1 00:01:00,727 --> 00:01:03,525 Today, We are in the midst of a scientific revolution 2 00:01:03,663 --> 00:01:05,563 in our understanding of the Earth 3 00:01:05,698 --> 00:01:08,030 and our relationship to it. 4 00:01:14,574 --> 00:01:16,565 Recently, scientists have begun to 5 00:01:16,709 --> 00:01:19,803 think of the Earth in a neW Way - 6 00:01:21,314 --> 00:01:24,408 almost as a living organism. 7 00:01:32,859 --> 00:01:36,955 Like a living thing it is forever on the move, 8 00:01:37,097 --> 00:01:38,621 driven by the restless energy 9 00:01:38,765 --> 00:01:41,290 locked up in its interior. 10 00:01:46,072 --> 00:01:48,006 And as the planet has evolved, 11 00:01:48,141 --> 00:01:50,109 so has life, 12 00:01:51,211 --> 00:01:52,576 shaped by the same forces 13 00:01:52,712 --> 00:01:57,945 that move continents and change climates. 14 00:02:00,086 --> 00:02:03,544 ln Earth Story We shall explore this neW vision 15 00:02:03,690 --> 00:02:06,056 of a living planet 16 00:02:06,192 --> 00:02:07,989 and the essence of this vision 17 00:02:08,128 --> 00:02:11,188 is an understanding of time. 18 00:02:30,950 --> 00:02:32,417 The most profound question 19 00:02:32,552 --> 00:02:34,452 any scientist can ask about the earth 20 00:02:34,587 --> 00:02:36,077 is also a simple one - 21 00:02:36,222 --> 00:02:38,622 hoW old is it? 22 00:02:41,194 --> 00:02:43,128 lt's a question geologists have been striving 23 00:02:43,263 --> 00:02:46,426 to ansWer for 200 years. 24 00:02:50,770 --> 00:02:51,998 At the turn of the century 25 00:02:52,138 --> 00:02:54,902 one such geologist came to a remote corner 26 00:02:55,041 --> 00:02:56,167 of Southern Africa 27 00:02:56,309 --> 00:02:59,335 called the Barberton Mountain Land. 28 00:03:00,113 --> 00:03:02,172 His name Was Alan Hall 29 00:03:02,315 --> 00:03:04,783 and he had a commission from the South African government 30 00:03:04,918 --> 00:03:08,979 to map this area looking for gold. 31 00:03:18,998 --> 00:03:20,124 The Barberton Mountain Land 32 00:03:20,266 --> 00:03:23,963 is several thousand square kilometres of rugged terrain, 33 00:03:24,103 --> 00:03:26,367 cut through by rivers. 34 00:03:34,113 --> 00:03:36,638 Rocky outcrops dot the hills, 35 00:03:36,783 --> 00:03:40,651 signs of the bedrock hidden beneath the landscape. 36 00:03:46,025 --> 00:03:48,459 Hall's aim Was to criss-cross the region, 37 00:03:48,595 --> 00:03:50,529 recording these outcrops, 38 00:03:50,663 --> 00:03:51,857 and so build up a picture 39 00:03:51,998 --> 00:03:54,432 of the rocks beloW the surface. 40 00:04:01,975 --> 00:04:04,205 lt Was an immense task. 41 00:04:06,546 --> 00:04:09,106 But as he Worked his Way across the landscape 42 00:04:09,249 --> 00:04:13,515 Hall sloWly realized that something Was missing. 43 00:04:17,090 --> 00:04:18,819 HoWever hard he looked, 44 00:04:18,958 --> 00:04:20,425 he could find in the rocks 45 00:04:20,560 --> 00:04:24,121 none of the usual signs of fossilized life. 46 00:04:30,403 --> 00:04:32,496 Could Barberton be a fragment of the Earth 47 00:04:32,639 --> 00:04:36,040 from a time before life began? 48 00:04:40,146 --> 00:04:43,172 Just hoW old Was this place? 49 00:04:48,254 --> 00:04:51,849 Hall's question came at a critical moment. 50 00:04:53,526 --> 00:04:55,756 For a hundred years scientists had been arguing 51 00:04:55,895 --> 00:04:58,489 about the age of the Earth 52 00:05:01,634 --> 00:05:03,625 They Were struggling to overcome ideas 53 00:05:03,770 --> 00:05:06,432 Which had held sWay for centuries. 54 00:05:06,572 --> 00:05:08,540 ldeas sanctioned by the full authority 55 00:05:08,675 --> 00:05:11,143 of religious doctrine. 56 00:05:27,126 --> 00:05:30,220 The book of Genesis relates hoW God created the earth 57 00:05:30,363 --> 00:05:32,627 and everything in it, including ourselves, 58 00:05:32,765 --> 00:05:35,928 in just 6 days. 59 00:05:42,408 --> 00:05:46,174 The implication Was that earth history and human history 60 00:05:46,312 --> 00:05:48,780 had begun at the same moment 61 00:05:48,915 --> 00:05:51,179 and this provided 1 7th century scholars 62 00:05:51,317 --> 00:05:54,912 With a Way to determine the age of the earth. 63 00:05:56,222 --> 00:05:58,019 By simply adding up the ages 64 00:05:58,157 --> 00:06:00,853 of Adam's descendants as listed in the Bible, 65 00:06:00,993 --> 00:06:02,221 they concluded that the planet 66 00:06:02,362 --> 00:06:06,389 must have been created in 4004 BC, 67 00:06:06,532 --> 00:06:10,434 Which meant it Was less than 6,000 years old. 68 00:06:15,041 --> 00:06:18,238 But it didn't look that Way to geologists. 69 00:06:19,445 --> 00:06:21,310 When they studied places like Barberton 70 00:06:21,447 --> 00:06:23,074 they saW evidence that the landscape 71 00:06:23,216 --> 00:06:24,649 had changed over time - 72 00:06:24,784 --> 00:06:27,582 that it had a long history. 73 00:06:29,122 --> 00:06:32,990 Hall's modern-day successor is Maarten de Wit. 74 00:06:33,659 --> 00:06:34,853 He too is fascinated 75 00:06:34,994 --> 00:06:38,054 by the question of Barberton's antiquity. 76 00:06:39,232 --> 00:06:40,995 l really got interested in this part 77 00:06:41,134 --> 00:06:42,601 of the World many years ago, 78 00:06:42,735 --> 00:06:44,726 but the opportunity to come here didn't arise 79 00:06:44,871 --> 00:06:46,202 until much later. 80 00:06:46,339 --> 00:06:47,465 At the end of the 70s 81 00:06:47,607 --> 00:06:49,370 l came doWn here to Barberton 82 00:06:49,509 --> 00:06:52,171 and it turned out to be one of the best moves of my life. 83 00:06:52,311 --> 00:06:53,369 lt's one of these areas 84 00:06:53,513 --> 00:06:56,607 that has something extremely special 85 00:06:56,749 --> 00:06:59,115 to tell about the story of the earth. 86 00:07:01,154 --> 00:07:03,054 Maarten, like Hall before him, 87 00:07:03,189 --> 00:07:06,625 has mapped the rocks of Barberton in detail. 88 00:07:07,126 --> 00:07:08,058 When you do this, 89 00:07:08,194 --> 00:07:11,493 a striking pattern quickly emerges. 90 00:07:15,368 --> 00:07:17,893 Well once you start mapping the hills here, 91 00:07:18,037 --> 00:07:19,629 you'll notice that the landscape 92 00:07:19,772 --> 00:07:21,364 is dominated by stripes - 93 00:07:21,507 --> 00:07:22,667 stripes of rocks - 94 00:07:22,809 --> 00:07:25,642 like that one there. 95 00:07:25,778 --> 00:07:27,177 And if you get your eye in, 96 00:07:27,313 --> 00:07:30,282 after a While you'll see, in fact, all these rock layers, 97 00:07:30,416 --> 00:07:31,576 all are visible. 98 00:07:31,717 --> 00:07:33,514 ln this case this huge mass here 99 00:07:33,653 --> 00:07:37,589 has finer vertical rock layers. 100 00:07:42,195 --> 00:07:43,423 Everywhere in Barberton 101 00:07:43,563 --> 00:07:46,862 the landscape seems to be made of layers. 