1
00:00:03,704 --> 00:00:05,773
Narrator: IT’S HAPPENED
AT LEAST FIVE TIMES

2
00:00:05,806 --> 00:00:08,008
IN THE HISTORY OF OUR PLANET.

3
00:00:08,675 --> 00:00:11,278
MASS EXTINCTIONS.

4
00:00:11,311 --> 00:00:13,914
DEATH ON AN UNIMAGINABLE SCALE.

5
00:00:19,286 --> 00:00:21,755
Man: IT’S NOT JUST KILLING
A BUNCH OF INDIVIDUALS.

6
00:00:21,788 --> 00:00:24,357
IT’S KILLING EVERY INDIVIDUAL
IN THE SPECIES

7
00:00:24,391 --> 00:00:27,427
THAT MAKES THAT SPECIES EXTINCT.

8
00:00:27,461 --> 00:00:30,831
Narrator: THESE CATASTROPHES
WERE RAPID, GLOBAL EVENTS,

9
00:00:30,864 --> 00:00:34,901
LEAVING THEIR MARK
IN ANCIENT ROCKS.

10
00:00:34,935 --> 00:00:37,337
Man: SO WHEN YOU SEE
THE RAPID DISAPPEARANCE

11
00:00:37,371 --> 00:00:39,907
OF MASSIVE NUMBERS OF SPECIES
IN THE FOSSIL RECORD,

12
00:00:39,940 --> 00:00:42,743
THE QUESTION THAT’S PROVOKED
EVERY BIOLOGIST IS

13
00:00:42,776 --> 00:00:44,845
WHAT THE HECK HAPPENED?

14
00:00:44,878 --> 00:00:48,615
WHAT’S IT TAKE TO WIPE OUT
MOST OF THE LIFE ON THE PLANET?

15
00:00:53,487 --> 00:00:56,156
Narrator: AS SCIENTISTS HUNT
FOR CLUES AROUND THE WORLD,

16
00:00:56,189 --> 00:01:01,394
TWO OF THE GREATEST EXTINCTIONS
MAY FINALLY BE SOLVED.

17
00:01:01,428 --> 00:01:03,297
Man: MAJOR EVENTS
IN THE HISTORY OF LIFE

18
00:01:03,330 --> 00:01:07,034
HAVE COINCIDED
WITH THESE EXTINCTIONS.

19
00:01:07,067 --> 00:01:08,802
Narrator: WHAT MIGHT THESE
CALAMITIES TELL US

20
00:01:08,835 --> 00:01:10,970
ABOUT OUR FUTURE?

21
00:01:12,839 --> 00:01:17,977
ARE THE FORCES THAT RAVAGED LIFE
EONS AGO BACK AT WORK TODAY?

22
00:01:21,315 --> 00:01:25,252
Man: IF ENVIRONMENTAL CHANGE
IS GREAT ENOUGH, FAST ENOUGH,

23
00:01:25,285 --> 00:01:30,457
AND ON A GLOBAL SCALE,
THE ENTIRE PLANET IS IN TROUBLE.

24
00:01:30,490 --> 00:01:34,294
Narrator: ARE WE ON THE BRINK
OF ANOTHER MASS EXTINCTION?

25
00:01:47,808 --> 00:01:49,176
WHEN YOU WALK THROUGH

26
00:01:49,209 --> 00:01:52,012
THE SMITHSONIAN’S NATIONAL
MUSEUM OF NATURAL HISTORY,

27
00:01:52,045 --> 00:01:54,915
MUCH OF WHAT YOU SEE IS EXTINCT.

28
00:01:58,585 --> 00:02:00,554
BUT WHILE SPECIES COME AND GO,

29
00:02:00,587 --> 00:02:05,258
ON RARE OCCASIONS
THERE ARE MASS EXTINCTIONS--

30
00:02:05,292 --> 00:02:09,797
RAPID EVENTS THAT WIPE OUT
THE MAJORITY OF LIFE ON EARTH.

31
00:02:13,000 --> 00:02:16,837
THIS IS THE STORY OF TWO
OF THOSE CATASTROPHES--

32
00:02:16,870 --> 00:02:21,308
HOW THEY UNFOLDED AND WHAT THEY
CAN TELL US ABOUT OUR FUTURE.

33
00:02:24,378 --> 00:02:28,115
THE FIRST MYSTERY IS
THE DEATH OF THE DINOSAURS.

34
00:02:31,685 --> 00:02:33,720
66 MILLION YEARS AGO,

35
00:02:33,754 --> 00:02:36,090
GIANT PTEROSAURS
RULED THE SKIES.

36
00:02:36,123 --> 00:02:38,158
[SCREECH]

37
00:02:40,394 --> 00:02:41,729
WHILE BENEATH THE WAVES,

38
00:02:41,762 --> 00:02:45,299
PREDATORS CALLED MOSASAURS
PROWLED THE SEAS.

39
00:02:49,236 --> 00:02:51,939
AND DINOSAURS ROAMED THE LAND.

40
00:02:55,308 --> 00:02:56,476
[ROARS]

41
00:02:56,510 --> 00:02:59,613
THEN SUDDENLY, THEY WERE GONE.

42
00:03:02,015 --> 00:03:05,085
Man: THIS IS A FEMUR
OF A TRICERATOPS.

43
00:03:05,118 --> 00:03:07,754
Narrator: TO UNDERSTAND
THE CAUSES OF MASS EXTINCTIONS,

44
00:03:07,788 --> 00:03:10,090
EVOLUTIONARY BIOLOGIST
SEAN CARROLL

45
00:03:10,123 --> 00:03:11,257
HAS CIRCLED THE GLOBE.

46
00:03:11,291 --> 00:03:12,592
Sean Carroll:
IT’S JUST HANGING OUT,

47
00:03:12,626 --> 00:03:14,595
AND YOU’VE GOT AN EDGE-ON
VIEW OF THE BONE HERE.

48
00:03:14,628 --> 00:03:16,196
MASS EXTINCTIONS POSE
THE GREATEST

49
00:03:16,229 --> 00:03:19,265
BIOLOGICAL MURDER MYSTERIES.

50
00:03:19,299 --> 00:03:21,401
WHAT KILLED THE DINOSAURS?

51
00:03:21,435 --> 00:03:23,504
PERHAPS YOU’VE HEARD
THAT WE NOW KNOW.

52
00:03:23,537 --> 00:03:25,406
BUT HOW DO WE KNOW?

53
00:03:25,439 --> 00:03:26,807
WELL, IT REQUIRED
SOME OF THE GREATEST

54
00:03:26,840 --> 00:03:29,509
SCIENTIFIC DETECTIVE WORK EVER.

55
00:03:29,543 --> 00:03:33,047
AND THE TRAIL BEGAN ALMOST
HALFWAY AROUND THE WORLD.

56
00:03:33,080 --> 00:03:35,616
[BELL TOLLING]

57
00:03:38,085 --> 00:03:42,790
Narrator: THIS IS GUBBIO,
A SLEEPY ITALIAN TOWN.

58
00:03:42,823 --> 00:03:45,826
NOT A SINGLE GIANT REPTILE
IN SIGHT.

59
00:03:50,797 --> 00:03:54,301
STILL, THE PAST IS
EVERYWHERE YOU LOOK.

60
00:03:56,203 --> 00:04:00,541
AND BEYOND THESE WALLS,
AN EVEN DEEPER PAST IS BURIED.

61
00:04:05,712 --> 00:04:09,883
JUST OUTSIDE OF TOWN, THERE ARE
TRACES OF THE DINOSAURS’ WORLD,

62
00:04:09,916 --> 00:04:14,020
ITS HISTORY WRITTEN IN
THE LAYERS OF LIMESTONE CLIFFS.

63
00:04:17,758 --> 00:04:19,293
MILLIONS OF YEARS AGO,

64
00:04:19,326 --> 00:04:22,663
THESE ROCKS WERE AT
THE BOTTOM OF THE SEA.

65
00:04:26,600 --> 00:04:29,970
IN THE 1970s, AMERICAN GEOLOGIST
WALTER ALVAREZ

66
00:04:30,003 --> 00:04:32,439
WAS STUDYING THESE
LIMESTONE LAYERS,

67
00:04:32,472 --> 00:04:36,643
ANALYZING FOSSILS LEFT
BY TINY, SHELLED SEA CREATURES.

68
00:04:41,915 --> 00:04:45,285
CALLED FORAMINIFERA,
OR FORAMS FOR SHORT,

69
00:04:45,318 --> 00:04:48,388
THEY’RE AMONG THE MOST COMMON
OCEAN PLANKTON.

70
00:04:50,590 --> 00:04:54,427
WHEN THEY DIE, THEIR SHELLS
BECOME PART OF THE SEDIMENT

71
00:04:54,461 --> 00:04:57,631
AND CAN BE USED AS MARKERS
OF GEOLOGIC TIME.

72
00:05:00,167 --> 00:05:04,238
BUT ALVAREZ SAW
SOMETHING STRIKING.

73
00:05:04,271 --> 00:05:08,442
THEY SEEMED TO DISAPPEAR AT
THIS MYSTERIOUS LINE OF CLAY.

74
00:05:11,711 --> 00:05:13,112
Walter Alvarez:
YOU COULD SEE THAT

75
00:05:13,146 --> 00:05:18,785
IN THE TOP LAYER OF LIMESTONE,
THERE WERE FAIRLY LARGE FORAMS.

76
00:05:18,819 --> 00:05:20,788
THEN THERE’S THIS CLAY LAYER.

77
00:05:20,821 --> 00:05:23,757
AND ABOVE IT,
IN THIS LIMESTONE LAYER,

78
00:05:23,790 --> 00:05:26,793
ALMOST ALL OF THOSE FORAMS
ARE GONE.

79
00:05:26,827 --> 00:05:28,829
AND I THINK THAT
SORT OF WOKE ME UP,

80
00:05:28,862 --> 00:05:32,632
BECAUSE THAT EXTINCTION OF
FORAMS, AS CLOSE AS WE CAN TELL,

81
00:05:32,666 --> 00:05:36,170
IT’S THE SAME AGE AS
THE EXTINCTION OF THE DINOSAURS.

82
00:05:38,338 --> 00:05:40,440
Narrator:
ALMOST 1,000 MILES AWAY,

83
00:05:40,473 --> 00:05:42,709
THERE WAS A SIMILAR PATTERN.

84
00:05:51,418 --> 00:05:53,453
ON THE ATLANTIC COAST OF SPAIN,

85
00:05:53,486 --> 00:05:58,691
DUTCH GEOLOGIST JAN SMIT
WAS STUDYING FORAMS AS WELL.

86
00:05:58,725 --> 00:06:02,229
THEIR FOSSILIZED SHELLS
FORMED THESE LIMESTONE CLIFFS,

87
00:06:02,262 --> 00:06:05,766
JUST LIKE IN GUBBIO.

88
00:06:05,799 --> 00:06:07,901
Carroll: SO RIGHT THERE
TOWARDS THE BOUNDARY?

89
00:06:07,934 --> 00:06:10,136
Jan Smit: RIGHT THERE
IS THE BOUNDARY.

90
00:06:10,170 --> 00:06:12,239
Narrator: THEY REPRESENT
THE GEOLOGICAL PERIOD

91
00:06:12,272 --> 00:06:15,208
WHEN DINOSAURS LAST
WALKED THE EARTH.

92
00:06:17,444 --> 00:06:21,381
AND LIKE ALVAREZ, SMIT FOUND
A PUZZLING CLAY LAYER

93
00:06:21,414 --> 00:06:24,384
MARKING THE EXTINCTION
OF THE FORAMS.

