1 00:00:15,000 --> 00:00:17,300 This is really exciting. 2 00:00:18,900 --> 00:00:20,500 We've been sitting in the UK 3 00:00:20,500 --> 00:00:24,380 waiting for just the right snow conditions for ages. 4 00:00:24,380 --> 00:00:28,220 Then, two days ago, we got the call to say that now is the time. 5 00:00:28,220 --> 00:00:31,140 So, here we are, about to set off an avalanche 6 00:00:31,140 --> 00:00:33,100 just there, on that mountain. 7 00:00:36,820 --> 00:00:39,940 Avalanches are unstoppable forces of nature 8 00:00:39,940 --> 00:00:42,500 that kill hundreds of people every year. 9 00:00:43,980 --> 00:00:47,300 It was kind of a bloodcurdling feeling, really. 10 00:00:47,300 --> 00:00:49,340 I had snow jammed down my throat, 11 00:00:49,340 --> 00:00:52,060 in my eyes, up my nose, 12 00:00:52,060 --> 00:00:54,420 and I really, really needed air. 13 00:00:58,100 --> 00:01:02,700 Even in Britain, around 30 people have lost their lives to avalanches 14 00:01:02,700 --> 00:01:04,860 since the year 2000. 15 00:01:04,860 --> 00:01:07,540 Yet we know surprisingly little about them. 16 00:01:07,540 --> 00:01:10,380 We can't predict when or where they'll strike, 17 00:01:10,380 --> 00:01:13,060 or how big or devastating they'll be. 18 00:01:14,260 --> 00:01:17,700 I'm Danielle George, an engineer and physicist... 19 00:01:17,700 --> 00:01:19,060 Wow! 20 00:01:19,060 --> 00:01:22,220 I've never been in a room where it's snowing. 21 00:01:22,220 --> 00:01:25,060 ..and I've gathered an international team of scientists 22 00:01:25,060 --> 00:01:29,260 in the Canadian Rockies for a unique and dangerous mission. 23 00:01:30,700 --> 00:01:33,020 We're going to rig an entire mountain 24 00:01:33,020 --> 00:01:35,100 with cameras and instruments, 25 00:01:35,100 --> 00:01:39,300 and then we're going to load this helicopter with explosives... 26 00:01:39,300 --> 00:01:41,020 Good luck, boys. 27 00:01:41,020 --> 00:01:42,380 Thanks. 28 00:01:42,380 --> 00:01:45,420 ..and use it to send a massive avalanche hurtling 29 00:01:45,420 --> 00:01:46,740 down these slopes. 30 00:01:48,540 --> 00:01:50,700 We want to find out why avalanches happen, 31 00:01:50,700 --> 00:01:52,180 where they will strike... 32 00:01:52,180 --> 00:01:53,460 So she's dropping... 33 00:01:53,460 --> 00:01:56,460 ..and why some of them become devastating killers. 34 00:01:56,460 --> 00:01:59,740 Are you OK? Big, deep breath. Yeah. You survived an avalanche. 35 00:01:59,740 --> 00:02:01,020 That is a truly... 36 00:02:05,100 --> 00:02:07,380 ..frightening experience. 37 00:02:07,380 --> 00:02:11,900 No-one has attempted an experiment quite like this before. 38 00:02:11,900 --> 00:02:15,460 If it works, it will revolutionise our ability to predict 39 00:02:15,460 --> 00:02:17,140 and prevent avalanches. 40 00:02:17,140 --> 00:02:18,660 OK. Here we go. 41 00:02:20,460 --> 00:02:22,220 Wow, look at that! 42 00:02:49,420 --> 00:02:52,860 It's early on a Sunday morning, in March 2018, 43 00:02:52,860 --> 00:02:56,740 and a team of snow scientists arrives in a remote valley 44 00:02:56,740 --> 00:02:58,580 in the Canadian Rockies. 45 00:03:03,660 --> 00:03:07,860 For many, this is their first sight of The Fortress, 46 00:03:07,860 --> 00:03:11,260 a 3,000m peak in the Kananaskis Range. 47 00:03:13,180 --> 00:03:15,420 We've brought these scientists here now 48 00:03:15,420 --> 00:03:17,300 because, for the next few days, 49 00:03:17,300 --> 00:03:19,780 the avalanche risk will be at its highest. 50 00:03:23,060 --> 00:03:26,900 We had about 45cm of snowfall this past week, 51 00:03:26,900 --> 00:03:30,140 and we're heading into another warm-up cycle here. 52 00:03:30,140 --> 00:03:32,380 You know, pretty concerned about the hazard. 53 00:03:32,380 --> 00:03:34,980 I think we'll see a lot of activity in the next couple of days. 54 00:03:37,860 --> 00:03:39,820 OK, so, you see those two trails? 55 00:03:39,820 --> 00:03:42,460 I think that might be a good place for a scan location. 56 00:03:42,460 --> 00:03:44,380 Over the next two days, 57 00:03:44,380 --> 00:03:47,020 the team will be surveying the mountain... 58 00:03:47,020 --> 00:03:48,900 One of the things that's really interesting 59 00:03:48,900 --> 00:03:50,620 is the snow stays so much colder at the top 60 00:03:50,620 --> 00:03:51,900 than lower down the mountain, 61 00:03:51,900 --> 00:03:53,380 that affects how fast it moves. 62 00:03:54,460 --> 00:03:59,220 ..trying to learn all they can about the snow conditions, 63 00:03:59,220 --> 00:04:02,460 before we trigger what will be one of the most closely-studied 64 00:04:02,460 --> 00:04:04,380 avalanches of all time. 65 00:04:04,380 --> 00:04:07,180 All right, that's it. Installed. 66 00:04:13,420 --> 00:04:17,340 We've designed this experiment to fulfil three key aims. 67 00:04:20,820 --> 00:04:24,620 First, we want to test our understanding of avalanches 68 00:04:24,620 --> 00:04:27,900 by trying to predict the size, path and power 69 00:04:27,900 --> 00:04:30,100 of the one that we're going to set off. 70 00:04:32,180 --> 00:04:34,660 Second, by studying that avalanche, 71 00:04:34,660 --> 00:04:37,260 we want to learn more about how they work, 72 00:04:37,260 --> 00:04:40,180 why they start and how they do so much damage... 73 00:04:42,420 --> 00:04:46,900 ..and thirdly, I want to understand the human cost of avalanches. 74 00:04:49,660 --> 00:04:52,340 Whilst the other guys investigate the avalanche remotely, 75 00:04:52,340 --> 00:04:55,060 I'm going to be getting hands-on with the snow, 76 00:04:55,060 --> 00:04:58,460 finding out what it's really like to be caught in an avalanche. 77 00:04:59,940 --> 00:05:02,540 I want to know what makes them so dangerous, 78 00:05:02,540 --> 00:05:05,620 and if there's anything we can do to survive them. 79 00:05:07,460 --> 00:05:10,140 The star of the show will be this car, 80 00:05:10,140 --> 00:05:12,780 which is going to become a mobile laboratory. 81 00:05:14,340 --> 00:05:16,420 We're going to rig it with sensors, 82 00:05:16,420 --> 00:05:19,900 and then drop it into the surging heart of the avalanche. 83 00:05:22,380 --> 00:05:26,660 If it all works, we will come away with valuable new information 84 00:05:26,660 --> 00:05:28,620 that could help save lives. 85 00:05:34,540 --> 00:05:36,980 We're in a real race against time here. 86 00:05:36,980 --> 00:05:39,980 The slopes above us are covered in fresh snow, 87 00:05:39,980 --> 00:05:42,340 so they are primed for avalanches. 88 00:05:42,340 --> 00:05:44,620 At any time, that snow could come at us, 89 00:05:44,620 --> 00:05:48,340 so we don't want to be down here for longer than absolutely necessary. 90 00:05:48,340 --> 00:05:51,260 So, we need to get this experiment ready and done. 91 00:05:51,260 --> 00:05:53,180 The worst thing that could happen 92 00:05:53,180 --> 00:05:56,980 is that the avalanche triggers spontaneously before we're ready. 93 00:05:56,980 --> 00:06:00,380 So I think, realistically, we've got about 48 hours 94 00:06:00,380 --> 00:06:02,620 to get everything in place. 95 00:06:02,620 --> 00:06:04,180 It's going to be busy. 96 00:06:14,700 --> 00:06:17,260 The next two days will not just be busy, 97 00:06:17,260 --> 00:06:19,140 they'll also be dangerous. 98 00:06:22,220 --> 00:06:25,940 The team will be working in an active avalanche zone. 99 00:06:28,420 --> 00:06:31,140 So, to prepare us for the possibility of being caught 100 00:06:31,140 --> 00:06:34,620 in an avalanche, the day starts with a safety briefing 101 00:06:34,620 --> 00:06:38,700 from local guide and avalanche forecaster Jason Kuruc. 102 00:06:38,700 --> 00:06:40,260 All right, folks, 103 00:06:40,260 --> 00:06:42,420 I just want to take the next few minutes 104 00:06:42,420 --> 00:06:45,220 and show you some of the avalanche safety equipment 105 00:06:45,220 --> 00:06:46,500 that we're going to be using. 106 00:06:46,500 --> 00:06:49,420 We're going to start off with the transceivers. 107 00:06:49,420 --> 00:06:51,660 Danielle, can I ask you to help me out here? Yeah. 108 00:06:51,660 --> 00:06:54,300 So, we're going to put it on underneath your top layer. OK. 109 00:06:54,300 --> 00:06:56,180 So, we're just going to put it over your arm 110 00:06:56,180 --> 00:06:57,460 and then over your head, 111 00:06:57,460 --> 00:07:00,540 and then we'll snug it up, so it's sitting right about here. 112 00:07:00,540 --> 00:07:01,820 I'm going to hand out... 113 00:07:01,820 --> 00:07:03,500 These portable transceivers 114 00:07:03,500 --> 00:07:06,220 are the most important piece of equipment we have. 115 00:07:07,740 --> 00:07:09,540 If any of us are buried in an avalanche, 116 00:07:09,540 --> 00:07:12,820 they'll send out a signal that will alert the rescuers to our position. 117 00:07:15,100 --> 00:07:18,300 For those of us not used to working in the mountains, 118 00:07:18,300 --> 00:07:20,180 it's a daunting prospect. 119 00:07:20,180 --> 00:07:21,780 So, I have a question. 