102 00:07:52,171 --> 00:07:53,695 By the nineteenth century, 103 00:07:53,840 --> 00:07:55,273 geologists had begun to realize 104 00:07:55,408 --> 00:07:57,899 that the process that created these layers 105 00:07:58,044 --> 00:08:00,569 Was still at Work all around them. 106 00:08:32,378 --> 00:08:35,142 Hall and his contemporaries kneW that Water 107 00:08:35,281 --> 00:08:37,681 can be a poWerful agent of change, 108 00:08:37,817 --> 00:08:43,187 eroding rock, but also creating it... over time. 109 00:08:48,728 --> 00:08:50,218 Well take this river, for example, 110 00:08:50,363 --> 00:08:51,762 like many rivers, 111 00:08:51,898 --> 00:08:53,525 cutting through the rocks, 112 00:08:53,666 --> 00:08:55,634 moving material doWnstream - 113 00:08:55,768 --> 00:08:57,201 sand and silt - 114 00:08:57,336 --> 00:08:58,394 and as it moves doWn 115 00:08:58,538 --> 00:09:00,369 that material Will deposit someWhere 116 00:09:00,506 --> 00:09:03,134 in a quiet spot layer upon layer, 117 00:09:03,276 --> 00:09:05,972 and as these layers get deposited on top of one another 118 00:09:06,112 --> 00:09:08,672 they turn into rock sloWly. 119 00:09:15,922 --> 00:09:18,288 Well here you have a slab of rock. 120 00:09:18,424 --> 00:09:21,052 NoW this slab represents a river bed. 121 00:09:21,193 --> 00:09:23,627 There you can even see the sand grains. 122 00:09:23,763 --> 00:09:26,061 These Would have been the sand grains in the river. 123 00:09:26,198 --> 00:09:28,291 These ridges that you see here, 124 00:09:28,434 --> 00:09:29,799 they are ripples. 125 00:09:29,936 --> 00:09:31,096 l can tell that it Would have floWed 126 00:09:31,237 --> 00:09:34,604 from my hand here doWnWards in that direction. 127 00:09:35,508 --> 00:09:37,305 NoW you can see if you look doWnWards 128 00:09:37,443 --> 00:09:39,570 that in fact there are several of these 129 00:09:39,712 --> 00:09:42,442 slabs stacked on top of one another. 130 00:09:43,182 --> 00:09:44,274 Here's one, 131 00:09:44,417 --> 00:09:46,851 there you see another one over here, 132 00:09:46,986 --> 00:09:48,544 and another one, 133 00:09:48,688 --> 00:09:51,589 and another one still, and more. 134 00:09:51,724 --> 00:09:54,090 These are dozens of slabs 135 00:09:54,226 --> 00:09:55,989 and they're all tilted right noW, 136 00:09:56,128 --> 00:09:58,562 but originally they Would have been horizontal 137 00:09:58,698 --> 00:10:00,893 and they represent all history of rivers. 138 00:10:01,033 --> 00:10:03,593 A long history of deposition. 139 00:10:07,173 --> 00:10:08,800 To nineteenth-century scientists 140 00:10:08,941 --> 00:10:10,636 a World made up of layers 141 00:10:10,776 --> 00:10:12,403 didn't look as if it had been created 142 00:10:12,545 --> 00:10:15,343 all in one go as the Bible says. 143 00:10:16,148 --> 00:10:19,311 lt must have been built up overtime. 144 00:10:20,286 --> 00:10:22,277 But hoW much time? 145 00:10:27,026 --> 00:10:28,357 The first person to realise 146 00:10:28,494 --> 00:10:30,928 the profound importance of this question 147 00:10:31,063 --> 00:10:34,590 Was a Scotsman, James Mutton. 148 00:10:38,304 --> 00:10:41,205 At Siccar Point on the east coast of Scotland 149 00:10:41,340 --> 00:10:43,069 exposed in the cliff side 150 00:10:43,209 --> 00:10:44,836 there's a small patch of rock 151 00:10:44,977 --> 00:10:48,344 Which made a deep impression on Hunt. 152 00:10:52,852 --> 00:10:54,979 Chris Nicholas is a geologist 153 00:10:55,121 --> 00:10:58,318 Who has made a special study of his Work. 154 00:11:05,865 --> 00:11:07,856 So here We are at one of the most 155 00:11:08,000 --> 00:11:09,865 famous geological localities in the World. 156 00:11:10,002 --> 00:11:11,993 This is Hutton's Uncomformity 157 00:11:12,138 --> 00:11:14,299 and What Hutton noticed here 158 00:11:14,440 --> 00:11:15,407 in this cliff 159 00:11:15,541 --> 00:11:18,339 is that at the bottom of the cliff you have these 160 00:11:18,477 --> 00:11:20,741 vertical strata, 161 00:11:20,880 --> 00:11:23,872 overlain by horizontal strata 162 00:11:24,016 --> 00:11:25,415 and betWeen the tWo 163 00:11:25,551 --> 00:11:27,951 there Was an undulating erosional surface. 164 00:11:28,087 --> 00:11:30,180 And What Hutton recognised 165 00:11:30,322 --> 00:11:32,654 Was that Well if all rocks 166 00:11:32,792 --> 00:11:34,623 Were deposited horizontally on the sea-bed, 167 00:11:34,760 --> 00:11:37,194 What on earth Was this grey rock doing being vertical 168 00:11:37,329 --> 00:11:39,593 at the base of the cliff there Was something Wrong here. 169 00:11:39,732 --> 00:11:41,165 And he started to look at rocks in more detail 170 00:11:41,300 --> 00:11:43,029 and he came up With this idea 171 00:11:43,169 --> 00:11:44,796 that What must have happened 172 00:11:44,937 --> 00:11:48,668 is that the grey rock must have been tWisted and turned 173 00:11:48,808 --> 00:11:50,298 so that it Was vertical, 174 00:11:50,443 --> 00:11:52,377 uplifted out of the sea, 175 00:11:52,511 --> 00:11:56,470 eroded off and then droWned again, 176 00:11:56,615 --> 00:12:00,073 so that the red rock could be deposited on top. 177 00:12:01,187 --> 00:12:03,917 And more than that, it Was then uplifted again 178 00:12:04,056 --> 00:12:06,456 to form the cliff We noW see. 179 00:12:06,592 --> 00:12:12,326 So there Were at least 2 cycles of deposition, 180 00:12:12,465 --> 00:12:14,262 uplift and then erosion 181 00:12:14,400 --> 00:12:16,368 that he could see in this cliff. 182 00:12:16,502 --> 00:12:19,869 And he Went on to say ''Well, these cycles must have taken 183 00:12:20,005 --> 00:12:22,235 an immense amount of time to complete'' 184 00:12:22,374 --> 00:12:25,172 because When he looked around him and saW rivers 185 00:12:25,311 --> 00:12:27,074 and the sea eroding today 186 00:12:27,213 --> 00:12:30,182 it doesn't really erode very quickly. 187 00:12:33,285 --> 00:12:35,219 And also he said ''Well hoW many cycles 188 00:12:35,354 --> 00:12:36,582 could have taken place before these 189 00:12:36,722 --> 00:12:38,622 and hoW many Will come after this, 190 00:12:38,758 --> 00:12:40,055 We just don't knoW''. 191 00:12:40,192 --> 00:12:42,160 And it led him on to this idea 192 00:12:42,294 --> 00:12:44,524 of the immensity 193 00:12:44,663 --> 00:12:46,426 of geological time 194 00:12:46,565 --> 00:12:49,557 and he came out With a very famous quote of, 195 00:12:49,702 --> 00:12:51,397 Well, he could see no vestige 196 00:12:51,537 --> 00:12:54,700 of a beginning and no prospect of an end. 197 00:12:56,475 --> 00:13:00,309 For Hutton the earth Was infinitely old. 198 00:13:10,556 --> 00:13:14,583 Siccar Point represents the discovery of geological time 199 00:13:14,727 --> 00:13:16,786 and it's shaped the Way 200 00:13:16,929 --> 00:13:20,888 that geologists think and Work ever since. 201 00:13:21,033 --> 00:13:21,965 One of Hutton's colleagues, 202 00:13:22,101 --> 00:13:23,659 John Plafare, Who Was a mathematician 203 00:13:23,803 --> 00:13:25,634 came to Siccar Point With Hutton 204 00:13:25,771 --> 00:13:27,864 and Plafare Wrote afterwards 205 00:13:28,007 --> 00:13:28,974 of his experience here 206 00:13:29,108 --> 00:13:30,234 and he said that 207 00:13:30,376 --> 00:13:31,866 ''For those of us Who 208 00:13:32,011 --> 00:13:34,479 saW the rocks at Siccar Point 209 00:13:34,613 --> 00:13:36,444 their impact Was not lost on us 210 00:13:36,582 --> 00:13:39,278 and We greW giddy 211 00:13:39,418 --> 00:13:42,581 looking so far into the abyss of time''. 