1 00:00:01,100 --> 00:00:03,133 ♪ ♪ 2 00:00:04,866 --> 00:00:08,300 (thunder crashing) 3 00:00:08,300 --> 00:00:11,000 NARRATOR: In January 2022, 4 00:00:11,000 --> 00:00:13,300 the volcano Hunga Tonga- Hunga Ha'apai 5 00:00:13,300 --> 00:00:17,200 produces the most explosive eruption ever recorded. 6 00:00:17,200 --> 00:00:20,333 (volcano erupting, people exclaiming) 7 00:00:20,333 --> 00:00:22,500 MOANA PAEA: It was so massive! 8 00:00:22,500 --> 00:00:24,533 Threw all of us on the ground! 9 00:00:24,533 --> 00:00:25,766 MAN: Look, look! 10 00:00:25,766 --> 00:00:29,266 BRANKO SUGAR: Suddenly, I can see a wall 11 00:00:29,266 --> 00:00:31,233 of white water coming fast. 12 00:00:31,233 --> 00:00:33,366 MAN: Here! PAEA: And I just screamed, 13 00:00:33,366 --> 00:00:34,566 "It's a tsunami!" 14 00:00:34,566 --> 00:00:36,566 SUGAR: Everyone, life jackets! 15 00:00:36,566 --> 00:00:38,833 Get your life jackets! 16 00:00:38,833 --> 00:00:40,266 SUGAR: I accepted the fact 17 00:00:40,266 --> 00:00:42,500 that we had three minutes left to live. 18 00:00:42,500 --> 00:00:47,533 (waves crashing, people crying) 19 00:00:49,400 --> 00:00:51,366 (people exclaiming) 20 00:00:51,366 --> 00:00:54,000 NARRATOR: Waves as high as 60 feet 21 00:00:54,000 --> 00:00:56,366 devastate the Pacific nation of Tonga. 22 00:00:58,233 --> 00:00:59,933 Now... 23 00:00:59,933 --> 00:01:01,433 Running away! 24 00:01:01,433 --> 00:01:03,600 NARRATOR: ...a team of scientists tries to solve 25 00:01:03,600 --> 00:01:04,866 the mysteries of this disaster. 26 00:01:04,866 --> 00:01:06,933 TAANIELA KULA: This is a turning point 27 00:01:06,933 --> 00:01:08,400 to how we understand the world. 28 00:01:08,400 --> 00:01:11,866 NARRATOR: Can they reconstruct the key events... 29 00:01:11,866 --> 00:01:13,033 The wave came from behind us 30 00:01:13,033 --> 00:01:15,400 and took out these columns. 31 00:01:15,400 --> 00:01:18,733 NARRATOR: ...and answer the critical question, 32 00:01:18,733 --> 00:01:21,766 could it happen again? 33 00:01:21,766 --> 00:01:23,400 SHANE CRONIN: Everything that we've discovered today 34 00:01:23,400 --> 00:01:25,833 is absolutely new, 35 00:01:25,833 --> 00:01:27,700 and I think will be a quite a shock. 36 00:01:27,700 --> 00:01:33,600 NARRATOR: "Hidden Volcano Abyss," right now, on "NOVA." 37 00:01:33,600 --> 00:01:38,300 ♪ ♪ 38 00:01:51,566 --> 00:01:54,066 (man speaking on radio) 39 00:01:54,066 --> 00:01:57,633 SUGAR: We were going spearfishing, just like we do now. 40 00:01:57,633 --> 00:02:02,800 Me, my son, and the boys. 41 00:02:02,800 --> 00:02:05,266 (man speaking on radio) 42 00:02:05,266 --> 00:02:07,433 The volcano's been erupting forever. 43 00:02:07,433 --> 00:02:10,766 Every five minutes, for months. 44 00:02:10,766 --> 00:02:13,666 But no big eruption, just... 45 00:02:13,666 --> 00:02:16,200 Just nice ones, beautiful to see. 46 00:02:16,200 --> 00:02:19,466 We could see it from here. 47 00:02:19,466 --> 00:02:24,000 It was nothing out of the ordinary. 48 00:02:24,000 --> 00:02:26,300 And then we see the mushroom was kind of getting bigger. 49 00:02:26,300 --> 00:02:27,666 Look, look! 50 00:02:27,666 --> 00:02:29,600 It just happened in a couple of minutes, that is... 51 00:02:29,600 --> 00:02:31,500 MAN 2: How quick it's spreading. MAN 1: Wow. 52 00:02:31,500 --> 00:02:35,100 So the boys want to stop and take some photos. 53 00:02:35,100 --> 00:02:37,400 I said, "Ah, yeah, okay." 54 00:02:37,400 --> 00:02:39,166 So I stopped the boat right here. 55 00:02:39,166 --> 00:02:45,600 ♪ ♪ 56 00:02:45,600 --> 00:02:46,600 MAN: Whoo! 57 00:02:46,600 --> 00:02:48,300 (all laughing) 58 00:02:48,300 --> 00:02:51,333 (eruption echoes, men exclaim) 59 00:02:51,333 --> 00:02:53,500 SUGAR: And suddenly the explosions came. 60 00:02:53,500 --> 00:02:56,600 (eruptions exploding) 61 00:02:56,600 --> 00:02:59,300 One, two, boom, bang, bing, bong. 62 00:02:59,300 --> 00:03:01,366 Four, five of them. 63 00:03:01,366 --> 00:03:04,166 I realized this one is different. 64 00:03:04,166 --> 00:03:06,200 MAN: Wow! 65 00:03:06,200 --> 00:03:08,066 SUGAR: And suddenly, 66 00:03:08,066 --> 00:03:12,700 I can see white water from one end to the next, 67 00:03:12,700 --> 00:03:15,333 as far as you can see. 68 00:03:15,333 --> 00:03:17,533 ♪ ♪ 69 00:03:17,533 --> 00:03:20,033 A wall of white water. 70 00:03:22,200 --> 00:03:26,466 Nobody think much about it, but then it hit Fafa Island. 71 00:03:26,466 --> 00:03:31,200 The wave was higher than the coconut trees. 72 00:03:31,200 --> 00:03:34,066 You couldn't see the island-- nothing. 73 00:03:35,633 --> 00:03:38,300 I knew what was coming. 74 00:03:39,333 --> 00:03:42,533 Tsunami. 75 00:03:42,533 --> 00:03:44,866 I accepted the fact 76 00:03:44,866 --> 00:03:47,600 that we had three minutes left to live. 77 00:03:47,600 --> 00:03:49,066 I just felt sorry for the boys, 78 00:03:49,066 --> 00:03:51,633 my son and the other boys. 79 00:03:51,633 --> 00:03:54,800 They were busy taking pictures and laughing. 80 00:03:54,800 --> 00:03:56,300 (men laughing) 81 00:03:56,300 --> 00:03:58,033 SUGAR: But I knew, 82 00:03:58,033 --> 00:04:00,900 you get hit by tsunami, you go to deep water. 83 00:04:00,900 --> 00:04:03,233 Just go. 84 00:04:03,233 --> 00:04:06,833 ♪ ♪ 85 00:04:06,833 --> 00:04:10,533 But the wave is chasing us and coming fast. 86 00:04:10,533 --> 00:04:15,400 (in video): Everyone, life jackets! Get your life jackets! 87 00:04:15,400 --> 00:04:19,300 (present day): And the sky was gray and murky. 88 00:04:19,300 --> 00:04:21,800 But now we're in the deep water. 89 00:04:21,800 --> 00:04:25,333 We can see the wave come to the other side 90 00:04:25,333 --> 00:04:26,866 and hit the main island. 91 00:04:26,866 --> 00:04:31,766 It must have gone underneath us-- we didn't even feel it. 92 00:04:31,766 --> 00:04:35,166 We thought we were now okay, just go home and that's it. 93 00:04:35,166 --> 00:04:36,933 But the worst was to come. 94 00:04:36,933 --> 00:04:40,933 (rocks, debris splashing) 95 00:04:40,933 --> 00:04:43,500 It start to rain rocks on us. 96 00:04:45,833 --> 00:04:48,366 (in video): It's getting worse! 97 00:04:49,500 --> 00:04:50,633 (present day): And then... 98 00:04:50,633 --> 00:04:53,066 (in video): No! 99 00:04:53,066 --> 00:04:55,100 (present day): Everything went pitch black. 100 00:04:55,100 --> 00:04:58,833 (debris falling, water splashing) 101 00:04:58,833 --> 00:05:01,666 You couldn't see your hand in front of you. 102 00:05:01,666 --> 00:05:04,066 Everything was dark, no electricity on the island. 103 00:05:04,066 --> 00:05:05,733 No electricity, no lights. 104 00:05:05,733 --> 00:05:07,800 I look at the boys. 105 00:05:07,800 --> 00:05:09,500 Everybody is silent. 106 00:05:11,700 --> 00:05:15,200 Three hours, fighting the sea. 107 00:05:22,433 --> 00:05:24,900 NARRATOR: Branko and his family had survived 108 00:05:24,900 --> 00:05:30,366 the most explosive event ever recorded on Earth. 109 00:05:30,366 --> 00:05:32,633 (eruption explodes) 110 00:05:32,633 --> 00:05:37,266 At 5:15 p.m. on January 15, 2022, 111 00:05:37,266 --> 00:05:40,133 satellites witnessed the volcano 112 00:05:40,133 --> 00:05:41,966 Hunga Tonga-Hunga Ha'apai 113 00:05:41,966 --> 00:05:47,100 blast a cloud of ash and rocks up into the atmosphere. 114 00:05:47,100 --> 00:05:49,300 (eruption echoes, people shouting) 115 00:05:49,300 --> 00:05:51,900 (water rushing) 116 00:05:51,900 --> 00:05:53,833 NARRATOR: Within minutes, tsunami waves crashed 117 00:05:53,833 --> 00:05:56,133 into the South Pacific nation of Tonga. 118 00:05:56,133 --> 00:05:59,133 (baby crying) 119 00:05:59,133 --> 00:06:01,300 (translated): I ran with my son. 120 00:06:01,300 --> 00:06:04,000 I could see that the wave was higher than this house. 121 00:06:04,000 --> 00:06:07,333 (people shouting) 122 00:06:07,333 --> 00:06:09,200 SALOTE KAFOA (translated): We saw a huge wave. 123 00:06:09,200 --> 00:06:11,866 It came splashing over the top of the church 124 00:06:11,866 --> 00:06:13,266 and school roofs. 125 00:06:13,266 --> 00:06:15,800 (people exclaiming) 126 00:06:15,800 --> 00:06:20,033 (translated): A boy came and reached out to grab me. 127 00:06:20,033 --> 00:06:23,333 I said, "What are you doing?" 