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Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 1 00:00:36,975 --> 00:00:42,493 THE LIVING PLANET 2 00:00:42,588 --> 00:00:46,163 A PORTRAIT OF THE EARTH 3 00:00:52,636 --> 00:00:58,082 Our planet, the earth, is, as far as we know, unique in the universe. 4 00:00:58,146 --> 00:01:04,466 It contains life. Even in its most barren stretches, there are animals. 5 00:01:16,220 --> 00:01:19,524 Around the equator, where those two essentials for life, 6 00:01:19,588 --> 00:01:24,280 sunshine and moisture, are most abundant, great forests grow, 7 00:01:24,344 --> 00:01:27,954 and here plants and animals proliferate in such numbers 8 00:01:28,018 --> 00:01:32,360 that we still have not even named all the different species. 9 00:01:44,204 --> 00:01:49,797 Here, animals and plants, insects and birds, mammals and man 10 00:01:49,861 --> 00:01:52,780 live together in intimate and complex communities, 11 00:01:52,844 --> 00:01:55,351 each dependent on one another. 12 00:01:58,482 --> 00:02:02,643 Two thirds of the surface of this unique planet are covered by water, 13 00:02:02,707 --> 00:02:06,084 and it was here indeed that life began. 14 00:02:16,968 --> 00:02:21,194 From the oceans, it has spread even to the summits of the highest mountains, 15 00:02:21,258 --> 00:02:26,411 as animals and plants have responded to the changing face of the earth. 16 00:02:29,777 --> 00:02:35,792 THE BUILDING OF THE EARTH 17 00:02:43,596 --> 00:02:49,016 This river, the Kali Gandaki, has cut its way, in the most remarkable fashion, 18 00:02:49,080 --> 00:02:53,267 right through the highest range of mountains in the world, the Himalaya. 19 00:02:53,654 --> 00:02:58,602 To the east of me rises Annapurna, over 26,000 feet high. 20 00:02:58,666 --> 00:03:01,804 To the west, Dhaulagiri, even higher. 21 00:03:02,249 --> 00:03:05,982 Their two summits are a mere 22 miles apart, 22 00:03:06,046 --> 00:03:09,648 and I am four vertical miles below them. 23 00:03:09,712 --> 00:03:12,810 And that makes this the deepest valley in the world. 24 00:03:12,874 --> 00:03:17,155 At this altitude, about 7,000 feet, it's quite warm, 25 00:03:17,219 --> 00:03:22,484 and animal and plant life on the flanks of the valley is both rich and abundant. 26 00:03:24,216 --> 00:03:27,372 The blossoms on these trees may well look familiar. 27 00:03:27,436 --> 00:03:30,104 Flowers like them grow in gardens all over the world. 28 00:03:30,168 --> 00:03:36,239 But these are wild plants and this is their original home. They're rhododendrons. 29 00:03:38,757 --> 00:03:42,105 And here they are food for monkeys, grey langurs, 30 00:03:42,169 --> 00:03:45,401 reminders that the hot plains of Southern Nepal and the tropics 31 00:03:45,465 --> 00:03:47,843 are not far away to the south. 32 00:04:00,091 --> 00:04:04,647 But they aren't just monkey food. They are the rhododendrons' advertisements, 33 00:04:04,711 --> 00:04:08,941 attracting birds and insects which will sip their nectar, gather their pollen, 34 00:04:09,005 --> 00:04:11,621 and so bring about their fertilisation. 35 00:04:20,096 --> 00:04:23,215 The ring-necked parakeet also comes from the tropics. 36 00:04:23,279 --> 00:04:28,709 Here, it's at the top of its range. Any higher and the weather will be too cold for it. 37 00:04:29,781 --> 00:04:32,540 Beneath the rhododendrons live several species 38 00:04:32,604 --> 00:04:36,206 of those most splendid of Asia's birds, the pheasants. 39 00:04:36,270 --> 00:04:41,374 The blood pheasant, for all its delicate beauty, is a plainer member of the family. 40 00:04:42,420 --> 00:04:46,329 The cock Tragopan is surely the most magnificent. 41 00:04:55,005 --> 00:04:59,085 Until, that is, you see a cock Impeyan pheasant, 42 00:05:00,004 --> 00:05:02,783 with the coronet of a peacock and the burnished, 43 00:05:02,847 --> 00:05:06,270 metallic iridescence of a tropical butterfly. 44 00:05:13,927 --> 00:05:18,647 The Impeyan's hen, like those of all pheasants, is comparatively dull. 45 00:05:33,755 --> 00:05:38,678 This deepest of all valleys in the world enables you to walk within a few days 46 00:05:38,742 --> 00:05:40,975 from the tropics, in its lower reaches, 47 00:05:41,039 --> 00:05:44,519 to the equivalent of the poles on the slopes high above, 48 00:05:44,583 --> 00:05:46,914 and to see as you make the journey 49 00:05:46,978 --> 00:05:51,907 how closely animals and plants are matched to the changing circumstances. 50 00:05:51,971 --> 00:05:56,926 As you walk higher, the rhododendron forest gets thinner and becomes hung with moss. 51 00:05:57,051 --> 00:06:00,633 The air is still moist and it can be quite warm during the day. 52 00:06:00,697 --> 00:06:03,841 And now, in summer, there are orchids here. 53 00:06:11,917 --> 00:06:16,212 On the ground beneath, flowers appear in close-packed bunches, 54 00:06:16,276 --> 00:06:19,460 protecting one another from the night frosts. 55 00:06:23,329 --> 00:06:27,999 The little Himalayan panda is certainly very well protected against the cold. 56 00:06:28,308 --> 00:06:32,279 Not only does it have warm, dense fur, but, like many animals 57 00:06:32,343 --> 00:06:37,120 that spend some of their time in the snow, it has hair on the soles of its feet. 58 00:06:37,525 --> 00:06:43,038 That not only keeps its feet warm on the snow but stops it from sliding around on ice. 59 00:06:43,102 --> 00:06:48,879 Now, in the summer, it also helps in getting a grip on wet, slippery branches. 60 00:06:53,758 --> 00:06:57,933 It's primarily a vegetarian, collecting buds and leaves and fruit, 61 00:06:57,997 --> 00:07:02,249 but it also takes eggs from a bird's nest, if it can find one. 62 00:07:06,739 --> 00:07:09,817 On the ground, and scarcely bigger than the panda, 63 00:07:09,881 --> 00:07:14,789 one of the shyest animals of the Himalayan forests, a musk deer. 64 00:07:19,291 --> 00:07:23,663 In these tangled trees, antlers would be a considerable handicap, 65 00:07:23,727 --> 00:07:26,142 and the musk deer doesn't develop them. 66 00:07:26,337 --> 00:07:30,321 A male fights instead with the short sharp tusks in his upper jaw. 67 00:07:30,406 --> 00:07:33,869 They feed on moss, lichen and leaves, 68 00:07:33,933 --> 00:07:36,967 and are so agile and well-adapted to a mountain life 69 00:07:37,031 --> 00:07:40,472 that they can climb steep cliffs in search of food. 70 00:07:43,501 --> 00:07:49,041 When a musk deer or any other animal of any size dies, the vultures come. 71 00:07:55,527 --> 00:07:59,014 These are griffons, very similar to those that circle the skies 72 00:07:59,078 --> 00:08:02,380 above Indian villages down in the hot foothills. 