1 00:00:03,127 --> 00:00:09,396 Earth, a 4.5- Billion-year-old planet, still evolving. 2 00:00:10,767 --> 00:00:18,367 As continents shift and clash, volcanoes erupt, glaciers grow and recede, 3 00:00:18,367 --> 00:00:22,327 the Earth's crust is carved in countless, fascinating ways, 4 00:00:22,327 --> 00:00:25,842 leaving a trail of geological mysteries behind. 5 00:00:27,687 --> 00:00:33,247 This is the story of Hawaii, a mountain chain over 80 million years old 6 00:00:33,247 --> 00:00:37,684 and home to the most active volcano in the world. 7 00:00:39,607 --> 00:00:41,847 In this exquisite, volatile landscape, 8 00:00:41,847 --> 00:00:45,567 scientists hunt for clues to the islands' origins - 9 00:00:45,567 --> 00:00:48,327 clues that may shed new light 10 00:00:48,327 --> 00:00:51,603 on the formation of the Earth itself. 11 00:00:57,647 --> 00:00:58,927 Hawaii. 12 00:00:58,927 --> 00:01:01,647 The most isolated group of islands on Earth, 13 00:01:01,647 --> 00:01:06,323 stretching 1,500 miles across the middle of the Pacific Ocean. 14 00:01:07,327 --> 00:01:08,927 These eight tropical islands 15 00:01:08,927 --> 00:01:12,367 are one of the youngest geological formations on the planet. 16 00:01:12,367 --> 00:01:20,407 With stunning beaches, huge canyons and the biggest volcanoes on Earth, 17 00:01:20,407 --> 00:01:24,798 this is where paradise meets hell. 18 00:01:27,527 --> 00:01:32,767 The investigation into how Hawaii was formed began in 1934. 19 00:01:32,767 --> 00:01:37,407 Dutch geophysicist Felix Meinesz invented the gravimeter, 20 00:01:37,407 --> 00:01:41,527 an incredible machine which enabled scientists to accurately measure gravity 21 00:01:41,527 --> 00:01:43,165 for the first time. 22 00:01:44,887 --> 00:01:46,887 With his cutting-edge technology, 23 00:01:46,887 --> 00:01:50,447 Meinesz was able to calculate the gravitational forces at work 24 00:01:50,447 --> 00:01:54,599 on the Big Island and, using this data, determine its size. 25 00:01:56,687 --> 00:02:00,887 His results revealed that the Big Island was like a gigantic iceberg. 26 00:02:00,887 --> 00:02:03,767 Only its tip was visible above the ocean. 27 00:02:03,767 --> 00:02:07,767 But drain away the water and its true size is remarkable. 28 00:02:07,767 --> 00:02:10,207 The island is twice the height of Everest, 29 00:02:10,207 --> 00:02:15,361 and so massive that Everest could fit inside it 140 times. 30 00:02:20,647 --> 00:02:24,087 Geologist Mike Poland heads to the top of the mountain Mauna Kea, 31 00:02:24,087 --> 00:02:29,002 the highest point on the Big Island, to get a sense of its true enormity. 32 00:02:31,127 --> 00:02:33,847 We're standing at the top of Mauna Kea volcano, 33 00:02:33,847 --> 00:02:36,047 which is the tallest mountain in the world. 34 00:02:36,047 --> 00:02:38,927 It's 13,796 feet above sea level, 35 00:02:38,927 --> 00:02:41,687 but it goes all the way down to the ocean floor 36 00:02:41,687 --> 00:02:45,362 and ends up being about 56,000 feet high. 37 00:02:46,647 --> 00:02:50,207 This giant island is the largest in the United States 38 00:02:50,207 --> 00:02:53,279 and bigger than all the other Hawaiian islands put together. 39 00:02:54,767 --> 00:02:58,287 Intrigued, scientists set out to discover what could have created 40 00:02:58,287 --> 00:03:01,040 such a huge land mass. 41 00:03:03,127 --> 00:03:07,647 10,000 feet below the peak of Mauna Kea and 70 miles to the south, 42 00:03:07,647 --> 00:03:14,837 the prime suspect is plain to see - the awesome Kilauea volcano. 43 00:03:16,407 --> 00:03:18,767 POLAND: We like to call Kilauea the most active volcano in the world 44 00:03:18,767 --> 00:03:21,647 because it's been erupting continuously since 1983. 45 00:03:21,647 --> 00:03:25,162 And it's been going every day, almost nonstop, since that time. 46 00:03:26,207 --> 00:03:28,687 Since early 2008, it's been even more active, 47 00:03:28,687 --> 00:03:30,727 'cause now we have this summit eruption as well, 48 00:03:30,727 --> 00:03:35,437 so now Kilauea's perhaps by two times the most active volcano in the world. 49 00:03:37,487 --> 00:03:40,047 But this volcano is not predictable. 50 00:03:40,047 --> 00:03:43,767 Although the summit is no longer spewing out lava, 51 00:03:43,767 --> 00:03:49,125 12 miles down on the south flank of the volcano is an active vent. 52 00:03:53,967 --> 00:03:57,567 For the last 25 years, lava has been gushing 53 00:03:57,567 --> 00:04:02,402 out of the side of the volcano from this vent, with no signs of stopping. 54 00:04:07,287 --> 00:04:12,281 Homes, towns and forests are swallowed up by scorching hot lava. 55 00:04:13,607 --> 00:04:18,807 With each new flow, layer upon layer of black crust builds, 56 00:04:18,807 --> 00:04:21,924 covering the island in volcanic rock. 57 00:04:24,047 --> 00:04:29,075 Could this huge island have been built entirely by lava? 58 00:04:30,767 --> 00:04:35,807 Experts needed to figure out exactly how much lava Kilauea produces. 59 00:04:35,807 --> 00:04:40,287 Their first clue can be found all over the volcano. 60 00:04:40,287 --> 00:04:44,127 Clinging to the rocks are yellow crystals. 61 00:04:44,127 --> 00:04:47,607 These are sulfur crystals and tell scientists 62 00:04:47,607 --> 00:04:53,364 that Kilauea volcano is releasing vast amounts of sulfur dioxide gas. 63 00:04:54,607 --> 00:04:57,887 To determine just how much the volcano is producing, 64 00:04:57,887 --> 00:05:00,242 researchers take regular measurements. 65 00:05:01,807 --> 00:05:06,367 The amount of sulfur dioxide that effervesces from the magma 66 00:05:06,367 --> 00:05:10,207 is tied directly to the amount of magma that's coming out of the ground, 67 00:05:10,207 --> 00:05:11,807 the amount of lava that's erupted. 68 00:05:11,807 --> 00:05:14,647 So by measuring the amount of sulfur dioxide, 69 00:05:14,647 --> 00:05:20,438 we can use that number to calculate how much lava is being erupted. 70 00:05:21,807 --> 00:05:25,436 These samples reveal staggering results. 71 00:05:27,007 --> 00:05:32,527 Kilauea could be producing 100 million cubic yards of lava a year, 72 00:05:32,527 --> 00:05:35,167 more than any volcano on Earth. 73 00:05:35,167 --> 00:05:38,847 But there isn't this much lava flowing across the surface. 74 00:05:38,847 --> 00:05:41,447 So where does the rest of it go? 75 00:05:41,447 --> 00:05:44,727 Geologists ventured below the surface, 76 00:05:44,727 --> 00:05:48,037 into the guts of the volcano, to investigate. 77 00:05:49,527 --> 00:05:53,327 Stretching 400 feet into the dark is a strange tunnel, 78 00:05:53,327 --> 00:05:55,447 just like a subway tunnel. 79 00:05:55,447 --> 00:05:57,887 But it's not a manmade structure. 80 00:05:57,887 --> 00:06:01,327 It's part of a vast network of tubes 81 00:06:01,327 --> 00:06:05,479 that hold the key to how much lava moves around the island. 