120 00:07:21,780 --> 00:07:24,260 What should I do if I get caught in an avalanche? 121 00:07:24,260 --> 00:07:28,380 So, you want to be trying to do this back crawl swimming motion 122 00:07:28,380 --> 00:07:32,060 to try and keep yourself at the surface of the snow, 123 00:07:32,060 --> 00:07:34,180 and at the very last moment, 124 00:07:34,180 --> 00:07:37,180 when you feel yourself stopping moving, 125 00:07:37,180 --> 00:07:40,260 you want to try and punch a hand up, as well. 126 00:07:40,260 --> 00:07:42,980 That might help us to find you easier. 127 00:07:42,980 --> 00:07:44,140 I feel quite breathless. 128 00:07:44,140 --> 00:07:46,180 You know, when you're talking about it... Mm-hm. 129 00:07:46,180 --> 00:07:48,380 ..you know, the feeling of being buried, I'm like... 130 00:07:48,380 --> 00:07:50,140 SHE HYPERVENTILATES You know, panicking. 131 00:07:50,140 --> 00:07:52,380 Yeah, it can be... 132 00:07:52,380 --> 00:07:56,860 ..the most exciting and worst few minutes of your life, for sure. 133 00:08:03,820 --> 00:08:06,540 To get some idea of the devastating impact 134 00:08:06,540 --> 00:08:10,580 of being caught in an avalanche, we have to leave The Fortress 135 00:08:10,580 --> 00:08:14,100 and go to the quiet college town of Missoula, Montana. 136 00:08:16,780 --> 00:08:20,260 Avalanches had never been an issue here, 137 00:08:20,260 --> 00:08:24,140 but in early 2014, the town had become a winter wonderland. 138 00:08:25,620 --> 00:08:29,100 It had snowed for 16 of the 28 days of February... 139 00:08:31,980 --> 00:08:34,980 ..and everyone wanted to make the most of it. 140 00:08:36,940 --> 00:08:38,780 So, about four o'clock in the afternoon, 141 00:08:38,780 --> 00:08:42,020 I'd just gotten home, I was sitting inside the front room here, 142 00:08:42,020 --> 00:08:44,140 and the kids asked to come out and play. 143 00:08:44,140 --> 00:08:45,780 And I said, "Sure, go play." 144 00:08:45,780 --> 00:08:48,060 And it was about five minutes after that, 145 00:08:48,060 --> 00:08:50,060 I heard a noise coming around the corner here. 146 00:08:50,060 --> 00:08:52,620 And it sounded like a plough truck that was ploughing snow, 147 00:08:52,620 --> 00:08:55,340 like, coming round on this back road, which was really weird, 148 00:08:55,340 --> 00:08:57,700 because they weren't even ploughing the main streets, 149 00:08:57,700 --> 00:08:58,780 the weather was so crazy. 150 00:09:01,780 --> 00:09:03,820 It felt like an earthquake. 151 00:09:03,820 --> 00:09:05,820 It shook the whole house. 152 00:09:07,900 --> 00:09:09,460 You could hear the windows shudder. 153 00:09:10,980 --> 00:09:15,620 And I saw this plume of white snow, it looked like smoke in the air, 154 00:09:15,620 --> 00:09:17,260 just almost like a whiteout. 155 00:09:22,620 --> 00:09:24,860 My wife and I were just sitting in the living room 156 00:09:24,860 --> 00:09:27,980 and thinking about what we were going to do for dinner that night, 157 00:09:27,980 --> 00:09:31,340 and all of a sudden, and instantaneously, 158 00:09:31,340 --> 00:09:34,180 I went from sitting on the couch 159 00:09:34,180 --> 00:09:35,940 to being covered by my house. 160 00:09:38,700 --> 00:09:40,300 It was like a bomb went off, 161 00:09:40,300 --> 00:09:42,180 and my house was sitting on top of me. 162 00:09:43,700 --> 00:09:45,740 And within seconds, I heard my wife screaming, 163 00:09:45,740 --> 00:09:47,580 and, you know, I said, "What's going on?" 164 00:09:47,580 --> 00:09:50,060 and she was just screaming, "My babies, my babies!" 165 00:09:51,180 --> 00:09:54,340 A river of snow had come sweeping off the mountain, 166 00:09:54,340 --> 00:09:58,740 flattening Fred Allendorf's house and burying Casey's kids. 167 00:10:01,940 --> 00:10:04,940 Ten-year-old Coral clambered out unharmed, 168 00:10:04,940 --> 00:10:08,500 but there was no sign of eight-year-old Phoenix. 169 00:10:19,780 --> 00:10:22,100 I saw the lady scrambling about 170 00:10:22,100 --> 00:10:25,700 and wondering what the heck had happened to her son. 171 00:10:30,300 --> 00:10:31,780 I know the statistics. 172 00:10:31,780 --> 00:10:34,180 People don't live that long underneath snow. 173 00:10:34,180 --> 00:10:36,020 You know, it's like, you're sitting there, 174 00:10:36,020 --> 00:10:40,860 you're trying to tell your wife that he's still alive 175 00:10:40,860 --> 00:10:43,220 and, like, really, you know that he's dead. 176 00:10:47,340 --> 00:10:49,740 I was lying there, thinking that either 177 00:10:49,740 --> 00:10:51,980 I was going to suffocate, freeze to death 178 00:10:51,980 --> 00:10:53,740 or somebody's going to find me. 179 00:10:55,620 --> 00:10:58,060 People were coming up with shovels and avalanche probes. 180 00:10:58,060 --> 00:11:00,780 People were shouting out stuff. There was live electric wires. 181 00:11:00,780 --> 00:11:02,580 So, it was quite chaotic. 182 00:11:09,180 --> 00:11:11,540 It was quite a long time before they actually found him - 183 00:11:11,540 --> 00:11:12,700 45 minutes. 184 00:11:14,260 --> 00:11:16,700 He ended up being trapped in this window down here, 185 00:11:16,700 --> 00:11:17,900 in an air pocket. 186 00:11:17,900 --> 00:11:20,420 He was pushed up against the window in an air pocket, 187 00:11:20,420 --> 00:11:22,460 and that's actually what kept him alive. 188 00:11:22,460 --> 00:11:25,460 So, it's almost a miracle that he survived. 189 00:11:30,100 --> 00:11:32,540 And while Phoenix was rushed to hospital, 190 00:11:32,540 --> 00:11:35,540 the search continued for Fred Allendorf and his wife. 191 00:11:37,540 --> 00:11:40,780 We started off five feet away from one another, 192 00:11:40,780 --> 00:11:44,420 and my understanding is she was found about 20m away, 193 00:11:44,420 --> 00:11:47,740 and she was obviously really hypothermic, 194 00:11:47,740 --> 00:11:50,980 and she had lots of internal injuries. 195 00:11:50,980 --> 00:11:55,380 And that was on Friday afternoon, and she died two days later. 196 00:12:03,780 --> 00:12:06,820 The striking thing about the Missoula avalanche 197 00:12:06,820 --> 00:12:08,740 is that it came out of the blue. 198 00:12:08,740 --> 00:12:11,540 No-one had thought the town was in danger. 199 00:12:15,300 --> 00:12:17,980 One of the main reasons we're doing this experiment 200 00:12:17,980 --> 00:12:21,020 is to prevent similar tragedies happening in the future, 201 00:12:21,020 --> 00:12:25,300 by developing a new scientific way of understanding avalanches... 202 00:12:29,380 --> 00:12:31,540 ..but there's a worrying trend 203 00:12:31,540 --> 00:12:34,580 that suggests more areas could soon be at risk. 204 00:12:36,020 --> 00:12:38,740 Until recently, we used historical records 205 00:12:38,740 --> 00:12:40,740 to tell us where the danger was. 206 00:12:41,980 --> 00:12:44,980 Mountain valleys were mapped, showing in red the areas 207 00:12:44,980 --> 00:12:47,980 that avalanches had devastated in the past. 208 00:12:50,020 --> 00:12:52,540 It allowed us to say which areas were safe 209 00:12:52,540 --> 00:12:54,340 and which were in danger... 210 00:12:55,620 --> 00:12:59,540 ..but these historical records are no longer so useful. 211 00:12:59,540 --> 00:13:01,540 The climate's changing now. 212 00:13:01,540 --> 00:13:04,420 This is changing when the snow falls and when the snow melts, 213 00:13:04,420 --> 00:13:07,740 and in some areas there could be many more destructive avalanches. 214 00:13:07,740 --> 00:13:09,580 Other places, there could be fewer. 215 00:13:10,900 --> 00:13:14,220 It's because we can't rely on the historical records any more 216 00:13:14,220 --> 00:13:17,260 that we desperately need to find new ways of predicting 217 00:13:17,260 --> 00:13:21,580 where avalanches will strike and the amount of damage they'll do... 218 00:13:25,780 --> 00:13:27,140 Hi, Jason. 219 00:13:33,540 --> 00:13:36,100 ..but before the serious science can start, 220 00:13:36,100 --> 00:13:40,380 we need to choose the perfect site to trigger our avalanche. 221 00:13:40,380 --> 00:13:42,580 So I've hitched a ride with Jason 222 00:13:42,580 --> 00:13:44,860 to scout out the mountain from the air. 223 00:14:01,260 --> 00:14:04,340 So, how do we choose which avalanche path will be good? 224 00:14:04,340 --> 00:14:07,740 We need a lot of snow up high, in the start zones, 225 00:14:07,740 --> 00:14:13,180 and we need a slope angle greater than 35 degrees, ideally, 226 00:14:13,180 --> 00:14:15,420 up to about 45, 50 degrees. 227 00:14:17,500 --> 00:14:20,180 The first site we look at is called JSP. 228 00:14:20,180 --> 00:14:23,060 Perched on the wide-open slopes of the mountain, 229 00:14:23,060 --> 00:14:25,180 it doesn't look threatening. 230 00:14:25,180 --> 00:14:29,460 There's probably two or three metres of snow just in here. 231 00:14:29,460 --> 00:14:32,660 So, if we were to put explosives across the top here, 232 00:14:32,660 --> 00:14:37,300 that could potentially make it propagate across this whole bowl, 233 00:14:37,300 --> 00:14:42,340 and then all of this snow down here would start falling downhill. 