1 00:00:27,320 --> 00:00:31,720 We are entranced by the beauty of our planet. 2 00:00:31,720 --> 00:00:34,280 Just take in this view for a moment. 3 00:00:34,280 --> 00:00:39,360 Lush green meadows, thick forest, jagged mountain peaks - 4 00:00:39,360 --> 00:00:41,080 it's magnificent. 5 00:00:46,000 --> 00:00:48,440 But whilst we appreciate that beauty, 6 00:00:48,440 --> 00:00:53,200 I think sometimes we forget that all of this is so fleeting. 7 00:00:53,200 --> 00:00:56,360 For the last four-and-a-half billion years, 8 00:00:56,360 --> 00:01:00,920 our Earth has been a constantly changing ball of rock, 9 00:01:00,920 --> 00:01:05,600 transforming itself over and over again. 10 00:01:05,600 --> 00:01:09,240 It's more fragile than we like to acknowledge. 11 00:01:09,240 --> 00:01:12,680 It's more indifferent to us than we care to admit. 12 00:01:16,000 --> 00:01:19,920 Now, thanks to pioneering new science, 13 00:01:19,920 --> 00:01:25,440 we can explore our planet's four-and-a-half-billion-year story 14 00:01:25,440 --> 00:01:26,920 like never before. 15 00:01:30,000 --> 00:01:34,600 In this series, we'll witness five pivotal moments 16 00:01:34,600 --> 00:01:36,240 in Earth's history... 17 00:01:39,240 --> 00:01:41,320 ..moments of drama... 18 00:01:42,880 --> 00:01:44,400 ..of crisis... 19 00:01:45,720 --> 00:01:48,000 ..and of rebirth... 20 00:01:51,720 --> 00:01:55,560 ..events that shaped the planet we live on. 21 00:01:58,200 --> 00:02:03,080 Wherever you are, you have beneath your feet the most precious object 22 00:02:03,080 --> 00:02:04,840 in the universe - 23 00:02:04,840 --> 00:02:09,160 a living, breathing, life-sustaining world. 24 00:02:09,160 --> 00:02:11,800 And this is its story. 25 00:02:48,240 --> 00:02:54,000 It can feel as if our living world was somehow inevitable... 26 00:03:00,280 --> 00:03:03,920 ..that ours is a planet with all the right ingredients 27 00:03:03,920 --> 00:03:06,480 for a rich assortment of life... 28 00:03:08,360 --> 00:03:13,320 ..not only to arise, but to flourish and endure. 29 00:03:14,800 --> 00:03:20,160 But, in fact, it's death that is the only true inevitability. 30 00:03:21,440 --> 00:03:25,480 There's an uncomfortable truth about life on Earth. 31 00:03:25,480 --> 00:03:29,520 You see, this great diversity, this weird, wonderful 32 00:03:29,520 --> 00:03:33,400 and beautiful mix of species, of plants, animals and fungi 33 00:03:33,400 --> 00:03:38,280 are all only here because something else has died - 34 00:03:38,280 --> 00:03:43,440 in fact, because an enormous number of other things have died. 35 00:03:43,440 --> 00:03:47,680 If we were to take the sum total of every living thing 36 00:03:47,680 --> 00:03:52,920 on our planet today, it would add up to less than 1% of those 37 00:03:52,920 --> 00:03:56,000 that have ever existed on Earth. 38 00:03:56,000 --> 00:04:00,880 But this colossal loss of life is not a tragedy. 39 00:04:00,880 --> 00:04:04,240 Extinction is a vital part of evolution. 40 00:04:07,560 --> 00:04:09,960 If nothing ever went extinct, 41 00:04:09,960 --> 00:04:13,320 there would be no room for new species to evolve. 42 00:04:14,680 --> 00:04:19,760 Over time, extinction helped create our rich living world. 43 00:04:21,200 --> 00:04:24,040 But our planet walks a tightrope. 44 00:04:25,840 --> 00:04:28,560 If extinction goes unchecked, 45 00:04:28,560 --> 00:04:32,160 the complex web of life crumbles. 46 00:04:37,080 --> 00:04:42,040 Imagine 90% of species suddenly dying - 47 00:04:42,040 --> 00:04:46,400 not just a few endangered plants or animals becoming extinct, 48 00:04:46,400 --> 00:04:49,000 or a handful of ecosystems disappearing, 49 00:04:49,000 --> 00:04:54,320 but nine out of ten living things wiped off the face of the Earth. 50 00:04:58,880 --> 00:05:03,600 Imagine what that Earth would look like in the aftermath - 51 00:05:03,600 --> 00:05:08,120 shattered, broken, bereft of the beautiful complexity 52 00:05:08,120 --> 00:05:10,080 that we take for granted today. 53 00:05:13,440 --> 00:05:18,880 We may think modern climate change is our planet's darkest hour, 54 00:05:18,880 --> 00:05:21,560 or the loss of the dinosaurs, 55 00:05:21,560 --> 00:05:24,280 but the Earth has seen worse. 56 00:05:26,000 --> 00:05:30,280 This is the story of the greatest mass extinction event 57 00:05:30,280 --> 00:05:31,840 in Earth's history. 58 00:05:36,760 --> 00:05:42,680 Something caused our planet's life-support systems to fail, 59 00:05:42,680 --> 00:05:47,440 wiping out most of the species on Earth. 60 00:05:48,840 --> 00:05:51,840 And this is not an apocalyptic vision, 61 00:05:51,840 --> 00:05:53,800 not a doomsday prophesy. 62 00:05:53,800 --> 00:05:56,360 This actually happened. 63 00:05:56,360 --> 00:06:00,000 252 million years ago, 64 00:06:00,000 --> 00:06:05,200 the Earth turned on the life that it had nurtured for so long. 65 00:06:09,280 --> 00:06:14,520 What does it take to destroy almost all life on Earth? 66 00:06:18,360 --> 00:06:20,360 And could it happen again? 67 00:06:26,000 --> 00:06:29,560 Well, the answer lies in Earth's deep history... 68 00:06:35,800 --> 00:06:40,440 ..in a time long before humans transformed the planet's surface... 69 00:06:46,000 --> 00:06:48,600 ..before the last Ice Age... 70 00:06:53,360 --> 00:06:57,480 ..before the asteroid impact wiped out the dinosaurs... 71 00:07:03,360 --> 00:07:07,400 ..in fact, back to a time before dinosaurs 72 00:07:07,400 --> 00:07:09,480 even existed at all. 73 00:07:28,720 --> 00:07:34,880 From space, the Earth in the Late Permian is a strange sight. 74 00:07:34,880 --> 00:07:38,240 From one side, a water world, 75 00:07:38,240 --> 00:07:39,880 no land in sight. 76 00:07:45,480 --> 00:07:50,760 But as the planet turns, something else creeps into view... 77 00:07:54,160 --> 00:07:59,000 ..all the Earth's major landmasses clustered as one. 78 00:08:00,800 --> 00:08:03,600 This is Pangea... 79 00:08:08,680 --> 00:08:12,280 ..a supercontinent rich with life. 80 00:08:18,880 --> 00:08:23,440 Coastal waters teem with weird and wonderful creatures. 81 00:08:26,160 --> 00:08:28,640 At once both alien, 82 00:08:28,640 --> 00:08:31,320 yet eerily familiar. 83 00:08:35,120 --> 00:08:41,680 And in lush forests, a cacophony of animal cries fill the air. 84 00:09:09,480 --> 00:09:12,840 In many ways, the Earth in the Late Permian 85 00:09:12,840 --> 00:09:15,120 was like the Earth we have today - 86 00:09:15,120 --> 00:09:18,280 millions of species of plants and animals, living together 87 00:09:18,280 --> 00:09:20,720 in complex, interconnected webs 88 00:09:20,720 --> 00:09:24,000 which are nurturing and self-sustaining. 