212 00:13:48,294 --> 00:13:49,591 But geologists kneW 213 00:13:49,728 --> 00:13:53,425 Hutton's abyss Was not empty. 214 00:13:56,135 --> 00:13:57,124 Beneath their feet 215 00:13:57,269 --> 00:14:00,568 lay clues to the entire history of the planet 216 00:14:00,706 --> 00:14:02,936 locked up in the rock layers. 217 00:14:03,075 --> 00:14:05,509 Yeah, We're going doWn to 128 level, 218 00:14:05,644 --> 00:14:08,704 someWhere betWeen 8 and 10 metres per second. 219 00:14:08,848 --> 00:14:10,315 l mean, it's nothing to be scared about? 220 00:14:10,449 --> 00:14:12,781 No, it's like the Empire State 221 00:14:12,918 --> 00:14:14,886 Building's elevator system. 222 00:14:15,020 --> 00:14:16,146 Yeah. 223 00:14:16,288 --> 00:14:19,314 Not as smooth and probably a bit quicker. 224 00:14:20,359 --> 00:14:23,920 200 miles West of Barberton lie the Rand goldfields, 225 00:14:24,063 --> 00:14:27,396 Where they sink the World's deepest mine shafts. 226 00:14:27,533 --> 00:14:28,522 For Maarten de Wit, 227 00:14:28,667 --> 00:14:33,127 it's an opportunity to travel back in time. 228 00:14:46,619 --> 00:14:48,018 OK, noW you should be able to 229 00:14:48,153 --> 00:14:50,815 get the impression of 230 00:14:51,824 --> 00:14:54,156 at a fairly rapid rate 231 00:14:54,293 --> 00:14:55,487 and you'll also feel your ears 232 00:14:55,628 --> 00:14:58,153 go from the pressure. 233 00:15:00,366 --> 00:15:02,391 can feel it noW. 234 00:15:08,774 --> 00:15:10,765 That's the other cage going on the Way up. 235 00:15:10,910 --> 00:15:12,810 On the couple drum system 236 00:15:12,945 --> 00:15:14,640 if the hoist driver gets it all Wrong 237 00:15:14,780 --> 00:15:17,749 and he snaps the brakes on too suddenly, 238 00:15:17,883 --> 00:15:19,441 you can feel the stretch noW. 239 00:15:19,585 --> 00:15:20,051 Unbelievable. 240 00:15:20,185 --> 00:15:22,517 He got his braking a bit Wrong. Scary. 241 00:15:22,655 --> 00:15:25,488 Oh you get used to it. 242 00:15:26,091 --> 00:15:30,221 So We're travelling through 6,000 metres of sediment 243 00:15:30,362 --> 00:15:31,761 backWards in time? 244 00:15:31,897 --> 00:15:33,558 We are noW in a part of the World 245 00:15:33,699 --> 00:15:36,725 Where We are old enough to be pre-life. 246 00:15:38,103 --> 00:15:41,630 No Wriggling organisms Were present at this point. 247 00:15:46,412 --> 00:15:49,074 No matter hoW far back in time you go, 248 00:15:49,214 --> 00:15:51,512 every rock contains a detailed picture 249 00:15:51,650 --> 00:15:54,244 of the environment it formed in - 250 00:15:54,853 --> 00:15:57,720 if you knoW hoW to look at it. 251 00:15:59,825 --> 00:16:00,985 OK, What We have here noW 252 00:16:01,126 --> 00:16:03,253 is a collection of gravel layers 253 00:16:03,395 --> 00:16:06,523 and What We are mining from top to bottom 254 00:16:06,665 --> 00:16:08,530 is the selected reef cut 255 00:16:08,667 --> 00:16:11,101 and associated With the pebbles 256 00:16:11,236 --> 00:16:13,261 and the pyrite that you see here, 257 00:16:13,405 --> 00:16:15,839 obviously there are concentrations of gold, 258 00:16:15,975 --> 00:16:17,636 Which is the source of our business. 259 00:16:17,776 --> 00:16:19,038 Well it looks to me 260 00:16:19,178 --> 00:16:20,509 like We're looking at a section here 261 00:16:20,646 --> 00:16:23,615 that's sliced through a series of river beds. 262 00:16:23,749 --> 00:16:25,376 l mean, We can clearly see the pebbles, 263 00:16:25,517 --> 00:16:26,950 you can see them rounded 264 00:16:27,086 --> 00:16:28,553 and of course We can see 265 00:16:28,687 --> 00:16:30,086 the heavy mineral concentration 266 00:16:30,222 --> 00:16:31,450 at the bottom of the bed. 267 00:16:31,590 --> 00:16:32,522 lt looks like We're looking at 268 00:16:32,658 --> 00:16:34,023 a stack of river bed. What do you think? 269 00:16:34,159 --> 00:16:36,525 That these have been meandering rivers of some sort? 270 00:16:36,662 --> 00:16:37,651 Yeah, exactly that. 271 00:16:37,796 --> 00:16:39,593 What one could actually describe 272 00:16:39,732 --> 00:16:43,327 is a series of gravel bars 273 00:16:43,469 --> 00:16:45,334 in their depositional mode 274 00:16:45,471 --> 00:16:47,166 Which have inter-fingered With each other. 275 00:16:47,306 --> 00:16:48,568 So some sort of meandering river 276 00:16:48,707 --> 00:16:49,867 over a flat plane. 277 00:16:50,009 --> 00:16:52,637 And We're sitting here a kilometre doWn noW 278 00:16:52,778 --> 00:16:54,439 for these beds have been buried 279 00:16:54,580 --> 00:16:55,842 by later rivers 280 00:16:55,981 --> 00:16:57,642 and more rivers and We knoW 281 00:16:57,783 --> 00:16:58,715 We can go doWnn in places 282 00:16:58,851 --> 00:17:01,445 even another 4, 5 kilometres, 283 00:17:01,587 --> 00:17:04,181 so We knoW that this is a huge stack 284 00:17:04,323 --> 00:17:05,915 of just river bed after river bed 285 00:17:06,058 --> 00:17:07,787 after river bed after river bed. 286 00:17:07,926 --> 00:17:09,757 And as you can see all this shiny stuff, 287 00:17:09,895 --> 00:17:11,692 iodine sulphite, pyrite, 288 00:17:11,830 --> 00:17:12,922 Which should have oxidised - 289 00:17:13,065 --> 00:17:14,396 it should have rusted by noW - 290 00:17:14,533 --> 00:17:15,522 but it's still shining. 291 00:17:15,667 --> 00:17:16,861 So the pyrite are telling us that 292 00:17:17,002 --> 00:17:18,469 We must have had much less oxygen 293 00:17:18,604 --> 00:17:19,628 in the atmosphere at the time. 294 00:17:19,772 --> 00:17:21,672 That's correct. lt probably Was the atmosphere 295 00:17:21,807 --> 00:17:24,640 Which Was dominated by carbon dioxide. 296 00:17:27,780 --> 00:17:28,804 As nineteenth-century 297 00:17:28,947 --> 00:17:32,314 geologists explored the bedrock in different parts of the World, 298 00:17:32,451 --> 00:17:34,316 they sloWly built up a collection 299 00:17:34,453 --> 00:17:36,819 of random snapshots of the past, 300 00:17:36,955 --> 00:17:40,447 isolated fragments of the planet's history. 301 00:17:40,592 --> 00:17:42,457 But hoW could these fragments be linked together 302 00:17:42,594 --> 00:17:45,620 to form a complete story of the Earth? 303 00:17:53,338 --> 00:17:55,806 Here at the Regency resort of Lyme Regis 304 00:17:55,941 --> 00:17:58,068 on Britain's south coast, 305 00:17:58,210 --> 00:17:59,575 19th century scientists 306 00:17:59,711 --> 00:18:02,111 found the key to this puzzle. 307 00:18:07,886 --> 00:18:10,252 Every year oceanographer, Rachel Mills, 308 00:18:10,389 --> 00:18:12,914 brings her students here to see a place 309 00:18:13,058 --> 00:18:17,119 Where the past is vividly etched into the rock layers. 310 00:18:21,733 --> 00:18:24,031 These rocks hold a different sort of clue 311 00:18:24,169 --> 00:18:26,160 to the earth's history. 