82 00:06:06,607 --> 00:06:10,287 We're standing in Thurston Lava Tube in Hawaii Volcanoes National Park, 83 00:06:10,287 --> 00:06:13,127 and this lava tube was one of the main conduits for lava 84 00:06:13,127 --> 00:06:16,047 that was flowing from Kilauea summit to the sea 85 00:06:16,047 --> 00:06:18,647 in an eruption that occurred about 500 years ago. 86 00:06:18,647 --> 00:06:20,847 So once this tube system has been established, 87 00:06:20,847 --> 00:06:23,007 you essentially have an underground river of lava. 88 00:06:23,007 --> 00:06:25,767 So these tube systems can be very long-lived 89 00:06:25,767 --> 00:06:27,723 and very efficient delivery systems for lava. 90 00:06:30,687 --> 00:06:34,760 The lava is so hot it burns a channel into the rocks beneath it. 91 00:06:37,287 --> 00:06:41,647 This incredible time-lapse footage shows that, because the top of the flow 92 00:06:41,647 --> 00:06:46,527 is still exposed to the air, it cools and crusts over. 93 00:06:46,527 --> 00:06:52,477 Below this crust, a tunnel forms, through which the lava continues to flow. 94 00:06:53,487 --> 00:06:57,480 But how much lava can these tubes carry? 95 00:07:00,607 --> 00:07:02,087 Back on the surface, 96 00:07:02,087 --> 00:07:06,956 Dr Ken Hon is carefully inspecting the lava fields to find an active tube. 97 00:07:07,967 --> 00:07:14,805 Only inches beneath his feet could be a tunnel full of 2,000 degree lava. 98 00:07:16,927 --> 00:07:22,047 Dr Hon is on the lookout for a skylight, a window in the ceiling of a tube. 99 00:07:22,047 --> 00:07:27,407 They can come and go within days and are a sure sign of an active lava tube. 100 00:07:27,407 --> 00:07:30,887 You can see the lava glowing inside the lava tube. 101 00:07:30,887 --> 00:07:35,127 This one's about ten to 15 feet wide and probably about five feet deep. 102 00:07:35,127 --> 00:07:39,678 And it's about 2,000 degrees Fahrenheit, and it glows like the Sun. 103 00:07:40,807 --> 00:07:44,447 These hidden tunnels keep the lava insulated and hot, 104 00:07:44,447 --> 00:07:47,727 preventing it from cooling and turning into solid rock, 105 00:07:47,727 --> 00:07:52,198 enabling it to travel further and faster than lava on the surface. 106 00:07:53,447 --> 00:07:57,887 What we're looking at is on the order of about five cubic yards every second 107 00:07:57,887 --> 00:08:00,407 going in this lava tube underneath us. 108 00:08:00,407 --> 00:08:04,087 And that's the equivalent of about a dump truck worth of lava 109 00:08:04,087 --> 00:08:06,567 every two seconds, so if I was standing on the freeway, 110 00:08:06,567 --> 00:08:09,127 what you would see is one dump truck after another dump truck 111 00:08:09,127 --> 00:08:11,607 after another dump truck going by me here, 112 00:08:11,607 --> 00:08:14,519 transporting a phenomenal amount of material. 113 00:08:16,287 --> 00:08:19,367 Hundreds of these expressways crisscross the island, 114 00:08:19,367 --> 00:08:22,487 carrying lava underground up to 30 miles 115 00:08:22,487 --> 00:08:25,763 until it reaches its inevitable destination... 116 00:08:27,727 --> 00:08:29,718 ...the ocean. 117 00:08:43,087 --> 00:08:48,161 And when 2,000 degree lava meets seawater, the results are spectacular. 118 00:08:57,487 --> 00:09:01,287 This interaction is key to how the Big Island was created 119 00:09:01,287 --> 00:09:03,118 and is continually growing. 120 00:09:04,327 --> 00:09:05,927 When the lava hits the ocean, 121 00:09:05,927 --> 00:09:10,967 it's extremely hot and it shatters into lots of little pieces, 122 00:09:10,967 --> 00:09:14,755 so what it does is leave a lot of black sand behind it. 123 00:09:16,647 --> 00:09:19,407 Layer upon layer of this black sandy rubble 124 00:09:19,407 --> 00:09:24,561 slowly piles up on the ocean floor until it forms a new beach. 125 00:09:25,967 --> 00:09:28,647 New lava on the surface runs across this beach, 126 00:09:28,647 --> 00:09:35,287 cooling slowly to form a new piece of solid land on sandy foundations. 127 00:09:35,287 --> 00:09:39,565 This massive island is built on piles of loose rubble. 128 00:09:40,967 --> 00:09:44,801 We're looking right here at the process by which the Hawaiian islands grow. 129 00:09:46,807 --> 00:09:50,047 The Big Island is the fastest growing piece of land on Earth, 130 00:09:50,047 --> 00:09:55,287 as lava from Kilauea adds 20 football fields a year to its already colossal size. 131 00:09:55,287 --> 00:09:58,247 But this just isn't enough. 132 00:09:58,247 --> 00:10:03,767 More lava is needed to build this huge island, so just where is it coming from? 133 00:10:03,767 --> 00:10:06,407 The clues are in the landscape itself. 134 00:10:06,407 --> 00:10:09,447 While Kilauea forms only one peak on the island, 135 00:10:09,447 --> 00:10:12,837 four other megastructures tower over the landscape. 136 00:10:16,207 --> 00:10:19,367 Over a million years ago, there was no Big Island of Hawaii. 137 00:10:19,367 --> 00:10:22,647 It started as a very small island, which was the volcano of Kohala, 138 00:10:22,647 --> 00:10:24,327 which grew out of the ocean. 139 00:10:24,327 --> 00:10:27,007 Over time, more volcanoes started to grow, 140 00:10:27,007 --> 00:10:30,527 Mauna Kea and Hualalai came next, growing into tremendous mountains. 141 00:10:30,527 --> 00:10:32,407 Mauna Loa was the next volcano to grow. 142 00:10:32,407 --> 00:10:36,685 And Kilauea is the youngest of the Big Island's volcanoes. 143 00:10:38,087 --> 00:10:41,527 Over a million years, lava from these five volcanoes 144 00:10:41,527 --> 00:10:45,247 slowly built the Big Island up from the sea floor. 145 00:10:45,247 --> 00:10:50,924 The biggest island in the United States is one big volcanic rock. 146 00:10:58,087 --> 00:11:01,047 The mystery of how Hawaii was made is slowly unravelling 147 00:11:01,047 --> 00:11:04,403 as the evidence emerges from its fiery volcanoes. 148 00:11:06,167 --> 00:11:11,127 Experiments in the 1930s revealed that the Big Island is a vast structure, 149 00:11:11,127 --> 00:11:14,327 stretching three miles down to the sea floor. 150 00:11:14,327 --> 00:11:19,367 Readings of sulfur dioxide gas show that Kilauea produces more lava 151 00:11:19,367 --> 00:11:21,597 than any other volcano on Earth. 152 00:11:23,087 --> 00:11:28,957 The landscape reveals that lava from five volcanoes built the island. 153 00:11:30,487 --> 00:11:33,207 The Big Island of Hawaii is a stunning wilderness 154 00:11:33,207 --> 00:11:36,047 dominated by fire and destruction. 155 00:11:36,047 --> 00:11:40,847 But what force on Earth could create the most active volcano in the world, 156 00:11:40,847 --> 00:11:45,875 2,000 miles from the nearest land, in the middle of the Pacific? 157 00:11:52,887 --> 00:11:56,926 Hawaii is filled with evidence of a volcanic past. 158 00:11:58,767 --> 00:12:02,555 The eight islands are made up of 15 mammoth volcanoes. 