89 00:09:24,000 --> 00:09:28,600 But in other ways, it was a very alien world. 90 00:09:28,600 --> 00:09:35,520 This was a time long before mammals or even dinosaurs walked the Earth. 91 00:09:35,520 --> 00:09:39,520 But life was no less remarkable. 92 00:09:39,520 --> 00:09:42,440 Scuttling around in the scrub of the Late Permian, 93 00:09:42,440 --> 00:09:44,520 you might have found one of these. 94 00:09:44,520 --> 00:09:49,040 This is the cast of a beautiful fossil of Nycteroleter. 95 00:09:49,040 --> 00:09:53,920 It's part of an extinct group of reptiles, and fed on things 96 00:09:53,920 --> 00:09:57,520 like proto-cockroaches, dragonflies, millipedes. 97 00:09:57,520 --> 00:09:58,800 It's got quite large eyes, 98 00:09:58,800 --> 00:10:00,960 suggesting that it might have been nocturnal, 99 00:10:00,960 --> 00:10:04,960 and we also know that it had really good hearing - 100 00:10:04,960 --> 00:10:07,640 something quite unique for animals of that time. 101 00:10:08,800 --> 00:10:11,040 But then, look at this chap. 102 00:10:11,040 --> 00:10:12,760 It's Dvinia. 103 00:10:12,760 --> 00:10:14,680 It would've grown to about 50 centimetres. 104 00:10:14,680 --> 00:10:16,840 Looked like a small dog. 105 00:10:16,840 --> 00:10:20,920 Neither a mammal, nor a reptile, it's got forward-facing eyes. 106 00:10:20,920 --> 00:10:23,760 It was perhaps a predator of some kind. 107 00:10:23,760 --> 00:10:27,360 But, look, from the top, you can see it's got really wide cheeks, 108 00:10:27,360 --> 00:10:30,680 and the remains here of perhaps a sagittal crest, 109 00:10:30,680 --> 00:10:34,280 suggesting that it had very powerful muscles, a powerful bite. 110 00:10:34,280 --> 00:10:38,280 In fact, it might have been fishing for shellfish down on the beach 111 00:10:38,280 --> 00:10:42,080 and crunching them up with its powerful jaws. 112 00:10:42,080 --> 00:10:45,160 But last, and perhaps most impressive, 113 00:10:45,160 --> 00:10:51,760 this is a magnificent specimen of a super predator, Inostrancevia. 114 00:10:51,760 --> 00:10:53,120 What an animal. 115 00:10:53,120 --> 00:10:56,440 Just look at those sabre-tooth teeth there. 116 00:10:56,440 --> 00:10:58,040 Now, those are slashing tools. 117 00:10:58,040 --> 00:11:01,880 Those are for wounding prey, waiting for it to bleed to death, 118 00:11:01,880 --> 00:11:06,320 and then catching up with it and swallowing large chunks whole. 119 00:11:06,320 --> 00:11:09,160 This animal would've grown to about 3 metres in length 120 00:11:09,160 --> 00:11:11,040 and very fast-moving 121 00:11:11,040 --> 00:11:15,120 and been terrorising the large herbivores of its time. 122 00:11:15,120 --> 00:11:17,880 What a fantastic beast it must have been. 123 00:11:20,560 --> 00:11:22,480 But by the end of the Permian, 124 00:11:22,480 --> 00:11:26,080 along with nearly every other living thing on Earth, 125 00:11:26,080 --> 00:11:28,280 they would be dead. 126 00:11:50,040 --> 00:11:52,920 We're not certain how it started, 127 00:11:52,920 --> 00:11:56,360 but deep inside the ancient Earth, 128 00:11:56,360 --> 00:11:59,600 superheated rock is rising... 129 00:12:01,880 --> 00:12:05,520 ..pushing upwards against the solid outer crust... 130 00:12:09,320 --> 00:12:12,640 ..until it can take no more. 131 00:12:17,240 --> 00:12:19,200 The crust fails. 132 00:12:29,760 --> 00:12:33,160 The landscape physically torn apart, 133 00:12:33,160 --> 00:12:35,600 as lava floods onto the surface... 134 00:12:36,800 --> 00:12:39,920 ..forming great curtains of fire. 135 00:12:45,040 --> 00:12:49,880 This is just the beginning of the most deadly volcanic event 136 00:12:49,880 --> 00:12:51,280 in Earth's history. 137 00:13:01,720 --> 00:13:05,560 We can get clues to what these ancient eruptions were like 138 00:13:05,560 --> 00:13:08,000 by studying modern volcanoes. 139 00:13:16,120 --> 00:13:19,880 This is Tajogaite Volcano, in the Canary Islands, 140 00:13:19,880 --> 00:13:23,800 and in September of 2021, the ground here split 141 00:13:23,800 --> 00:13:28,360 and tonnes of lava, ash and toxic gases exploded, 142 00:13:28,360 --> 00:13:30,960 shaking the entire island. 143 00:13:40,000 --> 00:13:41,760 Over three months, 144 00:13:41,760 --> 00:13:48,720 170 million cubic metres of lava poured onto the surface. 145 00:13:51,120 --> 00:13:55,040 It was the first eruption on the island in 50 years. 146 00:14:02,960 --> 00:14:07,360 More than 7,000 people had to flee their homes. 147 00:14:19,800 --> 00:14:23,200 This volcano spewed out enough lava to fill around 148 00:14:23,200 --> 00:14:26,200 70,000 Olympic-sized swimming pools, 149 00:14:26,200 --> 00:14:30,160 and that lava covered an area around ten square kilometres - 150 00:14:30,160 --> 00:14:32,280 which sounds pretty impressive, 151 00:14:32,280 --> 00:14:38,320 but it's just a teaspoon compared to those at the end of the Permian. 152 00:14:38,320 --> 00:14:40,960 252 million years ago, 153 00:14:40,960 --> 00:14:47,520 around four million cubic kilometres of lava, ash and toxic gases 154 00:14:47,520 --> 00:14:51,160 erupted in a series of volcanic explosions 155 00:14:51,160 --> 00:14:55,200 that went on for 2 million years. 156 00:14:55,200 --> 00:14:59,760 The Permian eruptions were 1,000 times greater than 157 00:14:59,760 --> 00:15:01,840 any witnessed by humans. 158 00:15:03,520 --> 00:15:07,400 And the ancient lava is still with us. 159 00:15:07,400 --> 00:15:09,520 In Northwestern Siberia, 160 00:15:09,520 --> 00:15:13,800 beneath a landscape of swamps and flood plains, 161 00:15:13,800 --> 00:15:18,440 scientists have discovered a colossal lava field, 162 00:15:18,440 --> 00:15:23,000 dated a little over 250 million years old... 163 00:15:25,240 --> 00:15:28,800 ..lava that covers over two-and-a-half million 164 00:15:28,800 --> 00:15:30,320 square kilometres... 165 00:15:32,960 --> 00:15:38,040 ..enough to bury the entire continent of Australia 166 00:15:38,040 --> 00:15:40,040 hundreds of metres deep. 167 00:15:46,360 --> 00:15:53,600 252 million years ago, Northern Pangea was hell on Earth. 168 00:15:57,800 --> 00:16:03,000 Fire fountains blast volcanic material over six miles up 169 00:16:03,000 --> 00:16:04,360 into the atmosphere... 170 00:16:08,200 --> 00:16:12,040 ..burning millions of square miles of forests. 