94
00:06:28,822 --> 00:06:31,058
Carroll: JAN, WHAT CAN WE TELL
ABOUT EARTH’S HISTORY

95
00:06:31,091 --> 00:06:32,993
FROM JUST LOOKING
AT THESE ROCKS?

96
00:06:33,026 --> 00:06:36,329
Smit: WELL, YOU CAN SEE
THE END OF THE ONE WORLD

97
00:06:36,363 --> 00:06:38,498
AND THE BEGINNING
OF THE NEXT ONE.

98
00:06:38,531 --> 00:06:40,900
AND YOU SEE THERE IS
A VERY SHARP,

99
00:06:40,934 --> 00:06:43,603
EXTREMELY SHARP DIVIDING LINE
BETWEEN THE TWO.

100
00:06:43,637 --> 00:06:44,805
Carroll: THAT GRAY BAND.

101
00:06:44,838 --> 00:06:46,440
Smit: THAT’S THAT GRAY BAND
OVER THERE.

102
00:06:46,473 --> 00:06:49,543
AND ALL OF A SUDDEN WE SEE
A DRAMATIC CHANGE,

103
00:06:49,576 --> 00:06:51,978
WHICH WE CALL THE KT BOUNDARY.

104
00:06:56,116 --> 00:06:57,651
Narrator: THE KT BOUNDARY
LIES BETWEEN

105
00:06:57,684 --> 00:07:01,254
TWO GREAT AGES OF ANIMAL LIFE--

106
00:07:01,288 --> 00:07:04,291
THE AGE OF REPTILES,
WITH DINOSAURS,

107
00:07:04,324 --> 00:07:09,062
AND THE AGE OF MAMMALS,
AFTER THE DINOSAURS WERE GONE.

108
00:07:09,095 --> 00:07:10,430
Smit: AND THE KT BOUNDARY,

109
00:07:10,463 --> 00:07:12,398
IT’S RIGHT HERE WHERE
YOU SEE A CONTRAST

110
00:07:12,432 --> 00:07:15,101
BETWEEN THE PURPLE AND THE DARK.

111
00:07:15,135 --> 00:07:17,237
SO HERE’S PLENTY OF LIFE.

112
00:07:17,270 --> 00:07:19,105
AND THERE, THE BASE
OF THE FOOD CHAIN

113
00:07:19,139 --> 00:07:21,141
OF THE OCEANS DISAPPEAR,

114
00:07:21,174 --> 00:07:22,876
AND EVERYTHING WHICH
IS DEPENDENT ON IT

115
00:07:22,909 --> 00:07:26,045
IS TOTALLY ZAPPED
RIGHT AT THE BOUNDARY.

116
00:07:27,314 --> 00:07:29,349
Narrator: VARYING IN COLOR
AND THICKNESS,

117
00:07:29,382 --> 00:07:35,188
THE LAYER WAS FOUND
AROUND THE WORLD.

118
00:07:35,221 --> 00:07:38,257
WALTER ALVAREZ BELIEVED
IT WAS A SILENT WITNESS

119
00:07:38,291 --> 00:07:40,860
TO THE END OF THE DINOSAURS.

120
00:07:40,894 --> 00:07:42,729
Alvarez: AND THAT’S WHAT’S
BEAUTIFUL ABOUT ROCKS,

121
00:07:42,762 --> 00:07:46,132
IS THAT THEY LIE THERE
FOR MILLIONS OF YEARS

122
00:07:46,166 --> 00:07:47,434
AND DON’T CHANGE.

123
00:07:47,467 --> 00:07:51,504
AND THEY REMEMBER WHAT HAPPENED
WHEN THEY WERE FORMED.

124
00:07:53,940 --> 00:07:55,341
Narrator: TO UNLOCK
THOSE MEMORIES,

125
00:07:55,375 --> 00:07:56,743
ALVAREZ SOUGHT HELP

126
00:07:56,776 --> 00:08:00,213
AT THE UNIVERSITY OF CALIFORNIA
AT BERKELEY

127
00:08:00,246 --> 00:08:03,049
FROM A NOBEL PRIZE-WINNING
PHYSICIST--

128
00:08:03,083 --> 00:08:06,186
HIS FATHER, LUIS ALVAREZ.

129
00:08:08,621 --> 00:08:10,590
Richard Muller: ALVAREZ LOOKED
AT THIS LAYER,

130
00:08:10,623 --> 00:08:12,692
AND HE THOUGHT THERE
MUST BE CLUES THERE.

131
00:08:12,726 --> 00:08:15,462
IT WAS LIKE SHERLOCK HOLMES
SEEING SOMETHING ODD.

132
00:08:15,495 --> 00:08:20,367
HE WANTED TO KNOW EVERYTHING
HE COULD KNOW ABOUT THAT LAYER.

133
00:08:20,400 --> 00:08:26,206
Narrator: ALVAREZ AND HIS SON
HUNTED FOR CHEMICAL CLUES.

134
00:08:26,239 --> 00:08:30,143
WHAT THEY FOUND STUNNED THEM.

135
00:08:30,176 --> 00:08:32,078
THE CLAY CONTAINED HIGH LEVELS
OF AN ELEMENT

136
00:08:32,112 --> 00:08:35,782
RARELY FOUND IN
THE EARTH’S CRUST--IRIDIUM.

137
00:08:38,218 --> 00:08:42,589
OTHER KT SITES HAD
IRIDIUM SPIKES JUST AS HIGH.

138
00:08:42,622 --> 00:08:45,692
LUIS ALVAREZ THOUGHT
HE KNEW WHY.

139
00:08:51,331 --> 00:08:54,067
THOUSANDS OF ASTEROIDS
CROSS THE EARTH’S ORBIT,

140
00:08:54,100 --> 00:08:57,637
AND MANY CONTAIN IRIDIUM.

141
00:08:57,670 --> 00:09:02,308
WHAT IF ONE HIT THE EARTH
66 MILLION YEARS AGO?

142
00:09:04,110 --> 00:09:07,046
Muller: SO LUIS ALVAREZ
HAD THIS HYPOTHESIS

143
00:09:07,080 --> 00:09:10,283
THAT AN ASTEROID WOULD CAUSE
THIS DESTRUCTION.

144
00:09:10,316 --> 00:09:13,052
HE HAD THE CLUE--THE AMOUNT
OF IRIDIUM AT GUBBIO.

145
00:09:13,086 --> 00:09:16,089
UNDER THIS HYPOTHESIS, IT WOULD
BE SPREAD ALL AROUND THE WORLD.

146
00:09:16,122 --> 00:09:19,392
SO NOW HE COULD CALCULATE
HOW MUCH IRIDIUM

147
00:09:19,426 --> 00:09:22,195
THERE HAD BEEN LAID DOWN
OVER THE ENTIRE EARTH.

148
00:09:22,228 --> 00:09:23,529
NOW, HE ALSO KNEW
HOW MUCH IRIDIUM

149
00:09:23,563 --> 00:09:25,698
THERE IS IN ASTEROIDS
AND COMETS.

150
00:09:25,732 --> 00:09:30,036
SO HE CAN NOW CALCULATE
THE SIZE OF THE OBJECT.

151
00:09:35,008 --> 00:09:37,677
Narrator: THE ASTEROID
WAS SIX MILES WIDE,

152
00:09:37,710 --> 00:09:42,481
WEIGHING HUNDREDS
OF BILLIONS OF TONS.

153
00:09:42,515 --> 00:09:46,252
STILL, COMPARED TO EARTH,
IT WAS TINY.

154
00:09:46,286 --> 00:09:48,789
HOW COULD IT WREAK SUCH HAVOC?

155
00:09:53,359 --> 00:09:57,697
IT WOULD HAVE HIT AT NEARLY
50,000 MILES PER HOUR.

156
00:10:01,434 --> 00:10:03,269
THE ENERGY RELEASED
WOULD BE EQUAL TO

157
00:10:03,303 --> 00:10:06,473
ABOUT 100 MILLION NUCLEAR BOMBS.

158
00:10:09,008 --> 00:10:11,344
[DINOSAUR GROANS]

159
00:10:13,980 --> 00:10:16,483
A HUGE MASS OF
SUPERHEATED DEBRIS

160
00:10:16,516 --> 00:10:18,651
WOULD HAVE BEEN BLASTED
INTO SPACE,

161
00:10:18,685 --> 00:10:22,088
ORBITING THE EARTH BEFORE
RAINING BACK DOWN.

162
00:10:25,825 --> 00:10:28,761
THE ALVAREZES THOUGHT THE DUST
COULD HAVE BLOCKED OUT THE SUN

163
00:10:28,795 --> 00:10:31,865
FOR YEARS, DEVASTATING LIFE.

164
00:10:33,867 --> 00:10:39,940
THIS WAS THE HYPOTHESIS FOR HOW
THE AGE OF DINOSAURS ENDED...

165
00:10:39,973 --> 00:10:42,342
BUT THERE WAS A PROBLEM.

166
00:10:46,179 --> 00:10:48,148
IF AN ASTEROID
SIX MILES IN DIAMETER

167
00:10:48,181 --> 00:10:49,549
DID STRIKE THE EARTH,

168
00:10:49,582 --> 00:10:54,020
WHERE WAS THE CRATER OF
THE RIGHT AGE, TYPE AND SIZE?

169
00:10:59,325 --> 00:11:02,728
[TRAIN WHISTLE BLOWS]

170
00:11:07,233 --> 00:11:08,835
ONE OF THE MOST PROMISING LEADS

171
00:11:08,868 --> 00:11:11,003
WAS DISCOVERED ALONG
THE BRAZOS RIVER,

172
00:11:11,037 --> 00:11:14,240
NEARLY 200 MILES
FROM THE GULF OF MEXICO.

173
00:11:19,746 --> 00:11:24,017
66 MILLION YEARS AGO,
THIS WAS THE BOTTOM OF THE SEA.

174
00:11:26,219 --> 00:11:28,254
[COW GRUNTS]

175
00:11:30,490 --> 00:11:33,426
Alan Hildebrand: IT’S ACTUALLY
EASIER WITH FRESH TRACKS.

176
00:11:33,459 --> 00:11:36,429
Narrator: IN THE 1980s,
GEOLOGIST ALAN HILDEBRAND

177
00:11:36,462 --> 00:11:39,098
CAME TO INVESTIGATE
AN ODD MIXTURE OF ROCKS

178
00:11:39,132 --> 00:11:41,334
AT THE KT BOUNDARY HERE.

179
00:11:48,841 --> 00:11:51,277
Carroll: SO, THIS IS THE TYPICAL
MUD JUST FOUND IN THIS AREA?

180
00:11:51,311 --> 00:11:52,546
Hildebrand: EXACTLY.

181
00:11:52,579 --> 00:11:55,348
ALL WE SEE IS SEVEN MILLION
YEARS OF THIS MUD HERE.

182
00:11:55,381 --> 00:11:59,051
SO, I MEAN,
WE’RE TALKING BORING.

183
00:11:59,085 --> 00:12:02,388
Narrator: BUT THIS MUD WAS
FULL OF PROTRUDING BOULDERS

184
00:12:02,422 --> 00:12:04,524
RIGHT AT THE BOUNDARY.

185
00:12:06,593 --> 00:12:08,628
Carroll: SO YOU HAVE THIS
REALLY REGULAR MUD LAYER,

186
00:12:08,661 --> 00:12:11,531
AND THEN ALL OF A SUDDEN,
THIS AREA THAT’S JUST FULL

187
00:12:11,564 --> 00:12:13,633
OF THIS WHOLE MIXTURE
OF BOULDERS AND...

188
00:12:13,666 --> 00:12:15,067
Hildebrand:
AND FROM DIFFERENT PLACES.