159 00:12:03,607 --> 00:12:05,927 Molokai boasts two huge mountains, 160 00:12:05,927 --> 00:12:11,167 the Big Island is dominated by the giant Mauna Loa, and in Honolulu, 161 00:12:11,167 --> 00:12:15,638 houses are crowded around the now extinct Diamond Head crater. 162 00:12:16,807 --> 00:12:22,367 Geologists had figured out that the Big Island was created by five volcanoes. 163 00:12:22,367 --> 00:12:27,122 Next, they wanted to know how the entire chain had come into existence. 164 00:12:30,727 --> 00:12:35,596 7,000 miles away, off the coast of Indonesia, is the mighty Krakatoa. 165 00:12:41,247 --> 00:12:43,607 Ever since it exploded in 1883, 166 00:12:43,607 --> 00:12:45,927 scientists have been trying to understand 167 00:12:45,927 --> 00:12:48,441 the forces that create volcanoes. 168 00:12:51,807 --> 00:12:56,167 Experts plotted all the active volcanoes in the world on a map, 169 00:12:56,167 --> 00:12:58,158 and an extraordinary fact emerged. 170 00:12:59,487 --> 00:13:04,367 80% lay around the edge of the Pacific Ocean. 171 00:13:04,367 --> 00:13:08,967 This long line of volcanoes became known as the Ring of Fire. 172 00:13:08,967 --> 00:13:13,167 452 giant volcanoes make up the ring, 173 00:13:13,167 --> 00:13:18,719 and it is thought that eruptions began in this area over 36 million years ago. 174 00:13:24,647 --> 00:13:26,807 During the 1950s and '60s, 175 00:13:26,807 --> 00:13:31,847 a theory emerged that finally began to make sense of these fire mountains. 176 00:13:31,847 --> 00:13:34,487 Geologists realised that the Earth's crust 177 00:13:34,487 --> 00:13:37,567 was made up of eight major and many minor plates, 178 00:13:37,567 --> 00:13:41,247 fitting together like a giant jigsaw puzzle. 179 00:13:41,247 --> 00:13:43,887 They move relative to one another, sometimes they intersect, 180 00:13:43,887 --> 00:13:46,047 sometimes they diverge. 181 00:13:46,047 --> 00:13:49,087 These plate boundaries are where we see most geologic activity. 182 00:13:49,087 --> 00:13:52,247 For example, along the Pacific Ring of Fire, 183 00:13:52,247 --> 00:13:54,367 where there's lots of volcanoes and earthquakes, 184 00:13:54,367 --> 00:13:56,961 that marks plate boundary locations. 185 00:13:58,927 --> 00:14:01,407 The theory was called subduction. 186 00:14:01,407 --> 00:14:06,127 When tectonic plates collide, the heavier oceanic plate is forced down 187 00:14:06,127 --> 00:14:10,047 into the Earth's intensely hot interior, taking water with it. 188 00:14:10,047 --> 00:14:13,287 The water forces magma to swirl up and push through the plate, 189 00:14:13,287 --> 00:14:15,960 where it forms volcanoes. 190 00:14:18,527 --> 00:14:20,927 But when geologists looked at the volcanoes of Hawaii, 191 00:14:20,927 --> 00:14:23,767 it was clear the theory didn't fit. 192 00:14:23,767 --> 00:14:26,807 They couldn't have been created as the plates collided, 193 00:14:26,807 --> 00:14:30,641 because they sit 2,000 miles from the nearest boundary. 194 00:14:35,207 --> 00:14:37,527 Here in Hawaii, we're in the middle of a plate, 195 00:14:37,527 --> 00:14:39,887 so we wouldn't expect to see that much activity. 196 00:14:39,887 --> 00:14:43,207 That's another bit of evidence that there's got to be some anomaly here 197 00:14:43,207 --> 00:14:47,644 that's causing all of the melting we see in the middle of this large plate. 198 00:14:49,087 --> 00:14:52,727 Puzzled, geologists decided to look at the volcanoes of Hawaii 199 00:14:52,727 --> 00:14:54,767 in the hope they might give up their secrets. 200 00:14:54,767 --> 00:14:58,327 But all they found were more differences. 201 00:14:58,327 --> 00:15:01,167 Most of the world's volcanoes are cone-shaped, 202 00:15:01,167 --> 00:15:04,567 with steep sides many thousands of feet tall, 203 00:15:04,567 --> 00:15:07,923 but Hawaii's volcanoes look completely different. 204 00:15:10,727 --> 00:15:14,007 We call these volcanoes shield volcanoes because of their shape. 205 00:15:14,007 --> 00:15:15,967 If you're looking behind me at Mauna Loa, 206 00:15:15,967 --> 00:15:18,447 it's got these very smooth sloping flanks, 207 00:15:18,447 --> 00:15:21,200 it's like a warrior's shield that's been put on its end. 208 00:15:23,407 --> 00:15:26,727 Digging deeper, geologists decided to test the lava 209 00:15:26,727 --> 00:15:28,647 and found that Hawaiian volcanoes 210 00:15:28,647 --> 00:15:32,047 produce a distinct type of lava called basalt. 211 00:15:32,047 --> 00:15:37,447 Basalt lava is made of rocks which have been heated up to 2,000 degrees. 212 00:15:37,447 --> 00:15:41,767 Not only is it the hottest lava in the world, it's also some of the most fluid, 213 00:15:41,767 --> 00:15:44,767 and this makes it terrifyingly unpredictable. 214 00:15:44,767 --> 00:15:47,087 MAN: We gotta get outta here! 215 00:15:47,087 --> 00:15:48,566 Get outta here! 216 00:15:49,767 --> 00:15:52,967 The lava that erupts here in Hawaii is very runny. 217 00:15:52,967 --> 00:15:55,487 It's much runnier than the kind of lavas that erupt 218 00:15:55,487 --> 00:15:58,206 from places like Mount Rainier or Mount St Helens, which is much stickier. 219 00:15:59,447 --> 00:16:02,200 It's like comparing honey to toothpaste. 220 00:16:04,167 --> 00:16:08,087 It's this difference in the consistency of the lava that gives Hawaii's volcanoes 221 00:16:08,087 --> 00:16:10,442 their dramatically different shape. 222 00:16:11,607 --> 00:16:14,047 The sides of the volcanoes here are gently sloping 223 00:16:14,047 --> 00:16:17,483 because those lava flows can just run out as they need to. 224 00:16:19,847 --> 00:16:24,007 And the lava flows at places like Mount Rainier and Mount St Helens, 225 00:16:24,007 --> 00:16:26,327 being very sticky, stay close to the volcano 226 00:16:26,327 --> 00:16:28,238 and build up very steep-sided volcanic cones. 227 00:16:35,927 --> 00:16:38,847 Geologists had uncovered crucial evidence, 228 00:16:38,847 --> 00:16:43,007 but they still did not understand what kind of force could create volcanoes 229 00:16:43,007 --> 00:16:47,683 in the middle of a plate 2,000 miles from the nearest boundary. 230 00:16:51,767 --> 00:16:56,287 But whatever that force turned out to be, it would have to be enormous. 231 00:16:56,287 --> 00:16:59,085 Big enough to quite literally move a mountain. 232 00:17:00,247 --> 00:17:03,207 At the summit of the Big Island's Kilauea volcano, 233 00:17:03,207 --> 00:17:07,607 Dr Mike Poland is using sophisticated global positioning equipment 234 00:17:07,607 --> 00:17:10,167 to measure changes in the volcano's size. 235 00:17:12,967 --> 00:17:16,607 GPS is a tool for locating yourself anywhere on the surface of the Earth. 236 00:17:16,607 --> 00:17:19,687 You may be familiar with this from seeing GPS units in cars. 237 00:17:19,687 --> 00:17:23,487 This is a different type of GPS, it's much more accurate. 238 00:17:23,487 --> 00:17:25,967 And that allows us to see how the ground is moving 239 00:17:25,967 --> 00:17:27,447 in centimetre-level scales. 