171 00:16:21,680 --> 00:16:25,720 And clouds bloom high into the atmosphere, 172 00:16:25,720 --> 00:16:27,400 blocking out the sun. 173 00:16:32,360 --> 00:16:34,960 Plants wilt and die... 174 00:16:40,200 --> 00:16:42,640 ..ash falls like snow... 175 00:16:46,800 --> 00:16:52,560 ..as vast swathes of Northern Pangea lie in ruins. 176 00:17:01,720 --> 00:17:06,320 These eruptions are on a scale almost beyond imagination. 177 00:17:08,560 --> 00:17:15,520 But lava still only covers less than 1% of Pangea's surface. 178 00:17:15,520 --> 00:17:19,920 And elsewhere, something curious is happening. 179 00:17:24,680 --> 00:17:28,360 A strange haze hangs in the air. 180 00:17:34,880 --> 00:17:38,720 Nutrient-rich volcanic ash and sulphur, 181 00:17:38,720 --> 00:17:44,400 transported thousands of miles, reflect the sun's rays... 182 00:17:46,000 --> 00:17:49,200 ..pushing global temperatures down... 183 00:17:56,200 --> 00:18:01,320 ..and in places, causing a surge of plant life to flourish. 184 00:18:07,480 --> 00:18:10,040 But death is coming. 185 00:18:26,120 --> 00:18:29,440 I've come to an outcrop in Northern Italy, 186 00:18:29,440 --> 00:18:35,200 made of rock that formed at the same time as those ancient eruptions. 187 00:18:38,240 --> 00:18:41,480 It's a fossilised crime scene 188 00:18:41,480 --> 00:18:44,400 with a chilling tale to tell. 189 00:18:46,600 --> 00:18:52,520 Look at this thin, black seam that runs all the way down here. 190 00:18:55,320 --> 00:18:57,560 It looks like coal to me, 191 00:18:57,560 --> 00:19:00,400 which would indicate that at one point... 192 00:19:02,240 --> 00:19:03,800 ..it was full of plant life. 193 00:19:03,800 --> 00:19:05,880 Probably full of lots of other life, too. 194 00:19:07,800 --> 00:19:11,160 Coal is little more than ancient organic matter 195 00:19:11,160 --> 00:19:14,760 that's been subjected to extreme temperatures and pressures 196 00:19:14,760 --> 00:19:17,080 over millions of years. 197 00:19:17,080 --> 00:19:19,600 So, where we find coal today, 198 00:19:19,600 --> 00:19:22,520 we know there was once life. 199 00:19:22,520 --> 00:19:26,440 But the rocks above it here tell an altogether different story. 200 00:19:32,920 --> 00:19:36,040 They're grey, dull, look a bit boring, 201 00:19:36,040 --> 00:19:38,560 a bit of a geological mush. 202 00:19:38,560 --> 00:19:40,720 But that's the point - 203 00:19:40,720 --> 00:19:44,840 because, aside from a few fossil microorganisms, 204 00:19:44,840 --> 00:19:50,520 scientists have found very little evidence of life in these rocks. 205 00:19:50,520 --> 00:19:56,080 So, what they are telling us is that 252 million years ago, 206 00:19:56,080 --> 00:19:59,840 the landscape here was almost devoid of life. 207 00:20:02,360 --> 00:20:08,920 In a geological blink of an eye, almost all life here vanished. 208 00:20:08,920 --> 00:20:12,760 You can't help but feel a certain sense of sadness. 209 00:20:12,760 --> 00:20:16,200 Holding this makes it so tangible. 210 00:20:19,240 --> 00:20:23,520 This was death on an unimaginable scale. 211 00:20:25,160 --> 00:20:29,280 But there's no evidence of lava here at all. 212 00:20:30,960 --> 00:20:34,480 When these rocks were laid down in this part of Italy, 213 00:20:34,480 --> 00:20:38,360 they were thousands of miles away from the eruptions in the north - 214 00:20:38,360 --> 00:20:42,040 certainly too far away for any direct impacts. 215 00:20:42,040 --> 00:20:44,680 But what's interesting is that geologists 216 00:20:44,680 --> 00:20:49,400 have found this line of death all over the planet - 217 00:20:49,400 --> 00:20:52,400 China, Australia, South Africa. 218 00:20:52,400 --> 00:20:56,080 And no matter how far away from the lava fields, 219 00:20:56,080 --> 00:20:58,760 there's a deathly silence in the fossil record. 220 00:21:01,160 --> 00:21:07,000 The question is, what could have killed this many creatures? 221 00:21:07,000 --> 00:21:12,000 What could have wiped out almost all life on Earth? 222 00:21:31,600 --> 00:21:35,440 Something more than lava was emerging from the Earth 223 00:21:35,440 --> 00:21:37,160 in Northern Pangea. 224 00:21:41,960 --> 00:21:47,360 Billions of tonnes of gases are injected high into the atmosphere. 225 00:21:56,200 --> 00:21:59,360 Water vapour, sulphur dioxide... 226 00:22:01,160 --> 00:22:06,160 ..but primarily a gas we all know too well - 227 00:22:06,160 --> 00:22:09,880 the greenhouse gas carbon dioxide. 228 00:22:30,120 --> 00:22:33,480 We're all becoming depressingly familiar with what happens 229 00:22:33,480 --> 00:22:39,200 when you pump huge quantities of carbon dioxide into the atmosphere. 230 00:22:39,200 --> 00:22:41,520 It's an experiment we've been running ourselves 231 00:22:41,520 --> 00:22:43,600 for more than 100 years. 232 00:22:43,600 --> 00:22:47,960 And the more the CO2, the more the heat is locked in, 233 00:22:47,960 --> 00:22:50,880 and the hotter our Earth becomes. 234 00:22:51,960 --> 00:22:55,520 Global warming isn't a localised effect. 235 00:22:55,520 --> 00:22:58,080 The whole planet feels the burn. 236 00:22:59,320 --> 00:23:00,920 Here we are, yeah, dead ahead. 237 00:23:00,920 --> 00:23:02,960 No creature is safe. 238 00:23:02,960 --> 00:23:06,280 You've got a little feeding party taking place here at the moment. 239 00:23:06,280 --> 00:23:08,480 Oh, look at that! 240 00:23:09,480 --> 00:23:11,880 Oh, yes, yes! 241 00:23:15,240 --> 00:23:18,360 Sorry to be a child, but it's always... 242 00:23:18,360 --> 00:23:20,880 Oh, oh, oh, oh! 243 00:23:20,880 --> 00:23:23,280 Oh, I just saw it catch a fish! 244 00:23:23,280 --> 00:23:24,360 Oh! 245 00:23:25,880 --> 00:23:28,240 There are several species here. 246 00:23:28,240 --> 00:23:29,680 Bottlenose... 247 00:23:31,880 --> 00:23:35,920 ..common, rough tooth, spotted. 248 00:23:37,520 --> 00:23:41,680 And dolphins, of course, can live in much warmer waters than these. 249 00:23:41,680 --> 00:23:44,280 So, you might imagine they're not the sorts of creatures 250 00:23:44,280 --> 00:23:47,400 that would be harmed by global warming. 251 00:23:47,400 --> 00:23:51,600 But sadly, I've got to tell you, these dolphins are in trouble. 252 00:23:57,960 --> 00:24:02,720 It's not always the temperature that poses a danger to life. 253 00:24:02,720 --> 00:24:06,080 In fact, for some, the heat is a blessing. 254 00:24:08,320 --> 00:24:11,000 Let's see what I've managed to catch. 