73 00:08:02,444 --> 00:08:06,339 They are common in this forest up to 7,000 or 8,000 feet. 74 00:08:30,317 --> 00:08:35,444 So the lives of all these creatures are connected, 75 00:08:35,508 --> 00:08:38,956 one with the other, either directly or indirectly, 76 00:08:39,020 --> 00:08:43,063 and all are ultimately dependent upon the vegetation. 77 00:08:43,483 --> 00:08:45,766 But of course, both animals and plants 78 00:08:45,830 --> 00:08:48,991 are also greatly affected by the physical environment. 79 00:08:49,187 --> 00:08:54,137 I've climbed several thousand feet now and things are beginning to change. 80 00:08:54,456 --> 00:08:59,960 It's getting colder, and the rhododendrons are giving way to fir trees, 81 00:09:00,024 --> 00:09:04,187 and that will mean a change in the animals that live here. 82 00:09:07,875 --> 00:09:11,235 The yellow-throated martin has a fairly broad taste in food. 83 00:09:11,299 --> 00:09:15,383 It takes fruit on occasion, catches the few insects now and then, 84 00:09:15,447 --> 00:09:19,742 but it relishes above all small rodents, like mice and squirrels, 85 00:09:19,806 --> 00:09:22,306 and there are quite a lot their found here. 86 00:09:22,489 --> 00:09:27,261 Even when winter comes, when the forests are deep in snow, it will remain active. 87 00:09:27,470 --> 00:09:30,775 But it's a great traveller, and if the weather becomes very cold indeed, 88 00:09:30,839 --> 00:09:34,074 it will descend to lower altitudes for a spell. 89 00:09:45,459 --> 00:09:49,630 The Himalayan bear is capable of living very high indeed. 90 00:09:49,694 --> 00:09:53,300 Its thick fur protects it against really severe cold, 91 00:09:53,364 --> 00:09:57,791 but its range is not limited by temperature so much as by food supply. 92 00:09:58,045 --> 00:10:02,578 In spite of its huge size, it seldom tackles any animal bigger than a mouse, 93 00:10:02,642 --> 00:10:07,693 and it lives for most of the time on just ants, grubs, nuts and leaves, 94 00:10:07,757 --> 00:10:11,638 so it seldom goes any higher than the forest can grow. 95 00:10:18,906 --> 00:10:24,516 And now, getting on for 10,000 feet up, the forest is beginning to thin. 96 00:10:24,705 --> 00:10:29,533 In summer, there's not much rain here, for it most has fallen at lower altitudes. 97 00:10:29,783 --> 00:10:32,711 In winter, it gets extremely cold. 98 00:10:32,775 --> 00:10:38,860 Those conditions don't suit rhododendrons. Here only conifers flourish in large numbers. 99 00:10:40,494 --> 00:10:44,576 High though we are, the Kali Gandaki is still a very broad river. 100 00:10:44,718 --> 00:10:47,225 Remarkably, and indeed mysteriously, 101 00:10:47,289 --> 00:10:52,560 it doesn't rise from the flanks of these giant mountains but cuts right through them. 102 00:10:53,273 --> 00:10:56,231 The people of the foothills have long since recognised 103 00:10:56,295 --> 00:11:00,832 the value of this extraordinary corridor that leads right through the Himalayas, 104 00:11:00,896 --> 00:11:04,608 and all summer trains of mules trudge up the valley, 105 00:11:04,672 --> 00:11:09,694 taking barley and buckwheat to trade with Tibetans for wool and salt. 106 00:11:12,820 --> 00:11:17,412 All the way up the valley there are villages where the muleteers can stay and rest, 107 00:11:17,723 --> 00:11:20,440 but during the summer few do so. 108 00:11:20,827 --> 00:11:24,765 Most trudge tirelessly upwards for as long as there's daylight. 109 00:12:13,182 --> 00:12:16,499 A lammergeier, the bearded vulture, a mountain bird 110 00:12:16,563 --> 00:12:22,016 that soars around the high valleys of Asia and still in a few remote parts of Europe, 111 00:12:22,160 --> 00:12:24,653 but nowhere higher than this. 112 00:12:30,435 --> 00:12:34,793 And a sign that now we are getting really high: Snow cock. 113 00:12:34,857 --> 00:12:38,977 Its dappled white plumage gives it good camouflage against the broken snow 114 00:12:39,041 --> 00:12:42,970 that even now, in summer, can fall at these altitudes. 115 00:12:43,034 --> 00:12:46,621 They forage for seeds and rootlets in the thin turf. 116 00:12:58,029 --> 00:13:02,803 There are no trees now, just a few small shrubs and dry, withered grass. 117 00:13:02,867 --> 00:13:05,125 But that's enough for the tahr. 118 00:13:05,189 --> 00:13:09,988 It is neither a true sheep nor a true goat, but related equally to them both. 119 00:13:10,052 --> 00:13:15,781 It will eat almost anything that's green, and is grateful to find it in this bleak land. 120 00:13:16,446 --> 00:13:21,067 Another typically mountain creature: The red-billed chough, a kind of crow. 121 00:13:21,131 --> 00:13:26,939 They search the rocks for insects, grubs, odd seeds. They will take most things. 122 00:13:35,256 --> 00:13:40,044 Their cousins, yellow-billed choughs, go as high as any bird in the world, 123 00:13:40,108 --> 00:13:45,453 riding the rising wind currents to the height of the snow peaks themselves. 124 00:14:10,509 --> 00:14:15,225 Flowers at this altitude can only come from small cushion plants, 125 00:14:15,289 --> 00:14:17,815 huddled together against the cold. 126 00:14:18,773 --> 00:14:22,005 Higher still, little can grow except lichens. 127 00:14:22,069 --> 00:14:26,967 Now it's so cold that growth may only be possible for a few days in the year. 128 00:14:29,664 --> 00:14:34,072 And yet, in these bleak regions, people live. 129 00:14:34,331 --> 00:14:37,180 To help plough the fields, they use the yak, 130 00:14:37,244 --> 00:14:41,403 a domesticated creature that once roamed wild on the plains of Tibet, 131 00:14:41,467 --> 00:14:46,092 the only large mammal that lives permanently as high as man. 132 00:14:48,770 --> 00:14:53,781 The people, Bhotias and Sherpas, grow not only barley but potatoes, 133 00:14:53,845 --> 00:14:57,341 a crop that was first cultivated by the Incas in the Andes 134 00:14:57,405 --> 00:15:01,247 and was introduced here a century or so ago. 135 00:15:02,039 --> 00:15:06,350 These highland people are well-adapted to life at these altitudes. 