1 00:00:02,727 --> 00:00:09,041 Earth, a 4.5- Billion-year-old planet, still evolving. 2 00:00:10,087 --> 00:00:18,087 As continents shift and clash, volcanoes erupt, and glaciers grow and recede, 3 00:00:18,087 --> 00:00:22,447 the Earth's crust is carved in countless fascinating ways, 4 00:00:22,447 --> 00:00:26,884 leaving a trail of geological mysteries behind. 5 00:00:27,927 --> 00:00:33,923 And one of the greatest is right here, at Yellowstone National Park in Wyoming. 6 00:00:36,007 --> 00:00:40,367 This is one of the world's most geologically active places, 7 00:00:40,367 --> 00:00:44,247 shaken by up to 5,000 earthquakes every year, 8 00:00:44,247 --> 00:00:48,847 and with more geysers and hot springs than in the rest of the world combined. 9 00:00:48,847 --> 00:00:53,167 Why is Yellowstone so active? How did it form? 10 00:00:53,167 --> 00:00:57,399 And why here in the heart of the Rockies? 11 00:00:58,407 --> 00:01:02,527 Scientists studying Yellowstone are uncovering a violent past. 12 00:01:02,527 --> 00:01:09,087 Carved by water, crushed by ancient glaciers and blasted 13 00:01:09,087 --> 00:01:13,478 by the biggest volcanic eruptions ever known on the planet. 14 00:01:20,767 --> 00:01:26,080 And even today, Yellowstone is one of the most dangerous places on Earth. 15 00:01:36,007 --> 00:01:40,007 Yellowstone National Park is one of the most amazing places on Earth, 16 00:01:40,007 --> 00:01:41,565 and it's unique. 17 00:01:43,847 --> 00:01:47,007 It contains some of America's most stunning scenery 18 00:01:47,007 --> 00:01:52,479 and wildlife that attracts three million tourists a year. 19 00:01:53,607 --> 00:01:59,567 To understand where Yellowstone came from, and why it is so active today, 20 00:01:59,567 --> 00:02:02,927 we need to take a journey back into the distant past 21 00:02:02,927 --> 00:02:07,682 of the North American continent and deep into the Earth's interior. 22 00:02:09,447 --> 00:02:14,167 Yellowstone sits 8,000 feet up on a remote mountain plateau, 23 00:02:14,167 --> 00:02:19,719 primarily within Wyoming, but stretching into parts of Idaho and Montana. 24 00:02:21,287 --> 00:02:28,367 The park covers 3,468 square miles, 63 miles north to south 25 00:02:28,367 --> 00:02:31,086 and 54 miles east to west. 26 00:02:33,567 --> 00:02:36,767 And it's on top of one of the world's most unusual 27 00:02:36,767 --> 00:02:39,076 and deadliest geological structures. 28 00:02:40,727 --> 00:02:46,847 What's unusual about the park? Are the wildlife unusual? No. 29 00:02:46,847 --> 00:02:50,607 Is the wide open space unusual? No. 30 00:02:50,607 --> 00:02:53,407 You've got it all over the western US. 31 00:02:53,407 --> 00:02:54,887 What's unusual? 32 00:02:54,887 --> 00:02:59,642 It's a very unusual geology that created the park. 33 00:03:01,007 --> 00:03:05,847 Yellowstone was founded as the world's first National Park 34 00:03:05,847 --> 00:03:08,725 because of the geology. 35 00:03:09,727 --> 00:03:15,247 It's this strange geology that attracts teams of scientists to the park. 36 00:03:15,247 --> 00:03:19,767 Their task, to piece together the story of the incredible processes 37 00:03:19,767 --> 00:03:23,607 that built this unique, extraordinary landscape 38 00:03:23,607 --> 00:03:26,565 by digging deep into Yellowstone's past. 39 00:03:27,927 --> 00:03:34,087 The geologic history of Yellowstone goes back to the formation 40 00:03:34,087 --> 00:03:36,007 of the North American continent. 41 00:03:36,007 --> 00:03:43,487 Some of the rocks in Yellowstone are 2.8 to 3.2 billion year old rocks, 42 00:03:43,487 --> 00:03:45,921 some of the oldest in North America. 43 00:03:46,927 --> 00:03:49,207 Only by travelling back into the past 44 00:03:49,207 --> 00:03:52,847 can we figure out why in this particular location 45 00:03:52,847 --> 00:03:59,036 there are 2,400 miles of rivers, more than 300 waterfalls... 46 00:04:01,007 --> 00:04:06,127 ...and the world's greatest concentration of 10,000 hot water springs, 47 00:04:06,127 --> 00:04:11,287 bubbling mud-holes, gas vents and geysers. 48 00:04:11,287 --> 00:04:17,396 What do these features reveal about this landscape, and how it was formed? 49 00:04:23,127 --> 00:04:26,207 The investigation begins at Yellowstone's star attraction, 50 00:04:26,207 --> 00:04:28,323 Old Faithful. 51 00:04:30,327 --> 00:04:35,196 It's a key clue to what's going on underneath the surface. 52 00:04:39,487 --> 00:04:41,727 Located in the southwest of Yellowstone Park, 53 00:04:41,727 --> 00:04:47,167 the geyser puts on an explosive display every 90 minutes or so, 54 00:04:47,167 --> 00:04:52,605 blasting out thousands of gallons of scalding hot water. 55 00:04:56,887 --> 00:04:58,887 Yellowstone is like no other place on Earth, 56 00:04:58,887 --> 00:05:00,967 there is so much heat coming out here. 57 00:05:00,967 --> 00:05:03,435 It's really a singular phenomenon. 58 00:05:05,487 --> 00:05:09,247 Well, after about a 90-minute nap, Old Faithful has roared back to life. 59 00:05:09,247 --> 00:05:11,647 It wasn't actually napping, it was recharging, 60 00:05:11,647 --> 00:05:15,247 and the temperature of the water was increasing, the system was pressurising. 61 00:05:15,247 --> 00:05:18,087 Beneath Old Faithful is a rather complex plumbing system, 62 00:05:18,087 --> 00:05:21,682 filled with caverns and conduits and constrictions. 63 00:05:23,127 --> 00:05:26,047 Rainwater saturating the ground around the geyser 64 00:05:26,047 --> 00:05:30,327 slowly fills its underground reservoir. 65 00:05:30,327 --> 00:05:35,687 Hot rocks below ground heat the water under pressure for around 90 minutes. 66 00:05:35,687 --> 00:05:41,847 Suddenly, some water spurts through a tiny, five-inch wide crack in the rocks. 67 00:05:41,847 --> 00:05:46,007 This causes a drop in the pressure within the water chamber. 68 00:05:46,007 --> 00:05:49,967 In an instant, thousands of gallons of water are turned to steam 69 00:05:49,967 --> 00:05:53,164 and blasted up into the air. 70 00:05:57,567 --> 00:06:01,127 When the pressure builds up enough, steam bubbles start rising to the surface, 71 00:06:01,127 --> 00:06:04,327 the system depressurises, and a full eruption can occur. 