240 00:17:27,447 --> 00:17:31,087 This cutting-edge technology is crucial to scientists 241 00:17:31,087 --> 00:17:35,000 in their struggle to understand the forces working beneath Hawaii. 242 00:17:36,447 --> 00:17:38,367 So we've got this GPS set-up here, 243 00:17:38,367 --> 00:17:41,647 we also have a GPS set-up on the far side of the caldera. 244 00:17:41,647 --> 00:17:43,327 Now, by looking at how the distance 245 00:17:43,327 --> 00:17:45,527 between those GPS stations is changing, 246 00:17:45,527 --> 00:17:48,847 we can get an idea of whether or not the volcano is inflating or deflating. 247 00:17:48,847 --> 00:17:50,487 If it's inflating like a balloon, 248 00:17:50,487 --> 00:17:52,647 it means that there's magma that's accumulating 249 00:17:52,647 --> 00:17:54,527 beneath the surface, and if it's deflating, 250 00:17:54,527 --> 00:17:57,727 it may mean that there's magma that's leaving the subsurface. 251 00:17:57,727 --> 00:18:00,687 And over the past years, actually, these stations have gotten farther apart 252 00:18:00,687 --> 00:18:02,287 from one another by almost a foot. 253 00:18:02,287 --> 00:18:06,047 The kind of force necessary to inflate the volcano, 254 00:18:06,047 --> 00:18:08,967 to spread the caldera wider by one foot, is tremendous, 255 00:18:08,967 --> 00:18:12,447 and it's a very good sign of magma that's accumulating beneath the surface 256 00:18:12,447 --> 00:18:14,244 and may be getting ready to erupt. 257 00:18:22,407 --> 00:18:25,807 Evidence was mounting that a huge and unexplained force 258 00:18:25,807 --> 00:18:27,763 was at work beneath the chain. 259 00:18:28,767 --> 00:18:32,407 The volcanoes of Hawaii do not emerge from a plate boundary, 260 00:18:32,407 --> 00:18:36,127 but rise up right in the middle of the Pacific Plate. 261 00:18:36,127 --> 00:18:38,767 Hawaii's lava is dramatically different 262 00:18:38,767 --> 00:18:42,157 to that produced by the rest of the volcanoes in the Pacific. 263 00:18:43,167 --> 00:18:47,087 The islands of Hawaii were a thorn in the side of geology. 264 00:18:47,087 --> 00:18:49,287 But, although they remained an unexplained mystery, 265 00:18:49,287 --> 00:18:51,927 geologists weren't about to give up. 266 00:18:51,927 --> 00:18:55,087 And the answers they would find were so incredible 267 00:18:55,087 --> 00:18:59,524 that the debate they created still rages to this day. 268 00:19:02,927 --> 00:19:08,365 The puzzle of what created the islands of Hawaii seemed impossible to solve. 269 00:19:09,727 --> 00:19:12,887 The mystery only deepened when, in the 1950s, 270 00:19:12,887 --> 00:19:16,163 the U.S. Navy mapped the ocean floor with sonar. 271 00:19:19,127 --> 00:19:23,327 They revealed a series of underwater mountains, known as seamounts, 272 00:19:23,327 --> 00:19:27,764 that extended far beyond the chain of eight Hawaiian islands. 273 00:19:28,967 --> 00:19:33,447 To the northwest are a whole string of sea mountains we call seamounts. 274 00:19:33,447 --> 00:19:36,447 Those are sunken volcanic mountains, 275 00:19:36,447 --> 00:19:38,487 many of them with reefs on top of them. 276 00:19:38,487 --> 00:19:42,487 Over 80 seamounts and 19 islands form this sequence, 277 00:19:42,487 --> 00:19:46,367 known as the Hawaiian-Emperor seamount chain. 278 00:19:46,367 --> 00:19:50,647 BLAY: You're looking at a total distance from the Big Island of Hawaii 279 00:19:50,647 --> 00:19:56,927 out to Midway and all the way up to Russia of about 3,200 miles, 280 00:19:56,927 --> 00:19:59,567 it's one of the longest mountain chains in the world, 281 00:19:59,567 --> 00:20:01,876 but very little of it is above sea level. 282 00:20:08,487 --> 00:20:13,807 In 1963, Canadian geologist J. Tuzo Wilson turned his attentions 283 00:20:13,807 --> 00:20:16,162 to the Hawaiian islands. 284 00:20:17,527 --> 00:20:21,967 He was struck by the fact that both the Hawaiian islands and seamounts 285 00:20:21,967 --> 00:20:26,404 form a straight line that courses through the middle of the Pacific. 286 00:20:27,407 --> 00:20:32,927 Straight lines are incredibly rare in nature, they don't occur by accident, 287 00:20:32,927 --> 00:20:38,367 especially not a line over 3,000 miles long. 288 00:20:38,367 --> 00:20:42,007 Wilson believed that one single force must have created 289 00:20:42,007 --> 00:20:45,477 this vast chain of volcanic islands and seamounts. 290 00:20:49,127 --> 00:20:54,407 Wilson also made a very simple and yet incredibly astute deduction. 291 00:20:54,407 --> 00:20:57,567 The further the islands of Hawaii were from the Big Island, 292 00:20:57,567 --> 00:21:00,167 the greener they got. 293 00:21:00,167 --> 00:21:03,007 And for Wilson, greener meant older. 294 00:21:03,007 --> 00:21:08,167 He noticed that the landscape on the Big Island is like a black desert, 295 00:21:08,167 --> 00:21:13,127 a barren wilderness with only a few seedlings peeping through the lava. 296 00:21:13,127 --> 00:21:18,599 Fresh lava flows regularly scorch the earth, killing any plant life. 297 00:21:20,367 --> 00:21:25,807 But move north along the chain, and the islands become increasingly green. 298 00:21:25,807 --> 00:21:29,327 Wilson believed that on each successive island, 299 00:21:29,327 --> 00:21:32,687 more time has passed since the last eruption, 300 00:21:32,687 --> 00:21:34,678 allowing more plants to grow. 301 00:21:36,447 --> 00:21:39,727 Two years later, using radiometric techniques, 302 00:21:39,727 --> 00:21:43,207 scientists dated rock samples from each of the islands. 303 00:21:43,207 --> 00:21:45,687 Their results confirmed Wilson's hunch 304 00:21:45,687 --> 00:21:48,759 and proved that the islands increased in age. 305 00:21:56,207 --> 00:21:59,687 Dr Poland has been collecting some of these rock samples 306 00:21:59,687 --> 00:22:01,996 and has brought them to the Big Island. 307 00:22:03,647 --> 00:22:06,687 This rock right here is from the lava flow that we're standing on, 308 00:22:06,687 --> 00:22:08,927 this is one of the youngest rocks on the island. 309 00:22:08,927 --> 00:22:11,887 And, in fact, we could go and pick up some lava that formed yesterday 310 00:22:11,887 --> 00:22:13,286 if it weren't too hot. 311 00:22:16,727 --> 00:22:19,327 If we move down to the middle of the chain, we get this rock here 312 00:22:19,327 --> 00:22:20,967 which is from Oahu, 313 00:22:20,967 --> 00:22:23,686 and this is about 3.5 million years old. 314 00:22:27,327 --> 00:22:30,567 This rock here is from a lava flow on the island of Kauai, 315 00:22:30,567 --> 00:22:33,567 it's from the island that's the farthest away from where we are today 316 00:22:33,567 --> 00:22:35,047 on the Big Island. 317 00:22:35,047 --> 00:22:38,567 You notice how dull it is, that's because it is very old, 318 00:22:38,567 --> 00:22:40,444 it's about five million years old. 319 00:22:46,167 --> 00:22:48,887 Wilson pulled together evidence from rock dating 320 00:22:48,887 --> 00:22:51,327 and the straight line forged by the islands 321 00:22:51,327 --> 00:22:53,447 and came up with a single theory. 