234 00:14:42,340 --> 00:14:45,420 And it's great that we can actually see all the way down, 235 00:14:45,420 --> 00:14:49,460 so we can actually see the path of where the snow might go 236 00:14:49,460 --> 00:14:52,300 on this avalanche as well, all the way down to the road. 237 00:14:52,300 --> 00:14:54,620 So, is that a good site? 238 00:14:54,620 --> 00:14:56,940 It could be a good site, but I'd like to see 239 00:14:56,940 --> 00:14:58,260 a few more options. 240 00:14:59,420 --> 00:15:02,500 The next site we look at is called A Gully. 241 00:15:02,500 --> 00:15:04,580 It looks far more dramatic. 242 00:15:05,660 --> 00:15:07,820 Oh, wow, what about this? 243 00:15:07,820 --> 00:15:11,500 Oh, that's a massive cornice, a couple of metres thick there. 244 00:15:11,500 --> 00:15:14,060 That snow is very, very dense. 245 00:15:14,060 --> 00:15:16,780 You can see how, if we were to put explosives 246 00:15:16,780 --> 00:15:18,900 on the back side of the cornice, 247 00:15:18,900 --> 00:15:22,940 that would cause it to fail and fall onto the slope below it, 248 00:15:22,940 --> 00:15:24,740 to create an avalanche. 249 00:15:28,220 --> 00:15:31,140 Back on the ground, it's time to make the big decision - 250 00:15:31,140 --> 00:15:33,420 where should we set off our avalanche? 251 00:15:33,420 --> 00:15:36,060 You wanted to see the cornices on A Gully. A Gully. 252 00:15:36,060 --> 00:15:39,060 They were massive, what, a few metres? 253 00:15:39,060 --> 00:15:43,180 It is loaded with some snow, but I don't think it has the same 254 00:15:43,180 --> 00:15:46,460 amount of snow as the JSP path. I think... 255 00:15:46,460 --> 00:15:49,060 Oh, well, that's quite interesting, cos I thought on A Gully, 256 00:15:49,060 --> 00:15:51,660 because the cornices were so big, then that would probably be 257 00:15:51,660 --> 00:15:53,540 a really good site, but you're saying you need 258 00:15:53,540 --> 00:15:54,980 more than just the cornice to... 259 00:15:54,980 --> 00:15:56,700 Yeah, you want the whole lot. 260 00:15:56,700 --> 00:15:58,980 If there's slabs at JSP, then it could fracture 261 00:15:58,980 --> 00:16:00,940 across the whole bowl and it could be quite big - 262 00:16:00,940 --> 00:16:02,020 but if it's A Gully, 263 00:16:02,020 --> 00:16:04,900 maybe it's just going to be the local snow, much smaller. 264 00:16:04,900 --> 00:16:08,100 So, it sounds like both of you are saying the same thing, then. 265 00:16:08,100 --> 00:16:09,580 Both of you are saying JSP. 266 00:16:09,580 --> 00:16:12,460 JSP seems like the better bet, but there's no guarantees 267 00:16:12,460 --> 00:16:15,020 in this game. Very true. 268 00:16:15,020 --> 00:16:18,780 JSP looks to be the ideal location for our avalanche. 269 00:16:20,020 --> 00:16:24,220 We know the bowl at the top of the run is filled with deep snow, 270 00:16:24,220 --> 00:16:26,660 but that's not necessarily enough. 271 00:16:34,660 --> 00:16:37,180 If it's going to produce a major avalanche, 272 00:16:37,180 --> 00:16:40,340 that snow needs to contain another critical ingredient. 273 00:16:41,500 --> 00:16:44,700 To find out what that is, I have to travel several hundred 274 00:16:44,700 --> 00:16:47,020 miles south to Bozeman, Montana. 275 00:16:49,500 --> 00:16:53,980 It's home to a unique facility, the Subzero Lab. 276 00:16:53,980 --> 00:16:55,700 OK? Yeah. 277 00:16:55,700 --> 00:16:58,340 It's run by snow scientist Ed Adams. 278 00:16:59,860 --> 00:17:03,140 Wow! I've never been in a room where it's snowing. 279 00:17:04,300 --> 00:17:06,100 What is this room, Ed? 280 00:17:06,100 --> 00:17:09,780 It's a cold lab, and what we're trying to do with it 281 00:17:09,780 --> 00:17:12,820 is simulate nature, as well as we can, 282 00:17:12,820 --> 00:17:14,220 in a winter environment. 283 00:17:14,220 --> 00:17:17,340 Our primary interest is in avalanches. 284 00:17:17,340 --> 00:17:20,340 In the lab today, Ed is performing an experiment 285 00:17:20,340 --> 00:17:22,740 to show how the vast power of avalanches 286 00:17:22,740 --> 00:17:26,540 originates in tiny changes in the structure of ice crystals. 287 00:17:28,780 --> 00:17:33,380 It's something I hadn't appreciated until...until I've come here. 288 00:17:33,380 --> 00:17:36,860 Snow is a very dynamic material. 289 00:17:36,860 --> 00:17:38,860 I call it a shapeshifter. 290 00:17:38,860 --> 00:17:41,660 It's really the hardest stuff to predict. 291 00:17:46,580 --> 00:17:49,940 Ed starts with a typical solid layer of snow... 292 00:17:51,660 --> 00:17:55,740 ..but then he dramatically cools the air to -10 degrees 293 00:17:55,740 --> 00:17:59,340 to simulate the conditions on a cold, clear night... 294 00:18:00,900 --> 00:18:03,100 ..and within minutes, the surface of the snow 295 00:18:03,100 --> 00:18:04,460 starts to change. 296 00:18:07,340 --> 00:18:11,220 It sprouts feather-like crystals called surface hoar, 297 00:18:11,220 --> 00:18:13,300 the frozen equivalent of dew. 298 00:18:15,860 --> 00:18:19,900 It seems unlikely, but when they're buried under more snow, 299 00:18:19,900 --> 00:18:22,900 these delicate, even beautiful crystals, 300 00:18:22,900 --> 00:18:27,020 become the crucial ingredient needed to trigger avalanches. 301 00:18:30,620 --> 00:18:33,740 To see how that happens, we need to put a sample of the snow 302 00:18:33,740 --> 00:18:35,220 into a CT scanner. 303 00:18:43,180 --> 00:18:45,940 So, this is that first layer that we put in as our base layer - 304 00:18:45,940 --> 00:18:47,620 that's going to be our bottom - 305 00:18:47,620 --> 00:18:50,380 and there's lots of strong interconnections between this. 306 00:18:50,380 --> 00:18:51,700 So, this is a strong layer. 307 00:18:51,700 --> 00:18:55,500 As you said, it appears strong, and it is relatively strong. 308 00:18:55,500 --> 00:18:59,620 The CT scan shows how tightly bonded the strong layer is. 309 00:18:59,620 --> 00:19:03,420 Each crystal forms several sturdy connections to the others around it, 310 00:19:03,420 --> 00:19:05,060 creating a solid slab... 311 00:19:06,860 --> 00:19:09,900 ..but the surface hoar is very different. 312 00:19:09,900 --> 00:19:12,620 There's no solid network of bonds. 313 00:19:12,620 --> 00:19:14,900 Instead, each feather-like crystal 314 00:19:14,900 --> 00:19:18,700 only has one delicate point of contact with the layer below. 315 00:19:20,540 --> 00:19:24,260 We've got these large crystals with a very small attachment point, 316 00:19:24,260 --> 00:19:26,980 so they do tend to be very weak, particularly in shear, 317 00:19:26,980 --> 00:19:29,060 so when you put it on a slope, they tend to want to fail. 318 00:19:29,060 --> 00:19:30,660 That's what causes the avalanche? 319 00:19:30,660 --> 00:19:32,660 That's when the avalanche takes off, yep. 320 00:19:36,500 --> 00:19:39,260 Surface hoar is just one of several types of weak layer 321 00:19:39,260 --> 00:19:41,540 that can form in the snow - 322 00:19:41,540 --> 00:19:45,300 and they all trigger avalanches in the same way. 323 00:19:47,300 --> 00:19:49,940 When those fragile crystals start to fracture, 324 00:19:49,940 --> 00:19:53,660 they set off a chain reaction that quickly spreads... 325 00:19:55,980 --> 00:19:58,420 ..severing the connection to the layer below 326 00:19:58,420 --> 00:20:01,740 and allowing all the snow on top to slide downhill... 327 00:20:03,580 --> 00:20:07,100 ..and when that happens, disaster is never far away. 328 00:20:10,460 --> 00:20:12,180 Ten seconds. 329 00:20:14,900 --> 00:20:19,660 In 2003, snowboarder Johno Verity was in New Zealand 330 00:20:19,660 --> 00:20:21,500 when catastrophe unfolded. 331 00:20:25,740 --> 00:20:29,260 All of the slope was breaking up into cubes of snow. 332 00:20:32,340 --> 00:20:35,580 A hidden weak layer had fractured right underneath him. 333 00:20:38,220 --> 00:20:40,540 It started kind of undulating. 334 00:20:43,860 --> 00:20:46,420 It became a river of snow. 335 00:20:47,580 --> 00:20:49,500 Where's Johno, where's Johno? 336 00:20:51,340 --> 00:20:54,660 It was kind of a bloodcurdling feeling, really. 337 00:20:55,780 --> 00:21:00,500 I had snow jammed down my throat, in my eyes, up my nose, 338 00:21:00,500 --> 00:21:02,820 and I really, really needed air. 339 00:21:08,980 --> 00:21:10,340 Are you OK? 340 00:21:11,780 --> 00:21:14,180 HE PANTS 341 00:21:19,100 --> 00:21:21,220 If we're to succeed in our mission, 342 00:21:21,220 --> 00:21:23,380 we need there to be a similar weak layer 343 00:21:23,380 --> 00:21:25,540 hidden beneath the surface of JSP, 344 00:21:25,540 --> 00:21:27,540 which we can break with our explosives. 345 00:21:29,340 --> 00:21:32,100 Finding it is the next step of our experiment. 346 00:21:43,140 --> 00:21:45,340 The next morning, back on The Fortress, 347 00:21:45,340 --> 00:21:48,660 Scott Havens has climbed to the top of the mountain 348 00:21:48,660 --> 00:21:50,860 in search of that crucial weak layer. 