128 00:06:23,333 --> 00:06:26,866 He said, "I am going to carry you, so we can escape." 129 00:06:26,866 --> 00:06:28,866 (woman speaking non-English language) 130 00:06:28,866 --> 00:06:30,733 (eruption echoes, woman yelps) 131 00:06:30,733 --> 00:06:33,133 NARRATOR: Rock and debris rained down on Tonga 132 00:06:33,133 --> 00:06:35,400 for over ten hours... 133 00:06:35,400 --> 00:06:38,766 (debris falling, clanging) WOMAN: Jesus Christ. 134 00:06:38,766 --> 00:06:42,300 (child exclaiming in background) 135 00:06:43,900 --> 00:06:49,033 NARRATOR: ...covering the country in a layer of volcanic dust. 136 00:06:49,033 --> 00:06:53,700 ♪ ♪ 137 00:06:55,400 --> 00:06:58,833 MARIAN KUPU: It was a disaster. 138 00:06:58,833 --> 00:07:04,566 It was like driving through a movie set 139 00:07:04,566 --> 00:07:09,433 where a bomb just exploded. 140 00:07:09,433 --> 00:07:14,066 It was left with dust and nothing but-- no color. 141 00:07:15,633 --> 00:07:20,266   It was just like a black-and-white movie. 142 00:07:20,266 --> 00:07:23,633 NARRATOR: Journalist Marian Kupu 143 00:07:23,633 --> 00:07:26,400 recorded the impact on her country. 144 00:07:26,400 --> 00:07:30,000 KUPU: This is my route towards work. 145 00:07:30,000 --> 00:07:33,566 And I would drive here and I would take pictures. 146 00:07:33,566 --> 00:07:37,266 ♪ ♪ 147 00:07:37,266 --> 00:07:42,500 There was hopelessness in the faces of people. 148 00:07:42,500 --> 00:07:44,933 (siren blaring in distance) People in shock, 149 00:07:44,933 --> 00:07:47,300 calling and looking for loved ones. 150 00:07:47,300 --> 00:07:50,100 (talking in background) 151 00:07:50,100 --> 00:07:52,566 KUPU: We didn't know-- are we gonna all die? 152 00:07:52,566 --> 00:07:56,466 Is this the end of the world? 153 00:07:56,466 --> 00:08:01,400 ♪ ♪ 154 00:08:01,400 --> 00:08:05,433 NARRATOR: Whole villages were destroyed. 155 00:08:05,433 --> 00:08:06,800 But, remarkably, 156 00:08:06,800 --> 00:08:11,933 across the country, there were just three deaths. 157 00:08:11,933 --> 00:08:14,033 (explosion echoes) 158 00:08:14,033 --> 00:08:16,200 Scientists around the world struggled 159 00:08:16,200 --> 00:08:19,766 to explain the enormity of what had happened. 160 00:08:19,766 --> 00:08:21,866 (rumbling) 161 00:08:21,866 --> 00:08:24,933 CRONIN: From satellites, we saw this huge eruption. 162 00:08:24,933 --> 00:08:26,266 We could not believe it. 163 00:08:26,266 --> 00:08:28,033 (rumbling) 164 00:08:28,033 --> 00:08:31,333 And we still don't know what actually generated that tsunami. 165 00:08:33,466 --> 00:08:35,733 NARRATOR: Discovering how Hunga Tonga-Hunga Ha'apai 166 00:08:35,733 --> 00:08:37,100 caused this disaster 167 00:08:37,100 --> 00:08:39,466 could transform our understanding 168 00:08:39,466 --> 00:08:41,633 of the threats from volcanoes. 169 00:08:41,633 --> 00:08:44,800 (thunder rumbling) 170 00:08:53,366 --> 00:08:56,233 The Kingdom of Tonga. 171 00:08:56,233 --> 00:08:59,966 Home to over 100,000 people. 172 00:08:59,966 --> 00:09:03,900 It is one of the most isolated countries on Earth. 173 00:09:07,100 --> 00:09:09,700 Separated from Australia and New Zealand 174 00:09:09,700 --> 00:09:12,566 by hundreds of miles of open ocean, 175 00:09:12,566 --> 00:09:17,300 it is an archipelago of over 170 separate islands 176 00:09:17,300 --> 00:09:18,600 in the South Pacific. 177 00:09:18,600 --> 00:09:20,933 ♪ ♪ 178 00:09:20,933 --> 00:09:24,200 Less than 40 miles from the main island of Tongatapu 179 00:09:24,200 --> 00:09:28,033   is the volcano Hunga Tonga-Hunga Ha'apai. 180 00:09:29,266 --> 00:09:30,700 (eruption echoes) 181 00:09:30,700 --> 00:09:32,133 WOMAN: Oh, my God! 182 00:09:32,133 --> 00:09:34,633 NARRATOR: When it erupts in January 2022, 183 00:09:34,633 --> 00:09:36,866 the world is in the grip 184 00:09:36,866 --> 00:09:39,133 of the COVID-19 pandemic. 185 00:09:41,666 --> 00:09:44,766 Tonga's borders are closed, 186 00:09:44,766 --> 00:09:48,166 making the nation even more isolated than usual. 187 00:09:51,433 --> 00:09:53,733 Local scientist Taaniela Kula 188 00:09:53,733 --> 00:09:56,100 is one of the first to respond. 189 00:09:56,100 --> 00:09:59,900 KULA: As a geologist, I will never forget this event. 190 00:09:59,900 --> 00:10:01,366 It is the turning point 191 00:10:01,366 --> 00:10:06,233 of how we understand the world. 192 00:10:08,966 --> 00:10:11,933 NARRATOR: An immediate concern is the volcanic ash. 193 00:10:13,300 --> 00:10:18,400 Over six million tons fell on Tongatapu alone... 194 00:10:20,333 --> 00:10:22,800 ...transforming a once-green environment. 195 00:10:26,500 --> 00:10:30,533 (radios running, sirens blaring in distance) 196 00:10:30,533 --> 00:10:33,466 Tongans mobilize to begin the cleanup. 197 00:10:33,466 --> 00:10:36,733 But Taaniela fears the ash poses a danger 198 00:10:36,733 --> 00:10:40,100 to human health. 199 00:10:42,966 --> 00:10:46,233 KULA: Rainwater is our source of drinking water, 200 00:10:46,233 --> 00:10:49,533 and volcanic ash, when it interacts with water, 201 00:10:49,533 --> 00:10:53,833 makes the water more acidic, so it causes health problems. 202 00:10:55,500 --> 00:10:58,466 So we started collecting the ash, 203 00:10:58,466 --> 00:11:02,966 so that we know the true contamination level. 204 00:11:02,966 --> 00:11:05,600 (radio running) 205 00:11:05,600 --> 00:11:10,000 NARRATOR: Samples reveal the ash isn't toxic. 206 00:11:10,000 --> 00:11:14,566 And Tongans can start rebuilding their lives. 207 00:11:16,466 --> 00:11:19,033 For Taaniela, mysteries remain. 208 00:11:20,366 --> 00:11:25,266 Why did the volcano suddenly erupt so violently? 209 00:11:25,266 --> 00:11:29,300 And is it still a danger to his country? 210 00:11:29,300 --> 00:11:34,766 To find out, he needs equipment and resources from overseas. 211 00:11:37,700 --> 00:11:40,633 Nine months after the eruption, he gets his opportunity. 212 00:11:45,566 --> 00:11:47,433 (metal clanging) 213 00:11:49,200 --> 00:11:53,100 The COVID restrictions have been relaxed. 214 00:11:53,100 --> 00:11:57,300 Tonga's borders have reopened. 215 00:11:57,300 --> 00:11:59,666 And an international team of scientists 216 00:11:59,666 --> 00:12:01,700 can join Taaniela on an expedition 217 00:12:01,700 --> 00:12:04,033 to the Hunga volcano. 218 00:12:04,033 --> 00:12:07,933 KULA: People are still anxious to know what's the status at this point. 219 00:12:07,933 --> 00:12:12,933 It's our responsibility to make sure we know our environment 220 00:12:12,933 --> 00:12:16,566 and what's the risk. 221 00:12:16,566 --> 00:12:21,566 NARRATOR: On the ship are marine geologist Marta Ribó 222 00:12:21,566 --> 00:12:24,833 and a volcanologist who has spent decades studying 223 00:12:24,833 --> 00:12:26,500 the volcanoes of the South Pacific... 224 00:12:26,500 --> 00:12:29,100 That one just needs to be parallel with this one. 225 00:12:29,100 --> 00:12:30,100 NARRATOR: ...Shane Cronin. 226 00:12:30,100 --> 00:12:31,466 CRONIN: That's it. 227 00:12:32,933 --> 00:12:35,600 CRONIN: I've been working with Taaniela for the last 20 years or so... 228 00:12:35,600 --> 00:12:37,333 All right! 229 00:12:37,333 --> 00:12:39,566 ...to understand just how these volcanoes work. 230 00:12:40,933 --> 00:12:41,933 Let's rock! 231 00:12:41,933 --> 00:12:44,133 (calls out) 232 00:12:45,566 --> 00:12:47,966 Ooh, I feel we're moving. 233 00:12:47,966 --> 00:12:51,333 Hunga is one of these typical volcanoes that sort of 234 00:12:51,333 --> 00:12:53,966 puffed away for a long time-- so in this case, decades-- 235 00:12:53,966 --> 00:12:55,833 just producing these small eruptions, 236 00:12:55,833 --> 00:12:59,700 and then there was this incredibly big eruption. 237 00:12:59,700 --> 00:13:02,966 This was generated by something at the volcano, 238 00:13:02,966 --> 00:13:05,066 we just don't know what. 239 00:13:06,300 --> 00:13:09,533 NARRATOR: Ahead of them lies a five-hour voyage 240 00:13:09,533 --> 00:13:13,833 to one of the most geologically active places on Earth. 241 00:13:17,100 --> 00:13:19,733 ♪ ♪ 242 00:13:19,733 --> 00:13:21,633 To the east of Tonga, 243 00:13:21,633 --> 00:13:23,866 two of the planet's vast tectonic plates 244 00:13:23,866 --> 00:13:26,766 are crashing into each other. 