- 5/30/2025
Viewers see what it's like to be overwhelmed by a sudden onslaught of "white death"—an avalanche. Avalanches are an escalating peril as skiers and snowmobilers push the limits into the back country. NOVA witnesses scientists getting buried alive in their attempts to understand these forces of nature.
Category
📺
TVTranscript
00:01Tonight on NOVA
00:03It was saving the house.
00:05The roof was just turned off.
00:07It strikes without warning and wipes out everything in its path.
00:11Now, scientists take you inside an avalanche
00:15to unlock its deadly secrets.
00:18Jay and I cannot move. We are buried inside the house.
00:22It's a battle to understand and control
00:27The Avalanche
00:51Major funding for NOVA is provided by
00:54The Park Foundation
00:56dedicated to education and quality television.
01:00And by
01:02The Corporation for Public Broadcasting
01:04and viewers like you.
01:19Off the coast of Iceland
01:21The rescue team races to a village in the grip of disaster.
01:29They arrive to find a site of utter devastation.
01:31The town of Flattery lies in frigid ruin
01:41under hundreds of tons of mountain snow.
01:45A score of residents are feared lost.
01:49Workers scrambled to find the living and the dead.
01:53The victims of a sudden and massive avalanche.
02:03I woke up to these terrible loud noises.
02:11The earth was shaking.
02:13It was shaking the house.
02:17The roof was just turned off.
02:19The wall hit my head.
02:21Then the snow came.
02:23The bed had moved into the next room.
02:27I was crushed in between the walls and the roof.
02:31Completely stuck in the snow.
02:33When I came out everything seemed very strange.
02:45And you couldn't hear nothing else but the wind.
02:49The wind and you could hear people crying.
02:57Where houses had not been before.
02:59It was only snow and dark spots.
03:01The avalanche took a big part of Flattery.
03:13Just took it away in a few seconds.
03:17It was just gone.
03:27The avalanche.
03:31An event that is as extraordinary as it is horrifying.
03:35Over a million tumble down the mountains of the world each year.
03:41They range from harmless showers of snow.
03:43To hurricane blasts that can strike with the force of 200 pounds of TNT.
03:51And some do.
03:55In its wake, age-old questions arise.
03:59How can simple snow become so destructive?
04:03Can the avalanche be controlled?
04:07It is these questions that awaken avalanche specialists around the world each winter season.
04:17And press scientists to extremes in pursuit of answers.
04:23All for what seems a fairly simple act of gravity.
04:27Inwards of our world.
04:28Inwards of our world.
04:29The Ev向ies of the World.
04:30The Ev向ies of the World.
04:31The Ev向ies of the World.
04:32The Ev向ies of the World.
04:33The Ev向ies of the World.
04:34Nowhere has the surge been pursued longer than in Switzerland.
04:35Nowhere has the search been pursued longer than in Switzerland.
04:50In the shadow of the soaring Alps reinforced walls on homes.
05:04Churches, slopes covered with protective barriers and sheltered roadways tell of a people under siege.
05:17For centuries a war has raged with the avalanche. One that has killed more people here than any other natural disaster.
05:28In that time the Swiss have come to know their enemy. An elaborately complex phenomena whose basic ingredients remain simple. That of snow and a slope.
05:50An avalanche is just snow gliding down a slope.
05:57The only force acting on the snow cover is gravity. So an avalanche will start because of its weight.
06:05Understanding these elements and how they are triggered to produce an avalanche is the job of Dr. Atmar Busser of the Institute for Snow and Avalanche Research in Davos, Switzerland.
06:26All around here are the mountains. They are all covered by snow. Some avalanches go. Some slopes don't go. The question is why do they not go? The answer to this question is within the snow cover.
06:51Whether an avalanche begins or not depends on the snow's ability to stay together and resist the force of gravity pulling it down the hill.
07:03In a laboratory scientists can measure the strength of the snow.
07:16I have here a sample of snow. I know how heavy it is and what I wonder about is how strong it is.
07:26Here, Dr. Busser uses centrifugal force to imitate the effects of gravity.
07:33Now, it's broken with a few hundred tons in a second and from that speed we can calculate the strength of the snow sample.
07:57We are interested in the strength of the snow sample because once it breaks we have an avalanche out in the field.
08:06But in the quest to predict when snow might break, scientists have to contend with one of nature's tiniest and most capricious wonders.
08:21Ice crystals.
08:30Infinite in variety, ice crystals give snow its stability. Yet they themselves are notoriously unstable.
