Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated:
1
00:00:11,230 --> 00:00:12,430
male narrator:
EARTH...
2
00:00:12,500 --> 00:00:14,600
THE ONLY PLANET ORBITING THE SUN
3
00:00:14,670 --> 00:00:16,670
THAT HAS CONTINENTS,
4
00:00:16,740 --> 00:00:18,410
OCEANS,
5
00:00:18,480 --> 00:00:20,040
PLATE TECTONICS,
6
00:00:20,110 --> 00:00:22,580
AND THE SOLE PLANET
WITH AN ATMOSPHERE
7
00:00:22,650 --> 00:00:26,950
THAT HAS SUSTAINED LIFE
FOR BILLIONS OF YEARS.
8
00:00:27,020 --> 00:00:29,280
HOW DID EARTH GET THIS WAY?
9
00:00:29,350 --> 00:00:32,550
WHAT'S BEHIND THE POWER,
THE VIOLENCE
10
00:00:32,620 --> 00:00:35,320
THAT CRACKS SOLID ROCK
IN AN INSTANT,
11
00:00:35,390 --> 00:00:37,830
THAT SHATTERS BUILDINGS
12
00:00:37,890 --> 00:00:40,900
AND SENDS TSUNAMIS
RACING FOR THE SHORE,
13
00:00:40,960 --> 00:00:46,000
THAT ERUPTS SEAS OF LAVA
AND BILLOWING CLOUDS OF ASH?
14
00:00:48,710 --> 00:00:51,040
EARTH HAS BEEN
MAKING HEADLINES LATELY.
15
00:00:51,110 --> 00:00:54,610
- POWERFUL IMAGES OF DESTRUCTION
NEVER SEEN IN OUR LIFETIME.
16
00:00:54,680 --> 00:00:56,380
narrator:
PEOPLE ARE ASKING,
17
00:00:56,450 --> 00:01:01,820
"HAS EARTH ENTERED A PERIOD
OF INTENSE GEOLOGIC UPHEAVAL?"
18
00:01:01,890 --> 00:01:05,490
SCIENTISTS HAVE NEW ANSWERS
TO QUESTIONS ABOUT OUR HOME,
19
00:01:05,560 --> 00:01:08,860
THE THIRD PLANET FROM THE SUN.
20
00:01:08,930 --> 00:01:11,530
IT'S A STORY THAT,
JUST A FEW DECADES AGO,
21
00:01:11,590 --> 00:01:13,960
COULD NOT HAVE BEEN TOLD.
22
00:01:23,610 --> 00:01:25,070
ABOUT 10 BILLION YEARS
23
00:01:25,140 --> 00:01:27,840
AFTER THE BIG BANG
CREATED THE UNIVERSE,
24
00:01:27,910 --> 00:01:32,150
OUR SOLAR SYSTEM BEGAN TO FORM.
25
00:01:32,220 --> 00:01:34,650
SCIENTISTS CALCULATE
THAT THIS HAPPENED
26
00:01:34,720 --> 00:01:39,250
4.567 BILLION YEARS AGO,
27
00:01:39,320 --> 00:01:43,990
AND THAT WAS WHEN PLANET EARTH
WAS CREATED.
28
00:01:44,060 --> 00:01:48,100
- A LONG TIME AGO,
ABOUT 4 1/2 BILLION YEARS AGO,
29
00:01:48,160 --> 00:01:52,200
THE EARTH FORMED
FROM THIS NEBULA AROUND THE SUN.
30
00:01:52,270 --> 00:01:56,400
THE SUN IN THE CENTER,
AND THE NEBULA SWIRLING AROUND,
31
00:01:56,470 --> 00:02:00,010
AND THE BITS
OF THE NEBULA ACCRETING,
32
00:02:00,080 --> 00:02:03,380
THAT IS, STICKING TOGETHER
AND COLLIDING WITH EACH OTHER,
33
00:02:03,450 --> 00:02:07,350
AND IT WAS
A VERY TURBULENT TIME.
34
00:02:07,420 --> 00:02:10,490
[explosion]
35
00:02:10,550 --> 00:02:13,960
AND THE EARTH
GRADUALLY CAME TOGETHER,
36
00:02:14,020 --> 00:02:16,090
AND AS IT BECAME MORE MASSIVE,
37
00:02:16,160 --> 00:02:18,960
THE GRAVITATIONAL FORCE
BECAME LARGER,
38
00:02:19,030 --> 00:02:22,560
AND IT COULD ATTRACT
MORE OF THE SMALL PIECES,
39
00:02:22,630 --> 00:02:25,470
AND THE EARTH GREW AND GREW.
40
00:02:28,140 --> 00:02:30,200
narrator:
IT TOOK ABOUT 100 MILLION YEARS
41
00:02:30,270 --> 00:02:33,770
FOR EARTH TO REACH
ITS PRESENT SIZE,
42
00:02:33,840 --> 00:02:35,310
BUT BEFORE IT DID,
43
00:02:35,380 --> 00:02:40,780
OUR PLANET EXPERIENCED ITS
LARGEST, MOST DRAMATIC EVENT.
44
00:02:40,850 --> 00:02:42,720
- SO AFTER
THE EARLY EARTH FORMED,
45
00:02:42,790 --> 00:02:44,620
PROBABLY TENS OF MILLIONS
OF YEARS AFTERWARDS,
46
00:02:44,690 --> 00:02:47,560
YOU HAD A MARS-SIZED OBJECT
THAT ACTUALLY HIT THE EARTH.
47
00:02:50,290 --> 00:02:53,430
[explosion]
48
00:02:53,500 --> 00:02:56,500
narrator: THE GIANT PLANETOID
IMPACTOR WAS CALLED THEIA.
49
00:02:58,940 --> 00:03:01,570
- THE MARS-SIZED IMPACTOR
HIT THE EARTH,
50
00:03:01,640 --> 00:03:04,310
AND IT SPEWED OFF A LOT
OF THE MATERIAL FROM THE EARTH,
51
00:03:04,370 --> 00:03:06,010
AND PART OF THAT
FORMED THE SMALL--
52
00:03:06,080 --> 00:03:07,880
THE MOON THAT WE NOW HAVE.
53
00:03:07,940 --> 00:03:10,480
AND ALSO WE GENERATED A LOT
OF HEAT FROM THIS IMPACT,
54
00:03:10,550 --> 00:03:13,710
AND SO IT MIGHT HAVE REMELTED
A LOT OF THE EARLY EARTH.
55
00:03:16,750 --> 00:03:18,390
narrator:
SCIENTISTS ONLY RECENTLY LEARNED
56
00:03:18,450 --> 00:03:20,120
OF THIS MASSIVE IMPACT
57
00:03:20,190 --> 00:03:23,560
BY STUDYING ROCKS
COLLECTED ON THE MOON.
58
00:03:23,630 --> 00:03:26,130
IT TURNED OUT THAT
THE MOON ROCKS WERE VERY SIMILAR
59
00:03:26,200 --> 00:03:29,730
IN COMPOSITION TO EARTH ROCKS.
60
00:03:29,800 --> 00:03:33,130
AFTER THE IMPACT,
THE MOON BECAME A SATELLITE,
61
00:03:33,200 --> 00:03:36,740
WHILE THE EARTH WAS LEFT
A MOLTEN BALL OF FIRE.
62
00:03:38,410 --> 00:03:41,940
- AND SO THE EARLY EARTH
WAS, LIKE, THIS MOLTEN MASS.
63
00:03:42,010 --> 00:03:46,580
THAT MUST HAVE LOOKED
LIKED MAYBE ONE GIANT VOLCANO
64
00:03:46,650 --> 00:03:47,950
OR LAVA LAKE.
65
00:03:50,220 --> 00:03:53,720
IT SLOWLY SOLIDIFIED
AND FORMED THIS OUTER CRUST
66
00:03:53,790 --> 00:03:56,590
THAT IS WHERE WE STAND TODAY.
67
00:03:58,360 --> 00:04:00,230
narrator:
AS THE CRUST FORMED,
68
00:04:00,300 --> 00:04:03,130
COLLISIONS AND BOMBARDMENTS
DIED DOWN,
69
00:04:03,200 --> 00:04:06,500
BUT THE METEORITES
CONTINUE TO FALL TO THIS DAY.
70
00:04:06,570 --> 00:04:08,740
- WE START WITH SOME
BREAKING NEWS THIS HOUR.
71
00:04:08,810 --> 00:04:10,670
PEOPLE IN THE URALS IN RUSSIA
72
00:04:10,740 --> 00:04:13,610
HAVE SEEN BURNING OBJECTS
RAINING DOWN FROM THE SKY
73
00:04:13,680 --> 00:04:16,110
AFTER A METEORITE EXPLODED
ABOVE THE EARTH,
74
00:04:16,180 --> 00:04:18,050
CAUSING A METEOR SHOWER.
75
00:04:18,110 --> 00:04:20,980
EYEWITNESSES REPORTED
SEVERAL BLASTS.
76
00:04:21,050 --> 00:04:23,820
[glass shattering]
77
00:04:23,890 --> 00:04:27,690
narrator: DESPITE THE SHOCK
THAT A METEOR SHOWER CAN CAUSE,
78
00:04:27,760 --> 00:04:30,930
METEORITES ARE
EXTREMELY VALUABLE TO SCIENTISTS
79
00:04:30,990 --> 00:04:34,460
WHO STUDY WHEN THE EARTH
WAS CREATED.
80
00:04:34,530 --> 00:04:38,170
THEY ARE COLLECTED
AND STUDIED WORLDWIDE.
81
00:04:38,230 --> 00:04:40,670
BUT THE BEST PLACE
TO FIND THESE ROCKY ALIENS
82
00:04:40,740 --> 00:04:45,440
IS ONE OF THE EARTH'S
MOST UNEARTHLY PLACES:
83
00:04:45,510 --> 00:04:46,570
ANTARCTICA.
84
00:04:49,610 --> 00:04:51,450
ON THE SLEEK, BLUE ICE EXPANSE
85
00:04:51,510 --> 00:04:54,020
OF THE CENTRAL ANTARCTIC
ICE SHEET,
86
00:04:54,080 --> 00:04:58,320
THE SURFACE IS SWEPT CLEAN
BY RELENTLESS WINDS.
87
00:04:58,390 --> 00:05:02,690
A METEORITE SITS EXPOSED
FOR AN AVERAGE OF 20,000 YEARS,
88
00:05:02,760 --> 00:05:05,360
SOMETIMES
FOR SEVERAL MILLION YEARS,
89
00:05:05,430 --> 00:05:09,130
BEFORE SCIENTISTS MIGHT SPOT IT
AND COLLECT IT.
90
00:05:11,000 --> 00:05:13,300
A TYPE OF METEORITE
CALLED A CHONDRITE
91
00:05:13,370 --> 00:05:15,370
CONTAINS THE SAME BASIC ELEMENTS
92
00:05:15,440 --> 00:05:18,140
THAT MAKE UP THE SUN
AND PLANETS,
93
00:05:18,210 --> 00:05:20,210
SO THEY TELL US A GREAT DEAL
94
00:05:20,280 --> 00:05:22,840
ABOUT WHERE
WE ORIGINALLY CAME FROM
95
00:05:22,910 --> 00:05:26,080
AND WHEN.
96
00:05:26,150 --> 00:05:28,980
TO FIGURE OUT HOW OLD
METEORITES AND THE EARTH
97
00:05:29,050 --> 00:05:30,720
ACTUALLY ARE,
98
00:05:30,790 --> 00:05:33,520
SCIENTISTS USE
HIGH-PRECISION INSTRUMENTS
99
00:05:33,590 --> 00:05:36,560
TO MEASURE
THEIR RADIOACTIVE PROPERTIES.
100
00:05:36,630 --> 00:05:39,790
BUT WHY MUST SCIENTISTS
RELY ON METEORITES
101
00:05:39,860 --> 00:05:43,260
TO FIGURE OUT HOW OLD
THE EARTH REALLY IS?
102
00:05:43,330 --> 00:05:46,630
WHY DON'T THEY SIMPLY STUDY
THE OLDEST ROCKS
103
00:05:46,700 --> 00:05:49,070
THAT WERE FORMED
ON THE EARTH ITSELF?
104
00:05:51,270 --> 00:05:54,310
- FROM THE EARTH'S FORMATION
AROUND 4.6 BILLION YEARS AGO
105
00:05:54,380 --> 00:05:56,280
UP TO ABOUT
3.8 BILLION YEARS AGO,
106
00:05:56,350 --> 00:05:58,450
IS AN ERA CALLED THE HADEAN,
107
00:05:58,510 --> 00:06:01,750
WHEN THE EARTH WAS UNDERGOING
HEAVY BOMBARDMENT,
108
00:06:01,820 --> 00:06:04,020
AND THERE'S
VIRTUALLY NO ROCK RECORD
109
00:06:04,090 --> 00:06:08,620
FROM THAT PERIOD OF TIME AT ALL
ON THE EARTH REMAINING TODAY.
110
00:06:12,360 --> 00:06:14,100
narrator:
THE HADEAN ERA,
111
00:06:14,160 --> 00:06:18,030
GREEK FOR UNDERWORLD,
OR HELL.
112
00:06:18,100 --> 00:06:20,370
NOTHING SURVIVED THIS INFERNO...
113
00:06:20,440 --> 00:06:22,000
OR DID IT?
114
00:06:22,070 --> 00:06:25,340
IT WAS A MISSING LINK HUNDREDS
OF MILLIONS OF YEARS LONG
115
00:06:25,410 --> 00:06:28,510
BETWEEN EARTH'S CREATION
AND ITS OLDEST ROCKS,
116
00:06:28,580 --> 00:06:33,110
LIKE THESE 3.6 BILLION-YEAR-OLD
ROCKS FOUND IN AUSTRALIA.
117
00:06:33,180 --> 00:06:34,010
- BEAUTIFUL.
118
00:06:35,990 --> 00:06:38,250
narrator: BUT BREAKTHROUGHS
IN ANALYZING THESE ROCKS
119
00:06:38,320 --> 00:06:43,360
FINALLY OPENED A WINDOW
INTO THE HADEAN.
120
00:06:43,430 --> 00:06:47,730
- INTERESTINGLY, WE DO HAVE
SOME MATERIALS FROM THAT TIME.
121
00:06:47,800 --> 00:06:52,900
THEY ARE SMALL ZIRCON GRAINS,
4.4 BILLION OR SO OF AGE.
122
00:06:55,510 --> 00:06:57,640
narrator: ZIRCONS ARE
THE OLDEST TERRESTRIAL MATERIAL
123
00:06:57,710 --> 00:07:00,880
EVER FOUND ON EARTH.
124
00:07:00,940 --> 00:07:04,950
BUT ROCKS CONTAINING ZIRCONS
THAT ARE BILLIONS OF YEARS OLD
125
00:07:05,010 --> 00:07:08,280
HAVE ONLY BEEN DISCOVERED
IN A HANDFUL OF PLACES ON EARTH,
126
00:07:08,350 --> 00:07:10,380
LIKE ANTARCTICA.