136 00:15:06,751 --> 00:15:11,115 Their blood contains a particularly high number of red corpuscles 137 00:15:11,494 --> 00:15:16,043 and so can carry more oxygen in it than a lowlander's can. 138 00:15:17,019 --> 00:15:21,803 Certainly, when it comes to walking at these high altitudes, 139 00:15:22,344 --> 00:15:25,816 they're very much better adapted than I am. 140 00:15:26,619 --> 00:15:32,096 So, all the living creatures in these high valleys 141 00:15:32,347 --> 00:15:36,605 are adapted to their environment, both their biological environment 142 00:15:36,669 --> 00:15:41,946 and their physical environment. And yet, in terms of biological history, 143 00:15:42,235 --> 00:15:46,432 those adaptations are very recent indeed. 144 00:15:46,782 --> 00:15:51,114 These immense mountains, the eternal hills, 145 00:15:51,178 --> 00:15:54,350 are in fact far from eternal. 146 00:15:55,166 --> 00:15:59,956 They are younger than the plains of India to the south 147 00:16:00,165 --> 00:16:02,876 or the plateau of Tibet to the north. 148 00:16:02,975 --> 00:16:09,587 They were raised to their present height about 65 million years ago 149 00:16:09,651 --> 00:16:11,852 from the bottom of the sea. 150 00:16:11,947 --> 00:16:15,780 And what is the evidence for that extraordinary statement? 151 00:16:15,942 --> 00:16:20,252 It can be found all over the place, just up here. 152 00:16:28,613 --> 00:16:32,752 These slopes are littered 153 00:16:33,887 --> 00:16:39,023 with fragments like these. 154 00:16:40,365 --> 00:16:45,444 This is obviously a shell that's been turned to stone, a fossil. 155 00:16:45,728 --> 00:16:50,690 Although there are no molluscs alive today exactly like this one, 156 00:16:50,754 --> 00:16:56,427 there are some which are sufficiently similar for us to be sure that it lived in water. 157 00:16:56,558 --> 00:17:00,684 And if we analyse the rock in which it's embedded, 158 00:17:00,822 --> 00:17:06,226 it's clear that that was mud laid down at the bottom of a sea. 159 00:17:06,901 --> 00:17:10,721 But I am about as far as possible is it's to be from the sea. 160 00:17:10,785 --> 00:17:14,741 Not only am I in the middle of Asia, hundreds of miles from the sea, 161 00:17:14,963 --> 00:17:18,663 but I am over two vertical miles above it's level. 162 00:17:18,727 --> 00:17:23,631 What forces could possibly have raised the seabed to these heights? 163 00:17:24,037 --> 00:17:27,462 We now know that those forces are still in action, 164 00:17:27,526 --> 00:17:34,415 that these mountains are still rising and that land is still being created. 165 00:17:58,435 --> 00:18:02,899 I'm in Iceland. This fantastic fountain of fire 166 00:18:02,963 --> 00:18:08,307 rising 200 feet or so into the air behind me is molten rock. 167 00:18:09,079 --> 00:18:15,159 Fine ash is falling all around, there are gusts of choking, poisonous gas, 168 00:18:15,223 --> 00:18:20,635 and it's so hot that this is just about as close as I can get to it. 169 00:18:35,402 --> 00:18:39,090 The sheer weight of these molten ingots of rock 170 00:18:39,154 --> 00:18:43,097 prevents them being swept away from the vent by the gale, 171 00:18:43,161 --> 00:18:46,632 so there's little danger of them suddenly coming our way. 172 00:18:51,832 --> 00:18:56,192 Less dramatic than the fire fountain but perhaps more sinister 173 00:18:56,256 --> 00:19:02,646 is this tide of black slag that is slowly creeping over the surface of the land. 174 00:19:02,886 --> 00:19:07,197 In parts it's red-hot and molten and flows like treacle, 175 00:19:07,353 --> 00:19:12,289 but on the edges it's cooled enough for me to be able to handle it. 176 00:19:12,561 --> 00:19:17,012 It's black, it's heavy and it's called basalt. 177 00:19:17,227 --> 00:19:22,327 Basalt like this has been welling up from deep in the earth's crust 178 00:19:22,391 --> 00:19:25,816 ever since the beginning of the history of our planet. 179 00:19:35,959 --> 00:19:39,786 A flow may travel for as much as 25 miles. 180 00:19:39,850 --> 00:19:43,167 Sometimes it moves no faster than a man can walk, 181 00:19:43,231 --> 00:19:47,154 but sometimes it races along at an extraordinary speed, 182 00:19:47,218 --> 00:19:51,271 40 miles an hour, and nothing... nothing... can stop it. 183 00:20:03,890 --> 00:20:06,496 Sometimes so much lava is produced 184 00:20:06,560 --> 00:20:10,382 that it accumulates in flows 100 feet or so thick. 185 00:20:10,533 --> 00:20:15,075 Then the centre layers of it cool exceptionally slowly and very evenly, 186 00:20:15,603 --> 00:20:17,937 and this is the result. 187 00:20:19,648 --> 00:20:24,622 Here, at the Giant's Causeway island, the top of the lava flow has been eroded away, 188 00:20:24,686 --> 00:20:28,100 for the eruptions took place 50 million years ago. 189 00:20:28,327 --> 00:20:32,748 The cooling contractions have produced the effect you can sometime see in drying mud, 190 00:20:32,835 --> 00:20:35,658 though here the cracks extend to a much greater depth 191 00:20:35,722 --> 00:20:39,994 to produce six-sided columns about a foot and a half across. 192 00:20:42,886 --> 00:20:46,214 Over the sea, in the Hebrides, there's another lava flow 193 00:20:46,278 --> 00:20:50,454 that erupted at about the same time and formed Fingal's Cave. 194 00:20:55,790 --> 00:21:01,415 The blanceting layer of lava that slowed down the cooling of the interior is still uneroded, 195 00:21:01,479 --> 00:21:06,768 and beneath it the near-perfect basalt columns rise almost 20 feet high. 196 00:21:30,749 --> 00:21:36,378 Basalt that doesn't contain very much gas wells out from below almost quietly. 197 00:22:07,941 --> 00:22:10,963 But if the lava has been extruded under great pressure, 198 00:22:11,027 --> 00:22:15,503 it may be full of gas, and then it behaves very differently. 199 00:22:23,711 --> 00:22:29,609 Sometimes a flow sweeps down over a forest, incinerating the trees in its path. 200 00:22:51,163 --> 00:22:57,663 Most dramatic of all, the lava sometimes wells up inside the deep crater and can't escape. 