255 00:24:12,440 --> 00:24:14,760 Wow, rather a lot. 256 00:24:14,760 --> 00:24:19,000 This mass of detritus here is plankton, 257 00:24:19,000 --> 00:24:22,160 much of it phytoplankton, algae. 258 00:24:22,160 --> 00:24:25,560 Now, most of the organisms wouldn't hurt anything, 259 00:24:25,560 --> 00:24:29,000 but there is one species, Karenia Brevis - 260 00:24:29,000 --> 00:24:31,760 well, that's an algae with a superpower. 261 00:24:31,760 --> 00:24:34,240 You see, when the water warms up here, 262 00:24:34,240 --> 00:24:37,640 it goes into a reproductive frenzy, 263 00:24:37,640 --> 00:24:41,280 producing blooms many hundreds of times greater 264 00:24:41,280 --> 00:24:43,160 than it normally would. 265 00:24:43,160 --> 00:24:45,440 But what's good for the algae, it turns out, 266 00:24:45,440 --> 00:24:47,960 is not so good for the dolphins. 267 00:24:47,960 --> 00:24:52,760 Because recent research has shown that this is extremely toxic. 268 00:24:52,760 --> 00:24:55,160 So, the small fish eat the algae, 269 00:24:55,160 --> 00:24:57,240 the bigger fish eat the small fish, 270 00:24:57,240 --> 00:24:59,840 the dolphins the larger fish. 271 00:24:59,840 --> 00:25:03,080 And this organism has been implicated 272 00:25:03,080 --> 00:25:05,960 in the deaths of dozens of dolphins, 273 00:25:05,960 --> 00:25:08,400 found dead floating in the sea here. 274 00:25:10,360 --> 00:25:14,800 Rising temperatures affect different parts of the food chain 275 00:25:14,800 --> 00:25:16,920 in different ways, 276 00:25:16,920 --> 00:25:20,760 throwing ecosystems out of balance... 277 00:25:20,760 --> 00:25:23,560 ..often with deadly results. 278 00:25:25,040 --> 00:25:27,360 You see, when it comes to global warming, 279 00:25:27,360 --> 00:25:30,480 it's not the actual heat that kills those creatures. 280 00:25:30,480 --> 00:25:34,680 It's the increases or decreases in plant or animal populations 281 00:25:34,680 --> 00:25:40,480 which disrupt those long-evolved, stable, beautiful ecosystems. 282 00:25:40,480 --> 00:25:46,120 Death by global warming is not short, sharp, and painless. 283 00:25:46,120 --> 00:25:48,880 It's prolonged and torturous. 284 00:26:06,840 --> 00:26:09,880 As the temperatures rise across Pangea... 285 00:26:16,520 --> 00:26:18,600 ..trees begin to die. 286 00:26:33,640 --> 00:26:37,400 Holes appear in the once-thick canopy, 287 00:26:37,400 --> 00:26:40,440 bathing the ground in sunlight. 288 00:26:45,760 --> 00:26:48,360 For some, it's an opportunity. 289 00:26:49,360 --> 00:26:51,400 Weed-like plants flourish, 290 00:26:51,400 --> 00:26:53,680 like spore-bearing lycophytes. 291 00:26:57,040 --> 00:26:59,520 No longer struggling in the shadows, 292 00:26:59,520 --> 00:27:02,240 in times of stress, they thrive. 293 00:27:06,080 --> 00:27:08,880 And foreign species appear. 294 00:27:08,880 --> 00:27:13,480 Woody, seed-bearing cycads that once only grew in the tropics 295 00:27:13,480 --> 00:27:16,240 are now abundant closer to the Poles. 296 00:27:21,360 --> 00:27:26,000 Surprisingly, some areas are now more diverse 297 00:27:26,000 --> 00:27:28,280 than before the warming began. 298 00:27:29,520 --> 00:27:33,840 But this is an ecosystem out of balance. 299 00:27:37,080 --> 00:27:39,240 A few more degrees' warming, 300 00:27:39,240 --> 00:27:41,960 and the living world will crumble. 301 00:27:57,120 --> 00:28:00,800 But then something strange happens. 302 00:28:03,360 --> 00:28:06,560 Red hot rivers of lava... 303 00:28:06,560 --> 00:28:09,200 ..turn to solid rock. 304 00:28:11,160 --> 00:28:13,960 Just as quickly as they started, 305 00:28:13,960 --> 00:28:17,120 the eruptions fall silent. 306 00:28:30,240 --> 00:28:33,400 The CO2 released from the Permian lavas 307 00:28:33,400 --> 00:28:36,720 likely dwarfed human emissions to date. 308 00:28:39,080 --> 00:28:43,360 But even that may have been just part of the story. 309 00:28:47,240 --> 00:28:49,040 These eruptions would have produced 310 00:28:49,040 --> 00:28:51,720 an inordinate amount of carbon dioxide - 311 00:28:51,720 --> 00:28:53,320 gigatons of the stuff, 312 00:28:53,320 --> 00:28:56,160 certainly enough to manifest some global warming, 313 00:28:56,160 --> 00:29:00,240 perhaps in the realm of an increase of 5 or 6 degrees Celsius, 314 00:29:00,240 --> 00:29:02,080 something like that. 315 00:29:02,080 --> 00:29:05,120 Now, that's a substantial amount of heating, 316 00:29:05,120 --> 00:29:08,760 but it's not significant enough to account for all of the deaths 317 00:29:08,760 --> 00:29:11,160 that we see in the fossil record. 318 00:29:11,160 --> 00:29:13,440 Yes, there would have been extinctions, 319 00:29:13,440 --> 00:29:17,160 but not 90% of all life on Earth. 320 00:29:29,000 --> 00:29:32,960 The effects of carbon dioxide can be lethal. 321 00:29:32,960 --> 00:29:36,520 But some scientists think there was another killer. 322 00:29:39,760 --> 00:29:42,720 The volcanism hadn't stopped. 323 00:29:42,720 --> 00:29:46,840 It had just entered a terrifying new phase. 324 00:29:49,720 --> 00:29:52,320 Beneath the desolate lava field... 325 00:29:53,320 --> 00:29:57,080 ..hot magma still flows, 326 00:29:57,080 --> 00:30:00,720 forming great reservoirs underground... 327 00:30:00,720 --> 00:30:04,920 ..and slowly baking the Earth's crust. 328 00:30:17,920 --> 00:30:20,480 The rocks underground were older - 329 00:30:20,480 --> 00:30:24,400 hundreds of millions of years older than the land above. 330 00:30:24,400 --> 00:30:26,640 And amongst them, 331 00:30:26,640 --> 00:30:29,800 there was plenty of this stuff - 332 00:30:29,800 --> 00:30:33,280 coal and other rocks rich in carbon. 333 00:30:33,280 --> 00:30:36,400 Now, what happens when magma meets coal? 334 00:30:36,400 --> 00:30:42,280 Well, the coal burns, releasing yet more dangerous carbon dioxide. 335 00:30:42,280 --> 00:30:44,240 But that was just the half of it. 336 00:30:44,240 --> 00:30:46,840 You see, it wasn't just coal. 337 00:30:46,840 --> 00:30:50,520 There was also lots of salt. 338 00:30:50,520 --> 00:30:56,760 And salt like this can form when ancient lakes and seas dry up. 339 00:30:56,760 --> 00:30:59,880 And when magma comes into contact with salt, 340 00:30:59,880 --> 00:31:02,160 things get really nasty. 341 00:31:04,840 --> 00:31:07,120 The salt begins to bake, 342 00:31:07,120 --> 00:31:12,520 releasing toxic halogen gases rich in bromine and chlorine - 343 00:31:12,520 --> 00:31:17,360 archenemies of the Earth's fragile ozone layer, 344 00:31:17,360 --> 00:31:23,880 that thin layer that protects us from the sun's most harmful rays. 345 00:31:23,880 --> 00:31:28,200 So, what I'm trying to say here is that the magma had found its way 346 00:31:28,200 --> 00:31:32,680 into the worst possible place on the planet. 