312 00:18:32,010 --> 00:18:33,705 The beach is a great place to come and do geology 313 00:18:33,846 --> 00:18:34,870 because here We have the sea 314 00:18:35,013 --> 00:18:36,002 eating aWay continuously 315 00:18:36,148 --> 00:18:38,207 at the cliffs exposing the rocks 316 00:18:38,350 --> 00:18:40,375 that normally are under our feet in dorset, 317 00:18:40,519 --> 00:18:42,043 but here We can Walk along the beach 318 00:18:42,187 --> 00:18:43,950 and actually see the rocks that Were laid doWn 319 00:18:44,089 --> 00:18:46,148 millions of years ago. 320 00:18:46,291 --> 00:18:48,259 The striking thing about these rocks is that 321 00:18:48,393 --> 00:18:50,554 here We have a cliff Which seems to have this alternating 322 00:18:50,696 --> 00:18:52,163 light/dark, light/dark, light/dark, 323 00:18:52,297 --> 00:18:54,959 Which is repeating in a sort of regular basis 324 00:18:55,100 --> 00:18:57,500 as We move up through geological time, 325 00:18:57,636 --> 00:18:59,069 up this cliff. 326 00:18:59,204 --> 00:19:01,934 NoW if We look at these rocks in a bit more details 327 00:19:02,074 --> 00:19:05,043 We can see there's a lot of interesting information 328 00:19:05,177 --> 00:19:07,907 in here Which We can pull out as geologists 329 00:19:08,046 --> 00:19:11,641 to tell us about the conditions under Which they formed. 330 00:19:11,783 --> 00:19:12,977 NoW the dark, soft layers, 331 00:19:13,118 --> 00:19:15,279 have been laid doWn in an ocean environment, 332 00:19:15,420 --> 00:19:16,785 a shalloW sea. 333 00:19:16,922 --> 00:19:18,617 l can break this With my fingers, 334 00:19:18,757 --> 00:19:20,156 so you can see it falls apart very easily 335 00:19:20,292 --> 00:19:22,726 and that's Why it erodes very easily here on the beach. 336 00:19:22,861 --> 00:19:25,352 And essentially it's made from clay particles 337 00:19:25,497 --> 00:19:27,863 that have been transported by rivers to the ocean 338 00:19:28,000 --> 00:19:31,265 and then very little has happened to it since then. 339 00:19:31,403 --> 00:19:32,893 The light layer is strikingly different. 340 00:19:33,038 --> 00:19:34,596 lt's much, much harder 341 00:19:34,740 --> 00:19:36,298 and that's Why it stands out 342 00:19:36,441 --> 00:19:38,534 in these platforms across the beach. 343 00:19:38,677 --> 00:19:40,372 Basically this rock is limestone 344 00:19:40,512 --> 00:19:42,912 and it is formed by the shelly remains of organisms 345 00:19:43,048 --> 00:19:44,845 that lived in the ocean at that time, 346 00:19:44,983 --> 00:19:47,315 but later on it has been cemented, 347 00:19:47,452 --> 00:19:49,511 Which makes it hard. 348 00:19:49,655 --> 00:19:51,646 But What's most exciting about these rocks 349 00:19:51,790 --> 00:19:54,224 is What We find in them. 350 00:19:54,927 --> 00:19:57,157 And so this layer Which l'm Walking across at the moment 351 00:19:57,296 --> 00:19:59,161 is one of these limestone pavements 352 00:19:59,298 --> 00:20:03,496 Which is full of hundreds and thousands of fossils. 353 00:20:03,635 --> 00:20:05,262 And this is a really nice example here 354 00:20:05,404 --> 00:20:07,304 of a fossil ammonite. 355 00:20:07,439 --> 00:20:09,031 And this organism lived in the ocean 356 00:20:09,174 --> 00:20:10,471 millions of years ago. 357 00:20:10,609 --> 00:20:12,372 lt died, sank to the sea floor, 358 00:20:12,511 --> 00:20:15,412 and then has been preserved for geological time. 359 00:20:18,150 --> 00:20:21,244 lronically, the first people to take a real interest 360 00:20:21,386 --> 00:20:23,047 in these strange shapes in the rocks 361 00:20:23,188 --> 00:20:26,214 Were not scientists but fossil-hunters 362 00:20:26,358 --> 00:20:30,590 Who made a living selling these beautiful objects to tourists. 363 00:20:46,011 --> 00:20:47,569 Fossil hunters at Lyme Regis 364 00:20:47,713 --> 00:20:49,544 soon acquired an intimate knoWledge 365 00:20:49,681 --> 00:20:52,775 of the different ammonites they found along the beach. 366 00:20:54,920 --> 00:20:56,888 There Were over 1 ,000 different species 367 00:20:57,022 --> 00:20:59,547 in this locality alone. 368 00:21:03,629 --> 00:21:07,121 Significantly these fossils increased in size, 369 00:21:07,266 --> 00:21:09,291 complexity and diversity 370 00:21:09,434 --> 00:21:11,959 as you moved higher up the cliff. 371 00:21:12,104 --> 00:21:15,870 ln other Words they seemed to evolve through time 372 00:21:25,484 --> 00:21:27,111 NoW each layer of limestone 373 00:21:27,252 --> 00:21:29,777 has a characteristic assemblage of fossils in it 374 00:21:29,921 --> 00:21:30,979 Which alloWs geologists 375 00:21:31,123 --> 00:21:32,613 to go anywhere else in the World 376 00:21:32,758 --> 00:21:34,726 and if they find the same assemblage of fossils 377 00:21:34,860 --> 00:21:35,588 they then can say 378 00:21:35,727 --> 00:21:38,059 ''That rock Was laid doWn at exactly the same 379 00:21:38,196 --> 00:21:40,562 as these rocks here in Lyme Regis''. 380 00:21:40,699 --> 00:21:42,860 This Was a great leap forward for geologists 381 00:21:43,001 --> 00:21:44,025 in the 19th century 382 00:21:44,169 --> 00:21:47,297 because it alloWed them to divide up geological time 383 00:21:47,439 --> 00:21:50,067 into the familiar time-scales that We noW use - 384 00:21:50,208 --> 00:21:53,405 the Triassic, the Jurassic, the Cretaceous - 385 00:21:53,545 --> 00:21:56,912 and so With this understanding of hoW fossils evolve 386 00:21:57,049 --> 00:21:58,482 and change through time 387 00:21:58,617 --> 00:22:01,609 We can put together a timescale. 388 00:22:02,988 --> 00:22:04,319 By classifying rock layers 389 00:22:04,456 --> 00:22:06,424 according to their fossil content, 390 00:22:06,558 --> 00:22:08,526 scientists Were able to tell hoW layers 391 00:22:08,660 --> 00:22:10,093 in one part of the World 392 00:22:10,228 --> 00:22:12,719 related to layers found elseWhere, 393 00:22:12,864 --> 00:22:15,424 Whether they Were younger or older. 394 00:22:15,567 --> 00:22:17,398 But What they still couldn't say 395 00:22:17,536 --> 00:22:20,369 Was hoW old they Were. 396 00:22:25,177 --> 00:22:26,508 The problem of putting a figure 397 00:22:26,645 --> 00:22:28,078 to the age of the Earth 398 00:22:28,213 --> 00:22:31,979 soon became the most pressing question in science - 399 00:22:32,117 --> 00:22:33,277 and it attracted one of 400 00:22:33,418 --> 00:22:36,182 the century's most brilliant physicists- 401 00:22:36,321 --> 00:22:38,255 Lord Kelvin. 402 00:22:39,925 --> 00:22:41,415 Kelvin believed that he had hit 403 00:22:41,560 --> 00:22:43,892 on a Way of calculating the Earth's age 404 00:22:44,029 --> 00:22:45,929 With some rigour. 405 00:22:47,232 --> 00:22:49,393 His method Was based on the eperience 406 00:22:49,534 --> 00:22:52,526 of Victorian coal miners. 407 00:22:53,438 --> 00:22:54,962 HoWever deep they go, 408 00:22:55,107 --> 00:22:57,302 all miners face a common hazard. 409 00:22:57,442 --> 00:23:00,172 WoW, it's hot doWn here. Hey! HoW hot is it here? 410 00:23:00,312 --> 00:23:02,803 Well l think it's about 27 degrees. 411 00:23:02,948 --> 00:23:04,279 Anywhere in the World you are, 412 00:23:04,416 --> 00:23:06,611 the deeper you go, the hotter it gets. 413 00:23:06,752 --> 00:23:07,810 What kind of temperature increase 414 00:23:07,953 --> 00:23:10,251 do We see here as We go doWn? 415 00:23:10,389 --> 00:23:14,052 We have something like 1 1 degrees per kilometre. 