322 00:22:53,447 --> 00:22:57,927 He proposed that Hawaii was created by something called a hotspot, 323 00:22:57,927 --> 00:23:01,527 an exceptionally hot region beneath the Earth's crust 324 00:23:01,527 --> 00:23:04,687 that was concentrated under Hawaii's Big Island. 325 00:23:04,687 --> 00:23:09,047 As the Pacific Plate moved slowly over this hotspot, 326 00:23:09,047 --> 00:23:14,075 the immense heat punched through the crust to form a chain of volcanic islands. 327 00:23:15,487 --> 00:23:19,247 So this hot spot is a... a constant and stationary source of heat 328 00:23:19,247 --> 00:23:20,927 beneath the Earth's surface, 329 00:23:20,927 --> 00:23:24,007 it's like a blowtorch pointed up at the surface of the Earth. 330 00:23:24,007 --> 00:23:28,127 And as the Earth's surface moves over that blowtorch, it punches through, 331 00:23:28,127 --> 00:23:30,727 creating a chain of islands and undersea mountains, 332 00:23:30,727 --> 00:23:32,797 and that's what we're seeing in Hawaii today. 333 00:23:38,167 --> 00:23:41,607 This theory was a geological masterstroke. 334 00:23:41,607 --> 00:23:45,007 It didn't just explain how Hawaii was created, 335 00:23:45,007 --> 00:23:47,647 it also confirmed one of the most radical theories 336 00:23:47,647 --> 00:23:49,087 of the 20th century, 337 00:23:49,087 --> 00:23:52,204 the theory of plate tectonics. 338 00:23:54,567 --> 00:23:58,447 Here, at last, was evidence that the vast lumbering plates 339 00:23:58,447 --> 00:24:01,245 that made up the Earth were moving. 340 00:24:02,807 --> 00:24:07,287 Tuzo Wilson's hotspot theory changed our understanding of our planet forever, 341 00:24:07,287 --> 00:24:13,362 but it also left behind a controversy that still rages to this day. 342 00:24:14,967 --> 00:24:18,039 How was the hotspot created? 343 00:24:19,327 --> 00:24:23,087 POLAND: Ever since scientists understood that volcanism in Hawaii 344 00:24:23,087 --> 00:24:26,047 was driven by this hotspot, the question then became, 345 00:24:26,047 --> 00:24:28,247 well, what drives the hotspot? 346 00:24:28,247 --> 00:24:30,238 What causes the hotspot? 347 00:24:32,007 --> 00:24:35,567 On the barren slopes of Mauna Kea on the Big Island, 348 00:24:35,567 --> 00:24:37,523 Mike Poland has found a clue. 349 00:24:38,687 --> 00:24:41,847 So what we're looking at here is what we call a xenolith, 350 00:24:41,847 --> 00:24:45,887 it's basically a foreign piece of rock that's trapped in this lava flow. 351 00:24:45,887 --> 00:24:49,087 It's where this foreign piece of rock 352 00:24:49,087 --> 00:24:52,127 has come from that's truly startling. 353 00:24:52,127 --> 00:24:54,327 The green mineral you're seeing in this xenolith here 354 00:24:54,327 --> 00:24:56,087 is a mineral called olivine, 355 00:24:56,087 --> 00:24:58,327 and it really indicates that this chunk here came from someplace 356 00:24:58,327 --> 00:25:00,522 very deep within the Earth. 357 00:25:01,687 --> 00:25:05,885 Olivine is usually found hundreds of miles beneath the surface. 358 00:25:06,887 --> 00:25:08,927 Its presence here is good evidence 359 00:25:08,927 --> 00:25:12,687 that the hotspot is powered by something deep within the Earth. 360 00:25:12,687 --> 00:25:15,567 And in the 1970s, 361 00:25:15,567 --> 00:25:19,447 American geologists finally came up with a groundbreaking theory. 362 00:25:19,447 --> 00:25:24,207 They theorised that below the hotspot lies a plume of hot rock, 363 00:25:24,207 --> 00:25:27,247 which rises up through the Earth's interior. 364 00:25:27,247 --> 00:25:30,327 Two or three hundred miles below the surface, 365 00:25:30,327 --> 00:25:33,444 it starts to spread out, forming a huge dome. 366 00:25:34,607 --> 00:25:37,997 The very top of this is the hotspot. 367 00:25:42,007 --> 00:25:46,159 Scientists called this phenomenon a mantle plume. 368 00:25:48,327 --> 00:25:50,687 No-one really knows how deep it goes, 369 00:25:50,687 --> 00:25:54,167 but some scientists have come to the extraordinary conclusion 370 00:25:54,167 --> 00:25:58,843 that it may stretch all the way down to the very core of our planet. 371 00:25:59,847 --> 00:26:01,887 It is possible that the plume extends 372 00:26:01,887 --> 00:26:04,367 all the way down to the core-mantle boundary, 373 00:26:04,367 --> 00:26:06,607 and frankly, that makes good sense to me, 374 00:26:06,607 --> 00:26:09,075 if you look at the size of the Hawaiian island chain. 375 00:26:15,527 --> 00:26:19,047 It's a huge feature, it's been around for tens of millions of years. 376 00:26:19,047 --> 00:26:21,647 To me, that's not something that can be explained by something 377 00:26:21,647 --> 00:26:23,207 that's just near the surface, 378 00:26:23,207 --> 00:26:26,279 I think it's got to be something quite deep within the Earth. 379 00:26:28,007 --> 00:26:31,927 Suddenly, experts realised plumes were the answer to hundreds 380 00:26:31,927 --> 00:26:35,047 of geological mysteries, which had long puzzled science, 381 00:26:35,047 --> 00:26:37,925 such as the existence of Icelandic volcanoes... 382 00:26:40,727 --> 00:26:42,683 ...the Galapagos Islands, 383 00:26:44,207 --> 00:26:47,199 ...and the vast Yellowstone supervolcano. 384 00:26:48,687 --> 00:26:53,807 An investigation, begun in Hawaii, transformed scientists' understanding, 385 00:26:53,807 --> 00:26:58,085 not just of the island chain but of the entire planet. 386 00:27:02,887 --> 00:27:06,887 Rock dating and the unusually straight alignment of the island chain 387 00:27:06,887 --> 00:27:11,407 revealed that the Pacific Plate is moving over a stationary hotspot. 388 00:27:11,407 --> 00:27:16,847 Olivine rock erupted on Hawaii's Big Island shows this hotspot is powered 389 00:27:16,847 --> 00:27:21,367 by a mantle plume originating from the very bowels of the Earth. 390 00:27:21,367 --> 00:27:25,727 But while the Hawaiian islands have been created by this very hotspot, 391 00:27:25,727 --> 00:27:30,323 another, equally powerful, force is working to destroy them. 392 00:27:35,287 --> 00:27:38,438 In Hawaii, a strange force is at work. 393 00:27:39,447 --> 00:27:43,607 While the Big Island is growing by 11,000 square feet a year, 394 00:27:43,607 --> 00:27:49,007 the islands at the northern end of the chain are vanishing into the Pacific 395 00:27:49,007 --> 00:27:53,603 at a rate of 2,400 square feet a year. 396 00:27:55,567 --> 00:27:58,923 These islands are disappearing fast. 397 00:28:00,367 --> 00:28:05,202 Geologists were curious about what force could cause them to vanish. 398 00:28:11,647 --> 00:28:15,167 They found their first clue in early scientific studies. 399 00:28:15,167 --> 00:28:19,527 1950s underwater sea mapping produced a wealth of data, 400 00:28:19,527 --> 00:28:22,883 and these results revealed something completely unexpected. 