1 00:00:05,322 --> 00:00:07,923 NARRATOR: Deep below the Pacific Ocean 2 00:00:07,925 --> 00:00:11,660 lies a tectonic monster. 3 00:00:11,662 --> 00:00:13,729 MAN: You know how we told you not to panic? 4 00:00:13,731 --> 00:00:15,797 Well, that's all off. 5 00:00:15,799 --> 00:00:17,399 Panic. Run for your life. 6 00:00:17,401 --> 00:00:18,667 (screaming) 7 00:00:18,669 --> 00:00:22,538 NARRATOR: The world's biggest tsunami machine, 8 00:00:22,540 --> 00:00:26,741 its dangers hidden from view, 9 00:00:26,743 --> 00:00:28,343 until now. 10 00:00:31,481 --> 00:00:35,350 Imagine if we could empty the oceans, 11 00:00:35,352 --> 00:00:37,486 letting the water drain away 12 00:00:37,488 --> 00:00:41,490 to reveal the secrets of the seafloor. 13 00:00:41,492 --> 00:00:44,860 Now, we can, 14 00:00:44,862 --> 00:00:48,563 using the latest underwater scanning technology, 15 00:00:48,565 --> 00:00:50,432 piercing the deep oceans, 16 00:00:50,434 --> 00:00:56,071 and turning accurate data into 3D images. 17 00:00:56,073 --> 00:00:59,908 This time, is the world's next mega-earthquake 18 00:00:59,910 --> 00:01:02,210 brewing off the coast of Seattle? 19 00:01:02,212 --> 00:01:03,545 MAN: We can have the big one 20 00:01:03,547 --> 00:01:04,980 right now, as we speak. 21 00:01:04,982 --> 00:01:06,548 NARRATOR: Why has the discovery 22 00:01:06,550 --> 00:01:10,685 of an underwater volcano, just 44 miles from Tokyo, 23 00:01:10,687 --> 00:01:13,655 got seismic experts so worried? 24 00:01:13,657 --> 00:01:17,326 And what do scientists caught up in a undersea earthquake 25 00:01:17,328 --> 00:01:20,529 learn about the dangers facing New Zealand? 26 00:01:20,531 --> 00:01:24,333 MAN: The front of it would have a huge amount of energy. 27 00:01:24,335 --> 00:01:26,434 The scale is just immense. 28 00:01:26,436 --> 00:01:27,636 NARRATOR: Drain the Oceans 29 00:01:27,638 --> 00:01:32,074 reveals the secrets of the deadly Pacific. 30 00:01:32,076 --> 00:01:38,847 (music) 31 00:01:38,849 --> 00:01:44,920 (music) 32 00:01:44,922 --> 00:01:46,922 The Pacific Ocean-- 33 00:01:46,924 --> 00:01:50,893 the planet's largest and deepest. 34 00:01:50,895 --> 00:01:55,030 500 million people live around its coast. 35 00:01:58,936 --> 00:02:04,406 But deep beneath the waves lurks a terrifying monster 36 00:02:04,408 --> 00:02:08,443 that threatens all of them, 37 00:02:08,445 --> 00:02:13,715 the planet's largest and most dangerous seismic zone-- 38 00:02:13,717 --> 00:02:17,252 the Ring of Fire. 39 00:02:17,254 --> 00:02:21,523 90 percent of all earthquakes strike here 40 00:02:21,525 --> 00:02:23,192 and when they do, 41 00:02:23,194 --> 00:02:26,461 the consequences are devastating. 42 00:02:26,463 --> 00:02:27,729 (siren) 43 00:02:27,731 --> 00:02:33,802 (siren) 44 00:02:33,804 --> 00:02:36,004 March 11, 2011. 45 00:02:36,006 --> 00:02:38,540 (speaking Japanese) 46 00:02:38,542 --> 00:02:40,842 NARRATOR: Tohoku, northeastern Japan. 47 00:02:40,844 --> 00:02:42,844 (shouting) 48 00:02:42,846 --> 00:02:48,650 A magnitude 9 earthquake violently shakes the region. 49 00:02:48,652 --> 00:02:51,853 MAN: Oh! 50 00:02:51,855 --> 00:02:54,756 NARRATOR: The quake causes buildings to collapse 51 00:02:54,758 --> 00:02:58,293 and people to flee for their lives. 52 00:02:58,295 --> 00:03:01,363 (shouting) 53 00:03:01,365 --> 00:03:04,566 But that's not the end of the destruction. 54 00:03:08,305 --> 00:03:11,106 A defining characteristic of the Ring of Fire 55 00:03:11,108 --> 00:03:13,242 is that the biggest earthquakes here 56 00:03:13,244 --> 00:03:17,779 shake not just the land, but the seabed as well... 57 00:03:20,717 --> 00:03:24,619 ...generating huge surges of water... 58 00:03:24,621 --> 00:03:26,121 (speaking Japanese) 59 00:03:26,123 --> 00:03:28,824 NARRATOR: ...deadly tsunamis. 60 00:03:28,826 --> 00:03:32,694 (shouting) 61 00:03:32,696 --> 00:03:36,298 (music) 62 00:03:36,300 --> 00:03:42,904 (music) 63 00:03:42,906 --> 00:03:43,739 (shouting) 64 00:03:43,741 --> 00:03:50,111 (shouting) 65 00:03:50,113 --> 00:03:54,816 (music) 66 00:03:54,818 --> 00:03:59,821 (music) 67 00:03:59,823 --> 00:04:03,926 In Japan, almost 16,000 people are killed. 68 00:04:06,163 --> 00:04:10,098 And geologists are certain it will happen again 69 00:04:10,100 --> 00:04:13,969 somewhere around the Pacific Ring of Fire, 70 00:04:13,971 --> 00:04:16,872 but when and where? 71 00:04:20,711 --> 00:04:22,910 Pulling the plug on the Pacific Ocean 72 00:04:22,912 --> 00:04:26,881 reveals a glimpse of one of its most terrifying secrets, 73 00:04:26,883 --> 00:04:30,786 just off the west coast of America-- 74 00:04:30,788 --> 00:04:33,588 not the infamous San Andreas Fault 75 00:04:33,590 --> 00:04:35,524 in California, 76 00:04:35,526 --> 00:04:38,193 but something close to the teeming cities 77 00:04:38,195 --> 00:04:42,130 of Portland, Seattle, and Vancouver, 78 00:04:42,132 --> 00:04:44,333 something far more menacing. 79 00:04:44,335 --> 00:04:49,404 (music) 80 00:04:49,406 --> 00:04:52,140 LELAND O'DRISCOLL: It's known that it's an active structure. 81 00:04:52,142 --> 00:04:53,408 It could happen now, and that's 82 00:04:53,410 --> 00:04:55,076 truly the source of fear. 83 00:04:55,078 --> 00:05:00,749 (music) 84 00:05:00,751 --> 00:05:02,350 NARRATOR: This region of North America 85 00:05:02,352 --> 00:05:06,354 is known as Cascadia, 86 00:05:06,356 --> 00:05:10,992 one of the most beautiful and peaceful in North America. 87 00:05:10,994 --> 00:05:13,795 It's also home to 10 million people. 88 00:05:16,366 --> 00:05:20,568 They feel safe here, and why wouldn't they? 89 00:05:20,570 --> 00:05:23,504 In all recorded history, there's been no trace 90 00:05:23,506 --> 00:05:27,642 of any natural disasters in the region, 91 00:05:27,644 --> 00:05:31,512 but on the 18th of May 1980, 92 00:05:31,514 --> 00:05:34,315 everything changes. 93 00:05:34,317 --> 00:05:35,583 (rumbling) 94 00:05:35,585 --> 00:05:36,651 MAN: There is no question at all 95 00:05:36,653 --> 00:05:39,454 that the volcanic activity has begun. 96 00:05:39,456 --> 00:05:44,259 NARRATOR: Mount St. Helens, 50 miles from Portland. 97 00:05:44,261 --> 00:05:47,996 Huge eruptions blast a 1,300-foot crater 98 00:05:47,998 --> 00:05:52,034 in the summit of a volcano long thought to be dormant. 99 00:05:55,739 --> 00:05:58,106 REPORTER: It is the biggest eruption ever recorded 100 00:05:58,108 --> 00:05:59,841 of Mount St. Helens so far. 101 00:05:59,843 --> 00:06:00,742 REPORTER: I think it does not look good 102 00:06:00,744 --> 00:06:02,744 for people in that area now. 103 00:06:02,746 --> 00:06:04,612 NARRATOR: It's the worst volcano disaster 104 00:06:04,614 --> 00:06:08,984 in U.S. history, claiming 57 lives. 105 00:06:08,986 --> 00:06:11,953 (music) 106 00:06:11,955 --> 00:06:16,291 (music) 107 00:06:16,293 --> 00:06:20,762 Scientists are now forced to ask a tough question. 108 00:06:20,764 --> 00:06:23,364 MAN: Is it, is it scaled to look at tsunamis? 