416 00:23:14,192 --> 00:23:17,389 As nineteenth-century miners had already discovered 417 00:23:17,529 --> 00:23:20,828 the interior of the Earth is hot. 418 00:23:22,434 --> 00:23:25,130 Where Was this heat coming from? 419 00:23:25,270 --> 00:23:29,001 Kelvin believed that it Was a relic of the planet's birth - 420 00:23:29,141 --> 00:23:32,975 heat trapped inside the Earth since its formation. 421 00:23:38,150 --> 00:23:40,448 Kelvin deduced that the Earth must have been formed 422 00:23:40,585 --> 00:23:43,713 by the steady accumulation of smaller rocks. 423 00:23:43,855 --> 00:23:44,879 The force of their impact 424 00:23:45,023 --> 00:23:47,014 as they Were pulled into the groWing planet 425 00:23:47,159 --> 00:23:49,457 released an immense amount of energy - 426 00:23:49,594 --> 00:23:52,722 enough to keep the entire globe molten. 427 00:23:59,971 --> 00:24:02,269 But Kelvin kneW that any hot body, 428 00:24:02,407 --> 00:24:04,500 unless it's being continuously heated, 429 00:24:04,643 --> 00:24:07,134 Will cool overtime. 430 00:24:07,279 --> 00:24:08,644 The longer the earth had been cooling, 431 00:24:08,780 --> 00:24:11,112 the colder it Would be. 432 00:24:14,219 --> 00:24:15,982 So he set about collecting information 433 00:24:16,121 --> 00:24:19,852 about hoW temperature increases as you go doWn mine shafts, 434 00:24:19,991 --> 00:24:22,221 hoW heat Was transmitted through rocks 435 00:24:22,360 --> 00:24:25,454 and What temperature rocks melt at. 436 00:24:25,597 --> 00:24:28,430 He applied all this to estimating hoW long it Was 437 00:24:28,567 --> 00:24:31,468 since the earth had last been molten. 438 00:24:33,605 --> 00:24:35,698 After many years of calculation 439 00:24:35,841 --> 00:24:38,674 Kelvin finally concluded that the earth 440 00:24:38,810 --> 00:24:43,270 couldn't be much more than 20 million years old. 441 00:24:49,254 --> 00:24:53,247 For most scientists Kelvin's argument appeared Watertight. 442 00:24:53,391 --> 00:24:55,757 But to field geologists like Hall, 443 00:24:55,894 --> 00:24:58,454 his number felt far too small. 444 00:24:58,597 --> 00:25:01,532 All around them Was layer upon layer of rock - 445 00:25:01,666 --> 00:25:04,157 even 20 million years seemed too short a time 446 00:25:04,302 --> 00:25:06,327 to lay them doWn. 447 00:25:08,340 --> 00:25:11,571 Then, just as Hall prepared to leave Barberton, 448 00:25:11,710 --> 00:25:13,075 his commission complete, 449 00:25:13,211 --> 00:25:15,338 back in London a stunning announcement 450 00:25:15,480 --> 00:25:18,210 began a revolution in geology . . . 451 00:25:18,350 --> 00:25:20,580 and resolved the paradox. 452 00:25:23,555 --> 00:25:25,216 ln 1904 453 00:25:25,357 --> 00:25:26,756 Britain's scientific elite 454 00:25:26,892 --> 00:25:29,759 Were gathering at the Royal lnstitution. 455 00:25:31,596 --> 00:25:34,793 A young NeW Zealand physicist, Ernest Rutherford, 456 00:25:34,933 --> 00:25:37,265 Was to reveal to the World What he had discovered 457 00:25:37,402 --> 00:25:41,771 about the neW phenomenon of radioactivity. 458 00:25:44,576 --> 00:25:46,476 The human understanding of the Earth, 459 00:25:46,611 --> 00:25:48,135 and of time itself, 460 00:25:48,280 --> 00:25:50,976 Was about to change forever. 461 00:25:53,552 --> 00:25:56,715 Tonight, the eminent scientist addressing the members 462 00:25:56,855 --> 00:25:59,449 is Professor Dan McKenzie. 463 00:26:00,325 --> 00:26:02,793 Professor McKenzie, We're ready. 464 00:26:13,238 --> 00:26:16,173 Obviously one of the central issues 465 00:26:16,308 --> 00:26:18,173 for the Earth is hoW old it is 466 00:26:18,310 --> 00:26:20,574 and one of the first physicists to try 467 00:26:20,712 --> 00:26:22,680 and make a decent estimate of the age 468 00:26:22,814 --> 00:26:25,214 of the Earth Was Lord Kelvin. 469 00:26:25,350 --> 00:26:27,511 And he came out With a number 470 00:26:27,652 --> 00:26:30,246 Which Was 20 million years. 471 00:26:31,022 --> 00:26:33,422 Earlier this century Rutherford came here 472 00:26:33,558 --> 00:26:35,822 to give a talk about radioactivity 473 00:26:35,961 --> 00:26:38,896 and someWhat to his consternation 474 00:26:39,030 --> 00:26:41,362 Kelvin Was in the audience. 475 00:26:41,499 --> 00:26:43,967 And he says jn hjs memoirs, 476 00:26:44,102 --> 00:26:45,899 ''l came into the room 477 00:26:46,037 --> 00:26:47,698 Which Was half dark 478 00:26:47,839 --> 00:26:50,364 and presently spotted Lord Kelvin in the audience 479 00:26:50,508 --> 00:26:52,806 and realised that l Was in for trouble 480 00:26:52,944 --> 00:26:54,775 at the last part of the speech dealing 481 00:26:54,913 --> 00:26:56,380 With the age of the Earth 482 00:26:56,514 --> 00:26:59,483 Where my vieWs conflicted With his. 483 00:26:59,618 --> 00:27:03,486 To my relief Kelvin fell fast asleep. 484 00:27:06,558 --> 00:27:10,085 Rutherford realised that various elements 485 00:27:10,228 --> 00:27:12,128 inside the Earth Were radioactive, 486 00:27:12,263 --> 00:27:14,527 like uranium and thorium and potassium 487 00:27:14,666 --> 00:27:16,429 and that these generated 488 00:27:16,568 --> 00:27:18,365 an important amount of heat 489 00:27:18,503 --> 00:27:20,869 and that this completely changed the basis 490 00:27:21,006 --> 00:27:22,439 of Kelvin's calculation 491 00:27:22,574 --> 00:27:24,542 because instead of the Earth cooling all the time 492 00:27:24,676 --> 00:27:26,439 it actually had heat sources in it. 493 00:27:26,578 --> 00:27:28,808 And that you couldn't any longer use 494 00:27:28,947 --> 00:27:32,508 that argument to estimate the age of the Earth. 495 00:27:32,651 --> 00:27:33,583 Rutherford had removed 496 00:27:33,718 --> 00:27:36,653 a central plank of Kelvin's argument. 497 00:27:36,788 --> 00:27:38,346 Not all the heat inside the Earth 498 00:27:38,490 --> 00:27:40,424 Was left over from its formation. 499 00:27:40,558 --> 00:27:42,685 lnstead, heat Was continuously being 500 00:27:42,827 --> 00:27:44,317 generated Within the planet 501 00:27:44,462 --> 00:27:46,930 by radioactive decay. 502 00:27:47,065 --> 00:27:48,657 But, on the other hand, 503 00:27:48,800 --> 00:27:50,631 What this then alloWed you to do 504 00:27:50,769 --> 00:27:53,237 Was to use the decay of these things, 505 00:27:53,371 --> 00:27:55,601 right, to not make an estimate 506 00:27:55,740 --> 00:27:59,301 but actually measure the age of the earth. 507 00:27:59,444 --> 00:28:01,002 Rutherford had laid the foundations 508 00:28:01,146 --> 00:28:04,138 for an entirely neW branch of the Earth sciences, 509 00:28:04,282 --> 00:28:05,909 geochronology - 510 00:28:06,051 --> 00:28:09,578 the direct measurement of the ages of rocks. 511 00:28:09,721 --> 00:28:12,087 One of its most distinguished practitioners 512 00:28:12,223 --> 00:28:14,248 is Stephen Moorbath. 