189
00:12:15,101 --> 00:12:17,136
IT ISN’T JUST THE ROCK
THAT WAS HERE IN THE SEAFLOOR.

190
00:12:17,170 --> 00:12:18,905
MAYBE SOME OF IT GOT PULLED
FROM DEEP WATER,

191
00:12:18,938 --> 00:12:20,406
MAYBE SOME OF IT GOT
PULLED FROM SHALLOW WATER.

192
00:12:20,440 --> 00:12:22,342
IT ALL GOT JUMBLED TOGETHER
AND DUMPED HERE.

193
00:12:22,375 --> 00:12:24,143
Carroll: ALRIGHT, SO WHAT COULD
HAVE HAPPENED HERE

194
00:12:24,177 --> 00:12:25,945
THAT WOULD EXPLAIN SOMETHING
SO DRAMATIC?

195
00:12:25,979 --> 00:12:28,348
Hildebrand: WELL, IT HAD TO BE
A HUGELY ENERGETIC WAVE

196
00:12:28,381 --> 00:12:30,416
IN THE OCEAN, A GIANT TSUNAMI.

197
00:12:35,021 --> 00:12:37,190
Narrator:
AN ASTEROID SIX MILES WIDE

198
00:12:37,223 --> 00:12:40,827
WOULD HAVE CAUSED TSUNAMIS
HUNDREDS OF FEET HIGH.

199
00:12:42,462 --> 00:12:44,197
TRAVELING AT THE SPEED OF A JET,

200
00:12:44,230 --> 00:12:46,699
THEY WOULD HAVE RIPPED UP
THE SEAFLOOR,

201
00:12:46,733 --> 00:12:50,036
LEAVING DEBRIS IN
THE BRAZOS RIVER BASIN.

202
00:12:54,607 --> 00:12:56,943
HILDEBRAND REALIZED THE STRIKE
MUST HAVE OCCURRED

203
00:12:56,976 --> 00:12:59,479
NEAR THE GULF OF MEXICO.

204
00:12:59,512 --> 00:13:02,749
BUT WHERE?

205
00:13:02,782 --> 00:13:04,784
THE BREAKTHROUGH CAME
WHEN HE FOUND A MAP

206
00:13:04,817 --> 00:13:08,587
MADE BY GEOLOGISTS
SEARCHING FOR OIL.

207
00:13:08,621 --> 00:13:10,723
IT REVEALED
A GIANT BURIED CRATER

208
00:13:10,757 --> 00:13:12,993
ON THE YUCATAN PENINSULA.

209
00:13:16,663 --> 00:13:20,167
DISCOVERED IN 1990,
IT WAS NAMED CHICXULUB,

210
00:13:20,199 --> 00:13:23,502
AFTER A VILLAGE NEAR ITS CENTER.

211
00:13:23,536 --> 00:13:24,837
Carroll: THE DISCOVERY
OF THE CHICXULUB CRATER

212
00:13:24,871 --> 00:13:27,774
WAS THE ULTIMATE EVIDENCE
OF THE ASTEROID IMPACT.

213
00:13:27,807 --> 00:13:31,811
MOREOVER, THE CRATER WAS
THE SAME AGE AS THE KT BOUNDARY,

214
00:13:31,844 --> 00:13:34,780
AND IT WAS THE SIZE PREDICTED
BY LUIS ALVAREZ.

215
00:13:34,814 --> 00:13:38,117
WE NOW KNEW FOR CERTAIN WHAT
HAPPENED ON THAT HORRIBLE DAY.

216
00:13:45,158 --> 00:13:47,027
I LOVE THAT LITTLE ROCK
SITTING UP OVER THERE.

217
00:13:47,060 --> 00:13:49,563
Kirk Johnson: YEAH,
THAT LITTLE CAP UP THERE.

218
00:13:49,595 --> 00:13:50,796
Narrator: ALTHOUGH THE TRIGGER
FOR THE EXTINCTION

219
00:13:50,830 --> 00:13:52,231
HAD BEEN FOUND,

220
00:13:52,265 --> 00:13:54,400
KEY QUESTIONS REMAINED.

221
00:13:56,536 --> 00:13:59,172
HOW DID A SINGLE IMPACT
IN THE YUCATAN

222
00:13:59,205 --> 00:14:03,676
WIPE OUT SO MUCH LIFE
ACROSS EARTH?

223
00:14:03,710 --> 00:14:05,912
WHICH SPECIES VANISHED?

224
00:14:05,945 --> 00:14:09,649
HOW DID THE WORLD CHANGE?

225
00:14:09,682 --> 00:14:10,783
ANSWERS WERE FOUND

226
00:14:10,817 --> 00:14:13,753
IN THE BADLANDS OF THE DAKOTAS
AND MONTANA,

227
00:14:13,786 --> 00:14:15,888
IN THE HELL CREEK FORMATION.

228
00:14:21,227 --> 00:14:24,697
ITS ERODING BUTTES HOLD FOSSILS
OF PLANTS AND ANIMALS

229
00:14:24,731 --> 00:14:28,501
THAT LIVED DURING THE AGE
OF THE DINOSAURS AND BEYOND.

230
00:14:32,672 --> 00:14:36,442
WHEN PALEONTOLOGIST KIRK JOHNSON
FOUND THE BOUNDARY HERE,

231
00:14:36,476 --> 00:14:40,580
HE COULD STUDY THE SCOPE OF THE
EXTINCTION FAR FROM THE IMPACT.

232
00:14:42,115 --> 00:14:44,451
Carroll: KIRK, HOW IMPORTANT
WAS IT TO FIND THE KT BOUNDARY

233
00:14:44,484 --> 00:14:46,252
UP HERE IN NORTH DAKOTA?

234
00:14:46,285 --> 00:14:47,720
Johnson: IF YOU CAN PUT
YOUR FINGER ON THE BOUNDARY

235
00:14:47,754 --> 00:14:49,689
LIKE YOU CAN RIGHT HERE,

236
00:14:49,722 --> 00:14:52,325
WHAT THAT MEANS IS YOU CAN ASK
THE VERY SIMPLE QUESTION,

237
00:14:52,358 --> 00:14:54,427
HOW WAS LIFE BEFORE THE IMPACT

238
00:14:54,460 --> 00:14:57,296
DIFFERENT FROM LIFE
AFTER THE IMPACT?

239
00:14:57,330 --> 00:14:59,265
ALL YOU GOT TO DO IS LOOK
FOR THE FOSSILS BELOW

240
00:14:59,298 --> 00:15:00,766
AND COMPARE THEM TO
THE FOSSILS ABOVE.

241
00:15:00,800 --> 00:15:05,371
AND THAT’S WHAT WE’VE DONE HERE
FOR THE LAST 30 YEARS.

242
00:15:05,405 --> 00:15:11,444
Narrator: THIS ARID LANDSCAPE
WAS ONCE A WET, LUSH FOREST.

243
00:15:11,477 --> 00:15:14,647
CRACK OPEN SOME ROCKS, AND
YOU’LL SEE THE LEAVES OF TREES

244
00:15:14,680 --> 00:15:18,951
THAT FLOURISHED HERE
OVER 66 MILLION YEARS AGO.

245
00:15:18,985 --> 00:15:21,754
Carroll: THERE IT IS.
LOOK AT THAT.

246
00:15:21,788 --> 00:15:24,124
Narrator: LOOK CLOSELY
AND YOU CAN FIND FOSSILS

247
00:15:24,157 --> 00:15:26,993
OF TURTLES, FISH,
AND SMALL MAMMALS

248
00:15:27,026 --> 00:15:31,564
THAT THRIVED IN THE RIVERS
AND FORESTS.

249
00:15:31,597 --> 00:15:35,101
AND THEN THERE ARE THE BONES
OF THE DINOSAURS.

250
00:15:35,134 --> 00:15:39,405
Johnson: SO THIS IS A PLASTERED
FEMUR OF A TRICERATOPS,

251
00:15:39,439 --> 00:15:43,209
SO AROUND THE CORNER IS
A TRICERATOPS SACRUM.

252
00:15:43,242 --> 00:15:45,177
Narrator: THE CLUES
TO WHAT HAPPENED HERE

253
00:15:45,211 --> 00:15:48,948
LIE IN THE FOSSILS
AND WHERE THEY’RE FOUND.

254
00:15:48,981 --> 00:15:52,084
Johnson: THIS IS AN ANKLEBONE OF
A SMALL, MEAT-EATING DINOSAUR.

255
00:15:52,118 --> 00:15:54,053
AND NEARBY WE FOUND THIS BONE,

256
00:15:54,086 --> 00:15:56,455
WHICH IS A BONE OF A MUCH LARGER
MEAT-EATING DINOSAUR.

257
00:15:56,489 --> 00:15:58,424
SAME BONE.
SEE THE SIZE DIFFERENCE?

258
00:15:58,458 --> 00:15:59,826
Carroll: RIGHT.

259
00:15:59,859 --> 00:16:02,195
Johnson: AND YOU FIND THESE
BONES, IDENTIFY THE ANIMAL,

260
00:16:02,228 --> 00:16:04,297
AND PRETTY SOON YOU START
ASSEMBLING A LIST OF DINOSAURS

261
00:16:04,330 --> 00:16:06,232
THAT ARE PRESENT
AT ANY GIVEN LEVEL.

262
00:16:06,265 --> 00:16:08,267
AND THE CLOSER TO THE BOUNDARY
YOU ARE,

263
00:16:08,301 --> 00:16:09,469
THE MORE WE ADDRESS THE QUESTION

264
00:16:09,502 --> 00:16:13,773
OF HOW LONG
THE DINOSAURS SURVIVED.

265
00:16:13,806 --> 00:16:16,275
Narrator: WE NOW KNOW
THAT 22 TYPES OF DINOSAURS

266
00:16:16,309 --> 00:16:21,281
LIVED IN HELL CREEK, INCLUDING
THE MIGHTY TYRANNOSAURUS REX.

267
00:16:23,616 --> 00:16:28,387
IF SOME SURVIVED, THEIR FOSSILS
WOULD LIE ABOVE THE BOUNDARY.

268
00:16:31,858 --> 00:16:33,226
Johnson: WE’VE NOW FOUND
SEVERAL SPECIMENS

269
00:16:33,259 --> 00:16:35,027
THAT ARE VERY CLOSE
TO THE BOUNDARY.

270
00:16:35,061 --> 00:16:36,229
AND REALLY WHAT
THAT’S SHOWING US

271
00:16:36,262 --> 00:16:38,464
IS THAT EVEN IF
DINOSAURS ARE RARE,

272
00:16:38,498 --> 00:16:40,500
IF YOU LOOK LONG ENOUGH,

273
00:16:40,533 --> 00:16:44,537
YOU’LL FIND THEM WHEN THEY
WERE LIVING ON THE PLANET.

274
00:16:44,570 --> 00:16:48,040
WHAT WE HAVE NOT FOUND YET
IS ANY DINOSAUR SKELETON

275
00:16:48,074 --> 00:16:53,212
ANYWHERE IN THE WORLD
ABOVE THE KT BOUNDARY LAYER.

276
00:16:53,246 --> 00:16:55,348
Narrator:
SO NO DINOSAUR SURVIVED

277
00:16:55,381 --> 00:16:58,150
THE AFTERMATH OF THE IMPACT.

278
00:16:58,184 --> 00:17:02,588
NEITHER DID 50% TO 60%
OF OTHER SPECIES.

279
00:17:04,257 --> 00:17:08,328
THE CATASTROPHE WAS EVEN WORSE
THAN THE ALVAREZES HAD IMAGINED.

280
00:17:11,898 --> 00:17:15,802
WITHIN 600 MILES OF THE IMPACT,
DEATH CAME QUICKLY.