347 00:31:32,680 --> 00:31:35,240 It had created a time bomb. 348 00:31:41,520 --> 00:31:45,440 That magma begins to heat up the coal and salt 349 00:31:45,440 --> 00:31:49,040 to a temperature of 800 degrees Celsius. 350 00:31:53,320 --> 00:31:56,560 A poisonous cocktail of gases begins to build... 351 00:32:03,520 --> 00:32:07,240 ..until the land above can take no more. 352 00:32:40,440 --> 00:32:43,360 More CO2 floods the atmosphere, 353 00:32:43,360 --> 00:32:46,120 pushing global temperatures even higher. 354 00:32:48,320 --> 00:32:53,800 But this time, there were also those toxic halogen gases. 355 00:33:01,400 --> 00:33:06,560 We've seen the Earth's ozone layer damaged in recent history, 356 00:33:06,560 --> 00:33:11,560 when artificial chemicals created a so-called ozone hole. 357 00:33:13,000 --> 00:33:16,080 But in the Permian, the halogens may have eroded 358 00:33:16,080 --> 00:33:18,840 the ozone layer away entirely... 359 00:33:21,480 --> 00:33:26,320 ..bathing all life in deadly UV radiation. 360 00:33:28,320 --> 00:33:32,040 Scientists have noticed something strange going on with the pollen 361 00:33:32,040 --> 00:33:34,320 at the end of the Permian. 362 00:33:34,320 --> 00:33:36,040 Take a look at this. 363 00:33:36,040 --> 00:33:42,000 This is a highly-magnified image of a modern pine pollen grain. 364 00:33:42,000 --> 00:33:44,760 And you can see it's got two essential parts to its structure - 365 00:33:44,760 --> 00:33:47,560 the central circular part here, the corpus, 366 00:33:47,560 --> 00:33:49,840 and then these winged sacchi. 367 00:33:49,840 --> 00:33:53,800 These are wind-pollinated pollen species, 368 00:33:53,800 --> 00:33:56,320 and these help it float through the air. 369 00:33:56,320 --> 00:33:58,640 But have a look at this. 370 00:33:58,640 --> 00:34:02,160 This is an image of a fossilised coniferous pollen grain 371 00:34:02,160 --> 00:34:04,280 from the time of those eruptions. 372 00:34:04,280 --> 00:34:08,000 It's got three of these wing structures. 373 00:34:08,000 --> 00:34:10,920 This one has four. 374 00:34:10,920 --> 00:34:15,040 These pollen grains are malformed, misshapen and, in fact, 375 00:34:15,040 --> 00:34:17,080 if you look at this last one, 376 00:34:17,080 --> 00:34:20,960 this appear to have been in the process of dividing, 377 00:34:20,960 --> 00:34:23,400 but somehow it's failed. 378 00:34:23,400 --> 00:34:26,440 These are mutant pollen grains, 379 00:34:26,440 --> 00:34:29,760 and it's thought that the mutation was caused by 380 00:34:29,760 --> 00:34:32,560 the excessive UV radiation - 381 00:34:32,560 --> 00:34:38,800 evidence that those gases had really damaged the Earth's ozone layer. 382 00:34:38,800 --> 00:34:40,960 Now, other theories are available. 383 00:34:40,960 --> 00:34:43,520 Others believe that, in fact, it was acid rain 384 00:34:43,520 --> 00:34:48,200 that caused these mutations, or merely the extreme heat. 385 00:34:48,200 --> 00:34:50,280 But whatever the cause, 386 00:34:50,280 --> 00:34:55,040 what's clear is that at this point, life was on the brink. 387 00:35:10,440 --> 00:35:15,160 At first glance, it seems nothing has changed. 388 00:35:15,160 --> 00:35:18,480 But this already fragile ecosystem 389 00:35:18,480 --> 00:35:23,320 has taken a lethal dose of UV radiation. 390 00:35:23,320 --> 00:35:27,040 Healthy-looking plants are now sterile. 391 00:35:29,560 --> 00:35:33,440 As individuals die, they aren't replaced. 392 00:35:38,000 --> 00:35:42,560 Once-lush forests become ravaged wastelands. 393 00:35:49,600 --> 00:35:54,280 The collapse in the oceans is even more dramatic. 394 00:35:54,280 --> 00:35:57,240 Carbon dioxide reacts with sea water, 395 00:35:57,240 --> 00:35:59,600 which begins to turn to acid. 396 00:36:04,520 --> 00:36:07,440 And oxygen levels plummet - 397 00:36:07,440 --> 00:36:10,680 in some places, dropping to zero. 398 00:36:13,560 --> 00:36:16,160 Algae blooms across the planet. 399 00:36:17,880 --> 00:36:21,120 As it decomposes, it poisons the ocean 400 00:36:21,120 --> 00:36:24,080 with toxic hydrogen sulphide... 401 00:36:34,000 --> 00:36:40,440 ..until the seafloor becomes a foetid bed of slime. 402 00:36:44,240 --> 00:36:47,720 Sulphurous tides lap barren shores, 403 00:36:47,720 --> 00:36:51,120 and a smell like rotten eggs hangs in the air. 404 00:36:53,400 --> 00:36:58,200 The Earth's rich complexity has vanished, 405 00:36:58,200 --> 00:37:00,440 seemingly for good. 406 00:37:13,520 --> 00:37:15,600 It's been called many things - 407 00:37:15,600 --> 00:37:20,000 the Great Dying, the mother of all mass extinction events 408 00:37:20,000 --> 00:37:24,000 or, simply, when life nearly died. 409 00:37:24,000 --> 00:37:27,120 The details are still a bit hazy. 410 00:37:27,120 --> 00:37:30,840 Was it a single short, sharp, giant catastrophe, 411 00:37:30,840 --> 00:37:34,200 or a wave of smaller catastrophes? 412 00:37:34,200 --> 00:37:37,360 To what extent did the extinctions occur on land 413 00:37:37,360 --> 00:37:40,480 versus extinctions in the water? 414 00:37:40,480 --> 00:37:42,720 The fossil record is patchy, 415 00:37:42,720 --> 00:37:45,000 so there's plenty of room for academic debate. 416 00:37:45,000 --> 00:37:49,160 But the one thing that almost everyone agrees upon 417 00:37:49,160 --> 00:37:53,000 is that these ancient eruptions caused extinctions 418 00:37:53,000 --> 00:37:55,920 on an unprecedented scale. 419 00:37:55,920 --> 00:38:01,800 Figures frequently cited suggest that 70% of land vertebrates 420 00:38:01,800 --> 00:38:06,040 and 96% of marine life 421 00:38:06,040 --> 00:38:09,720 vanished off the face of the Earth forever. 422 00:38:12,160 --> 00:38:15,520 By the time the eruptions finally stop, 423 00:38:15,520 --> 00:38:20,760 the average global temperature has risen by over 10 degrees Celsius. 424 00:38:23,400 --> 00:38:29,800 Vast areas of the Earth's surface are completely uninhabitable, 425 00:38:29,800 --> 00:38:33,400 and nearly all species are gone. 426 00:38:42,000 --> 00:38:47,240 The End-Permian extinction has a virtually undisputed claim 427 00:38:47,240 --> 00:38:51,840 to being the worst moment in the history of the Earth. 428 00:38:52,960 --> 00:38:57,640 But from the ashes, there was a glimmer of hope, 429 00:38:57,640 --> 00:39:00,520 because life had survived somewhere. 