245 00:13:26,766 --> 00:13:29,833 The Pacific Plate is being forced downwards, 246 00:13:29,833 --> 00:13:32,700 in a process called subduction. 247 00:13:34,266 --> 00:13:37,300 As it descends towards the hot center of the Earth, 248 00:13:37,300 --> 00:13:39,733 it gets warmer. 249 00:13:39,733 --> 00:13:44,566 The rocks begin to melt, turning into liquid magma, 250 00:13:44,566 --> 00:13:47,200 which rises towards the surface, 251 00:13:47,200 --> 00:13:52,000 collecting in magma chambers under the sea floor. 252 00:13:52,000 --> 00:13:55,566 Occasionally, this magma surges upwards... 253 00:13:57,300 --> 00:14:00,366 ...and erupts out of the volcano. 254 00:14:00,366 --> 00:14:04,933 But the constant subduction refills the magma chamber. 255 00:14:04,933 --> 00:14:09,466 Which can trigger more eruptions. 256 00:14:09,466 --> 00:14:11,666 ♪ ♪ 257 00:14:11,666 --> 00:14:14,333 40 miles from Tongatapu, 258 00:14:14,333 --> 00:14:18,600 the ship reaches an area of open ocean. 259 00:14:18,600 --> 00:14:23,066 This is the site of the volcano. 260 00:14:23,066 --> 00:14:26,433 All that is visible are two small islands, 261 00:14:26,433 --> 00:14:28,300 Hunga Tonga 262 00:14:28,300 --> 00:14:31,600 and Hunga Ha'apai. 263 00:14:31,600 --> 00:14:33,800 Looking behind me, you'll see, 264 00:14:33,800 --> 00:14:36,000 seeing the island of Hunga Ha'apai. 265 00:14:36,000 --> 00:14:38,933 So that's right on the edge of the volcano. 266 00:14:38,933 --> 00:14:42,033 The main volcano is actually over to the east. 267 00:14:42,033 --> 00:14:44,533 So in this great big expanse of what looks 268 00:14:44,533 --> 00:14:46,966 just like completely clear ocean, 269 00:14:46,966 --> 00:14:51,100 we're actually sitting right on top of the Hunga caldera. 270 00:14:51,100 --> 00:14:54,600 So below us is actually the volcano. 271 00:14:56,833 --> 00:15:01,300 NARRATOR: Hunga Tonga-Hunga Ha'apai is a submarine volcano. 272 00:15:03,000 --> 00:15:05,100 Its two-and-a-half-mile-wide crater 273 00:15:05,100 --> 00:15:10,533 sits at the top of a mountain nearly 6,000 feet tall, 274 00:15:10,533 --> 00:15:13,766 which is almost completely hidden underwater. 275 00:15:15,800 --> 00:15:18,666 Only in two places is the crater wall high enough 276 00:15:18,666 --> 00:15:20,600 to break the surface, 277 00:15:20,600 --> 00:15:24,966 forming the two islands. 278 00:15:24,966 --> 00:15:28,000 Before the January 15 eruption, 279 00:15:28,000 --> 00:15:30,866 the volcano looked very different. 280 00:15:32,733 --> 00:15:37,733 The center of the crater was 2,300 feet shallower. 281 00:15:39,133 --> 00:15:42,266 The islands were far bigger, 282 00:15:42,266 --> 00:15:45,766 and between them was the volcanic cone. 283 00:15:45,766 --> 00:15:49,066 (eruptions rumbling) 284 00:15:49,066 --> 00:15:54,066 On December 20, 2021, this cone suddenly sprang to life. 285 00:15:56,866 --> 00:16:01,833 Usually, eruptions in Tonga are monitored by satellite, 286 00:16:01,833 --> 00:16:06,333 but space is too far away to pick up all the detail. 287 00:16:07,500 --> 00:16:08,533 (man speaking non-English language) 288 00:16:09,833 --> 00:16:11,666 NARRATOR: So, for almost four weeks, 289 00:16:11,666 --> 00:16:13,933 Taaniela regularly came to the volcano 290 00:16:13,933 --> 00:16:18,833 to check for increasing activity with a drone. 291 00:16:18,833 --> 00:16:21,466 (eruption echoes) 292 00:16:28,600 --> 00:16:31,600 KULA: We came here on 293 00:16:31,600 --> 00:16:34,366 the evening of the 14th of January. 294 00:16:37,000 --> 00:16:41,700 I saw a column of ash and gas... 295 00:16:43,333 --> 00:16:47,233 ...almost two miles wide 296 00:16:47,233 --> 00:16:50,833 just rising into the heavens. 297 00:16:50,833 --> 00:16:54,266 (thunder rumbling) 298 00:16:54,266 --> 00:16:56,733 There were lightning bolts everywhere. 299 00:16:56,733 --> 00:16:59,500 It happened all around the island. 300 00:16:59,500 --> 00:17:03,366 (thunder rumbling) 301 00:17:03,366 --> 00:17:07,100 It's like shooting several thousands of crack, firecrackers 302 00:17:07,100 --> 00:17:08,533 all at the same time. 303 00:17:08,533 --> 00:17:11,066 (eruption exploding) 304 00:17:11,066 --> 00:17:15,200 It felt like I'm witnessing Mother Earth's might 305 00:17:15,200 --> 00:17:18,366 and power being released. 306 00:17:23,666 --> 00:17:27,466 (thunder crashing) 307 00:17:27,466 --> 00:17:32,466 NARRATOR: Eight hours later, the volcano stopped erupting. 308 00:17:34,766 --> 00:17:38,833 Then, at 5:15 p.m. on January 15... 309 00:17:40,600 --> 00:17:44,600 ...it produced an eruption over 70 times larger... 310 00:17:46,933 --> 00:17:53,400 ...exploding with the power of over 60 million tons of TNT 311 00:17:53,400 --> 00:17:57,633 and triggering a series of tsunami waves 312 00:17:57,633 --> 00:18:01,133 that hit Tonga, Australia, 313 00:18:01,133 --> 00:18:05,200 Japan, and the Americas. 314 00:18:05,200 --> 00:18:07,666 Why had this volcano suddenly produced 315 00:18:07,666 --> 00:18:10,366 such an immense explosion? 316 00:18:11,366 --> 00:18:13,200 Why was it so much more powerful 317 00:18:13,200 --> 00:18:15,866 than the previous day's eruption? 318 00:18:17,200 --> 00:18:19,400 And is the volcano active enough 319 00:18:19,400 --> 00:18:22,766 to erupt again in the near future? 320 00:18:26,633 --> 00:18:31,733 First, the team needs to know the volcano's current activity. 321 00:18:31,733 --> 00:18:34,700 CRONIN (chuckling): The weather's not ideal. 322 00:18:34,700 --> 00:18:36,633 I mean, the big problem for us is, 323 00:18:36,633 --> 00:18:38,100 is the sea condition, 324 00:18:38,100 --> 00:18:40,700 and a strong wind is on its way. 325 00:18:40,700 --> 00:18:42,300 So we're really hoping 326 00:18:42,300 --> 00:18:44,100 that we can get all the survey done 327 00:18:44,100 --> 00:18:47,766 before that, that starts coming on. 328 00:18:47,766 --> 00:18:50,900 (radio running) 329 00:18:50,900 --> 00:18:54,633 NARRATOR: Marta is trying to gauge the volcano's activity using sonar. 330 00:18:54,633 --> 00:18:58,066 (pinging faintly) 331 00:18:58,066 --> 00:19:00,466 The echo sounder is sending a ping down, 332 00:19:00,466 --> 00:19:03,433 and the reflection of that ping noise, 333 00:19:03,433 --> 00:19:06,366   it's coming back and it's building up this 3D model 334 00:19:06,366 --> 00:19:09,900 of the sea floor. 335 00:19:09,900 --> 00:19:12,466 NARRATOR: The scanning will reveal if magma is dangerously close 336 00:19:12,466 --> 00:19:14,766 to the surface. 337 00:19:14,766 --> 00:19:16,800 ♪ ♪ 338 00:19:16,800 --> 00:19:20,633 (people talking and laughing in background) 339 00:19:20,633 --> 00:19:23,633 Wow, these are, it's stronger than the one before. 340 00:19:23,633 --> 00:19:26,000 CRONIN: So these are the shallow ones... 341 00:19:26,000 --> 00:19:28,900 NARRATOR: Escaping from the sea floor are plumes of volcanic gases 342 00:19:28,900 --> 00:19:31,200 released by the magma. 343 00:19:31,200 --> 00:19:32,633 1,340 meters. 344 00:19:32,633 --> 00:19:35,033 NARRATOR: The closer the magma is to the surface, 345 00:19:35,033 --> 00:19:37,766 the hotter the plumes 346 00:19:37,766 --> 00:19:41,266 and the more likely an eruption. 347 00:19:41,266 --> 00:19:42,833 (talking in background) 348 00:19:45,933 --> 00:19:48,266 CRONIN: This is a sensor, which actually measures, 349 00:19:48,266 --> 00:19:51,800 2,000 times a second, the temperature of the water. 350 00:19:51,800 --> 00:19:54,966 Is the volcano heating the water, for example? 351 00:19:54,966 --> 00:19:57,333 Is the volcano changing the water temperature? 352 00:19:57,333 --> 00:20:00,800 It's all the question of whether the volcano is alive or not. 353 00:20:00,800 --> 00:20:02,633 That's it, that's it, that's it! 354 00:20:02,633 --> 00:20:05,233 RIBÓ: Careful. 355 00:20:05,233 --> 00:20:06,566 CRONIN: Down, down, down, quick. 356 00:20:07,900 --> 00:20:10,500 Keep going, yup. 357 00:20:10,500 --> 00:20:12,866 NARRATOR: Measuring multiple plumes will reveal how close 358 00:20:12,866 --> 00:20:14,066 the volcano is to erupting. 359 00:20:14,066 --> 00:20:15,233 Running away! 360 00:20:15,233 --> 00:20:17,933   (waves crashing, man exclaims) 361 00:20:17,933 --> 00:20:20,633 KULA: It's a big one! 362 00:20:23,266 --> 00:20:26,933 NARRATOR: They see a consistent trend. 