINGS INSTANTLY.
865
00:48:57,936 --> 00:49:00,469
WE HAVE THE LIVE FOOTAGE
OF THE TSUNAMIS
866
00:49:00,538 --> 00:49:02,471
ARRIVING ON THE JAPANESE COAST,
867
00:49:02,540 --> 00:49:03,906
AND THE WHOLE WORLD
KNOWS ABOUT IT.
868
00:49:07,278 --> 00:49:09,745
narrator: THE RECORDED NUMBER
OF TSUNAMIS HAS INCREASED
869
00:49:09,814 --> 00:49:11,914
IN THE PAST 100 YEARS,
870
00:49:11,983 --> 00:49:17,320
BUT SCIENTISTS ATTRIBUTE THIS
TO EVER-IMPROVING DETECTION.
871
00:49:17,388 --> 00:49:19,956
AND WITH BETTER WARNING SYSTEMS
BEING INSTALLED,
872
00:49:20,024 --> 00:49:24,260
THE LOSS OF LIFE IS DECREASING.
873
00:49:24,329 --> 00:49:26,729
SO DO SCIENTISTS SEE AN UPTICK
874
00:49:26,798 --> 00:49:29,265
IN INCREASED
GEOLOGICAL ACTIVITY?
875
00:49:32,170 --> 00:49:34,337
- NO, THE EARTH'S DOING
THE SAME THING
876
00:49:34,405 --> 00:49:36,572
IT'S BEEN DOING FOR BILLIONS
OF YEARS.
877
00:49:36,641 --> 00:49:38,708
WE NOTICE THE EVENTS MORE
878
00:49:38,776 --> 00:49:41,610
BECAUSE OUR MORE COMPLEX SOCIETY
879
00:49:41,679 --> 00:49:45,614
AND OUR FAR MORE
POPULATED PLANET
880
00:49:45,683 --> 00:49:48,084
ARE MUCH MORE VULNERABLE
TO THESE DISASTERS.
881
00:49:48,152 --> 00:49:51,120
[rumbling]
882
00:49:51,189 --> 00:49:53,489
THERE'S NO REAL EVIDENCE THAT
WE'RE LIVING THROUGH A PERIOD
883
00:49:53,558 --> 00:49:54,957
OF ENHANCED ACTIVITY.
884
00:49:55,026 --> 00:49:56,592
IN ANY ONE AREA,
885
00:49:56,661 --> 00:50:01,397
THERE MAY BE REGIONS WHERE
WE HAVE A FEW MORE EARTHQUAKES
886
00:50:01,466 --> 00:50:05,401
FOR A FEW HUNDRED YEARS,
AND THEN AFTER THAT CLUSTERING,
887
00:50:05,470 --> 00:50:07,603
SEISMICITY WILL DIE AWAY.
888
00:50:07,672 --> 00:50:10,473
BUT ON A PLANET-WIDE SCALE,
THERE'S NO EVIDENCE FOR THAT.
889
00:50:13,711 --> 00:50:16,712
narrator: LOOKING DEEPER
INTO EARTH'S GEOLOGIC PAST,
890
00:50:16,781 --> 00:50:18,614
FAR BIGGER UPHEAVALS
HAVE OCCURRED
891
00:50:18,683 --> 00:50:21,951
THAN ANYTHING KNOWN BY HUMANS.
892
00:50:22,020 --> 00:50:24,987
A SUPERVOLCANO
THOUSANDS OF TIMES BIGGER
893
00:50:25,056 --> 00:50:28,157
THAN THE HUGE MOUNT SAINT HELENS
ERUPTION OF 1980
894
00:50:28,226 --> 00:50:32,294
WENT OFF AT YELLOWSTONE
640,000 YEARS AGO.
895
00:50:34,365 --> 00:50:38,834
SUPERVOLCANOES ARE EXCEEDINGLY
RARE IN HUMAN TERMS.
896
00:50:38,903 --> 00:50:41,670
NONE HAVE ERUPTED
FOR 26,000 YEARS.