201 00:22:57,727 --> 00:23:02,541 Then it forms that most fearsome of nature's spectacles, a lava lake, 202 00:23:02,605 --> 00:23:05,520 like this one in Nyiragongo in Africa. 203 00:23:05,802 --> 00:23:12,053 This lava is over 1,000 degrees centigrade, 2,000 degrees Fahrenheit. 204 00:23:12,180 --> 00:23:16,830 The bubbles of gas that burst from its surface may be 50 feet across. 205 00:23:17,204 --> 00:23:21,851 Sometimes, having got rid of much of its gas, like beer losing its fizz, 206 00:23:21,915 --> 00:23:25,405 it sinks back down the vast pipe up which it roses 207 00:23:25,469 --> 00:23:29,690 and returns to the lava chamber a mile or so below. 208 00:23:31,754 --> 00:23:35,053 But lava lakes fed by pipes are not common. 209 00:23:35,183 --> 00:23:40,757 Basalt more usually comes to the surface of the Earth in a rather different way. 210 00:23:51,794 --> 00:23:57,958 These Icelandic volcanoes erupt from huge cracks or fissures 211 00:23:58,022 --> 00:24:03,837 which regularly open up in a line which runs right across the width of the island. 212 00:24:04,019 --> 00:24:09,740 But that line itself is only the northern end of a huge line of weakness 213 00:24:09,804 --> 00:24:14,023 that runs for thousands of miles southwards from Iceland 214 00:24:14,087 --> 00:24:16,480 right round the side of the globe. 215 00:24:18,830 --> 00:24:22,984 Iceland lies between Norway and Greenland, south of the Arctic Circle. 216 00:24:23,048 --> 00:24:27,029 The crack, ridged over by lava, is mostly underwater, 217 00:24:27,093 --> 00:24:31,365 which is why its existence wasn't known until the beginning of this century. 218 00:24:31,625 --> 00:24:35,285 From Iceland it runs midway between Europe and Africa to the east 219 00:24:35,349 --> 00:24:39,354 and the Americas to the west. In places, it rises above the sea 220 00:24:39,418 --> 00:24:43,497 to form volcanic islands: The Azores, the Cape Verdes, 221 00:24:43,561 --> 00:24:47,181 Ascension, St Helena, Tristan da Cunha. 222 00:24:47,272 --> 00:24:51,336 But below the surface the lava is also continually erupting, 223 00:24:51,400 --> 00:24:55,168 unseen by human eyes until only a few years ago. 224 00:25:27,166 --> 00:25:30,090 The clouds of gas come from the lava itself. 225 00:25:30,154 --> 00:25:35,405 They're not steam. The pressure of the water prevents that from being produced. 226 00:25:35,588 --> 00:25:39,436 The heat is rapidly absorbed by the vastness of the ocean itself 227 00:25:39,500 --> 00:25:44,379 so that the lava cools and congeals much more quickly than it would do in the air. 228 00:25:53,035 --> 00:25:57,535 Eruptions like these, at great depths, built the Atlantic ridge. 229 00:25:57,599 --> 00:26:03,747 But the basalt forms not only the ridge itself but the sea floor on either side. 230 00:26:04,153 --> 00:26:07,786 By dating it chemically, we know that the farther way it is 231 00:26:07,850 --> 00:26:10,863 from the centre of the ridge, the older it is. 232 00:26:11,127 --> 00:26:15,351 This means that basalt is welling up in a molten state at the ridge 233 00:26:15,415 --> 00:26:20,076 and then, as it solidifies, is moving away on either side. 234 00:26:20,508 --> 00:26:24,349 We still don't fully understand the forces that power the process, 235 00:26:24,413 --> 00:26:28,491 but it seems that 50 to 60 miles below the earth's surface 236 00:26:28,555 --> 00:26:31,575 it's so hot that the rocks are molten 237 00:26:31,639 --> 00:26:36,382 and currents in them are welling up beneath the ridge, causing eruptions, 238 00:26:36,446 --> 00:26:39,143 and then flowing away on either side, 239 00:26:39,207 --> 00:26:42,360 pulling the great plates of the ocean floor with them. 240 00:26:42,543 --> 00:26:46,695 It was this movement that dragged apart Africa and South America 241 00:26:46,759 --> 00:26:49,490 and created the Atlantic Ocean. 242 00:26:53,346 --> 00:26:55,877 Similar things have happened in the Pacific. 243 00:26:55,988 --> 00:26:59,740 The great plate that forms the eastern part of the ocean floor 244 00:26:59,804 --> 00:27:02,930 is moving towards the west coast of America. 245 00:27:03,133 --> 00:27:06,888 But where it meets the continent, it dives downwards, 246 00:27:06,952 --> 00:27:10,300 perhaps pulled by the descending current in the crust below, 247 00:27:10,364 --> 00:27:13,714 producing a deep trench in the ocean floor. 248 00:27:15,478 --> 00:27:18,757 As it goes down, it takes with it some of the sediments 249 00:27:18,821 --> 00:27:22,913 that accumulated of the bottom of the ocean and also some water. 250 00:27:23,652 --> 00:27:27,179 These new ingredients melt with the basalt as they get deeper 251 00:27:27,243 --> 00:27:30,808 and interact with the rocks of the interior to produce a mixture 252 00:27:30,872 --> 00:27:35,318 that is crucially different from the lava that erupted at the ocean ridge. 253 00:27:35,663 --> 00:27:40,463 For one thing, it contains much more dissolved gas and steam. 254 00:27:42,219 --> 00:27:45,200 As it rises up in the cracks on the edge of the continent, 255 00:27:45,264 --> 00:27:48,867 it cools and solidifies, choking the vents. 256 00:27:49,703 --> 00:27:53,826 The effect is like screwing down the safety valve of a boiler. 257 00:28:11,938 --> 00:28:15,218 Mount St Helens on the Pacific coast of North America. 258 00:28:15,502 --> 00:28:17,793 On May 18th 1980, 259 00:28:17,857 --> 00:28:22,948 with an explosion 500 times as powerful as the atomic blast at Hiroshima, 260 00:28:23,041 --> 00:28:26,975 it blew away three-quarters of a cubic mile of rock. 261 00:28:28,789 --> 00:28:32,520 The forests around the mountain were totally destroyed. 262 00:28:32,584 --> 00:28:36,998 Trees 200 feet tall lay scattered like matchsticks. 263 00:28:38,216 --> 00:28:40,629 Geologists, weeks beforehand, 264 00:28:40,693 --> 00:28:44,143 watching a huge bulge develop on the side of the mountain, 265 00:28:44,207 --> 00:28:46,879 had warned of the coming catastrophe. 266 00:28:47,196 --> 00:28:51,796 Even so, over 60 people stayed and were killed. 