430 00:39:00,520 --> 00:39:04,920 It must have. Otherwise, we wouldn't be here. 431 00:39:06,400 --> 00:39:11,160 In a way, we are all survivors of the Great Dying. 432 00:39:11,160 --> 00:39:17,680 You see, every living organism on the planet has an ancient ancestor, 433 00:39:17,680 --> 00:39:21,360 perhaps millions, perhaps billions of generations back, 434 00:39:21,360 --> 00:39:24,800 that not only survived that mass extinction event 435 00:39:24,800 --> 00:39:28,560 but then went on to prosper in the aftermath 436 00:39:28,560 --> 00:39:31,640 and then to repopulate the Earth. 437 00:39:34,640 --> 00:39:38,400 The Great Dying may have been the end of one world, 438 00:39:38,400 --> 00:39:42,240 but it was also the beginning of a new one. 439 00:39:53,120 --> 00:39:57,240 The Triassic Earth is a shadow of its former self. 440 00:40:01,960 --> 00:40:05,080 Many creatures seek refuge underground... 441 00:40:11,000 --> 00:40:13,880 ..sheltering from blistering temperatures 442 00:40:13,880 --> 00:40:16,240 and lethal UV radiation. 443 00:40:21,600 --> 00:40:26,960 Above ground, a single plant species dominates the landscape. 444 00:40:28,160 --> 00:40:32,440 Pleuromeia - a weed-like plant lucky enough to make it 445 00:40:32,440 --> 00:40:37,080 through the apocalypse and find itself with few competitors. 446 00:40:41,040 --> 00:40:44,040 It helps provide sustenance for the cockroaches, 447 00:40:44,040 --> 00:40:46,880 who also made it through unscathed. 448 00:40:51,840 --> 00:40:55,120 But just because the eruptions have stopped 449 00:40:55,120 --> 00:40:59,200 doesn't mean that life's troubles are over. 450 00:41:12,120 --> 00:41:15,800 The Early Triassic was dominated by extreme heat. 451 00:41:15,800 --> 00:41:19,200 The fossil record shows us that ocean temperatures could have been 452 00:41:19,200 --> 00:41:22,000 up to 14 degrees centigrade warmer 453 00:41:22,000 --> 00:41:24,360 than they were prior to the eruptions. 454 00:41:24,360 --> 00:41:28,720 In some places, the water was as warm as it is in a hot tub - 455 00:41:28,720 --> 00:41:31,680 too extreme for most marine organisms. 456 00:41:35,480 --> 00:41:38,960 And on land, things weren't faring much better. 457 00:41:38,960 --> 00:41:43,040 There were probably heatwaves of up to 60 degrees centigrade - 458 00:41:43,040 --> 00:41:47,480 a temperature that would have seriously inhibited photosynthesis. 459 00:41:47,480 --> 00:41:53,080 In fact, for the 10 million years following the mass extinction event, 460 00:41:53,080 --> 00:41:58,320 we see no significant coal reserves laid down anywhere on Earth. 461 00:41:58,320 --> 00:42:02,400 There simply weren't enough trees. 462 00:42:02,400 --> 00:42:07,440 For life to bounce back, the planet needed to cool down. 463 00:42:14,920 --> 00:42:18,800 In normal times, the Earth can cool itself - 464 00:42:18,800 --> 00:42:22,120 over thousands of years, removing carbon dioxide 465 00:42:22,120 --> 00:42:26,480 from the atmosphere, in part through reacting with rainwater. 466 00:42:27,760 --> 00:42:31,960 But vast areas of Pangea are desert. 467 00:42:31,960 --> 00:42:33,600 Little rain falls. 468 00:42:36,840 --> 00:42:41,440 So, it takes millions of years for temperatures to drop. 469 00:42:52,880 --> 00:42:56,880 And even then, recovery is slow. 470 00:43:00,920 --> 00:43:05,960 The living world's struggling to regain the diversity it once knew. 471 00:43:16,960 --> 00:43:19,560 But salvation was coming. 472 00:43:25,120 --> 00:43:31,400 High in the Dolomite Mountains is evidence for a bizarre event, 473 00:43:31,400 --> 00:43:35,000 one that may have helped life rebound. 474 00:43:38,320 --> 00:43:40,240 Look at this. 475 00:43:40,240 --> 00:43:43,280 Absolutely stunning. 476 00:43:43,280 --> 00:43:49,080 And these mountains were formed very shortly after the extinction event, 477 00:43:49,080 --> 00:43:52,440 and they're made up of sedimentary rock - 478 00:43:52,440 --> 00:43:55,320 layers of sediment on top of one another, 479 00:43:55,320 --> 00:43:59,000 each corresponding to a time in the Earth's history. 480 00:43:59,000 --> 00:44:01,280 The oldest rocks are at the bottom, 481 00:44:01,280 --> 00:44:03,520 around 238 million years old. 482 00:44:03,520 --> 00:44:05,320 The youngest at the top, 483 00:44:05,320 --> 00:44:08,240 about 200 million years old. 484 00:44:08,240 --> 00:44:11,400 Now, you might imagine that if we wanted to uncover the secrets 485 00:44:11,400 --> 00:44:14,200 in these rocks, we'd take some, break them open 486 00:44:14,200 --> 00:44:17,120 and look for some details - but not here. 487 00:44:17,120 --> 00:44:21,920 The secrets in these rocks are held in plain view. 488 00:44:21,920 --> 00:44:25,320 The key is the shape of the mountains. 489 00:44:25,320 --> 00:44:30,280 It hints at a planetary intervention that, just a few decades ago, 490 00:44:30,280 --> 00:44:33,440 we had no idea happened. 491 00:44:33,440 --> 00:44:38,480 Look, it starts steep at the bottom, rises sharply, 492 00:44:38,480 --> 00:44:40,760 and then there's a shallow shelf, 493 00:44:40,760 --> 00:44:44,440 and then it rises steeply again to the peak, 494 00:44:44,440 --> 00:44:46,480 currently in the clouds. 495 00:44:46,480 --> 00:44:51,000 But the bit that we're interested in is that shallow slope, 496 00:44:51,000 --> 00:44:56,400 which corresponds to about 2 million years in the Earth's history, 497 00:44:56,400 --> 00:44:59,320 and to a very strange period of time. 498 00:45:01,040 --> 00:45:05,520 This shallow slope is evidence of a softer rock type 499 00:45:05,520 --> 00:45:07,920 that's been eroded over the years. 500 00:45:10,320 --> 00:45:11,640 Here we go. 501 00:45:15,680 --> 00:45:18,400 This is a lump of sandstone. 502 00:45:18,400 --> 00:45:21,200 It's a soft sedimentary rock. 503 00:45:21,200 --> 00:45:23,320 The key is in the name. 504 00:45:23,320 --> 00:45:27,680 It's made up of sediments, like sand, which wash off of the land, 505 00:45:27,680 --> 00:45:31,160 down into the rivers and then down into the sea. 506 00:45:31,160 --> 00:45:34,680 So, what I'm holding here is evidence of rain - 507 00:45:34,680 --> 00:45:36,280 rather a lot of rain, 508 00:45:36,280 --> 00:45:40,920 because in places, this layer is about 80 metres deep. 509 00:45:42,600 --> 00:45:44,840 Sandstone is a common rock, 510 00:45:44,840 --> 00:45:47,880 but scientists have discovered similar layers 511 00:45:47,880 --> 00:45:50,280 right across the planet, 512 00:45:50,280 --> 00:45:55,320 leading some to think this was the result of a global deluge. 