72 00:06:04,327 --> 00:06:09,640 Old Faithful shows that rocks below the surface are very hot. 73 00:06:17,647 --> 00:06:23,207 Scientists find clues to a violent past 34 miles southeast of the hot springs, 74 00:06:23,207 --> 00:06:27,485 on the shores of a circular lake called Indian Ponds. 75 00:06:29,567 --> 00:06:31,047 As a field geologist, 76 00:06:31,047 --> 00:06:35,007 my job is to basically be a rock detective. 77 00:06:35,007 --> 00:06:37,527 And so I try to determine what their origin is 78 00:06:37,527 --> 00:06:41,087 and what the history is of that particular rock. 79 00:06:41,087 --> 00:06:42,487 There we go. 80 00:06:42,487 --> 00:06:47,287 OK, now, in this particular case... Let's look at this. 81 00:06:47,287 --> 00:06:52,367 This rock, when it started, it was just a loose sand, 82 00:06:52,367 --> 00:06:55,487 you could just put your fingers through it. 83 00:06:55,487 --> 00:07:00,880 The solid boulder is formed from millions of individual grains of sand. 84 00:07:02,367 --> 00:07:06,087 Microscopic analysis reveals the grains have been cemented together 85 00:07:06,087 --> 00:07:09,841 by chemicals and pressure deep under the ground. 86 00:07:11,687 --> 00:07:15,805 But how did the rock get to the surface? 87 00:07:16,807 --> 00:07:20,927 Morgan has chemically dated the rocks and discovered that 3,000 years ago, 88 00:07:20,927 --> 00:07:24,327 the boulder was blasted out of the ground by the hot water explosion 89 00:07:24,327 --> 00:07:26,761 of a gigantic geyser. 90 00:07:28,247 --> 00:07:34,727 You would see boiling water, rock fragments and fine muddy material 91 00:07:34,727 --> 00:07:41,287 being ejected up into the air as high as 3 to 5,000 feet. 92 00:07:41,287 --> 00:07:43,047 And then, at some point, 93 00:07:43,047 --> 00:07:49,127 material would start raining down from this explosion column. 94 00:07:49,127 --> 00:07:52,836 Now, you wouldn't want to be standing next to one of those. 95 00:07:54,687 --> 00:07:58,726 Indian Ponds is the crater that the geyser left behind. 96 00:08:04,527 --> 00:08:07,527 But it is dwarfed by the crater Morgan has found 97 00:08:07,527 --> 00:08:09,916 at Mary Bay in Yellowstone Lake. 98 00:08:12,687 --> 00:08:17,447 Morgan has dated this geyser explosion to 13,000 years ago. 99 00:08:17,447 --> 00:08:20,967 So here we are in the middle of Yellowstone Lake, 100 00:08:20,967 --> 00:08:25,407 and it's, as you can see, a beautiful day and it's nice and placid, 101 00:08:25,407 --> 00:08:29,446 but on the floor of Yellowstone Lake, it's anything but quiet. 102 00:08:30,647 --> 00:08:34,607 Morgan's research proves that geysers were exploding around the lake, 103 00:08:34,607 --> 00:08:40,367 and even under the water, between 13,000 and 3,000 years ago. 104 00:08:40,367 --> 00:08:45,247 And their size suggests that whatever was powering them was huge. 105 00:08:45,247 --> 00:08:47,681 But is it still active today? 106 00:08:49,567 --> 00:08:52,957 A clue comes from underwater vents at the bottom of the geyser crater. 107 00:08:55,367 --> 00:08:59,201 They pump out vast quantities of hot water and gases. 108 00:09:04,487 --> 00:09:07,007 To find out what's creating the gases, 109 00:09:07,007 --> 00:09:10,487 Jake Lowenstern and his assistant collect samples from the hot springs 110 00:09:10,487 --> 00:09:13,160 in the centre of the park. 111 00:09:14,887 --> 00:09:17,887 The funnel they use is designed to collect up gas bubbles 112 00:09:17,887 --> 00:09:20,047 before they reach the surface, 113 00:09:20,047 --> 00:09:23,927 so that they're not contaminated by ordinary air. 114 00:09:23,927 --> 00:09:28,127 So we let it sit for five minutes and let the oxygen get out? 115 00:09:28,127 --> 00:09:29,447 Yeah. 116 00:09:29,447 --> 00:09:33,687 It is a very complex mix of gases and... but we have a... a lot of tools 117 00:09:33,687 --> 00:09:38,447 that we can use to try to unravel this rather, uh, complicated information. 118 00:09:38,447 --> 00:09:41,487 So we'll look at all of the gases that are coming out, 119 00:09:41,487 --> 00:09:44,687 we can learn about the different kinds of rocks beneath Yellowstone 120 00:09:44,687 --> 00:09:48,807 and try to understand how things might be changing from... from week to week, 121 00:09:48,807 --> 00:09:52,447 or year to year or... or decade to decade. 122 00:09:52,447 --> 00:09:54,767 Analysis of the gases reveals 123 00:09:54,767 --> 00:10:00,887 that they are a mix of carbon dioxide, sulphur dioxide and hydrogen sulphide. 124 00:10:00,887 --> 00:10:05,244 It is the same mix that is found coming out of volcanoes. 125 00:10:07,887 --> 00:10:11,127 But the final clue to what's actually going on underground 126 00:10:11,127 --> 00:10:14,164 is found on the edge of the same hot springs. 127 00:10:15,927 --> 00:10:19,287 So these are quartz crystals that we collected on the side of the pool there. 128 00:10:19,287 --> 00:10:20,847 This stuff is what remains. 129 00:10:20,847 --> 00:10:24,487 It gets tossed up, and forms a little burr around the side of the pool 130 00:10:24,487 --> 00:10:26,727 and it's all beautiful little quartz crystals. 131 00:10:26,727 --> 00:10:30,087 Some of them have a little bit of iron staining and other things, um, 132 00:10:30,087 --> 00:10:35,115 but most... most of them are... are nice, uh, shades of yellow and... and clear. 133 00:10:36,247 --> 00:10:39,527 Quartz crystals like these can only have formed as a hot, 134 00:10:39,527 --> 00:10:43,927 molten rock lava flow slowly cooled after being erupted onto the surface 135 00:10:43,927 --> 00:10:46,157 from deep underground. 136 00:10:47,247 --> 00:10:53,004 So the crystals are clear evidence that under the springs is a volcano. 137 00:10:57,007 --> 00:11:01,847 Yellowstone's hot water features all point to one conclusion. 138 00:11:01,847 --> 00:11:05,760 Yellowstone must be powered by the heat of a volcano. 139 00:11:07,007 --> 00:11:11,327 Geysers only erupt if the rocks are hot enough to turn water into steam. 