897
00:50:45,109 --> 00:50:48,778
EARTH'S HISTORY BOOK CHRONICLES
OTHER MASSIVE UPHEAVALS
898
00:50:48,846 --> 00:50:52,448
LIKE THE SIBERIAN TRAPS.
899
00:50:52,517 --> 00:50:57,053
THERE WAS SNOWBALL EARTH,
WHEN THE WHOLE WORLD FROZE OVER.
900
00:50:57,121 --> 00:50:58,854
IN MORE RECENT TIMES,
901
00:50:58,923 --> 00:51:01,924
OUR DISTANT ANCESTORS
EXPERIENCED THE BITTER COLD
902
00:51:01,993 --> 00:51:03,893
OF THE ICE AGES,
903
00:51:03,961 --> 00:51:07,296
WHEN CHICAGO LAY
UNDER A MILE-THICK SHEET OF ICE.
904
00:51:09,767 --> 00:51:13,569
IF PLANET EARTH WERE ACTING UP
MORE THAN USUAL RIGHT NOW,
905
00:51:13,638 --> 00:51:15,104
IT WOULD BARELY REGISTER
906
00:51:15,173 --> 00:51:17,606
IN THE ANNALS
OF MAJOR EARTHLY EVENTS.
907
00:51:19,243 --> 00:51:21,577
THE EXCEPTION IS THE CLIMATE,
908
00:51:21,646 --> 00:51:24,447
WHICH IS CHANGING IN WAYS
NEVER BEFORE SEEN
909
00:51:24,515 --> 00:51:27,283
IN THE GEOLOGIC RECORD.
910
00:51:27,351 --> 00:51:30,986
PEOPLE MAY HAVE SOME INFLUENCE
OVER THIS PROCESS,
911
00:51:31,055 --> 00:51:32,955
BUT DEEP EARTH PROCESSES
912
00:51:33,024 --> 00:51:35,825
LIKE EARTHQUAKES
AND VOLCANIC ERUPTIONS
913
00:51:35,893 --> 00:51:39,862
ARE BEYOND ANYONE'S CONTROL.
914
00:51:39,931 --> 00:51:41,564
SO SCIENTISTS ARE FOCUSING ON
915
00:51:41,632 --> 00:51:44,266
WAYS TO LIVE
WITH THESE POWERFUL FORCES
916
00:51:44,335 --> 00:51:47,536
AND REDUCE THEIR THREATS.
917
00:51:47,605 --> 00:51:49,271
- THE PUBLIC WOULD LOVE IT
IF WE COULD PROVIDE
918
00:51:49,340 --> 00:51:51,807
SHORT-TERM PREDICTIONS
OF HOURS TO DAYS
919
00:51:51,876 --> 00:51:54,510
BEFORE AN EARTHQUAKE,
AND WE CAN'T DO THAT.
920
00:51:54,579 --> 00:51:58,647
BUT WHAT WE CAN DO IS PROVIDE
LONG-TERM ESTIMATES--
921
00:51:58,716 --> 00:52:00,716
DECADAL ESTIMATES, PERHAPS.
922
00:52:00,785 --> 00:52:03,652
THAT SHOULD BE IMPORTANT TO US,
TO OUR SOCIETY,
923
00:52:03,721 --> 00:52:05,354
TO PLAN FOR THESE EVENTS.
924
00:52:05,423 --> 00:52:07,456
[bell clanging]
925
00:52:07,525 --> 00:52:10,159
IN MY LIFETIME,
THERE'S A 3/4 CHANCE
926
00:52:10,228 --> 00:52:13,963
THERE WILL BE A MAJOR EARTHQUAKE
IN THE BAY AREA WHERE I LIVE,
927
00:52:14,031 --> 00:52:16,465
AND THAT SHOULD BE ENOUGH
TO ENCOURAGE ME
928
00:52:16,534 --> 00:52:18,801
TO PLAN WISELY
FOR THAT EARTHQUAKE
929
00:52:18,870 --> 00:52:20,669
THAT I NEED TO EXPECT.