109 00:06:23,366 --> 00:06:24,532 NARRATOR: Does the eruption 110 00:06:24,534 --> 00:06:27,335 of the supposedly inactive Mount St. Helens 111 00:06:27,337 --> 00:06:30,572 mean the 10 million inhabitants of Cascadia 112 00:06:30,574 --> 00:06:34,041 are now sitting on a seismic time bomb 113 00:06:34,043 --> 00:06:37,045 that just started ticking? 114 00:06:37,047 --> 00:06:41,116 To find out, scientists launch an urgent investigation 115 00:06:41,118 --> 00:06:44,819 on land and deep under the sea. 116 00:06:44,821 --> 00:06:48,490 Off the coast of Cascadia, the latest scanning technology 117 00:06:48,492 --> 00:06:53,795 reveals something extraordinary and terrifying. 118 00:06:53,797 --> 00:06:57,598 Based upon their exact data, for the first time, 119 00:06:57,600 --> 00:07:00,602 we can pull the plug on the Pacific Ocean 120 00:07:00,604 --> 00:07:04,405 to reveal their shocking discovery. 121 00:07:04,407 --> 00:07:07,142 As the water drains away, 122 00:07:07,144 --> 00:07:12,314 a vast world no human has ever seen before is laid bare. 123 00:07:15,185 --> 00:07:18,086 For mile after mile across its heart, 124 00:07:18,088 --> 00:07:19,954 the Pacific Ocean floor 125 00:07:19,956 --> 00:07:23,792 is a vast, flat, featureless plain... 126 00:07:26,029 --> 00:07:29,197 ...until suddenly, 127 00:07:29,199 --> 00:07:31,166 the landscape changes. 128 00:07:33,836 --> 00:07:35,971 Here, just 150 miles 129 00:07:35,973 --> 00:07:40,008 from the great cities of the Pacific Northwest, 130 00:07:40,010 --> 00:07:43,377 a dramatic transformation takes place, 131 00:07:43,379 --> 00:07:46,748 revealing a fractured, broken seafloor... 132 00:07:48,585 --> 00:07:50,852 ...brooding, 133 00:07:50,854 --> 00:07:52,787 menacing. 134 00:07:52,789 --> 00:07:54,322 O'DRISCOLL: One of the best analogies I can think of 135 00:07:54,324 --> 00:07:57,492 is looking at the, the front end of a car 136 00:07:57,494 --> 00:08:00,328 that's been in a head-on collision, 137 00:08:00,330 --> 00:08:02,530 dented and corroded and corrugated 138 00:08:02,532 --> 00:08:04,766 into this complex mess. 139 00:08:08,138 --> 00:08:10,872 NARRATOR: The scale of this geological fender bender 140 00:08:10,874 --> 00:08:12,874 is truly epic. 141 00:08:14,878 --> 00:08:16,678 Colossal cliffs, 142 00:08:16,680 --> 00:08:19,548 almost twice the height of the Grand Canyon... 143 00:08:21,885 --> 00:08:25,953 ...some deep enough to hide six Empire State Buildings 144 00:08:25,955 --> 00:08:29,490 stacked on top of each other, 145 00:08:29,492 --> 00:08:34,496 all of it stretching 700 miles along the Cascadian coastline. 146 00:08:38,568 --> 00:08:41,436 This titanic rupture in the earth's crust 147 00:08:41,438 --> 00:08:45,307 is what geologists call a subduction zone. 148 00:08:50,113 --> 00:08:51,479 At the core of our planet 149 00:08:51,481 --> 00:08:54,449 is a boiling cauldron of molten iron, 150 00:08:54,451 --> 00:08:59,987 surrounded by a thick mantle of rock. 151 00:08:59,989 --> 00:09:04,425 That outer crust is divided into huge tectonic plates 152 00:09:04,427 --> 00:09:06,695 that are constantly in motion. 153 00:09:09,733 --> 00:09:13,601 When they collide, they thrust mountains upwards 154 00:09:13,603 --> 00:09:16,738 and carve deep trenches into the ocean floor 155 00:09:16,740 --> 00:09:21,610 as one plate drives the other back inside the earth. 156 00:09:23,279 --> 00:09:25,280 If the plates lock together, 157 00:09:25,282 --> 00:09:28,049 tremendous pressure begins to build. 158 00:09:31,355 --> 00:09:32,620 O'DRISCOLL: Only in subduction zones 159 00:09:32,622 --> 00:09:34,355 where the plates are compressing together 160 00:09:34,357 --> 00:09:36,291 and there's this lock between the plates, 161 00:09:36,293 --> 00:09:37,959 that, those are the only fault zones 162 00:09:37,961 --> 00:09:39,093 that have the potential 163 00:09:39,095 --> 00:09:40,295 to create magnitude 164 00:09:40,297 --> 00:09:42,163 9.0 and higher events. 165 00:09:44,034 --> 00:09:46,134 NARRATOR: But that's not all. 166 00:09:46,136 --> 00:09:49,771 Subduction zones, because they are underwater, 167 00:09:49,773 --> 00:09:54,576 can generate not just earthquakes, but huge tsunamis. 168 00:09:58,648 --> 00:10:02,850 Written history suggests that Cascadia's subduction zone 169 00:10:02,852 --> 00:10:06,121 has been inactive for centuries, 170 00:10:06,123 --> 00:10:10,758 but does written history go back far enough? 171 00:10:10,760 --> 00:10:15,430 Is this monster really as sleepy as it seems? 172 00:10:15,432 --> 00:10:21,502 (music) 173 00:10:21,504 --> 00:10:24,472 Scientists scour the landscape around Cascadia 174 00:10:24,474 --> 00:10:26,974 in search of answers, 175 00:10:26,976 --> 00:10:30,812 and, in the banks of coastal rivers like this, 176 00:10:30,814 --> 00:10:34,749 they find an alarming pattern. 177 00:10:34,751 --> 00:10:37,018 DAVID YAMAGUCHI: It's very much like a chocolate cake. 178 00:10:37,020 --> 00:10:38,085 You slice a chocolate cake, 179 00:10:38,087 --> 00:10:40,221 and there's a layer of brown frosting, 180 00:10:40,223 --> 00:10:43,224 and then, down below, there's another layer of brown frosting, 181 00:10:43,226 --> 00:10:46,160 and the Washington coast looks very much like that. 182 00:10:46,162 --> 00:10:47,562 NARRATOR: But there's nothing sweet 183 00:10:47,564 --> 00:10:50,898 about these layers of peat and sand. 184 00:10:50,900 --> 00:10:52,701 YAMAGUCHI: Each of these buried soil layers 185 00:10:52,703 --> 00:10:54,703 on the Washington coast 186 00:10:54,705 --> 00:10:58,372 reflected times when the coast had been jerked downwards 187 00:10:58,374 --> 00:11:01,542 by the occurrence of an earthquake. 188 00:11:01,544 --> 00:11:03,310 NARRATOR: In the layers of peat, 189 00:11:03,312 --> 00:11:07,115 David Yamaguchi and geologist Brian Atwater 190 00:11:07,117 --> 00:11:10,118 unearth evidence of seismic devastation 191 00:11:10,120 --> 00:11:13,654 stretching back over thousands of years, 192 00:11:13,656 --> 00:11:18,093 quakes that scarred the entire coastline of Cascadia. 193 00:11:18,095 --> 00:11:20,195 The question now is, 194 00:11:20,197 --> 00:11:24,199 when was the last one, and how big was it? 195 00:11:28,939 --> 00:11:32,040 NARRATOR: The Copalis River, Washington State. 196 00:11:34,911 --> 00:11:39,481 Scientist David Yamaguchi is on a quest. 197 00:11:39,483 --> 00:11:42,750 He and his fellow scientists already suspect 198 00:11:42,752 --> 00:11:45,787 that the 10 million inhabitants of Cascadia 199 00:11:45,789 --> 00:11:49,624 are living on a seismic time bomb, 200 00:11:49,626 --> 00:11:52,326 but when did it last go off, 201 00:11:52,328 --> 00:11:56,831 and how big was it when it did? 202 00:11:56,833 --> 00:12:02,170 Three miles inland, he comes across a haunting sight. 