363 00:20:26,933 --> 00:20:30,033 RIBÓ: All of the plumes, they're very weak. 364 00:20:30,033 --> 00:20:33,600 NARRATOR: The plumes aren't hot. 365 00:20:33,600 --> 00:20:34,933 RIBÓ: It's still active, 366 00:20:34,933 --> 00:20:38,566 but the strength of the volcano has decreased. 367 00:20:38,566 --> 00:20:41,466 So for the people of Tonga, there is still some risk, 368 00:20:41,466 --> 00:20:44,466 but it's less dangerous. 369 00:20:44,466 --> 00:20:48,800 NARRATOR: The team's findings suggest the Hunga volcano 370 00:20:48,800 --> 00:20:51,466 won't produce another massive eruption-- 371 00:20:51,466 --> 00:20:53,733 for the time being. 372 00:20:55,466 --> 00:20:57,100 But the events of January 15 373 00:20:57,100 --> 00:21:01,233 show this is an unpredictable volcano. 374 00:21:03,366 --> 00:21:05,566 Why did it suddenly produce an eruption 375 00:21:05,566 --> 00:21:08,733 70 times bigger than the previous day? 376 00:21:12,500 --> 00:21:17,133 It's a question with global implications. 377 00:21:17,133 --> 00:21:21,166 There could be as many as 50,000 submarine volcanoes 378 00:21:21,166 --> 00:21:24,266 lurking under our planet's waves. 379 00:21:24,266 --> 00:21:26,966 In recent years, Kolumbo, 380 00:21:26,966 --> 00:21:29,133 near the Greek island of Santorini, 381 00:21:29,133 --> 00:21:34,000 and Oomurodashi, less than 40 miles from the center of Tokyo, 382 00:21:34,000 --> 00:21:37,333 have been identified as active threats. 383 00:21:40,866 --> 00:21:43,633 Knowing exactly how the Hunga volcano generated 384 00:21:43,633 --> 00:21:45,633 such a powerful eruption 385 00:21:45,633 --> 00:21:47,333 could change our understanding 386 00:21:47,333 --> 00:21:50,100 of the dangers from submarine volcanoes. 387 00:21:50,100 --> 00:21:52,800 (debris falling, people shouting) 388 00:21:52,800 --> 00:21:54,133 And the clues 389 00:21:54,133 --> 00:21:56,600 could lie in the ash Hunga Tonga-Hunga Ha'apai 390 00:21:56,600 --> 00:22:00,400 rained down on the islands. 391 00:22:00,400 --> 00:22:04,333 ♪ ♪ 392 00:22:04,333 --> 00:22:08,966 The debris contains time capsules from the eruption, 393 00:22:08,966 --> 00:22:12,066 which volcanologist Joali Paredes-Mariño analyzes. 394 00:22:14,766 --> 00:22:19,133 The first thing that highlights, to, to me, is this very dark 395 00:22:19,133 --> 00:22:23,033 and, like, glossy, 396 00:22:23,033 --> 00:22:25,900 blocky particles-- so, that's glass. 397 00:22:27,433 --> 00:22:30,333 NARRATOR: Volcanic glass is solidified magma, 398 00:22:30,333 --> 00:22:35,733 created at the very moment the volcano exploded. 399 00:22:40,366 --> 00:22:42,400 A powerful electron microscope 400 00:22:42,400 --> 00:22:46,666 allows Joali to compare different samples of glass. 401 00:22:48,533 --> 00:22:51,000 This one's from a different eruption. 402 00:22:51,000 --> 00:22:53,233 We got this kind of, like, massive glass, 403 00:22:53,233 --> 00:22:56,600 covered with bubbles. MAN: Right. 404 00:22:56,600 --> 00:23:01,600 NARRATOR: Explosions happen when a material expands very rapidly. 405 00:23:01,600 --> 00:23:04,333 In most eruptions, this material 406 00:23:04,333 --> 00:23:08,133 is gas in the magma. 407 00:23:09,200 --> 00:23:13,033 Normally, this gas is dissolved in the liquid magma, 408 00:23:13,033 --> 00:23:16,566 just like in a soda. 409 00:23:16,566 --> 00:23:20,833 If some reason, the pressure that is on that magma change, 410 00:23:20,833 --> 00:23:23,966 like when you open a bottle of soda, 411 00:23:23,966 --> 00:23:26,266 you will have all these bubbles. 412 00:23:26,266 --> 00:23:29,666 They will create this inner force that, at the moment 413 00:23:29,666 --> 00:23:31,166 that it cannot hold it any longer, 414 00:23:31,166 --> 00:23:32,600 it will fragment the magma. 415 00:23:32,600 --> 00:23:35,766 And that's what creates an eruption from within. 416 00:23:37,400 --> 00:23:39,800 NARRATOR: The growing bubbles of gas inside the magma 417 00:23:39,800 --> 00:23:43,966 cause it to expand rapidly and explode, 418 00:23:43,966 --> 00:23:48,400 and are clearly visible in glass from a typical eruption. 419 00:23:50,100 --> 00:23:52,366 But the team sees something very different 420 00:23:52,366 --> 00:23:56,833 in this sample from the Hunga volcano. 421 00:23:56,833 --> 00:23:59,833 If we see the one in the center, you don't see those bubbles. 422 00:23:59,833 --> 00:24:04,233 They have kind of blocky particles. 423 00:24:04,233 --> 00:24:07,533 NARRATOR: No bubbles means the eruption wasn't generated 424 00:24:07,533 --> 00:24:12,266 by the sudden expansion of gas in the magma. 425 00:24:12,266 --> 00:24:14,900 The shapes of the fragments point to the explosion 426 00:24:14,900 --> 00:24:19,566 of a completely different material. 427 00:24:19,566 --> 00:24:22,500 You have this kind of, like, step fractures. 428 00:24:22,500 --> 00:24:24,900 And also, you can see 429 00:24:24,900 --> 00:24:27,366 the big particle in the bottom corner. 430 00:24:27,366 --> 00:24:30,133 This is concave fractures. 431 00:24:30,133 --> 00:24:32,533 NARRATOR: This pattern of fractures is consistent 432 00:24:32,533 --> 00:24:36,200 with a very specific explosive event. 433 00:24:36,200 --> 00:24:39,200 That means that is telling us this is interaction 434 00:24:39,200 --> 00:24:42,066 with magma and water. 435 00:24:42,066 --> 00:24:45,433 NARRATOR: Water can be extremely explosive. 436 00:24:45,433 --> 00:24:49,133 If it hits something as hot as magma, 437 00:24:49,133 --> 00:24:53,266 water instantly turns to gas, 438 00:24:53,266 --> 00:24:56,133 expanding as much as 4,000 times. 439 00:24:56,133 --> 00:24:57,733 (thunder crashing) 440 00:24:57,733 --> 00:24:59,900 It would seem the most intense eruption 441 00:24:59,900 --> 00:25:01,800 ever witnessed by science 442 00:25:01,800 --> 00:25:05,600 was detonated by the explosion of water. 443 00:25:08,500 --> 00:25:11,133 ♪ ♪ 444 00:25:11,133 --> 00:25:14,633 But there is a mystery. 445 00:25:14,633 --> 00:25:19,100 The volcano's magma is usually locked away from the ocean, 446 00:25:19,100 --> 00:25:23,733 in a chamber over three miles below the surface. 447 00:25:23,733 --> 00:25:27,066 Why did water and magma suddenly come into contact 448 00:25:27,066 --> 00:25:30,233 on January 15? 449 00:25:30,233 --> 00:25:32,833 In the global seismic records, 450 00:25:32,833 --> 00:25:37,633 the team spots signals the satellites didn't detect. 451 00:25:37,633 --> 00:25:39,233 Okay. That's it? 452 00:25:39,233 --> 00:25:41,766 Uh-huh! Yes. 453 00:25:41,766 --> 00:25:44,233 NARRATOR: 28 minutes before the big eruption, 454 00:25:44,233 --> 00:25:49,700 there was a series of smaller, precursory eruptions. 455 00:25:49,700 --> 00:25:52,433 CRONIN: We think the precursory eruptions 456 00:25:52,433 --> 00:25:56,033 led to the rapid fracturing of the upper volcano. 457 00:25:56,033 --> 00:25:59,633   And then seawater gets down into the magma, and away we go, 458 00:25:59,633 --> 00:26:04,033 and we start a very, very violent explosion. 459 00:26:05,833 --> 00:26:07,400 NARRATOR: The magma and water 460 00:26:07,400 --> 00:26:12,233 were separated by thousands of feet of solid rock. 461 00:26:12,233 --> 00:26:15,533 The team thinks, on January 15, 462 00:26:15,533 --> 00:26:20,166 the first of the precursory eruptions cracked open faults. 463 00:26:23,833 --> 00:26:26,500 As this series of eruptions continued, 464 00:26:26,500 --> 00:26:29,566 these cracks grew bigger. 465 00:26:29,566 --> 00:26:32,433 And bigger. 466 00:26:32,433 --> 00:26:36,933 Until finally, they allowed cold seawater to flood in, 467 00:26:36,933 --> 00:26:40,500 hitting incredibly hot magma in the chamber 468 00:26:40,500 --> 00:26:43,400 and generating the immense explosion. 469 00:26:43,400 --> 00:26:46,200 (booming) 470 00:26:48,866 --> 00:26:52,900 The investigators have made a major breakthrough: 471 00:26:52,900 --> 00:26:55,433 an explanation for how the Hunga volcano 472 00:26:55,433 --> 00:27:00,033 could have produced such a powerful explosion. 473 00:27:00,033 --> 00:27:04,000 But they face another problem. 