267 00:29:03,147 --> 00:29:07,968 On the northern side of the volcano, there were not even trees to be seen. 268 00:29:08,054 --> 00:29:11,990 A huge avalanche of rock, blown out by the blast, 269 00:29:12,054 --> 00:29:17,581 had slid for 15 miles down the side of the mountain, burying everything. 270 00:29:21,367 --> 00:29:24,683 Behind it, Mount St Helens lay wrecked. 271 00:29:24,747 --> 00:29:27,339 Its summit was over 1,000 feet lower, 272 00:29:27,403 --> 00:29:32,033 and at the back of a huge amphitheatre, a mile wide from which the rock had come, 273 00:29:32,152 --> 00:29:37,339 another ominous bulge was developing, swathed in jets of steam. 274 00:29:52,941 --> 00:29:56,935 Almost a century earlier, on the opposite side of the Pacific, 275 00:29:56,999 --> 00:30:02,541 another catastrophic eruption had taken place on the tiny island of Krakatau, 276 00:30:02,605 --> 00:30:07,823 in the straits between Java to the east and Sumatra to the west. 277 00:30:08,263 --> 00:30:12,949 In 1883 it was an island five miles long and three miles wide, 278 00:30:13,013 --> 00:30:18,445 with three volcanic peaks on it, the highest of which rose to almost 3,000 feet. 279 00:30:18,871 --> 00:30:23,548 But those peaks were dormant. There had been no sign of any volcanic activity on Krakatau 280 00:30:23,612 --> 00:30:28,245 within living memory. But then, in August of that year, 281 00:30:28,309 --> 00:30:32,186 people on the coast of Java began to hear series of explosions. 282 00:30:32,250 --> 00:30:35,865 A great column of smoke rose above Krakatau. 283 00:30:36,814 --> 00:30:41,913 Pieces of lava the size of a house were being thrown high into the air. 284 00:30:42,019 --> 00:30:45,488 The explosions continued day after day. 285 00:30:45,552 --> 00:30:52,064 The column of smoke rose up until it was five miles or so up into the sky. 286 00:30:52,444 --> 00:30:57,573 Ships that were sailing nearby had their decks covered in ash and pumice, 287 00:30:57,637 --> 00:31:01,824 and at night electric flames played over the rigging. 288 00:31:02,033 --> 00:31:05,503 Day after day this continued. And as it was doing so, 289 00:31:05,567 --> 00:31:10,784 it was emptying the lava chamber deep in the crust beneath the sea, 290 00:31:10,848 --> 00:31:14,787 and that was the cause of the greatest catastrophe of all. 291 00:31:14,936 --> 00:31:20,700 Because on the morning of August 27th, Monday, at 10 o'clock, 292 00:31:21,063 --> 00:31:24,783 the roof of that lava chamber collapsed. 293 00:31:25,183 --> 00:31:28,545 Millions of tons of sea water poured onto the red-hot lava. 294 00:31:28,609 --> 00:31:31,909 So did millions of tons of rocks. 295 00:31:31,973 --> 00:31:35,639 And this produced a titanic explosion. 296 00:31:36,416 --> 00:31:39,371 The noise was almost certainly the loudest noise 297 00:31:39,435 --> 00:31:43,595 that has ever echoed round the earth in recorded history. 298 00:31:43,943 --> 00:31:47,640 It was heard 2,000 miles away in Australia. 299 00:31:48,185 --> 00:31:53,877 3,000 miles away on the small island of Rodriguez in the South Atlantic, 300 00:31:53,941 --> 00:32:00,485 the commander of the garrison heard it and thought it was distant gunfire at sea. 301 00:32:01,190 --> 00:32:04,840 The explosion also produced a tempest of wind, 302 00:32:04,904 --> 00:32:10,003 which swept out entirely round the globe seven and a half times 303 00:32:10,067 --> 00:32:12,279 before it finally died away. 304 00:32:13,218 --> 00:32:18,243 But most catastrophic of all, the explosion produced a tidal wave. 305 00:32:18,598 --> 00:32:21,510 It swept towards the coasts and as it approached 306 00:32:21,574 --> 00:32:25,329 it became a wall of water over 100 feet high. 307 00:32:25,741 --> 00:32:28,369 It crashed into the harbours of little villages, 308 00:32:28,433 --> 00:32:31,789 it picked up a naval gunboat with a crew of 28 309 00:32:31,853 --> 00:32:37,534 and lifted it bodily for over a mile inland and dumped it on the top of a hill. 310 00:32:37,716 --> 00:32:41,408 And it overwhelmed village after village. 311 00:32:41,472 --> 00:32:46,290 Over 36,000 people were killed. 312 00:32:47,566 --> 00:32:51,145 The pall of ash brought darkness 313 00:32:51,209 --> 00:32:55,307 over an area of 100 miles or so for several days. 314 00:32:55,752 --> 00:33:01,769 But when it cleared away, they found that the island of Krakatau was unrecognisable. 315 00:33:02,907 --> 00:33:05,872 Three-quarters of the main island had disappeared. 316 00:33:05,945 --> 00:33:10,139 The two nearby islets were buried beneath massive deposits of ash. 317 00:33:10,203 --> 00:33:15,031 And where the tallest peak had stood, the sea was 900 feet deep. 318 00:33:15,143 --> 00:33:21,606 But not for long. 44 years later another island rose from the boiling sea. 319 00:33:31,536 --> 00:33:35,544 They called it Anak Krakatau: The child of Krakatau. 320 00:33:35,657 --> 00:33:38,202 Compared with the explosions of its parent, 321 00:33:38,266 --> 00:33:41,687 its eruptions are still trivial bubblings. 322 00:34:08,430 --> 00:34:12,135 Now, after more than 50 years of fitful activity, 323 00:34:12,199 --> 00:34:16,099 Krakatau's child has built itself a new cone. 324 00:34:16,163 --> 00:34:19,743 It's still not very big, less than 1,000 feet high. 325 00:34:20,098 --> 00:34:26,099 Sporadically, it explodes. But often it's easy enough to walk round its rim. 326 00:34:36,196 --> 00:34:42,259 The fumes that boil up from its crater are partly steam and partly sulphurous gas, 327 00:34:42,327 --> 00:34:46,771 and the sulphur condenses on the rocks, coating them yellow. 328 00:34:49,001 --> 00:34:53,042 All volcanic eruptions spew out sulphur in one form or another, 329 00:34:53,106 --> 00:34:55,514 including those underwater. 330 00:34:57,631 --> 00:35:00,151 Here it doesn't form yellow crystals, 331 00:35:00,215 --> 00:35:05,198 but reacts with the sea water to produce clouds of black sulphides. 332 00:35:08,875 --> 00:35:13,094 These smokers, nearly two miles deep on the floor of the Pacific, 333 00:35:13,158 --> 00:35:17,653 are one of the most extraordinary scientific discoveries of recent years. 334 00:35:17,875 --> 00:35:22,300 The sulphides they produce are food for microscopic bacteria. 