513 00:28:14,392 --> 00:28:16,053 What Rutherford suggested 514 00:28:16,194 --> 00:28:18,253 Was that you could actually use 515 00:28:18,396 --> 00:28:22,162 the phenomenon of radioactivity to date rocks 516 00:28:22,300 --> 00:28:25,599 and he suggested that if you had a rock 517 00:28:25,737 --> 00:28:29,833 Which has a certain amount of uranium in it, 518 00:28:29,974 --> 00:28:31,908 the uranium Would in the course of time 519 00:28:32,043 --> 00:28:33,840 decay to the element lead 520 00:28:33,978 --> 00:28:35,843 by radioactive decay 521 00:28:35,980 --> 00:28:39,177 and one could measure the rate of that process 522 00:28:39,317 --> 00:28:40,682 so that if you took a rock 523 00:28:40,819 --> 00:28:42,184 and measured the amount of uranium 524 00:28:42,320 --> 00:28:43,617 and the amount of lead, 525 00:28:43,755 --> 00:28:45,586 and then you could calculate 526 00:28:45,724 --> 00:28:48,124 the actual age of the rock. 527 00:28:49,794 --> 00:28:52,058 So Rutherford - 528 00:28:52,197 --> 00:28:55,325 Well some of his younger colleagues actually - 529 00:28:55,467 --> 00:28:57,435 started to measure, 530 00:28:57,569 --> 00:29:01,232 take rocks and measure the uranium and lead content. 531 00:29:08,480 --> 00:29:12,109 Every rock contains its oWn radioactive clock. 532 00:29:12,250 --> 00:29:14,912 That clock starts ticking When the rock forms 533 00:29:15,053 --> 00:29:17,920 and neW minerals crystallise Within it. 534 00:29:18,056 --> 00:29:20,991 lmmediately the chemical composition of these minerals 535 00:29:21,126 --> 00:29:22,821 sloWly starts to change 536 00:29:22,961 --> 00:29:26,988 as radioactive decay turns one element into another. 537 00:29:35,607 --> 00:29:39,065 So after nearly tWo centuries of scientific endeavour, 538 00:29:39,210 --> 00:29:41,178 the age of the earth Would be revealed 539 00:29:41,312 --> 00:29:44,440 by a feW grains of sand. 540 00:29:46,084 --> 00:29:52,580 And they suggested that they found that rocks 541 00:29:52,724 --> 00:29:56,421 Were as old as a feW hundred million years 542 00:29:56,561 --> 00:29:59,428 and then very soon afterwards 543 00:29:59,564 --> 00:30:01,031 it Was found that there Were rocks 544 00:30:01,166 --> 00:30:04,329 Which Were 1 ,500 million years old, 545 00:30:04,469 --> 00:30:07,563 and this is a completely different order of magnitude 546 00:30:07,705 --> 00:30:11,539 to the estimates of the age of the earth, 547 00:30:11,676 --> 00:30:12,938 and the age of rocks 548 00:30:13,077 --> 00:30:15,307 that had been given before radioactivity 549 00:30:15,446 --> 00:30:17,038 Which tended to give figures like 550 00:30:17,182 --> 00:30:20,310 10, 20, 30 million years. 551 00:30:20,451 --> 00:30:23,716 What Rutherford did really at a stroke, 552 00:30:23,855 --> 00:30:26,915 Was to lengthen geological time 553 00:30:27,058 --> 00:30:30,858 by a factor of something like 100. 554 00:30:30,995 --> 00:30:33,395 And this Was greeted by the geologists 555 00:30:33,531 --> 00:30:35,624 With a great sigh of relief 556 00:30:35,767 --> 00:30:39,828 and it is really one of the major achievements 557 00:30:39,971 --> 00:30:41,666 of the 20th century 558 00:30:41,806 --> 00:30:45,264 that We noW can date rocks and minerals 559 00:30:45,410 --> 00:30:49,005 and things of that kind With greater and greater accuracy 560 00:30:49,147 --> 00:30:52,310 and see hoW the Whole history 561 00:30:52,450 --> 00:30:55,510 of the solar system and the Earth has unrolled. 562 00:31:01,826 --> 00:31:05,057 But to finally determine When our planet began, 563 00:31:05,196 --> 00:31:07,289 geologists still needed to find a rock 564 00:31:07,432 --> 00:31:11,061 left over from the time When the Earth Was forming. 565 00:31:19,077 --> 00:31:22,137 This rather inconspicuous looking object, 566 00:31:22,280 --> 00:31:24,009 it's part of a meteorite 567 00:31:24,148 --> 00:31:26,241 Which fell at a place called Allende 568 00:31:26,384 --> 00:31:30,445 in Mexico in February 1969. 569 00:31:30,588 --> 00:31:35,287 And it is actually the oldest knoWn object 570 00:31:35,426 --> 00:31:38,259 that We knoW of, that exists on Earth. 571 00:31:40,698 --> 00:31:41,892 lt's the oldest object 572 00:31:42,033 --> 00:31:45,400 that can be held by human hands. 573 00:32:04,956 --> 00:32:09,359 lt has an age of 4,566, 574 00:32:09,494 --> 00:32:12,895 plus or minus 2, million years. 575 00:32:13,031 --> 00:32:14,760 Actually most of the meteorites 576 00:32:14,899 --> 00:32:17,094 are in approximately the same range - 577 00:32:17,235 --> 00:32:19,999 just a feW million years younger - 578 00:32:20,138 --> 00:32:22,572 and its these little White inclusions here 579 00:32:22,707 --> 00:32:25,767 that give this fantastically old age. 580 00:32:25,910 --> 00:32:29,346 And it comes from the outer 581 00:32:29,480 --> 00:32:31,175 reaches of the solar system. 582 00:32:31,316 --> 00:32:36,151 lt's really a kind of residue of the material 583 00:32:36,287 --> 00:32:40,314 from Which the Whole solar system accreted, 584 00:32:40,458 --> 00:32:42,050 came together, compacted. 585 00:32:42,193 --> 00:32:43,387 lt's the building block 586 00:32:43,528 --> 00:32:46,395 of all the planets and the sun 587 00:32:46,531 --> 00:32:50,399 and that formation of the solar system 588 00:32:50,535 --> 00:32:53,663 and of the earth happened a feW tens, 589 00:32:53,805 --> 00:32:54,931 perhaps a hundred million years 590 00:32:55,073 --> 00:32:57,473 after the formation of this object, 591 00:32:57,608 --> 00:33:08,280 betWeen about 4,550 to 4,450 million years ago. 592 00:33:09,287 --> 00:33:10,686 Meteorites told scientists 593 00:33:10,822 --> 00:33:13,154 When the Earth started to form. 594 00:33:13,291 --> 00:33:15,555 But to knoW What the infant planet Was like, 595 00:33:15,693 --> 00:33:18,389 they needed to find a remnant of the early crust 596 00:33:18,529 --> 00:33:21,623 miraculously preserved at the surface. 597 00:33:21,766 --> 00:33:25,167 The search Was on for the oldest place on Earth. 598 00:33:26,904 --> 00:33:28,929 That quest took Stephen Moorbath 599 00:33:29,073 --> 00:33:32,975 to the edge of the great Greenland lce Cap. 600 00:33:39,817 --> 00:33:41,284 ln 1971 601 00:33:41,419 --> 00:33:44,877 Vic MacGregor and l heard about this area 602 00:33:45,023 --> 00:33:49,585 Which is about 150 kilometres north east of Knud, 603 00:33:49,727 --> 00:33:51,695 capital of Greenland, 604 00:33:51,829 --> 00:33:54,059 and a mining company Was up there 605 00:33:54,198 --> 00:33:56,928 exploring a big iron ore deposit, 606 00:33:57,068 --> 00:34:01,164 and Vic and l Were very keen to see this area. 607 00:34:01,305 --> 00:34:04,934 Vic made the first reliable geological map 608 00:34:05,076 --> 00:34:06,805 and he suggested 609 00:34:06,944 --> 00:34:10,778 that some of these rocks might be very old indeed. 610 00:34:22,627 --> 00:34:25,187 This place is called lsua. 611 00:34:25,329 --> 00:34:29,356 For Stephen it Was to prove the discovery of a life-time. 612 00:34:29,967 --> 00:34:31,958 We're standing right in the middle 613 00:34:32,103 --> 00:34:35,800 of the oldest knoWn rocks on the Earth. 