203 00:12:02,172 --> 00:12:08,375 (music) 204 00:12:08,377 --> 00:12:14,315 (music) 205 00:12:14,317 --> 00:12:17,552 This is what's left of a once mighty forest 206 00:12:17,554 --> 00:12:22,123 of red cedar and spruce trees, 207 00:12:22,125 --> 00:12:24,259 thousands of petrified corpses 208 00:12:24,261 --> 00:12:26,194 scattered over hundreds of miles 209 00:12:26,196 --> 00:12:28,863 along Cascadia's coast. 210 00:12:28,865 --> 00:12:29,930 YAMAGUCHI: And the mystery here 211 00:12:29,932 --> 00:12:32,133 is what killed the trees, 212 00:12:32,135 --> 00:12:35,770 and when did they die? 213 00:12:35,772 --> 00:12:42,376 (chainsaw) 214 00:12:42,378 --> 00:12:45,580 NARRATOR: Sampling dozens of the trees, 215 00:12:45,582 --> 00:12:48,616 Yamaguchi analyzes their age rings, 216 00:12:48,618 --> 00:12:52,020 and what he finds is a new mystery. 217 00:12:52,022 --> 00:12:54,889 YAMAGUCHI: The trees were fine and healthy in 1699. 218 00:12:54,891 --> 00:12:56,690 Then, the following summer, 219 00:12:56,692 --> 00:12:58,493 the trees that, that would normally have produced 220 00:12:58,495 --> 00:13:00,161 another annual ring 221 00:13:00,163 --> 00:13:01,229 were nearly all dead. 222 00:13:02,999 --> 00:13:06,434 NARRATOR: What happened to kill an entire forest 223 00:13:06,436 --> 00:13:09,571 in one instant? 224 00:13:09,573 --> 00:13:12,907 Another scientist thinks the answer could lie 225 00:13:12,909 --> 00:13:15,076 deep in the geological car crash 226 00:13:15,078 --> 00:13:17,378 of the Cascadia subduction zone, 227 00:13:17,380 --> 00:13:19,714 just 100 miles away. 228 00:13:19,716 --> 00:13:24,118 (music) 229 00:13:24,120 --> 00:13:29,457 Chris Goldfinger is an underwater earthquake detective 230 00:13:29,459 --> 00:13:31,826 seeking evidence in core samples 231 00:13:31,828 --> 00:13:35,596 taken from deep under the seafloor. 232 00:13:35,598 --> 00:13:37,565 Studying the layers of sediment 233 00:13:37,567 --> 00:13:41,402 reveals when and where earthquakes struck in the past 234 00:13:41,404 --> 00:13:44,672 and how powerful they were. 235 00:13:44,674 --> 00:13:46,207 CHRIS GOLDFINGER: Sediment settles to the seafloor, 236 00:13:46,209 --> 00:13:48,076 but it got there somehow, 237 00:13:48,078 --> 00:13:52,013 from some storm, an earthquake, and even a volcanic eruption 238 00:13:52,015 --> 00:13:54,215 will leave a deposit on the seafloor, 239 00:13:54,217 --> 00:13:57,952 and so it's just a very precise, 240 00:13:57,954 --> 00:13:59,219 three-dimensional tape recorder, 241 00:13:59,221 --> 00:14:01,422 just recording every single thing that happens. 242 00:14:03,826 --> 00:14:05,092 Well, this is a core sample 243 00:14:05,094 --> 00:14:09,097 from, from the seafloor off of Cascadia, 244 00:14:09,099 --> 00:14:12,934 and it's about 2,000 years' worth of sediment. 245 00:14:12,936 --> 00:14:15,002 NARRATOR: In the middle of the sample, 246 00:14:15,004 --> 00:14:17,906 dating to roughly 300 years ago, 247 00:14:17,908 --> 00:14:22,610 Goldfinger finds the classic signs of a large earthquake. 248 00:14:22,612 --> 00:14:24,045 GOLDFINGER: Well, in fact, the shells like this 249 00:14:24,047 --> 00:14:26,781 turn out to be shallow-water fossils, 250 00:14:26,783 --> 00:14:28,516 but this is a deep-water core, 251 00:14:28,518 --> 00:14:29,917 so these things were carried down 252 00:14:29,919 --> 00:14:32,420 from shallow water to deep water. 253 00:14:32,422 --> 00:14:36,457 What this points to is a fairly dramatic kind of event. 254 00:14:36,459 --> 00:14:38,993 (rumbling) 255 00:14:38,995 --> 00:14:42,397 NARRATOR: That dramatic event was an earthquake 256 00:14:42,399 --> 00:14:47,334 that triggered a vast underwater landslide. 257 00:14:47,336 --> 00:14:50,070 And it all happened around the same time 258 00:14:50,072 --> 00:14:54,208 that Yamaguchi's trees died. 259 00:14:54,210 --> 00:14:57,946 Next, he compares core samples of the same date, 260 00:14:57,948 --> 00:14:59,948 taken along the 700 miles 261 00:14:59,950 --> 00:15:03,150 of the Cascadia subduction zone. 262 00:15:03,152 --> 00:15:07,321 Core after core reveals the same disturbed layer, 263 00:15:07,323 --> 00:15:10,825 all occurring at the exact same time. 264 00:15:14,164 --> 00:15:18,766 This is evidence of no ordinary earthquake, 265 00:15:18,768 --> 00:15:21,436 but a monster. 266 00:15:21,438 --> 00:15:24,772 GOLDFINGER: Cascadia, through the study of past earthquakes, 267 00:15:24,774 --> 00:15:26,907 has shown that it's capable of generating earthquakes 268 00:15:26,909 --> 00:15:31,646 that run the full length, roughly 1,000 kilometers. 269 00:15:31,648 --> 00:15:35,315 NARRATOR: In 1700, the Cascadia subduction zone 270 00:15:35,317 --> 00:15:39,520 generated a cataclysmic quake along its entire length, 271 00:15:39,522 --> 00:15:42,656 with a magnitude that Goldfinger and other scientists 272 00:15:42,658 --> 00:15:45,893 calculate as level 8. 273 00:15:48,264 --> 00:15:50,531 But that's not all. 274 00:15:50,533 --> 00:15:55,302 This was more than just an earthquake. 275 00:15:55,304 --> 00:16:00,074 Japan has a long history of earthquakes and tsunamis, 276 00:16:00,076 --> 00:16:04,879 with written evidence going back 1,400 years. 277 00:16:04,881 --> 00:16:07,081 Among these historical records, 278 00:16:07,083 --> 00:16:10,418 in accounts written by samurai and merchants, 279 00:16:10,420 --> 00:16:14,555 researchers uncover reports of a 16-foot tsunami 280 00:16:14,557 --> 00:16:18,426 that arrives from far out in the Pacific, 281 00:16:18,428 --> 00:16:20,762 swamping the eastern coast. 282 00:16:20,764 --> 00:16:22,430 It destroys houses 283 00:16:22,432 --> 00:16:25,566 and causes villagers to flee to higher ground. 284 00:16:27,237 --> 00:16:31,339 The date of these reports? 285 00:16:31,341 --> 00:16:34,241 1700. 286 00:16:34,243 --> 00:16:38,312 YAMAGUCHI: They propose that our earthquake was magnitude 9. 287 00:16:38,314 --> 00:16:40,381 A magnitude 8 was not big enough 288 00:16:40,383 --> 00:16:43,117 to produce a wave that's that wide. 289 00:16:43,119 --> 00:16:44,384 In addition, 290 00:16:44,386 --> 00:16:47,188 based on the arrival times of the waves in Japan, 291 00:16:47,190 --> 00:16:48,522 the earthquake must have happened here 292 00:16:48,524 --> 00:16:51,826 on January 26, 1700 293 00:16:51,828 --> 00:16:53,894 at 9:00 at night, 294 00:16:53,896 --> 00:16:55,029 yes, local time. 295 00:16:56,999 --> 00:17:00,267 NARRATOR: The Cascadia mega-quake was so powerful 296 00:17:00,269 --> 00:17:01,936 that it generated a tsunami 297 00:17:01,938 --> 00:17:06,774 that hit Japan, 4,500 miles away. 298 00:17:09,479 --> 00:17:10,878 Using the combined insights 299 00:17:10,880 --> 00:17:14,215 of experts from both sides of the Pacific 300 00:17:14,217 --> 00:17:16,617 and the extraordinary drained landscape 301 00:17:16,619 --> 00:17:19,387 of the subduction zone, 302 00:17:19,389 --> 00:17:21,556 it's now possible to visualize 303 00:17:21,558 --> 00:17:26,427 the titanic events of January 1700 304 00:17:26,429 --> 00:17:30,030 and its deadly trail of destruction. 