349 00:21:54,460 --> 00:21:56,780 In these conditions, one wrong step 350 00:21:56,780 --> 00:21:58,660 could trigger an avalanche. 351 00:22:03,420 --> 00:22:05,220 So, what we do when we dig a pit... 352 00:22:07,220 --> 00:22:09,540 Cos we're looking for what's happened 353 00:22:09,540 --> 00:22:12,220 over the entire season within the snowpack. 354 00:22:13,980 --> 00:22:17,460 Once they're buried, weak layers are notoriously hard to find. 355 00:22:20,180 --> 00:22:23,940 It's one of the reasons avalanches are so hard to predict. 356 00:22:23,940 --> 00:22:27,940 The most reliable way of finding them is to dig a pit like this. 357 00:22:27,940 --> 00:22:30,860 It reveals the history of the snowpack 358 00:22:30,860 --> 00:22:33,700 that's accumulated over the winter, 359 00:22:33,700 --> 00:22:35,940 and by testing its consistency, 360 00:22:35,940 --> 00:22:39,780 Scott can search for the existence of any weak layers. 361 00:22:39,780 --> 00:22:43,420 So, we have a very dense, very hard slab. 362 00:22:43,420 --> 00:22:45,900 So, barely can get a finger in it - 363 00:22:45,900 --> 00:22:49,100 but as we get further and further down, it's very sugary snow, 364 00:22:49,100 --> 00:22:51,580 it's easier to put my fingers into it. 365 00:22:51,580 --> 00:22:54,220 Take a nice little sample of this... 366 00:22:54,220 --> 00:22:58,660 ..and so this is what we're looking for, this is our weak layer. 367 00:23:00,780 --> 00:23:02,500 This is a key discovery. 368 00:23:05,060 --> 00:23:08,380 It's only now that we've found the weak layer that we can be sure 369 00:23:08,380 --> 00:23:11,940 that JSP is capable of releasing a major avalanche... 370 00:23:13,100 --> 00:23:17,380 ..and it also gives us another important piece of information. 371 00:23:17,380 --> 00:23:21,340 By sawing along the weak layer, we can make our first estimate 372 00:23:21,340 --> 00:23:23,900 of how large our avalanche could be. 373 00:23:31,780 --> 00:23:35,500 This mini avalanche released about half a cubic metre of snow... 374 00:23:37,500 --> 00:23:39,820 ..and it weighs over 100kg. 375 00:23:42,860 --> 00:23:46,460 If, when we drop our explosives, we can get the same weak layer 376 00:23:46,460 --> 00:23:51,620 to fail right across the top of JSP, we can expect up to 100,000 times 377 00:23:51,620 --> 00:23:54,220 more snow to slide out of this bowl. 378 00:23:56,100 --> 00:23:59,060 That would be up to 10,000 tonnes. 379 00:23:59,060 --> 00:24:00,700 A huge avalanche. 380 00:24:03,260 --> 00:24:06,140 But just as Scott is making his discoveries, 381 00:24:06,140 --> 00:24:10,220 there's an alarming development on the other side of the valley. 382 00:24:10,220 --> 00:24:12,780 Hey, check this out. This is real cool. What just happened? 383 00:24:12,780 --> 00:24:15,820 Well, we're starting to see a change in the start zone at the top. 384 00:24:15,820 --> 00:24:19,820 One of our thermal cameras has picked up unexpected movement 385 00:24:19,820 --> 00:24:21,380 in the snow. 386 00:24:21,380 --> 00:24:24,620 So, you see this V in the scan is a lighter colour? 387 00:24:24,620 --> 00:24:26,660 We've got a little different temperature 388 00:24:26,660 --> 00:24:28,180 than the surrounding snow. 389 00:24:28,180 --> 00:24:29,820 It was all dark blue and purple prior, 390 00:24:29,820 --> 00:24:31,620 and then, just in the last couple of minutes, 391 00:24:31,620 --> 00:24:33,220 things started moving. You see it? 392 00:24:33,220 --> 00:24:35,460 It's moving there, yeah, yeah. Pretty neat, hey? Wow. 393 00:24:35,460 --> 00:24:37,460 But, you see, the tail is growing. 394 00:24:37,460 --> 00:24:41,580 I expect it'll be down by here before we're done seeing it. 395 00:24:41,580 --> 00:24:42,780 Wowee! 396 00:24:50,260 --> 00:24:53,260 So, does this mean that the snowpack is really unstable 397 00:24:53,260 --> 00:24:55,820 and this thing could just go at any time? Yeah. 398 00:24:55,820 --> 00:24:58,340 I wouldn't want to be skiing up there right now. Yeah. No way. 399 00:25:01,420 --> 00:25:03,660 So, this is a little bit nerve-racking. 400 00:25:03,660 --> 00:25:05,300 It seems that that avalanche is ready, 401 00:25:05,300 --> 00:25:06,740 and we are nowhere NEAR ready. 402 00:25:06,740 --> 00:25:08,140 We've got more scanning, 403 00:25:08,140 --> 00:25:10,300 we've got an entire experiment to set up. 404 00:25:10,300 --> 00:25:12,660 So, we need that snow to stay up there 405 00:25:12,660 --> 00:25:14,700 for at least another 24 hours. 406 00:25:19,540 --> 00:25:22,460 It seems we may have even less time than we thought. 407 00:25:24,740 --> 00:25:28,500 The scientists desperately need to collect as much data as they can 408 00:25:28,500 --> 00:25:30,460 before the avalanche comes down. 409 00:25:30,460 --> 00:25:32,060 I think this looks good - 410 00:25:32,060 --> 00:25:34,940 we're just going to head up a little bit, and then we'll set up. 411 00:25:34,940 --> 00:25:38,820 It means it's "skates on" time for Chris Hopkinson and his team. 412 00:25:42,300 --> 00:25:44,700 Can I get the tripod first, please? Yeah. 413 00:25:44,700 --> 00:25:48,700 They have just one day to create a map of the mountainside... 414 00:25:48,700 --> 00:25:50,940 It keeps you fit, doing this! 415 00:25:50,940 --> 00:25:53,540 ..that we can then use to predict the exact route 416 00:25:53,540 --> 00:25:55,700 our avalanche will take. 417 00:25:58,340 --> 00:25:59,660 There we are. 418 00:26:00,940 --> 00:26:03,740 Their key bit of kit is this yellow box, 419 00:26:03,740 --> 00:26:07,820 which contains a range-finding device called a lidar. 420 00:26:07,820 --> 00:26:10,580 Essentially, what we've got here is a three-dimensional camera, 421 00:26:10,580 --> 00:26:12,460 but instead of using passive light from the sun, 422 00:26:12,460 --> 00:26:14,300 it uses its own active light source. 423 00:26:15,620 --> 00:26:17,340 That light source is a laser, 424 00:26:17,340 --> 00:26:19,620 which it bounces off the mountainside. 425 00:26:20,860 --> 00:26:23,820 The data that's reflected back is then used to build up 426 00:26:23,820 --> 00:26:27,420 this detailed three-dimensional map of the avalanche path. 427 00:26:32,140 --> 00:26:35,660 It reveals every ridge and the steepness of each slope 428 00:26:35,660 --> 00:26:38,980 that will affect the path and speed of the avalanche 429 00:26:38,980 --> 00:26:42,860 as it flows down through this gully and into the valley below. 430 00:26:44,060 --> 00:26:47,660 It's information that will be critical when we try to predict 431 00:26:47,660 --> 00:26:50,940 the size, speed and power of that avalanche. 432 00:26:58,620 --> 00:27:01,380 While the team continue to survey the mountain, 433 00:27:01,380 --> 00:27:04,860 it's time for me to move on to the next part of MY mission. 434 00:27:04,860 --> 00:27:08,740 Because our experiment is about more than just the physics 435 00:27:08,740 --> 00:27:10,860 and mechanics of avalanches. 436 00:27:10,860 --> 00:27:13,820 If we want to save lives, we also need to understand 437 00:27:13,820 --> 00:27:16,580 what being caught in an avalanche does to the human body. 438 00:27:22,820 --> 00:27:27,140 Elyse Saugstad is one of the best skiers in the world, 439 00:27:27,140 --> 00:27:28,860 a former freeride world champion... 440 00:27:32,300 --> 00:27:35,780 ..and she knows exactly what it's like to be caught in an avalanche. 441 00:27:37,740 --> 00:27:42,420 In February 2012, she was out with a group of other world-class skiers 442 00:27:42,420 --> 00:27:44,660 on a route called Tunnel Creek, 443 00:27:44,660 --> 00:27:46,820 in Stevens Pass, near Seattle. 444 00:27:55,340 --> 00:27:58,260 What happened that day is a perfect example 445 00:27:58,260 --> 00:28:01,500 of how even the most expert skiers can be caught out 446 00:28:01,500 --> 00:28:03,820 by the hidden risks of avalanches. 447 00:28:07,500 --> 00:28:10,020 I look up to my left, 448 00:28:10,020 --> 00:28:11,780 up into the trees... 449 00:28:12,900 --> 00:28:15,860 ..and I see this plume of smoke coming, 450 00:28:15,860 --> 00:28:18,700 like a plume of snow smoke. 451 00:28:20,060 --> 00:28:23,500 My ski partner, Chris Rudolph, yelled at me, 452 00:28:23,500 --> 00:28:25,620 "Elyse, avalanche! 453 00:28:25,620 --> 00:28:27,540 "Elyse, avalanche!" 454 00:28:30,300 --> 00:28:34,460 And I just got flipped over and over and over. 455 00:28:36,460 --> 00:28:39,860 It's a lot like being on a roller-coaster. 456 00:28:39,860 --> 00:28:42,380 The only difference is, in an avalanche, 457 00:28:42,380 --> 00:28:46,340 you don't know when it's going to end and how it's going to end up. 458 00:28:47,700 --> 00:28:51,060 That's when it struck me, "Oh, my gosh... 459 00:28:51,060 --> 00:28:52,500 "This is how I'm going to die." 460 00:29:00,660 --> 00:29:02,740 In just 45 seconds, 461 00:29:02,740 --> 00:29:05,780 Elyse was hurled over 700 vertical metres 462 00:29:05,780 --> 00:29:07,220 down the mountain. 