127
00:07:10,450 --> 00:07:14,820
THE REST HAVE BEEN OBLITERATED.
128
00:07:14,890 --> 00:07:18,730
STUDYING THOSE RARE VESTIGES
OF THE EARLY DAYS OF EARTH,
129
00:07:18,800 --> 00:07:21,530
SCIENTISTS WERE ASTONISHED
TO FIND EVIDENCE
130
00:07:21,600 --> 00:07:24,970
THAT VERY EARLY ON,
EARTH DEVELOPED A CHARACTERISTIC
131
00:07:25,030 --> 00:07:29,540
THAT IT AND NO OTHER PLANET
IN THE SOLAR SYSTEM POSSESSES:
132
00:07:29,610 --> 00:07:34,310
PLATE TECTONICS.
133
00:07:34,380 --> 00:07:36,280
- PLATE TECTONICS
HAS BEEN AROUND ON EARTH
134
00:07:36,350 --> 00:07:37,910
FROM THE EARLY DAYS,
135
00:07:37,980 --> 00:07:41,180
AT LEAST 2 1/2,
3 BILLION YEARS AGO.
136
00:07:41,250 --> 00:07:43,980
SO MORE THAN 3/4 OF THE LIFE
OF THE PLANET.
137
00:07:44,050 --> 00:07:48,060
narrator: MARS NEARLY DEVELOPED
PLATE TECTONICS,
138
00:07:48,120 --> 00:07:50,090
BUT FAILED.
139
00:07:50,160 --> 00:07:51,430
- MARS IS SMALLER THAN EARTH.
140
00:07:51,490 --> 00:07:52,890
IT COOLED FASTER.
141
00:07:52,960 --> 00:07:55,060
IT MAY WELL HAVE HAD A STYLE
OF PLATE TECTONICS
142
00:07:55,130 --> 00:08:00,000
EARLY IN ITS HISTORY,
BUT IT CLEARLY DOES NOT TODAY.
143
00:08:00,070 --> 00:08:02,900
narrator: VENUS, CONSIDERED
EARTH'S SISTER PLANET,
144
00:08:02,970 --> 00:08:07,010
IS ALSO MISSING EARTH'S TRAIT
OF PLATE TECTONICS.
145
00:08:07,080 --> 00:08:09,980
- VENUS DOESN'T HAVE
PLATE TECTONICS
146
00:08:10,050 --> 00:08:11,910
IN THE STYLE THAT WE RECOGNIZE
147
00:08:11,980 --> 00:08:14,980
WITH VERY CLEAR, LINEAR
BOUNDARIES BETWEEN RIGID PLATES,
148
00:08:15,050 --> 00:08:18,820
PERHAPS BECAUSE THERE'S NO WATER
ON THE SURFACE OF VENUS.
149
00:08:24,690 --> 00:08:26,290
narrator:
LIQUID WATER:
150
00:08:26,360 --> 00:08:29,460
IT IS THE STRIKING AND
DISTINGUISHING CHARACTERISTIC
151
00:08:29,530 --> 00:08:32,400
OF EARTH'S SURFACE,
152
00:08:32,470 --> 00:08:36,000
AND SCIENTISTS ARE FINDING
THAT THIS SUBSTANCE IS THE KEY
153
00:08:36,070 --> 00:08:38,210
THAT STARTED EARTH'S EARLY CRUST
154
00:08:38,270 --> 00:08:41,440
INTO CONSTANT,
EVER-CHANGING MOTION.
155
00:08:43,110 --> 00:08:45,780
- ONE OF THE REASONS
WE HAVE PLATE TECTONICS,
156
00:08:45,850 --> 00:08:47,410
WHICH WE DON'T SEE
ON ANY OTHER PLANETS,
157
00:08:47,480 --> 00:08:50,520
IS THAT WE HAVE
A LOT OF WATER ON THE EARTH.
158
00:08:50,590 --> 00:08:53,220
SO WE HAVE WATER
NOT ONLY IN THE OCEANS,
159
00:08:53,290 --> 00:08:55,720
BUT THERE'S APPROXIMATELY
AN OCEAN'S WORTH OF WATER
160
00:08:55,790 --> 00:08:58,960
LOCKED UP IN THE ROCKS IN, SAY,
THE UPPER 100 KILOMETERS
161
00:08:59,030 --> 00:08:59,860
OF THE EARTH.
162
00:09:02,000 --> 00:09:03,960
WHEN YOU PUT WATER INTO A ROCK,
163
00:09:04,030 --> 00:09:06,930
IT MAKES THE ROCK WEAKER
BY MAYBE A FACTOR OF 100
164
00:09:07,000 --> 00:09:11,340
THAN IT WOULD BE
WITHOUT THE WATER.
165
00:09:11,410 --> 00:09:13,310
WEAKER ROCKS
MAKE FOR PLATE TECTONICS
166
00:09:13,380 --> 00:09:15,840
BECAUSE YOU HAVE TO HAVE
PLATE BOUNDARIES
167
00:09:15,910 --> 00:09:17,980
WHERE ROCKS EITHER SLIDE
BY EACH OTHER,
168
00:09:18,050 --> 00:09:21,620
OR ONE GOES DOWN
UNDERNEATH THE OTHER.
169
00:09:21,680 --> 00:09:23,750
AND SO UNLESS YOU HAVE ROCKS
THAT ARE WEAK ENOUGH
170
00:09:23,820 --> 00:09:26,150
TO BE ABLE TO SLIDE
PAST EACH OTHER,
171
00:09:26,220 --> 00:09:27,920
YOU'RE NOT GONNA HAVE
PLATE TECTONICS.
172
00:09:34,000 --> 00:09:36,100
narrator: BUT WHERE
DID EARTH'S VAST AMOUNT
173
00:09:36,170 --> 00:09:39,570
OF LIQUID WATER COME FROM?
174
00:09:39,640 --> 00:09:42,670
- IN THE EARLY HISTORY
OF THE EARTH,
175
00:09:42,740 --> 00:09:45,510
WHEN THERE WAS A LOT
OF VOLCANISM GOING ON,
176
00:09:45,580 --> 00:09:49,580
VOLCANOES ACTUALLY
BROUGHT GASES UP
177
00:09:49,650 --> 00:09:52,980
THAT CREATED
THE EARLY ATMOSPHERE.
178
00:09:53,050 --> 00:09:58,020
AND MAGMA HAS WATER
IN THE FORM OF VAPOR
179
00:09:58,090 --> 00:09:59,790
THAT IT CAN BRING UP.
180
00:09:59,860 --> 00:10:02,690
[rumbling]
181
00:10:05,530 --> 00:10:07,290
narrator:
ICY METEORITES AND COMETS
182
00:10:07,360 --> 00:10:09,200
WERE THE OTHER LIKELY SOURCE
183
00:10:09,270 --> 00:10:11,700
THAT INFUSED EARTH'S CRUST
WITH WATER
184
00:10:11,770 --> 00:10:14,870
AND GOT IT MOVING.
185
00:10:14,940 --> 00:10:17,270
AND ONCE PLATE TECTONICS
STARTED,
186
00:10:17,340 --> 00:10:19,270
IT NEVER STOPPED.
187
00:10:19,340 --> 00:10:22,880
IT HAS INFLUENCED EVERYTHING
THAT HAS HAPPENED ON THE SURFACE
188
00:10:22,950 --> 00:10:24,210
INCLUDING LIFE.
189
00:10:28,250 --> 00:10:31,290
- THE OXYGEN, THE MINERALS,
EVERYTHING THAT WE GET
190
00:10:31,350 --> 00:10:33,150
COMES FROM THE INTERIOR
OF THE EARTH.
191
00:10:35,890 --> 00:10:38,460
WE ALL HAVE INTERNALLY WITHIN US
192
00:10:38,530 --> 00:10:41,200
A WHOLE SUITE OF MINERALS
AND THINGS THAT--
193
00:10:41,260 --> 00:10:42,500
WE'RE FROM THE EARTH.
194
00:10:42,570 --> 00:10:46,730
ESSENTIALLY, THAT'S WHERE WE--
195
00:10:46,800 --> 00:10:48,300
OUR CHEMICAL MAKEUP
IS FROM THE EARTH.
196
00:10:50,970 --> 00:10:54,810
AND IF YOU HAD NO WAY OF GETTING
THAT OUTSIDE OF THE EARTH,
197
00:10:54,880 --> 00:10:57,280
THEN ESSENTIALLY YOU'D HAVE
A DEAD PLANET.
198
00:11:01,180 --> 00:11:03,280
narrator: PLATE TECTONICS
BECAME RECOGNIZED
199
00:11:03,350 --> 00:11:05,620
AS BEING A CRUCIAL INGREDIENT
FOR LIFE,
200
00:11:05,690 --> 00:11:08,990
AS IS WATER.
201
00:11:09,060 --> 00:11:10,690
THIS WAS AN IMPORTANT PIECE
OF KNOWLEDGE
202
00:11:10,760 --> 00:11:15,630
FOR SCIENTISTS WHO WERE STUDYING
EARTH'S ANCIENT ROCKS.
203
00:11:15,700 --> 00:11:18,300
IF THE CONDITIONS FOR LIFE
WERE PRESENT
204
00:11:18,370 --> 00:11:22,870
WHEN EARTH'S ANCIENT ROCKS
FORMED BILLIONS OF YEARS AGO,
205
00:11:22,940 --> 00:11:25,840
THEN WASN'T IT POSSIBLE
THAT LIFE ALSO TOOK HOLD
206
00:11:25,910 --> 00:11:30,210
IN THE EARLY DAWN
OF EARTH'S FORMATION?
207
00:11:30,280 --> 00:11:32,110
THE SEARCH WAS ON.
208
00:11:34,720 --> 00:11:39,450
SOME SCIENTISTS ZEROED IN ON
THE 3.5 BILLION-YEAR-OLD ROCKS
209
00:11:39,520 --> 00:11:42,920
IN THE OUTBACK
OF WESTERN AUSTRALIA.
210
00:11:42,990 --> 00:11:47,360
- AMAZINGLY, IT TURNS OUT
THAT FAIRLY SOON AFTER,
211
00:11:47,430 --> 00:11:50,500
PEOPLE STARTED DISCOVERING
SOME POTENTIAL SIGNS OF LIFE
212
00:11:50,570 --> 00:11:51,870
IN THOSE ROCKS,
213
00:11:51,930 --> 00:11:54,400
AND ONE OF THE MAJOR DISCOVERIES
214
00:11:54,470 --> 00:11:55,970
WAS STRUCTURES
CALLED STROMATOLITES.
215
00:12:00,280 --> 00:12:02,910
narrator: STROMATOLITES
ARE PECULIAR ROCKY STRUCTURES
216
00:12:02,980 --> 00:12:05,280
BUILT BY COLONIES
OF CYANOBACTERIA,
217
00:12:05,350 --> 00:12:08,550
OR BLUE-GREEN ALGAE.
218
00:12:08,620 --> 00:12:11,020
THEY ARE EXTREMELY RARE
ON EARTH TODAY,
219
00:12:11,090 --> 00:12:13,250
GROWING IN ONLY A FEW PLACES,
220
00:12:13,320 --> 00:12:17,160
LIKE LAGUNA BACALAR IN MEXICO.
221
00:12:17,230 --> 00:12:20,730
BUT THEY WERE THE FIRST
LIFE FORMS TO APPEAR ON EARTH,
222
00:12:20,800 --> 00:12:23,700
AND THEY GAVE RISE
TO ALL OTHER FORMS OF LIFE,
223
00:12:23,770 --> 00:12:26,100
INCLUDING PEOPLE.
224
00:12:26,170 --> 00:12:28,940
IT TOOK AWHILE, THOUGH.
225
00:12:29,000 --> 00:12:31,210
- STROMATOLITES DOMINATE
THE FIRST 3 BILLION YEARS
226
00:12:31,270 --> 00:12:33,110
OF THE HISTORY OF LIFE ON EARTH.
227
00:12:33,180 --> 00:12:36,340
SO FROM 3 1/2 BILLION YEARS AGO
228
00:12:36,410 --> 00:12:37,850
TO UP TO ABOUT
1/2 A BILLION YEARS AGO,
229
00:12:37,910 --> 00:12:40,310
THE FOSSIL RECORD CONSISTS
230
00:12:40,380 --> 00:12:42,320
ALMOST ENTIRELY
OF STROMATOLITES.
231
00:12:46,060 --> 00:12:49,660
narrator: STROMATOLITES LIVED
IN OCEANS AND LAKES.
232
00:12:49,730 --> 00:12:52,590
FOR THAT PERIOD,
NO FOSSILS HAVE BEEN FOUND
233
00:12:52,660 --> 00:12:54,900
OF CREATURES THAT LIVED ON LAND.
234
00:12:54,960 --> 00:12:57,800
DOES THAT MEAN
THERE WERE NO CONTINENTS
235
00:12:57,870 --> 00:13:01,900
FOR THE FIRST 3 BILLION YEARS
OF EARTH'S HISTORY?
236
00:13:01,970 --> 00:13:03,370
ONCE AGAIN,
237
00:13:03,440 --> 00:13:08,240
EARTH'S ANCIENT ROCKS
YIELDED CLUES TO THIS MYSTERY.
238
00:13:08,310 --> 00:13:10,410
- WE DON'T KNOW FOR SURE
WHEN PLATE TECTONICS STARTED,
239
00:13:10,480 --> 00:13:15,580
BUT WE DO KNOW FOR SURE
WHEN WE FIRST HAD CONTINENTS.
240
00:13:15,650 --> 00:13:18,620
WE HAVE INTACT AREAS
THAT WE CAN GO AND MAP IN
241
00:13:18,690 --> 00:13:21,590
THAT GO BACK AS FAR
AS 4 BILLION YEARS.
242
00:13:21,660 --> 00:13:25,060
THAT'S NEARLY 90%
OF THE AGE OF THE EARTH,
243
00:13:25,130 --> 00:13:27,460
SO WE'RE QUITE SURE
ABOUT THE FACT
244
00:13:27,530 --> 00:13:29,460
THAT WE HAD CONTINENTS
BACK THAT FAR.
245
00:13:32,940 --> 00:13:34,940
narrator: NO ONE KNOWS
WHAT THE CONTINENTS WERE LIKE
246
00:13:35,000 --> 00:13:37,440
4 BILLION YEARS AGO
247
00:13:37,510 --> 00:13:39,540
OR WHY WE ENDED UP
WITH SEVEN CONTINENTS
248
00:13:39,610 --> 00:13:42,910
THAT RIDE AROUND
ON A DOZEN LARGE CRUSTAL PLATES
249
00:13:42,980 --> 00:13:46,750
AND MANY MICROPLATES IN BETWEEN.
250
00:13:46,820 --> 00:13:52,650
BUT THE QUESTION THAT PLAGUED
SCIENTISTS FOR YEARS WAS THIS:
251
00:13:52,720 --> 00:13:56,220
WHAT WAS THE PRIME FORCE
THAT MADE THE PLATES MOVE?