140 00:11:11,327 --> 00:11:16,847 Gases from underwater have the same composition as those from volcanoes. 141 00:11:16,847 --> 00:11:22,647 Quartz in the hot springs must have come from volcanic lava. 142 00:11:22,647 --> 00:11:25,967 There is an immense amount of energy coming out of the ground 143 00:11:25,967 --> 00:11:29,767 that's expressed by the geysers, 144 00:11:29,767 --> 00:11:32,767 the mud pots, the hot springs and the steam vents. 145 00:11:32,767 --> 00:11:34,447 Where's all that heat coming from? 146 00:11:34,447 --> 00:11:39,521 It's coming from the molten rock associated with the Yellowstone volcano. 147 00:11:40,567 --> 00:11:43,527 But that leaves a big question unanswered. 148 00:11:43,527 --> 00:11:48,840 In this gentle rolling landscape, where's the volcano? 149 00:11:59,687 --> 00:12:05,087 Yellowstone's unique volcanic geology is potentially deadly dangerous. 150 00:12:05,087 --> 00:12:10,127 It makes it crucial to monitor what's happening under the ground. 151 00:12:10,127 --> 00:12:13,927 The Yellowstone volcano is a very, very active volcanic system, 152 00:12:13,927 --> 00:12:18,327 and so it really requires observation. 153 00:12:18,327 --> 00:12:21,407 Everything that we do here has a research component, 154 00:12:21,407 --> 00:12:24,487 but it also has a volcano monitoring component 155 00:12:24,487 --> 00:12:28,087 and, uh, you know, if... if... if activity picks up here, 156 00:12:28,087 --> 00:12:30,727 we're going to want to know something about the plumbing system 157 00:12:30,727 --> 00:12:32,206 beneath us here. 158 00:12:33,487 --> 00:12:38,367 To try and predict when Yellowstone's hidden volcano will erupt in the future, 159 00:12:38,367 --> 00:12:42,326 scientists study its geological past. 160 00:12:43,407 --> 00:12:49,207 Part of our task is to look at the landscape and read the geologic story, 161 00:12:49,207 --> 00:12:54,247 and there are so many clues and so much evidence here to look at 162 00:12:54,247 --> 00:12:57,045 that it's a fascinating place to work. 163 00:13:00,407 --> 00:13:03,287 Scientists began investigating Yellowstone 164 00:13:03,287 --> 00:13:08,727 even before it became the world's first national park in 1872. 165 00:13:08,727 --> 00:13:14,404 But observations of this astonishing land began long before that. 166 00:13:19,887 --> 00:13:21,567 Dating ancient arrowheads shows 167 00:13:21,567 --> 00:13:26,038 that Native Americans first lived here 11,000 years ago. 168 00:13:28,447 --> 00:13:32,167 Their legends of Yellowstone's angry spirits who made the ground tremble 169 00:13:32,167 --> 00:13:37,036 were passed on to early explorers such as Lewis and Clark. 170 00:13:38,927 --> 00:13:40,447 Later reports from trappers, 171 00:13:40,447 --> 00:13:44,167 explorers and mountain men like John Colter and Jim Bridger 172 00:13:44,167 --> 00:13:48,007 told of geysers that fired 70 feet into the air 173 00:13:48,007 --> 00:13:52,159 and springs so hot that meat was readily cooked in them. 174 00:13:54,327 --> 00:13:58,327 But these were thought to be tall tales until the 1860s, 175 00:13:58,327 --> 00:14:02,727 when geologists investigated and found that the lava flows and hot vents 176 00:14:02,727 --> 00:14:06,003 were signs of volcanic activity. 177 00:14:13,767 --> 00:14:15,967 But something clearly wasn't right. 178 00:14:15,967 --> 00:14:19,846 Nobody could actually find the Yellowstone volcano. 179 00:14:21,647 --> 00:14:26,367 We say that Yellowstone is one of the world's most active volcanoes. 180 00:14:26,367 --> 00:14:29,087 People come out here, visitors, other scientists, 181 00:14:29,087 --> 00:14:30,967 and they say, "What do you mean? 182 00:14:30,967 --> 00:14:38,967 "I... I don't see a smoking volcano, I don't see a big steep volcanic, uh, uh, crater," 183 00:14:38,967 --> 00:14:42,357 all the things that one normally thinks of for an active volcano. 184 00:14:43,847 --> 00:14:49,160 So, without obvious signs of a volcano, scientists hunted for other clues. 185 00:14:51,807 --> 00:14:56,487 They would find them in the sweeping forests of Lodge Pole pines. 186 00:14:56,487 --> 00:14:59,767 These are the only plants that thrive on the poor soil 187 00:14:59,767 --> 00:15:04,477 that comes from a particular type of lava called rhyolite. 188 00:15:08,127 --> 00:15:11,927 And Yellowstone's constant plagues of mosquitoes also reveal 189 00:15:11,927 --> 00:15:14,487 the presence of that same rhyolite lava. 190 00:15:17,407 --> 00:15:23,447 The rhyolites are... are not very permeable, and so in... it creates 191 00:15:23,447 --> 00:15:27,527 these little ponds of water that never go away, 192 00:15:27,527 --> 00:15:32,967 and those are wonderful breeding grounds for mosquitoes. 193 00:15:32,967 --> 00:15:37,087 There are a lot of mosquitoes, if you can't see them, flying around my head. 194 00:15:37,087 --> 00:15:40,447 So the pine trees and the insects both indicate 195 00:15:40,447 --> 00:15:42,836 that there's a lot of rhyolite in Yellowstone. 196 00:15:44,127 --> 00:15:45,887 And that's important, 197 00:15:45,887 --> 00:15:51,200 because rhyolite lava creates incredibly violent volcanic eruptions. 198 00:15:52,647 --> 00:15:55,727 It's much more like a bread dough. 199 00:15:55,727 --> 00:15:59,567 It's about a thousand to a million times thicker or more viscous. 200 00:15:59,567 --> 00:16:04,447 If we put a bunch of gas in it, we can have a very explosive eruption. 201 00:16:04,447 --> 00:16:11,159 But if rhyolite lava is that explosive, how big a bang did it produce? 202 00:16:24,087 --> 00:16:28,927 To find that out, scientists looked, not inside Yellowstone Park, 203 00:16:28,927 --> 00:16:31,521 but in a faraway river valley at Meadow Creek, Wyoming. 