474 00:27:04,000 --> 00:27:06,333 (eruption explodes, thunder crashes) 475 00:27:06,333 --> 00:27:09,766 Most tsunamis are caused by earthquakes. 476 00:27:09,766 --> 00:27:13,000 Volcanic tsunamis are so rare, 477 00:27:13,000 --> 00:27:15,500 scientists don't know how the Hunga volcano 478 00:27:15,500 --> 00:27:20,500 generated a series of enormous waves. 479 00:27:20,500 --> 00:27:24,433 Discovering what happened here could give new insights 480 00:27:24,433 --> 00:27:29,966 into the global threat from submarine volcanoes. 481 00:27:29,966 --> 00:27:35,566 The answers could lie on Tonga's Hihifo peninsula. 482 00:27:38,633 --> 00:27:42,766 Once, this area was dotted with thriving resorts. 483 00:27:44,833 --> 00:27:49,500 One of the busiest was owned by Moana Paea. 484 00:27:49,500 --> 00:27:51,666 PAEA: The whole place 485 00:27:51,666 --> 00:27:55,433 was just full of beautiful big trees 486 00:27:55,433 --> 00:27:57,833 and coconut trees and palm trees. 487 00:27:57,833 --> 00:28:00,900   You wouldn't have seen the ocean. 488 00:28:00,900 --> 00:28:04,200 That used to be the tree with all surfboards on it. 489 00:28:04,200 --> 00:28:08,400 It was a massive tree. 490 00:28:08,400 --> 00:28:10,733 As a kid, we would climb around it. 491 00:28:10,733 --> 00:28:13,533 But after that tree, there was a house there, 492 00:28:13,533 --> 00:28:18,733 and then from there would be the beach area. 493 00:28:20,166 --> 00:28:22,533 NARRATOR: The Hihifo peninsula lies 494 00:28:22,533 --> 00:28:27,066 on the northwest coast of Tongatapu. 495 00:28:27,066 --> 00:28:29,466 Less than 40 miles due north 496 00:28:29,466 --> 00:28:33,333 is the volcano Hunga Tonga-Hunga Ha'apai. 497 00:28:33,333 --> 00:28:36,566 (volcano rumbling, thunder crashing) 498 00:28:36,566 --> 00:28:41,300 PAEA: The volcano was going crazy, striking lightning and stuff. 499 00:28:41,300 --> 00:28:43,866 Because it'd been happening for weeks and weeks, 500 00:28:43,866 --> 00:28:46,666 we kind of took it for granted that it must be all right. 501 00:28:46,666 --> 00:28:48,900 ♪ ♪ 502 00:28:48,900 --> 00:28:50,500 We had a full hotel, 503 00:28:50,500 --> 00:28:53,900 and maybe quarter past five, I heard screaming. 504 00:28:53,900 --> 00:28:55,400 MAN: Here! 505 00:28:55,400 --> 00:28:56,800 PAEA: One of my staff said, 506 00:28:56,800 --> 00:28:58,866 "Hey, look at the water." 507 00:28:58,866 --> 00:29:00,866 It looked like a washing machine. 508 00:29:00,866 --> 00:29:02,433 (man exclaims) 509 00:29:02,433 --> 00:29:05,366 And I just screamed, "It's a tsunami!" 510 00:29:05,366 --> 00:29:07,466 (people yelling in background) 511 00:29:07,466 --> 00:29:09,400 PAEA: And people were going to pack their clothes, 512 00:29:09,400 --> 00:29:11,366 and I said, "No, you need to get out!" 513 00:29:11,366 --> 00:29:13,766 One family literally just got out of the pool 514 00:29:13,766 --> 00:29:15,233 and got in their car and took off. 515 00:29:15,233 --> 00:29:17,266 (men speaking indistinctly) 516 00:29:17,266 --> 00:29:18,533 PAEA: That's when I saw... 517 00:29:18,533 --> 00:29:20,166 MAN: Oh, my God. 518 00:29:20,166 --> 00:29:24,000 PAEA: ...the water is moving fast, but growing. 519 00:29:24,000 --> 00:29:25,566 So we ran through here. 520 00:29:25,566 --> 00:29:29,366 (people exclaiming) WOMAN: Oh! Oh, (bleep)! 521 00:29:29,366 --> 00:29:31,266 PAEA: We were yelling, "Tsunami! Tsunami!" 522 00:29:31,266 --> 00:29:32,600 MAN: Holy (bleep)! 523 00:29:32,600 --> 00:29:34,533 (people exclaiming) 524 00:29:34,533 --> 00:29:35,600 PAEA: And my son was, like, 525 00:29:35,600 --> 00:29:37,433 "Mom, let's climb a tree." 526 00:29:37,433 --> 00:29:38,900 And then, suddenly... 527 00:29:38,900 --> 00:29:40,066 (explosion pounds) 528 00:29:40,066 --> 00:29:41,200 MAN: Oh, (bleep)! 529 00:29:41,200 --> 00:29:42,200 WOMAN: Whoa! 530 00:29:42,200 --> 00:29:43,700 MAN: Holy (bleep)! 531 00:29:43,700 --> 00:29:46,133 PAEA: Another massive explosion. 532 00:29:46,133 --> 00:29:47,166 MAN: Tsunami's heading in. 533 00:29:47,166 --> 00:29:48,933 (people exclaiming) (bleep) 534 00:29:48,933 --> 00:29:51,200 The pressure of it threw all of us on the ground. 535 00:29:51,200 --> 00:29:53,566 My daughter was crying, "My ears!" 536 00:29:53,566 --> 00:29:56,133 But my sons are, like, "Mom, get up, get up!" 537 00:29:56,133 --> 00:30:00,033 Because we could still hear waves rumbling. 538 00:30:00,033 --> 00:30:02,766 (men shouting indistinctly) 539 00:30:02,766 --> 00:30:03,966 MAN: Okay, okay! 540 00:30:03,966 --> 00:30:06,266 (baby crying) 541 00:30:06,266 --> 00:30:07,833 (man panting) 542 00:30:07,833 --> 00:30:09,566 MAN: Here! 543 00:30:09,566 --> 00:30:12,066 (waves crashing, water rushing) 544 00:30:12,066 --> 00:30:13,833 PAEA: And when we got down to the road, 545 00:30:13,833 --> 00:30:16,300 there's this two-story house there, 546 00:30:16,300 --> 00:30:18,633 and there were all these village people 547 00:30:18,633 --> 00:30:20,600 up on top of there, and it started to 548 00:30:20,600 --> 00:30:22,333 rain down with dust. 549 00:30:22,333 --> 00:30:25,100 (baby crying, people murmuring and exclaiming) 550 00:30:25,100 --> 00:30:26,733 (water rushing) 551 00:30:26,733 --> 00:30:29,300 PAEA: When we got to the roof, 552 00:30:29,300 --> 00:30:34,166 we saw the big swell coming across. 553 00:30:34,166 --> 00:30:37,300 (people whimpering and shouting) 554 00:30:37,300 --> 00:30:38,566 PAEA: We were praying and singing. 555 00:30:38,566 --> 00:30:42,266 And then my brother came, so we all came down. 556 00:30:42,266 --> 00:30:43,566 (water rushing) 557 00:30:43,566 --> 00:30:45,966 We got in the car, and it being so dark, 558 00:30:45,966 --> 00:30:49,400 and the dust was massive, and rocks coming... 559 00:30:49,400 --> 00:30:50,966 (debris pelting) CHILD: Mommy... 560 00:30:50,966 --> 00:30:54,833 PAEA: And they weren't just little rocks. (debris pelting) 561 00:30:54,833 --> 00:30:57,866 (people whimpering, murmuring) 562 00:30:57,866 --> 00:31:01,266 ♪ ♪ 563 00:31:01,266 --> 00:31:04,133 (people speaking in background) 564 00:31:04,133 --> 00:31:05,500 NARRATOR: Like many Tongans, 565 00:31:05,500 --> 00:31:07,933 Moana headed for the safety of high ground. 566 00:31:10,133 --> 00:31:13,333 ♪ ♪ 567 00:31:13,333 --> 00:31:17,333 The next day revealed the scale of the destruction. 568 00:31:17,333 --> 00:31:22,366 ♪ ♪ 569 00:31:26,366 --> 00:31:30,366 PAEA: I remember one of my staff ringing up the next morning. 570 00:31:31,966 --> 00:31:34,700 (voice breaking): And he's saying, "Sorry, Moana, 571 00:31:34,700 --> 00:31:37,266 everything is gone." 572 00:31:37,266 --> 00:31:39,233 And I said to him, "Praise God, 573 00:31:39,233 --> 00:31:41,233 "we are all still alive. 574 00:31:41,233 --> 00:31:43,333 That's the main thing." (sniffs) 575 00:31:43,333 --> 00:31:46,833 (breath trembles) 576 00:31:46,833 --> 00:31:52,133 ♪ ♪ 577 00:31:52,133 --> 00:31:54,100 We loved it here. 578 00:31:54,100 --> 00:31:56,066 Such a beautiful space. 579 00:31:56,066 --> 00:31:58,100 (gasps) 580 00:31:58,100 --> 00:32:00,933 It was very hard to see, 581 00:32:00,933 --> 00:32:03,833 because this is our livelihood, 582 00:32:03,833 --> 00:32:06,633 and this is something that has looked after... 583 00:32:06,633 --> 00:32:08,633 (sniffles): ...our community for many years. 584 00:32:08,633 --> 00:32:12,566 (sniffles, breathes deeply) 585 00:32:12,566 --> 00:32:14,333 ♪ ♪ 586 00:32:14,333 --> 00:32:19,700 NARRATOR: Ahead of Moana lies months of rebuilding. 587 00:32:19,700 --> 00:32:26,833 This is the stark reality of the tsunami that hit Tonga. 588 00:32:26,833 --> 00:32:29,933 But this event is also a mystery. 589 00:32:29,933 --> 00:32:35,266 How did the volcano generate such destructive waves? 590 00:32:39,600 --> 00:32:43,533 Tsunami scientist Jose Borrero has flown in to investigate. 591 00:32:43,533 --> 00:32:45,533 (wind blowing) 592 00:32:45,533 --> 00:32:47,066 (shutter clicking) 593 00:32:47,066 --> 00:32:50,133 BORRERO: As tsunami waves propagate through the ocean, 594 00:32:50,133 --> 00:32:53,400 their speed is governed by the depth of the water. 