401 00:28:25,287 --> 00:28:29,807 Heat and pressure from the hotspot had forced up the ocean floor, 402 00:28:29,807 --> 00:28:35,404 creating a bulge 750 miles long and 500 feet high. 403 00:28:37,047 --> 00:28:42,167 The chain is raised by the swell, but as the islands move away from the hotspot, 404 00:28:42,167 --> 00:28:47,082 they slide off the swollen crust, sinking further and further. 405 00:28:49,007 --> 00:28:52,967 Eventually, as they move northward at about eight to ten centimetres, 406 00:28:52,967 --> 00:28:55,727 that's about three and a half inches, per year... 407 00:28:55,727 --> 00:29:00,887 So in, say, another, um, one to two million years, this island 408 00:29:00,887 --> 00:29:05,407 will probably be as much as three to 4,000 feet lower, 409 00:29:05,407 --> 00:29:11,084 probably have relatively little freshwater on it and not be very inhabitable. 410 00:29:13,487 --> 00:29:17,605 The hotspot that created the islands also seals their fate. 411 00:29:20,327 --> 00:29:24,727 But the islands aren't just sinking, they're shrinking too. 412 00:29:24,727 --> 00:29:26,367 Erosion is the culprit. 413 00:29:26,367 --> 00:29:28,887 It's slowly destroying the islands, 414 00:29:28,887 --> 00:29:31,207 and nowhere is this more apparent than on Kauai, 415 00:29:31,207 --> 00:29:33,198 the oldest island of Hawaii. 416 00:29:35,767 --> 00:29:38,567 Here, along the coastline, intense weathering may have produced 417 00:29:38,567 --> 00:29:41,847 some of the most breathtaking natural features in the world, 418 00:29:41,847 --> 00:29:45,635 but it is also evidence of the island's inherent flaw. 419 00:29:46,927 --> 00:29:50,567 And erosion isn't just taking place at the coast. 420 00:29:50,567 --> 00:29:52,603 It's happening all over the island. 421 00:29:55,927 --> 00:29:58,407 (BIRDS CRYING) 422 00:29:58,407 --> 00:30:01,727 Waimea Canyon, Hawaii's Grand Canyon, 423 00:30:01,727 --> 00:30:05,127 a ten-mile scar through Kauai's green wilderness. 424 00:30:05,127 --> 00:30:10,047 Over 3,000 feet deep, this canyon is the most dramatic example 425 00:30:10,047 --> 00:30:11,446 of erosion in Hawaii. 426 00:30:17,207 --> 00:30:20,407 If you look up to the east, you'll see one of the rainiest places in the world, 427 00:30:20,407 --> 00:30:22,567 Mount Waialeale. 428 00:30:22,567 --> 00:30:26,845 Rain flows from that mountain down into the canyon. 429 00:30:31,247 --> 00:30:35,487 Mount Waialeale receives over 400 inches of rain every year, 430 00:30:35,487 --> 00:30:39,526 which pours out over the island, carving out the canyon. 431 00:30:43,207 --> 00:30:48,407 But the islands are made of basalt lava, one of the hardest rocks on Earth. 432 00:30:48,407 --> 00:30:52,567 How could water alone be wearing them away? 433 00:30:52,567 --> 00:30:57,847 The answer lies in the canyon's spectacular red walls. 434 00:30:57,847 --> 00:31:02,367 The reddish colour is from the oxidation of the mineral iron, 435 00:31:02,367 --> 00:31:06,567 which makes up about 10 to 12% of the lava rock here. 436 00:31:06,567 --> 00:31:11,207 It's very similar to the rust that forms on your car. 437 00:31:11,207 --> 00:31:14,727 So, literally, we're looking at a highly rusted landscape, if you will, 438 00:31:14,727 --> 00:31:16,207 which makes it very soft. 439 00:31:16,207 --> 00:31:19,836 So, in a sense, it's, uh, somewhat rotten. 440 00:31:20,887 --> 00:31:24,407 Exposed to water, the high level of iron in this lava 441 00:31:24,407 --> 00:31:26,967 causes the rock to rust and crumble. 442 00:31:26,967 --> 00:31:29,727 It's the paradox of the Hawaiian islands. 443 00:31:29,727 --> 00:31:34,087 They're made of volcanic basalt, one of nature's hardest rocks, 444 00:31:34,087 --> 00:31:36,247 but it's fatally flawed. 445 00:31:36,247 --> 00:31:40,407 This, uh, rock, which, uh, initially was, uh, very dense, hard lava 446 00:31:40,407 --> 00:31:42,367 you could barely break with a hammer, 447 00:31:42,367 --> 00:31:45,803 we can now actually pull out pieces with our hand. 448 00:31:49,527 --> 00:31:53,327 Combine this crumbling rock with some of the highest rainfall in the world, 449 00:31:53,327 --> 00:31:57,445 and the result is massive erosion over millions of years. 450 00:31:58,447 --> 00:32:01,487 But scientists knew that erosion alone 451 00:32:01,487 --> 00:32:03,796 couldn't be causing the islands to disappear. 452 00:32:09,487 --> 00:32:11,127 On the island of Molokai, 453 00:32:11,127 --> 00:32:14,327 they found evidence that vast tracts of land had disappeared, 454 00:32:14,327 --> 00:32:17,125 not over millions of years, but overnight. 455 00:32:19,967 --> 00:32:21,527 Satellite images revealed 456 00:32:21,527 --> 00:32:25,407 that Molokai is not like the other round islands of Hawaii. 457 00:32:25,407 --> 00:32:27,567 Something strange happened to Molokai, 458 00:32:27,567 --> 00:32:29,842 it's quite obvious just by looking at any map. 459 00:32:31,607 --> 00:32:34,447 It's not a round volcano, part of it is missing. 460 00:32:34,447 --> 00:32:40,886 It's a thin strip of land with sharp cliff edges, shorn away into steep faces. 461 00:32:42,327 --> 00:32:47,527 At 1,700 feet, these are the highest sea cliffs in the world. 462 00:32:47,527 --> 00:32:50,758 All the evidence pointed to a sudden cataclysmic event. 463 00:32:51,807 --> 00:32:55,567 Many theories were put forward, but it wasn't until the 1980s 464 00:32:55,567 --> 00:32:58,967 that geologists got the evidence they desperately needed. 465 00:32:58,967 --> 00:33:01,967 After the success of earlier underwater mapping, 466 00:33:01,967 --> 00:33:06,847 the U.S. Navy returned to Hawaii with the world's most advanced sonar system 467 00:33:06,847 --> 00:33:10,487 and surveyed the surrounding waters in incredible detail. 468 00:33:10,487 --> 00:33:13,807 They discovered the seabed on the island's north side 469 00:33:13,807 --> 00:33:16,967 was littered with gigantic underwater blocks of land, 470 00:33:16,967 --> 00:33:19,967 some larger than the island of Manhattan. 471 00:33:19,967 --> 00:33:24,407 Geologists took thousands of samples and measured the blocks. 472 00:33:24,407 --> 00:33:27,001 What they found was incredible. 473 00:33:28,367 --> 00:33:31,607 These blocks could be fitted back to the island's steep cliffs 474 00:33:31,607 --> 00:33:34,487 like a giant jigsaw puzzle. 475 00:33:34,487 --> 00:33:38,007 Finally, scientists had enough evidence to put together a picture 476 00:33:38,007 --> 00:33:39,759 of what had happened. 477 00:33:40,847 --> 00:33:43,567 Radiometric dating confirmed the age of the blocks 478 00:33:43,567 --> 00:33:46,647 and showed that they were the result of an event which had taken place 479 00:33:46,647 --> 00:33:48,727 over a million years ago. 480 00:33:48,727 --> 00:33:54,279 Geologists knew there could only be one explanation - a massive landslide. 481 00:33:55,287 --> 00:33:58,247 One and a half million years ago, um, 482 00:33:58,247 --> 00:34:00,477 there was a very bad day in the Hawaiian islands. 