204 00:16:36,767 --> 00:16:39,287 Cutting down through the land over millions of years, 205 00:16:39,287 --> 00:16:44,839 the river has exposed an unusual, thin layer of black rock in the cliff face. 206 00:16:47,727 --> 00:16:52,517 A nearby road cutting lets investigators examine the mysterious, dark rock. 207 00:16:58,687 --> 00:17:01,447 If you look at this sample, um, in detail up close, 208 00:17:01,447 --> 00:17:04,167 you can see that here's a pumice fragment, 209 00:17:04,167 --> 00:17:08,887 these... these red fragments here are... are little rock fragments, 210 00:17:08,887 --> 00:17:11,007 and, uh, if we were to make 211 00:17:11,007 --> 00:17:13,647 a thin section of this rock and look at it under the microscope, 212 00:17:13,647 --> 00:17:15,127 you would in fact see 213 00:17:15,127 --> 00:17:17,846 compressed, uh, glass shards. 214 00:17:19,647 --> 00:17:24,562 The black layer that geologists call obsidian is actually a type of glass. 215 00:17:26,167 --> 00:17:30,558 It's crucial evidence that the rocks and soil here came out of a volcano. 216 00:17:34,087 --> 00:17:37,207 Because obsidian is forged when boiling hot ash and gas 217 00:17:37,207 --> 00:17:40,722 rapidly cool under great pressure. 218 00:17:43,047 --> 00:17:44,887 And that's just what happens 219 00:17:44,887 --> 00:17:48,084 when hot volcanic clouds roll out across the landscape. 220 00:17:49,687 --> 00:17:54,407 The obsidian forms in the very bottom layers, cooled from below 221 00:17:54,407 --> 00:17:57,877 and crushed by the weight of hot debris on top. 222 00:18:00,887 --> 00:18:06,041 The ash layer that crushed the obsidian at Meadow Creek is still visible today. 223 00:18:07,167 --> 00:18:10,247 Its base is characterised by this very thick, dense, obsidian 224 00:18:10,247 --> 00:18:14,047 as... as the flow came to rest and was compacted. 225 00:18:14,047 --> 00:18:17,527 And then, above this dense glass layer as it grades upwards 226 00:18:17,527 --> 00:18:22,127 into a tan sort of region and continues up for about an additional 30 feet. 227 00:18:22,127 --> 00:18:24,847 And then up on top of that, as it's exposed today, 228 00:18:24,847 --> 00:18:27,647 modern soil has formed and we can see growing up there 229 00:18:27,647 --> 00:18:31,481 various sorts of vegetation, trees and grasses and things of that sort. 230 00:18:32,967 --> 00:18:35,247 Studying the mineral composition of the ash 231 00:18:35,247 --> 00:18:40,401 proved that it came from an ancient volcanic blast in Yellowstone Park. 232 00:18:42,087 --> 00:18:45,567 And there's only one way that so much ash could have been blasted 233 00:18:45,567 --> 00:18:48,400 so very far away from its source. 234 00:18:49,407 --> 00:18:52,967 The eruption must have been larger, far larger, 235 00:18:52,967 --> 00:18:56,327 than anything ever seen by man. 236 00:18:56,327 --> 00:19:01,765 So big that scientists now label it as a supereruption. 237 00:19:02,767 --> 00:19:05,327 We're looking at this deposit from a supereruption, 238 00:19:05,327 --> 00:19:09,286 and yet we're over 50 miles from the source of the... of the eruption. 239 00:19:12,727 --> 00:19:15,527 The geologists have recreated what must have happened here 240 00:19:15,527 --> 00:19:18,767 on the day that Yellowstone exploded. 241 00:19:18,767 --> 00:19:24,205 Incandescent avalanches of ash raced out of the park in all directions. 242 00:19:25,567 --> 00:19:28,967 CATHEY: So this is travelling at very high velocity, um, 243 00:19:28,967 --> 00:19:31,167 easily over 100 miles per hour, 244 00:19:31,167 --> 00:19:35,487 across the land surface and obliterating everything in its path. 245 00:19:35,487 --> 00:19:37,887 NASH: It was extremely hot when it arrived here, 246 00:19:37,887 --> 00:19:42,607 and... perhaps as hot as... as 1,500 degrees Fahrenheit, two... 247 00:19:42,607 --> 00:19:45,167 ...twice a pizza oven, I mean, it's just very hot. 248 00:19:46,207 --> 00:19:49,167 So what would it have been like to be standing on this spot 249 00:19:49,167 --> 00:19:51,687 hundreds of thousands of years ago, 250 00:19:51,687 --> 00:19:56,317 on the day when the Yellowstone ash cloud roared over the horizon? 251 00:19:57,567 --> 00:20:01,607 The... the impact of this would... would be, uh, absolutely unimaginable. 252 00:20:01,607 --> 00:20:03,087 It would be... CATHEY: Yeah. 253 00:20:03,087 --> 00:20:06,767 I think you would be disarticulated, burned and... and unrecognisable, 254 00:20:06,767 --> 00:20:09,201 and it would be very difficult to find any of you. 255 00:20:13,367 --> 00:20:16,367 All of the evidence about the size of the supereruption 256 00:20:16,367 --> 00:20:20,007 helped solve the mystery of the missing volcano. 257 00:20:20,007 --> 00:20:24,327 Scientists realised that the supereruption was so enormous 258 00:20:24,327 --> 00:20:27,687 that it must have blown the volcano to pieces. 259 00:20:27,687 --> 00:20:31,077 (ROARING AND EXPLOSIONS) 260 00:20:33,327 --> 00:20:37,007 Swarms of mosquitoes show that explosive rhyolite lava 261 00:20:37,007 --> 00:20:39,607 underlies parts of the park. 262 00:20:39,607 --> 00:20:43,647 Obsidian glass 60 miles away reveals that ash flows spread 263 00:20:43,647 --> 00:20:46,647 for miles around Yellowstone. 264 00:20:46,647 --> 00:20:50,687 And thick layers of debris confirm how gigantic an explosion 265 00:20:50,687 --> 00:20:52,166 this must have been. 266 00:20:53,887 --> 00:20:59,207 The problem now is the explosive legacy that the supervolcano left behind. 267 00:20:59,207 --> 00:21:05,157 Because a deadly danger still lurks here, hidden deep under the ground. 268 00:21:11,127 --> 00:21:15,287 For nearly a century after Yellowstone National Park was established, 269 00:21:15,287 --> 00:21:18,757 nobody realised one astonishing fact. 270 00:21:20,407 --> 00:21:26,721 That the park is located inside one of the biggest volcano craters on Earth. 271 00:21:28,287 --> 00:21:30,407 It wasn't until the late 1960s 272 00:21:30,407 --> 00:21:33,927 that American geophysicist Robert Christiansen realised 273 00:21:33,927 --> 00:21:37,807 that rock formations he had been studying for several years 274 00:21:37,807 --> 00:21:44,155 all around the edges of the park in fact formed a giant circular ridge. 275 00:21:45,687 --> 00:21:49,887 He compared his findings on the ground with a series of NASA pictures 276 00:21:49,887 --> 00:21:53,567 taken between 1966 and 1970, 277 00:21:53,567 --> 00:22:02,123 confirming that the ring was the rim of a giant crater, 45 miles across. 