305 00:17:30,032 --> 00:17:34,168 (music) 306 00:17:34,170 --> 00:17:35,402 GOLDFINGER: The entire subduction zone 307 00:17:35,404 --> 00:17:37,805 shakes very hard. 308 00:17:40,509 --> 00:17:43,778 The ground motion is big, and it's over a big area, 309 00:17:43,780 --> 00:17:45,980 so it's gonna shake a lot of sediment loose. 310 00:17:45,982 --> 00:17:50,918 (music) 311 00:17:50,920 --> 00:17:52,786 There are gonna be hundreds of landslides. 312 00:17:52,788 --> 00:17:54,822 They're gonna all come tumbling down the slope 313 00:17:54,824 --> 00:17:56,524 and leave a deposit. 314 00:17:56,526 --> 00:18:02,463 (music) 315 00:18:02,465 --> 00:18:04,298 (music) 316 00:18:06,603 --> 00:18:09,737 NARRATOR: The quake also triggers a huge tsunami 317 00:18:09,739 --> 00:18:14,475 which smashes into the coast of Cascadia, 318 00:18:14,477 --> 00:18:17,779 flooding the land with seawater, 319 00:18:17,781 --> 00:18:20,347 including the red cedar forest 320 00:18:20,349 --> 00:18:23,217 and everything else in its path. 321 00:18:27,557 --> 00:18:29,623 Although there is no written history 322 00:18:29,625 --> 00:18:33,527 of the 1700 earthquake and tsunami in Cascadia, 323 00:18:33,529 --> 00:18:35,296 native peoples of this region 324 00:18:35,298 --> 00:18:40,000 do hold haunting memories of these terrible events. 325 00:18:40,002 --> 00:18:42,302 GOLDFINGER: The First Nation peoples had oral histories 326 00:18:42,304 --> 00:18:45,873 about the great battle of Thunderbird and Whale 327 00:18:45,875 --> 00:18:47,775 that had a lot of shaking of the ground, 328 00:18:47,777 --> 00:18:50,244 washing away of villages. 329 00:18:50,246 --> 00:18:51,779 MAN: The Great Thunderbird 330 00:18:51,781 --> 00:18:55,082 finally carried the Whale to its nest. 331 00:18:55,084 --> 00:18:58,085 There were a shaking, jumping up, 332 00:18:58,087 --> 00:19:00,788 and trembling of the earth beneath 333 00:19:00,790 --> 00:19:03,724 and the rolling up of the great waters. 334 00:19:03,726 --> 00:19:05,326 GOLDFINGER: So, once these stories came to light, 335 00:19:05,328 --> 00:19:07,461 the Native Americans essentially said, 336 00:19:07,463 --> 00:19:11,332 'Why didn't you just ask us? We knew all about that.' 337 00:19:11,334 --> 00:19:12,800 The story had a moral, and the moral was, 338 00:19:12,802 --> 00:19:15,369 don't build your village too close to the beach. 339 00:19:18,741 --> 00:19:24,211 NARRATOR: But evidently, no one was listening. 340 00:19:24,213 --> 00:19:28,950 Today, 10 million people live along the coast of Cascadia 341 00:19:28,952 --> 00:19:33,921 and in the cities of Seattle, Portland, and Vancouver, 342 00:19:33,923 --> 00:19:36,890 and the question is how likely is it 343 00:19:36,892 --> 00:19:40,227 that the monster will roar again? 344 00:19:40,229 --> 00:19:42,096 THOMAS HEATON: It's not at all like a clock, 345 00:19:42,098 --> 00:19:43,497 but the average time 346 00:19:43,499 --> 00:19:44,765 between the earthquakes 347 00:19:44,767 --> 00:19:47,869 is on the order of 400 years. 348 00:19:47,871 --> 00:19:50,103 NARRATOR: If the Cascadia subduction zone 349 00:19:50,105 --> 00:19:52,973 repeats its 400-year cycle, 350 00:19:52,975 --> 00:19:56,911 then its next mega-quake could be imminent. 351 00:19:56,913 --> 00:19:58,645 O'DRISCOLL: We know the strain is building, 352 00:19:58,647 --> 00:20:00,581 and we know, one day, it's gonna be released, 353 00:20:00,583 --> 00:20:02,516 and that could happen any day. 354 00:20:02,518 --> 00:20:06,520 NARRATOR: So, what will happen when the monster wakes? 355 00:20:06,522 --> 00:20:08,089 GOLDFINGER: In a subduction zone earthquake, 356 00:20:08,091 --> 00:20:11,692 energy is stretched out, not 10 seconds or 20 seconds, 357 00:20:11,694 --> 00:20:13,194 more like three minutes. 358 00:20:13,196 --> 00:20:14,194 HEATON: The shaking's not 359 00:20:14,196 --> 00:20:16,130 incredibly violent, 360 00:20:16,132 --> 00:20:17,465 but it lasts for a long time, 361 00:20:17,467 --> 00:20:19,266 and it's a very long, 362 00:20:19,268 --> 00:20:21,168 rolling motion. 363 00:20:21,170 --> 00:20:24,672 For tall buildings, that's not good news. 364 00:20:28,277 --> 00:20:30,144 NARRATOR: With buildings collapsing 365 00:20:30,146 --> 00:20:32,680 and infrastructures shattered, 366 00:20:32,682 --> 00:20:35,182 it will be hard for the population to escape 367 00:20:35,184 --> 00:20:38,085 from the coastal area, 368 00:20:38,087 --> 00:20:42,823 the worst place to be trapped. 369 00:20:42,825 --> 00:20:44,959 HEATON: You know that if you get a giant earthquake, 370 00:20:44,961 --> 00:20:46,160 you'd better assume you're 371 00:20:46,162 --> 00:20:47,762 about to get a giant tsunami. 372 00:20:50,599 --> 00:20:53,734 NARRATOR: The tectonic plates' sudden release of pressure 373 00:20:53,736 --> 00:20:58,439 forces a massive swell in the ocean above. 374 00:20:58,441 --> 00:21:00,708 GOLDFINGER: So, the wave height, initially, 375 00:21:00,710 --> 00:21:02,509 might only be a couple of meters, 376 00:21:02,511 --> 00:21:05,012 but it might be 200 kilometers long, 377 00:21:05,014 --> 00:21:07,247 and it heads out at the deep-water wave speed, 378 00:21:07,249 --> 00:21:09,316 which is very fast, so it's jetliner speed, 379 00:21:09,318 --> 00:21:11,252 500 or 600 miles an hour. 380 00:21:13,122 --> 00:21:16,090 Everything we've seen in Japan, we can expect, basically, 381 00:21:16,092 --> 00:21:17,925 the exact same thing in Cascadia. 382 00:21:17,927 --> 00:21:21,929 (man on loudspeaker) 383 00:21:21,931 --> 00:21:25,065 HEATON: 30 meters of water rushing in 384 00:21:25,067 --> 00:21:28,869 at 10 meters a second kind of velocities... 385 00:21:31,273 --> 00:21:32,206 ...it just scours 386 00:21:32,208 --> 00:21:33,541 everything off the, 387 00:21:33,543 --> 00:21:35,343 off the surface of the earth. 388 00:21:36,446 --> 00:21:38,045 NARRATOR: Within 20 minutes, 389 00:21:38,047 --> 00:21:41,349 the tsunami will approach the coast of Cascadia. 390 00:21:41,351 --> 00:21:42,817 GOLDFINGER: When that wave starts feeling bottom, 391 00:21:42,819 --> 00:21:43,950 like all other waves do, 392 00:21:43,952 --> 00:21:45,920 it gets compressed from 200 kilometers 393 00:21:45,922 --> 00:21:48,188 down to a kilometer or two. 394 00:21:48,190 --> 00:21:49,523 HEATON: It's like an enormous 395 00:21:49,525 --> 00:21:52,259 tide happening very quickly. 396 00:21:52,261 --> 00:21:57,298 (music) 397 00:22:01,504 --> 00:22:04,238 NARRATOR: A Cascadia mega-quake is predicted to be 398 00:22:04,240 --> 00:22:08,976 North America's worst ever natural disaster. 399 00:22:08,978 --> 00:22:11,912 O'DRISCOLL: The fatalities could be fairly large. 400 00:22:11,914 --> 00:22:14,781 We're looking at, at a few tens of thousands of people, 401 00:22:14,783 --> 00:22:16,083 at least, on our coastline. 402 00:22:16,085 --> 00:22:18,118 We know the strain is building, 403 00:22:18,120 --> 00:22:19,453 and that's quite harrowing to know 404 00:22:19,455 --> 00:22:23,591 that we could have the big one right now, as we speak. 