483 00:34:01,967 --> 00:34:06,327 The entire north slope of the island slipped off into the ocean, 484 00:34:06,327 --> 00:34:10,847 a section 25 miles long and perhaps as much as a mile thick, 485 00:34:10,847 --> 00:34:12,838 and it did it all at once. 486 00:34:15,127 --> 00:34:18,887 This huge section of the island crashed into the ocean, 487 00:34:18,887 --> 00:34:22,323 splitting into massive blocks weighing millions of tons. 488 00:34:25,807 --> 00:34:30,127 The force with which they crashed into the waves meant they didn't stop dead 489 00:34:30,127 --> 00:34:35,247 but continued to move along the ocean floor at an incredible speed. 490 00:34:35,247 --> 00:34:37,087 It was sudden, it was dramatic, 491 00:34:37,087 --> 00:34:40,807 and we know that because of how far the blocks went, 492 00:34:40,807 --> 00:34:44,167 they... they went down into this trough around the Hawaiian islands 493 00:34:44,167 --> 00:34:45,727 and then up the other side 494 00:34:45,727 --> 00:34:49,687 and eventually stopped about 200 miles away. 495 00:34:49,687 --> 00:34:54,327 And for them to go that far means they had to be travelling about 150, 496 00:34:54,327 --> 00:34:58,087 160 miles an hour, really fast, 497 00:34:58,087 --> 00:35:00,727 and of course, it's displacing water while it's doing that, 498 00:35:00,727 --> 00:35:04,687 so you're creating for the Hawaiian islands a huge tsunami, 499 00:35:04,687 --> 00:35:08,157 a tsunami that would have reached to the top of the cliffs behind me. 500 00:35:13,247 --> 00:35:16,887 A landslide on this scale and at this speed would have produced 501 00:35:16,887 --> 00:35:22,767 one of the most awesome and deadly waves ever seen on the planet. 502 00:35:22,767 --> 00:35:25,567 The main event was over in only five minutes, 503 00:35:25,567 --> 00:35:29,927 and, uh, and I'm afraid that, if you saw that, it would be too late, 504 00:35:29,927 --> 00:35:32,567 because, yeah, you could run as hard as you like 505 00:35:32,567 --> 00:35:36,196 and you wouldn't get away from the subsequent... the subsequent tsunami. 506 00:35:37,887 --> 00:35:42,278 But what could have caused such catastrophic land failure? 507 00:35:43,407 --> 00:35:47,366 Geologists look to the youngest island, the Big Island, for answers. 508 00:35:48,927 --> 00:35:53,127 Here the island is still building, just as Molokai once did, 509 00:35:53,127 --> 00:35:57,727 and experts suspect they will find their answer in the island's foundations. 510 00:35:57,727 --> 00:35:59,767 As the new land builds out, 511 00:35:59,767 --> 00:36:03,927 it's building on sand that's deposited in front of the lava flows 512 00:36:03,927 --> 00:36:06,007 and so it's very unstable. 513 00:36:06,007 --> 00:36:10,287 And every once in a while, this material collapses, leaves the lava unsupported, 514 00:36:10,287 --> 00:36:13,327 and it breaks and it slides down into the ocean. 515 00:36:13,327 --> 00:36:15,927 It was a disturbing discovery. 516 00:36:15,927 --> 00:36:20,767 All Hawaii's islands were built rapidly and entirely from lava. 517 00:36:20,767 --> 00:36:24,567 They are all based on the same weak foundations. 518 00:36:24,567 --> 00:36:27,604 And that means a landslide could strike anywhere. 519 00:36:31,247 --> 00:36:33,527 On the south coast of the Big Island, 520 00:36:33,527 --> 00:36:38,287 there's evidence that another major landslide could be about to occur. 521 00:36:38,287 --> 00:36:44,207 A huge tear in the Earth points to where a 4,700 square mile chunk of land 522 00:36:44,207 --> 00:36:50,247 is breaking away from the Big Island at a rate of four inches a year. 523 00:36:50,247 --> 00:36:55,807 For its size, this is the fastest moving tract of land on the planet. 524 00:36:55,807 --> 00:36:59,447 Geologists have calculated that if it were to fall into the ocean, 525 00:36:59,447 --> 00:37:02,847 it could trigger an earthquake up to magnitude seven 526 00:37:02,847 --> 00:37:05,407 and unleash a colossal tsunami. 527 00:37:05,407 --> 00:37:09,967 All the cities of Hawaii would be swept away as a mammoth wave 528 00:37:09,967 --> 00:37:13,403 races towards the California coast. 529 00:37:18,087 --> 00:37:22,007 Investigators have discovered why Hawaii is disappearing. 530 00:37:22,007 --> 00:37:26,807 Sonar maps reveal the islands are sliding off a swollen section 531 00:37:26,807 --> 00:37:29,207 of the Earth's crust. 532 00:37:29,207 --> 00:37:32,927 Kauai's crumbling landscape reveals an inherent flaw in the islands. 533 00:37:32,927 --> 00:37:36,407 They are made of the hardest rock on Earth, but exposed to water, 534 00:37:36,407 --> 00:37:38,247 they rapidly break down. 535 00:37:38,247 --> 00:37:41,727 And Molokai's dramatic cliffs, shorn away overnight, 536 00:37:41,727 --> 00:37:45,083 are evidence of catastrophic landslides. 537 00:37:46,087 --> 00:37:49,127 Sinking, eroding and crashing into the Pacific, 538 00:37:49,127 --> 00:37:53,367 eventually, even the Big Island will be just another underwater mountain 539 00:37:53,367 --> 00:37:57,327 in the long chain hidden beneath the waves. 540 00:37:57,327 --> 00:38:00,327 But the story of Hawaii is far from over. 541 00:38:00,327 --> 00:38:02,647 Rumblings from under the sea tell scientists 542 00:38:02,647 --> 00:38:05,927 a new monster may be rising from the waves. 543 00:38:05,927 --> 00:38:11,087 Now they must venture into one of the most hostile environments on Earth, 544 00:38:11,087 --> 00:38:13,396 where fire meets water. 545 00:38:17,767 --> 00:38:23,127 The story of Hawaii is an incredible tale of giant volcanoes, 546 00:38:23,127 --> 00:38:30,687 unimaginable catastrophe and vanishing islands, but it doesn't end here. 547 00:38:30,687 --> 00:38:34,647 Because, only 20 miles off the Big Island's beaches, 548 00:38:34,647 --> 00:38:38,686 something strange is stirring in the depths. 549 00:38:41,327 --> 00:38:44,727 In the 1950s, sea floor surveys revealed 550 00:38:44,727 --> 00:38:48,800 that an underwater volcano sat right on the flanks of the Big Island. 551 00:38:50,087 --> 00:38:52,967 Geologists were intrigued by this giant seamount 552 00:38:52,967 --> 00:38:58,087 rising up two miles from the ocean floor, and named it Loihi. 553 00:38:58,087 --> 00:39:00,247 Scientists were desperate to learn more. 554 00:39:00,247 --> 00:39:04,007 But it wasn't until 40 years later, when the technology became available, 555 00:39:04,007 --> 00:39:07,287 that they were able to dive down and investigate the seamount. 556 00:39:07,287 --> 00:39:09,727 MAN: The scientists were very interested to go down 557 00:39:09,727 --> 00:39:12,127 and actually see what the situation was, 558 00:39:12,127 --> 00:39:15,567 so they took the research submarine Alvin, 559 00:39:15,567 --> 00:39:17,447 which is the very famous three-person sub 560 00:39:17,447 --> 00:39:19,167 that found the Titanic, 561 00:39:19,167 --> 00:39:21,167 and they went down to the seamount 562 00:39:21,167 --> 00:39:25,927 and found that there was a huge pile of volcanic rocks 563 00:39:25,927 --> 00:39:27,927 that were all freshly broken. 