252
00:14:01,130 --> 00:14:03,930
THERE WERE
TWO CONTENDING FORCES.
253
00:14:04,000 --> 00:14:08,100
THE FIRST WAS DISCOVERED ABOARD
SEAFARING RESEARCH VESSELS
254
00:14:08,170 --> 00:14:12,440
MAPPING THE SEA FLOOR
DECADES AGO.
255
00:14:12,510 --> 00:14:14,410
SCIENTISTS LEARNED
THAT THE SEA FLOOR
256
00:14:14,480 --> 00:14:17,340
WAS SPREADING APART
IN THE MIDDLE OF THE OCEANS
257
00:14:17,410 --> 00:14:21,580
AT SUBMARINE MOUNTAIN RANGES
CALLED MID-OCEAN RIDGES.
258
00:14:21,650 --> 00:14:23,920
SUBMERSIBLES WERE SENT DOWN
259
00:14:23,990 --> 00:14:26,750
AND CAME BACK WITH FOOTAGE
OF HOT GASES WELLING UP
260
00:14:26,820 --> 00:14:29,790
IN THE RIFT ZONES.
261
00:14:29,860 --> 00:14:32,130
MAGMA WAS RISING
FROM BELOW HERE,
262
00:14:32,190 --> 00:14:34,130
AND IT WAS BELIEVED
THAT IT WAS PUSHING
263
00:14:34,200 --> 00:14:38,270
THE OCEANIC PLATES APART.
264
00:14:38,330 --> 00:14:42,800
THE KEY TO PLATE TECTONICS
WAS AT LAST DISCOVERED...
265
00:14:42,870 --> 00:14:46,270
OR WAS IT?
266
00:14:46,340 --> 00:14:50,010
SEISMIC EXPERIMENTS
OF EARTH'S DEEP CRUST AND MANTLE
267
00:14:50,080 --> 00:14:52,810
CHANGED SCIENTISTS' THINKING.
268
00:14:52,880 --> 00:14:55,580
A SECOND FORCE WAS DISCOVERED
269
00:14:55,650 --> 00:14:57,920
WHERE PLATES
COLLIDED HEAD-ON,
270
00:14:57,990 --> 00:15:01,620
AS THEY DO UNDER
THE ANDES MOUNTAINS OF ECUADOR.
271
00:15:01,690 --> 00:15:05,630
ONE PLATE WAS IMAGED DIVING
UNDERNEATH THE OTHER.
272
00:15:05,690 --> 00:15:09,230
THE WAS CALLED
A SUBDUCTION ZONE.
273
00:15:09,300 --> 00:15:11,900
THE SINKING SLAB
APPEARED TO BE PULLING
274
00:15:11,970 --> 00:15:13,870
THE REST OF THE PLATE BEHIND IT,
275
00:15:13,940 --> 00:15:17,300
MAKING THE ENTIRE PLATE MOVE.
276
00:15:17,370 --> 00:15:20,940
A GREAT DEBATE AROSE OVER
WHICH FORCE WAS MORE IMPORTANT
277
00:15:21,010 --> 00:15:23,910
IN DRIVING PLATE TECTONICS:
278
00:15:23,980 --> 00:15:29,820
PUSHING FROM THE RISING MAGMA
OR PULLING IN SUBDUCTION ZONES.
279
00:15:29,890 --> 00:15:33,820
THERE NOW APPEARS
TO BE A WINNER.
280
00:15:33,890 --> 00:15:37,160
- WHEN PEOPLE FIRST RECOGNIZED
MID-OCEAN RIDGE SPREADING
281
00:15:37,230 --> 00:15:39,760
AS THE KEY TO UNDERSTANDING
PLATE TECTONICS,
282
00:15:39,830 --> 00:15:44,200
THE VIEW WAS THAT THE MAGMA,
THE MANTLE,
283
00:15:44,270 --> 00:15:48,270
ROSE UP IN THE CENTER
AND FORCED THE PLATES APART.
284
00:15:48,340 --> 00:15:50,640
BUT THAT VIEW
HAS CHANGED OVER THE YEARS
285
00:15:50,710 --> 00:15:54,340
AND HAS LARGELY BEEN REPLACED
BY THE VIEW THAT IT'S THE PULL
286
00:15:54,410 --> 00:15:57,210
OF THE SUBDUCTION SLAB
THAT MATTERS MOST.
287
00:15:57,280 --> 00:16:00,850
- BOB, CAN YOU PLEASE HAND ME
THE PVC PIPE, PLEASE?
288
00:16:00,920 --> 00:16:03,250
- SURE.
289
00:16:03,320 --> 00:16:06,090
narrator: SO SCIENTISTS
LOOKED HARDER AT SUBDUCTION,
290
00:16:06,160 --> 00:16:12,160
AND AS THEY DID, MORE GEOLOGIC
WONDERS WERE UNCOVERED.
291
00:16:12,230 --> 00:16:16,000
FOR ONE, SEISMIC STUDIES
OF SUBDUCTION ZONES
292
00:16:16,070 --> 00:16:18,570
REVEALED THAT OCEANIC PLATES
ARE VERY THIN
293
00:16:18,630 --> 00:16:21,230
COMPARED TO CONTINENTS.
294
00:16:21,300 --> 00:16:24,810
THE SEA FLOOR
IS 3 TO 6 MILES THICK,
295
00:16:24,870 --> 00:16:27,710
WHILE CONTINENTS AVERAGE
30 MILES THICK
296
00:16:27,780 --> 00:16:32,510
AND SWELL UP TO 50 MILES
UNDER GREAT MOUNTAIN BELTS.
297
00:16:32,580 --> 00:16:34,580
THIS HAS A MAJOR INFLUENCE
298
00:16:34,650 --> 00:16:37,150
ON HOW THE PLATES
AFFECT EACH OTHER,
299
00:16:37,220 --> 00:16:40,290
ESPECIALLY IN SUBDUCTION ZONES.
300
00:16:40,360 --> 00:16:43,290
WHERE SUBDUCTING PLATES
MEET CONTINENTS,
301
00:16:43,360 --> 00:16:46,130
EARTH'S TALLEST MOUNTAINS
ARE BUILT:
302
00:16:46,200 --> 00:16:49,260
THE HIMALAYA OF ASIA,
303
00:16:49,330 --> 00:16:51,630
THE ALPS OF EUROPE,
304
00:16:51,700 --> 00:16:54,330
THE ANDES OF SOUTH AMERICA.
305
00:16:54,400 --> 00:16:57,000
SUBDUCTION CREATED THEM ALL.
306
00:16:59,140 --> 00:17:03,910
BUT SUBDUCTION CAN CREATE HAVOC
ON THE SURFACE.
307
00:17:03,980 --> 00:17:06,980
AS SEISMIC NETWORKS
IMPROVED AROUND THE WORLD,
308
00:17:07,050 --> 00:17:09,950
IT BECAME APPARENT
THAT SUBDUCTION WAS THE CULPRIT
309
00:17:10,020 --> 00:17:13,250
BEHIND EARTH'S
MOST POWERFUL EARTHQUAKES.
310
00:17:15,720 --> 00:17:19,330
- FIRST THE EARTHQUAKE ITSELF...
311
00:17:19,400 --> 00:17:21,230
[people screaming]
312
00:17:21,300 --> 00:17:24,660
A GROCERY STORE IN THE CAPITAL
AT THE MOMENT OF IMPACT.
313
00:17:24,730 --> 00:17:27,200
narrator:
THE TOHOKU EARTHQUAKE OF 2011
314
00:17:27,270 --> 00:17:29,770
WAS THE MOST POWERFUL
EVER KNOWN IN JAPAN
315
00:17:29,840 --> 00:17:33,410
AT MAGNITUDE 9.
316
00:17:33,480 --> 00:17:35,780
IT STRUCK
WHERE THE OCEANIC PACIFIC PLATE
317
00:17:35,840 --> 00:17:39,480
SUBDUCTS UNDER A PIECE
OF THE NORTH AMERICAN PLATE.
318
00:17:41,920 --> 00:17:43,950
- WHERE SUBDUCTION IS OCCURRING,
319
00:17:44,020 --> 00:17:48,890
YOU SEE A VERY WELL-DEFINED ZONE
OF EARTHQUAKES,
320
00:17:48,960 --> 00:17:52,760
ESSENTIALLY BETWEEN
THE DOWNGOING OCEANIC CRUST
321
00:17:52,830 --> 00:17:57,060
AND THE CONTINENTAL CRUST,
322
00:17:57,130 --> 00:17:59,370
AND IT FORMS A LINE
OF EARTHQUAKES
323
00:17:59,440 --> 00:18:02,940
WHERE THESE TWO CRUSTS
ARE IN CONTACT WITH EACH OTHER
324
00:18:03,010 --> 00:18:07,840
AND SLIPPING PAST EACH OTHER.
325
00:18:07,910 --> 00:18:11,140
[siren wailing]
326
00:18:11,210 --> 00:18:13,050
narrator: SUBDUCTION QUAKES
CAN ALSO GENERATE
327
00:18:13,120 --> 00:18:14,880
DEVASTATING TSUNAMIS
328
00:18:14,950 --> 00:18:17,420
BECAUSE OF THEIR PROXIMITY
TO COASTLINES.
329
00:18:17,490 --> 00:18:19,720
- ONE OF THE WORST
EARTHQUAKES EVER...
330
00:18:19,790 --> 00:18:23,390
- THE JAPANESE QUAKE AND
THE 2004 INDIAN OCEAN EARTHQUAKE
331
00:18:23,460 --> 00:18:26,430
OFF SUMATRA
ARE STRIKING EXAMPLES.
332
00:18:34,300 --> 00:18:37,040
EARTHQUAKES AND TSUNAMIS
ARE NOT THE ONLY ACTION
333
00:18:37,110 --> 00:18:39,770
SPAWNED BY SUBDUCTION.
334
00:18:39,840 --> 00:18:42,540
SUBDUCTION
ALSO CREATES VOLCANOES,
335
00:18:42,610 --> 00:18:47,310
AND THEY, TOO,
CAN BE LARGE AND DANGEROUS.
336
00:18:47,380 --> 00:18:51,120
- VOLCANOES IN THE SUBDUCTION
ZONES ARE FORMED
337
00:18:51,190 --> 00:18:56,820
BY MAGMAS THAT ARE MORE SILICIC,
OR MORE VISCOUS,
338
00:18:56,890 --> 00:19:00,590
AND THEY ARE
MUCH MORE EXPLOSIVE.
339
00:19:00,660 --> 00:19:04,060
SO THOSE ARE THE VOLCANOES
THAT CAN REALLY BE DANGEROUS
340
00:19:04,130 --> 00:19:06,130
AND REALLY CREATE TROUBLE.
341
00:19:10,610 --> 00:19:14,810
narrator: SUBDUCTION VOLCANOES
ARE EARTH'S MOST NOTORIOUS:
342
00:19:14,880 --> 00:19:18,410
MOUNT TUNGURAHUA IN ECUADOR,
343
00:19:18,480 --> 00:19:21,920
MOUNT VESUVIUS IN ITALY,
344
00:19:21,980 --> 00:19:24,720
MOUNT ASAMA IN JAPAN,
345
00:19:24,790 --> 00:19:27,620
MOUNT SAINT HELENS
IN THE U.S.
346
00:19:27,690 --> 00:19:31,530
ALL ARE KNOWN FOR EXPLOSIVE,
DESTRUCTIVE ERUPTIONS.
347
00:19:33,030 --> 00:19:35,960
THEY ALSO GROW TO GREAT HEIGHTS.
348
00:19:36,030 --> 00:19:37,860
THIS IS CHIMBORAZO,
349
00:19:37,930 --> 00:19:41,100
RISING 20,700 FEET
ABOVE SEA LEVEL
350
00:19:41,170 --> 00:19:44,870
IN THE ANDES MOUNTAINS
OF ECUADOR.
351
00:19:44,940 --> 00:19:47,040
WHEN MEASURED FROM THE CENTER
OF THE EARTH'S CORE
352
00:19:47,110 --> 00:19:48,910
TO THE VOLCANO'S SUMMIT,
353
00:19:48,980 --> 00:19:51,980
CHIMBORAZO
IS EARTH'S TALLEST MOUNTAIN,
354
00:19:52,050 --> 00:19:56,280
SOARING OVER 7,000 FEET CLOSER
TO THE SUN THAN MOUNT EVEREST.
355
00:19:58,050 --> 00:20:01,150
THAT'S BECAUSE THE VOLCANO SITS
ON THE EQUATOR
356
00:20:01,220 --> 00:20:04,490
WHERE THE EARTH BULGES OUTWARD
FROM THE FORCE OF ROTATION.
357
00:20:09,870 --> 00:20:12,070
EARTH SCIENTISTS
HAVE GOTTEN A GOOD HANDLE
358
00:20:12,130 --> 00:20:14,170
ON THE FORCES
DRIVING PLATE TECTONICS,
359
00:20:14,240 --> 00:20:16,700
LIKE SUBDUCTION,
360
00:20:16,770 --> 00:20:19,370
BUT QUESTIONS REMAIN.
361
00:20:19,440 --> 00:20:23,440
ONE OF THE BIGGEST QUESTIONS
IS HOW PLATE TECTONICS IS LINKED
362
00:20:23,510 --> 00:20:26,880
TO PROCESSES OPERATING
DEEP BELOW EARTH'S CRUST.
363
00:20:29,350 --> 00:20:32,990
THE DEEPER WE LOOK,
THE LESS WE KNOW.
364
00:20:33,060 --> 00:20:35,890
BUT NEW RESEARCH
IS TURNING UP BIG SURPRISES
365
00:20:35,960 --> 00:20:38,760
LURKING IN THE CENTER
OF THE EARTH.
366
00:20:38,830 --> 00:20:40,860
- TUMBLE INTO CASCADING
SALT BEDS,
367
00:20:40,930 --> 00:20:44,260
ESCAPE FROM HISSING STEAM CAVES,
368
00:20:44,330 --> 00:20:47,930
BEHOLD THE STAGGERING
UNDERGROUND OCEAN.
369
00:20:48,000 --> 00:20:51,040
YOU WILL ENCOUNTER BREATHTAKING
DANGERS BEYOND BELIEF
370
00:20:51,110 --> 00:20:53,670
HERE AT THE CENTER OF THE EARTH.
371
00:20:53,740 --> 00:20:55,580
[thunder crashes]
372
00:20:55,640 --> 00:20:57,480
narrator:
THE INSIDE OF EARTH,
373
00:20:57,550 --> 00:20:59,980
AN OBJECT OF GREAT CURIOSITY,
374
00:21:00,050 --> 00:21:02,820
WILD CONJECTURE.
375
00:21:02,880 --> 00:21:05,590
AT THE CENTER OF IT ALL
IS THE EARTH'S CORE,
376
00:21:05,650 --> 00:21:11,390
WHICH WAS DISCOVERED
ACCIDENTALLY ONLY 140 YEARS AGO.