614 00:34:35,940 --> 00:34:40,309 And they extend from the lake there, 615 00:34:40,445 --> 00:34:43,471 over to the other lake here. 616 00:34:55,093 --> 00:34:56,651 Well back in 1971 617 00:34:56,794 --> 00:34:58,227 When We first came up here 618 00:34:58,362 --> 00:35:00,523 We collected many of the rock types 619 00:35:00,665 --> 00:35:03,498 and then took them back to our laboratory 620 00:35:03,634 --> 00:35:06,569 to do the radioactive dating analysis 621 00:35:06,704 --> 00:35:10,435 and We found that many of these rock types around here 622 00:35:10,575 --> 00:35:14,978 have ages of nearly 3,800 million years 623 00:35:15,113 --> 00:35:19,243 Which is still the oldest age 624 00:35:19,383 --> 00:35:21,180 of any terrestrial rocks 625 00:35:21,319 --> 00:35:24,755 Which are as extensive as this. 626 00:35:24,889 --> 00:35:26,982 Well it came as quite a surprise. 627 00:35:27,125 --> 00:35:30,891 The age itself is very old 628 00:35:31,028 --> 00:35:33,588 in relation to the age of the Earth 629 00:35:33,731 --> 00:35:35,756 but also What's interesting is 630 00:35:35,900 --> 00:35:37,390 What these rocks can tell you about 631 00:35:37,535 --> 00:35:40,402 the environment of the early Earth. 632 00:35:40,905 --> 00:35:43,499 This is a particularly interesting unit here 633 00:35:43,641 --> 00:35:45,131 because as you can see 634 00:35:45,276 --> 00:35:48,404 it's full of thousands and thousands of round pebbles 635 00:35:48,546 --> 00:35:51,538 set in a fine grained matrix of mud, 636 00:35:51,682 --> 00:35:53,707 clay and shale. 637 00:35:53,851 --> 00:35:55,375 And this sort of rock 638 00:35:55,520 --> 00:35:58,114 Which geologists call a conglomerate, 639 00:35:58,256 --> 00:36:01,885 Were formed at a beach or a shoreline 640 00:36:02,026 --> 00:36:08,659 and the erosion by Water has rounded these pebbles, 641 00:36:08,799 --> 00:36:11,893 and it shoWs Without any doubt that Water existed 642 00:36:12,036 --> 00:36:15,096 at the surface of the Earth 3,800 million years ago, 643 00:36:15,239 --> 00:36:19,539 Which at that time came as a complete surprise. 644 00:36:27,285 --> 00:36:29,310 At lsua the ice has uncovered 645 00:36:29,453 --> 00:36:32,616 a tantalising glimpse of the early earth. 646 00:36:33,191 --> 00:36:35,284 But geologists' search for a place Where rocks 647 00:36:35,426 --> 00:36:38,020 might yield a more detailed picture of the young planet 648 00:36:38,162 --> 00:36:41,325 took them to the other side of the globe. 649 00:36:43,167 --> 00:36:44,657 The Barberton Mountain Land, 650 00:36:44,802 --> 00:36:46,599 in South Africa. 651 00:36:48,406 --> 00:36:51,136 Field area of Maarten de Wit 652 00:36:54,579 --> 00:36:55,841 Well it turns out that the oldest rocks 653 00:36:55,980 --> 00:36:59,177 at Barberton are about 3,500 million years old. 654 00:36:59,317 --> 00:37:00,409 Some of them slightly older, 655 00:37:00,551 --> 00:37:02,712 up to 3,700 million years. 656 00:37:02,853 --> 00:37:04,878 There are older rocks elseWhere in the World 657 00:37:05,022 --> 00:37:06,512 but What's so special about Barberton 658 00:37:06,657 --> 00:37:09,125 is that it's so incredibly Well preserved. 659 00:37:09,260 --> 00:37:11,285 Almost in a pristine state. 660 00:37:16,701 --> 00:37:19,761 Hall's original suspicion turned out to be correct. 661 00:37:19,904 --> 00:37:21,963 Barberton is the oldest extensive piece 662 00:37:22,106 --> 00:37:24,631 of the Earth's ancient surface. 663 00:37:24,775 --> 00:37:28,438 Here, the rocks at last really begin to speak. 664 00:37:29,113 --> 00:37:30,444 And it's not until you've Walked 665 00:37:30,581 --> 00:37:31,980 for Weeks and Weeks on end, 666 00:37:32,116 --> 00:37:33,743 all of a sudden you find one tiny little outcrop 667 00:37:33,884 --> 00:37:35,818 and you say ''Bingo, l've got it. 668 00:37:35,953 --> 00:37:37,716 That's What they've been trying to tell me. 669 00:37:37,855 --> 00:37:41,086 That's What makes it exciting. That's Why l'm a geologist.'' 670 00:37:44,895 --> 00:37:46,760 What the rocks of Barberton reveal 671 00:37:46,897 --> 00:37:49,866 is that 3.5 billion years ago 672 00:37:50,001 --> 00:37:52,765 the Earth Was a World of volcanoes. 673 00:37:55,539 --> 00:37:56,563 That's amazing, 674 00:37:56,707 --> 00:37:58,334 all these little globules. 675 00:37:58,476 --> 00:37:59,374 The physics of the formation 676 00:37:59,510 --> 00:38:01,478 is very like the formation of hailstones. 677 00:38:01,612 --> 00:38:03,477 These globules form in volcanic clouds 678 00:38:03,614 --> 00:38:06,378 Where very large volcanoes erupt violently, 679 00:38:06,517 --> 00:38:09,042 like Mount St Helens, for example. 680 00:38:16,093 --> 00:38:18,118 And as the volcanic hailstones form, 681 00:38:18,262 --> 00:38:19,854 they fall back to Earth, 682 00:38:19,997 --> 00:38:22,227 in this case on a layer in a lake. 683 00:38:22,366 --> 00:38:24,334 The biggest ones settled to the bottom 684 00:38:24,468 --> 00:38:27,266 and the smallest ones folloW. 685 00:38:27,838 --> 00:38:30,136 And as in Greenland there's abundant evidence 686 00:38:30,274 --> 00:38:33,300 that the volcanoes Were surrounded by Water. 687 00:38:48,292 --> 00:38:49,816 Look! These are the volcanic rocks 688 00:38:49,960 --> 00:38:51,154 and they're so characteristic 689 00:38:51,295 --> 00:38:53,126 and all over Barberton. 690 00:38:53,264 --> 00:38:54,891 And it's these funny shapes, 691 00:38:55,032 --> 00:38:56,897 these bulbs and these contorted things 692 00:38:57,034 --> 00:39:00,094 that We see all over this face here 693 00:39:00,237 --> 00:39:02,000 that tells us that these volcanic rocks 694 00:39:02,139 --> 00:39:04,232 Were erupted under Water. 695 00:39:07,745 --> 00:39:10,077 And the shape is a reaction 696 00:39:10,214 --> 00:39:12,512 of the lava onto the rocks on the Water, 697 00:39:12,650 --> 00:39:15,676 against the cool Water that Wants to cool it doWn. 698 00:39:17,054 --> 00:39:19,488 And as that freezes and forms this bulb 699 00:39:19,623 --> 00:39:21,454 it's like squeezing toothpaste out 700 00:39:21,592 --> 00:39:24,288 and piling it up on top of one another. 701 00:39:26,497 --> 00:39:29,091 Everywhere in Barberton We look it is these kind 702 00:39:29,233 --> 00:39:32,361 of rocks that alloW us to reconstruct 703 00:39:32,503 --> 00:39:35,336 that there Were huge tracks of ocean 704 00:39:35,473 --> 00:39:38,306 in this part of the World at that time. 705 00:39:40,111 --> 00:39:43,171 Where Was all this Water coming from? 706 00:39:45,483 --> 00:39:47,280 Look at this rock. 707 00:39:48,586 --> 00:39:50,747 See these textures on the rock. 708 00:39:50,888 --> 00:39:53,083 Very delicately preserved - 709 00:39:53,224 --> 00:39:55,385 almost as if birds have been Walking on this. 710 00:39:55,526 --> 00:39:58,086 They're actually little crystals. 711 00:40:02,666 --> 00:40:03,690 They almost look man-made 712 00:40:03,834 --> 00:40:06,962 but they're really natural crystals groWing. 