595 00:32:53,400 --> 00:32:55,966 So, the deeper the water, the faster they can go. 596 00:32:55,966 --> 00:32:59,166 Now, where we are, on the west coast of Tongatapu, 597 00:32:59,166 --> 00:33:01,100 there was a very narrow fringing reef, 598 00:33:01,100 --> 00:33:02,300 and you can see the reef here. 599 00:33:02,300 --> 00:33:05,166 It was where the waves are breaking. 600 00:33:05,166 --> 00:33:07,966   Just on the other side of that reef, 601 00:33:07,966 --> 00:33:11,233 the water drops off to about a depth of 602 00:33:11,233 --> 00:33:14,433 just over 1,000 meters. 603 00:33:14,433 --> 00:33:18,600 It's deep water from here out to the Hunga volcano. 604 00:33:18,600 --> 00:33:22,133 ♪ ♪ 605 00:33:22,133 --> 00:33:24,800 The tsunami came directly in here, unimpeded. 606 00:33:24,800 --> 00:33:27,200 There was no reefs or features 607 00:33:27,200 --> 00:33:30,033 or anything in the way to slow it down, redirect it. 608 00:33:30,033 --> 00:33:31,933 ♪ ♪ 609 00:33:31,933 --> 00:33:34,966 And the tsunami takes only eight minutes 610 00:33:34,966 --> 00:33:37,733 to get from the volcano to here. 611 00:33:37,733 --> 00:33:40,066 ♪ ♪ 612 00:33:40,066 --> 00:33:43,933 NARRATOR: A wave with immense power arrived at the peninsula 613 00:33:43,933 --> 00:33:47,000 and caused widespread damage 614 00:33:47,000 --> 00:33:50,666 because of what happens when a tsunami enters shallow water. 615 00:33:50,666 --> 00:33:53,400 ♪ ♪ 616 00:33:55,066 --> 00:33:57,900 The energy of a tsunami is spread throughout 617 00:33:57,900 --> 00:34:00,333 the depth of the ocean. 618 00:34:00,333 --> 00:34:01,866 In deep water, 619 00:34:01,866 --> 00:34:06,566 this makes the height of the wave barely noticeable. 620 00:34:06,566 --> 00:34:08,966 But as the wave reaches shallow water, 621 00:34:08,966 --> 00:34:12,533 it is slowed dramatically, 622 00:34:12,533 --> 00:34:16,266 and the water begins to pile up, 623 00:34:16,266 --> 00:34:21,166 making the wave higher and higher. 624 00:34:21,166 --> 00:34:25,166 BORRERO: When a tsunami comes ashore, 625 00:34:25,166 --> 00:34:27,600 it's not just the water that causes the damage. 626 00:34:27,600 --> 00:34:30,100 It starts to pick things up. 627 00:34:30,100 --> 00:34:32,433 It starts with boulders and sand. 628 00:34:32,433 --> 00:34:35,433 And then it knocks down trees, 629 00:34:35,433 --> 00:34:37,533 and the trees become entrained in the flow. 630 00:34:37,533 --> 00:34:39,466 Then it'll take out a house, 631 00:34:39,466 --> 00:34:43,033 and the material from the house will become part of the flow. 632 00:34:43,033 --> 00:34:45,966 And all of this material gradually builds up 633 00:34:45,966 --> 00:34:47,633 until it's, it's not even water anymore. 634 00:34:47,633 --> 00:34:51,833 It's a dense debris flow 635 00:34:51,833 --> 00:34:55,400 of everything that the wave has picked up along the way. 636 00:34:55,400 --> 00:35:01,366 ♪ ♪ 637 00:35:02,933 --> 00:35:06,000 NARRATOR: Jose's first task is working out the height and power 638 00:35:06,000 --> 00:35:09,033 of the incoming wave. 639 00:35:09,033 --> 00:35:12,766 And the trail of destruction offers him the vital clues. 640 00:35:12,766 --> 00:35:13,966 This is weird. 641 00:35:15,700 --> 00:35:17,200   This stuff is 642 00:35:17,200 --> 00:35:19,766 very difficult to bend with your hand, 643 00:35:19,766 --> 00:35:21,033 but the way we see it here, 644 00:35:21,033 --> 00:35:22,966 just wrapped around a concrete pillar 645 00:35:22,966 --> 00:35:27,533 like tissue paper, but with roofing steel. 646 00:35:27,533 --> 00:35:32,433 NARRATOR: First, Jose needs to find the wave's direction. 647 00:35:32,433 --> 00:35:34,766 Over here, 648 00:35:34,766 --> 00:35:38,233 we see these concrete columns 649 00:35:38,233 --> 00:35:42,900 are knocked down in the direction the wave was going. 650 00:35:42,900 --> 00:35:44,866 So the wave came from behind us, 651 00:35:44,866 --> 00:35:47,500 from the north, swept down the beach, 652 00:35:47,500 --> 00:35:50,700 and took out these columns, laying them down that way. 653 00:35:52,300 --> 00:35:54,966 NARRATOR: Following the trail of debris inland, 654 00:35:54,966 --> 00:35:58,933 Jose can find the evidence he needs. 655 00:35:58,933 --> 00:36:00,666 ♪ ♪ 656 00:36:00,666 --> 00:36:03,933 BORRERO: Up here is one of the most crucial bits of information 657 00:36:03,933 --> 00:36:06,200 from the whole tsunami event. 658 00:36:06,200 --> 00:36:09,233 This was a cell phone tower. 659 00:36:09,233 --> 00:36:11,766 And on the cell phone tower was a weather station, 660 00:36:11,766 --> 00:36:14,500 and, as you can see, was completely obliterated 661 00:36:14,500 --> 00:36:17,700 by the tsunami surge. 662 00:36:17,700 --> 00:36:20,433 This is a very strong piece of equipment. 663 00:36:20,433 --> 00:36:23,133 It's a big, strong thing. 664 00:36:23,133 --> 00:36:25,233 This was a 20-meter-tall tower. 665 00:36:25,233 --> 00:36:29,900 But yet the force was able to bend the entire thing over. 666 00:36:32,066 --> 00:36:34,866 And 200 meters inland, on one of the trees 667 00:36:34,866 --> 00:36:38,400 is pieces of this tower still hanging from a branch 668 00:36:38,400 --> 00:36:42,200 five to six meters above the ground. 669 00:36:42,200 --> 00:36:45,566 NARRATOR: Bringing all of this information together, 670 00:36:45,566 --> 00:36:48,166 Jose can compute the scale of the tsunami. 671 00:36:48,166 --> 00:36:50,466 ♪ ♪ 672 00:36:50,466 --> 00:36:52,966 BORRERO: So the ground level that we're standing at 673 00:36:52,966 --> 00:36:55,000 is about 13 meters above sea level. 674 00:36:55,000 --> 00:36:57,400 And then with the flow marks around this area, 675 00:36:57,400 --> 00:37:00,466 we know that the tsunami flow depth through here was 676 00:37:00,466 --> 00:37:02,233 somewhere to five to six meters. 677 00:37:02,233 --> 00:37:05,633 So we're talking, you know, 18, 19 meters 678 00:37:05,633 --> 00:37:08,900 of, of total tsunami height passing through this area. 679 00:37:11,700 --> 00:37:16,833 NARRATOR: 19 meters is over 60 feet-- 680 00:37:16,833 --> 00:37:20,900 about the height of a six-story building. 681 00:37:22,700 --> 00:37:25,133 (water rushing) 682 00:37:25,133 --> 00:37:29,500 NARRATOR: In 2011, a massive earthquake unleashed a tsunami on Japan. 683 00:37:29,500 --> 00:37:31,833 (people screaming) 684 00:37:31,833 --> 00:37:33,666 NARRATOR: Despite being protected by a breakwater 685 00:37:33,666 --> 00:37:37,000 costing some $1.6 billion, 686 00:37:37,000 --> 00:37:39,400 Kamaishi City was hit by a wave 687 00:37:39,400 --> 00:37:42,900 that measured 26 feet tall. 688 00:37:42,900 --> 00:37:45,466 (water rushing) 689 00:37:45,466 --> 00:37:49,400 All of this damage was caused by a wave 690 00:37:49,400 --> 00:37:54,066 less than half the height of the Hihifo tsunami. 691 00:37:54,066 --> 00:37:57,733 ♪ ♪ 692 00:37:57,733 --> 00:38:01,966 How did the Hunga volcano generate such an immense wave? 693 00:38:01,966 --> 00:38:05,400 (men exclaiming) 694 00:38:05,400 --> 00:38:06,600 BORRERO: So, yeah, this is you guys 695 00:38:06,600 --> 00:38:08,300 parked up here. Yes. 696 00:38:08,300 --> 00:38:09,666 NARRATOR: To find out, 697 00:38:09,666 --> 00:38:14,166 Jose gathers eyewitness testimony and video. 698 00:38:14,166 --> 00:38:16,633 MAN 2: I was the driver of that car. 699 00:38:16,633 --> 00:38:19,133 BORRERO: Were you waiting for someone to come? No. 700 00:38:19,133 --> 00:38:20,533 We were waiting because the... 701 00:38:20,533 --> 00:38:22,733 The road! Over the road. The road was busy. 702 00:38:22,733 --> 00:38:27,100 (laughs): And the waves began banging on the car. 703 00:38:27,100 --> 00:38:30,933 (all exclaiming in video) 704 00:38:30,933 --> 00:38:32,533 (video rewinding) 705 00:38:32,533 --> 00:38:35,133 NARRATOR: Jose is combining this firsthand evidence 706 00:38:35,133 --> 00:38:39,033 with images and videos he has found on social media. 707 00:38:41,133 --> 00:38:42,400 BORRERO: It's astounding, 708 00:38:42,400 --> 00:38:44,266 the amount of material that's available online. 709 00:38:44,266 --> 00:38:45,766 People just post things up, 710 00:38:45,766 --> 00:38:48,333 and all of this is completely useful 711 00:38:48,333 --> 00:38:49,333 in a scientific sense. 