377
00:21:11,460 --> 00:21:14,330
- A HUGE EARTHQUAKE
IN THE 1880s WAS--
378
00:21:14,400 --> 00:21:16,000
THE WAVES FROM THAT EARTHQUAKE,
379
00:21:16,060 --> 00:21:17,560
TRAVELING THROUGH
THE EARTH'S CORE,
380
00:21:17,630 --> 00:21:19,900
BOUNCING OFF THE EARTH'S CORE,
381
00:21:19,970 --> 00:21:22,800
WERE RECOGNIZED AS ARRIVING
AT DIFFERENT TIMES
382
00:21:22,870 --> 00:21:24,400
FROM THE SEISMIC WAVES
383
00:21:24,470 --> 00:21:26,610
THAT TRAVELED THROUGH
THE OUTER LAYERS OF THE EARTH.
384
00:21:26,680 --> 00:21:29,480
AND WITH THAT,
THE EARTH'S CORE WAS DISCOVERED.
385
00:21:29,540 --> 00:21:32,050
IT TOOK UNTIL THE 1920s
TO RECOGNIZE
386
00:21:32,110 --> 00:21:34,610
THAT THE EARTH
HAD A SOLID INNER CORE
387
00:21:34,680 --> 00:21:38,150
INSIDE THE FLUID OUTER CORE.
388
00:21:38,220 --> 00:21:40,590
narrator: AT HALF THE SIZE
OF THE PLANET,
389
00:21:40,660 --> 00:21:46,230
THE EARTH'S CORE IS PECULIAR
IN THAT IT'S ALL MADE OF IRON.
390
00:21:46,300 --> 00:21:51,200
BUT ITS INNER HALF IS SOLID,
AND ITS OUTER HALF IS LIQUID.
391
00:21:51,270 --> 00:21:53,700
- THE EARTH'S OUTER CORE
IS MOLTEN
392
00:21:53,770 --> 00:21:55,940
BECAUSE IT'S VERY HIGH
TEMPERATURE, AND IT'S--
393
00:21:56,000 --> 00:21:57,670
THE TEMPERATURES ARE
ABOVE THE MELTING TEMPERATURE
394
00:21:57,740 --> 00:21:59,210
OF THIS IRON-RICH MATERIAL,
395
00:21:59,270 --> 00:22:01,440
BUT THE EARTH'S INNER CORE
IS ACTUALLY--CAN BE SOLID
396
00:22:01,510 --> 00:22:04,280
BECAUSE WE HAVE
EVEN HIGHER PRESSURES,
397
00:22:04,350 --> 00:22:06,780
SO GET TO OVER
3 MILLION ATMOSPHERES,
398
00:22:06,850 --> 00:22:09,920
SO 3 MILLION TIMES THE PRESSURE
AT THE SURFACE OF THE PLANET.
399
00:22:09,990 --> 00:22:11,480
AND AT THOSE HIGH PRESSURES,
400
00:22:11,550 --> 00:22:13,790
THEY CAUSE THE MATERIAL
TO ACTUALLY SOLIDIFY.
401
00:22:17,330 --> 00:22:20,260
narrator: FORTUNATELY FOR US
AND ALL LIVING THINGS,
402
00:22:20,330 --> 00:22:22,730
THE EARTH'S OUTER CORE IS FLUID,
403
00:22:22,800 --> 00:22:27,630
FOR IT GENERATES OUR PLANET'S
PROTECTIVE MAGNETIC FIELD.
404
00:22:27,700 --> 00:22:30,170
- IF WE DIDN'T HAVE THE EARTH'S
MAGNETIC FIELD TODAY,
405
00:22:30,240 --> 00:22:33,810
WE PROBABLY COULDN'T HAVE LIFE
ON THE SURFACE OF THE PLANET.
406
00:22:33,880 --> 00:22:36,680
THE SUN'S ALWAYS THROWING ALL
THESE PARTICLES AT THE PLANET,
407
00:22:36,750 --> 00:22:38,240
BUT THEN THE EARTH'S
MAGNETIC FIELD
408
00:22:38,310 --> 00:22:40,210
PROTECTS THIS NICE,
PROTECTIVE COATING
409
00:22:40,280 --> 00:22:42,780
THAT PROTECTS US
FROM THESE DAMAGING RAYS
410
00:22:42,850 --> 00:22:44,780
AND PARTICLE--
HIGH-ENERGY PARTICLES.
411
00:22:47,290 --> 00:22:48,960
narrator: THE EARTH IS UNIQUE
AMONG PLANETS
412
00:22:49,020 --> 00:22:51,760
IN HAVING A MAGNETIC FIELD.
413
00:22:51,830 --> 00:22:53,790
MARS HAD ONE EARLY ON,
414
00:22:53,860 --> 00:22:55,800
BUT ITS SMALL CORE
COOLED QUICKLY,
415
00:22:55,860 --> 00:22:58,800
AND IT WAS LOST AND, WITH IT,
416
00:22:58,870 --> 00:23:02,370
THE CHANCE FOR LIFE
TO TAKE HOLD ON ITS SURFACE.
417
00:23:02,440 --> 00:23:06,470
MEANWHILE, EARTH'S MAGNETIC
FIELD, FOR ALL ITS IMPORTANCE,
418
00:23:06,540 --> 00:23:10,180
IS NOT WELL UNDERSTOOD.
419
00:23:10,250 --> 00:23:13,250
WHAT IS GETTING CLEARER
IS WHAT IS ACTUALLY GOING ON
420
00:23:13,320 --> 00:23:15,350
IN THE EARTH'S CORE ITSELF.
421
00:23:15,420 --> 00:23:17,250
- OKAY.
LET'S PUT IT ON THERE.
422
00:23:17,320 --> 00:23:18,550
narrator:
THAT IS BECAUSE
423
00:23:18,620 --> 00:23:20,050
SCIENTISTS HAVE
FINALLY RE-CREATED
424
00:23:20,120 --> 00:23:23,590
THE CORE'S EXTREME CONDITIONS
IN THE LAB.
425
00:23:23,660 --> 00:23:27,660
3 MILLION ATMOSPHERES
AND 10,000 DEGREES FAHRENHEIT,
426
00:23:27,730 --> 00:23:30,860
THE SAME TEMPERATURE
AS THE SURFACE OF THE SUN.
427
00:23:34,040 --> 00:23:36,170
- SO YOU HAVE TO REACH
MILLIONS OF ATMOSPHERES,
428
00:23:36,240 --> 00:23:37,870
AND YOU HAVE TO REACH
THOUSANDS OF DEGREES,
429
00:23:37,940 --> 00:23:40,940
SO THAT'S A VERY CHALLENGING
TECHNOLOGICAL PROBLEM.
430
00:23:41,010 --> 00:23:41,940
OKAY, GREAT.
431
00:23:42,010 --> 00:23:44,840
LOOKS GOOD.
432
00:23:44,910 --> 00:23:47,210
SO ONE WAY TO REACH
THE VERY HIGH PRESSURES
433
00:23:47,280 --> 00:23:49,950
AND TEMPERATURES IN THE PLANET
IS TO COMPRESS MATERIALS
434
00:23:50,020 --> 00:23:51,820
BETWEEN THE TIPS
OF TWO DIAMONDS,
435
00:23:51,890 --> 00:23:55,120
AND SINCE DIAMOND IS THE HARDEST
MATERIAL ON THE PLANET,
436
00:23:55,190 --> 00:23:59,090
WE CAN GENERATE
VERY HIGH PRESSURES.
437
00:23:59,160 --> 00:24:00,490
AND THEN,
AT THE SAME TIME,
438
00:24:00,560 --> 00:24:02,860
WE CAN USE LASERS
TO HEAT THE SAMPLE
439
00:24:02,930 --> 00:24:04,700
AND TO REACH
THE SAME CONDITIONS
440
00:24:04,770 --> 00:24:08,870
WE THINK ARE INSIDE THE PLANET.
441
00:24:08,940 --> 00:24:13,510
narrator: THE CORE'S SUN-HOT
HEAT IS CRUCIAL TO UNDERSTAND.
442
00:24:13,580 --> 00:24:15,540
IT AFFECTS EVERYTHING
AT THE SURFACE,
443
00:24:15,610 --> 00:24:19,050
1,800 MILES ABOVE.
444
00:24:19,110 --> 00:24:20,350
TO GET UP HERE,
445
00:24:20,420 --> 00:24:24,420
IT TRAVELS THROUGH TWO LAYERS
OF SOLID ROCK.
446
00:24:24,490 --> 00:24:28,660
THE FIRST IS THE MANTLE,
EARTH'S BIGGEST LAYER BY FAR.
447
00:24:30,260 --> 00:24:31,860
AND THEN THE CRUST,
448
00:24:31,930 --> 00:24:35,730
REALLY JUST A THIN VENEER
ON THE EARTH.
449
00:24:35,800 --> 00:24:38,970
SCIENTISTS BELIEVE THAT
THE IMMENSE HEAT OF THE CORE
450
00:24:39,030 --> 00:24:42,170
MAKES THE MANTLE SO HOT
THAT IT ACTS LIKE A FLUID
451
00:24:42,240 --> 00:24:45,510
AND RISES
UNTIL IT HITS THE CRUST.
452
00:24:45,570 --> 00:24:49,580
SOME OF THE HEAT THEN CIRCULATES
ALONG THE CRUST'S UNDERSIDE
453
00:24:49,640 --> 00:24:53,850
UNTIL SUBDUCTING SLABS OF CRUST
TAKE IT DOWNWARD.
454
00:24:53,920 --> 00:24:57,820
IT'S A GIANT RECYCLING TREADMILL
CALLED CONVECTION.
455
00:24:59,820 --> 00:25:01,220
THROUGH EXPERIMENTS,
456
00:25:01,290 --> 00:25:03,960
SCIENTISTS HAVE CALCULATED
THAT HEAT'S ROUND TRIP
457
00:25:04,030 --> 00:25:07,630
FROM THE CORE TO THE CRUST
AND BACK TO THE CORE AGAIN
458
00:25:07,700 --> 00:25:11,400
TAKES 300 MILLION YEARS.
459
00:25:11,470 --> 00:25:13,930
THIS CIRCULATION OF HEAT
IS KEPT ALIVE
460
00:25:14,000 --> 00:25:15,940
BY THE SINKING
OF COLD, HEAVY PLATES
461
00:25:16,000 --> 00:25:18,670
INTO THE HOT MANTLE BELOW.
462
00:25:18,740 --> 00:25:20,070
IN OTHER WORDS,
463
00:25:20,140 --> 00:25:23,610
THOSE SLABS CAUSE
QUITE A STIR AS THEY DESCEND.
464
00:25:25,580 --> 00:25:27,810
- WE CAN TRACK THOSE SLABS
WITH TOMOGRAPHY
465
00:25:27,880 --> 00:25:30,380
DOWN AT LEAST
INTO THE MIDDLE MANTLE.
466
00:25:30,450 --> 00:25:32,520
AND PROBABLY THOSE SLABS
REACH ALL THE WAY
467
00:25:32,590 --> 00:25:34,420
TO THE CORE-MANTLE BOUNDARY,
468
00:25:34,490 --> 00:25:38,890
AND THERE'S A SLAB GRAVEYARD
THAT SITS ABOVE THE CORE.
469
00:25:38,960 --> 00:25:43,300
THAT SLAB GRAVEYARD
MAY IN TURN HELP DRIVE
470
00:25:43,370 --> 00:25:45,970
THE CONVECTION CELLS
IN EARTH'S MANTLE
471
00:25:46,030 --> 00:25:48,070
THAT IN TURN THEN REACH UP
472
00:25:48,140 --> 00:25:50,370
AND DRIVE THE PATTERN
OF PLATE TECTONICS
473
00:25:50,440 --> 00:25:52,240
AND THE SHIFTING PLATES
AT EARTH'S SURFACE.
474
00:25:54,340 --> 00:25:57,380
narrator: THE SINKING SLABS NOT
ONLY DRIVE HEAT IN THE MANTLE;
475
00:25:57,450 --> 00:26:00,380
THEY HAVE RADICALLY CHANGED
THE MAKEUP OF THE MANTLE
476
00:26:00,450 --> 00:26:04,850
OVER THE COURSE
OF GEOLOGIC TIME.
477
00:26:04,920 --> 00:26:09,060
- THE MANTLE IS A VERY
COMPLICATED MIXTURE OF THINGS
478
00:26:09,120 --> 00:26:11,320
THAT HAVE BEEN STIRRED
INTERNALLY
479
00:26:11,390 --> 00:26:13,560
AND THINGS THAT HAVE COME UP
TO THE SURFACE,
480
00:26:13,630 --> 00:26:17,360
BEEN OCEAN FLOOR FOR A WHILE,
AND THEN TAKEN BACK DOWN.
481
00:26:19,730 --> 00:26:22,540
IN THE 4.5 BILLION-YEAR HISTORY
OF THE EARTH,
482
00:26:22,600 --> 00:26:26,910
THE ENTIRE MANTLE HAS BEEN
CIRCULATED ABOUT ONCE.
483
00:26:26,980 --> 00:26:29,140
VIRTUALLY NOTHING
AT THE EARTH'S SURFACE
484
00:26:29,210 --> 00:26:31,440
OR IN THE INTERIOR IS PERMANENT.
485
00:26:31,510 --> 00:26:32,580
THINGS ARE CHANGING
ALL THE TIME.
486
00:26:37,350 --> 00:26:39,290
narrator:
HEAT RISING UP FROM THE CORE
487
00:26:39,350 --> 00:26:42,520
DOES NOT ALWAYS
RECYCLE BACK DOWN.
488
00:26:42,590 --> 00:26:45,960
SOMETIMES IT ESCAPES
ITS EARTHLY CONFINES
489
00:26:46,030 --> 00:26:50,900
AS VOLCANIC ERUPTIONS.
490
00:26:50,970 --> 00:26:52,670
EARTH IS BY FAR
491
00:26:52,730 --> 00:26:57,440
THE SOLAR SYSTEM'S MOST
VOLCANICALLY ACTIVE PLANET.
492
00:26:57,510 --> 00:27:02,310
VOLCANOES ARE NATURE'S MOST
VIOLENT AND DESTRUCTIVE FORCE.
493
00:27:02,380 --> 00:27:04,010
BUT IRONICALLY,
494
00:27:04,080 --> 00:27:07,750
THIS FORCE EMANATING FROM
THE EARTH'S MANTLE DEEP BELOW
495
00:27:07,820 --> 00:27:11,220
IS AT THE VERY ROOT
OF THE CREATION AND MAINTENANCE
496
00:27:11,290 --> 00:27:14,090
OF LIFE ON EARTH'S SURFACE.
497
00:27:15,860 --> 00:27:18,960
- VOLCANOES HAVE CERTAINLY
INFLUENCED LIFE ON EARTH.
498
00:27:19,030 --> 00:27:22,030
AND THAT'S NOT JUST WHEN
THEY HAVE A BIG ERUPTION
499
00:27:22,100 --> 00:27:23,330
AND PEOPLE DIE.