930
00:52:26,477 --> 00:52:29,512
narrator: WITH EARTHQUAKE
PREDICTIONS STILL IN THE FUTURE,
931
00:52:29,580 --> 00:52:31,514
EARTHQUAKE-PRONE JAPAN
HAS DEVELOPED
932
00:52:31,582 --> 00:52:36,252
THE WORLD'S FIRST EARTHQUAKE AND
TSUNAMI EARLY WARNING SYSTEM.
933
00:52:36,320 --> 00:52:40,890
ITS FIRST MAJOR TEST CAME WITH
THE MASSIVE EARTHQUAKE IN 2011.
934
00:52:40,958 --> 00:52:43,025
[alarm buzzing]
935
00:52:43,094 --> 00:52:45,194
RESIDENTS OF TOKYO WERE WARNED
936
00:52:45,263 --> 00:52:47,963
EIGHT TO NINE SECONDS
BEFORE THE QUAKE HIT.
937
00:52:48,032 --> 00:52:50,366
- AT 2:46 IN THE AFTERNOON.
938
00:52:50,434 --> 00:52:52,935
THE SHAKING WENT ON
FOR MORE THAN 2 MINUTES.
939
00:52:53,004 --> 00:52:54,603
- THE CLOSEST MAJOR CITY,
SENDAI...
940
00:52:54,672 --> 00:52:57,673
narrator: RESIDENTS OF THE
NEAREST COASTAL CITY OF SENDAI
941
00:52:57,742 --> 00:53:00,342
HEARD TSUNAMI WARNINGS
EIGHT MINUTES BEFORE
942
00:53:00,411 --> 00:53:02,678
THE 33-FOOT TSUNAMI CAME ASHORE.
943
00:53:05,750 --> 00:53:07,850
JAPAN'S ADVANCED STATE
OF PREPAREDNESS
944
00:53:07,919 --> 00:53:11,187
AND STRONG BUILDING CODES
WERE THE CRITICAL FACTORS
945
00:53:11,255 --> 00:53:15,558
IN SAVING COUNTLESS LIVES
DURING THIS DISASTER.
946
00:53:15,626 --> 00:53:17,026
AND THE EARLY WARNING SYSTEM
947
00:53:17,094 --> 00:53:21,130
SAVED AN UNTOLD NUMBER
OF LIVES AS WELL.
948
00:53:21,199 --> 00:53:22,031
[phone rings]
949
00:53:24,101 --> 00:53:27,636
THE JAPAN METEOROLOGICAL
AGENCIES EARLY WARNING SYSTEM
950
00:53:27,705 --> 00:53:31,173
ALSO DOUBLES AS JAPAN'S VOLCANIC
ERUPTION WARNING SYSTEM.
951
00:53:33,277 --> 00:53:37,179
ERUPTIONS ARE EASIER TO PREDICT
THAN EARTHQUAKES.
952
00:53:37,248 --> 00:53:40,049
- WE ARE GETTING BETTER
ALL THE TIME
953
00:53:40,117 --> 00:53:42,017
AT PREDICTING
VOLCANIC ERUPTIONS,
954
00:53:42,086 --> 00:53:45,821
BUT IT'S BY NO MEANS PERFECT.
955
00:53:45,890 --> 00:53:50,259
AND IT'S STILL A VERY DIFFICULT
THING TO DO.
956
00:53:50,328 --> 00:53:52,761
WE HAVE MUCH BETTER
INSTRUMENTATION.
957
00:53:52,830 --> 00:53:56,298
WE CAN MEASURE THE INFLATION
OF THE GROUND.
958
00:53:56,367 --> 00:53:59,802
SEISMOGRAPHS SEE HOW MAGMA
IS MOVING UP.
959
00:53:59,870 --> 00:54:04,039
EVEN TEMPERATURES OF FUMAROLES,
CHANGES IN THE GASES.