281
00:17:21,274 --> 00:17:25,178
Brian Toon: IF YOU TURN YOUR
OVEN ON BROIL, OPEN THE DOOR,

282
00:17:25,211 --> 00:17:27,146
PUT YOUR HAND
UNDER THE GLOW BAR,

283
00:17:27,179 --> 00:17:30,049
THAT’S WHAT THE DINOSAURS FELT
VERY SOON.

284
00:17:30,082 --> 00:17:34,320
AND THEY WERE PROBABLY BROILED
ALIVE WITHIN AN HOUR OR SO.

285
00:17:36,188 --> 00:17:41,193
Narrator: WHAT HAPPENED NEXT
WAS A CHAIN REACTION.

286
00:17:41,227 --> 00:17:43,996
FALLING EJECTA IGNITED FIRES.

287
00:17:46,165 --> 00:17:51,804
SOOT AT KT BOUNDARIES SHOWS THAT
NEARLY THE ENTIRE WORLD BURNED.

288
00:17:52,772 --> 00:17:55,341
SMOKE FILLED THE SKIES.

289
00:17:57,410 --> 00:17:58,678
[ROARS]

290
00:17:58,711 --> 00:18:00,446
Toon: AND THERE MAY HAVE ALSO
BEEN A LOT OF SULFUR

291
00:18:00,479 --> 00:18:01,680
BLOWN INTO THE ATMOSPHERE,

292
00:18:01,714 --> 00:18:04,483
BECAUSE THE IMPACT SITE
IN THE YUCATAN PENINSULA

293
00:18:04,517 --> 00:18:06,252
HAD A LOT OF SULFUR IN IT.

294
00:18:06,285 --> 00:18:09,088
AND ALL OF THOSE THINGS
WERE ABUNDANT ENOUGH

295
00:18:09,121 --> 00:18:11,423
TO OBLITERATE THE SUN.

296
00:18:13,693 --> 00:18:15,094
Narrator: THE DESTRUCTION
TRIGGERED

297
00:18:15,127 --> 00:18:19,331
A GLOBAL ECOLOGICAL COLLAPSE.

298
00:18:19,365 --> 00:18:23,903
ACID RAIN DECIMATED PLANTS,
THE BASE OF THE FOOD CHAIN.

299
00:18:25,371 --> 00:18:27,907
TOXIC GASES
RELEASED BY THE IMPACT

300
00:18:27,940 --> 00:18:29,442
DESTROYED THE OZONE LAYER

301
00:18:29,475 --> 00:18:32,678
THAT PROTECTS THE PLANET
FROM SOLAR RADIATION.

302
00:18:35,181 --> 00:18:39,085
WITH HABITATS DESTROYED AND
THE CLIMATE RADICALLY CHANGED,

303
00:18:39,118 --> 00:18:42,221
THE AGE OF DINOSAURS WAS OVER.

304
00:18:43,856 --> 00:18:45,424
BUT AS SCIENTISTS WOULD LEARN,

305
00:18:45,458 --> 00:18:48,962
THERE’S MORE THAN ONE WAY
TO PUSH LIFE TO THE BRINK.

306
00:18:58,004 --> 00:19:01,574
SINCE AN ASTEROID STRIKE
ENDED THE AGE OF DINOSAURS,

307
00:19:01,607 --> 00:19:03,442
SCIENTISTS WONDERED IF IMPACTS

308
00:19:03,476 --> 00:19:06,346
COULD HAVE CAUSED
OTHER MASS EXTINCTIONS.

309
00:19:09,081 --> 00:19:11,250
AT METEOR CRATER IN ARIZONA,

310
00:19:11,283 --> 00:19:16,288
SEAN CARROLL AND GEOPHYSICIST
JAY MELOSH PONDER THE QUESTION.

311
00:19:19,525 --> 00:19:22,395
Carroll: SO, JAY, ABOUT HOW MANY
TIMES HAS THE EARTH BEEN HIT

312
00:19:22,428 --> 00:19:26,499
BY AN ASTEROID LARGE ENOUGH
TO CAUSE A CRATER THIS BIG?

313
00:19:26,532 --> 00:19:28,567
Jay Melosh: WE LIVE
IN A SHOOTING GALLERY.

314
00:19:28,601 --> 00:19:31,037
THERE ARE THOUSANDS OF ASTEROIDS

315
00:19:31,070 --> 00:19:33,506
THAT CREATED THIS CRATER
AND MUCH BIGGER

316
00:19:33,539 --> 00:19:35,207
CROSSING THE EARTH’S ORBIT.

317
00:19:35,241 --> 00:19:38,077
THE QUESTION IS HOW OFTEN
DO WE GET HIT BY SOMETHING

318
00:19:38,110 --> 00:19:41,780
BIG ENOUGH TO CAUSE
A MASS EXTINCTION?

319
00:19:41,814 --> 00:19:45,685
Narrator: THE ANSWER IS
VERY SELDOM.

320
00:19:45,718 --> 00:19:49,121
AFTER MUCH SEARCHING,
SCIENTISTS FOUND NO EVIDENCE

321
00:19:49,155 --> 00:19:53,092
LINKING AN ASTEROID STRIKE
TO ANY OTHER EXTINCTION EVENT.

322
00:19:57,296 --> 00:20:01,066
THERE HAVE BEEN AT LEAST
FOUR OTHER MASS EXTINCTIONS.

323
00:20:01,100 --> 00:20:03,402
SO WHAT COULD EXPLAIN THEM?

324
00:20:03,436 --> 00:20:07,440
ESPECIALLY THE MOST DEVASTATING,
WHICH ENDED THE PERMIAN PERIOD,

325
00:20:07,473 --> 00:20:10,743
LONG BEFORE
THE RISE OF DINOSAURS.

326
00:20:13,546 --> 00:20:18,684
ALMOST 90% OF THE PLANET’S
SPECIES VANISHED.

327
00:20:18,718 --> 00:20:21,921
THAT’S WHY IT’S CALLED
THE GREAT DYING.

328
00:20:28,194 --> 00:20:32,865
IN CONTRAST TO OUR WORLD,
THE PERMIAN WAS AN ALIEN PLACE.

329
00:20:34,834 --> 00:20:39,305
THE EARTH HAD ONE SUPERCONTINENT
KNOWN AS PANGAEA.

330
00:20:42,875 --> 00:20:45,845
THE OCEAN WAS TEEMING WITH LIFE.

331
00:20:48,114 --> 00:20:53,553
THERE WERE TRILOBITES,
WHICH HAD SURVIVED FOR EONS,

332
00:20:53,586 --> 00:20:55,755
AND CREATURES LIKE
THE HELICOPRION,

333
00:20:55,788 --> 00:20:57,957
WITH ITS SAW-LIKE JAW.

334
00:21:01,160 --> 00:21:02,862
THERE WERE NO DINOSAURS YET,

335
00:21:02,895 --> 00:21:05,398
BUT CARNIVORES LIKE
THE GORGONOPSIDS,

336
00:21:05,431 --> 00:21:08,968
THE FIRST ANIMALS TO EVOLVE
SABER-LIKE TEETH.

337
00:21:13,038 --> 00:21:16,475
AND PLANT-EATERS
LIKE THE DICYNODONTS...

338
00:21:16,509 --> 00:21:17,877
[RASPING]

339
00:21:17,910 --> 00:21:20,479
...SO COMMON, THEIR FOSSILS
HAVE BEEN FOUND EVERYWHERE.

340
00:21:20,513 --> 00:21:23,349
[ROARS]

341
00:21:23,382 --> 00:21:29,188
THEN, SUDDENLY, THE WORLD WAS
ALMOST EMPTIED OF CREATURES.

342
00:21:29,221 --> 00:21:31,390
WHAT COULD EXPLAIN IT?

343
00:21:36,896 --> 00:21:38,364
IN SOUTHERN CHINA,

344
00:21:38,397 --> 00:21:42,768
KEY CLUES LIE BURIED BEYOND
THESE ANCIENT MOUNTAINS.

345
00:21:47,373 --> 00:21:50,810
HERE, SCIENTISTS ARE SEARCHING
FOR VICTIMS OF THE GREAT DYING

346
00:21:50,843 --> 00:21:53,379
ON THE BANKS OF THE RED RIVER.

347
00:21:55,414 --> 00:21:57,249
Shuzhong Shen: WHOA! BEAUTIFUL!

348
00:21:57,283 --> 00:21:59,252
Narrator: UNEARTHING FOSSILS
FROM THE EXTINCTION

349
00:21:59,285 --> 00:22:02,922
IS THE LIFE’S WORK OF
PALEONTOLOGIST SHUZHONG SHEN.

350
00:22:02,955 --> 00:22:04,089
Shen: THIS ONE’S DIFFERENT,

351
00:22:04,123 --> 00:22:07,660
BUT THOSE THREE MAY BE
THE SAME THING.

352
00:22:07,693 --> 00:22:11,764
Narrator: HE’S DOCUMENTING WHICH
CREATURES LIVED AND DIED HERE.

353
00:22:14,333 --> 00:22:16,068
Shen, translated:
AFTER TEN YEARS OF WORK,

354
00:22:16,101 --> 00:22:18,270
WE’VE DISCOVERED THAT
THIS CROSS SECTION

355
00:22:18,304 --> 00:22:21,674
HAS RECORDED THE ENTIRE PROCESS
OF THE MASS EXTINCTION.

356
00:22:21,707 --> 00:22:24,810
THE DIVERSITY OF CREATURES
THAT THRIVED IN THE PERMIAN,

357
00:22:24,844 --> 00:22:28,114
AND THE SUDDEN POINT WHERE
THEY DISAPPEARED QUICKLY.

358
00:22:33,385 --> 00:22:37,022
[SHIP HORN BLARES]

359
00:22:41,060 --> 00:22:42,995
Narrator:
A SHORT DISTANCE UPRIVER,

360
00:22:43,028 --> 00:22:44,630
GEOLOGIST SAM BOWRING

361
00:22:44,663 --> 00:22:47,099
HAS FOUND THE END
OF THE PERMIAN WORLD

362
00:22:47,132 --> 00:22:49,434
AND THE DAWN OF THE AGE
OF REPTILES--

363
00:22:49,468 --> 00:22:51,103
THE TRIASSIC PERIOD.

364
00:22:51,136 --> 00:22:54,539
Sam Bowring: OH, YEAH.
BEAUTIFULLY PRESERVED. YEAH.

365
00:22:54,573 --> 00:22:59,278
WHAT WE HAVE HERE IS AN EXPOSURE
OF THE PERMO-TRIASSIC BOUNDARY.

366
00:22:59,311 --> 00:23:02,347
NOW, YOU MIGHT SAY,
"WHAT’S SO SPECIAL ABOUT THIS?"

367
00:23:02,381 --> 00:23:04,483
YOU WOULDN’T KNOW
AT FIRST GLANCE,

368
00:23:04,516 --> 00:23:07,953
BUT IN FACT, THE ROCKS TO
THE RIGHT ARE PERMIAN-AGE ROCKS,

369
00:23:07,987 --> 00:23:09,255
FULL OF FOSSILS,

370
00:23:09,288 --> 00:23:12,858
AND THIS BLACK SHALE,
WHICH IS THE TRIASSIC--

371
00:23:12,892 --> 00:23:14,861
WHICH HAS NONE OF
THOSE ORGANISMS.

372
00:23:14,894 --> 00:23:18,030
AND THE LINE BETWEEN THEM
REPRESENTS

373
00:23:18,063 --> 00:23:22,601
THE GREATEST EXTINCTION
IN EARTH HISTORY.