405 00:22:23,593 --> 00:22:26,793 NARRATOR: But Cascadia is not the only populated region 406 00:22:26,795 --> 00:22:30,598 in the Ring of Fire danger zone. 407 00:22:30,600 --> 00:22:34,402 As the waters of the Pacific continue to drain away, 408 00:22:34,404 --> 00:22:37,471 they reveal another sleeping giant 409 00:22:37,473 --> 00:22:40,207 near the east coast of New Zealand, 410 00:22:40,209 --> 00:22:44,478 where scientists discover traces of an epic seismic event 411 00:22:44,480 --> 00:22:47,547 that reshaped the Southern Hemisphere 412 00:22:47,549 --> 00:22:52,486 and ask, when will it happen again? 413 00:22:59,595 --> 00:23:01,462 NARRATOR: The islands of New Zealand 414 00:23:01,464 --> 00:23:05,198 lie directly on the Ring of Fire. 415 00:23:05,200 --> 00:23:10,270 Small earthquakes shake the ground here every week. 416 00:23:10,272 --> 00:23:14,007 (sirens) 417 00:23:14,009 --> 00:23:15,676 (screaming) 418 00:23:15,678 --> 00:23:19,814 In 2011, the country's second largest city, Christchurch, 419 00:23:19,816 --> 00:23:24,385 is devastated by a magnitude 6.3 quake... 420 00:23:24,387 --> 00:23:26,753 WOMAN: I can confirm that there have been deaths. 421 00:23:26,755 --> 00:23:29,490 NARRATOR: ...killing 185 people. 422 00:23:29,492 --> 00:23:31,192 (siren) 423 00:23:37,800 --> 00:23:40,100 100 miles from Christchurch 424 00:23:40,102 --> 00:23:42,203 is the town of Kaikoura. 425 00:23:44,040 --> 00:23:45,172 MAN: Kaikoura, welcome aboard. 426 00:23:45,174 --> 00:23:46,439 WOMAN: Thank you. 427 00:23:46,441 --> 00:23:48,142 NARRATOR: A peaceful holiday resort 428 00:23:48,144 --> 00:23:50,177 that's popular with nature lovers. 429 00:23:50,179 --> 00:23:51,511 MAN: Keep looking out there. 430 00:23:51,513 --> 00:23:54,048 You'll see them just out of the front of us there. 431 00:23:54,050 --> 00:23:56,717 NARRATOR: Its deep, nutrient-rich waters 432 00:23:56,719 --> 00:23:59,252 entice whales close to the shore. 433 00:23:59,254 --> 00:24:02,590 MAN: This is the beautiful humpback, 434 00:24:02,592 --> 00:24:06,594 and it is awesome to see humps. 435 00:24:06,596 --> 00:24:07,794 NARRATOR: While these leviathans 436 00:24:07,796 --> 00:24:12,333 are Kaikoura's star attraction, 437 00:24:12,335 --> 00:24:16,537 geologists now come here for a very different reason. 438 00:24:18,474 --> 00:24:21,474 New Zealand's geologists constantly monitor 439 00:24:21,476 --> 00:24:24,278 the threat posed by the faults and fissures 440 00:24:24,280 --> 00:24:26,280 that run under the islands, 441 00:24:26,282 --> 00:24:30,150 trying to discover where the next big quake might strike. 442 00:24:32,288 --> 00:24:34,154 Ground surveys can help, 443 00:24:34,156 --> 00:24:36,357 but investigating under the waves 444 00:24:36,359 --> 00:24:39,093 has always been a challenge, 445 00:24:39,095 --> 00:24:40,760 until now, 446 00:24:40,762 --> 00:24:44,097 because the latest multiple-beam sonar technology 447 00:24:44,099 --> 00:24:47,668 is opening up a hidden world. 448 00:24:47,670 --> 00:24:50,838 JOSHU MOUNTJOY: It's multiple beams of sound energy 449 00:24:50,840 --> 00:24:53,173 being released from the instrument on the vessel, 450 00:24:53,175 --> 00:24:56,443 and we time how long it takes for that beam to come back. 451 00:24:56,445 --> 00:24:57,845 (beeping) 452 00:24:57,847 --> 00:24:59,780 We do what we call mowing the grass, 453 00:24:59,782 --> 00:25:02,449 and we're just collecting this continuous image 454 00:25:02,451 --> 00:25:05,686 of what the shape of the seabed is. 455 00:25:05,688 --> 00:25:08,455 NARRATOR: And the shape of the seabed near Kaikoura 456 00:25:08,457 --> 00:25:12,660 is not what they expected. 457 00:25:12,662 --> 00:25:15,929 As the data comes in, it slowly reveals 458 00:25:15,931 --> 00:25:19,967 something astonishing and potentially lethal. 459 00:25:23,139 --> 00:25:26,406 Pulling the plug on the Pacific Ocean 460 00:25:26,408 --> 00:25:28,776 exposes the remarkable sight. 461 00:25:33,883 --> 00:25:37,684 Just a half mile from the town of Kaikoura, 462 00:25:37,686 --> 00:25:40,521 as the water drains away, 463 00:25:40,523 --> 00:25:45,526 it reveals the plunging walls of a vast, undersea chasm... 464 00:25:48,431 --> 00:25:52,532 ...the Kaikoura Canyon. 465 00:25:52,534 --> 00:25:53,500 MOUNTJOY: The Kaikoura Canyon, 466 00:25:53,502 --> 00:25:55,369 it comes within a really short distance 467 00:25:55,371 --> 00:25:59,172 of the coastline out here, less than a kilometer, 468 00:25:59,174 --> 00:26:01,975 and, from there, it drops down at 30, 40 degrees 469 00:26:01,977 --> 00:26:05,178 down to about 600 meters water depth. 470 00:26:05,180 --> 00:26:10,017 Then it carries on down to about 2,000 meters water depth. 471 00:26:10,019 --> 00:26:12,853 NARRATOR: Stretching for over 37 miles, 472 00:26:12,855 --> 00:26:14,454 the canyon forms part 473 00:26:14,456 --> 00:26:17,658 of one of the deepest sea channels in the world. 474 00:26:19,862 --> 00:26:25,666 The walls nose-dive over 6,000 feet-- 475 00:26:25,668 --> 00:26:27,701 the depth of the Grand Canyon. 476 00:26:32,541 --> 00:26:35,542 Geologists wonder at the immense geological forces 477 00:26:35,544 --> 00:26:38,545 involved to create such a huge canyon... 478 00:26:41,617 --> 00:26:43,917 ...but also ask themselves, 479 00:26:43,919 --> 00:26:48,255 does it pose a threat to those living on the nearby coast? 480 00:26:52,828 --> 00:26:54,894 Geologists know that landslides 481 00:26:54,896 --> 00:26:57,798 triggered by earthquakes in underwater canyons 482 00:26:57,800 --> 00:27:01,235 can generate lethal tsunamis. 483 00:27:01,237 --> 00:27:05,038 Could the Kaikoura Canyon do the same? 484 00:27:05,040 --> 00:27:09,509 On board the research ship Tangaroa, they investigate. 485 00:27:09,511 --> 00:27:10,744 MAN: Let's try it again, Mitch. 486 00:27:10,746 --> 00:27:13,647 (radio chatter) 487 00:27:13,649 --> 00:27:16,650 NARRATOR: Using Perspex tubes, they gather evidence 488 00:27:16,652 --> 00:27:21,255 from the sedimentary layers on the canyon's floor, 489 00:27:21,257 --> 00:27:25,125 looking for signs of seismic activity in the past. 490 00:27:27,229 --> 00:27:28,195 MAN: Yep. 491 00:27:30,298 --> 00:27:32,466 MAN: This is core two. 492 00:27:32,468 --> 00:27:36,203 NARRATOR: But then, just as they're studying history, 493 00:27:36,205 --> 00:27:38,906 they get the chance to make some. 494 00:27:41,944 --> 00:27:47,214 Midnight, November 14, 2016. 495 00:27:47,216 --> 00:27:48,682 (static) 496 00:27:48,684 --> 00:27:52,085 WOMAN: And we are undergoing a fairly dense earthquake 497 00:27:52,087 --> 00:27:53,687 at the moment, 498 00:27:53,689 --> 00:27:55,021 so, please, just get to somewhere 499 00:27:55,023 --> 00:27:59,426 where you are safely under some protection. 500 00:27:59,428 --> 00:28:01,328 I can honestly say, I doubt that I'll be able 501 00:28:01,330 --> 00:28:04,631 to stay in the chair for much longer. 