500
00:27:23,400 --> 00:27:28,500
BUT THEY ALSO MAY HAVE CREATED
LIFE ON EARTH.
501
00:27:28,570 --> 00:27:30,770
IN THE LAST FEW DECADES,
502
00:27:30,840 --> 00:27:34,410
HYDROTHERMAL VENTS WERE
DISCOVERED DEEP IN THE OCEAN,
503
00:27:34,480 --> 00:27:38,680
AND MINERALS ARE COMING OUT
THAT CAN ACTUALLY FEED LIFE
504
00:27:38,750 --> 00:27:40,380
AROUND THOSE VENTS,
505
00:27:40,450 --> 00:27:44,280
AND A VERY SURPRISING FIND
WAS THAT LIFE COULD EXIST
506
00:27:44,350 --> 00:27:47,390
AT SUCH DEPTH IN THE OCEAN.
507
00:27:51,530 --> 00:27:54,030
narrator: VOLCANOES WERE
THE ORIGINAL ARCHITECTS
508
00:27:54,100 --> 00:27:55,830
OF OUR ATMOSPHERE,
509
00:27:55,900 --> 00:27:58,830
UNLOCKING CO2 AND WATER
FROM THE MANTLE'S ROCKS
510
00:27:58,900 --> 00:28:00,900
AND TAKING THEM TO THE SURFACE.
511
00:28:02,970 --> 00:28:04,500
ONE OF THE LARGEST
CONCENTRATIONS
512
00:28:04,570 --> 00:28:08,010
OF ACTIVE VOLCANOES
ON EARTH IS IN JAPAN--
513
00:28:08,080 --> 00:28:10,080
MORE THAN 100.
514
00:28:10,150 --> 00:28:13,610
MOUNT FUJI
IS JAPAN'S LARGEST VOLCANO,
515
00:28:13,680 --> 00:28:17,750
RISING 12,400 FEET HIGH.
516
00:28:17,820 --> 00:28:21,850
THIS GRACEFUL PEAK IS
A MASSIVE SUBDUCTION VOLCANO,
517
00:28:21,920 --> 00:28:26,360
BUT THE LARGEST VOLCANOES
ON EARTH ARE 100 TIMES BIGGER.
518
00:28:28,100 --> 00:28:30,060
THEY BELONG TO A RARE CLASS
OF VOLCANO
519
00:28:30,130 --> 00:28:34,100
KNOWN AS A MANTLE PLUME VOLCANO,
520
00:28:34,170 --> 00:28:36,670
AND THE LARGEST OF ALL
ARE ON HAWAII.
521
00:28:39,970 --> 00:28:42,910
LAVA HAS BEEN ERUPTING
FROM THIS SPOT IN THE PACIFIC
522
00:28:42,980 --> 00:28:47,010
FOR AT LEAST 75 MILLION YEARS.
523
00:28:47,080 --> 00:28:52,190
IT BUILT MAUNA LOA, EARTH'S
LARGEST VOLCANO BY VOLUME.
524
00:28:52,250 --> 00:28:57,990
BUT MAUNA LOA IS NOT THE BIGGEST
VOLCANO IN THE SOLAR SYSTEM.
525
00:28:58,060 --> 00:29:00,090
- THE LARGEST VOLCANO
IN THE SOLAR SYSTEM
526
00:29:00,160 --> 00:29:04,030
IS OLYMPUS MONS ON MARS.
527
00:29:04,100 --> 00:29:06,900
IT'S ABOUT 26 KILOMETERS HIGH
528
00:29:06,970 --> 00:29:12,040
AND AROUND
600 KILOMETERS ACROSS.
529
00:29:14,210 --> 00:29:15,710
narrator:
COMPARED TO HAWAII,
530
00:29:15,780 --> 00:29:20,250
OLYMPUS MONS IS VASTLY BIGGER
IN ALL RESPECTS.
531
00:29:20,320 --> 00:29:24,820
WHY ARE EARTH'S VOLCANOES
SO MUCH SMALLER?
532
00:29:24,890 --> 00:29:27,290
- ON MARS,
THERE'S NO PLATE TECTONICS,
533
00:29:27,360 --> 00:29:32,490
SO THE SAME, LET'S SAY, HOT SPOT
CAN BUILD UP A VOLCANO
534
00:29:32,560 --> 00:29:36,500
IN THE SAME LOCATION FOR VERY,
VERY LONG PERIODS OF TIME.
535
00:29:39,900 --> 00:29:42,000
ON THE EARTH,
WE CAN'T HAVE THAT SITUATION
536
00:29:42,070 --> 00:29:45,170
BECAUSE THE PLATES ARE MOVING,
SO YOU GET, FOR EXAMPLE,
537
00:29:45,240 --> 00:29:49,310
HOT SPOT LIKE THE ONE THAT
FORMED THE HAWAIIAN VOLCANOES,
538
00:29:49,380 --> 00:29:53,480
BUT THE PLATE IS MOVING OVER IT,
SO IT PUNCHES ONE VOLCANO,
539
00:29:53,550 --> 00:29:54,910
BUT THEN THE PLATE MOVES,
540
00:29:54,980 --> 00:29:59,320
AND THE VOLCANO MOVES
SOMEWHERE ELSE.
541
00:29:59,390 --> 00:30:04,060
SO ON EARTH, WE DON'T REALLY
BUILD THOSE SIZES OF VOLCANOES.
542
00:30:05,730 --> 00:30:08,560
[fire roaring and crackling]
543
00:30:08,630 --> 00:30:11,500
narrator: THE SOURCE THAT FEEDS
EARTH'S GIANT VOLCANOES
544
00:30:11,570 --> 00:30:14,100
IS THOUGHT TO BE
A NARROW CYLINDER OF HOT ROCK
545
00:30:14,170 --> 00:30:17,140
THAT REACHES DEEP
INTO THE MANTLE.
546
00:30:17,210 --> 00:30:20,070
HOW DEEP IS A MATTER OF DEBATE.
547
00:30:20,140 --> 00:30:22,640
BUT RECENT SEISMIC STUDIES
OF THE HAWAIIAN CHAIN
548
00:30:22,710 --> 00:30:24,940
IMAGED FOR THE FIRST TIME
549
00:30:25,010 --> 00:30:28,210
A HOT PLUME REACHING HALFWAY
TO THE EARTH'S CORE.
550
00:30:30,350 --> 00:30:33,750
CHEMICAL ANALYSIS OF LAVAS
RETRIEVED IN DRILL CORES
551
00:30:33,820 --> 00:30:36,390
TRACES THE PLUME EVEN DEEPER,
552
00:30:36,460 --> 00:30:39,860
ACTUALLY EXTENDING
TO THE EARTH'S CORE ITSELF.
553
00:30:42,760 --> 00:30:45,330
THE DEEPEST REACHES
OF OUR PLANET, THEN,
554
00:30:45,400 --> 00:30:46,930
ARE INTIMATELY CONNECTED
555
00:30:47,000 --> 00:30:50,170
WITH GEOLOGICAL ACTION
AT THE SURFACE.
556
00:30:53,240 --> 00:30:55,310
WITHOUT THESE
DEEP-SEATED FORCES,
557
00:30:55,380 --> 00:31:00,810
LIFE WOULD HAVE NOT GAINED
A FOOTHOLD ON OUR PLANET,
558
00:31:00,880 --> 00:31:02,280
AND IT WOULDN'T HAVE FLOURISHED
559
00:31:02,350 --> 00:31:05,480
AND EVOLVED INTO COUNTLESS
WONDROUS FORMS
560
00:31:05,550 --> 00:31:08,490
WITHOUT SOMETHING ELSE:
561
00:31:08,560 --> 00:31:11,920
A REMARKABLY STABLE,
PRECISELY TUNED CLIMATE.
562
00:31:17,770 --> 00:31:20,200
FOR MOST OF EARTH'S EXISTENCE,
563
00:31:20,270 --> 00:31:22,800
THE TEMPERATURE AT THE SURFACE
HAS RARELY WAVERED.
564
00:31:24,670 --> 00:31:28,070
WHY THIS IS
IS A GREAT MYSTERY.
565
00:31:28,140 --> 00:31:32,910
THE GLOBAL MEAN TEMPERATURE
IS A COMFORTABLE 59 DEGREES.
566
00:31:32,980 --> 00:31:35,250
INCREASE THAT
BY JUST 18 DEGREES,
567
00:31:35,320 --> 00:31:39,690
AND ICE AT THE POLES WOULD MELT.
568
00:31:39,750 --> 00:31:42,150
DECREASE IT BY 18 DEGREES,
569
00:31:42,220 --> 00:31:44,960
AND THE ENTIRE WORLD
WOULD FREEZE OVER.
570
00:31:46,660 --> 00:31:49,760
OTHER PLANETS
ARE FAR FROM HABITABLE.
571
00:31:49,830 --> 00:31:53,170
VENUS,
WITH 200,000 TIMES MORE CO2
572
00:31:53,230 --> 00:31:55,100
IN ITS ATMOSPHERE THAN EARTH,
573
00:31:55,170 --> 00:31:59,170
IS RAVAGED BY TEMPERATURES
REACHING 900 DEGREES FAHRENHEIT.
574
00:32:01,910 --> 00:32:05,950
MARS, LONG AGO STRIPPED OF ITS
ATMOSPHERE AND MAGNETIC SHIELD,
575
00:32:06,010 --> 00:32:11,180
IS DEEPLY FROZEN TO AN AVERAGE
OF 70 DEGREES BELOW ZERO.
576
00:32:11,250 --> 00:32:14,290
[lively music]
577
00:32:14,360 --> 00:32:18,660
¶ ¶
578
00:32:18,730 --> 00:32:22,060
EARTH'S CLIMATE IS KEPT MODERATE
BY A LITTLE UNDERSTOOD INTERPLAY
579
00:32:22,130 --> 00:32:26,400
OF GEOLOGIC AND BIOLOGIC FORCES.
580
00:32:26,470 --> 00:32:30,200
VOLCANIC ERUPTIONS SPEW CO2
INTO THE AIR.
581
00:32:30,270 --> 00:32:33,170
PLATE TECTONICS BUILDS MOUNTAINS
582
00:32:33,240 --> 00:32:36,710
AND RIFTS APART OCEAN BASINS.
583
00:32:36,780 --> 00:32:39,250
THEN WEATHER ERODES THE LAND,
584
00:32:39,310 --> 00:32:41,010
CAPTURING CO2
585
00:32:41,080 --> 00:32:44,220
AND LOCKING IT AWAY
IN SEDIMENTS.
586
00:32:44,290 --> 00:32:48,850
LIVING ORGANISMS ADD
THEIR ALTERATIONS INTO THE MIX.
587
00:32:48,920 --> 00:32:52,830
ALL IS BUILT INTO A SYSTEM
OF GLOBAL CHECKS AND BALANCES.
588
00:32:56,900 --> 00:32:58,600
THERE HAVE BEEN ONLY A FEW TIMES
589
00:32:58,670 --> 00:33:02,800
WHEN EARTH'S CLIMATE TIPPED
WELL BEYOND ITS COMFORT ZONE.
590
00:33:02,870 --> 00:33:08,310
EARTH'S COLDEST EXTREME HAPPENED
ABOUT 750 MILLION YEARS AGO
591
00:33:08,380 --> 00:33:11,980
AND PROBABLY SEVERAL TIMES
BEFORE THAT.
592
00:33:12,050 --> 00:33:16,080
IT WAS CALLED SNOWBALL EARTH.
593
00:33:16,150 --> 00:33:18,750
- SNOWBALL EARTH REFERS
TO A TIME IN THE EARTH'S HISTORY
594
00:33:18,820 --> 00:33:22,190
WHEN THE EARTH
WAS ENTIRELY COVERED WITH ICE.
595
00:33:22,260 --> 00:33:24,860
THAT MEANS GLACIERS
ON THE CONTINENTS
596
00:33:24,930 --> 00:33:27,190
AND SEA ICE COVERING
MOST OF THE OCEANS
597
00:33:27,260 --> 00:33:30,660
ALL THE WAY DOWN TO THE EQUATOR.
598
00:33:30,730 --> 00:33:32,370
narrator:
DURING SNOWBALL EARTH,
599
00:33:32,430 --> 00:33:34,300
THE TEMPERATURE
AT THE EQUATOR PLUNGED
600
00:33:34,370 --> 00:33:37,200
TO MINUS 4 DEGREES FAHRENHEIT.
601
00:33:37,270 --> 00:33:40,140
LIFE, STILL IN
ITS PRIMITIVE BACTERIAL STAGE,
602
00:33:40,210 --> 00:33:43,710
SURVIVED THE DEEP FREEZE
AS IT DOES TODAY:
603
00:33:43,780 --> 00:33:46,880
BELOW ICE SHELVES
AND EVEN BELOW GLACIERS.
604
00:33:49,580 --> 00:33:52,720
SCIENTISTS THINK THAT
THE TRIGGER FOR SNOWBALL EARTH
605
00:33:52,790 --> 00:33:58,060
WAS THE BUNCHING
OF CONTINENTS AT THE EQUATOR.
606
00:33:58,130 --> 00:34:00,590
THE GIANT LAND MASS
ATTRACTED MOISTURE,
607
00:34:00,660 --> 00:34:03,600
AND GREAT STORMS ENSUED.
608
00:34:03,660 --> 00:34:06,770
RAIN STRIPPED CO2
FROM THE ATMOSPHERE
609
00:34:06,830 --> 00:34:11,240
AND LOCKED IT
IN ERODING SEDIMENTS.
610
00:34:11,310 --> 00:34:14,610
AS CO2 LEVELS DROPPED,
SO DID THE TEMPERATURE.
611
00:34:20,920 --> 00:34:24,720
VOLCANIC ERUPTIONS EVENTUALLY
OVERPOWERED SNOWBALL EARTH
612
00:34:24,790 --> 00:34:29,420
BY INJECTING CO2
BACK INTO THE ATMOSPHERE.
613
00:34:29,490 --> 00:34:31,320
AS THE CLIMATE RESTABILIZED,
614
00:34:31,390 --> 00:34:34,930
THE SURVIVING BACTERIAL
LIFE FORMS MULTIPLIED,
615
00:34:35,000 --> 00:34:36,660
PHOTOSYNTHESIZED,
616
00:34:36,730 --> 00:34:39,030
AND FILLED THE AIR WITH OXYGEN,
617
00:34:39,100 --> 00:34:42,070
A REQUIREMENT
FOR MORE COMPLEX LIFE.
618
00:34:43,740 --> 00:34:47,710
FINALLY, 550 MILLION YEARS AGO,
619
00:34:47,780 --> 00:34:50,710
LIFE BRANCHED OUT AND BEGAN
ITS EXTRAORDINARY JOURNEY
620
00:34:50,780 --> 00:34:53,710
OF DIVERSIFICATION
AND EVOLUTION.