278 00:22:03,727 --> 00:22:07,727 Parts of the crater rim are still clearly visible today, 279 00:22:07,727 --> 00:22:11,356 but the other edge is almost out of sight. 280 00:22:16,727 --> 00:22:20,567 Finding the crater coincided with another scientific discovery 281 00:22:20,567 --> 00:22:23,365 in a totally different part of the country. 282 00:22:25,887 --> 00:22:30,607 In California, scientists identified a strange, thin layer of ash 283 00:22:30,607 --> 00:22:34,567 buried underneath the modern-day soil. 284 00:22:34,567 --> 00:22:38,367 The ash matched material from the Yellowstone crater. 285 00:22:38,367 --> 00:22:45,247 Dating the soil layers proved that the ash arrived 640,000 years ago. 286 00:22:45,247 --> 00:22:50,640 Scientists at last had a date for the Yellowstone supereruption. 287 00:22:56,687 --> 00:23:00,047 Ash was later found all over the western US, 288 00:23:00,047 --> 00:23:03,403 confirming the huge size of the eruption. 289 00:23:05,367 --> 00:23:09,127 At least 80 times the size of the 1883 explosion 290 00:23:09,127 --> 00:23:12,836 that destroyed the island of Krakatoa. 291 00:23:21,087 --> 00:23:27,640 And 2,500 times bigger than the 1980 eruption of Mount St Helens. 292 00:23:31,047 --> 00:23:34,527 The almost unimaginable size of the Yellowstone blast 293 00:23:34,527 --> 00:23:38,759 means that scientists now call it a supervolcano. 294 00:23:43,807 --> 00:23:46,047 But that creates another mystery. 295 00:23:46,047 --> 00:23:48,167 In this peaceful landscape, 296 00:23:48,167 --> 00:23:54,487 where is the steaming hot crater that the volcano must have left behind? 297 00:23:54,487 --> 00:23:57,687 Today, when you're looking out across the landscape, 298 00:23:57,687 --> 00:24:01,327 you see rolling hills and... and trees, 299 00:24:01,327 --> 00:24:04,487 so, obviously, there's not a big hole left in the ground, 300 00:24:04,487 --> 00:24:07,607 um, from the eruption of the... of the Yellowstone volcano. 301 00:24:07,607 --> 00:24:10,247 So something else has happened. 302 00:24:10,247 --> 00:24:15,767 One of the first processes was infilling with all sorts of volcanic lava flows, 303 00:24:15,767 --> 00:24:18,767 and if you look just down from the landscape toward those trees, 304 00:24:18,767 --> 00:24:23,207 you'll see one of the oldest lava flows that happened 305 00:24:23,207 --> 00:24:26,279 after the 640,000-year eruption. 306 00:24:27,287 --> 00:24:31,127 Over hundreds of thousands of years this flow has weathered into soil 307 00:24:31,127 --> 00:24:33,960 and been covered with trees. 308 00:24:36,287 --> 00:24:40,447 But elsewhere in the park are a different type of lava deposit, 309 00:24:40,447 --> 00:24:44,807 still bare of vegetation because this lava was still erupting 310 00:24:44,807 --> 00:24:47,480 up until about 100,000 years ago. 311 00:24:49,287 --> 00:24:55,522 The later lava was far less explosive and more runny, and cooled slowly. 312 00:24:57,367 --> 00:25:00,287 It smoothed the harsh, volcanic landscape 313 00:25:00,287 --> 00:25:03,643 into Yellowstone's softer countryside. 314 00:25:09,447 --> 00:25:13,486 That made Yellowstone, at first, more tranquil. 315 00:25:16,287 --> 00:25:20,447 But there's evidence here that the land was soon buried once again, 316 00:25:20,447 --> 00:25:24,201 this time by freezing snow and ice. 317 00:25:25,687 --> 00:25:28,997 The ice that polished the rocks has a story to tell. 318 00:25:30,767 --> 00:25:36,399 It offers crucial evidence about volcanic forces still shaping the park to this day. 319 00:25:40,327 --> 00:25:43,524 Its tale unfolds through the tiniest of clues. 320 00:25:44,887 --> 00:25:48,926 Scratches on the rocks reveal which way the ice was moving. 321 00:25:51,207 --> 00:25:54,367 They show that glaciers always slid the same way, 322 00:25:54,367 --> 00:25:59,600 outwards and downwards from an icecap at the heart of the park. 323 00:26:01,527 --> 00:26:05,887 The only conclusion is that something pushed up Yellowstone Park 324 00:26:05,887 --> 00:26:10,756 so much higher than the surrounding hills that glaciers formed on the top. 325 00:26:22,327 --> 00:26:25,407 But what force could possibly be powerful enough 326 00:26:25,407 --> 00:26:28,877 to have raised Yellowstone's peaks up into the air? 327 00:26:39,247 --> 00:26:41,447 The first clue to help answer that question 328 00:26:41,447 --> 00:26:44,767 comes from Yellowstone's numerous earthquakes. 329 00:26:44,767 --> 00:26:50,127 When the ground deforms, it creaks and groans like a Stradivarius violin. 330 00:26:50,127 --> 00:26:52,038 And the creaks and groans are essentially earthquakes. 331 00:26:53,167 --> 00:26:56,204 The quakes are recorded by seismometers all over the park. 332 00:26:58,927 --> 00:27:01,567 The earthquake monitoring is a critical part of the picture 333 00:27:01,567 --> 00:27:06,447 because it's basically... it's the stethoscope that we have to really see 334 00:27:06,447 --> 00:27:09,405 and sense the... the heartbeat of the system. 335 00:27:15,847 --> 00:27:20,125 Smith is investigating a puzzling geological mystery. 336 00:27:22,807 --> 00:27:25,887 Yellowstone has up to 5,000 earthquakes a year, 337 00:27:25,887 --> 00:27:31,166 even though it's in the stable heart of the North American continent. 338 00:27:32,367 --> 00:27:35,647 Scientists needed to know what was happening underground 339 00:27:35,647 --> 00:27:37,842 to shake the park so much. 340 00:27:39,807 --> 00:27:44,247 To find out, they plotted the precise locations and depths of earthquakes 341 00:27:44,247 --> 00:27:45,885 under the ground. 342 00:27:51,447 --> 00:27:54,041 So, why are there so many quakes? 343 00:27:58,647 --> 00:28:01,287 The answer had to wait until the mid-1980s, 344 00:28:01,287 --> 00:28:06,680 when ever more powerful computers first let scientists see into the Earth. 