335 00:35:22,750 --> 00:35:27,521 They, in turn, are consumed by a group of creatures, quite unlike any 336 00:35:27,585 --> 00:35:30,036 that have been seen before. 337 00:35:31,650 --> 00:35:34,855 These are giant tube-worms 11 feet long. 338 00:35:34,919 --> 00:35:40,349 They have neither mouth nor gut but absorb bacteria through their thin skin. 339 00:35:42,356 --> 00:35:47,543 And these are clams, two feet across. They too consume the bacteria. 340 00:35:47,847 --> 00:35:50,935 The heated water rising above the smokers 341 00:35:50,999 --> 00:35:55,971 causes currents along the sea bottom that sweep small particles towards to the vents 342 00:35:56,035 --> 00:35:59,423 so there's a whole community of creatures feeding on them. 343 00:35:59,487 --> 00:36:05,269 Small, white, blind crabs. Strange fish, hitherto unknown. 344 00:36:07,386 --> 00:36:10,092 Until this bizarre colony was discovered, 345 00:36:10,156 --> 00:36:12,639 we had believed that all creatures on earth 346 00:36:12,703 --> 00:36:16,021 derived their energy through plants from the sun. 347 00:36:16,244 --> 00:36:22,159 Even the deep sea creatures we knew of fed on fragments falling from the sunlit surface. 348 00:36:22,223 --> 00:36:26,343 But here were animals that owed nothing to the sun 349 00:36:26,407 --> 00:36:32,351 and were sustained through bacteria by the chemical energy of volcanoes. 350 00:36:39,258 --> 00:36:43,378 But volcanoes don't remain active for ever. 351 00:36:43,464 --> 00:36:47,336 Eventually, there is some shift deep in the earth's crust 352 00:36:47,400 --> 00:36:51,254 and the focus of the intense heat moves away slightly 353 00:36:51,318 --> 00:36:53,912 and the eruptions come to an end. 354 00:36:54,172 --> 00:36:58,313 But if water should percolate down from the surface through the rocks 355 00:36:58,377 --> 00:37:01,403 and approach to the magma chamber, it's still so hot 356 00:37:01,467 --> 00:37:05,494 that the water is superheated and forced up again, 357 00:37:05,558 --> 00:37:08,480 like water in the spout of a boiling kettle. 358 00:37:09,002 --> 00:37:13,884 On the way, it may well dissolve minerals from the rocks through which it passes, 359 00:37:13,948 --> 00:37:20,362 and then, as it emerges as hot springs, the minerals will be deposited in terraces, 360 00:37:20,426 --> 00:37:23,502 like these in Rotorua, in New Zealand. 361 00:37:32,497 --> 00:37:36,107 In some parts, the superheated steam on its way to the surface 362 00:37:36,171 --> 00:37:38,976 has dissolved the softer rocks through which it is passes 363 00:37:39,040 --> 00:37:41,763 and brings them up as boiling mud. 364 00:37:48,244 --> 00:37:52,353 Elsewhere, the boiling water shoots spasmodically into huge fountains, 365 00:37:52,417 --> 00:37:55,295 and the whole area is wreathed in steam. 366 00:37:55,721 --> 00:38:00,878 Such a place is typical parts of land where volcanic fires are on the wane. 367 00:38:01,120 --> 00:38:05,066 The famous hot springs of Yellowstone in the Rocky Mountains of North America 368 00:38:05,130 --> 00:38:08,383 are also heated by a vast chamber of molten rock 369 00:38:08,447 --> 00:38:11,316 some distance down beneath the surface. 370 00:38:22,852 --> 00:38:27,059 The water welling up from these crystal-clear, chemically rich pools 371 00:38:27,123 --> 00:38:30,902 is so scaldingly hot that no creature can live in them. 372 00:38:31,206 --> 00:38:33,845 But when they trickle over the brim, they begin to cool, 373 00:38:33,909 --> 00:38:38,860 and there rich colonies of bacteria and mats of algae begin to grow. 374 00:38:39,285 --> 00:38:42,813 In places they flourish so thickly that they break the surface 375 00:38:42,877 --> 00:38:49,077 and divert the flow of water so that in parts they're cool enough to allow brine flies. 376 00:38:58,892 --> 00:39:01,373 The flies come to feed on the algae. 377 00:39:07,153 --> 00:39:09,418 And here, too, they mate. 378 00:39:24,640 --> 00:39:28,833 They lay their eggs directly in the warm mat of the algae. 379 00:39:28,897 --> 00:39:32,847 Each has a long white thread to its case, like a seed. 380 00:39:41,110 --> 00:39:43,988 The eggs, however, are far from safe. 381 00:39:44,052 --> 00:39:47,825 They're seized by mites that clamber about over the algae. 382 00:39:58,465 --> 00:40:02,438 Spiders, too, prowl around the grazing herds. 383 00:40:08,585 --> 00:40:11,862 A slightly larger fly moves among the brine flies. 384 00:40:11,926 --> 00:40:15,251 It too is a killer, devouring the grubs. 385 00:40:29,162 --> 00:40:33,758 So the algal mats support a closely-knit interdependent community, 386 00:40:33,822 --> 00:40:38,822 all nourished by chemicals in the water and energised by the volcanic heat. 387 00:40:38,974 --> 00:40:42,238 But in the end it's destroyed by its own success. 388 00:40:42,302 --> 00:40:47,195 Increasing numbers of grubs munch away the algae and begin weaken the mat. 389 00:40:47,259 --> 00:40:53,230 Eventually it gives way, the channel clears and lethal scalding water gushes down, 390 00:40:53,294 --> 00:40:58,785 killing an entire generation of grubs and many hunters and parasites that live on them. 391 00:41:02,701 --> 00:41:06,222 Now the process has to start all over again. 392 00:41:23,115 --> 00:41:26,193 The hot volcanic springs of the Rift Valley in Africa 393 00:41:26,257 --> 00:41:32,215 also support their own crops of bacteria and the small floating algae that feed on them. 394 00:41:32,481 --> 00:41:36,159 But here the creatures that come to harvest them are much bigger. 395 00:41:36,367 --> 00:41:41,495 Flamingoes, sometimes as many as a million of them on this one lake. 396 00:41:49,678 --> 00:41:53,552 These lesser flamingoes feed entirely on single-celled algae 397 00:41:53,616 --> 00:41:58,433 that proliferate in vast quantities in these steaming soda-rich waters. 398 00:41:58,555 --> 00:42:01,846 Flocks like these remove 150 tons 399 00:42:01,910 --> 00:42:05,491 of these microscopic plants from this lake every day. 400 00:42:11,651 --> 00:42:15,508 Their bills have sieves inside them which strain off the algae 401 00:42:15,572 --> 00:42:17,883 as the water passes through them. 402 00:42:22,320 --> 00:42:24,818 It's easy to see how living creatures can benefit 403 00:42:24,882 --> 00:42:30,070 from the chemical riches of volcanoes when thay dissolved in the waters of hot springs. 