621
00:34:56,720 --> 00:35:00,350
WHY THIS HAPPENED
IS STILL A MYSTERY,
622
00:35:00,420 --> 00:35:02,960
BUT THE EXTREME HIT
THAT LIFE TOOK
623
00:35:03,020 --> 00:35:04,490
DURING SNOWBALL EARTH
624
00:35:04,560 --> 00:35:09,100
MAY HAVE ACTUALLY BEEN
PART OF THE REASON.
625
00:35:09,160 --> 00:35:11,000
- ONCE LIFE WAS ESTABLISHED
ON THE EARTH,
626
00:35:11,070 --> 00:35:14,000
IT CONTINUED TO SHOW EVIDENCE
THAT IT WAS EXTREMELY ADAPTABLE,
627
00:35:14,070 --> 00:35:17,400
THAT WHATEVER HARSH CONDITIONS
WERE THROWN AT IT,
628
00:35:17,470 --> 00:35:21,610
THAT IT WAS ABLE TO ADAPT
TO FIND A WAY TO SURVIVE.
629
00:35:21,680 --> 00:35:24,480
SO EVEN THROUGH PERIODS
LIKE SNOWBALL EARTH,
630
00:35:24,550 --> 00:35:27,580
LIFE WOULD ADAPT TO THOSE
CONDITIONS AND REEMERGE.
631
00:35:27,650 --> 00:35:30,820
AND IN FACT, THOSE SORTS OF
CONDITIONS WERE MAJOR FACTORS
632
00:35:30,890 --> 00:35:32,850
DRIVING THE EVOLUTION
OF LIFE ON EARTH.
633
00:35:37,230 --> 00:35:40,390
narrator: THE NEXT TIME EARTH'S
CLIMATE WAS KNOCKED OFF BALANCE
634
00:35:40,460 --> 00:35:44,030
WAS AT A TIME WHEN EARTH
EXPERIENCED ITS BIGGEST UPHEAVAL
635
00:35:44,100 --> 00:35:47,770
SINCE THE EARLY DAYS
OF ITS FORMATION.
636
00:35:47,840 --> 00:35:50,900
- ABOUT 250 MILLION YEARS AGO,
637
00:35:50,970 --> 00:35:54,210
95% OF LIFE ON EARTH
DISAPPEARED.
638
00:35:56,840 --> 00:35:59,510
WE THINK THAT'S BECAUSE
OF VERY LARGE ERUPTIONS
639
00:35:59,580 --> 00:36:02,720
IN THE SIBERIAN TRAPS.
640
00:36:02,780 --> 00:36:06,020
[clacking]
641
00:36:06,090 --> 00:36:10,060
narrator: EARTH SCIENTISTS HAVE
MAPPED 800,000 SQUARE MILES
642
00:36:10,120 --> 00:36:12,990
OF SIBERIA THAT WERE COVERED
BY LAVA FLOWS
643
00:36:13,060 --> 00:36:16,460
UP TO 12,000 FEET THICK.
644
00:36:16,530 --> 00:36:20,530
THEY CALL THIS PROVINCE
THE SIBERIAN TRAPS.
645
00:36:20,600 --> 00:36:23,900
- THOSE ERUPTIONS
WOULD HAVE PUT A LOT OF DUST,
646
00:36:23,970 --> 00:36:27,070
A LOT OF SULFUR
IN THE ATMOSPHERE,
647
00:36:27,140 --> 00:36:29,710
COOLED THE TEMPERATURE.
648
00:36:29,780 --> 00:36:33,850
SO THIS KILLED
A LOT OF LIFE ON EARTH.
649
00:36:33,920 --> 00:36:38,380
narrator: THE CLIMATE RECOVERED
EVENTUALLY, AND SO DID LIFE.
650
00:36:38,450 --> 00:36:39,950
BUT 90 MILLION YEARS AGO,
651
00:36:40,020 --> 00:36:44,590
THE HOTTEST PERIOD EVER KNOWN
ENVELOPED THE EARTH.
652
00:36:44,660 --> 00:36:48,030
DINOSAURS ROAMED
WHAT ARE NOW THE ICY REALMS
653
00:36:48,100 --> 00:36:50,030
OF THE ARCTIC CIRCLE.
654
00:36:50,100 --> 00:36:55,170
AROUND THEM WERE FELLOW
SWAMP-DWELLERS LIKE ALLIGATORS.
655
00:36:55,240 --> 00:36:59,000
WHAT WERE THEY DOING
AT THE EARTH'S POLES?
656
00:36:59,070 --> 00:37:03,180
SCIENTISTS FIGURED OUT THAT
PLATE TECTONICS WAS THE CULPRIT.
657
00:37:04,650 --> 00:37:06,410
100 MILLION YEARS AGO,
658
00:37:06,480 --> 00:37:08,250
THE CONTINENTS
HAD WRENCHED APART,
659
00:37:08,320 --> 00:37:11,250
AND SEA LEVEL ROSE.
660
00:37:11,320 --> 00:37:13,550
MOUNTAIN BUILDING SLOWED DOWN,
661
00:37:13,620 --> 00:37:17,290
AND SO DID RAINFALL AND EROSION.
662
00:37:17,360 --> 00:37:19,760
BUT CO2-SPEWING
VOLCANIC ERUPTIONS,
663
00:37:19,830 --> 00:37:25,430
ESPECIALLY IN THE MID-OCEAN
RIFT ZONES, DID NOT.
664
00:37:25,500 --> 00:37:27,200
- WHEN CONTINENTS
ARE SPLITTING APART
665
00:37:27,270 --> 00:37:29,240
AND YOU HAVE MORE SEA FLOOR
SPREADING,
666
00:37:29,300 --> 00:37:31,670
YOU'RE ADDING MORE CO2
TO THE ATMOSPHERE,
667
00:37:31,740 --> 00:37:34,470
AND IT'S NOT BEING REMOVED
AS QUICKLY
668
00:37:34,540 --> 00:37:38,040
BY WEATHERING OF THE CONTINENTS,
669
00:37:38,110 --> 00:37:40,580
SO IT'S WARMER
DURING THOSE PERIODS.
670
00:37:40,650 --> 00:37:42,580
[bird cawing]
671
00:37:42,650 --> 00:37:45,180
narrator: TEMPERATURES ROSE
TO A BALMY 54 DEGREES
672
00:37:45,250 --> 00:37:48,890
AT THE NORTH AND SOUTH POLES.
673
00:37:48,960 --> 00:37:51,390
THE CLIMATE SO AGREED
WITH THE DINOSAURS
674
00:37:51,460 --> 00:37:55,390
THAT THEY DOMINATED LIFE
ON EARTH FOR MILLIONS OF YEARS.
675
00:37:57,330 --> 00:38:00,530
THEN,
65 MILLION YEARS AGO,
676
00:38:00,600 --> 00:38:04,300
A MASSIVE METEORITE IMPACT
SUDDENLY ENDED THEIR REIGN.
677
00:38:04,370 --> 00:38:07,210
[explosion]
678
00:38:11,380 --> 00:38:13,880
THE METEORITE GOUGED OUT
A HUGE CRATER
679
00:38:13,950 --> 00:38:15,580
OVER 100 MILES ACROSS
680
00:38:15,650 --> 00:38:19,220
WITH THE TOWN OF CHICXULUB,
MEXICO, AT ITS CENTER.
681
00:38:22,460 --> 00:38:25,960
THE CITY OF MERIDA
ALSO LIES WITHIN THE CRATER,
682
00:38:26,030 --> 00:38:29,800
WHICH WAS BURIED BY SEDIMENT
MILLIONS OF YEARS AGO
683
00:38:29,860 --> 00:38:33,200
AND ONLY DISCOVERED BY CHANCE
AS GEOLOGISTS EXPLORED FOR OIL
684
00:38:33,270 --> 00:38:35,100
IN THE 1970s.
685
00:38:40,040 --> 00:38:42,780
THE CRATER AND ITS SURROUNDINGS
ARE ALSO THE SITE
686
00:38:42,840 --> 00:38:46,210
OF THE GREAT CITIES
BUILT BY THE ANCIENT MAYA.
687
00:38:46,280 --> 00:38:49,080
BUT NONE OF THE HUMAN DRAMA
PLAYING OUT IN THIS REGION
688
00:38:49,150 --> 00:38:50,680
WOULD HAVE BEEN POSSIBLE
689
00:38:50,750 --> 00:38:52,720
IF IT WEREN'T
FOR THE KILLER METEORITE
690
00:38:52,790 --> 00:38:54,450
THAT STRUCK HERE,
691
00:38:54,520 --> 00:38:57,760
WIPING OUT THE DINOSAURS.
692
00:38:57,830 --> 00:39:00,530
THEIR EXTINCTION OPENED
AN EVOLUTIONARY DOOR
693
00:39:00,590 --> 00:39:03,260
FOR MAMMALS LIKE US TO EVOLVE.
694
00:39:06,400 --> 00:39:08,630
BUT 65 MILLION YEARS AGO,
695
00:39:08,700 --> 00:39:10,700
THE EARTHLY STAGE
WAS FAR FROM SET
696
00:39:10,770 --> 00:39:13,740
FOR THE ENTRANCE OF PEOPLE.
697
00:39:13,810 --> 00:39:18,180
CO2 LEVELS AND TEMPERATURES
WERE MUCH TOO HIGH.
698
00:39:18,250 --> 00:39:22,510
LUCKILY FOR US, PLATE TECTONICS
BUILT THE MOST MASSIVE STRUCTURE
699
00:39:22,580 --> 00:39:26,490
ON EARTH TO MAKE
THE CLIMATE HUMAN-FRIENDLY:
700
00:39:26,550 --> 00:39:31,120
THE GREAT HIMALAYA RANGE.
701
00:39:31,190 --> 00:39:35,490
ABOUT 60 MILLION YEARS AGO,
INDIA, ONCE A MASSIVE ISLAND,
702
00:39:35,560 --> 00:39:39,160
RAMMED ASIA, AND THE BUILDING
OF THE HIMALAYA BEGAN.
703
00:39:41,840 --> 00:39:43,740
AS THE HIMALAYAS GREW,
704
00:39:43,800 --> 00:39:48,110
A GREAT BLOCK OF LAND
ROSE UP BEHIND THE RANGE.
705
00:39:48,180 --> 00:39:50,240
IT FORMED THE TIBETAN PLATEAU
706
00:39:50,310 --> 00:39:54,180
AND EVEN RAISED THE LAND
AS FAR TO THE NORTH AS MONGOLIA,
707
00:39:54,250 --> 00:39:57,650
MORE THAN 1,000 MILES AWAY.
708
00:39:57,720 --> 00:40:01,390
SINCE THEN, THE EARTH'S CLIMATE
HAS NEVER BEEN THE SAME.
709
00:40:05,260 --> 00:40:08,130
- THERE'S A REAL BELIEF
AMONGST GEOLOGISTS
710
00:40:08,200 --> 00:40:11,400
THAT THE GROWTH OF THE HIMALAYA
IN TIBET
711
00:40:11,470 --> 00:40:14,470
OVER THE LAST 60 MILLION YEARS
712
00:40:14,540 --> 00:40:17,170
HAS LED TO MAJOR CHANGES
IN THE GLOBAL CLIMATE.
713
00:40:19,570 --> 00:40:22,470
THE INDIAN MONSOON IS CREATED
714
00:40:22,540 --> 00:40:25,440
WHEN WARM AIR
FROM THE INDIAN OCEAN
715
00:40:25,510 --> 00:40:27,510
MEETS THE MOUNTAINS
OF THE HIMALAYA
716
00:40:27,580 --> 00:40:31,580
AND DUMPS THE RAIN
ON THAT MOUNTAIN FRONT.
717
00:40:31,650 --> 00:40:34,690
PRIOR TO THE FORMATION
OF THE HIMALAYA IN TIBET,
718
00:40:34,760 --> 00:40:36,360
THERE WAS NO MONSOON.
719
00:40:36,420 --> 00:40:39,090
THERE WAS NO BARRIER
TO THE NORTHWARD PROGRESS
720
00:40:39,160 --> 00:40:41,230
OF THE MOIST INDIAN OCEAN AIR.
721
00:40:44,800 --> 00:40:47,470
narrator: THE NEW MONSOON
BEGAN DUMPING RAIN AND SNOW
722
00:40:47,540 --> 00:40:51,140
ON THE GROWING MOUNTAINS
OF ASIA.
723
00:40:51,210 --> 00:40:54,070
THIS ERODED THE ROCKS
AND CHANGED THE CHEMICAL BALANCE
724
00:40:54,140 --> 00:40:57,480
IN THE ATMOSPHERE.
725
00:40:57,550 --> 00:41:01,080
MASSIVE AMOUNTS OF CO2
WERE REMOVED FROM THE AIR,
726
00:41:01,150 --> 00:41:04,780
SO MUCH THAT THE GLOBAL CLIMATE
BEGAN TO COOL.
727
00:41:07,420 --> 00:41:10,490
IT WAS THE FIRST TIME IN
HUNDREDS OF MILLIONS OF YEARS
728
00:41:10,560 --> 00:41:15,030
THAT THE EARTH'S CLIMATE
COOLED SO DEEPLY.
729
00:41:15,100 --> 00:41:18,060
BUT BEFORE WE HUMANS
MADE OUR APPEARANCE,
730
00:41:18,130 --> 00:41:21,500
PLATE TECTONICS HAD A FEW MORE
MODIFICATIONS TO MAKE.
731
00:41:24,340 --> 00:41:26,000
- ALL RIGHT, HERE.
HERE WE GO.
732
00:41:26,070 --> 00:41:27,540
narrator:
IN ANTARCTICA,
733
00:41:27,610 --> 00:41:30,910
SCIENTISTS MADE
THE STARTLING DISCOVERY
734
00:41:30,980 --> 00:41:33,450
THAT THIS LONELY CONTINENT
AT THE BOTTOM OF THE WORLD
735
00:41:33,510 --> 00:41:37,550
WAS ONCE CONNECTED TO AUSTRALIA.
736
00:41:37,620 --> 00:41:40,490
THEN 40 MILLION YEARS AGO,
737
00:41:40,550 --> 00:41:43,160
THE LAND MASSES RIFTED APART,
738
00:41:43,220 --> 00:41:47,960
COMPLETELY CHANGING
OCEAN CURRENTS IN THE REGION.
739
00:41:48,030 --> 00:41:49,730
- OVER THE LAST
40 MILLION YEARS,
740
00:41:49,800 --> 00:41:52,900
ANTARCTICA BECAME AN ISOLATED
CONTINENT DOWN THERE,
741
00:41:52,970 --> 00:41:57,800
AND SO THE CIRCUM-ANTARCTIC
CURRENT FORMED,
742
00:41:57,870 --> 00:42:00,870
WHICH ISOLATED THAT CONTINENT
SO IT COULD COOL
743
00:42:00,940 --> 00:42:02,610
AND START TO GROW AN ICE SHEET.