513 00:45:56,800 --> 00:45:59,680 Now, we're not precisely sure why it started. 514 00:45:59,680 --> 00:46:02,600 It could have been underwater volcanic activity 515 00:46:02,600 --> 00:46:04,640 disrupting the water cycle. 516 00:46:04,640 --> 00:46:07,160 But at some point in the Triassic, 517 00:46:07,160 --> 00:46:11,880 a time famed for being excruciatingly hot and arid, 518 00:46:11,880 --> 00:46:14,040 it started to rain. 519 00:46:14,040 --> 00:46:17,640 And, boy, did it rain - because that rain 520 00:46:17,640 --> 00:46:22,880 defined the Earth's climate for almost 2 million years. 521 00:46:36,440 --> 00:46:40,960 18 million years after the mass extinction, 522 00:46:40,960 --> 00:46:42,680 the heavens open... 523 00:46:45,000 --> 00:46:48,920 ..a sudden increase in rainfall across Pangea. 524 00:46:51,440 --> 00:46:54,080 The rain causes more extinctions... 525 00:46:55,960 --> 00:46:58,360 ..but the planet is reborn. 526 00:47:06,840 --> 00:47:09,800 Where arid shrub land once stood... 527 00:47:11,320 --> 00:47:14,000 ..lush forests now grow. 528 00:47:15,600 --> 00:47:19,840 It's been called the greening of Triassic Earth, 529 00:47:19,840 --> 00:47:24,440 and it marked the beginning of much of the life we know today. 530 00:47:36,400 --> 00:47:38,840 There were new species of crocodiles... 531 00:47:40,960 --> 00:47:42,920 ..amphibians... 532 00:47:46,080 --> 00:47:49,680 ..even early ancestors of modern mammals. 533 00:48:00,000 --> 00:48:03,360 But the mammals would have to wait in the wings. 534 00:48:03,360 --> 00:48:07,640 Other creatures were set to inherit this renewed world. 535 00:48:14,840 --> 00:48:16,160 Look at this. 536 00:48:17,800 --> 00:48:19,520 See this impression in the rock here? 537 00:48:19,520 --> 00:48:24,680 Look, there are one, two, three toes. 538 00:48:24,680 --> 00:48:27,440 This is a dinosaur footprint, 539 00:48:27,440 --> 00:48:31,080 and I love the fact that I can put my hand 540 00:48:31,080 --> 00:48:34,080 where a dinosaur once put its foot. 541 00:48:34,080 --> 00:48:37,680 Now, whether dinosaurs existed before the rains, we can't be sure. 542 00:48:37,680 --> 00:48:40,960 If they did, it was only as an obscure group 543 00:48:40,960 --> 00:48:42,720 in the south of Pangea. 544 00:48:42,720 --> 00:48:45,360 But in the millions of years after the rains, 545 00:48:45,360 --> 00:48:46,840 they certainly prospered. 546 00:48:46,840 --> 00:48:53,160 In some places, 90% of the vertebrate fossils are dinosaurs. 547 00:48:53,160 --> 00:48:55,360 Why did they suddenly do so well? 548 00:48:55,360 --> 00:48:57,000 Well, it could be down to the food. 549 00:48:57,000 --> 00:49:01,120 They could use it more efficiently to grow bigger more quickly. 550 00:49:01,120 --> 00:49:03,240 But whatever the reason, 551 00:49:03,240 --> 00:49:06,360 dinosaurs went on to dominate the Earth. 552 00:49:07,440 --> 00:49:08,640 I love this! 553 00:49:15,280 --> 00:49:17,520 By the end of the Triassic, 554 00:49:17,520 --> 00:49:21,720 the stage is set for the reptiles to rule supreme. 555 00:49:26,040 --> 00:49:32,080 This will be their world for the next 140 million years. 556 00:49:35,520 --> 00:49:38,600 The age of the dinosaurs is dawning. 557 00:49:51,480 --> 00:49:55,040 In one way, the End-Permian extinction 558 00:49:55,040 --> 00:49:59,400 exposed the fundamental fragility of life. 559 00:49:59,400 --> 00:50:02,520 Countless species of plants and animals were wiped out 560 00:50:02,520 --> 00:50:04,440 by those volcanic eruptions, 561 00:50:04,440 --> 00:50:07,600 and it took millions of years to recover. 562 00:50:07,600 --> 00:50:11,440 But perhaps the event also taught us another lesson 563 00:50:11,440 --> 00:50:13,960 about the tenacity of life - 564 00:50:13,960 --> 00:50:18,360 because the living world did bounce back, to be just as complex 565 00:50:18,360 --> 00:50:22,760 and just as beautiful, in fact, maybe even more so. 566 00:50:29,480 --> 00:50:33,280 But there's a big unspoken question here. 567 00:50:33,280 --> 00:50:37,160 For over 100 years, we've been pumping carbon dioxide into 568 00:50:37,160 --> 00:50:41,760 the atmosphere and watching as global temperatures creep up. 569 00:50:43,440 --> 00:50:49,880 So, what can the mass extinction 252 million years ago teach us 570 00:50:49,880 --> 00:50:52,840 about our own climate change event? 571 00:50:58,560 --> 00:51:03,360 I think the big lesson we've just learned is that the living world 572 00:51:03,360 --> 00:51:05,720 will ultimately be fine. 573 00:51:05,720 --> 00:51:09,880 Even if we don't address our climate and biodiversity crisis, 574 00:51:09,880 --> 00:51:13,560 if we burn every last lump of coal and drop of oil, 575 00:51:13,560 --> 00:51:17,080 if we leave this place as a complete hellscape, 576 00:51:17,080 --> 00:51:21,480 whilst we might perish, life will bounce back, 577 00:51:21,480 --> 00:51:25,640 and this will all be beautiful again - 578 00:51:25,640 --> 00:51:27,360 which begs the question, 579 00:51:27,360 --> 00:51:31,160 "Should we bother to preserve and protect it?" 580 00:51:31,160 --> 00:51:35,800 Well, that extinction event 252 million years ago 581 00:51:35,800 --> 00:51:37,880 was part of a planetary process. 582 00:51:37,880 --> 00:51:40,560 It was a chance volcanic eruption. 583 00:51:43,480 --> 00:51:45,400 Think of all of that suffering. 584 00:51:45,400 --> 00:51:47,520 Think of all of that wastage. 585 00:51:50,120 --> 00:51:54,480 Do we want those sorts of extinctions on our conscience? 586 00:51:56,120 --> 00:51:57,360 I don't think so. 587 00:52:16,480 --> 00:52:21,120 In this episode, we saw how an Earth-shattering eruption 588 00:52:21,120 --> 00:52:24,400 destroyed almost all life on Earth. 589 00:52:29,240 --> 00:52:31,960 This is the closest our planet has ever been 590 00:52:31,960 --> 00:52:33,640 to going back to square one. 591 00:52:35,840 --> 00:52:38,000 To understand the scale of the event, 592 00:52:38,000 --> 00:52:41,560 scientists mapped the Permian lava fields of Russia - 593 00:52:41,560 --> 00:52:44,600 known as the Siberian Traps. 594 00:52:46,440 --> 00:52:50,200 I have actually been to the Siberian Traps 595 00:52:50,200 --> 00:52:53,000 and flown helicopters. 596 00:52:54,360 --> 00:52:58,720 The helicopter is right, mm...there. 