404 00:42:30,930 --> 00:42:34,068 It's more difficult to imagine how any living thing 405 00:42:34,132 --> 00:42:37,713 could derive nourishment from a basalt lava flow. 406 00:42:42,292 --> 00:42:46,758 Its surface in many places is as smooth and as hard as glass, 407 00:42:46,822 --> 00:42:52,136 and neither frost nor roots of plants can initially make any impression on it. 408 00:43:00,865 --> 00:43:03,267 Centuries may pass after an eruption 409 00:43:03,331 --> 00:43:08,119 before there's any sign of the surface of such a flow beginning even to weather. 410 00:43:08,219 --> 00:43:14,744 This flow for example on the flanks of Mount Kilauea in Hawaii is some 3,000 years old, 411 00:43:14,808 --> 00:43:20,678 and yet still it shows the rippled, ropy surface that formed when it was liquid. 412 00:43:20,742 --> 00:43:26,842 But in the end the surface does erode and plants do manage to get root in the cracks. 413 00:43:26,906 --> 00:43:30,452 They in turn can support all kinds of other life, 414 00:43:30,516 --> 00:43:34,036 and so the lava flow is eventually colonised, 415 00:43:34,100 --> 00:43:37,372 not only on its surface but in its depths. 416 00:43:37,436 --> 00:43:42,302 For these basaltic lava flows are often not as solid as they seem. 417 00:43:43,957 --> 00:43:47,951 When the lava first flows out of the vent like a river, 418 00:43:48,015 --> 00:43:53,058 that on the outside of the flow will cool quicker and solidify, 419 00:43:53,122 --> 00:43:56,037 forming walls on either side of the flow. 420 00:43:57,903 --> 00:44:04,168 The top too cools quicker, and that causes a crust to form over the flow, 421 00:44:04,232 --> 00:44:09,023 so that eventually the lava is flowing down a long tunnel. 422 00:44:09,871 --> 00:44:14,749 When that happens, the walls and ceiling of the tunnel act as insulation, 423 00:44:14,813 --> 00:44:18,857 keeping the heat in, so that the lava flow remains liquid 424 00:44:18,921 --> 00:44:21,952 and so continues for mile after mile. 425 00:44:27,043 --> 00:44:30,116 When eventually the supply of lava stops, 426 00:44:30,180 --> 00:44:36,699 that tunnel may drain, leaving a long cavern like this one. 427 00:45:20,317 --> 00:45:23,884 Out of the reach of rain and frost and even dust, 428 00:45:23,948 --> 00:45:27,359 the surface of the lava looks exactly as it must have done 429 00:45:27,423 --> 00:45:31,445 when the last trickle was draining away and the floor was so hot 430 00:45:31,509 --> 00:45:34,877 that anything touching it would be turned to a cinder. 431 00:45:54,760 --> 00:45:59,835 Molten lava had dripped from the ceiling, it had swilled round the sides 432 00:45:59,899 --> 00:46:04,459 and spurted out in little dribbles from cracks in the newly congealed walls. 433 00:46:04,605 --> 00:46:07,872 But living organisms have already moved in. 434 00:46:08,475 --> 00:46:14,019 These roots belong to trees that are growing on the surface of the lava flow. 435 00:46:14,083 --> 00:46:18,549 They've found their way down through the cracks, and here they dangle, 436 00:46:18,613 --> 00:46:23,020 catching water as it percolates through the lava and trickles down them. 437 00:46:23,191 --> 00:46:29,678 Among the rootlets, there are animals that live nowhere else in the world. 438 00:46:34,193 --> 00:46:37,467 Normally, these creatures are in total darkness. 439 00:46:37,636 --> 00:46:41,671 Nearly all of them, like this cricket, have lost their pigment. 440 00:46:41,892 --> 00:46:45,511 Many of them have also lost their wings and their eyes. 441 00:46:46,007 --> 00:46:49,469 In the blackness, they find their way about by touch, 442 00:46:49,601 --> 00:46:52,365 and, like many cave insects elsewhere in the world, 443 00:46:52,429 --> 00:46:56,299 have consequently developed long legs and antennae. 444 00:47:03,695 --> 00:47:06,648 Some, like this bug, are scavengers. 445 00:47:09,160 --> 00:47:12,626 Others, like the centipede, hunt. 446 00:47:18,095 --> 00:47:20,965 And the millipedes feed on the roots. 447 00:47:40,330 --> 00:47:43,721 So, in these extraordinary lava caverns, 448 00:47:43,785 --> 00:47:47,101 there is yet another community of interdependent creatures 449 00:47:47,165 --> 00:47:51,681 that have come into existence since the volcanoes erupted. 450 00:48:03,699 --> 00:48:08,412 The colonisation of volcanic ash presents different problems. 451 00:48:08,587 --> 00:48:12,069 The difficulty here is not the glassy hardness of the rock 452 00:48:12,133 --> 00:48:16,246 but quite the reverse, its insubstantial dustiness. 453 00:48:16,593 --> 00:48:20,239 Mount St Helens is still a wasteland. 454 00:48:22,004 --> 00:48:26,324 It's now, as I speak, some two and a quarter years 455 00:48:26,388 --> 00:48:28,714 since the volcano erupted. 456 00:48:29,422 --> 00:48:33,178 I'm some three miles from the crater, 457 00:48:33,242 --> 00:48:38,925 and still the scene is one of devastation and sterility. 458 00:48:38,989 --> 00:48:44,385 It's not just that this unweathered ash is not very fertile, 459 00:48:44,449 --> 00:48:49,417 but it's also so loose that it's difficult for plants to get root. 460 00:48:49,481 --> 00:48:52,964 But that possibility is always here. 461 00:48:53,256 --> 00:48:59,738 Here, for example, in this crevice, there are the seeds of the willow herb, 462 00:48:59,802 --> 00:49:03,222 or, as they call it in these parts, fireweed, 463 00:49:03,286 --> 00:49:06,985 that have been blown up from the valleys below. 464 00:49:07,049 --> 00:49:11,248 I don't suppose these particular ones will manage to get root here, 465 00:49:11,312 --> 00:49:13,819 but in the end some plant will, 466 00:49:13,883 --> 00:49:18,476 and in the end the process of colonisation will begin. 467 00:49:22,025 --> 00:49:25,199 Krakatau's child is just 57 years old. 468 00:49:25,263 --> 00:49:28,299 Its flanks too are covered for the most part with ash, 469 00:49:28,363 --> 00:49:32,267 and they're still being buried regularly with new layers from fresh eruptions, 470 00:49:32,331 --> 00:49:36,456 yet the process of colonisation is already under way. 471 00:49:37,059 --> 00:49:41,393 Not only are there giant grasses, like this wild sugar cane, 472 00:49:41,818 --> 00:49:44,487 but trees: A casuarina. 