345 00:28:07,687 --> 00:28:11,847 Seismic waves spreading out from earthquakes travel rapidly 346 00:28:11,847 --> 00:28:16,727 through cold rock, but slow down when the rocks are hot. 347 00:28:16,727 --> 00:28:20,207 The varying wave speeds can be translated by computers 348 00:28:20,207 --> 00:28:26,407 into colour 3D images, revealing exactly where hot rock lies under the ground. 349 00:28:26,407 --> 00:28:28,327 Seismic waves propagate through the Earth 350 00:28:28,327 --> 00:28:31,127 just like X-rays go through a body, 351 00:28:31,127 --> 00:28:36,727 and so we use the same physics to reconstruct the structure of the geol... 352 00:28:36,727 --> 00:28:38,247 ...of the Earth beneath us. 353 00:28:38,247 --> 00:28:42,567 The seismic waves have outlined the park's underground structures, 354 00:28:42,567 --> 00:28:46,321 revealing a graphic history of what's happened under Yellowstone. 355 00:28:48,327 --> 00:28:51,727 They reveal this gigantic reservoir of molten rock 356 00:28:51,727 --> 00:28:55,007 which created Yellowstone's crater when lava erupted out, 357 00:28:55,007 --> 00:29:00,286 and the ground above collapsed into the space left behind. 358 00:29:01,967 --> 00:29:05,807 And the seismic waves still slow down under Yellowstone today, 359 00:29:05,807 --> 00:29:10,167 showing that the magma chamber still lurks under the park. 360 00:29:10,167 --> 00:29:16,047 It's more than 30 miles long, 25 miles wide and ten miles in depth. 361 00:29:16,047 --> 00:29:21,087 But its size alters from year to year as it fills or empties 362 00:29:21,087 --> 00:29:25,647 with semi-liquid rock at an incredible 1,500 degrees Fahrenheit. 363 00:29:25,647 --> 00:29:29,567 This is the hidden, beating heart of Yellowstone Park. 364 00:29:29,567 --> 00:29:32,207 The way it moves deforms the ground above, 365 00:29:32,207 --> 00:29:36,727 explaining the fault lines and the earthquakes they produce. 366 00:29:36,727 --> 00:29:39,207 And its heat ultimately powers 367 00:29:39,207 --> 00:29:43,086 all of Yellowstone's hot water pools and geysers. 368 00:29:48,807 --> 00:29:52,687 Subterranean Yellowstone is giving up its secrets. 369 00:29:52,687 --> 00:29:57,407 Seismographs record thousands of earthquakes in the park. 370 00:29:57,407 --> 00:29:59,847 And the evidence of earthquake waves 371 00:29:59,847 --> 00:30:04,477 reveals a massive magma chamber miles under Yellowstone's surface. 372 00:30:05,727 --> 00:30:09,807 But the Yellowstone investigation is far from finished, 373 00:30:09,807 --> 00:30:15,127 because there's evidence of another, even more monstrous sized structure 374 00:30:15,127 --> 00:30:17,800 under the park. 375 00:30:24,607 --> 00:30:27,287 By the beginning of the 21 st century, 376 00:30:27,287 --> 00:30:30,127 scientists investigating how Yellowstone was made 377 00:30:30,127 --> 00:30:33,517 had images of what lay under the park. 378 00:30:34,527 --> 00:30:36,807 But there was a problem. 379 00:30:36,807 --> 00:30:41,127 Technology only allowed a view of a few miles below the surface. 380 00:30:41,127 --> 00:30:46,407 Then, as more and more data was fed into more and more powerful computers, 381 00:30:46,407 --> 00:30:49,001 there was a breakthrough. 382 00:30:50,047 --> 00:30:55,527 In April 2006, geologists published new diagrams of hot structures, 383 00:30:55,527 --> 00:30:57,687 far deeper under the park 384 00:30:57,687 --> 00:31:02,327 and computers painted more detailed pictures. 385 00:31:02,327 --> 00:31:04,443 The results were startling. 386 00:31:07,127 --> 00:31:09,647 Investigators saw for the first time 387 00:31:09,647 --> 00:31:13,765 the sleeping monster that lies below Yellowstone Park. 388 00:31:17,367 --> 00:31:20,807 Snaking down hundreds of miles into the Earth, 389 00:31:20,807 --> 00:31:24,687 far deeper than the relatively shallow magma chamber, 390 00:31:24,687 --> 00:31:28,362 is a colossal volcanic pipe. 391 00:31:32,367 --> 00:31:35,127 Nobody's certain how deep it goes, 392 00:31:35,127 --> 00:31:38,847 but they can picture it down to 400 miles or more - 393 00:31:38,847 --> 00:31:43,159 twice the distance between Washington and New York. 394 00:31:47,447 --> 00:31:53,127 Smith makes an educated guess about what the underground plume is like. 395 00:31:53,127 --> 00:31:56,367 Our best estimates now as we start doing the physics 396 00:31:56,367 --> 00:32:00,087 and the dynamics of these things, it's like a conduit of melted rock, 397 00:32:00,087 --> 00:32:02,127 like a chimney. 398 00:32:02,127 --> 00:32:06,167 That chimney, called a hotspot, pumped up enough heat 399 00:32:06,167 --> 00:32:10,607 to melt the rocks of the crust and fill the overlying magma chamber, 400 00:32:10,607 --> 00:32:15,123 which then erupted to blast out Yellowstone's vast crater. 401 00:32:20,247 --> 00:32:23,727 Understanding how the crater formed was an important moment 402 00:32:23,727 --> 00:32:25,797 for the investigation. 403 00:32:28,047 --> 00:32:33,127 Because there was evidence that similar eruptions had happened before. 404 00:32:33,127 --> 00:32:35,038 Many times before. 405 00:32:46,127 --> 00:32:48,007 Throughout the 1960s, 406 00:32:48,007 --> 00:32:49,887 various teams of geologists 407 00:32:49,887 --> 00:32:51,647 studied the Snake River Plain, 408 00:32:51,647 --> 00:32:53,367 to the southwest of Yellowstone Park, 409 00:32:53,367 --> 00:32:54,887 and found traces 410 00:32:54,887 --> 00:32:57,481 of ancient volcanic craters. 411 00:32:58,727 --> 00:33:01,327 The crater rims had long been eroded, 412 00:33:01,327 --> 00:33:04,007 but their outlines were confirmed by aerial pictures 413 00:33:04,007 --> 00:33:06,396 over the following decade. 414 00:33:08,967 --> 00:33:12,087 They ran in a straight line along the plain, 415 00:33:12,087 --> 00:33:15,007 heading for the heart of Yellowstone Park. 416 00:33:15,007 --> 00:33:21,047 On average, each crater was a couple of million years older than its neighbour. 417 00:33:21,047 --> 00:33:22,647 Investigators realised 418 00:33:22,647 --> 00:33:26,887 that these are the remnants of earlier supervolcano explosions, 419 00:33:26,887 --> 00:33:31,483 an unbroken chain stretching far back into geological history. 