463 00:29:08,940 --> 00:29:11,900 When the slide finally came to rest, 464 00:29:11,900 --> 00:29:14,860 I was mostly buried. 465 00:29:16,100 --> 00:29:18,780 The only thing that was free 466 00:29:18,780 --> 00:29:23,980 was...my face and airway, 467 00:29:23,980 --> 00:29:25,780 which was the most important thing. 468 00:29:27,020 --> 00:29:31,460 But the snow had solidified around me like cement, 469 00:29:31,460 --> 00:29:36,220 and I was so stuck in place, I couldn't even free my head 470 00:29:36,220 --> 00:29:38,460 and lift it up out of the snow. 471 00:29:40,180 --> 00:29:42,420 Elyse was lucky. 472 00:29:42,420 --> 00:29:44,740 She was rescued within minutes... 473 00:29:44,740 --> 00:29:47,460 ..but three of her friends died that day. 474 00:29:55,260 --> 00:29:59,500 The thought of being caught in an avalanche is truly horrifying, 475 00:29:59,500 --> 00:30:03,580 and it taps into a genuine fear I have of being buried alive - 476 00:30:03,580 --> 00:30:08,060 but what's it like to be interred in the snow, and why is it so deadly? 477 00:30:08,060 --> 00:30:10,460 Well, much against my better judgment, 478 00:30:10,460 --> 00:30:13,300 I've volunteered to take part in an experiment 479 00:30:13,300 --> 00:30:17,420 which is studying how our bodies react to being buried in snow. 480 00:30:19,260 --> 00:30:23,100 I'm going to have over half a tonne of snow piled on top of me 481 00:30:23,100 --> 00:30:27,580 as part of a trial to test some potentially life-saving equipment. 482 00:30:27,580 --> 00:30:31,620 It's being run by wilderness medicine expert Nic Kanaan. 483 00:30:31,620 --> 00:30:33,380 Nic. 484 00:30:33,380 --> 00:30:35,180 Oh, hey! Hi. How you doing? 485 00:30:35,180 --> 00:30:37,660 Good, thank you. Good to meet you. You too. 486 00:30:37,660 --> 00:30:38,940 Thanks for coming out here. 487 00:30:38,940 --> 00:30:40,860 Oh, well, I was going to say you're welcome, 488 00:30:40,860 --> 00:30:42,220 but you're not really! So... 489 00:30:42,220 --> 00:30:43,500 So, this is it, is it? 490 00:30:43,500 --> 00:30:44,660 This is my grave? 491 00:30:44,660 --> 00:30:46,020 Well, it's not really a grave. 492 00:30:46,020 --> 00:30:49,140 Uh, you're supposed to be coming out of here alive. 493 00:30:49,140 --> 00:30:51,900 It's about a metre deep, and then we're going to be stacking 494 00:30:51,900 --> 00:30:53,980 snow even higher from there. 495 00:30:53,980 --> 00:30:55,980 How do I communicate with you when I'm in there? 496 00:30:55,980 --> 00:30:57,540 You're going to have a radio. 497 00:30:57,540 --> 00:30:59,460 So, you can communicate by radio. 498 00:30:59,460 --> 00:31:01,860 Your feet will not be buried, OK? 499 00:31:01,860 --> 00:31:03,580 Your feet are going to be left free. 500 00:31:03,580 --> 00:31:07,300 If at any point you want out, and you're panicking, 501 00:31:07,300 --> 00:31:09,060 you just start kicking your feet. 502 00:31:10,980 --> 00:31:12,940 Which finger would you like that one on? 503 00:31:12,940 --> 00:31:15,660 This one. OK, great. So this is going to go... 504 00:31:16,580 --> 00:31:17,660 ..right here. 505 00:31:18,780 --> 00:31:20,740 The aim of this experiment... 506 00:31:20,740 --> 00:31:22,220 There's nothing nice about this. 507 00:31:22,220 --> 00:31:26,580 ..is to find ways to help avalanche victims survive for longer. 508 00:31:26,580 --> 00:31:29,580 We're going to just put this right here, 509 00:31:29,580 --> 00:31:31,900 and then this goes on the forehead. 510 00:31:31,900 --> 00:31:35,540 So, I'm being fitted with sensors that will monitor my vital signs 511 00:31:35,540 --> 00:31:36,900 while I'm under the snow. 512 00:31:38,580 --> 00:31:41,660 Nic's just put this on my finger. See how much my hand's shaking here? 513 00:31:43,140 --> 00:31:45,580 That's bad, isn't it? 514 00:31:45,580 --> 00:31:47,340 But very reflective of how I feel. 515 00:31:48,940 --> 00:31:51,980 One, two. There you go, and I'm going to lower you down, OK? 516 00:31:51,980 --> 00:31:54,100 One, two, three - coming down. 517 00:31:58,380 --> 00:32:01,140 Over three quarters of the people killed by avalanches 518 00:32:01,140 --> 00:32:02,660 die from suffocation. 519 00:32:03,820 --> 00:32:08,460 So, today, I'm helping test a bit of kit called an Avalung. 520 00:32:08,460 --> 00:32:11,500 It's designed to extract the air from the snowpack. 521 00:32:11,500 --> 00:32:14,300 If it works, it should allow me to breathe under the snow 522 00:32:14,300 --> 00:32:15,620 for up to an hour. 523 00:32:16,660 --> 00:32:17,940 Close your eyes. 524 00:32:17,940 --> 00:32:21,220 You're going to have to do some breathing exercises, and... 525 00:32:21,220 --> 00:32:22,940 ..all that yoga's going to pay off. 526 00:32:22,940 --> 00:32:24,300 OK? 527 00:32:24,300 --> 00:32:25,380 Cardiac... 528 00:32:27,020 --> 00:32:29,620 Actually, I don't think all the yoga in the world 529 00:32:29,620 --> 00:32:31,380 would help me right now. 530 00:32:36,340 --> 00:32:40,140 I feel utterly terrified, but I guess that's... 531 00:32:41,220 --> 00:32:43,380 ..that's the reason we're doing this, cos, you know, 532 00:32:43,380 --> 00:32:46,300 the people caught in an avalanche would feel utterly terrified, 533 00:32:46,300 --> 00:32:48,300 too, so... But I... 534 00:32:48,300 --> 00:32:52,820 Like, my whole body is shaking, and it's not cos I'm cold. 535 00:32:52,820 --> 00:32:56,460 It is truly the most terrifying thing I've ever done, ever. 536 00:32:56,460 --> 00:32:58,420 Or ever wish to do. 537 00:33:17,060 --> 00:33:19,100 I'm only under a metre of snow, 538 00:33:19,100 --> 00:33:21,940 but it really is like being set in concrete. 539 00:33:23,660 --> 00:33:25,300 I can't move. 540 00:33:25,300 --> 00:33:28,340 I can't hear or see anything from the outside world. 541 00:33:30,820 --> 00:33:33,900 OK, can you get on comms and have her wiggle her feet 542 00:33:33,900 --> 00:33:36,260 to indicate that she's OK? 543 00:33:36,260 --> 00:33:39,020 Danielle, wiggle your feet for us. 544 00:33:39,020 --> 00:33:41,900 There we go. Positive - feet. 545 00:33:44,020 --> 00:33:46,460 But already, I'm starting to panic. 546 00:33:49,300 --> 00:33:52,340 Her heart rate has increased to 135. 547 00:33:52,340 --> 00:33:55,580 Her oxygen saturation is dropping a little bit. 548 00:33:55,580 --> 00:33:58,620 She's now at 94% oxygen saturation. 549 00:34:01,140 --> 00:34:04,900 It's soon clear that the survival equipment won't help me 550 00:34:04,900 --> 00:34:08,580 unless I can win my mental battle and remain calm. 551 00:34:12,060 --> 00:34:15,660 After just five minutes under the snow, I lose it completely. 552 00:34:18,420 --> 00:34:22,540 I start hyperventilating and my blood-oxygen level plummets. 553 00:34:22,540 --> 00:34:24,220 So, she's dropping alarmingly... 554 00:34:24,220 --> 00:34:26,500 OK, let's go. Dig her out. 555 00:34:32,300 --> 00:34:33,620 There we go. 556 00:34:34,620 --> 00:34:36,300 There you go. 557 00:34:37,300 --> 00:34:38,420 How you doing? 558 00:34:39,300 --> 00:34:41,220 You OK? Big, deep breath. Yeah. 559 00:34:41,220 --> 00:34:44,020 Big, deep breath. You're doing great. 560 00:34:44,020 --> 00:34:46,420 I'm so sorry. No, you're fine. 561 00:34:46,420 --> 00:34:48,020 You're absolutely fine. 562 00:34:48,020 --> 00:34:50,460 It's just the breathing, I couldn't... There you go. 563 00:34:50,460 --> 00:34:52,740 We got you. We got you. 564 00:34:56,540 --> 00:34:58,580 You're safe. 565 00:34:58,580 --> 00:35:00,300 You're breathing good oxygen. 566 00:35:00,300 --> 00:35:03,140 Your oxygen level is back up to 100, OK? That's good. 567 00:35:03,140 --> 00:35:04,860 OK. 568 00:35:04,860 --> 00:35:07,180 Let's get you out of here, OK? Yeah. 569 00:35:07,180 --> 00:35:08,980 You survived an avalanche. 570 00:35:08,980 --> 00:35:10,580 Up you go! 571 00:35:12,260 --> 00:35:13,740 OK, just stand right there. 572 00:35:19,660 --> 00:35:20,940 That's a truly... 573 00:35:25,060 --> 00:35:26,740 ..frightening experience. 574 00:35:26,740 --> 00:35:29,580 It's just the...the sheer panic 575 00:35:29,580 --> 00:35:31,580 of...of the claustrophobia... 576 00:35:32,660 --> 00:35:35,420 ..and...and the whole not being able to breathe. 577 00:35:35,420 --> 00:35:37,820 Everything else, I just felt absolutely fine, 578 00:35:37,820 --> 00:35:39,340 but it was... I just... 579 00:35:39,340 --> 00:35:41,780 It's the total mental thing. 580 00:35:41,780 --> 00:35:44,860 I couldn't quite control it mentally, 581 00:35:44,860 --> 00:35:47,940 and so I couldn't...I couldn't control my breathing. 582 00:35:47,940 --> 00:35:49,820 Um... 583 00:35:49,820 --> 00:35:51,540 Yeah. 584 00:35:51,540 --> 00:35:55,700 I can't... And that's just a taste of, obviously, what people feel, 585 00:35:55,700 --> 00:35:58,860 you know, when they're...when they're stuck in an avalanche. 586 00:35:58,860 --> 00:36:00,940 It's truly, truly terrifying. 