08:40As frozen water vapor, ice crystals undergo continuous change with variations in temperature and humidity.
08:49How they become so individual is by way of an odyssey that begins when a water molecule freezes around a dust particle high above the earth.
09:01Then, out of the sky it falls, growing and shrinking as it drifts, picking up water molecules and ice crystals as it goes.
09:14A snowflake is a group of crystals and the shape each crystal takes determines its crucial ability to bond within the snow cover.
09:24Small, rounded crystals pack tightly to create dense slabs of snow. Large and angular crystals tend to form loose, weak layers.
09:43How well these layers bond to each other is critical.
09:50If the bonds are weak, the seeds of an avalanche may be planted.
10:07Even an expert skiing the champagne powder of Montana
10:11cannot tell what dangers lie beneath the surface.
10:22Carl Berkland is an avalanche forecaster for the Gallatin National Forest.
10:28He and his partner Ron Johnson go out daily to evaluate the latest snow conditions.
10:34Just like no two snowflakes are alike, no two snowstorms are exactly alike either.
10:40We are going to have storms that are warmer where we will put down denser snow, colder storms where the snow is all fluffy.
10:48And then we will have some storms that are really windy and then the snow packs in tighter and you get a denser layer.
10:54So we are going to end up with these different layers in the snow pack.
11:00To get a look at the stability of these layers, forecasters dig a pit into the slope.
11:06By exposing a cross section of the snow pack, they have a window on the history of the winter so far.
11:16Looks like this is that wind slab from yesterday's wind event.
11:19Just that downhill wind, huh?
11:20Yeah, and all the soft things.
11:22Snows from the storm that came in last weekend.
11:27The story that unfolds reveals individual storms and even past changes in weather conditions.
11:32This is that big wind event from 10 days, 14 days ago.
11:36The strength of the layer is reflected in the light passing through a thin column.
11:43The darker layer is denser and more tightly bonded than the lighter snow on top.
11:48And so this is the darker snow right here and then this stuff up in here is a lot less dense so the light's coming through it.
11:56How these layers stack up determines the avalanche danger.
12:02An avalanche hazard begins to build when a weak layer forms on a slope.
12:08One classic type may consist of frozen dew.
12:11Known as surface horror, these loose crystals are not in themselves dangerous.
12:19But if another layer is deposited on top with the help of the wind or a dense snowfall, a heavy slab can build up.
12:27When the force above becomes too much to bear, the result is an avalanche.
12:33This is the weak layer, a little slab on top when we load this thing up.
12:42Boy, it's going to rock and roll.
12:44For now, only a thin slab layer is on top.
12:48But the season is far from over.
12:51Carl and Ron will be closely watching the snows to come.
12:54But often, the discovery of avalanche-prone slopes is by accident.
13:02All that's required is the addition of what in effect is the straw that breaks the camel's back.
13:09Yesterday, we were up skiing, and right away we knew it was a dangerous day due to wind.
13:22It just makes for really weird snow.
13:26For 15 years, Chris Stone has taken on the backcountry of Montana.
13:30Like hundreds of other skiers each year, he has found himself an unwitting participant in the creation of an avalanche.
13:40We're out there a lot. We have a feel for the conditions. We felt pretty safe.
13:45My partner went down first, cautiously watched me go by.
13:52I got out of sight from him, and I got caught in an avalanche.
13:57In accidents like this one, even the most experienced skiers find they're no match for an avalanche.
14:09It was up to speed so fast.
14:12There was no hope for any getting out of it.
14:16It took me and slammed me down.
14:18The role Chris played in the avalanche was that of a trigger.
14:31By applying the final increment of pressure, avalanche triggers cause buried weak layers to fail, releasing all the snow above.
14:40Most avalanches are triggered by rapid heavy snowfall.
14:50But most avalanche accidents are caused by people.
14:55Whether trigger or victim, with ignorance or arrogance, they can transform a natural act into a natural disaster.
15:07Avalanches don't happen by accident. They happen for particular reasons.
15:18It's the interaction of terrain and snowpack and weather that make it possible to have an avalanche.
15:23But there's no avalanche hazard until you introduce people.
15:27It's the human factor.
15:30And really, it does come down to attitude.
15:43We're going to accept a different level of risk if we want to just go out snowboarding for the day and come back and live for another day.
15:53We're going to have a different level of acceptable risk if we want to climb this mountain no matter what.