502 00:28:04,633 --> 00:28:07,234 (alarm) 503 00:28:11,506 --> 00:28:16,110 NARRATOR: The 7.8 magnitude quake rips apart the earth, 504 00:28:16,112 --> 00:28:21,682 creating giant crevices and billions of dollars of damage. 505 00:28:21,684 --> 00:28:27,988 Geologist Joshu Mountjoy has never seen anything like it. 506 00:28:27,990 --> 00:28:29,723 MOUNTJOY: The key thing was that it just covered 507 00:28:29,725 --> 00:28:31,592 such a large geographic area, 508 00:28:31,594 --> 00:28:33,660 and it was right on our coastline. 509 00:28:33,662 --> 00:28:36,530 NARRATOR: The quake rattles the ground for two minutes, 510 00:28:36,532 --> 00:28:38,665 causing thousands of landslides 511 00:28:38,667 --> 00:28:42,135 across 3,800 square miles. 512 00:28:42,137 --> 00:28:45,606 Just north of Kaikoura is the biggest. 513 00:28:45,608 --> 00:28:50,377 800 million cubic feet has shaken to the ground, 514 00:28:50,379 --> 00:28:55,348 exposing a virgin cliff face almost a mile wide. 515 00:28:55,350 --> 00:28:57,217 MOUNTJOY: Grass and tussock we're standing on 516 00:28:57,219 --> 00:28:59,620 was connected to that grass and tussock up there, 517 00:28:59,622 --> 00:29:01,955 and then the whole block slid right down 518 00:29:01,957 --> 00:29:04,357 to bring it down to where it is now, 519 00:29:04,359 --> 00:29:06,360 so this has happened during the earthquake. 520 00:29:06,362 --> 00:29:08,662 We call that co-seismic, and there's actually 521 00:29:08,664 --> 00:29:10,096 a fault line running through here 522 00:29:10,098 --> 00:29:12,733 that runs right down to the coastline. 523 00:29:12,735 --> 00:29:14,201 NARRATOR: The shaking is so severe 524 00:29:14,203 --> 00:29:16,970 that it thrusts the foreshore of Kaikoura 525 00:29:16,972 --> 00:29:21,441 upwards by three feet in just one second. 526 00:29:21,443 --> 00:29:22,376 MOUNTJOY: We're looking at here, 527 00:29:22,378 --> 00:29:23,577 we can see a whole a lot of seaweed 528 00:29:23,579 --> 00:29:25,845 that's stranded above the tide line. 529 00:29:25,847 --> 00:29:26,913 Before the earthquake, 530 00:29:26,915 --> 00:29:30,650 that would have been down below the sea level. 531 00:29:30,652 --> 00:29:33,319 NARRATOR: But Joshu Mountjoy isn't only interested 532 00:29:33,321 --> 00:29:37,057 in how the earthquake tears apart the land. 533 00:29:37,059 --> 00:29:39,526 As soon as the earthquake begins, 534 00:29:39,528 --> 00:29:41,461 he wants to know the effect it's having 535 00:29:41,463 --> 00:29:43,997 deep under the ocean, 536 00:29:43,999 --> 00:29:48,067 in the newly scanned Kaikoura Canyon. 537 00:29:48,069 --> 00:29:52,205 Mountjoy makes contact with the research ship Tangaroa, 538 00:29:52,207 --> 00:29:55,675 which is mapping the very far end of the canyon. 539 00:29:55,677 --> 00:29:57,344 MOUNTJOY: We requested that they divert their energy 540 00:29:57,346 --> 00:30:00,547 to focus on doing some earthquake response. 541 00:30:00,549 --> 00:30:03,883 NARRATOR: That response is to immediately gather core samples 542 00:30:03,885 --> 00:30:07,754 from the floor of the canyon before the dust has settled. 543 00:30:07,756 --> 00:30:08,922 ALAN ORPIN: So, we really had 544 00:30:08,924 --> 00:30:11,758 an unprecedented opportunity to assist. 545 00:30:11,760 --> 00:30:14,561 Well, what, what is the aftermath of a major earthquake? 546 00:30:14,563 --> 00:30:16,597 NARRATOR: If the crew responds in time, 547 00:30:16,599 --> 00:30:19,533 they can achieve a world first, 548 00:30:19,535 --> 00:30:22,502 recording the impact of an earthquake 549 00:30:22,504 --> 00:30:26,240 in a deep-sea canyon as it happens. 550 00:30:29,979 --> 00:30:32,179 NARRATOR: Within minutes of the earthquake, 551 00:30:32,181 --> 00:30:37,484 the crew retrieves precious core samples from the seafloor. 552 00:30:37,486 --> 00:30:39,653 MOUNTJOY: They collected the sedimentary deposit 553 00:30:39,655 --> 00:30:42,055 that had only just happened, so they were boring it 554 00:30:42,057 --> 00:30:45,058 while it was probably still settling out of the ocean. 555 00:30:45,060 --> 00:30:48,461 NARRATOR: And what marine geologist Alan Orpin discovers 556 00:30:48,463 --> 00:30:51,464 is intriguing. 557 00:30:51,466 --> 00:30:53,800 ORPIN: What we found was a very soupy, fluidized mud 558 00:30:53,802 --> 00:30:56,803 that was lying on the seabed. 559 00:30:56,805 --> 00:30:57,738 As we moved south, 560 00:30:57,740 --> 00:31:00,006 what we found was compelling evidence 561 00:31:00,008 --> 00:31:03,777 of core after core for a thickness of material 562 00:31:03,779 --> 00:31:05,679 that had spilled down through the channel. 563 00:31:05,681 --> 00:31:07,613 NARRATOR: The more samples they take, 564 00:31:07,615 --> 00:31:10,017 the clearer the picture becomes. 565 00:31:10,019 --> 00:31:13,286 The shaking of the quake has created a secondary 566 00:31:13,288 --> 00:31:17,291 and truly spectacular undersea upheaval. 567 00:31:17,293 --> 00:31:19,592 MOUNTJOY: No one's ever been able to observe one 568 00:31:19,594 --> 00:31:23,496 of these huge landscape scale canyon-flushing events 569 00:31:23,498 --> 00:31:25,365 to show exactly what effect it had 570 00:31:25,367 --> 00:31:27,167 on the canyon itself. 571 00:31:27,169 --> 00:31:31,505 (music) 572 00:31:31,507 --> 00:31:32,773 NARRATOR: Using the data 573 00:31:32,775 --> 00:31:34,975 gathered by the crew of Tangaroa 574 00:31:34,977 --> 00:31:37,910 and the remarkable drained seascape, 575 00:31:37,912 --> 00:31:39,980 the impact of a large earthquake 576 00:31:39,982 --> 00:31:42,782 on a gigantic underwater canyon 577 00:31:42,784 --> 00:31:48,522 can now be visualized for the very first time. 578 00:31:48,524 --> 00:31:53,393 The seabed shudders ominously as huge tectonic forces 579 00:31:53,395 --> 00:31:55,395 power through the earth's crust. 580 00:31:55,397 --> 00:31:57,464 (rumbling) 581 00:31:57,466 --> 00:32:01,802 This dislodges a top layer of sediment, 582 00:32:01,804 --> 00:32:06,406 becoming a gigantic canyon-flushing landslide. 583 00:32:06,408 --> 00:32:10,877 (rumbling) 584 00:32:10,879 --> 00:32:14,814 (music) 585 00:32:14,816 --> 00:32:17,918 Rock and sediment tumble down the steep walls. 586 00:32:22,091 --> 00:32:27,227 850 million tons of debris roars through the canyon, 587 00:32:27,229 --> 00:32:32,165 gouging 160 feet out of the floor. 588 00:32:32,167 --> 00:32:34,668 MOUNTJOY: There's really like a powder snow avalanche. 589 00:32:36,838 --> 00:32:39,573 The front of it would have a huge amount of energy 590 00:32:39,575 --> 00:32:41,707 moving at about 70 kilometers an hour 591 00:32:41,709 --> 00:32:43,777 and maybe 400 meters high. 592 00:32:47,649 --> 00:32:49,749 It's spreading tens of kilometers 593 00:32:49,751 --> 00:32:52,652 across the ocean floor. 594 00:32:52,654 --> 00:32:56,456 It's just gonna take over everything that's down there. 595 00:32:56,458 --> 00:32:59,326 NARRATOR: The landslide travels with such velocity, 596 00:32:59,328 --> 00:33:02,395 it carves a path across the seafloor 597 00:33:02,397 --> 00:33:07,034 for an astonishing 435 miles. 