744
00:42:06,250 --> 00:42:07,380
narrator:
FOR THE FIRST TIME,
745
00:42:07,450 --> 00:42:09,550
ANTARCTICA BECAME FROZEN
WITH ICE,
746
00:42:09,620 --> 00:42:12,180
UP TO 15,000 FEET THICK,
747
00:42:12,250 --> 00:42:16,720
DROPPING GLOBAL TEMPERATURES
EVEN MORE.
748
00:42:16,790 --> 00:42:19,460
AND THEN,
3 MILLION YEARS AGO,
749
00:42:19,530 --> 00:42:23,360
A NEW LAND BRIDGE WELDED SOUTH
AND NORTH AMERICA TOGETHER.
750
00:42:25,600 --> 00:42:28,030
BEFORE THAT, THE TWO CONTINENTS
WERE SEPARATED
751
00:42:28,100 --> 00:42:31,870
BY THE ANCIENT PANAMA SEAWAY.
752
00:42:31,940 --> 00:42:34,610
AS PLATE TECTONICS
JOINED THEM TOGETHER,
753
00:42:34,680 --> 00:42:39,140
OCEAN CURRENTS WERE RADICALLY
REROUTED ONCE AGAIN.
754
00:42:39,210 --> 00:42:42,650
- THE GULF STREAM, INSTEAD OF
GOING INTO THE PACIFIC OCEAN,
755
00:42:42,720 --> 00:42:46,850
IT ACTUALLY WAS THEN REDIRECTED
UPWARD IN THE ATLANTIC,
756
00:42:46,920 --> 00:42:52,520
BRINGING MORE MOISTURE
UP INTO THE NORTH ATLANTIC,
757
00:42:52,590 --> 00:42:54,930
AND THAT'S A SOURCE
OF MOISTURE FOR ICE
758
00:42:55,000 --> 00:42:59,200
ON THE CONTINENTS UP THERE.
759
00:42:59,270 --> 00:43:01,800
narrator:
BY 2 1/2 MILLION YEARS AGO,
760
00:43:01,870 --> 00:43:06,040
TEMPERATURES PLUNGED SO MUCH
THAT THE PLEISTOCENE ICE AGES
761
00:43:06,110 --> 00:43:09,140
WERE TRIGGERED,
762
00:43:09,210 --> 00:43:11,140
AND IN THIS ICE AGE WORLD,
763
00:43:11,210 --> 00:43:13,680
WHEN FREEZING GLACIAL PERIODS
ALTERNATED
764
00:43:13,750 --> 00:43:16,620
WITH MUCH WARMER INTERGLACIALS,
765
00:43:16,680 --> 00:43:19,020
THE STORY OF HUMAN EVOLUTION
UNFOLDED
766
00:43:19,090 --> 00:43:21,090
IN THE EAST AFRICAN RIFT.
767
00:43:23,960 --> 00:43:27,130
[women conversing]
768
00:43:27,190 --> 00:43:29,630
HUMANS HAVE LIVED
THROUGH EIGHT MAJOR ICE AGES
769
00:43:29,700 --> 00:43:32,400
OVER THE PAST MILLION YEARS.
770
00:43:32,470 --> 00:43:36,130
THE LAST GLACIAL PERIOD
ENDED 10,000 YEARS AGO,
771
00:43:36,200 --> 00:43:41,040
AND WE ARE NOW AT THE TAIL END
OF AN INTERGLACIAL.
772
00:43:41,110 --> 00:43:44,040
THE CLIMATE HAS BEEN
WARM ON AVERAGE,
773
00:43:44,110 --> 00:43:47,110
BUT WITH ENOUGH VARIATION
TO PROFOUNDLY AFFECT PEOPLE
774
00:43:47,180 --> 00:43:51,350
AND EVEN CIVILIZATIONS.
775
00:43:51,420 --> 00:43:54,920
- ONCE WE ENTERED
THE WARM PERIOD WE'RE IN NOW
776
00:43:54,990 --> 00:43:57,860
THAT STARTED
ABOUT 10,000 YEARS AGO,
777
00:43:57,930 --> 00:44:00,990
THE CHANGES IN CLIMATE
HAVE BEEN RELATIVELY SMALLER
778
00:44:01,060 --> 00:44:03,300
THAN THE ICE AGES,
779
00:44:03,360 --> 00:44:04,960
BUT THEY'VE BEEN BIG ENOUGH
780
00:44:05,030 --> 00:44:09,300
THAT THERE WERE DROUGHTS
AND FLOODS AND COLD PERIODS
781
00:44:09,370 --> 00:44:11,400
AND LITTLE MINI ICE AGES.
782
00:44:11,470 --> 00:44:13,440
AND THAT PEOPLE
WERE STILL MIGRATING
783
00:44:13,510 --> 00:44:16,380
AND STILL HAVING TO ADAPT.
784
00:44:18,680 --> 00:44:22,380
narrator: RESEARCHERS STUDYING
PAST CLIMATE CHANGES
785
00:44:22,450 --> 00:44:24,950
IN GUATEMALA FOUND
THAT LONG DROUGHTS OCCURRED
786
00:44:25,020 --> 00:44:27,550
AT THE HEIGHT OF
THE ANCIENT MAYA CIVILIZATION,
787
00:44:27,620 --> 00:44:32,660
FROM 3,000 TO 1,000 YEARS AGO.
788
00:44:32,730 --> 00:44:34,460
THIS MAY HAVE BEEN A BIG FACTOR
789
00:44:34,530 --> 00:44:37,600
IN THE MAYA CIVILIZATION'S
MYSTERIOUS COLLAPSE.
790
00:44:42,970 --> 00:44:46,510
BECAUSE GLOBAL WARMING IS
AGAIN CREATING SERIOUS PROBLEMS
791
00:44:46,570 --> 00:44:48,640
FOR PEOPLE AND ECOSYSTEMS,
792
00:44:48,710 --> 00:44:51,840
SCIENTISTS ARE ENGAGED
IN AN URGENT EFFORT
793
00:44:51,910 --> 00:44:54,210
TO STUDY PAST CLIMATE CHANGES
794
00:44:54,280 --> 00:44:59,350
IN ORDER TO PREDICT
WHAT MIGHT HAPPEN IN THE FUTURE.
795
00:44:59,420 --> 00:45:02,350
ONE OF THEIR BEST TOOLS
IS THE STUDY OF GASES
796
00:45:02,420 --> 00:45:04,520
THAT CAUSE GLOBAL WARMING,
797
00:45:04,590 --> 00:45:09,260
ESPECIALLY CARBON DIOXIDE,
OR CO2.
798
00:45:09,330 --> 00:45:12,930
THESE GASES ARE DETECTED
IN ANCIENT GLACIAL ICE
799
00:45:13,000 --> 00:45:16,070
HUNDREDS OF THOUSANDS
OF YEARS OLD IN ANTARCTICA.
800
00:45:18,410 --> 00:45:21,210
- ATMOSPHERIC GASES
GET TRAPPED IN THE ICE,
801
00:45:21,280 --> 00:45:24,110
AND YOU GET THESE TRAPPED
BUBBLES OF ATMOSPHERE
802
00:45:24,180 --> 00:45:25,980
THAT ARE PRESERVED,
803
00:45:26,050 --> 00:45:28,680
AND SO WHEN YOU TAKE
THE ICE CORE,
804
00:45:28,750 --> 00:45:33,720
YOU HAVE THIS SORT OF
ANCIENT ATMOSPHERE.
805
00:45:33,790 --> 00:45:37,320
AND SO THEY CAN RELEASE THAT
AND MEASURE THE AMOUNT OF CO2
806
00:45:37,390 --> 00:45:38,960
THAT WAS AROUND.
807
00:45:39,030 --> 00:45:42,930
AND ALSO HOW IT CHANGED
SINCE THE LAST ICE AGE.
808
00:45:44,730 --> 00:45:48,770
SO WE KNOW FROM THE ICE CORES
THAT THE NATURAL LEVEL OF CO2
809
00:45:48,840 --> 00:45:51,340
SHOULD BE
ABOUT 280 PARTS PER MILLION,
810
00:45:51,410 --> 00:45:54,670
AND TODAY IT'S
ABOUT 390 PARTS PER MILLION,
811
00:45:54,740 --> 00:45:58,610
AS HUMANS HAVE BEEN BURNING
FOSSIL FUELS AND RELEASING CO2.
812
00:46:02,480 --> 00:46:04,120
THAT'S A REALLY BIG RISE.
813
00:46:04,180 --> 00:46:08,090
WE'VE NEVER SEEN THIS RAPID
A RISE OF CO2
814
00:46:08,160 --> 00:46:09,720
IN THE ATMOSPHERE
815
00:46:09,790 --> 00:46:12,460
OVER, YOU KNOW,
100 MILLION YEARS.
816
00:46:16,430 --> 00:46:19,830
narrator: SO IT APPEARS
THAT ONE NATURAL EARTH SYSTEM,
817
00:46:19,900 --> 00:46:21,230
THE CLIMATE,
818
00:46:21,300 --> 00:46:24,340
MAY INDEED BE ENTERING
A PERIOD OF INTENSE UPHEAVAL.
819
00:46:26,170 --> 00:46:29,010
[rumbling]
820
00:46:32,280 --> 00:46:34,750
WHAT ABOUT THE OTHER
NATURAL EARTH SYSTEMS,
821
00:46:34,820 --> 00:46:38,680
LIKE THOSE THAT CAUSE
EARTHQUAKES AND VOLCANOES?
822
00:46:38,750 --> 00:46:42,220
- ICELAND'S MOST ACTIVE VOLCANO
HAS STARTED ERUPTING.
823
00:46:42,290 --> 00:46:43,460
narrator:
HAVE ANY OF THESE
824
00:46:43,520 --> 00:46:45,860
BEGUN A PERIOD
OF INCREASED ACTIVITY?
825
00:46:45,930 --> 00:46:49,360
- HAS BEEN SPEWING ASH AND SMOKE
12 MILES INTO THE AIR.
826
00:46:51,060 --> 00:46:52,960
narrator:
LOOKING BACK 100 YEARS,
827
00:46:53,030 --> 00:46:55,430
THE NUMBER OF VOLCANIC ERUPTIONS
EACH YEAR
828
00:46:55,500 --> 00:46:58,540
HAS ACTUALLY HELD STEADY.
829
00:46:58,610 --> 00:47:02,070
- IN GENERAL, THE PUBLIC ONLY
HEARS ABOUT VOLCANIC ERUPTIONS
830
00:47:02,140 --> 00:47:06,380
WHEN THEY'RE PARTICULARLY BIG,
WHEN THEY KILL PEOPLE,
831
00:47:06,450 --> 00:47:10,650
BUT, IN FACT, THERE ARE USUALLY
COUPLE DOZEN VOLCANIC ERUPTIONS
832
00:47:10,720 --> 00:47:13,550
GOING ON EVERY MONTH.
833
00:47:13,620 --> 00:47:17,520
AND SOME VOLCANOES HAVE BEEN
ERUPTING FOR DOZENS OF YEARS,
834
00:47:17,590 --> 00:47:19,190
LIKE KILAUEA--
835
00:47:19,260 --> 00:47:23,460
OR EVEN HUNDREDS
OR THOUSANDS OF YEARS
836
00:47:23,530 --> 00:47:26,500
LIKE AETNA IN ITALY.
837
00:47:26,570 --> 00:47:28,700
SO THERE IS A LOT OF VARIATION
838
00:47:28,770 --> 00:47:33,210
IN TERMS OF SOMETIMES WE HAVE
REALLY BIG VOLCANIC ERUPTIONS,
839
00:47:33,270 --> 00:47:38,280
AND THEN WE MIGHT GO FOR MONTHS
OR YEARS WITHOUT ONE OF THOSE.
840
00:47:38,350 --> 00:47:40,410
BUT, IN FACT,
VOLCANOES ARE ERUPTING
841
00:47:40,480 --> 00:47:42,480
AROUND THE EARTH ALL THE TIME.
842
00:47:48,160 --> 00:47:51,120
narrator: A SIMILAR SCENARIO
HOLDS FOR EARTHQUAKES.
843
00:47:55,160 --> 00:47:58,200
THE NUMBER OF BIG QUAKES
GREATER THAN MAGNITUDE 7
844
00:47:58,270 --> 00:48:00,030
AVERAGES 18 PER YEAR.
845
00:48:00,100 --> 00:48:02,200
- AT LEAST 250 PEOPLE HAVE DIED
846
00:48:02,270 --> 00:48:05,070
AFTER A MAJOR EARTHQUAKE
HIT SOUTHWESTERN PAKISTAN.
847
00:48:05,140 --> 00:48:06,300
narrator:
ONE OF THESE QUAKES
848
00:48:06,370 --> 00:48:08,940
IS HIGHER THAN MAGNITUDE 8
EACH YEAR.
849
00:48:11,110 --> 00:48:16,620
THIS NUMBER HAS HELD STEADY
SINCE THE YEAR 1900.
850
00:48:16,680 --> 00:48:19,580
BUT IT MAY SEEM THAT EARTHQUAKES
HAVE BECOME MORE FREQUENT
851
00:48:19,650 --> 00:48:21,120
FOR SEVERAL REASONS.
852
00:48:21,190 --> 00:48:22,520
- YO!
853
00:48:22,590 --> 00:48:23,990
EXCUSE ME!
854
00:48:24,060 --> 00:48:27,930
narrator: FIRST, MORE ARE BEING
RECORDED AND PINPOINTED.
855
00:48:28,000 --> 00:48:32,930
MORE THAN 8,000 STATIONS
LISTEN FOR QUAKES WORLDWIDE.
856
00:48:33,000 --> 00:48:38,440
IN 1931,
THERE WERE JUST 350.
857
00:48:38,510 --> 00:48:40,570
EARTHQUAKES ALSO SEEM
MORE NUMEROUS
858
00:48:40,640 --> 00:48:42,610
BECAUSE OF THE SOARING
POPULATION
859
00:48:42,680 --> 00:48:46,110
AND NEAR-INSTANT REPORTING
OF NEWS WORLDWIDE.
860
00:48:49,320 --> 00:48:54,150
- THE EARTHQUAKE THAT KILLED
1/4 MILLION PEOPLE IN HAITI
861
00:48:54,220 --> 00:48:57,820
WOULD ONLY HAVE KILLED
1/10 THAT NUMBER 100 YEARS AGO,
862
00:48:57,890 --> 00:48:59,320
AND WE WOULDN'T HAVE KNOWN
ABOUT IT.
863
00:48:59,390 --> 00:49:01,860
- THIS IS SOME OF WHAT I SAW
ON THE STREETS.
864
00:49:01,930 --> 00:49:03,860
- NOW WE HEAR
ABOUT THESE THINGS INSTANTLY.
865
00:49:03,930 --> 00:49:06,460
WE HAVE THE LIVE FOOTAGE
OF THE TSUNAMIS
866
00:49:06,530 --> 00:49:08,470
ARRIVING ON THE JAPANESE COAST,
867
00:49:08,540 --> 00:49:09,900
AND THE WHOLE WORLD
KNOWS ABOUT IT.