473 00:49:44,551 --> 00:49:50,175 If you want to see what a whole century of colonisation by plants can bring about, 474 00:49:50,548 --> 00:49:54,873 have a look at that fragment of old Krakatau over there. 475 00:50:04,227 --> 00:50:07,210 We know from first-hand reports that 100 years ago 476 00:50:07,274 --> 00:50:11,358 there was nothing here at all but sterile ash many feet deep. 477 00:50:11,693 --> 00:50:16,594 Within three years, 34 different species of plants had reappeared. 478 00:50:17,210 --> 00:50:20,028 Ten years later there were twice that number, 479 00:50:20,092 --> 00:50:23,588 and over 100 species of birds and insects as well. 480 00:50:24,064 --> 00:50:28,424 Some seeds must have floated here from Java, some 20 miles away, 481 00:50:28,488 --> 00:50:31,070 and they still continue to do so. 482 00:50:32,352 --> 00:50:36,052 Other smaller ones were probably carried here by birds, 483 00:50:36,116 --> 00:50:39,172 either on their feet or in their stomachs. 484 00:50:51,465 --> 00:50:56,672 But the ash is still here beneath the lattice of roots of the jungle trees. 485 00:51:01,732 --> 00:51:07,352 Somehow or other, rats and lizards and pythons have all reached here. 486 00:51:07,581 --> 00:51:11,259 There are now many hundreds of different species of plants, 487 00:51:11,344 --> 00:51:15,937 and the winds have assisted the passage of great number of flying insects, 488 00:51:16,001 --> 00:51:20,348 whose descendants now form large and permanent populations, 489 00:51:20,412 --> 00:51:23,925 pollinating the flowers, feeding on their fruits, 490 00:51:23,989 --> 00:51:28,779 collecting their rotting leaves and indeed feeding on one another. 491 00:51:48,387 --> 00:51:52,599 As yet there are no larger mammals, no monkeys or squirrels, 492 00:51:52,663 --> 00:51:57,331 no hunting cats or mongoose, as there are in Java or Sumatra. 493 00:51:57,617 --> 00:52:00,069 But as far as smaller creatures are concerned, 494 00:52:00,133 --> 00:52:03,495 the number of species is increasing all the time. 495 00:52:17,117 --> 00:52:20,465 And on the flanks of volcanoes all round the world, 496 00:52:20,529 --> 00:52:23,895 men clear fields and plant crops, 497 00:52:23,959 --> 00:52:27,637 even though they know they may be sitting on a time bomb. 498 00:52:34,720 --> 00:52:39,135 These rice fields lie on the flanks of one of Krakatau's near neighbours, 499 00:52:39,199 --> 00:52:43,841 Gunung Agung in Bali. Only 20 years ago it erupted, 500 00:52:43,905 --> 00:52:49,027 killing 2,000 people and leaving 150,000 homeless. 501 00:52:49,530 --> 00:52:53,299 But the Balinese will not leave fields that are so fertile 502 00:52:53,363 --> 00:52:58,314 they can produce two or three rich harvests of rice every year. 503 00:52:59,789 --> 00:53:05,417 Gunung Agung, Krakatau and the rest of the long line of violently explosive volcanoes 504 00:53:05,481 --> 00:53:10,826 that run in a chain along Sumatra and Java and rest of the Indonesian islands 505 00:53:10,890 --> 00:53:14,255 stand on the line of the crack in the earth's crust 506 00:53:14,319 --> 00:53:17,526 where the basalt plate forming the floor of the Indian Ocean 507 00:53:17,590 --> 00:53:21,395 meets the partly submerged edge of the continent of Asia. 508 00:53:21,507 --> 00:53:25,451 This junction already existed 65 million years ago, 509 00:53:25,515 --> 00:53:29,685 when India was an isolated island in the middle of that ocean. 510 00:53:30,182 --> 00:53:33,944 Since then, as the ocean floor has continued to spread, 511 00:53:34,008 --> 00:53:38,087 the continents have shifted and India has moved towards Asia. 512 00:53:38,393 --> 00:53:42,617 As the two continents approached, the sediments between them crumpled 513 00:53:42,681 --> 00:53:45,615 and eventually piled up over the junction, 514 00:53:45,713 --> 00:53:49,868 so instead of the line between them being marked by chain of volcanoes, 515 00:53:49,932 --> 00:53:55,439 it's buried deep beneath an immense range of mountains, the Himalaya. 516 00:53:58,065 --> 00:54:04,454 So these great peaks of sandstone and limestone rising five miles into the sky 517 00:54:04,518 --> 00:54:09,183 are not only the highest mountains in the world, but among the youngest. 518 00:54:09,247 --> 00:54:13,175 What is more, the process has not yet come to an end. 519 00:54:13,389 --> 00:54:18,049 India is still moving north at the rate of about two inches a year, 520 00:54:18,113 --> 00:54:23,614 compacting itself ever more tightly against the great continental mass of Asia, 521 00:54:24,003 --> 00:54:29,062 and the Himalaya are, infinitesimally, getting higher and higher. 522 00:54:30,216 --> 00:54:34,203 And that is how this ammonite, this sea-living creature, 523 00:54:34,267 --> 00:54:38,797 came to rest over two miles high in the Himalaya. 524 00:54:38,986 --> 00:54:42,877 That too is the explanation of how the Kali Gandaki river 525 00:54:42,941 --> 00:54:48,455 managed to cut its way clean through the highest range of mountains in the world. 526 00:54:49,315 --> 00:54:53,085 It was flowing south from the ancient plateau of Tibet 527 00:54:53,149 --> 00:54:57,536 even before the great mass of India collided with Asia. 528 00:54:58,544 --> 00:55:03,864 As the sediments between the two land masses buckled and rose over millions of years, 529 00:55:03,928 --> 00:55:06,611 the river maintained its course, 530 00:55:06,675 --> 00:55:10,666 cutting down through the rocks as swiftly as they rose. 531 00:55:11,142 --> 00:55:15,080 And so now it still flows south to the plains of India, 532 00:55:15,206 --> 00:55:19,408 and does so through the deepest gorge in the world. 533 00:55:21,241 --> 00:55:25,792 Mountain ranges have been created in this way several times during history the Earth. 534 00:55:25,856 --> 00:55:28,632 The Himalaya are just the most recent. 535 00:55:28,696 --> 00:55:32,493 As they are worn down, so they create different environments 536 00:55:32,557 --> 00:55:35,072 in which animals and plants can live. 52811

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