587 00:36:09,780 --> 00:36:12,900 For many people, the Avalung will be a life-saver, 588 00:36:12,900 --> 00:36:16,580 allowing them to breathe for longer under the snow - 589 00:36:16,580 --> 00:36:19,460 but it wouldn't have saved me. 590 00:36:19,460 --> 00:36:23,500 Unable to control the panic, I inevitably would have suffocated. 591 00:36:26,220 --> 00:36:29,500 That's why we need to conduct experiments like ours. 592 00:36:29,500 --> 00:36:32,300 We need to stop people from being caught by avalanches 593 00:36:32,300 --> 00:36:33,340 in the first place. 594 00:36:46,980 --> 00:36:49,860 Back at avalanche base camp, the team have finished 595 00:36:49,860 --> 00:36:51,180 their survey work... 596 00:36:52,700 --> 00:36:54,380 ..and now it's the big moment. 597 00:36:55,460 --> 00:36:58,340 It's time to make our prediction of how the avalanche 598 00:36:58,340 --> 00:37:00,420 will play out tomorrow. 599 00:37:00,420 --> 00:37:03,780 So, Jim McElwaine enters all the data we've collected 600 00:37:03,780 --> 00:37:06,300 into a state-of-the-art computer model, 601 00:37:06,300 --> 00:37:09,660 specially designed to simulate how avalanches behave. 602 00:37:11,060 --> 00:37:15,420 One of the key bits of data for that is a model of the mountain surface, 603 00:37:15,420 --> 00:37:18,420 and that's what we got from Chris's lidar data. 604 00:37:18,420 --> 00:37:21,380 Then Jim adds the details, the depth of the weak layer 605 00:37:21,380 --> 00:37:24,340 and the amount of snow that's lying on top of it. 606 00:37:24,340 --> 00:37:27,420 So, I think there's going to be about 50,000 metre cubed 607 00:37:27,420 --> 00:37:30,580 of snow come down - that's if the whole thing goes. 608 00:37:30,580 --> 00:37:31,980 And we've put all this stuff in, 609 00:37:31,980 --> 00:37:33,500 and then we can run the simulation. 610 00:37:37,980 --> 00:37:42,220 This is the best prediction that current science can make. 611 00:37:42,220 --> 00:37:44,820 It shows the path our avalanche will take 612 00:37:44,820 --> 00:37:47,420 and the distance it will likely travel. 613 00:37:47,420 --> 00:37:52,020 Between 1,000 and 15,000 tonnes of snow will come down the mountain 614 00:37:52,020 --> 00:37:54,380 at speeds of up to 80mph. 615 00:37:56,660 --> 00:37:59,700 The red zones show the areas where the destructive forces 616 00:37:59,700 --> 00:38:01,140 will be the highest... 617 00:38:04,940 --> 00:38:08,500 ..and then, after nearly two minutes, it will slide to a halt 618 00:38:08,500 --> 00:38:11,540 right at the bottom of the valley. 619 00:38:15,820 --> 00:38:19,540 We'll see tomorrow how accurate this prediction is, 620 00:38:19,540 --> 00:38:22,300 but we already know that computer models like this one 621 00:38:22,300 --> 00:38:23,540 are fatally flawed. 622 00:38:24,620 --> 00:38:27,380 Sometimes there are some things they can get very wrong. 623 00:38:27,380 --> 00:38:30,380 So, velocities, they're often two or three times larger in avalanches 624 00:38:30,380 --> 00:38:32,020 than the models would predict. 625 00:38:32,020 --> 00:38:34,620 The destructive forces, they can be ten times bigger - 626 00:38:34,620 --> 00:38:36,940 and these can have horrific consequences. 627 00:38:36,940 --> 00:38:39,860 You can design things that you think are going to stand up, 628 00:38:39,860 --> 00:38:42,300 and they get destroyed, many people get killed. 629 00:38:44,740 --> 00:38:46,460 So, the house was right here, as you can see, 630 00:38:46,460 --> 00:38:48,300 where the foundation is. 631 00:38:48,300 --> 00:38:51,340 And so the front door was there, at the head of those stairs. 632 00:38:53,100 --> 00:38:56,460 In Missoula, when the avalanche flowing off Mount Jumbo 633 00:38:56,460 --> 00:39:00,260 struck Fred Allendorf's house, it completely flattened it. 634 00:39:01,460 --> 00:39:03,900 So, this was the driveway. 635 00:39:03,900 --> 00:39:05,780 My office was right there, 636 00:39:05,780 --> 00:39:08,180 and there was a TV room right there. 637 00:39:10,860 --> 00:39:14,780 This is the fatal flaw in our understanding of avalanches. 638 00:39:14,780 --> 00:39:18,300 None of our current computer models would have predicted 639 00:39:18,300 --> 00:39:21,060 this level of destruction. 640 00:39:21,060 --> 00:39:24,580 So, as my good friend - who lives about a block away - 641 00:39:24,580 --> 00:39:27,940 said, "It schmeared the house across the street." 642 00:39:27,940 --> 00:39:30,620 So, the house was completely demolished, 643 00:39:30,620 --> 00:39:34,180 and it was about 100 metres in that direction, 644 00:39:34,180 --> 00:39:36,820 the house was just schmeared all over the landscape. 645 00:39:37,980 --> 00:39:40,820 And Missoula is not a rare case. 646 00:39:40,820 --> 00:39:43,020 Again and again, around the world, 647 00:39:43,020 --> 00:39:47,140 we see avalanches travelling much faster and doing far more damage 648 00:39:47,140 --> 00:39:49,740 than our models can currently explain. 649 00:39:51,740 --> 00:39:54,740 That's why it's so important that we improve our models... 650 00:39:55,820 --> 00:39:59,580 ..so we can accurately predict where avalanches will strike 651 00:39:59,580 --> 00:40:01,940 and how much damage they will do... 652 00:40:03,620 --> 00:40:06,220 ..but to do that, we must achieve something 653 00:40:06,220 --> 00:40:08,060 that no-one has done before. 654 00:40:08,060 --> 00:40:10,020 We need to find out what's going on 655 00:40:10,020 --> 00:40:11,780 in the heart of the avalanche. 656 00:40:18,940 --> 00:40:21,100 The reason that's so difficult is because, 657 00:40:21,100 --> 00:40:23,220 as they rush down a mountainside, 658 00:40:23,220 --> 00:40:26,340 avalanches throw up a mixture of snow and air... 659 00:40:28,060 --> 00:40:29,620 ..creating powder clouds 660 00:40:29,620 --> 00:40:32,900 that can stretch for hundreds of metres in all directions... 661 00:40:34,460 --> 00:40:36,500 ..and they are impossible to see through. 662 00:40:42,740 --> 00:40:46,780 If we want to find out why avalanches are so destructive, 663 00:40:46,780 --> 00:40:51,260 we need to find out what's going on inside that powder cloud... 664 00:40:56,380 --> 00:40:58,620 ..and that's where our car comes in. 665 00:41:03,620 --> 00:41:06,500 It's going to become a mobile instrument platform 666 00:41:06,500 --> 00:41:10,260 that will let us see inside the avalanche's powder cloud. 667 00:41:13,220 --> 00:41:17,700 Jeff Johnson is a geophysicist from Boise State University in Idaho. 668 00:41:21,380 --> 00:41:25,540 He's a rigging the car with a series of cameras and motion sensors. 669 00:41:27,660 --> 00:41:30,300 It'll then be airlifted onto the mountain 670 00:41:30,300 --> 00:41:32,660 and into the path of the avalanche. 671 00:41:36,820 --> 00:41:40,540 Every year, dangerous avalanches sweep across roads, 672 00:41:40,540 --> 00:41:42,180 swallowing cars whole. 673 00:41:43,460 --> 00:41:47,300 This experiment will give us an unprecedented opportunity 674 00:41:47,300 --> 00:41:51,460 to measure the sorts of forces those vehicles are subject to. 675 00:41:51,460 --> 00:41:54,540 No-one's put a vehicle in the flow path of a snow avalanche 676 00:41:54,540 --> 00:41:56,380 that will be this energetic - 677 00:41:56,380 --> 00:41:57,900 and that's exciting, 678 00:41:57,900 --> 00:42:01,100 because we're going to be able to measure accelerations and forces 679 00:42:01,100 --> 00:42:02,740 that the car is being subjected to 680 00:42:02,740 --> 00:42:05,780 that have not previously been measured. 681 00:42:05,780 --> 00:42:07,780 As it is buffeted down the slope, 682 00:42:07,780 --> 00:42:10,820 it should give us some of the best data ever recorded 683 00:42:10,820 --> 00:42:12,460 from inside an avalanche. 684 00:42:14,060 --> 00:42:16,220 And so that, to me, is very exciting. 685 00:42:16,220 --> 00:42:18,220 We may learn something that we don't know. 686 00:42:19,940 --> 00:42:22,420 But it's not just the car we are going to drop 687 00:42:22,420 --> 00:42:25,300 into the path of the avalanche. 688 00:42:25,300 --> 00:42:27,340 If you get caught in an avalanche, 689 00:42:27,340 --> 00:42:29,020 you are in for a rough ride, 690 00:42:29,020 --> 00:42:32,460 but there are some things we can do to help our survival. 691 00:42:32,460 --> 00:42:37,340 One of them is to wear one of these, an avalanche air bag. 692 00:42:37,340 --> 00:42:40,220 The idea is, if you find yourself caught in an avalanche, 693 00:42:40,220 --> 00:42:41,980 you pull down on this ripcord. 694 00:42:48,260 --> 00:42:50,540 The air bag works in two ways. 695 00:42:50,540 --> 00:42:54,540 First, it acts as a cushion, protecting you from injury 696 00:42:54,540 --> 00:42:56,540 from the power of the snow. 697 00:42:58,260 --> 00:43:01,980 And secondly, it's supposed to take advantage of the way 698 00:43:01,980 --> 00:43:05,940 the different sized chunks of snow in the avalanche behave. 