374
00:23:22,635 --> 00:23:24,971
Narrator: THE BLACK SHALE
MARKING THE EXTINCTION

375
00:23:25,004 --> 00:23:27,740
REVEALS A SICK OCEAN.

376
00:23:29,341 --> 00:23:35,080
WHAT POWERFUL EVENT
UNLEASHED THESE CHANGES?

377
00:23:35,114 --> 00:23:37,383
TO SOLVE THE MYSTERY,
THEY NEED TO FIGURE OUT

378
00:23:37,416 --> 00:23:41,086
PRECISELY WHEN
THE EXTINCTION OCCURRED.

379
00:23:44,957 --> 00:23:48,327
JUST ABOVE THE BOUNDARY,
THERE MAY BE AN ANSWER.

380
00:23:48,360 --> 00:23:51,997
A LAYER OF ANCIENT ASH
FROM A NEARBY VOLCANO,

381
00:23:52,031 --> 00:23:56,736
FULL OF TIME-TELLING CRYSTALS
CALLED ZIRCONS.

382
00:23:56,769 --> 00:23:59,372
Bowring: THE MINERAL ZIRCON,
IT’S A FAMOUS GEMSTONE.

383
00:23:59,405 --> 00:24:01,674
BUT IT HAS A VERY UNIQUE
ATTRIBUTE,

384
00:24:01,707 --> 00:24:04,176
AND THAT IS THAT WHEN
IT FORMS IN A MAGMA,

385
00:24:04,209 --> 00:24:07,813
IT’S LIKE STARTING A CLOCK.

386
00:24:07,846 --> 00:24:10,482
Narrator: A CLOCK BASED
ON RADIOACTIVE DECAY,

387
00:24:10,516 --> 00:24:14,420
WHICH CAN TELL WHEN
A VOLCANIC ROCK WAS FORMED.

388
00:24:16,822 --> 00:24:19,258
Bowring: SO THIS IS
THE VOLCANIC LAYER

389
00:24:19,291 --> 00:24:22,127
THAT IS VERY CLOSE TO
THE PERMO-TRIASSIC BOUNDARY,

390
00:24:22,161 --> 00:24:24,363
WHICH IS RIGHT HERE.

391
00:24:24,396 --> 00:24:26,999
SO WE’RE GOING TO SEPARATE
ZIRCONS FROM IT.

392
00:24:27,032 --> 00:24:29,067
AND WE’RE EXCITED ABOUT THIS ONE
IN PARTICULAR,

393
00:24:29,101 --> 00:24:31,937
BECAUSE WE ARE GOING TO GET
THE BEST ESTIMATE

394
00:24:31,971 --> 00:24:35,041
OF THE AGE OF
THE PERMO-TRIASSIC BOUNDARY.

395
00:24:35,074 --> 00:24:40,479
[TRAIN WHISTLE BLOWS]

396
00:24:41,914 --> 00:24:45,284
Shen: YES, THIS IS JUST HERE,
WE FOUND, ACTUALLY.

397
00:24:45,317 --> 00:24:47,553
Narrator: ONCE THE TEAM
DATES THE BOUNDARY,

398
00:24:47,586 --> 00:24:51,857
THEY CAN FIGURE OUT WHEN
THE EXTINCTION BEGAN.

399
00:24:51,890 --> 00:24:55,727
THEN THEY CAN LOOK FOR EVENTS
THAT HAPPENED AT THE SAME TIME

400
00:24:55,761 --> 00:24:59,365
AND ZERO IN
ON THE LIKELIEST SUSPECTS.

401
00:25:04,737 --> 00:25:05,972
BACK IN THE U.S.,

402
00:25:06,005 --> 00:25:10,009
SCIENTISTS FOLLOW
ANOTHER TRAIL OF EVIDENCE.

403
00:25:10,042 --> 00:25:14,380
IN ROCKS FROM THE BOUNDARY,
THERE’S AN INTRIGUING CLUE--

404
00:25:14,413 --> 00:25:17,049
A SUDDEN CHANGE
IN THE TYPE OF CARBON--

405
00:25:17,082 --> 00:25:20,385
EVIDENCE OF A DRAMATIC
GLOBAL DISTURBANCE.

406
00:25:22,287 --> 00:25:23,989
Jonathan Payne: WHEN WE SAW
THIS DISTURBANCE,

407
00:25:24,023 --> 00:25:26,959
THIS INDICATED THAT THERE WAS
PROBABLY A RAPID ADDITION

408
00:25:26,992 --> 00:25:31,163
OF A LOT OF CARBON DIOXIDE GAS
TO THE ATMOSPHERE.

409
00:25:31,196 --> 00:25:32,497
AND THAT’S WORRISOME,

410
00:25:32,531 --> 00:25:36,135
BECAUSE CARBON DIOXIDE
CONTROLS EARTH’S CLIMATE.

411
00:25:36,168 --> 00:25:38,203
SO THE BIG QUESTION
THAT CAME UP IN OUR MINDS

412
00:25:38,237 --> 00:25:40,873
IS WHERE DID THE CARBON
COME FROM?

413
00:25:48,080 --> 00:25:52,585
Narrator: ONE PRIME SUSPECT
LIES IN THE VASTNESS OF SIBERIA.

414
00:25:55,421 --> 00:25:57,790
AROUND 250 MILLION YEARS AGO,

415
00:25:57,823 --> 00:26:00,259
A SERIES OF MASSIVE
VOLCANIC ERUPTIONS

416
00:26:00,292 --> 00:26:04,263
RAVAGED MORE THAN A MILLION
SQUARE MILES OF LAND.

417
00:26:07,066 --> 00:26:09,368
THE EARTH’S MANTLE
SPEWED OUT ENOUGH LAVA

418
00:26:09,401 --> 00:26:12,504
TO BURY AN AREA THE SIZE
OF THE CONTINENTAL U.S.

419
00:26:12,538 --> 00:26:16,242
UNDER A LAYER
AT LEAST 1,000 FEET DEEP.

420
00:26:17,776 --> 00:26:20,979
HUGE AMOUNTS OF GASES,
INCLUDING CARBON DIOXIDE,

421
00:26:21,013 --> 00:26:23,516
POURED INTO THE ATMOSPHERE.

422
00:26:25,984 --> 00:26:28,186
SAM BOWRING AND
A TEAM OF SCIENTISTS

423
00:26:28,220 --> 00:26:29,788
HAVE COME TO THIS REMOTE AREA

424
00:26:29,822 --> 00:26:32,024
TO SEARCH FOR REMNANTS
OF THE ERUPTIONS,

425
00:26:32,057 --> 00:26:35,928
KNOWN AS THE SIBERIAN TRAPS.

426
00:26:35,961 --> 00:26:40,098
MUCH OF THE VOLCANIC ROCK
LIES BURIED UNDERGROUND.

427
00:26:44,136 --> 00:26:47,139
TO REACH IT, THE EXPEDITION
WILL TRAVEL DOWN RIVERS

428
00:26:47,172 --> 00:26:50,375
THAT HAVE CARVED THROUGH
THE ANCIENT LAVA.

429
00:26:51,243 --> 00:26:54,546
[AIR PUMP HISSING]

430
00:26:56,615 --> 00:26:58,684
Bowring: THE BEAUTY
OF BEING ON THIS RIVER

431
00:26:58,717 --> 00:27:02,321
IS THAT WE ARE ABLE
TO FLOAT THROUGH TIME.

432
00:27:02,354 --> 00:27:05,357
AND WE’RE GOING TO GO UP
THROUGH THE PERMIAN.

433
00:27:05,390 --> 00:27:06,925
AND THEN THE LAST BIT
OF THE PERMIAN

434
00:27:06,959 --> 00:27:09,295
IS COVERED WITH THIS THICK
OUTPOURING OF LAVA

435
00:27:09,328 --> 00:27:11,764
THAT WE KNOW AS
THE SIBERIAN TRAPS.

436
00:27:11,797 --> 00:27:14,400
AND WE NEED TO EVALUATE
ONCE AND FOR ALL,

437
00:27:14,433 --> 00:27:17,569
DOES IT COINCIDE EXACTLY
WITH THE EXTINCTION,

438
00:27:17,603 --> 00:27:19,872
OR IS IT POST THE EXTINCTION,

439
00:27:19,905 --> 00:27:23,008
OR DOES IT SIGNIFICANTLY
PREDATE THE EXTINCTION?

440
00:27:26,044 --> 00:27:27,646
Man: OH, YES!

441
00:27:27,679 --> 00:27:29,080
Narrator:
AFTER DAYS OF TRAVELING,

442
00:27:29,114 --> 00:27:33,485
GEOLOGIST LINDY ELKINS-TANTON
MAKES THE FIRST DISCOVERY.

443
00:27:33,519 --> 00:27:35,388
Lindy Elkins-Tanton:
THAT IS LAVA.

444
00:27:35,420 --> 00:27:37,889
THIS IS MATERIAL
THAT’S FILLED IN AROUND.

445
00:27:37,923 --> 00:27:39,892
SEE THAT EDGE RIGHT THERE?

446
00:27:39,925 --> 00:27:41,527
Narrator: A LAYER OF
ANCIENT LAVA

447
00:27:41,560 --> 00:27:44,363
BESIDE ROCKS FROM
THE PERMIAN WORLD.

448
00:27:44,396 --> 00:27:46,565
Elkins-Tanton: THIS IS THE FIRST
MOMENT IN THIS WHOLE TRIP

449
00:27:46,598 --> 00:27:49,034
WE’VE ACTUALLY FOUND
THE LOWER-MOST LAVA

450
00:27:49,067 --> 00:27:53,171
WHERE IT IS IN CONTACT WITH
THE UPPER PERMIAN SEDIMENTS

451
00:27:53,205 --> 00:27:54,473
THAT IT ERUPTED ONTO.

452
00:27:54,506 --> 00:27:56,174
AND SO RIGHT ON THIS INTERFACE

453
00:27:56,208 --> 00:27:59,978
IS WHERE WE THINK THAT
THE EARTH STARTED TO CHANGE.

454
00:28:02,814 --> 00:28:05,650
Narrator: CLUES TO THIS CHANGE
MUST BE HERE.

455
00:28:05,684 --> 00:28:07,252
Man: YOU GOT SOME...
AM I KEEPING THESE?

456
00:28:07,286 --> 00:28:08,721
Elkins-Tanton:
YEAH, HANG ON TO THOSE.

457
00:28:08,754 --> 00:28:09,989
Benjamin Black:
THIS SAMPLE LOOKS GOOD.

458
00:28:10,022 --> 00:28:11,290
Elkins-Tanton:
DOES IT LOOK GOOD?

459
00:28:11,323 --> 00:28:14,026
Narrator: AS WELL AS ZIRCONS
TO DATE THE ERUPTIONS.

460
00:28:16,361 --> 00:28:19,664
BUT COLLECTING THE EVIDENCE
WILL TAKE ENDURANCE.

461
00:28:19,698 --> 00:28:22,000
[INSECTS BUZZING]

462
00:28:22,034 --> 00:28:23,269
Bowring: THERE’S NOTHING LIKE
RIDING IN A BOAT

463
00:28:23,302 --> 00:28:25,571
WITH A CLOUD OF MOSQUITOES
AROUND YOUR HEAD

464
00:28:25,604 --> 00:28:28,173
AND DRIVING RAIN.

465
00:28:28,207 --> 00:28:31,343
Black: YOU NEED SOME THINGS
TO MAKE YOU REALIZE

466
00:28:31,376 --> 00:28:34,112
YOU’RE IN SIBERIA.

467
00:28:35,914 --> 00:28:37,682
Narrator: AFTER MULTIPLE
EXPEDITIONS,

468
00:28:37,716 --> 00:28:41,353
THE HUNT FOR EVIDENCE
IS COMING TO AN END.