598 00:33:12,941 --> 00:33:16,609 A landslide of this ferocity has the potential 599 00:33:16,611 --> 00:33:21,882 to generate a tsunami that could devastate Kaikoura. 600 00:33:21,884 --> 00:33:23,917 MOUNTJOY: When a landslide creates a tsunami, 601 00:33:23,919 --> 00:33:27,420 you need a large chunk of material to slide downslope, 602 00:33:27,422 --> 00:33:29,755 and what happens is it's coupled to the water above it 603 00:33:29,757 --> 00:33:31,558 and actually pulls it down with it, 604 00:33:31,560 --> 00:33:32,892 and then, as that water rebounds, 605 00:33:32,894 --> 00:33:35,728 then you create your wave. 606 00:33:35,730 --> 00:33:38,432 NARRATOR: This time, Kaikoura is lucky. 607 00:33:38,434 --> 00:33:42,301 No large objects fall off the canyon rim. 608 00:33:42,303 --> 00:33:45,572 Next time, the town may not be so fortunate. 609 00:33:48,377 --> 00:33:53,580 And the dramatic events of 2016 draw the geologists' attention 610 00:33:53,582 --> 00:33:57,050 to an even bigger tsunami threat nearby. 611 00:33:59,121 --> 00:34:01,387 By continuing to drain the ocean 612 00:34:01,389 --> 00:34:03,990 off the northeast coast of New Zealand, 613 00:34:03,992 --> 00:34:07,327 we can see the reason for their fear. 614 00:34:07,329 --> 00:34:09,963 Lurking just north of the canyon 615 00:34:09,965 --> 00:34:11,197 and frighteningly close 616 00:34:11,199 --> 00:34:15,201 to the New Zealand capital of Wellington-- 617 00:34:15,203 --> 00:34:18,805 the Hikurangi subduction zone, 618 00:34:18,807 --> 00:34:23,910 2,174 miles of seismic trouble. 619 00:34:27,416 --> 00:34:30,950 Geologists recently learned that stress has been building 620 00:34:30,952 --> 00:34:36,423 at its southern end for hundreds of years, 621 00:34:36,425 --> 00:34:39,492 and they believe that the 2016 earthquake 622 00:34:39,494 --> 00:34:42,829 has ratcheted the pressure up even further. 623 00:34:46,234 --> 00:34:48,368 Understanding what's happening here 624 00:34:48,370 --> 00:34:52,872 has become an international priority. 625 00:34:52,874 --> 00:34:55,976 100 ocean floor seismic measuring devices 626 00:34:55,978 --> 00:35:01,314 and support scientists recently arrived from Japan. 627 00:35:01,316 --> 00:35:04,918 They're here to monitor and record the mounting stresses 628 00:35:04,920 --> 00:35:10,123 in the hope of discovering the true danger of Hikurangi. 629 00:35:10,125 --> 00:35:15,061 (music) 630 00:35:15,063 --> 00:35:16,663 Geologists delve deep 631 00:35:16,665 --> 00:35:19,733 into the subduction zone's tectonic past. 632 00:35:22,604 --> 00:35:26,406 And their results are astounding. 633 00:35:26,408 --> 00:35:30,477 It hasn't fractured recently, but deep in its past, 634 00:35:30,479 --> 00:35:35,315 it produced something bigger than anyone had imagined. 635 00:35:35,317 --> 00:35:38,284 Now, using the geologists' data, 636 00:35:38,286 --> 00:35:42,222 it's possible to reconstruct, for the first time, 637 00:35:42,224 --> 00:35:47,760 a tectonic event that reshaped a hemisphere-- 638 00:35:47,762 --> 00:35:51,297 the Ruatoria avalanche. 639 00:35:51,299 --> 00:35:54,634 Just 200 miles from what today is New Zealand's 640 00:35:54,636 --> 00:35:57,837 bustling capital, Wellington, 641 00:35:57,839 --> 00:36:00,974 the epicenter of one of the biggest seismic events 642 00:36:00,976 --> 00:36:03,509 in the history of the earth. 643 00:36:03,511 --> 00:36:05,378 (rumbling) 644 00:36:05,380 --> 00:36:09,649 170,000 years ago, the Australian plate 645 00:36:09,651 --> 00:36:12,652 is bearing down on its Pacific neighbor, 646 00:36:12,654 --> 00:36:15,421 grinding down everything in its path. 647 00:36:15,423 --> 00:36:18,257 Even a towering volcanic cone 648 00:36:18,259 --> 00:36:20,594 six times the volume of Mount Fuji 649 00:36:20,596 --> 00:36:23,163 becomes collateral damage. 650 00:36:26,201 --> 00:36:28,535 The resulting seismic shock 651 00:36:28,537 --> 00:36:31,004 triggers an underwater landslide 652 00:36:31,006 --> 00:36:33,506 on a scale rarely seen. 653 00:36:33,508 --> 00:36:36,109 Moving a swath of broken rock, 654 00:36:36,111 --> 00:36:38,878 the equivalent of three-quarters the size 655 00:36:38,880 --> 00:36:40,947 of the Grand Canyon. 656 00:36:40,949 --> 00:36:41,915 (rumbling) 657 00:36:41,917 --> 00:36:48,221 (rumbling) 658 00:36:48,223 --> 00:36:49,622 MOUNTJOY: So, the Ruatoria avalanche 659 00:36:49,624 --> 00:36:51,891 is the second biggest submarine landslide in the world. 660 00:36:51,893 --> 00:36:54,827 It's absolutely enormous, 3,000 cubic kilometers. 661 00:36:54,829 --> 00:36:56,896 And if you can try and visualize a cubic kilometer, 662 00:36:56,898 --> 00:36:58,497 that's a kilometer high 663 00:36:58,499 --> 00:37:00,567 by a kilometer long by a kilometer wide, 664 00:37:00,569 --> 00:37:02,502 3,000 of them. 665 00:37:02,504 --> 00:37:08,375 (music) 666 00:37:08,377 --> 00:37:11,377 NARRATOR: Nobody knows when the Hikurangi subduction zone 667 00:37:11,379 --> 00:37:14,246 will facture again, 668 00:37:14,248 --> 00:37:15,682 but when it does, 669 00:37:15,684 --> 00:37:19,318 geologists estimate the tsunami wave from the mega-quake 670 00:37:19,320 --> 00:37:21,388 will take only seven minutes 671 00:37:21,390 --> 00:37:24,991 to reach New Zealand's capital city, Wellington, 672 00:37:24,993 --> 00:37:27,027 and its half a million residents. 673 00:37:32,334 --> 00:37:33,933 And such a huge tsunami 674 00:37:33,935 --> 00:37:37,604 wouldn't only impact New Zealand. 675 00:37:37,606 --> 00:37:39,939 There would be an ocean-wide alert 676 00:37:39,941 --> 00:37:42,575 as the waves fan out into the Pacific. 677 00:37:46,147 --> 00:37:49,315 (screaming) 678 00:37:49,317 --> 00:37:51,518 The last time a tsunami on this scale 679 00:37:51,520 --> 00:37:53,986 hit the southern arc of the Ring of Fire 680 00:37:53,988 --> 00:37:58,858 was December 26, 2004, 681 00:37:58,860 --> 00:38:02,662 devastating 14 countries 682 00:38:02,664 --> 00:38:08,234 and killing 230,000 people-- 683 00:38:08,236 --> 00:38:12,405 a terrible reminder of the power of the deadly Pacific. 684 00:38:16,211 --> 00:38:19,111 Continuing to drain away the Pacific Ocean 685 00:38:19,113 --> 00:38:23,115 reveals a very different kind of seismic threat 686 00:38:23,117 --> 00:38:27,153 5,000 miles away, 687 00:38:27,155 --> 00:38:31,123 right next to one of the most densely populated cities 688 00:38:31,125 --> 00:38:32,992 on the planet. 689 00:38:32,994 --> 00:38:36,429 Just 44 miles from bustling Tokyo, 690 00:38:36,431 --> 00:38:38,832 a mysterious underwater feature 691 00:38:38,834 --> 00:38:42,235 has scientists on the edge of their seats. 692 00:38:46,475 --> 00:38:48,474 The island nation of Japan 693 00:38:48,476 --> 00:38:53,413 suffers from its position on the Ring of Fire. 694 00:38:53,415 --> 00:38:55,748 The country accounts for about 20 percent 695 00:38:55,750 --> 00:39:00,487 of the world's earthquakes of magnitude 6 or greater. 