712 00:38:49,333 --> 00:38:51,566 We have a set of videos 713 00:38:51,566 --> 00:38:53,333 that show a series of tsunami waves, 714 00:38:53,333 --> 00:38:56,566 and we know what time the video was taken. 715 00:38:56,566 --> 00:38:59,000 And by knowing the timing of when it's hitting the coast, 716 00:38:59,000 --> 00:39:00,366 it gives us clues as to 717 00:39:00,366 --> 00:39:04,300 how that wave was generated at the volcano. 718 00:39:04,300 --> 00:39:06,800 NARRATOR: Jose has built a timeline of the day. 719 00:39:06,800 --> 00:39:08,266 (eruption explodes in distance) MAN 1: Oh! MAN 2: Whoo! 720 00:39:08,266 --> 00:39:10,033 MAN 1: Holy (bleep)! 721 00:39:10,033 --> 00:39:14,133 NARRATOR: He's identified not one, but two tsunamis-- 722 00:39:14,133 --> 00:39:17,966 one at 5:23 and one at 5:34. 723 00:39:17,966 --> 00:39:19,100 (mouse clicking) 724 00:39:19,100 --> 00:39:21,300 Tracking back eight minutes from each, 725 00:39:21,300 --> 00:39:23,300 he finds the same thing. 726 00:39:24,966 --> 00:39:27,266 An eruption at the volcano. 727 00:39:27,266 --> 00:39:30,266 ♪ ♪ 728 00:39:30,266 --> 00:39:32,500 This fits with one theory 729 00:39:32,500 --> 00:39:37,066 of how submarine volcanoes produce tsunamis. 730 00:39:37,066 --> 00:39:41,633 As material erupts upwards, it pushes water out of the way, 731 00:39:41,633 --> 00:39:45,566 creating immense waves that radiate out from the volcano. 732 00:39:49,766 --> 00:39:52,966 But Jose doesn't think these eruptions 733 00:39:52,966 --> 00:39:56,466 can explain the destructive 60-foot-high tsunami. 734 00:39:56,466 --> 00:39:58,400 ♪ ♪ 735 00:39:58,400 --> 00:39:59,933 BORRERO: We know the weather station 736 00:39:59,933 --> 00:40:02,866 transmitted its last packet of data at 6:00 p.m. 737 00:40:02,866 --> 00:40:05,066 So we know a tsunami 738 00:40:05,066 --> 00:40:06,800 could not have destroyed the weather station 739 00:40:06,800 --> 00:40:08,900 and the cell phone tower that it was attached to 740 00:40:08,900 --> 00:40:12,100 until sometime after 6:00 p.m. 741 00:40:12,100 --> 00:40:16,800 This means that there was a later wave. 742 00:40:16,800 --> 00:40:18,666 But this doesn't fit 743 00:40:18,666 --> 00:40:20,733 with the idea that the wave was generated 744 00:40:20,733 --> 00:40:22,766 during these two volcanic eruptions. 745 00:40:22,766 --> 00:40:27,233 ♪ ♪ 746 00:40:27,233 --> 00:40:28,800 NARRATOR: If it wasn't an eruption, 747 00:40:28,800 --> 00:40:31,566 what other event at the Hunga volcano 748 00:40:31,566 --> 00:40:33,566 would have enough power to unleash 749 00:40:33,566 --> 00:40:35,833 a 60-foot-high tsunami? 750 00:40:35,833 --> 00:40:38,733 (eruption thundering) 751 00:40:38,733 --> 00:40:41,233 (roaring) 752 00:40:41,233 --> 00:40:45,666 One possibility lies with the speed it threw out material. 753 00:40:47,400 --> 00:40:49,866 CRONIN: During the first one-and-a-half hours, 754 00:40:49,866 --> 00:40:54,600 it was ejecting material at a rate twice as much as 755 00:40:54,600 --> 00:40:56,733 the next-biggest eruption that we know of. 756 00:40:56,733 --> 00:41:01,333 It threw out seven cubic kilometers of 757 00:41:01,333 --> 00:41:03,400 dense rock material. 758 00:41:03,400 --> 00:41:07,700 NARRATOR: That's enough to cover the entire island of Manhattan 759 00:41:07,700 --> 00:41:11,633 in nearly 400 feet of debris. 760 00:41:11,633 --> 00:41:15,200 CRONIN: When a large amount of magma erupts from a volcano, 761 00:41:15,200 --> 00:41:17,666 large amounts of magma come out at once. 762 00:41:17,666 --> 00:41:20,133 And so that means that the top part of the volcano 763 00:41:20,133 --> 00:41:23,300 actually then sinks in on itself. 764 00:41:23,300 --> 00:41:26,433 NARRATOR: Shane's idea is that 765 00:41:26,433 --> 00:41:29,300 as material erupted out of the magma chamber, 766 00:41:29,300 --> 00:41:34,433 it created a larger and larger void underground. 767 00:41:34,433 --> 00:41:38,500 When it could no longer support the weight of material above, 768 00:41:38,500 --> 00:41:43,633 the entire caldera dropped over 2,300 feet. 769 00:41:43,633 --> 00:41:46,666 Seawater flooded in, 770 00:41:46,666 --> 00:41:48,766 kickstarting tsunamis that radiated 771 00:41:48,766 --> 00:41:53,000 out from the volcano, 772 00:41:53,000 --> 00:41:55,400 an explanation of how the volcano 773 00:41:55,400 --> 00:41:59,566 could generate a 60-foot wave. 774 00:41:59,566 --> 00:42:04,533 ♪ ♪ 775 00:42:04,533 --> 00:42:06,800 The team has found that a caldera 776 00:42:06,800 --> 00:42:09,333 where the water can get into the magma chamber 777 00:42:09,333 --> 00:42:12,333 can erupt explosively 778 00:42:12,333 --> 00:42:14,866 and generate life-threatening tsunamis, 779 00:42:14,866 --> 00:42:19,166 heightening the need to monitor these types of volcanoes. 780 00:42:22,300 --> 00:42:26,566 And only 55 miles from Hunga Tonga-Hunga Ha'apai 781 00:42:26,566 --> 00:42:29,433 is its volcanic twin: 782 00:42:29,433 --> 00:42:32,566 the island of Tofua. 783 00:42:32,566 --> 00:42:34,733 Just like the Hunga volcano, 784 00:42:34,733 --> 00:42:39,500 Tofua has a two-and-a-half- mile-wide caldera. 785 00:42:41,866 --> 00:42:47,166 But its magma chamber is far closer to the surface, 786 00:42:47,166 --> 00:42:52,600 and far closer to the surrounding seawater. 787 00:42:52,600 --> 00:42:55,900 ♪ ♪ 788 00:42:55,900 --> 00:42:57,166 KULA: Captain, 789 00:42:57,166 --> 00:43:00,433 we're keeping a straight line. 790 00:43:00,433 --> 00:43:01,966 We're about here. 791 00:43:01,966 --> 00:43:04,533 CRONIN: It's a very remote part of the world, 792 00:43:04,533 --> 00:43:06,033 and so no one's been able to get here. 793 00:43:06,033 --> 00:43:09,566 It's 14 hours on the boat, 794 00:43:09,566 --> 00:43:11,700 and out here, the ocean can be 795 00:43:11,700 --> 00:43:14,066 extremely treacherous. 796 00:43:14,066 --> 00:43:17,133 ♪ ♪ 797 00:43:17,133 --> 00:43:19,200 All previous measurements 798 00:43:19,200 --> 00:43:22,366 have been made from satellite observations, 799 00:43:22,366 --> 00:43:26,466 so it's critical that we try to land on the island. 800 00:43:26,466 --> 00:43:28,333 NARRATOR: The satellites suggest 801 00:43:28,333 --> 00:43:31,166 there is virtually no activity at Tofua. 802 00:43:31,166 --> 00:43:36,300 But this has never been verified with field measurements. 803 00:43:40,366 --> 00:43:44,633 NARRATOR: Taaniela and Shane enlist the help of boatmen 804 00:43:44,633 --> 00:43:46,833 from the neighboring island of Kotu. 805 00:43:46,833 --> 00:43:49,133 (motor humming) 806 00:43:49,133 --> 00:43:51,700 They report having seen 807 00:43:51,700 --> 00:43:54,800 a red glow above Tofua at night. 808 00:43:57,566 --> 00:44:02,066 ♪ ♪ 809 00:44:05,500 --> 00:44:09,800 KULA: I feel excited to go up for the first time. 810 00:44:09,800 --> 00:44:13,500 We hope to get some real data on the ground. 811 00:44:13,500 --> 00:44:16,800 And then, uh, we can share it with the world. 812 00:44:16,800 --> 00:44:19,433 ♪ ♪ 813 00:44:19,433 --> 00:44:21,666 NARRATOR: First, they need to ascend 814 00:44:21,666 --> 00:44:27,566 over 1,500 feet through tropical forests. 815 00:44:27,566 --> 00:44:31,766 ♪ ♪ 816 00:44:31,766 --> 00:44:33,933 CRONIN: It's quite humid. 817 00:44:33,933 --> 00:44:35,466 So... 818 00:44:35,466 --> 00:44:38,366 I think my sweat is on top of my sweat, 819 00:44:38,366 --> 00:44:41,466 building up a third layer of sweat. 820 00:44:41,466 --> 00:44:43,900 (grunts) 821 00:44:43,900 --> 00:44:47,700 ♪ ♪ 822 00:44:50,000 --> 00:44:52,966 NARRATOR: Their first objective: 823 00:44:52,966 --> 00:44:56,500 the rim of Tofua's two-and-a-half-mile-wide crater. 824 00:44:58,200 --> 00:45:03,633 CRONIN: Look, look, this is a big caldera. 825 00:45:03,633 --> 00:45:06,700 Yeah, so there's the active cone. 826 00:45:06,700 --> 00:45:09,466 That's our destination, should we decide to accept it. 827 00:45:12,033 --> 00:45:14,666 NARRATOR: Shane suspects the satellites are wrong 828 00:45:14,666 --> 00:45:17,733 and Tofua could be due an eruption. 829 00:45:20,233 --> 00:45:23,666 CRONIN: We had a big eruption around 1,200 years ago, 830 00:45:23,666 --> 00:45:27,366 another big one around 800 years ago, 831 00:45:27,366 --> 00:45:32,400 and the most recent one around 400 years ago. 832 00:45:32,400 --> 00:45:36,333 NARRATOR: This pattern suggests Tofua should erupt again, 833 00:45:36,333 --> 00:45:38,200 and soon. 834 00:45:40,766 --> 00:45:41,933 (camera shutter clicks) 835 00:45:41,933 --> 00:45:43,233 CRONIN: Okay, it's fantastic. 