960
00:54:04,108 --> 00:54:06,342
SO WE ARE GETTING BETTER
ALL THE TIME.
961
00:54:15,086 --> 00:54:17,586
narrator: MEANWHILE EARTH'S
INNER AND OUTER FORCES
962
00:54:17,655 --> 00:54:21,323
WILL KEEP REWORKING THE PLANET,
963
00:54:21,392 --> 00:54:24,226
FROM THE CENTER
OF THE INNER CORE
964
00:54:24,295 --> 00:54:27,796
TO THE HIGHEST PEAKS
ON THE SURFACE.
965
00:54:27,865 --> 00:54:30,332
NO OTHER PLANET KNOWN TO US
966
00:54:30,401 --> 00:54:34,703
HAS SO MANY DIFFERENT
NATURAL FORCES AT WORK.
967
00:54:34,772 --> 00:54:36,538
THE EARTH WE SEE TODAY
968
00:54:36,607 --> 00:54:40,342
HAS BEEN 4 1/2 BILLION YEARS
IN THE MAKING
969
00:54:40,411 --> 00:54:44,246
AND HAS NEVER LOOKED
QUITE THIS WAY BEFORE,
970
00:54:44,315 --> 00:54:48,851
AND IT WILL NEVER LOOK
THE SAME AGAIN.
971
00:54:48,919 --> 00:54:52,054
- I THINK THE WAY THE EARTH
LOOKS NOW AS A PLANET
972
00:54:52,123 --> 00:54:55,524
IS UNIQUE IN HISTORY,
973
00:54:55,593 --> 00:54:58,227
AS IS ALMOST EVERY PERIOD
IN GEOLOGIC HISTORY.
974
00:54:58,296 --> 00:55:01,297
THE EARTH IS CONSTANTLY
UNDERGOING CHANGE.
975
00:55:01,365 --> 00:55:02,364
- WHAT ARE THE GREENS?
976
00:55:02,433 --> 00:55:03,632
- THE GREENS ARE COUNTRY ROADS,
977
00:55:03,701 --> 00:55:05,200
AND THE YELLOWS ARE LOCAL ROADS.
978
00:55:05,269 --> 00:55:07,336
- FROM A GEOLOGIST'S
POINT OF VIEW,
979
00:55:07,405 --> 00:55:10,439
THE EARTH IS REALLY,
REALLY INTERESTING
980
00:55:10,508 --> 00:55:15,477
BECAUSE, ON EARTH,
WE SEE ALL THE MAJOR PROCESSES
981
00:55:15,546 --> 00:55:20,316
THAT FORM THE SURFACE
OF A PLANET ACTUALLY GOING ON.
982
00:55:20,384 --> 00:55:23,419
WE HAVE VOLCANISM.
983
00:55:23,487 --> 00:55:27,456
WE HAVE IMPACT CRATERS FORMED
NOT THAT LONG AGO.
984
00:55:27,525 --> 00:55:29,458
WE HAVE AN ATMOSPHERE,
985
00:55:29,527 --> 00:55:33,429
WHICH MEANS WE HAVE
LIQUID WATER.
986
00:55:33,497 --> 00:55:37,032
WE HAVE WIND.
WE HAVE EROSION.
987
00:55:37,101 --> 00:55:39,401
WE HAVE PLATE TECTONICS ON EARTH
988
00:55:39,470 --> 00:55:43,505
WHICH APPEARS TO BE UNIQUE
IN THE SOLAR SYSTEM.
989
00:55:43,574 --> 00:55:48,744
SO IT'S VERY GEOLOGICALLY
DIVERSE AND VERY DYNAMIC.
990
00:55:48,813 --> 00:55:51,347
SO I THINK WE ARE LUCKY,
ACTUALLY, TO LIVE HERE.
991
00:55:58,289 --> 00:56:01,290
[jangly guitar music]
992
00:56:01,359 --> 00:56:09,131
¶ ¶
85547
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