713 00:40:10,207 --> 00:40:12,767 These rocks came from very high temperatures, 714 00:40:12,910 --> 00:40:14,810 crystallised out from magma 715 00:40:14,945 --> 00:40:16,503 that came from deep in the Earth 716 00:40:16,647 --> 00:40:18,239 very rapidly to the surface, 717 00:40:18,382 --> 00:40:23,285 high in volatile content, high in Water. 718 00:40:25,055 --> 00:40:26,647 The volcanoes erupting here 719 00:40:26,791 --> 00:40:28,452 Were producing vast quantities 720 00:40:28,592 --> 00:40:31,152 of Water vapour With the lava. 721 00:40:31,295 --> 00:40:33,263 lt Was this Water Which Was condensing to 722 00:40:33,397 --> 00:40:35,957 form the primitive ocean. 723 00:40:46,010 --> 00:40:49,241 The combination of volcanic activity and Water 724 00:40:49,380 --> 00:40:50,677 produced an environment Where 725 00:40:50,815 --> 00:40:54,046 a fascinating neW process could begin. 726 00:40:57,721 --> 00:41:01,350 My eye caught these structures by accident 727 00:41:01,492 --> 00:41:04,052 and When l looked at them l asked ''What is that?'' 728 00:41:04,195 --> 00:41:05,890 You knoW, l didn't have a clue What it Was. 729 00:41:06,030 --> 00:41:08,555 l'd never seen anything like this before. 730 00:41:08,699 --> 00:41:09,461 ln that same year 731 00:41:09,600 --> 00:41:13,502 l Went on a conference to NeW Zealand 732 00:41:13,637 --> 00:41:14,604 and during that conference 733 00:41:14,738 --> 00:41:17,571 l had a chance to sit around some of the mud pools 734 00:41:17,708 --> 00:41:18,800 in NeW Zealand 735 00:41:18,943 --> 00:41:20,103 and When l Was looking at them, 736 00:41:20,244 --> 00:41:22,405 While l Was looking at this bubbling mud, 737 00:41:22,546 --> 00:41:24,241 l all of a sudden remembered these structures 738 00:41:24,381 --> 00:41:25,245 and l thought ''WoW, that's it. 739 00:41:25,382 --> 00:41:27,350 That's got to be What it is.'' 740 00:41:28,719 --> 00:41:31,483 Ancient mud pool structures frozen in the rock here 741 00:41:31,622 --> 00:41:33,249 and What gives it aWay as a mud pool 742 00:41:33,390 --> 00:41:35,688 is of course all these intersections. 743 00:41:43,300 --> 00:41:45,359 What is even more interesting to think about 744 00:41:45,503 --> 00:41:47,596 is the Warmth of this area 745 00:41:47,738 --> 00:41:50,400 and the sort of niche it might have created 746 00:41:50,541 --> 00:41:52,873 for bacteria, for example, to be sWimming around. 747 00:41:53,010 --> 00:41:55,410 And this is, of course, one of the sites 748 00:41:55,546 --> 00:41:56,877 We might be thinking about 749 00:41:57,014 --> 00:41:59,710 Where life might have started. 750 00:42:02,286 --> 00:42:04,447 And in fact, just recently Maarten 751 00:42:04,588 --> 00:42:07,489 has made another remarkable find. 752 00:42:12,830 --> 00:42:13,819 Well these sedimentary rocks, 753 00:42:13,964 --> 00:42:15,397 they've locked inside them 754 00:42:15,533 --> 00:42:18,195 the very earliest signs of life on this planet. 755 00:42:18,335 --> 00:42:19,825 They're very tiny 756 00:42:19,970 --> 00:42:21,870 and When you look through the microscope at these rocks 757 00:42:22,006 --> 00:42:24,941 you'll see tiny little bacteria. 758 00:42:30,347 --> 00:42:31,507 And it's these bacteria 759 00:42:31,649 --> 00:42:34,482 that are the first Well preserved signs 760 00:42:34,618 --> 00:42:36,779 of life on this planet. 761 00:42:43,694 --> 00:42:46,060 All geologists are time travellers 762 00:42:46,196 --> 00:42:49,962 but feW have travelled as far as Maarten de Wit. 763 00:42:51,035 --> 00:42:52,195 He has ventured back in time 764 00:42:52,336 --> 00:42:55,032 almost as far as the rocks Will take him, 765 00:42:55,172 --> 00:42:59,040 to a planet very different from the World We knoW today. 766 00:43:06,717 --> 00:43:09,652 lt's quite remarkable to think that 767 00:43:09,787 --> 00:43:11,448 geologists over the last 100 years 768 00:43:11,589 --> 00:43:15,116 have been able to collect all this data to alloW us 769 00:43:15,259 --> 00:43:16,624 to piece together What the early earth, 770 00:43:16,760 --> 00:43:18,022 the young earth, the juvenile earth 771 00:43:18,162 --> 00:43:22,656 might have looked like 3.5 million years ago. 772 00:43:22,800 --> 00:43:24,267 And in many Ways Barberton 773 00:43:24,401 --> 00:43:26,426 has played a very big role in this. 774 00:43:26,570 --> 00:43:30,597 The unique preservations of all the features in Barberton 775 00:43:30,741 --> 00:43:34,040 alloW us to have to very firm picture 776 00:43:34,178 --> 00:43:35,110 of What that planet, 777 00:43:35,245 --> 00:43:37,839 the skin of the planet, might have looked like. 778 00:43:37,982 --> 00:43:39,449 There Would have been lots of continents, 779 00:43:39,583 --> 00:43:42,245 little continents, rocks basically, 780 00:43:42,386 --> 00:43:45,184 With lots of volcanoes reaching the surface. 781 00:43:45,322 --> 00:43:47,813 So We Would have seen a tremendous amount of volcanic activity. 782 00:43:47,958 --> 00:43:50,984 Gasses, lava floWs everywhere. 783 00:44:03,207 --> 00:44:05,232 This Whole process Would have been 784 00:44:05,376 --> 00:44:09,506 driven at a faster rate than We see today. 785 00:44:09,647 --> 00:44:11,512 There's more energy inside the planet 786 00:44:11,649 --> 00:44:13,378 through this huge amount 787 00:44:13,517 --> 00:44:16,850 of radioactive heat that's trying to escape. 788 00:44:20,024 --> 00:44:22,515 All this volcanic activity Was constantly 789 00:44:22,660 --> 00:44:26,255 adding neW material to the groWing continents. 790 00:44:30,034 --> 00:44:32,332 But there Were no plants to soften the contours 791 00:44:32,469 --> 00:44:34,528 of the neWly created land 792 00:44:34,672 --> 00:44:38,631 and Without plants no oxygen in the atmosphere. 793 00:44:47,885 --> 00:44:52,913 But around bubbling volcanic pools bacteria thrived, 794 00:45:03,734 --> 00:45:08,137 And the volcanoes also produced vast quantities of Water vapour. 795 00:45:10,407 --> 00:45:12,136 As it rained back to the surface, 796 00:45:12,276 --> 00:45:15,143 it eroded the neW rocks. 797 00:45:15,279 --> 00:45:17,247 On the bottom of the primitive ocean 798 00:45:17,381 --> 00:45:20,748 sedimentary layers started to form. 799 00:45:21,285 --> 00:45:25,722 80/90% , 95% perhaps of the planet Would have been ocean 800 00:45:25,856 --> 00:45:27,255 and We knoW from our observations that 801 00:45:27,391 --> 00:45:29,154 the oceans must have been shalloW. 802 00:45:29,293 --> 00:45:32,228 ShalloW oceans over most of the planet. 803 00:45:32,830 --> 00:45:35,526 Since the scientific study of our planet began, 804 00:45:35,666 --> 00:45:39,397 geologists have been learning to travel through time. 805 00:45:39,536 --> 00:45:42,266 Thanks to places like lsua and Barberton 806 00:45:42,406 --> 00:45:45,432 they have been able to achieve something quite remarkable - 807 00:45:45,576 --> 00:45:48,704 to shoW us our World being born. 808 00:45:52,816 --> 00:45:55,148 This is the Earth as it is at the very limit 809 00:45:55,285 --> 00:45:58,049 of our scientific imagination. 810 00:46:01,759 --> 00:46:04,557 As far as the record in the rocks is concerned, 811 00:46:04,695 --> 00:46:07,823 this is the beginning of the Earth's story.