469
00:28:41,386 --> 00:28:43,421
NOW IT’S TIME TO FIGURE OUT

470
00:28:43,455 --> 00:28:46,458
IF THE GREATEST VOLCANIC
ERUPTIONS IN EARTH’S HISTORY

471
00:28:46,491 --> 00:28:49,361
CAUSED ITS GREATEST
MASS EXTINCTION.

472
00:28:58,537 --> 00:29:03,542
IN CAMBRIDGE, MASSACHUSETTS,
THE EVIDENCE HAS ARRIVED.

473
00:29:03,575 --> 00:29:07,379
WILL IT LINK THE SIBERIAN
ERUPTIONS TO THE GREAT DYING?

474
00:29:10,082 --> 00:29:13,252
THE FIRST TASK--
TO ISOLATE THE ZIRCONS,

475
00:29:13,285 --> 00:29:16,488
THE TIME-TELLING CRYSTALS
THAT RECORD HISTORY.

476
00:29:20,993 --> 00:29:23,829
AFTER FIGURING OUT
WHEN EACH ZIRCON WAS FORMED,

477
00:29:23,862 --> 00:29:28,400
THE SCIENTISTS HAVE A RANGE
OF REMARKABLY PRECISE DATES.

478
00:29:31,136 --> 00:29:32,571
Seth Burgess:
IT’S AN AMAZING THING.

479
00:29:32,604 --> 00:29:36,875
WHAT WE’VE BEEN ABLE TO SHOW
FROM OUR WORK IN SOUTH CHINA

480
00:29:36,908 --> 00:29:41,246
IS THAT THE MASS EXTINCTION
OCCURRED VERY QUICKLY

481
00:29:41,280 --> 00:29:44,350
AND OVER A VERY SHORT
DURATION HERE.

482
00:29:44,383 --> 00:29:46,585
Bowring: 251.9.

483
00:29:46,618 --> 00:29:49,321
Burgess: AND WE CAN SHOW
FROM OUR SIBERIA TRIPS

484
00:29:49,354 --> 00:29:51,156
AND THE ZIRCONS
THAT WE’VE DATED,

485
00:29:51,189 --> 00:29:55,560
THAT THE SIBERIAN ERUPTION
OCCURRED AT THE SAME TIME AS,

486
00:29:55,594 --> 00:29:58,197
OR EVEN JUST A BIT PRIOR TO,

487
00:29:58,230 --> 00:29:59,998
THE ONSET OF
THE MASS EXTINCTION.

488
00:30:00,032 --> 00:30:02,501
AND THAT’S A VERY
IMPORTANT RESULT.

489
00:30:05,604 --> 00:30:07,439
Bowring: WHEN YOU HAVE
TWO EVENTS IN EARTH HISTORY,

490
00:30:07,472 --> 00:30:10,842
BOTH SHORT DURATION,
EXACTLY THE SAME AGE,

491
00:30:10,876 --> 00:30:12,077
IT DOESN’T GET ANY BETTER

492
00:30:12,110 --> 00:30:14,479
IN TERMS OF FINDING
THE SMOKING GUN.

493
00:30:18,083 --> 00:30:19,451
Narrator: IT’S POWERFUL EVIDENCE

494
00:30:19,484 --> 00:30:22,187
THAT MASSIVE VOLCANOES
IN SIBERIA

495
00:30:22,220 --> 00:30:24,589
TRIGGERED THE GREAT DYING.

496
00:30:29,061 --> 00:30:33,399
EVEN MORE SURPRISING IS
THE SPEED OF THE EXTINCTION.

497
00:30:33,432 --> 00:30:35,868
INSTEAD OF HAPPENING SLOWLY
OVER MILLIONS OF YEARS

498
00:30:35,901 --> 00:30:37,970
AS ONCE THOUGHT--

499
00:30:38,003 --> 00:30:41,306
IT UNFOLDED IN LESS THAN 60,000.

500
00:30:53,485 --> 00:30:57,723
BUT HOW COULD ERUPTIONS IN
SIBERIA AFFECT THE ENTIRE WORLD?

501
00:31:00,292 --> 00:31:03,929
CRYSTALS WITHIN ANCIENT LAVA
MAY CONTAIN THE ANSWERS.

502
00:31:06,465 --> 00:31:09,802
IN THEM, BEN BLACK HAS FOUND
TINY DROPLETS OF MAGMA

503
00:31:09,835 --> 00:31:12,905
THAT, AMAZINGLY,
STILL CONTAIN GASES

504
00:31:12,938 --> 00:31:15,974
FROM 250 MILLION YEARS AGO.

505
00:31:19,578 --> 00:31:22,347
Black: YOU CAN SEE THE CRYSTAL
THAT WE’RE ANALYZING RIGHT HERE,

506
00:31:22,381 --> 00:31:25,951
AND OVER HERE YOU CAN SEE
THE ACTUAL GASES

507
00:31:25,984 --> 00:31:27,853
THAT WERE TRAPPED
INSIDE THIS CRYSTAL.

508
00:31:27,886 --> 00:31:31,823
SO THE BRIGHTEST ORANGE COLORS
SHOW THE MOST SULFUR HERE.

509
00:31:31,857 --> 00:31:33,425
AND THEN THESE GREENS SHOW YOU

510
00:31:33,458 --> 00:31:35,927
WHERE THERE’S GASES
LIKE FLUORINE,

511
00:31:35,961 --> 00:31:41,867
AND WE FIND CHLORINE, CARBON,
WHICH WOULD BE CARBON DIOXIDE.

512
00:31:41,900 --> 00:31:44,102
Elkins-Tanton: SO IT’S TRILLIONS
OF TONS OF GASES

513
00:31:44,136 --> 00:31:46,472
RELEASED INTO THE ATMOSPHERE.

514
00:31:46,505 --> 00:31:48,207
AND WE TAKE ALL THE EVIDENCE,

515
00:31:48,240 --> 00:31:50,609
AND WE PUT THEM
INTO GLOBAL CLIMATE MODELS.

516
00:31:50,642 --> 00:31:54,746
AND WE ASK THE QUESTION, CAN
THAT MUCH GAS CHANGE THE CLIMATE

517
00:31:54,780 --> 00:31:57,483
TO SUCH AN EXTENT THAT
IT WOULD KILL ALL THE THINGS

518
00:31:57,516 --> 00:31:59,752
THAT WE KNOW THAT IT KILLED?

519
00:31:59,785 --> 00:32:01,553
AND IT LOOKS LIKE
THAT’S WHAT IT TAKES

520
00:32:01,586 --> 00:32:04,222
TO MAKE A GLOBAL
EXTINCTION EVENT.

521
00:32:07,025 --> 00:32:08,493
Narrator: OUR PICTURE
OF THE GREAT DYING

522
00:32:08,527 --> 00:32:11,330
IS NOW CLEARER THAN EVER BEFORE.

523
00:32:14,566 --> 00:32:18,336
AS MAGMA ROSE TO THE SURFACE,
IT HEATED SEDIMENTARY ROCKS,

524
00:32:18,370 --> 00:32:22,107
RELEASING MASSIVE AMOUNTS
OF CLIMATE-CHANGING GASES.

525
00:32:28,980 --> 00:32:33,184
AMONG THEM WAS CARBON DIOXIDE,
WHICH TRAPS HEAT.

526
00:32:35,954 --> 00:32:39,925
AS THE WORLD GREW WARMER,
OCEANS CURRENTS MAY HAVE SLOWED,

527
00:32:39,958 --> 00:32:44,663
CUTTING OFF THE FLOW OF OXYGEN,
CREATING DEAD ZONES.

528
00:32:47,699 --> 00:32:51,136
EXCESS CARBON DIOXIDE TRIGGERED
OCEAN ACIDIFICATION,

529
00:32:51,169 --> 00:32:54,472
PREVENTING ANIMALS
FROM BUILDING SHELLS.

530
00:32:58,109 --> 00:32:59,944
THE CHANGES WERE SO OVERWHELMING

531
00:32:59,978 --> 00:33:02,981
THAT MOST CREATURES
COULD NOT ADAPT.

532
00:33:05,116 --> 00:33:07,151
SO WHAT CAN EXTINCTIONS
OF THE PAST

533
00:33:07,185 --> 00:33:10,055
TELL US ABOUT OUR WORLD TODAY?

534
00:33:11,923 --> 00:33:13,024
Carroll: WHAT’S REALLY VALUABLE

535
00:33:13,058 --> 00:33:14,860
ABOUT COMPARING THESE
MASS EXTINCTIONS,

536
00:33:14,893 --> 00:33:16,762
THE KT AND THE END-PERMIAN,

537
00:33:16,795 --> 00:33:20,065
IS THEY WERE CAUSED BY TOTALLY
DIFFERENT TRIGGERS, RIGHT?

538
00:33:20,098 --> 00:33:23,668
AN ASTEROID FROM ABOVE
OR VOLCANISM FROM BENEATH.

539
00:33:23,702 --> 00:33:25,370
BUT THEY HAD
VERY SIMILAR EFFECTS

540
00:33:25,403 --> 00:33:27,572
IN TERMS OF
CATASTROPHIC DESTRUCTION

541
00:33:27,606 --> 00:33:29,441
OF ECOSYSTEMS AROUND THE WORLD.

542
00:33:29,474 --> 00:33:31,343
AND THERE’S
A REALLY SIMPLE LESSON

543
00:33:31,376 --> 00:33:32,744
THAT’S RELEVANT TO TODAY,

544
00:33:32,777 --> 00:33:36,281
WHICH IS, IF ENVIRONMENTAL
CHANGE IS GREAT ENOUGH,

545
00:33:36,314 --> 00:33:39,250
FAST ENOUGH,
AND ON A GLOBAL SCALE,

546
00:33:39,284 --> 00:33:42,254
THE ENTIRE PLANET IS IN TROUBLE.

547
00:33:42,287 --> 00:33:46,158
Narrator: HUMANS ARE RAPIDLY
CHANGING THE EARTH.

548
00:33:46,191 --> 00:33:49,461
COULD LIFE BE
AT THE BRINK AGAIN?

549
00:33:58,937 --> 00:34:01,039
MASS EXTINCTIONS EONS AGO

550
00:34:01,072 --> 00:34:04,375
MAY SEEM AS IF THEY HAPPENED
ON A DISTANT PLANET.

551
00:34:08,079 --> 00:34:11,182
BUT THIS IS THE SAME STAGE,

552
00:34:11,216 --> 00:34:13,785
EVEN IF THE ACTORS HAVE CHANGED.

553
00:34:16,288 --> 00:34:21,260
WE’RE NOW IN A THIRD GREAT AGE,
KNOWN AS THE AGE OF MAMMALS.

554
00:34:23,762 --> 00:34:29,201
DURING THIS TIME, LIFE REACHED
ITS GREATEST LEVEL OF DIVERSITY.

555
00:34:32,370 --> 00:34:34,405
BUT THERE ARE FEARS
THAT THE WORLD COULD FACE

556
00:34:34,439 --> 00:34:36,875
ANOTHER MASS EXTINCTION.

557
00:34:36,908 --> 00:34:40,512
ONLY THIS TIME, INSTEAD
OF VOLCANOES OR ASTEROIDS,

558
00:34:40,545 --> 00:34:43,114
THE TRIGGER WOULD BE US.

559
00:34:46,885 --> 00:34:49,988
PALEONTOLOGIST ANTHONY BARNOSKY
IS INVESTIGATING

560
00:34:50,021 --> 00:34:54,692
IF THE SIXTH MASS EXTINCTION
HAS ALREADY ARRIVED.