696 00:39:00,489 --> 00:39:02,689 Its biggest city, Tokyo, 697 00:39:02,691 --> 00:39:05,291 has been hit by nine mega-earthquakes 698 00:39:05,293 --> 00:39:09,162 in the past 95 years. 699 00:39:09,164 --> 00:39:12,898 But just 44 miles off the city's shoreline, 700 00:39:12,900 --> 00:39:15,034 geologists have recently discovered 701 00:39:15,036 --> 00:39:18,872 a new and very different tectonic troublemaker. 702 00:39:25,847 --> 00:39:31,083 The first discovery is made by scientist Ken Tani. 703 00:39:31,085 --> 00:39:32,585 He's heading out to test 704 00:39:32,587 --> 00:39:37,457 his new underwater remotely operated vehicle, or ROV, 705 00:39:37,459 --> 00:39:40,460 in the waters just off the island of Oshima, 706 00:39:40,462 --> 00:39:42,729 south of Tokyo Bay. 707 00:39:42,731 --> 00:39:47,266 Until now, the waters here have been considered safe passage 708 00:39:47,268 --> 00:39:49,135 for one of the busiest shipping lanes 709 00:39:49,137 --> 00:39:51,070 into the port of Tokyo, 710 00:39:51,072 --> 00:39:55,274 with 400 vessels passing through here every day, 711 00:39:55,276 --> 00:39:58,144 but that is about to change. 712 00:40:05,353 --> 00:40:08,054 NARRATOR: 44 miles from Tokyo Bay, 713 00:40:08,056 --> 00:40:12,926 Ken Tani prepares an underwater survey, using an ROV. 714 00:40:12,928 --> 00:40:16,595 (speaking Japanese) 715 00:40:16,597 --> 00:40:19,999 Passing over a rocky mound on the seafloor, 716 00:40:20,001 --> 00:40:23,536 he discovers something extraordinary, 717 00:40:23,538 --> 00:40:26,806 a seismic beast that has lain hidden 718 00:40:26,808 --> 00:40:31,277 for hundreds of thousands of years. 719 00:40:31,279 --> 00:40:36,215 Using Ken Tani's own data, draining away the Pacific Ocean 720 00:40:36,217 --> 00:40:39,219 reveals what is lurking below the waves. 721 00:40:47,495 --> 00:40:49,629 As the water recedes, 722 00:40:49,631 --> 00:40:54,767 it exposes a large flat plateau. 723 00:40:54,769 --> 00:40:56,202 Near its center, 724 00:40:56,204 --> 00:40:59,272 what looks like an ordinary hole in the seafloor. 725 00:41:02,010 --> 00:41:06,846 But on closer inspection, the frightening truth emerges. 726 00:41:06,848 --> 00:41:10,550 It's the vent of an undersea volcano. 727 00:41:12,854 --> 00:41:14,654 Thousands of years ago, 728 00:41:14,656 --> 00:41:17,123 it very likely had a towering cone, 729 00:41:17,125 --> 00:41:20,727 but erosion and wave action has worn it down, 730 00:41:20,729 --> 00:41:23,363 which is why no one discovered it before. 731 00:41:25,667 --> 00:41:30,603 But is it as dormant as it appears? 732 00:41:30,605 --> 00:41:34,040 Ken wastes no time in exploring the crater. 733 00:41:34,042 --> 00:41:36,142 KEN TANI: So, that's the sea surface. 734 00:41:36,144 --> 00:41:38,278 NARRATOR: Testing the water temperature around the outlet 735 00:41:38,280 --> 00:41:40,680 with a submarine thermometer, 736 00:41:40,682 --> 00:41:44,117 and what he finds surprises everyone. 737 00:42:02,871 --> 00:42:09,108 (music) 738 00:42:09,110 --> 00:42:11,644 NARRATOR: The smoldering undersea volcano 739 00:42:11,646 --> 00:42:13,912 is named Oomurodashi, 740 00:42:13,914 --> 00:42:18,484 44 miles south of Tokyo, 741 00:42:18,486 --> 00:42:21,787 placing at risk the lives of thousands of mariners 742 00:42:21,789 --> 00:42:23,556 in the shipping lanes above. 743 00:42:26,527 --> 00:42:31,330 In 1952, an underwater volcano like Oomurodashi 744 00:42:31,332 --> 00:42:35,335 erupts 260 miles south of Tokyo. 745 00:42:35,337 --> 00:42:38,537 Super-heated magma reacts with water 746 00:42:38,539 --> 00:42:42,342 to produce what's called a phreatomagmatic explosion, 747 00:42:42,344 --> 00:42:46,412 an underwater steam bomb. 748 00:42:46,414 --> 00:42:49,949 A nearby ship is engulfed in the explosion, 749 00:42:49,951 --> 00:42:52,485 killing all 31 on board. 750 00:43:07,635 --> 00:43:09,635 NARRATOR: A stirring volcanic giant 751 00:43:09,637 --> 00:43:12,972 is not just a danger to shipping. 752 00:43:12,974 --> 00:43:16,208 A major eruption could send tsunami waves 753 00:43:16,210 --> 00:43:21,347 racing towards Tokyo, population 38 million. 754 00:43:29,524 --> 00:43:30,923 NARRATOR: Ken decides he needs 755 00:43:30,925 --> 00:43:33,660 to keep Oomurodashi under surveillance. 756 00:43:35,797 --> 00:43:38,931 Nothing happens for five years. 757 00:43:38,933 --> 00:43:42,535 Then, when he returns to gather fresh samples, 758 00:43:42,537 --> 00:43:46,372 Oomurodashi has another unpleasant surprise for him. 759 00:43:48,643 --> 00:43:50,943 Returning to the drained ocean floor 760 00:43:50,945 --> 00:43:54,680 reveals his next shocking discovery. 761 00:43:54,682 --> 00:43:56,949 In addition to the crater, 762 00:43:56,951 --> 00:44:00,686 five more volcanic cones. 763 00:44:00,688 --> 00:44:05,491 That's five more possible outlets for the volcano. 764 00:44:05,493 --> 00:44:10,563 Only one is currently active, but all could become so. 765 00:44:10,565 --> 00:44:13,966 And if the volcano keeps growing, 766 00:44:13,968 --> 00:44:17,369 Oomurodashi could become an even greater threat 767 00:44:17,371 --> 00:44:19,305 by breaking the surface 768 00:44:19,307 --> 00:44:21,941 and spewing toxic ash into the sky. 769 00:44:24,245 --> 00:44:29,182 Active volcanos can do this astonishingly quickly. 770 00:44:29,184 --> 00:44:33,386 It took Nishinoshima, Japan's latest volcanic island, 771 00:44:33,388 --> 00:44:34,987 just two years to grow 772 00:44:34,989 --> 00:44:39,992 from a flat-topped, underwater summit 773 00:44:39,994 --> 00:44:45,064 to this tectonic monster, 774 00:44:45,066 --> 00:44:49,869 measuring one square mile and 443 feet high. 775 00:44:51,672 --> 00:44:52,738 But Nishinoshima 776 00:44:52,740 --> 00:44:55,608 is nearly 600 miles from Tokyo. 777 00:44:55,610 --> 00:44:59,278 Oomurodashi is only 44. 778 00:45:00,381 --> 00:45:02,081 Once out of the water, 779 00:45:02,083 --> 00:45:04,350 any major eruption of Oomurodashi 780 00:45:04,352 --> 00:45:09,555 could shower Tokyo in choking volcanic ash. 781 00:45:09,557 --> 00:45:13,125 Despite the dangers, Ken Tani and his team 782 00:45:13,127 --> 00:45:16,562 continue to monitor Oomurodashi. 783 00:45:16,564 --> 00:45:19,865 Any increase in the volcano's activity 784 00:45:19,867 --> 00:45:22,101 could signal impending disaster 785 00:45:22,103 --> 00:45:26,572 for the thousands living on nearby islands 786 00:45:26,574 --> 00:45:30,643 and threaten the safety of millions in nearby Tokyo. 787 00:45:33,181 --> 00:45:34,980 Draining the Ring of Fire 788 00:45:34,982 --> 00:45:39,518 has revealed hidden geological wonders 789 00:45:39,520 --> 00:45:41,787 and terrors, 790 00:45:41,789 --> 00:45:44,790 exposing new evidence of this immense power 791 00:45:44,792 --> 00:45:47,660 of plate tectonics 792 00:45:47,662 --> 00:45:52,331 and its ability to create 793 00:45:52,333 --> 00:45:53,933 and destroy.