868
00:49:13,270 --> 00:49:15,740
narrator: THE RECORDED NUMBER
OF TSUNAMIS HAS INCREASED
869
00:49:15,810 --> 00:49:17,910
IN THE PAST 100 YEARS,
870
00:49:17,980 --> 00:49:23,320
BUT SCIENTISTS ATTRIBUTE THIS
TO EVER-IMPROVING DETECTION.
871
00:49:23,380 --> 00:49:25,950
AND WITH BETTER WARNING SYSTEMS
BEING INSTALLED,
872
00:49:26,020 --> 00:49:30,260
THE LOSS OF LIFE IS DECREASING.
873
00:49:30,320 --> 00:49:32,720
SO DO SCIENTISTS SEE AN UPTICK
874
00:49:32,790 --> 00:49:35,260
IN INCREASED
GEOLOGICAL ACTIVITY?
875
00:49:38,170 --> 00:49:40,330
- NO, THE EARTH'S DOING
THE SAME THING
876
00:49:40,400 --> 00:49:42,570
IT'S BEEN DOING FOR BILLIONS
OF YEARS.
877
00:49:42,640 --> 00:49:44,700
WE NOTICE THE EVENTS MORE
878
00:49:44,770 --> 00:49:47,610
BECAUSE OUR MORE COMPLEX SOCIETY
879
00:49:47,670 --> 00:49:51,610
AND OUR FAR MORE
POPULATED PLANET
880
00:49:51,680 --> 00:49:54,080
ARE MUCH MORE VULNERABLE
TO THESE DISASTERS.
881
00:49:54,150 --> 00:49:57,120
[rumbling]
882
00:49:57,180 --> 00:49:59,480
THERE'S NO REAL EVIDENCE THAT
WE'RE LIVING THROUGH A PERIOD
883
00:49:59,550 --> 00:50:00,950
OF ENHANCED ACTIVITY.
884
00:50:01,020 --> 00:50:02,590
IN ANY ONE AREA,
885
00:50:02,660 --> 00:50:07,390
THERE MAY BE REGIONS WHERE
WE HAVE A FEW MORE EARTHQUAKES
886
00:50:07,460 --> 00:50:11,400
FOR A FEW HUNDRED YEARS,
AND THEN AFTER THAT CLUSTERING,
887
00:50:11,470 --> 00:50:13,600
SEISMICITY WILL DIE AWAY.
888
00:50:13,670 --> 00:50:16,470
BUT ON A PLANET-WIDE SCALE,
THERE'S NO EVIDENCE FOR THAT.
889
00:50:19,710 --> 00:50:22,710
narrator: LOOKING DEEPER
INTO EARTH'S GEOLOGIC PAST,
890
00:50:22,780 --> 00:50:24,610
FAR BIGGER UPHEAVALS
HAVE OCCURRED
891
00:50:24,680 --> 00:50:27,950
THAN ANYTHING KNOWN BY HUMANS.
892
00:50:28,020 --> 00:50:30,980
A SUPERVOLCANO
THOUSANDS OF TIMES BIGGER
893
00:50:31,050 --> 00:50:34,150
THAN THE HUGE MOUNT SAINT HELENS
ERUPTION OF 1980
894
00:50:34,220 --> 00:50:38,290
WENT OFF AT YELLOWSTONE
640,000 YEARS AGO.
895
00:50:40,360 --> 00:50:44,830
SUPERVOLCANOES ARE EXCEEDINGLY
RARE IN HUMAN TERMS.
896
00:50:44,900 --> 00:50:47,670
NONE HAVE ERUPTED
FOR 26,000 YEARS.
897
00:50:51,100 --> 00:50:54,770
EARTH'S HISTORY BOOK CHRONICLES
OTHER MASSIVE UPHEAVALS
898
00:50:54,840 --> 00:50:58,440
LIKE THE SIBERIAN TRAPS.
899
00:50:58,510 --> 00:51:03,050
THERE WAS SNOWBALL EARTH,
WHEN THE WHOLE WORLD FROZE OVER.
900
00:51:03,120 --> 00:51:04,850
IN MORE RECENT TIMES,
901
00:51:04,920 --> 00:51:07,920
OUR DISTANT ANCESTORS
EXPERIENCED THE BITTER COLD
902
00:51:07,990 --> 00:51:09,890
OF THE ICE AGES,
903
00:51:09,960 --> 00:51:13,290
WHEN CHICAGO LAY
UNDER A MILE-THICK SHEET OF ICE.
904
00:51:15,760 --> 00:51:19,560
IF PLANET EARTH WERE ACTING UP
MORE THAN USUAL RIGHT NOW,
905
00:51:19,630 --> 00:51:21,100
IT WOULD BARELY REGISTER
906
00:51:21,170 --> 00:51:23,600
IN THE ANNALS
OF MAJOR EARTHLY EVENTS.
907
00:51:25,240 --> 00:51:27,570
THE EXCEPTION IS THE CLIMATE,
908
00:51:27,640 --> 00:51:30,440
WHICH IS CHANGING IN WAYS
NEVER BEFORE SEEN
909
00:51:30,510 --> 00:51:33,280
IN THE GEOLOGIC RECORD.
910
00:51:33,350 --> 00:51:36,980
PEOPLE MAY HAVE SOME INFLUENCE
OVER THIS PROCESS,
911
00:51:37,050 --> 00:51:38,950
BUT DEEP EARTH PROCESSES
912
00:51:39,020 --> 00:51:41,820
LIKE EARTHQUAKES
AND VOLCANIC ERUPTIONS
913
00:51:41,890 --> 00:51:45,860
ARE BEYOND ANYONE'S CONTROL.
914
00:51:45,930 --> 00:51:47,560
SO SCIENTISTS ARE FOCUSING ON
915
00:51:47,630 --> 00:51:50,260
WAYS TO LIVE
WITH THESE POWERFUL FORCES
916
00:51:50,330 --> 00:51:53,530
AND REDUCE THEIR THREATS.
917
00:51:53,600 --> 00:51:55,270
- THE PUBLIC WOULD LOVE IT
IF WE COULD PROVIDE
918
00:51:55,340 --> 00:51:57,800
SHORT-TERM PREDICTIONS
OF HOURS TO DAYS
919
00:51:57,870 --> 00:52:00,510
BEFORE AN EARTHQUAKE,
AND WE CAN'T DO THAT.
920
00:52:00,570 --> 00:52:04,640
BUT WHAT WE CAN DO IS PROVIDE
LONG-TERM ESTIMATES--
921
00:52:04,710 --> 00:52:06,710
DECADAL ESTIMATES, PERHAPS.
922
00:52:06,780 --> 00:52:09,650
THAT SHOULD BE IMPORTANT TO US,
TO OUR SOCIETY,
923
00:52:09,720 --> 00:52:11,350
TO PLAN FOR THESE EVENTS.
924
00:52:11,420 --> 00:52:13,450
[bell clanging]
925
00:52:13,520 --> 00:52:16,150
IN MY LIFETIME,
THERE'S A 3/4 CHANCE
926
00:52:16,220 --> 00:52:19,960
THERE WILL BE A MAJOR EARTHQUAKE
IN THE BAY AREA WHERE I LIVE,
927
00:52:20,030 --> 00:52:22,460
AND THAT SHOULD BE ENOUGH
TO ENCOURAGE ME
928
00:52:22,530 --> 00:52:24,800
TO PLAN WISELY
FOR THAT EARTHQUAKE
929
00:52:24,870 --> 00:52:26,660
THAT I NEED TO EXPECT.
930
00:52:32,470 --> 00:52:35,510
narrator: WITH EARTHQUAKE
PREDICTIONS STILL IN THE FUTURE,
931
00:52:35,580 --> 00:52:37,510
EARTHQUAKE-PRONE JAPAN
HAS DEVELOPED
932
00:52:37,580 --> 00:52:42,250
THE WORLD'S FIRST EARTHQUAKE AND
TSUNAMI EARLY WARNING SYSTEM.
933
00:52:42,320 --> 00:52:46,890
ITS FIRST MAJOR TEST CAME WITH
THE MASSIVE EARTHQUAKE IN 2011.
934
00:52:46,950 --> 00:52:49,020
[alarm buzzing]
935
00:52:49,090 --> 00:52:51,190
RESIDENTS OF TOKYO WERE WARNED
936
00:52:51,260 --> 00:52:53,960
EIGHT TO NINE SECONDS
BEFORE THE QUAKE HIT.
937
00:52:54,030 --> 00:52:56,360
- AT 2:46 IN THE AFTERNOON.
938
00:52:56,430 --> 00:52:58,930
THE SHAKING WENT ON
FOR MORE THAN 2 MINUTES.
939
00:52:59,000 --> 00:53:00,600
- THE CLOSEST MAJOR CITY,
SENDAI...
940
00:53:00,670 --> 00:53:03,670
narrator: RESIDENTS OF THE
NEAREST COASTAL CITY OF SENDAI
941
00:53:03,740 --> 00:53:06,340
HEARD TSUNAMI WARNINGS
EIGHT MINUTES BEFORE
942
00:53:06,410 --> 00:53:08,670
THE 33-FOOT TSUNAMI CAME ASHORE.
943
00:53:11,750 --> 00:53:13,850
JAPAN'S ADVANCED STATE
OF PREPAREDNESS
944
00:53:13,910 --> 00:53:17,180
AND STRONG BUILDING CODES
WERE THE CRITICAL FACTORS
945
00:53:17,250 --> 00:53:21,550
IN SAVING COUNTLESS LIVES
DURING THIS DISASTER.
946
00:53:21,620 --> 00:53:23,020
AND THE EARLY WARNING SYSTEM
947
00:53:23,090 --> 00:53:27,130
SAVED AN UNTOLD NUMBER
OF LIVES AS WELL.
948
00:53:27,190 --> 00:53:28,030
[phone rings]
949
00:53:30,100 --> 00:53:33,630
THE JAPAN METEOROLOGICAL
AGENCIES EARLY WARNING SYSTEM
950
00:53:33,700 --> 00:53:37,170
ALSO DOUBLES AS JAPAN'S VOLCANIC
ERUPTION WARNING SYSTEM.
951
00:53:39,270 --> 00:53:43,170
ERUPTIONS ARE EASIER TO PREDICT
THAN EARTHQUAKES.
952
00:53:43,240 --> 00:53:46,040
- WE ARE GETTING BETTER
ALL THE TIME
953
00:53:46,110 --> 00:53:48,010
AT PREDICTING
VOLCANIC ERUPTIONS,
954
00:53:48,080 --> 00:53:51,820
BUT IT'S BY NO MEANS PERFECT.
955
00:53:51,890 --> 00:53:56,250
AND IT'S STILL A VERY DIFFICULT
THING TO DO.
956
00:53:56,320 --> 00:53:58,760
WE HAVE MUCH BETTER
INSTRUMENTATION.
957
00:53:58,830 --> 00:54:02,290
WE CAN MEASURE THE INFLATION
OF THE GROUND.
958
00:54:02,360 --> 00:54:05,800
SEISMOGRAPHS SEE HOW MAGMA
IS MOVING UP.
959
00:54:05,870 --> 00:54:10,030
EVEN TEMPERATURES OF FUMAROLES,
CHANGES IN THE GASES.
960
00:54:10,100 --> 00:54:12,340
SO WE ARE GETTING BETTER
ALL THE TIME.
961
00:54:21,080 --> 00:54:23,580
narrator: MEANWHILE EARTH'S
INNER AND OUTER FORCES
962
00:54:23,650 --> 00:54:27,320
WILL KEEP REWORKING THE PLANET,
963
00:54:27,390 --> 00:54:30,220
FROM THE CENTER
OF THE INNER CORE
964
00:54:30,290 --> 00:54:33,790
TO THE HIGHEST PEAKS
ON THE SURFACE.
965
00:54:33,860 --> 00:54:36,330
NO OTHER PLANET KNOWN TO US
966
00:54:36,400 --> 00:54:40,700
HAS SO MANY DIFFERENT
NATURAL FORCES AT WORK.
967
00:54:40,770 --> 00:54:42,530
THE EARTH WE SEE TODAY
968
00:54:42,600 --> 00:54:46,340
HAS BEEN 4 1/2 BILLION YEARS
IN THE MAKING
969
00:54:46,410 --> 00:54:50,240
AND HAS NEVER LOOKED
QUITE THIS WAY BEFORE,
970
00:54:50,310 --> 00:54:54,850
AND IT WILL NEVER LOOK
THE SAME AGAIN.
971
00:54:54,910 --> 00:54:58,050
- I THINK THE WAY THE EARTH
LOOKS NOW AS A PLANET
972
00:54:58,120 --> 00:55:01,520
IS UNIQUE IN HISTORY,
973
00:55:01,590 --> 00:55:04,220
AS IS ALMOST EVERY PERIOD
IN GEOLOGIC HISTORY.
974
00:55:04,290 --> 00:55:07,290
THE EARTH IS CONSTANTLY
UNDERGOING CHANGE.
975
00:55:07,360 --> 00:55:08,360
- WHAT ARE THE GREENS?
976
00:55:08,430 --> 00:55:09,630
- THE GREENS ARE COUNTRY ROADS,
977
00:55:09,700 --> 00:55:11,200
AND THE YELLOWS ARE LOCAL ROADS.
978
00:55:11,260 --> 00:55:13,330
- FROM A GEOLOGIST'S
POINT OF VIEW,
979
00:55:13,400 --> 00:55:16,430
THE EARTH IS REALLY,
REALLY INTERESTING
980
00:55:16,500 --> 00:55:21,470
BECAUSE, ON EARTH,
WE SEE ALL THE MAJOR PROCESSES
981
00:55:21,540 --> 00:55:26,310
THAT FORM THE SURFACE
OF A PLANET ACTUALLY GOING ON.
982
00:55:26,380 --> 00:55:29,410
WE HAVE VOLCANISM.
983
00:55:29,480 --> 00:55:33,450
WE HAVE IMPACT CRATERS FORMED
NOT THAT LONG AGO.
984
00:55:33,520 --> 00:55:35,450
WE HAVE AN ATMOSPHERE,
985
00:55:35,520 --> 00:55:39,420
WHICH MEANS WE HAVE
LIQUID WATER.
986
00:55:39,490 --> 00:55:43,030
WE HAVE WIND.
WE HAVE EROSION.
987
00:55:43,100 --> 00:55:45,400
WE HAVE PLATE TECTONICS ON EARTH
988
00:55:45,470 --> 00:55:49,500
WHICH APPEARS TO BE UNIQUE
IN THE SOLAR SYSTEM.
989
00:55:49,570 --> 00:55:54,740
SO IT'S VERY GEOLOGICALLY
DIVERSE AND VERY DYNAMIC.
990
00:55:54,810 --> 00:55:57,340
SO I THINK WE ARE LUCKY,
ACTUALLY, TO LIVE HERE.
991
00:56:04,280 --> 00:56:07,290
[jangly guitar music]
992
00:56:07,350 --> 00:56:15,130
¶ ¶
78597
Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.