597 00:52:58,720 --> 00:53:02,760 Floated on boats, hiked, 598 00:53:02,760 --> 00:53:07,520 ridden on trains all over Arctic Siberia, 599 00:53:07,520 --> 00:53:10,800 looking for remnants of the Siberian Traps. 600 00:53:12,120 --> 00:53:17,800 And these lava flows go distances that boggle the mind. 601 00:53:17,800 --> 00:53:23,440 The 1 million cubic miles that we have is probably a minimum number, 602 00:53:23,440 --> 00:53:26,600 and it's a minimum because not all of the rocks 603 00:53:26,600 --> 00:53:28,720 are exposed at the surface. 604 00:53:28,720 --> 00:53:32,080 We also sampled the rocks of the Siberian Traps 605 00:53:32,080 --> 00:53:35,160 with sledgehammers and rock hammers 606 00:53:35,160 --> 00:53:36,960 and a lot of hard work. 607 00:53:39,000 --> 00:53:41,920 The rock samples were key to understanding 608 00:53:41,920 --> 00:53:45,920 why the Earth's climate changed so dramatically. 609 00:53:45,920 --> 00:53:49,040 When magma comes up from deep within the Earth, 610 00:53:49,040 --> 00:53:52,080 it has gases dissolved in it, 611 00:53:52,080 --> 00:53:55,960 gases like carbon dioxide and sulphur dioxide. 612 00:53:55,960 --> 00:53:59,040 These gases come out into bubbles, 613 00:53:59,040 --> 00:54:03,920 a bit like when you take the lid off a soda bottle and it fizzes. 614 00:54:03,920 --> 00:54:08,720 But these gases told a contradictory story. 615 00:54:08,720 --> 00:54:12,280 Sulphur dioxide and carbon dioxide have opposite effects 616 00:54:12,280 --> 00:54:14,120 on the Earth's atmosphere. 617 00:54:14,120 --> 00:54:17,760 Sulphur dioxide reflects sunlight back into outer space, 618 00:54:17,760 --> 00:54:19,360 causing global cooling, 619 00:54:19,360 --> 00:54:21,920 whereas carbon dioxide is a greenhouse gas 620 00:54:21,920 --> 00:54:23,520 and can lead to global warming. 621 00:54:25,960 --> 00:54:29,520 It turns out that different volcanic gases hang around in our atmosphere 622 00:54:29,520 --> 00:54:31,040 for different amounts of time 623 00:54:31,040 --> 00:54:35,360 because of their different chemical properties. 624 00:54:35,360 --> 00:54:37,640 Sulphur dioxide tends to stay in the atmosphere 625 00:54:37,640 --> 00:54:39,840 for a shorter period of time, 626 00:54:39,840 --> 00:54:41,760 because it can get rained out. 627 00:54:42,840 --> 00:54:46,040 But carbon dioxide can stay in the Earth's atmosphere for hundreds, 628 00:54:46,040 --> 00:54:47,520 if not thousands of years. 629 00:54:48,960 --> 00:54:52,920 Scientists think that heat-trapping carbon dioxide 630 00:54:52,920 --> 00:54:56,800 would have built up in the atmosphere, warming the planet. 631 00:54:59,440 --> 00:55:03,720 And there were other clues in the fossil record. 632 00:55:03,720 --> 00:55:06,480 So, we can measure what temperatures were like in the past 633 00:55:06,480 --> 00:55:08,200 by the study of fossils, 634 00:55:08,200 --> 00:55:10,520 and particularly fossil bone material. 635 00:55:10,520 --> 00:55:12,120 So, when the bone is formed, 636 00:55:12,120 --> 00:55:14,640 it's partly controlled by the temperature. 637 00:55:14,640 --> 00:55:17,120 And so by studying these bones, we're able to see 638 00:55:17,120 --> 00:55:19,600 what the temperatures were like back in the past. 639 00:55:23,400 --> 00:55:29,800 Temperature rises of up to 7 degrees brought a deluge of rainfall. 640 00:55:29,800 --> 00:55:33,120 Known as the Carnian Pluvial Episode, 641 00:55:33,120 --> 00:55:37,080 some scientists think these conditions were essential 642 00:55:37,080 --> 00:55:39,280 to the success of the dinosaurs. 643 00:55:40,600 --> 00:55:45,920 My research suggests that more rain means it's better for the plants. 644 00:55:45,920 --> 00:55:51,320 This era of warm, wet conditions really boosted plant diversity. 645 00:55:51,320 --> 00:55:54,600 More plants equals more insects, more plant-eaters, 646 00:55:54,600 --> 00:55:57,280 and then you get more meat-eaters as well, 647 00:55:57,280 --> 00:55:59,240 and dinosaurs are part of that growth. 648 00:56:01,640 --> 00:56:03,160 So, this is Herrerasaurus. 649 00:56:03,160 --> 00:56:05,760 This is one of the first dinosaurs to appear. 650 00:56:05,760 --> 00:56:08,480 And as you can see by the sharp teeth here, 651 00:56:08,480 --> 00:56:12,240 this was a meat-eater, one of the top predators. 652 00:56:12,240 --> 00:56:16,760 The evidence for this growth is written in the rock record. 653 00:56:16,760 --> 00:56:20,080 The success of the dinosaurs after this event is seen in 654 00:56:20,080 --> 00:56:23,800 just an abundance of their fossils, but also in their sort of indirect 655 00:56:23,800 --> 00:56:27,600 records that they leave in the forms of their footprints as well. 656 00:56:27,600 --> 00:56:29,880 Before the Carnian Pluvial Episode, 657 00:56:29,880 --> 00:56:32,920 dinosaurs and their relatives only made up around 5% of the footprints 658 00:56:32,920 --> 00:56:35,320 at these different fossil sites. 659 00:56:35,320 --> 00:56:38,800 After the Carnian Pluvial Episode, we see a big increase - 660 00:56:38,800 --> 00:56:40,600 it jumps up to 70%. 661 00:56:42,200 --> 00:56:45,480 The explosion in the population of dinosaurs 662 00:56:45,480 --> 00:56:48,920 is a brand-new area of research. 663 00:56:48,920 --> 00:56:51,920 We can see that the ecosystems were changing, 664 00:56:51,920 --> 00:56:54,080 but what actually would've affected the dinosaurs, 665 00:56:54,080 --> 00:56:56,480 what would've caused them to be successful, 666 00:56:56,480 --> 00:56:58,280 we don't know yet. 667 00:56:58,280 --> 00:57:00,280 This is why there's so many palaeontologists 668 00:57:00,280 --> 00:57:02,040 doing active research. 669 00:57:08,480 --> 00:57:09,800 Next time... 670 00:57:13,200 --> 00:57:16,960 ..we journey deeper into the past, 671 00:57:16,960 --> 00:57:20,760 to witness one of the strangest moments in history... 672 00:57:22,640 --> 00:57:25,560 ..a global deep freeze.. 673 00:57:27,200 --> 00:57:30,120 ..that transformed the Earth... 674 00:57:30,120 --> 00:57:32,000 ..into an ice world. 675 00:57:37,200 --> 00:57:40,120 If the Earth could talk, what would it tell us? 676 00:57:40,120 --> 00:57:42,680 Well, the Open University imagine how it might answer 677 00:57:42,680 --> 00:57:44,160 some of our questions. 678 00:57:44,160 --> 00:57:46,760 To experience this interactive presentation, 679 00:57:46,760 --> 00:57:49,320 go to the website on the screen and follow the links 680 00:57:49,320 --> 00:57:51,200 to The Open University.