699 00:43:05,940 --> 00:43:10,260 As it churns and rolls, the snow starts to self-organise 700 00:43:10,260 --> 00:43:12,580 so that the smaller particles are on the bottom 701 00:43:12,580 --> 00:43:17,700 and then the much larger snowballs and ice chunks rise to the top. 702 00:43:17,700 --> 00:43:20,260 So the theory is, if you are wearing an air bag, 703 00:43:20,260 --> 00:43:23,900 it makes you bigger, turns you into a larger chunk, 704 00:43:23,900 --> 00:43:26,380 and that should keep you at the top of the avalanche, 705 00:43:26,380 --> 00:43:29,020 and therefore easier to rescue. 706 00:43:29,020 --> 00:43:32,380 To test this, we've got two rescue dummies 707 00:43:32,380 --> 00:43:34,900 about the size and weight of a human, 708 00:43:34,900 --> 00:43:37,700 and we're going to put them in the path of our avalanche. 709 00:43:37,700 --> 00:43:42,180 One of them is wearing an air bag and one of them is not. 710 00:43:43,660 --> 00:43:45,780 In theory, the dummy with the air bag 711 00:43:45,780 --> 00:43:48,380 should stay on the top of the avalanche, 712 00:43:48,380 --> 00:43:52,220 while the other one will be buried deep beneath the snow. 713 00:43:52,220 --> 00:43:56,660 In the morning, we are going to find out if that's true. 714 00:44:05,340 --> 00:44:07,420 Finally, everything is ready. 715 00:44:08,740 --> 00:44:12,980 After two days of surveying and rigging the mountainside, 716 00:44:12,980 --> 00:44:14,820 avalanche day is here... 717 00:44:16,500 --> 00:44:19,420 ..and, at sunrise, the whole team gathers. 718 00:44:20,420 --> 00:44:22,740 Morning, everybody, welcome to day three. 719 00:44:22,740 --> 00:44:24,580 Exciting day. 720 00:44:24,580 --> 00:44:27,020 The big sort of theme of it is to remain calm. 721 00:44:27,020 --> 00:44:29,500 Everybody is going to get excited and amped up. 722 00:44:29,500 --> 00:44:31,700 In the end, we need to make proper calls on safety 723 00:44:31,700 --> 00:44:33,260 before anything else happens. 724 00:44:33,260 --> 00:44:35,540 We do the mission, land, regroup 725 00:44:35,540 --> 00:44:38,580 and then see what we have to do to recover. 726 00:44:38,580 --> 00:44:41,620 Calm and slow, measured is the order of the day. 727 00:44:41,620 --> 00:44:43,820 Any other questions, guys? 728 00:44:43,820 --> 00:44:46,380 Awesome. Thanks, gang. Have a good time. 729 00:44:50,380 --> 00:44:53,020 As the final countdown gets under way, 730 00:44:53,020 --> 00:44:56,740 the first thing we need to do is to get the car into place. 731 00:44:58,580 --> 00:45:02,340 So we've got an hour to go, and, for me, this is hugely exciting. 732 00:45:02,340 --> 00:45:04,700 It's amazing to contemplate that this car, 733 00:45:04,700 --> 00:45:06,340 in little more than an hour, 734 00:45:06,340 --> 00:45:08,500 is going to be consumed by an avalanche 735 00:45:08,500 --> 00:45:10,180 that comes down the slope. 736 00:45:14,980 --> 00:45:18,140 It's not something you see every day, is it? 737 00:45:18,140 --> 00:45:21,060 It needs to be lowered with great care. 738 00:45:21,060 --> 00:45:24,980 There are already tracks caused by the snow rolling down the slope... 739 00:45:26,980 --> 00:45:29,500 ..and if the car is dropped too violently, 740 00:45:29,500 --> 00:45:32,180 it could set off the avalanche much too early. 741 00:45:36,180 --> 00:45:38,700 You can really see the different bits of the mountain 742 00:45:38,700 --> 00:45:40,020 where it's exposed. 743 00:45:41,980 --> 00:45:45,780 Meanwhile, the scientists gather at the bottom of the slope 744 00:45:45,780 --> 00:45:48,900 to make last-minute checks on their equipment. 745 00:45:48,900 --> 00:45:50,220 Yeah, I'm pretty nervous. 746 00:45:50,220 --> 00:45:52,180 I've got all sorts of bits of kit going on. 747 00:45:54,260 --> 00:45:56,820 Really got to hope I've got it right, 748 00:45:56,820 --> 00:45:58,980 didn't make too many mistakes. 749 00:46:00,460 --> 00:46:02,740 All right, well, here come the dummies. 750 00:46:07,540 --> 00:46:11,300 The next job for Jason, the mountain safety expert, 751 00:46:11,300 --> 00:46:15,740 is to prepare the explosive charges that'll trigger the avalanche. 752 00:46:15,740 --> 00:46:18,620 Only qualified personnel are allowed in here, 753 00:46:18,620 --> 00:46:21,380 so at this point we need to say goodbye for a few minutes 754 00:46:21,380 --> 00:46:24,420 and we'll see you again soon. 755 00:46:24,420 --> 00:46:28,020 It's like perfect conditions for the avalanche. 756 00:46:28,020 --> 00:46:30,340 You know, the sun's been on this all morning, 757 00:46:30,340 --> 00:46:32,500 so it's absolutely ready to go. 758 00:46:33,500 --> 00:46:35,780 So we're nearly there. It's very exciting. 759 00:46:42,180 --> 00:46:43,940 Good luck, boys. 760 00:46:43,940 --> 00:46:45,340 Thanks. 761 00:46:47,780 --> 00:46:50,860 With just six minutes to go, the helicopter takes off 762 00:46:50,860 --> 00:46:52,540 for the final time. 763 00:47:01,580 --> 00:47:04,420 RADIO CHATTER 764 00:47:04,420 --> 00:47:07,740 Jason has to work out precisely where to deploy the explosives 765 00:47:07,740 --> 00:47:09,900 for maximum impact. 766 00:47:15,500 --> 00:47:19,340 He needs to create a shock wave powerful enough to fracture 767 00:47:19,340 --> 00:47:22,780 that weak layer buried a metre under the surface. 768 00:47:22,780 --> 00:47:25,340 I'm confident Jason is going to trigger us an avalanche. 769 00:47:25,340 --> 00:47:27,140 I think he knows what he's doing. 770 00:47:27,140 --> 00:47:28,820 And he's got a big bomb! 771 00:47:35,300 --> 00:47:38,700 Yeah, that's no problem. We're going over to get in position here now. 772 00:47:39,700 --> 00:47:43,100 Then it's a case of lighting the blue touchpaper. 773 00:47:43,100 --> 00:47:45,620 OK, here we go. 774 00:47:55,740 --> 00:47:57,140 Whoo! 775 00:48:04,500 --> 00:48:07,020 At first, not much happens. 776 00:48:07,020 --> 00:48:09,820 It's not clear if the weak layer has fractured... 777 00:48:09,820 --> 00:48:12,060 Come on... 778 00:48:12,060 --> 00:48:15,260 ..but then the surface snow starts to slide. 779 00:48:16,380 --> 00:48:18,380 It's coming now, though, look at that. Yeah. 780 00:48:34,820 --> 00:48:36,380 Wow, look at that. 781 00:48:38,220 --> 00:48:43,380 All the time, it is picking up speed, and more and more snow. 782 00:48:43,380 --> 00:48:44,860 Oh, yes. 783 00:48:44,860 --> 00:48:46,420 Look how fast it's going! Yeah. 784 00:48:46,420 --> 00:48:48,660 It's certainly an avalanche you wouldn't want to be in. 785 00:48:48,660 --> 00:48:50,580 If you went over those cliffs, you'd be in a mess. 786 00:49:12,380 --> 00:49:15,340 It's an amazing spectacle - 787 00:49:15,340 --> 00:49:18,580 but was this the avalanche our model predicted? 788 00:49:19,860 --> 00:49:22,780 We can immediately see it made at least one error. 789 00:49:24,620 --> 00:49:27,500 The avalanche didn't reach the valley floor, 790 00:49:27,500 --> 00:49:30,140 stopping several hundred metres short of our prediction. 791 00:49:31,740 --> 00:49:33,780 But just how big and powerful was it? 792 00:49:39,500 --> 00:49:42,100 To find out, we have to go up to the slope 793 00:49:42,100 --> 00:49:45,060 to see the damage the avalanche has caused. 794 00:49:46,660 --> 00:49:50,260 This is the most hazardous part of the entire operation. 795 00:49:51,900 --> 00:49:54,580 There's always the chance of a secondary avalanche 796 00:49:54,580 --> 00:49:56,060 coming down the mountain. 797 00:49:57,180 --> 00:49:59,580 We're going to have somebody acting as avalanche guard 798 00:49:59,580 --> 00:50:01,020 the whole time we're here. 799 00:50:01,020 --> 00:50:02,860 If anybody yells avalanche, 800 00:50:02,860 --> 00:50:06,220 we run HARD towards that treed rib. 801 00:50:06,220 --> 00:50:07,300 HARD. 802 00:50:08,900 --> 00:50:11,780 The first thing we find are the two dummies. 803 00:50:11,780 --> 00:50:14,180 They'd got tangled up and been carried 804 00:50:14,180 --> 00:50:15,940 down the slope together. 805 00:50:17,220 --> 00:50:20,460 But they were sitting safely on the surface, 806 00:50:20,460 --> 00:50:22,580 suggesting the air bag had done its job 807 00:50:22,580 --> 00:50:24,660 and prevented them from being buried. 808 00:50:28,220 --> 00:50:31,820 The next job is to assess how big the avalanche was. 809 00:50:31,820 --> 00:50:35,900 To do that, the lidar team perform another scan. 810 00:50:35,900 --> 00:50:38,620 OK. Looks good so far. 811 00:50:38,620 --> 00:50:41,300 By comparing it to the one before the avalanche, 812 00:50:41,300 --> 00:50:45,740 they can work out exactly how much snow flowed down the mountain. 813 00:50:47,380 --> 00:50:52,500 And so we've got 3,647 cubic metres of loss. 814 00:50:52,500 --> 00:50:55,740 That would give us about 1,300 tonnes 815 00:50:55,740 --> 00:50:57,940 of material, snowpack. 816 00:50:59,620 --> 00:51:04,460 1,300 tonnes is the equivalent of four fully loaded jumbo jets. 817 00:51:05,540 --> 00:51:07,700 But our instruments captured far more 818 00:51:07,700 --> 00:51:09,580 than the size of the avalanche. 819 00:51:12,940 --> 00:51:16,500 These images were taken by our thermal cameras, 820 00:51:16,500 --> 00:51:20,500 and they reveal details that no-one has ever seen before. 