561
00:34:57,028 --> 00:34:59,531
Anthony Barnosky: HUMANS USED TO
BE PART OF NATURE.

562
00:34:59,564 --> 00:35:02,100
NOW WE’RE A FORCE OF NATURE.

563
00:35:02,133 --> 00:35:06,838
WE HAVE TRANSFORMED 40% OF
THE PLANET FOR OUR OWN NEEDS.

564
00:35:06,871 --> 00:35:09,173
AND THINGS ARE ONLY
GOING TO GET WORSE,

565
00:35:09,207 --> 00:35:12,010
BECAUSE WE’RE GOING TO HAVE
THREE BILLION MORE PEOPLE

566
00:35:12,043 --> 00:35:15,313
ON THE PLANET BY THE YEAR 2050.

567
00:35:19,017 --> 00:35:22,954
Narrator: ACROSS THE WORLD,
VAST REGIONS OF FORESTS,

568
00:35:22,988 --> 00:35:28,060
HOME TO MOST BIODIVERSITY
ON LAND, HAVE DISAPPEARED.

569
00:35:31,630 --> 00:35:34,433
OTHER HABITATS
ARE ALSO VANISHING.

570
00:35:36,568 --> 00:35:37,836
70 YEARS AGO,

571
00:35:37,869 --> 00:35:41,973
THE AFRICAN SAVANNAH WAS HOME
TO 400,000 LIONS.

572
00:35:43,908 --> 00:35:49,113
TODAY, ONLY AROUND 30,000 REMAIN
IN ISOLATED PATCHES.

573
00:35:51,716 --> 00:35:54,152
Barnosky: WE’RE DOING TWO THINGS
TO OTHER SPECIES NOW.

574
00:35:54,185 --> 00:35:56,521
WE’RE TAKING AWAY
WHERE THEY LIVE.

575
00:35:56,554 --> 00:35:59,624
BUT WE’RE ALSO SEPARATING
THEIR NEIGHBORHOODS.

576
00:35:59,658 --> 00:36:02,794
AND THE PROBLEM IS THAT
WE’RE CHANGING THE CLIMATE

577
00:36:02,827 --> 00:36:06,064
AT THE SAME TIME.

578
00:36:06,097 --> 00:36:08,099
SO THE NORMAL RESPONSE
OF A SPECIES

579
00:36:08,133 --> 00:36:10,702
WOULD BE JUST TO MOVE
TO A NEW HOME.

580
00:36:10,735 --> 00:36:12,370
THEY CAN’T DO THAT ANYMORE,

581
00:36:12,404 --> 00:36:14,539
BECAUSE, IN ORDER TO MOVE
TO A NEW HOME,

582
00:36:14,572 --> 00:36:17,675
THEY MIGHT HAVE TO GO
THROUGH LOS ANGELES.

583
00:36:19,978 --> 00:36:21,546
Narrator: BARNOSKY BELIEVES
WE’RE CHANGING

584
00:36:21,579 --> 00:36:23,247
THE EARTH’S ATMOSPHERE IN WAYS

585
00:36:23,281 --> 00:36:26,184
THAT RIVAL PAST
MASS EXTINCTIONS.

586
00:36:28,186 --> 00:36:30,255
JUST LIKE
THE SIBERIAN ERUPTIONS,

587
00:36:30,288 --> 00:36:34,058
WE’RE RELEASING GREENHOUSE GASES
THAT TRAP HEAT.

588
00:36:37,662 --> 00:36:39,297
OVER THE PAST CENTURY,

589
00:36:39,330 --> 00:36:43,301
CO2 LEVELS AND GLOBAL SURFACE
TEMPERATURES HAVE CLIMBED,

590
00:36:43,334 --> 00:36:46,204
STRESSING ECOSYSTEMS
ACROSS THE WORLD.

591
00:36:50,809 --> 00:36:52,411
YOU CAN SEE THE WARNING SIGNS

592
00:36:52,444 --> 00:36:55,647
EVEN IN ONE OF THE WORLD’S
MOST PROTECTED PLACES,

593
00:36:55,680 --> 00:36:58,850
YELLOWSTONE NATIONAL PARK.

594
00:36:58,883 --> 00:37:02,587
[WOLF HOWLS]

595
00:37:06,391 --> 00:37:08,059
[BISON GRUNTS]

596
00:37:10,395 --> 00:37:13,298
IT LIES WITHIN ONE OF
THE LARGEST INTACT ECOSYSTEMS

597
00:37:13,331 --> 00:37:15,200
NORTH OF THE EQUATOR,

598
00:37:15,233 --> 00:37:18,636
SHELTERING OVER 60 SPECIES
OF MAMMALS.

599
00:37:25,076 --> 00:37:26,978
AMONG THEM IS THE GRIZZLY BEAR,

600
00:37:27,011 --> 00:37:31,616
WHOSE NUMBERS HAVE REBOUNDED
FROM 150 TO ABOUT 600.

601
00:37:34,219 --> 00:37:37,889
BUT GRIZZLIES ARE BACK ON
THE ENDANGERED SPECIES LIST.

602
00:37:39,257 --> 00:37:40,792
CLIMATE CHANGE IS KILLING OFF

603
00:37:40,825 --> 00:37:43,194
ONE OF THEIR KEY
SOURCES OF FOOD--

604
00:37:43,228 --> 00:37:47,165
THE HIGH-FAT SEEDS OF
THE WHITEBARK PINE TREE.

605
00:37:50,802 --> 00:37:53,271
ACROSS THE AMERICAN
AND CANADIAN ROCKIES,

606
00:37:53,304 --> 00:37:56,374
ONCE-GREEN FORESTS
ARE BLEACHED OF COLOR,

607
00:37:56,407 --> 00:38:00,745
AS WHITEBARK PINES ARE KILLED
BY A TINY ASSAILANT.

608
00:38:06,918 --> 00:38:08,887
BIOLOGIST ELIZABETH HADLY
HAS STUDIED

609
00:38:08,920 --> 00:38:12,490
THE YELLOWSTONE ECOSYSTEM
FOR 30 YEARS.

610
00:38:12,524 --> 00:38:14,126
Elizabeth Hadly: OKAY, SEAN.

611
00:38:14,159 --> 00:38:16,294
THIS IS A REALLY,
THIS IS A GREAT EXAMPLE.

612
00:38:16,327 --> 00:38:20,097
SO, YOU KNOW, IF YOU LOOK UP,
YOU SEE GREEN BRANCHES,

613
00:38:20,131 --> 00:38:22,467
AND THERE’S SOME CONES UP THERE.

614
00:38:22,500 --> 00:38:25,069
BUT IN FACT THIS TREE
HAS JUST BEEN HIT.

615
00:38:25,103 --> 00:38:27,872
AND THE EVIDENCE
ARE THESE LITTLE HOLES

616
00:38:27,906 --> 00:38:29,274
THAT ARE MARKED BY RED.

617
00:38:29,307 --> 00:38:34,279
Carroll: SO THE DEFENSE THAT
THIS TREE HAS IS REALLY MINIMAL.

618
00:38:35,814 --> 00:38:37,182
Hadly: THAT SIGN HERE...

619
00:38:37,215 --> 00:38:39,350
Narrator: THE CULPRIT IS
THE MOUNTAIN PINE BEETLE,

620
00:38:39,384 --> 00:38:42,420
WHICH BORES INTO THE BARK
TO LAY ITS EGGS.

621
00:38:44,389 --> 00:38:47,359
THE NEWLY HATCHED LARVAE
EAT AWAY AT THE TREE,

622
00:38:47,392 --> 00:38:48,860
QUICKLY KILLING IT.

623
00:38:48,893 --> 00:38:52,163
Carroll: SO THIS IS THE BEAST
CAUSING ALL THE TROUBLE.

624
00:38:52,197 --> 00:38:55,634
LOOK AT THAT, NOT EVEN AS BIG
AS MY FINGERNAIL.

625
00:38:57,769 --> 00:38:59,671
Narrator: BEETLES HAVE
LONG LIVED HERE,

626
00:38:59,704 --> 00:39:01,272
BUT AS THE CLIMATE WARMS,

627
00:39:01,306 --> 00:39:03,341
THEY’RE MOVING TO
HIGHER ELEVATIONS,

628
00:39:03,374 --> 00:39:06,911
ATTACKING TREES
ONCE OUT OF REACH.

629
00:39:08,713 --> 00:39:11,182
AN AVERAGE INCREASE OF
JUST A COUPLE OF DEGREES

630
00:39:11,216 --> 00:39:14,686
MEANS THE WINTER IS NO LONGER
COLD ENOUGH, FOR LONG ENOUGH,

631
00:39:14,719 --> 00:39:16,821
TO KILL OFF THE BEETLES.

632
00:39:19,824 --> 00:39:23,161
AND IT’S ALL HAPPENING
VERY FAST.

633
00:39:25,129 --> 00:39:26,797
Hadly: THIS IS WHAT AN ATTACK
LOOKS LIKE

634
00:39:26,831 --> 00:39:27,965
SEVEN TO TEN YEARS LATER.

635
00:39:27,999 --> 00:39:28,800
Carroll: WOW!

636
00:39:28,833 --> 00:39:30,335
Hadly: THE LAST TIME I WAS HERE,

637
00:39:30,368 --> 00:39:35,006
THIS WAS A DENSE, GREEN FOREST
WITH A CACOPHONY OF SOUND.

638
00:39:35,039 --> 00:39:39,243
WITHIN TEN YEARS,
THIS FOREST IS SILENT.

639
00:39:39,277 --> 00:39:41,679
THESE TREES ARE NOT GOING
TO PRODUCE CONES

640
00:39:41,713 --> 00:39:43,181
FOR AT LEAST 50 YEARS.

641
00:39:43,214 --> 00:39:45,450
THAT IS, IF WHITEBARK PINE
COMES BACK.

642
00:39:45,483 --> 00:39:47,185
Carroll: SO THE CHANGE
MAY BE PERMANENT.

643
00:39:47,218 --> 00:39:49,687
[SQUAWKING]

644
00:39:51,256 --> 00:39:55,594
Narrator: AND BEARS AREN’T
THE ONLY LOSERS.

645
00:39:55,627 --> 00:39:57,796
CLIMATE CHANGE
OF JUST A FEW DEGREES

646
00:39:57,829 --> 00:40:01,399
IS THREATENING THE WEB OF LIFE.

647
00:40:01,432 --> 00:40:05,336
SPECIES AROUND THE WORLD
ARE MOVING, IF THEY CAN.

648
00:40:07,338 --> 00:40:08,639
EVEN MORE WORRISOME,

649
00:40:08,673 --> 00:40:12,377
TEMPERATURES MAY RISE
BY 9 TO 11 DEGREES FAHRENHEIT

650
00:40:12,410 --> 00:40:15,079
BY THE END OF THE CENTURY--

651
00:40:15,113 --> 00:40:20,051
A RISE ALMOST AS GREAT
AS DURING THE END-PERMIAN.

652
00:40:20,084 --> 00:40:22,587
Carroll: AND THE UNCERTAINTY IS
NOT THAT THE CLIMATE IS WARMING.

653
00:40:22,620 --> 00:40:24,689
THE UNCERTAINTY IS WHAT
THE EFFECTS ARE GONNA BE.

654
00:40:24,722 --> 00:40:26,524
THINGS THAT SURPRISE BIOLOGISTS.

655
00:40:26,557 --> 00:40:27,925
UNEXPECTED CONNECTIONS.

656
00:40:27,959 --> 00:40:29,627
OR, FOR EXAMPLE,
CERTAIN POPULATIONS

657
00:40:29,661 --> 00:40:32,464
THAT ARE UNDER CERTAIN STRESSES
WE DIDN’T QUITE RECOGNIZE,

658
00:40:32,497 --> 00:40:35,033
BUT THE NEXT STRESS
MAY PUSH THEM OVER THE EDGE.