564 00:39:27,927 --> 00:39:33,160 And here's a sample, this is a very heavy rock, and it's a top of a pillow lava. 565 00:39:34,207 --> 00:39:37,916 Pillow lava was evidence of a very recent eruption. 566 00:39:44,007 --> 00:39:47,847 Scientists had believed Loihi to be an ancient volcano, 567 00:39:47,847 --> 00:39:50,047 extinct for thousands of years. 568 00:39:50,047 --> 00:39:53,847 But this discovery called for some radical rethinking. 569 00:39:53,847 --> 00:39:57,442 Could Loihi be alive and erupting? 570 00:39:58,727 --> 00:40:03,287 Experts struggled for 11 years to find indisputable proof, 571 00:40:03,287 --> 00:40:07,167 mapping the seamount extensively and taking thousands of samples, 572 00:40:07,167 --> 00:40:10,567 until, finally, they came across the piece of evidence 573 00:40:10,567 --> 00:40:13,007 they had been searching for. 574 00:40:13,007 --> 00:40:17,398 Now it wasn't until 1996 that, really, the smoking gun was discovered. 575 00:40:20,527 --> 00:40:24,767 In October that year, there was a huge number of seismic events 576 00:40:24,767 --> 00:40:28,207 occurring that the people at the Volcano Observatory discovered, 577 00:40:28,207 --> 00:40:30,927 but they quickly realised that the source of the seismic activity 578 00:40:30,927 --> 00:40:34,527 was not on the island here, it was offshore. 579 00:40:34,527 --> 00:40:36,607 They did the best estimates they could 580 00:40:36,607 --> 00:40:39,767 and it all pointed to this seamount off the south end of the Big Island. 581 00:40:39,767 --> 00:40:43,767 This swarm of earthquakes coming from Loihi 582 00:40:43,767 --> 00:40:48,807 were the largest number ever recorded from any Hawaiian volcano. 583 00:40:48,807 --> 00:40:53,207 Scientists knew they were on the verge of an incredible discovery. 584 00:40:53,207 --> 00:40:55,687 Desperate to witness the action as it happened, 585 00:40:55,687 --> 00:40:58,527 scientists rushed to the heart of the activity. 586 00:40:58,527 --> 00:41:01,883 The trick was to get out there while the eruption was occurring. 587 00:41:07,047 --> 00:41:11,247 So we went out there, there was a tremendous amount of seismic activity. 588 00:41:11,247 --> 00:41:15,126 From the ship you could actually hear the noise of the earthquake. 589 00:41:16,127 --> 00:41:20,047 Venturing into the unknown, a team from the University of Hawaii 590 00:41:20,047 --> 00:41:21,967 dived 3,000 feet down 591 00:41:21,967 --> 00:41:26,007 into this dangerous and unpredictable environment. 592 00:41:26,007 --> 00:41:30,125 Everywhere you could see were mounds of broken-up rock. 593 00:41:31,687 --> 00:41:35,396 In this murky water was this precipice. 594 00:41:36,407 --> 00:41:40,887 The top of the seamount had suddenly collapsed to create this pit crater 595 00:41:40,887 --> 00:41:43,527 that was hundreds of feet across and hundreds of feet deep, 596 00:41:43,527 --> 00:41:48,806 and this was the first evidence for really active volcanic activity. 597 00:41:49,807 --> 00:41:53,287 Experts had just missed one of the most violent eruptions 598 00:41:53,287 --> 00:41:56,847 Hawaii had ever seen, but, as the dust settled, 599 00:41:56,847 --> 00:41:59,919 they were able to survey the aftermath. 600 00:42:01,287 --> 00:42:04,087 Lava had poured out of the volcano, 601 00:42:04,087 --> 00:42:07,284 draining the summit and causing it to collapse. 602 00:42:12,887 --> 00:42:16,967 The team finally had proof that Loihi was an active volcano, 603 00:42:16,967 --> 00:42:21,727 which will continue to erupt and grow until it forms a new island, 604 00:42:21,727 --> 00:42:24,924 the next in the Hawaiian chain. 605 00:42:27,647 --> 00:42:30,407 The assumption was there had to be another volcano coming up 606 00:42:30,407 --> 00:42:32,607 one of these days. 607 00:42:32,607 --> 00:42:36,167 No-one knew whether that was gonna happen in our lifetime or not, 608 00:42:36,167 --> 00:42:39,807 but it's very rewarding for the scientists to realise 609 00:42:39,807 --> 00:42:42,847 that now the next volcano in the sequence has been discovered - 610 00:42:42,847 --> 00:42:45,202 Loihi is apparently it. 611 00:42:46,687 --> 00:42:50,567 As lava continues to spew from its submerged summit, 612 00:42:50,567 --> 00:42:54,247 Loihi will build until it rises out of the Pacific. 613 00:42:54,247 --> 00:42:59,047 The Pacific Plate will shift, carrying the Big Island off the hotspot, 614 00:42:59,047 --> 00:43:03,040 and Loihi will take its place at the head of the Hawaiian chain. 615 00:43:05,247 --> 00:43:09,527 Experts had studied the ancient islands of Hawaii for hundreds of years, 616 00:43:09,527 --> 00:43:11,807 theorising about how they were created. 617 00:43:11,807 --> 00:43:15,247 But they never imagined they would have the opportunity 618 00:43:15,247 --> 00:43:17,602 to witness it for themselves. 619 00:43:19,647 --> 00:43:23,927 Loihi provides us with a real unique laboratory. 620 00:43:23,927 --> 00:43:26,687 It gives us a window back into the past. 621 00:43:26,687 --> 00:43:28,967 This is our one chance to see how it worked 622 00:43:28,967 --> 00:43:32,004 before the islands reached the surface. 623 00:43:35,727 --> 00:43:37,287 Reviewing all the evidence, 624 00:43:37,287 --> 00:43:42,167 investigators finally understand how the Hawaiian chain was created. 625 00:43:42,167 --> 00:43:45,127 Gravity readings taken in the 1930s 626 00:43:45,127 --> 00:43:49,847 show that the Big Island is 140 times bigger than Mount Everest. 627 00:43:49,847 --> 00:43:53,887 Further investigation reveals that it is made entirely from basalt lava 628 00:43:53,887 --> 00:43:56,607 from five volcanoes. 629 00:43:56,607 --> 00:44:00,807 Rocks created deep underground are found within the lava 630 00:44:00,807 --> 00:44:04,247 and show the island's volcanoes are fuelled by something 631 00:44:04,247 --> 00:44:07,080 from deep within the Earth, a mantle plume. 632 00:44:08,247 --> 00:44:13,727 But high levels of iron in Hawaii's basalt lava cause the islands to crumble. 633 00:44:13,727 --> 00:44:18,323 And the steep cliffs of Molokai are evidence of mega landslides. 634 00:44:19,647 --> 00:44:23,767 Underwater lava is proof that a new volcano is stirring - 635 00:44:23,767 --> 00:44:25,687 the next island in the chain 636 00:44:25,687 --> 00:44:29,236 that will eventually emerge from beneath the waves. 637 00:44:32,047 --> 00:44:35,087 Hawaii's dramatic cycle of birth and death 638 00:44:35,087 --> 00:44:37,687 is more than just a geological wonder. 639 00:44:37,687 --> 00:44:40,647 It's transformed geologists' understanding 640 00:44:40,647 --> 00:44:42,647 of the entire planet. 641 00:44:42,647 --> 00:44:46,407 On Hawaii, we can see for ourselves 642 00:44:46,407 --> 00:44:49,080 how the Earth is made.