420 00:33:37,167 --> 00:33:39,567 It seemed clear that, time after time, 421 00:33:39,567 --> 00:33:44,607 the hotspot had blasted out a supereruption and then moved on. 422 00:33:44,607 --> 00:33:49,362 The hotspot appeared to have travelled hundreds of miles. 423 00:33:51,647 --> 00:33:54,487 But that posed yet another riddle. 424 00:33:54,487 --> 00:34:00,039 How could a hotspot anchored to the core of the planet be moving? 425 00:34:08,847 --> 00:34:12,287 An important clue had been found in 1985 426 00:34:12,287 --> 00:34:15,484 by American volcanologist William Scott. 427 00:34:17,007 --> 00:34:20,527 He realised that plotting the location of 30,000 earthquakes 428 00:34:20,527 --> 00:34:24,566 around Yellowstone produced an amazing pattern. 429 00:34:25,967 --> 00:34:31,200 The quakes traced out a giant V-shape on the surface of the Earth. 430 00:34:32,887 --> 00:34:36,163 The V-shape wrapped around the hotspot's location. 431 00:34:37,407 --> 00:34:41,687 It seemed, at first, to confirm that the hotspot was still moving, 432 00:34:41,687 --> 00:34:45,127 rippling up the land around it with fault lines 433 00:34:45,127 --> 00:34:47,436 and tens of thousands of earthquakes. 434 00:34:53,807 --> 00:34:57,927 But the real answer lay with the theory of plate tectonics. 435 00:34:57,927 --> 00:35:03,797 It showed that it's the American continent, not the hotspot, that's moving. 436 00:35:05,327 --> 00:35:08,367 And the chain of craters on Snake River Plain is there 437 00:35:08,367 --> 00:35:12,687 because for millions of years, the moving American continent 438 00:35:12,687 --> 00:35:18,047 has continually pushed new land over the stationary hotspot. 439 00:35:18,047 --> 00:35:22,127 SMITH: But, as the North American Plate moved across this source of heat, 440 00:35:22,127 --> 00:35:27,047 it pops through the lid and creates the hotspot track. 441 00:35:27,047 --> 00:35:28,647 That's the Snake River Plain. 442 00:35:28,647 --> 00:35:30,922 Yellowstone is just the active component today. 443 00:35:32,007 --> 00:35:36,876 The repeated hotspot explosions on land have made Yellowstone unique. 444 00:35:39,367 --> 00:35:42,767 Other hotspots have been identified around the world, 445 00:35:42,767 --> 00:35:46,007 like the one that has created the island chain of Hawaii, 446 00:35:46,007 --> 00:35:50,407 but Yellowstone is the only place where a hotspot has erupted 447 00:35:50,407 --> 00:35:52,875 in the middle of a continent. 448 00:35:55,687 --> 00:36:00,647 Each of the earlier explosions blew the original mountains to pieces. 449 00:36:00,647 --> 00:36:05,367 Then, the land smoothed over with later flows of more runny lava 450 00:36:05,367 --> 00:36:08,916 that was released from deep under the Earth's crust. 451 00:36:15,127 --> 00:36:16,967 Multiple strands of evidence 452 00:36:16,967 --> 00:36:19,687 combine to reveal Yellowstone's slumbering monster, 453 00:36:19,687 --> 00:36:24,247 the gigantic hotspot plume lying under the park. 454 00:36:24,247 --> 00:36:28,240 Earthquake maps show the hotspot's location. 455 00:36:29,447 --> 00:36:33,360 Seismic waves reveal the depth of the plume. 456 00:36:34,447 --> 00:36:40,447 And earlier craters prove regular supereruptions over millions of years. 457 00:36:40,447 --> 00:36:44,127 All of which leads to the most frightening question of all. 458 00:36:44,127 --> 00:36:47,767 When will Yellowstone erupt again? 459 00:36:47,767 --> 00:36:50,839 (RUMBLING AND EXPLOSIONS) 460 00:36:59,047 --> 00:37:02,127 Measuring the amount and geographical spread of ashfall 461 00:37:02,127 --> 00:37:06,647 from Yellowstone's supereruptions produced some terrifying figures. 462 00:37:06,647 --> 00:37:08,887 (EXPLOSIONS) 463 00:37:08,887 --> 00:37:11,527 640,000 years ago, 464 00:37:11,527 --> 00:37:16,007 the eruption poured out around 240 cubic miles of material - 465 00:37:16,007 --> 00:37:22,887 enough to bury the whole of New York State tens of feet deep in ash. 466 00:37:22,887 --> 00:37:26,567 If it happens again, thousands will die 467 00:37:26,567 --> 00:37:32,367 and vast areas of the United States will be buried in volcanic debris. 468 00:37:32,367 --> 00:37:35,484 But when will Yellowstone erupt again? 469 00:37:39,607 --> 00:37:41,807 One clue to when that next eruption 470 00:37:41,807 --> 00:37:46,358 will happen comes from investigating the eruptions of the past. 471 00:37:48,527 --> 00:37:51,487 The hotspot punches out a supereruption, on average, 472 00:37:51,487 --> 00:37:54,126 every 600,000 years. 473 00:37:55,687 --> 00:38:00,636 And the last one was 640,000 years ago. 474 00:38:02,487 --> 00:38:05,607 But geologists expect that there will be warning signs 475 00:38:05,607 --> 00:38:08,167 before Yellowstone explodes again. 476 00:38:11,287 --> 00:38:13,847 Volcanic eruptions are usually preceded 477 00:38:13,847 --> 00:38:16,407 by an increasing number of earthquakes. 478 00:38:18,007 --> 00:38:21,527 The quakes are a sign that underground volcanic chambers 479 00:38:21,527 --> 00:38:25,007 are filling with molten rock and expanding to stretch and deform 480 00:38:25,007 --> 00:38:27,521 the land up above. 481 00:38:36,407 --> 00:38:38,887 Yellowstone Park usually experiences 482 00:38:38,887 --> 00:38:42,927 an average of 12 tiny earthquake tremors every day. 483 00:38:42,927 --> 00:38:46,007 Most are too weak to be felt by tourists 484 00:38:46,007 --> 00:38:49,967 and register only on the most sensitive seismometers. 485 00:38:49,967 --> 00:38:52,407 But in early 2009, 486 00:38:52,407 --> 00:38:57,007 more than four times as many quakes started striking every day. 487 00:38:57,007 --> 00:39:00,887 Over one ten-day period, there were more than 500 quakes, 488 00:39:00,887 --> 00:39:06,207 some of them up to magnitude 3.9, powerful enough to frighten the visitors 489 00:39:06,207 --> 00:39:08,038 and put the scientists on alert. 490 00:39:09,727 --> 00:39:13,356 There's a second indicator of increasing volcanic activity. 