659
00:40:38,569 --> 00:40:41,238
Narrator: WHAT’S HAPPENING
ON LAND IS VISIBLE.

660
00:40:41,272 --> 00:40:43,941
BUT WHAT ABOUT BENEATH THE SEA?

661
00:40:47,445 --> 00:40:49,180
ALONG THE CALIFORNIA COAST,

662
00:40:49,213 --> 00:40:52,383
THERE ARE SIGNS THAT THE CO2
WARMING THE ATMOSPHERE

663
00:40:52,417 --> 00:40:55,453
IS ALSO DISSOLVING
INTO THE OCEANS,

664
00:40:55,486 --> 00:40:58,422
CHANGING THEIR CHEMISTRY.

665
00:40:58,456 --> 00:40:59,724
Barnosky: AND IT HAS
THE NET EFFECT

666
00:40:59,757 --> 00:41:02,827
OF ACTUALLY MAKING THOSE WATERS
MORE ACIDIC.

667
00:41:02,860 --> 00:41:05,029
AND IT’S A HUGE PROBLEM

668
00:41:05,063 --> 00:41:06,731
FOR THE MARINE CREATURES
THAT LIVE THERE.

669
00:41:06,764 --> 00:41:09,700
THEY RELY ON A CERTAIN
WATER CHEMISTRY.

670
00:41:09,734 --> 00:41:14,973
IF THE WATERS GET TOO ACIDIC,
THEY CAN’T BUILD THEIR SHELLS.

671
00:41:15,006 --> 00:41:18,843
IN FACT, WE’RE ALREADY SEEING
THAT IN THE PACIFIC NORTHWEST,

672
00:41:18,876 --> 00:41:24,615
WHERE THE EMBRYOS OF OYSTERS
AND SCALLOPS CANNOT SURVIVE.

673
00:41:27,986 --> 00:41:29,955
Narrator: IF THE CURRENT TREND
CONTINUES,

674
00:41:29,988 --> 00:41:32,824
SCIENTISTS PREDICT THAT
BY THE END OF THIS CENTURY,

675
00:41:32,857 --> 00:41:36,060
THE RATE OF OCEAN ACIDIFICATION
WILL MIRROR WHAT HAPPENED

676
00:41:36,094 --> 00:41:38,430
DURING THE GREAT DYING.

677
00:41:41,766 --> 00:41:46,804
BY GEOLOGICAL STANDARDS, THIS IS
CHANGE AT A BREAKNECK PACE.

678
00:41:54,078 --> 00:41:56,180
Barnosky: THERE ARE PREDICTIONS
THAT WE WILL LOSE

679
00:41:56,214 --> 00:42:01,086
MOST OF THE CORAL REEFS ON EARTH
BY THE YEAR 2070.

680
00:42:01,119 --> 00:42:02,921
NOW, IF WE LOSE CORAL REEFS,

681
00:42:02,954 --> 00:42:07,192
WE’RE NOT JUST TALKING ABOUT
NO NICE PLACES TO SNORKEL,

682
00:42:07,225 --> 00:42:12,363
WE’RE TALKING ABOUT LOSS OF 25%
OF THE FISH SPECIES IN THE SEA

683
00:42:12,397 --> 00:42:14,232
THAT DEPEND ON CORAL REEFS.

684
00:42:14,265 --> 00:42:18,102
WE’RE TALKING ABOUT LOSS OF
10% OF THE OCEAN’S FISHERIES

685
00:42:18,136 --> 00:42:20,105
THAT WE DEPEND UPON.

686
00:42:22,774 --> 00:42:26,444
Narrator: HABITAT DESTRUCTION,
OCEAN ACIDIFICATION,

687
00:42:26,477 --> 00:42:30,348
RISING CO2 LEVELS
AND TEMPERATURES.

688
00:42:30,381 --> 00:42:33,951
HUMANS ARE ALMOST AS GOOD
AS ASTEROIDS AND VOLCANOES

689
00:42:33,985 --> 00:42:37,355
AT WREAKING HAVOC.

690
00:42:37,388 --> 00:42:40,992
SO HAS THE SIXTH MASS EXTINCTION
ALREADY BEGUN?

691
00:42:47,765 --> 00:42:50,868
TO FIND OUT, BARNOSKY ANALYZED
RATES OF EXTINCTION

692
00:42:50,902 --> 00:42:52,303
IN THE FOSSIL RECORD

693
00:42:52,336 --> 00:42:53,771
AND COMPARED THEM TO DATA

694
00:42:53,805 --> 00:42:57,175
TRACKING ENDANGERED SPECIES
TODAY.

695
00:42:57,208 --> 00:42:59,277
Barnosky:
I HAD A SNEAKING SUSPICION

696
00:42:59,310 --> 00:43:03,447
THAT IF WE WERE ABLE
TO CALCULATE EXTINCTION RATES

697
00:43:03,481 --> 00:43:06,951
OVER HUMAN HISTORY
OF THE PAST FEW CENTURIES

698
00:43:06,984 --> 00:43:10,321
IN THE SAME WAY WE CALCULATED
EXTINCTION RATES

699
00:43:10,354 --> 00:43:12,857
IN THE DEEP-TIME
PALEONTOLOGICAL RECORD,

700
00:43:12,890 --> 00:43:16,427
THAT IT MIGHT NOT LOOK SO BAD.

701
00:43:16,461 --> 00:43:19,898
I WAS TOTALLY WRONG.

702
00:43:19,931 --> 00:43:22,400
ONCE WE CRUNCHED THE NUMBERS,

703
00:43:22,433 --> 00:43:24,635
IT TURNED OUT
WE REALLY WERE SEEING

704
00:43:24,669 --> 00:43:29,107
HUGELY ACCELERATED
EXTINCTION RATES TODAY.

705
00:43:29,140 --> 00:43:32,310
Narrator: IN FACT,
AT LEAST 12 TIMES FASTER

706
00:43:32,343 --> 00:43:35,680
THAN SPECIES NORMALLY DIE OFF.

707
00:43:35,713 --> 00:43:38,182
TODAY, A QUARTER OF ALL MAMMAL

708
00:43:38,216 --> 00:43:41,486
AND ONE FIFTH OF FISH
AND REPTILE SPECIES

709
00:43:41,519 --> 00:43:44,889
ARE THREATENED WITH EXTINCTION.

710
00:43:44,922 --> 00:43:48,292
AMPHIBIANS ARE VANISHING
EVEN FASTER.

711
00:43:48,326 --> 00:43:51,129
Barnosky: IF WE CONTINUE
TO LOSE SPECIES

712
00:43:51,162 --> 00:43:54,499
AT THE RATE WE’VE LOST THEM
OVER THE LAST CENTURY,

713
00:43:54,532 --> 00:43:57,402
WITHIN AS LITTLE AS 200 YEARS,

714
00:43:57,435 --> 00:44:03,074
WE WOULD SEE 75% OF SPECIES
WE KNOW ABOUT

715
00:44:03,107 --> 00:44:07,044
DISAPPEARING FROM
THE PLANET FOREVER.

716
00:44:07,078 --> 00:44:09,380
IF WE CONTINUE DOING THINGS

717
00:44:09,413 --> 00:44:11,949
PRETTY MUCH AS WE ARE
DOING THEM TODAY,

718
00:44:11,983 --> 00:44:14,552
WHAT THAT MEANS IS
THE SIXTH MASS EXTINCTION

719
00:44:14,585 --> 00:44:16,587
IS A VIRTUAL CERTAINTY.

720
00:44:22,160 --> 00:44:23,862
Carroll: I THINK THE HARDEST
QUESTION TO ANSWER

721
00:44:23,895 --> 00:44:25,296
IS WHAT DO WE DO?

722
00:44:25,329 --> 00:44:27,331
PARTICULARLY WHAT DO WE DO AS
INDIVIDUALS? WHAT CAN WE DO?

723
00:44:27,365 --> 00:44:30,301
WELL, ONE THING WE KNOW
THAT WORKS ARE RESERVES.

724
00:44:30,334 --> 00:44:33,704
SET ASIDE A LARGE ENOUGH SPACE
OF INTACT ECOSYSTEMS,

725
00:44:33,738 --> 00:44:35,039
AND ANIMALS CAN THRIVE THERE.

726
00:44:35,072 --> 00:44:37,608
SO WE AT LEAST HAVE TO DO THAT.

727
00:44:37,642 --> 00:44:39,878
[WOLF HOWLS]

728
00:44:39,911 --> 00:44:42,447
Narrator: A GLOBAL EFFORT
IS NOW UNDER WAY

729
00:44:42,480 --> 00:44:45,583
TO CONNECT WILDLIFE HABITATS
WITH LAND CORRIDORS

730
00:44:45,616 --> 00:44:48,752
SO ANIMALS CAN MOVE FREELY.

731
00:44:48,786 --> 00:44:50,788
ONE CORRIDOR BEING PROPOSED

732
00:44:50,821 --> 00:44:53,557
WOULD RUN FROM ALASKA
TO THE YUCATAN,

733
00:44:53,591 --> 00:44:57,495
AND INCLUDES YELLOWSTONE.

734
00:44:57,528 --> 00:44:58,896
Barnosky: I JUST THINK
IT’S REALLY IMPORTANT

735
00:44:58,930 --> 00:45:04,002
FOR PEOPLE TO REALIZE
THAT THIS ISN’T A LOST CAUSE.

736
00:45:04,035 --> 00:45:06,538
HUMANITY IS AT A CROSSROADS
RIGHT NOW.

737
00:45:06,571 --> 00:45:10,775
WE CAN EITHER CHOOSE TO KEEP
ENDANGERED SPECIES ALIVE

738
00:45:10,808 --> 00:45:13,244
AND AVOID
THE SIXTH MASS EXTINCTION,

739
00:45:13,277 --> 00:45:16,747
OR WE CAN WATCH
THE TRAIN WRECK HAPPEN.

740
00:45:16,781 --> 00:45:20,952
WE HAVE A VERY NARROW WINDOW
OF OPPORTUNITY TO FIX THIS.

741
00:45:20,985 --> 00:45:22,353
WILL WE DO THAT?

742
00:45:22,386 --> 00:45:24,221
I LIKE TO THINK WE WILL.

743
00:45:24,255 --> 00:45:25,957
Carroll: THIS IS
THE AGE OF MAMMALS,

744
00:45:25,990 --> 00:45:28,159
AND WE DON’T WANT IT TO END
LIKE THE AGE OF DINOSAURS,

745
00:45:28,192 --> 00:45:30,461
PARTICULARLY AT OUR OWN HANDS.

746
00:45:30,494 --> 00:45:31,929
WE DON’T WANT
SORT OF THE EQUIVALENT

747
00:45:31,963 --> 00:45:33,364
OF T. REX OF YESTERDAY,

748
00:45:33,397 --> 00:45:34,999
THE GRIZZLY BEARS
OF NORTH AMERICA,

749
00:45:35,032 --> 00:45:37,735
OR THE LIONS OF AFRICA,
OR THE TIGERS OF ASIA,

750
00:45:37,768 --> 00:45:43,440
TO DISAPPEAR ONLY TO BE SEEN
AS STUFFED ANIMALS IN A MUSEUM.

751
00:45:43,474 --> 00:45:45,142
SO THE QUESTION IS CAN WE--

752
00:45:45,176 --> 00:45:47,111
BECAUSE WE UNDERSTAND
WHAT’S GOING ON--

753
00:45:47,144 --> 00:45:49,179
DO SOMETHING ABOUT IT?