821 00:51:25,100 --> 00:51:29,180 When the avalanche starts, it's made up of cold surface snow, 822 00:51:29,180 --> 00:51:31,100 shown in green - 823 00:51:31,100 --> 00:51:34,780 but as it flows, it changes, becoming warmer and more turquoise. 824 00:51:40,780 --> 00:51:44,580 Back at Durham University, the challenge for Jim McElwaine 825 00:51:44,580 --> 00:51:46,940 is to explain what this reveals 826 00:51:46,940 --> 00:51:49,940 about the avalanche's inner workings. 827 00:51:49,940 --> 00:51:53,180 This is radically changing our understanding 828 00:51:53,180 --> 00:51:55,180 of how avalanches behave. 829 00:51:55,180 --> 00:51:58,340 Our old model was that the snow would start off at the top 830 00:51:58,340 --> 00:52:00,980 of the mountain, it would maybe pick up some snow as it moved down, 831 00:52:00,980 --> 00:52:03,660 and then it would deposit it at the bottom. 832 00:52:03,660 --> 00:52:06,060 But what this data shows us is that the snow that starts 833 00:52:06,060 --> 00:52:08,820 at the top probably stops partway down, 834 00:52:08,820 --> 00:52:11,380 and the snow that ends up at the bottom probably started 835 00:52:11,380 --> 00:52:12,700 from somewhere in the middle. 836 00:52:14,580 --> 00:52:17,580 This is very important, because the temperature of the snow 837 00:52:17,580 --> 00:52:19,060 affects how it flows. 838 00:52:21,780 --> 00:52:24,900 This discovery, that the snow at the top of the avalanche 839 00:52:24,900 --> 00:52:27,020 isn't the snow that reaches the bottom, 840 00:52:27,020 --> 00:52:28,860 could have major implications 841 00:52:28,860 --> 00:52:33,060 for our understanding of how far and fast avalanches travel. 842 00:52:33,060 --> 00:52:35,820 It's already helped answer one question. 843 00:52:35,820 --> 00:52:37,420 Whoo! 844 00:52:39,260 --> 00:52:42,980 It might partially explain why our avalanche didn't flow 845 00:52:42,980 --> 00:52:44,820 as far as the models predicted. 846 00:52:47,700 --> 00:52:51,260 Because the snow that reached the bottom was warmer than expected, 847 00:52:51,260 --> 00:52:54,060 it was also slushier and stickier. 848 00:52:54,060 --> 00:52:57,180 And that stickiness contributed to our avalanche stopping 849 00:52:57,180 --> 00:52:59,900 much higher up the slope than the model predicted. 850 00:53:02,180 --> 00:53:05,900 This new knowledge will improve our ability to predict which areas 851 00:53:05,900 --> 00:53:07,980 are under threat from avalanches... 852 00:53:12,460 --> 00:53:15,060 ..but what about the really big question? 853 00:53:15,060 --> 00:53:18,860 Why are avalanches so much more devastating than they can predict? 854 00:53:19,940 --> 00:53:23,700 And have we discovered the secret of that vast destructive power? 855 00:53:24,820 --> 00:53:27,860 To answer that, we have to see what our avalanche 856 00:53:27,860 --> 00:53:29,060 has done to the car. 857 00:53:38,940 --> 00:53:40,260 Wow. 858 00:53:42,940 --> 00:53:47,020 It's about 50m below where I think it was set down. 859 00:53:47,020 --> 00:53:50,780 And so... Obviously, it's tilted. It was hit with a lot of force. 860 00:53:50,780 --> 00:53:54,420 The good thing is we have these loggers. 861 00:53:54,420 --> 00:53:57,420 The GPS in here will allow us to figure out how much this has slid. 862 00:54:01,020 --> 00:54:04,060 The car has clearly been seriously damaged. 863 00:54:04,060 --> 00:54:05,460 To see what it went through, 864 00:54:05,460 --> 00:54:07,780 we have to look at the footage from its cameras. 865 00:54:11,780 --> 00:54:14,340 The avalanche starts with a warning of what's to come. 866 00:54:17,060 --> 00:54:20,420 A few large snowballs bouncing down the slope... 867 00:54:22,060 --> 00:54:24,580 ..followed by a surging river of snow, 868 00:54:24,580 --> 00:54:27,580 pouring through the gully at around 50mph. 869 00:54:43,460 --> 00:54:47,060 The initial figures from the motion sensors show the avalanche struck 870 00:54:47,060 --> 00:54:50,660 the car with a force of 30,000 newtons, 871 00:54:50,660 --> 00:54:54,260 nearly ten times that needed to break human bone. 872 00:54:54,260 --> 00:54:57,140 Overall, it was nearly four times more powerful 873 00:54:57,140 --> 00:54:59,860 than the computer models would have predicted 874 00:54:59,860 --> 00:55:01,580 for an avalanche this size... 875 00:55:02,660 --> 00:55:06,460 ..but can we now explain what generated this extraordinary power? 876 00:55:16,260 --> 00:55:18,140 What current models would suggest 877 00:55:18,140 --> 00:55:19,980 is that the avalanche will hit the car 878 00:55:19,980 --> 00:55:21,780 and it will accelerate smoothly, 879 00:55:21,780 --> 00:55:25,020 move for a bit, and then come to a stop. 880 00:55:25,020 --> 00:55:27,620 But when we look at the acceleration data, 881 00:55:27,620 --> 00:55:30,700 we can see that what actually happened was very different. 882 00:55:32,340 --> 00:55:34,900 What I'm seeing here is there's one big surge... 883 00:55:37,940 --> 00:55:39,180 ..the car starts moving - 884 00:55:39,180 --> 00:55:40,660 but then, very surprisingly, 885 00:55:40,660 --> 00:55:42,820 the car gets hit by a second surge, 886 00:55:42,820 --> 00:55:44,340 and then a third surge. 887 00:55:48,820 --> 00:55:52,100 I believe that these surges are most likely why avalanches 888 00:55:52,100 --> 00:55:55,420 have a much greater destructive effect than we would expect. 889 00:55:57,620 --> 00:55:59,660 Until now, our models have assumed 890 00:55:59,660 --> 00:56:02,060 that the snow at the heart of an avalanche 891 00:56:02,060 --> 00:56:04,260 moves like a smoothly flowing river... 892 00:56:05,980 --> 00:56:09,540 ..but Jim's theory is that this river is not smooth at all. 893 00:56:09,540 --> 00:56:13,100 That the surges and acceleration are caused by huge waves 894 00:56:13,100 --> 00:56:15,140 in the avalanche. 895 00:56:15,140 --> 00:56:16,860 Like waves on the ocean, 896 00:56:16,860 --> 00:56:19,420 they tower above the rest of the flow 897 00:56:19,420 --> 00:56:22,780 and move much faster and with much greater force. 898 00:56:27,940 --> 00:56:30,260 He believes it was three of these waves 899 00:56:30,260 --> 00:56:31,860 that smashed into our car, 900 00:56:31,860 --> 00:56:33,580 and that they are the source 901 00:56:33,580 --> 00:56:35,980 of the avalanche's unexpected power. 902 00:56:40,660 --> 00:56:43,500 It's potentially a massive breakthrough. 903 00:56:44,540 --> 00:56:46,620 For the first time, we have this direct data 904 00:56:46,620 --> 00:56:48,460 from inside the avalanche - 905 00:56:48,460 --> 00:56:51,980 and this is going to be invaluable for improving our models. 906 00:56:51,980 --> 00:56:55,580 So if we can build these truly predictive models, 907 00:56:55,580 --> 00:56:57,180 then we can really save lives 908 00:56:57,180 --> 00:56:58,980 because we can apply them in areas 909 00:56:58,980 --> 00:57:01,020 where we don't have historical records, 910 00:57:01,020 --> 00:57:03,540 we can apply them if the climate is changing, 911 00:57:03,540 --> 00:57:06,220 and we will know how to design infrastructure 912 00:57:06,220 --> 00:57:09,300 so it can withstand the massive forces that avalanches can generate. 913 00:57:23,980 --> 00:57:27,820 The implications of this experiment could be huge. 914 00:57:28,860 --> 00:57:33,420 For the first time, we are beginning to understand how avalanches move 915 00:57:33,420 --> 00:57:35,740 and why they are so destructive. 916 00:57:36,860 --> 00:57:40,100 It could lead us to a fundamental rethink 917 00:57:40,100 --> 00:57:42,860 in how we assess avalanche risk. 918 00:57:42,860 --> 00:57:46,180 We may find that villages and towns we thought were safe 919 00:57:46,180 --> 00:57:48,940 are actually in danger... 920 00:57:48,940 --> 00:57:50,860 ..but armed with that knowledge, 921 00:57:50,860 --> 00:57:53,300 we can now reinforce their defences 922 00:57:53,300 --> 00:57:56,220 to protect them against future calamities. 923 00:57:58,060 --> 00:58:02,060 It may be that these three days in the Canadian Rockies 924 00:58:02,060 --> 00:58:06,380 will one day prove a milestone in advancing avalanche science. 925 00:58:09,220 --> 00:58:12,860 I think this has been really important. 926 00:58:12,860 --> 00:58:15,620 For the first time, we've used portable technology 927 00:58:15,620 --> 00:58:17,580 to look deep inside an avalanche, 928 00:58:17,580 --> 00:58:19,860 and we're just beginning to understand 929 00:58:19,860 --> 00:58:22,900 how these devastating natural phenomena operate. 930 00:58:22,900 --> 00:58:24,980 Now, we are still at the early stages, 931 00:58:24,980 --> 00:58:26,420 we've got a long way to go - 932 00:58:26,420 --> 00:58:28,940 but if we can use this understanding 933 00:58:28,940 --> 00:58:30,820 to improve those models, 934 00:58:30,820 --> 00:58:34,740 then perhaps we can prevent tragedies in the future, 935 00:58:34,740 --> 00:58:37,780 potentially saving thousands of lives.