491 00:39:14,887 --> 00:39:19,087 If more molten rock does inflate the underground chamber, 492 00:39:19,087 --> 00:39:23,239 the ground above will rise. 493 00:39:25,687 --> 00:39:29,646 And that, too, seems to be happening right now. 494 00:39:32,567 --> 00:39:36,527 Unusual evidence to prove it comes from an unlikely source, 495 00:39:36,527 --> 00:39:39,519 the waters of Yellowstone Lake. 496 00:39:40,927 --> 00:39:44,967 Around 100 years ago, small steamships carried tourists 497 00:39:44,967 --> 00:39:47,167 on sightseeing trips across the lake. 498 00:39:47,167 --> 00:39:49,327 But one of the ships caught fire 499 00:39:49,327 --> 00:39:52,239 and sank forever below the surface of the lake. 500 00:39:53,887 --> 00:39:56,927 But now, Yellowstone's astonishing geological forces 501 00:39:56,927 --> 00:40:01,000 have resurrected the ship's remains from their watery grave. 502 00:40:02,127 --> 00:40:05,967 Here we have a boat which burnt down to water level 503 00:40:05,967 --> 00:40:12,567 and so this tells us something about the deformation of Yellowstone, 504 00:40:12,567 --> 00:40:17,407 and basically, what's happened is that the floor of the lake has risen, 505 00:40:17,407 --> 00:40:20,126 bringing the boat out of water. 506 00:40:21,247 --> 00:40:25,167 The reappearance of the wreck shows that land under and around the lake 507 00:40:25,167 --> 00:40:29,718 is rising because of the expansion of the magma chamber. 508 00:40:31,727 --> 00:40:36,767 Even more alarmingly, the rate at which it's rising seems to be increasing. 509 00:40:36,767 --> 00:40:41,607 In geological terms, a huge area of Yellowstone Park 510 00:40:41,607 --> 00:40:46,840 is positively soaring up into the air, faster than it's ever done before. 511 00:40:56,167 --> 00:40:59,447 The biggest uplift of all has been recorded just a few miles 512 00:40:59,447 --> 00:41:02,567 from the shore of the lake. 513 00:41:02,567 --> 00:41:04,607 There's a GPS system here, 514 00:41:04,607 --> 00:41:08,680 a much more sophisticated version of the one in your car. 515 00:41:09,687 --> 00:41:12,327 It measures not only its surface position, 516 00:41:12,327 --> 00:41:16,240 but also its exact altitude to within fractions of an inch. 517 00:41:17,847 --> 00:41:21,807 There's a small radio antenna, about the size of your thumb, that sits on top 518 00:41:21,807 --> 00:41:25,567 of this steel rod, and it is anchored in two to thr... 519 00:41:25,567 --> 00:41:28,527 ...about three or four feet, so if the ground moves up and down, 520 00:41:28,527 --> 00:41:30,245 the antenna moves up and down. 521 00:41:32,327 --> 00:41:36,639 The GPS and the land on which it's anchored are moving upwards. 522 00:41:37,967 --> 00:41:43,527 We're above the magma chamber and, beginning in late 2006, 523 00:41:43,527 --> 00:41:48,567 this whole area of ground started to rise, uh, 524 00:41:48,567 --> 00:41:51,927 at the order of two to three inches per year. 525 00:41:51,927 --> 00:41:58,087 And as of today, this whole system right here has risen about that much, 526 00:41:58,087 --> 00:42:00,047 and it's still moving today, 527 00:42:00,047 --> 00:42:03,967 and so we're measuring and keeping close track of the deformation, 528 00:42:03,967 --> 00:42:07,198 the... of the uplift that we're seeing at this station. 529 00:42:08,207 --> 00:42:11,847 But does the uplift mean that Yellowstone's supervolcano 530 00:42:11,847 --> 00:42:14,122 is threatening to erupt once again? 531 00:42:15,127 --> 00:42:19,727 The question of what lies in Yellowstone's geologic future 532 00:42:19,727 --> 00:42:21,407 is fascinating, 533 00:42:21,407 --> 00:42:28,404 and I and all of my colleagues would love to know the answer to that question. 534 00:42:29,407 --> 00:42:33,116 The scientists keep a careful watch on the volcano's activity. 535 00:42:35,607 --> 00:42:38,927 The idea of science is to understand the process 536 00:42:38,927 --> 00:42:43,607 and so we have a responsibility to see how this system is deforming, 537 00:42:43,607 --> 00:42:45,887 and how it's working, hence we have to be aware 538 00:42:45,887 --> 00:42:49,567 there is still a possibility of... of volcanic eruptions or earthquakes. 539 00:42:49,567 --> 00:42:51,447 After all, that's what made this system, 540 00:42:51,447 --> 00:42:54,803 and, uh, there is no reason to think that volcanism has stopped. 541 00:42:56,847 --> 00:42:58,927 The Yellowstone investigation has shown 542 00:42:58,927 --> 00:43:01,767 that the park's sleeping supervolcano 543 00:43:01,767 --> 00:43:04,520 is still alive, and dangerous. 544 00:43:05,527 --> 00:43:09,607 Old Faithful's underground plumbing reveals volcanic heat. 545 00:43:09,607 --> 00:43:12,767 Obsidian glass tells of a massive eruption. 546 00:43:12,767 --> 00:43:17,287 Seismographs record thousands of earthquakes, 547 00:43:17,287 --> 00:43:21,687 while the earthquake waves reveal terrifying underground chambers. 548 00:43:21,687 --> 00:43:27,000 And the reappearance of a sunken boat shows that the land is rising. 549 00:43:28,327 --> 00:43:31,847 And yet, the ultimate Yellowstone geological question 550 00:43:31,847 --> 00:43:33,967 remains to be answered. 551 00:43:33,967 --> 00:43:38,647 When will the supervolcano erupt once again? 552 00:43:38,647 --> 00:43:41,407 HEASLER: We know there's enough magma left, 553 00:43:41,407 --> 00:43:42,967 we know there's enough heat, 554 00:43:42,967 --> 00:43:46,807 we know that there will be future eruptions in Yellowstone. 555 00:43:46,807 --> 00:43:52,200 But we don't know if there will ever be another catastrophic eruption. 556 00:43:55,727 --> 00:44:00,567 So the investigation is left with a deadly serious warning. 557 00:44:00,567 --> 00:44:03,887 On the timescale that geologists work to, 558 00:44:03,887 --> 00:44:08,767 a coming supereruption in Yellowstone may well be right around the corner. 559 00:44:08,767 --> 00:44:13,927 That corner could be 10,000 or 100,000 years in the future. 560 00:44:13,927 --> 00:44:16,887 Or it could be tomorrow. 561 00:44:16,887 --> 00:44:21,087 A new and devastating chapter in the ever-changing story 562 00:44:21,087 --> 00:44:23,885 of how the Earth was made.