16:03If you have a ski to die or a snowboard to die or I'm going to live here no matter what, probably sooner or later you will die in avalanche.
16:11I've dug out many, many bodies. I've been to lots of accident sites. They just didn't understand the risk they were taking.
16:22In mountains like these, the risk comes with the territory.
16:28Avalanches kill hundreds of people every year.
16:39Most avalanches occur on slopes between 30 and 45 degrees.
16:45About the range of the most challenging runs at ski resorts like Bridger Bowl in Montana.
16:50Over 30 storms drop more than 25 feet of snow per winter here.
17:01With just the right slope angle and more than enough potential triggers,
17:08After the storm, Bridger Bowl should be a scene of slaughter.
17:15But it's not.
17:19Here the avalanche risk is vigorously controlled.
17:24Each morning, well before the skiers arrive, the ski patrol gets ready to open the slopes.
17:29Things got skied heavily yesterday. We did get the ridge open and it got hammered.
17:35Led by Faye Johnson, these control specialists are preparing to trigger avalanches intentionally before skiers can later by accident.
17:44The north and south rope lines on Bridger need some attention, just the usual things.
17:49So we might as well head on up.
17:50At 9 a.m. the lifts will open.
17:58They have less than three hours to tame the mountain.
18:11They first use a technique called ski cutting.
18:14They try to dislodge unstable snow by traversing the slope slowly.
18:20But at an angle to give them an escape route should they trigger an avalanche.
18:25This is my rock. When I come around, I'll be out of here.
18:2910-4, go ahead.
18:31Thank you, Martin.
18:33For other slopes, they turn to a different method.
18:35Ready to fire.
18:36A 75-millimeter recoilless rifle pounds the highest and most distant slopes of Bridger Bowl.
18:45Through the veil of a winter storm, each 10-pound shell wallops a snowpack one mile away.
18:53Ready to load.
18:54Loading.
18:59Locked and loaded.
19:01On target.
19:07Ready to fire.
19:08Clear to the front.
19:09Clear to the rear.
19:10Ready to fire.
19:11Fire.
19:23In just minutes, the gun can clear several slopes.
19:26A job that would take the ski patrol hours to accomplish on foot.
19:36Wind-packed cornices are attacked with poles and shovels.
19:40If resistant, they're hit with an explosive punch.
19:44More than 1,000 explosive charges are set off at Bridger Bowl every year.
20:01Is it armed now?
20:02It's not gonna blow up yet.
20:03I've just put the fuse in there.
20:09The fuse gives them 90 seconds to place the bomb.
20:12For maximum effect, the charge is suspended above the snowpack, where its shockwave can do more damage.
20:32In just two hours, the ski patrol has made Bridger Bowl safe for another day.
20:37But that's only one square mile up the Bridger Range.
20:43Outside the resort lays the vast backcountry.
20:48Thousands of miles of untended, uncontrolled slopes.
20:52Skiers are coming here in ever greater numbers, raising the stakes for forecaster Carl Burkland.
21:03Over the past six years, we probably have about three times as many backcountry skiers as we ever did before.
21:10And if you get more people into the backcountry, you have more avalanche triggers and increasing death tolls.
21:15The most important things for me to do as an avalanche specialist is to get out in the field.
21:23I want to get out there, I want to walk on the snowpack, dig snow pits, do stability evaluations.
21:30I think that's all we're going to get for a break here, Ron.
21:34They combine field observations with the latest weather information.
21:37Yeah, maybe based on the models in this satellite loop.
21:40Yeah, might just give us a little bit of a shot of moisture tomorrow.
21:44You kind of see it dropping in as this axis is off the west coast in the northwest part of Montana.
21:49This forms the basis for their daily avalanche advisory.
21:53Good morning, this is Carl Burkland with an avalanche advisory.
21:56I would call the avalanche danger mostly moderate to high on slopes steeper than 40 degrees
22:02and moderate on gentler slopes in the Bridger, Gallatin, Madison and Washburn ranges, the Lionhead area and the mountains around.
22:08But it's up to the individual to heed this warning.
22:12We hope to give people the tools to make better decisions in the backcountry,
22:17which will hopefully save lives.
22:21I mean, people are going out to the really radical lines as soon as they can.
22:27They're really pushing the boundaries.
22:36Typical are the snowmobilers.
22:39Thousands invade the national forests of Montana each year.
22:48With a 130 horsepower engine weighing a quarter of a ton and exceeding speeds of 85 miles per hour,
22:56the snowmobile makes an impressive toy.