836 00:45:43,233 --> 00:45:44,700 We've got a bit of a break in the weather. 837 00:45:44,700 --> 00:45:47,866 You can see how blue that gas is coming off that volcano. 838 00:45:50,700 --> 00:45:54,866 When the color of the gas is blue, it's sulfur dioxide. 839 00:45:54,866 --> 00:45:58,600 NARRATOR: This gas is released by the magma. 840 00:46:01,066 --> 00:46:03,066 The blue color is only visible 841 00:46:03,066 --> 00:46:08,166 if the levels of sulfur dioxide are high. 842 00:46:08,166 --> 00:46:09,400 CRONIN: So I think the magma 843 00:46:09,400 --> 00:46:10,933 must be very close to the... (shutter clicks) 844 00:46:10,933 --> 00:46:13,766 ...close to the surface, actually. 845 00:46:13,766 --> 00:46:16,200 (shutter clicks) 846 00:46:16,200 --> 00:46:18,200 And this corresponds to 847 00:46:18,200 --> 00:46:19,833 what the locals have been reporting 848 00:46:19,833 --> 00:46:22,300 over the last couple of months, 849 00:46:22,300 --> 00:46:25,866 is that there is a glow in the sky above Tofua 850 00:46:25,866 --> 00:46:29,233 when there's a cloudy evening. 851 00:46:32,100 --> 00:46:35,300 NARRATOR: The signs point to Tofua being far more active 852 00:46:35,300 --> 00:46:39,366 than the satellite readings suggest. 853 00:46:40,766 --> 00:46:43,133 But to know the level of the threat, 854 00:46:43,133 --> 00:46:46,000 the team needs more evidence. 855 00:46:50,200 --> 00:46:55,900 Taaniela will use a drone to investigate the active cone. 856 00:46:57,366 --> 00:47:00,633 While the rest of the team will collect vital readings, 857 00:47:00,633 --> 00:47:04,566 which need to be taken from inside the caldera itself. 858 00:47:05,966 --> 00:47:09,800 ♪ ♪ 859 00:47:15,833 --> 00:47:21,133 CRONIN: I'm going to try and get a position close to the plume. 860 00:47:21,133 --> 00:47:23,333 I don't want to go underneath it, 861 00:47:23,333 --> 00:47:26,700 because sulfur dioxide is actually quite lethal. 862 00:47:26,700 --> 00:47:29,866 We can then try to measure some of the output. 863 00:47:34,000 --> 00:47:36,833 This is what I've been lugging up the hill. 864 00:47:38,566 --> 00:47:41,500 NARRATOR: Volcanologists monitor the sulfur dioxide 865 00:47:41,500 --> 00:47:45,400 to gauge the activity of volcanoes. 866 00:47:45,400 --> 00:47:48,366 CRONIN: This is the telescope. 867 00:47:48,366 --> 00:47:49,966 And it's a rotating one. 868 00:47:49,966 --> 00:47:52,266 NARRATOR: The more sulfur dioxide 869 00:47:52,266 --> 00:47:54,000 Shane detects, the more active 870 00:47:54,000 --> 00:47:55,633 the volcano. 871 00:47:55,633 --> 00:47:56,833 Now... 872 00:47:58,633 --> 00:48:00,633 It's going to be scanning over there, 873 00:48:00,633 --> 00:48:02,033 and I want it to scan above the level 874 00:48:02,033 --> 00:48:04,166 of the opposite caldera rim. 875 00:48:06,533 --> 00:48:09,366 We're capturing it beautifully with this angle. 876 00:48:09,366 --> 00:48:15,400 ♪ ♪ 877 00:48:15,400 --> 00:48:17,633 NARRATOR: Shane's readings indicate the satellites have been 878 00:48:17,633 --> 00:48:20,933 dangerously underestimating the levels of sulfur dioxide. 879 00:48:23,066 --> 00:48:27,100 Tofua is releasing far more than previously thought. 880 00:48:27,100 --> 00:48:33,100 ♪ ♪ 881 00:48:33,100 --> 00:48:35,933 Taaniela's expert flying reveals that 882 00:48:35,933 --> 00:48:39,933 the magma has welled up in the crater, 883 00:48:39,933 --> 00:48:42,833 creating a lava lake, 884 00:48:42,833 --> 00:48:47,400 one of fewer than ten on the entire planet. 885 00:48:52,033 --> 00:48:56,200 And there's a sign Tofua has been actively throwing out lava, 886 00:48:56,200 --> 00:48:58,433 incredibly recently. 887 00:48:58,433 --> 00:49:02,033 CRONIN: This erupted in the last few days. 888 00:49:02,033 --> 00:49:03,566 It's a fresh volcanic bomb. 889 00:49:03,566 --> 00:49:05,866 So this really contrasts to 890 00:49:05,866 --> 00:49:07,866 all of the rest of the older material around here. 891 00:49:07,866 --> 00:49:13,066 So there's been some quite big explosions to produce these. 892 00:49:13,066 --> 00:49:15,666 It's really interesting, because it looks as if 893 00:49:15,666 --> 00:49:17,300 Tofua is entering a new phase of activity, 894 00:49:17,300 --> 00:49:20,300 one that we haven't seen here before. 895 00:49:20,300 --> 00:49:23,033 ♪ ♪ 896 00:49:23,033 --> 00:49:24,933 Everything that we've discovered today 897 00:49:24,933 --> 00:49:27,333 is absolutely new, and I think will be 898 00:49:27,333 --> 00:49:30,733 quite a shock around the globe. 899 00:49:32,233 --> 00:49:34,433 NARRATOR: Tonga is still recovering 900 00:49:34,433 --> 00:49:38,633 from the eruption of the Hunga volcano. 901 00:49:38,633 --> 00:49:40,966 Now scientists have discovered 902 00:49:40,966 --> 00:49:43,233 that its volcanic twin, Tofua, 903 00:49:43,233 --> 00:49:44,800 is far more active 904 00:49:44,800 --> 00:49:48,266 than satellites have led them to believe, 905 00:49:48,266 --> 00:49:52,900 a finding that has implications far beyond Tonga. 906 00:49:52,900 --> 00:49:55,166 ♪ ♪ 907 00:49:58,133 --> 00:50:02,300 KULA: Our latest expedition really showed us 908 00:50:02,300 --> 00:50:06,533 there are limitations of the satellite system. 909 00:50:06,533 --> 00:50:10,566 You always need to be on-site to actually know 910 00:50:10,566 --> 00:50:15,133 the full level of the volcanic activity. 911 00:50:16,533 --> 00:50:21,266 NARRATOR: With as many as 50,000 submarine volcanoes around the planet, 912 00:50:21,266 --> 00:50:23,400 the world needs to find better ways of 913 00:50:23,400 --> 00:50:26,933 keeping an eye on these destructive forces of nature. 914 00:50:26,933 --> 00:50:31,300 ♪ ♪ 915 00:50:31,300 --> 00:50:34,100 And be ready 916 00:50:34,100 --> 00:50:36,800 for the next Hunga Tonga-Hunga Ha'apai. 917 00:50:36,800 --> 00:50:40,466 (people exclaiming) 918 00:50:40,466 --> 00:50:42,700 (speaking Tongan): 919 00:50:42,700 --> 00:50:44,966 NARRATOR: Taaniela and his colleagues 920 00:50:44,966 --> 00:50:47,933 have long reached out to people of Tonga. 921 00:50:47,933 --> 00:50:51,033 ANA MAEA (speaking Tongan): 922 00:50:51,033 --> 00:50:52,666 PUPILS: 923 00:50:52,666 --> 00:50:55,500 KULA: We feel that it's our responsibility 924 00:50:55,500 --> 00:50:59,400 to build awareness about geological hazards and risks 925 00:50:59,400 --> 00:51:03,000 that we are exposed to. 926 00:51:03,000 --> 00:51:04,700 NARRATOR: It's a strategy that 927 00:51:04,700 --> 00:51:07,166 the rest of the world could learn from. 928 00:51:07,166 --> 00:51:08,900 MAEA: 929 00:51:13,300 --> 00:51:15,633 NARRATOR: Awareness is a major reason 930 00:51:15,633 --> 00:51:17,533 just three people died in Tonga 931 00:51:17,533 --> 00:51:20,266 during the Hunga volcano disaster. 932 00:51:20,266 --> 00:51:23,300 BORRERO: The death toll was so low 933 00:51:23,300 --> 00:51:26,266 because of the knowledge of tsunami. 934 00:51:26,266 --> 00:51:27,633 Everybody moved to high ground, 935 00:51:27,633 --> 00:51:29,033 they alerted their neighbors, 936 00:51:29,033 --> 00:51:31,033 they alerted their friends, and everybody evacuated. 937 00:51:31,033 --> 00:51:33,433 It's miraculous, 938 00:51:33,433 --> 00:51:35,566 but it's doing the right thing at the right time. 939 00:51:35,566 --> 00:51:41,200 ♪ ♪ 940 00:51:41,200 --> 00:51:42,733 KULA: Our existence today is 941 00:51:42,733 --> 00:51:44,933 a demonstration of our resilience. 942 00:51:44,933 --> 00:51:47,800 ♪ ♪ 943 00:51:47,800 --> 00:51:51,800 And I think knowledge will increase the resilience 944 00:51:51,800 --> 00:51:54,100 of the people in the world. 945 00:51:54,100 --> 00:51:55,833 (crowd cheering) 946 00:51:55,833 --> 00:51:57,833 NARRATOR: Being ready 947 00:51:57,833 --> 00:52:01,766 is Tonga's lesson for the rest of the planet. 948 00:52:01,766 --> 00:52:03,666 (cheering) 949 00:52:20,800 --> 00:52:28,333 ♪ ♪ 950 00:52:32,166 --> 00:52:39,700 ♪ ♪ 951 00:52:41,333 --> 00:52:48,866 ♪ ♪ 952 00:52:50,500 --> 00:52:58,033 ♪ ♪ 953 00:53:03,833 --> 00:53:11,000 ♪ ♪