22:59Usually there's about 10 of us go out riding.
23:02Our idea is just go out and have a good time and try not to break anything.
23:05Here, the thrill of open throttle in open country is so powerful, warnings often fall by the wayside.
23:18High marking is a favorite activity.
23:21But for two snowmobilers, it became a game of Russian roulette.
23:25We were climbing up the hill over here.
23:28Jim had went up at first and made a high mark on it.
23:31High markings where you go up the hill, pretty steep hill, as far as you can.
23:36And you either start to get stuck because it gets too steep and deep, or the snowmobile starts to lose power.
23:42Then you turn around right before you get stuck.
23:43We've had several avalanches come down on us before, but usually, you know, you're heading downhill when it's happened and you just kind of ride it out and it's been fine.
23:55But, you know, it didn't feel like, you know, we were ever doing anything really ridiculous.
23:59Jim went up the hill first and I waited until he got back down and then I went up.
24:10As soon as he made his corner up on top of the hill, it broke off up above him.
24:21I could see the suit tumbling in the snow, carried a sled into the trees, and then he disappeared.
24:27I kind of remember swimming for a minute and then I can remember just thinking to relax.
24:37The avalanche buried John under three feet of snow.
24:41A similar accident caught on videotape shows how survival depends on immediate rescue.
24:48John nearly suffocated.
24:51When he was found, he wasn't breathing and had no pulse.
24:55If it wouldn't have been for the people that were with me, I'm sure I wouldn't be here.
25:04You read about it in the papers, but you figured it'd never happen to me.
25:07A lot of people think that avalanches can't happen to them, but it's the same thing as someone who builds a home in a floodplain saying that they don't think that a flood will ever hit their house.
25:23If people go out and play on steep, snow-covered terrain, in other words, play in avalanche terrain, then there's always the potential for them to trigger an avalanche.
25:33The day after the snowmobile accident, Carl comes to investigate the site.
25:40Carl, nice to see you again.
25:41Yeah, thanks for calling me.
25:43You ready to take a ride?
25:44Yeah.
25:45He joins forest ranger Jonathan Klein.
25:47Sounds like a pretty interesting story.
25:53In making the journey here, Carl hopes to piece together how the snowpack failed.
25:59He ended up separated from his sled.
26:03Yeah, his sled was upslope of him, 30, 40 yards.
26:09Okay.
26:11Carl treats this frozen landscape like the scene of a crime.
26:16That must be where he was.
26:18If you imagine, you know, the snow coming right over the top here, imagine your head being...
26:25Avalanche debris is typically rock solid.
26:27See how hard that stuff is.
26:29It's just set up like concrete, you know?
26:31It's a rock.
26:32Warmed by the friction of the fall, the air forced out of it.
26:37The dense snow quickly refreezes after it comes to rest.
26:42Makes for a good stairway, though, doesn't it?
26:44Yeah, it sure does.
26:45You can sure walk on this stuff easily.
26:48They head for the crown, the wall created when the avalanche broke away.
26:53I'll shoot the slope when we get up here a bit.
26:55Right, this about looks like the steepest part.
26:59Take one more shot of the slope angle.
27:01Okay.
27:03This slide is classic, you know?
27:04They check the slope angle using an inclinometer.
27:08It tends to get people in trouble.
27:10It falls within the most dangerous range, at 36 degrees.
27:14It's just the perfect slope angle for just enough snow to build up on the bed surface.
27:21Look how much steep the crown is over on our left.
27:23At the crown, Carl examines the snowpack.
27:27He finds a weak layer halfway down.
27:29Remember how we're looking at that double weakness down at the...
27:32Yeah.
27:33But there must be another weak layer below it.
27:35Sitting on a pretty decent little ice crust.
27:37This is out more.
27:38To confirm it, Carl digs outside the avalanche, where the weak layer should lie undisturbed.
27:45And then that other weak layer is just this thing.
27:47It doesn't take long to find it.
27:48Yeah, this is a real thin weak layer right here.
27:51Look at this guy.
27:52The culprit is surface horror.
27:54You know what I mean?
27:55The large loose crystals that form the weakest bonds.
27:58Yeah, look at that.
28:07Now, and right there, that's the layer that the avalanche released off.
28:12We'll just use this first one.
28:13This one.
28:14A shovel test shows how vulnerable this snowpack was.
28:17Look at that first of those two breaks.
28:19Yeah.
28:20So, I mean, it's possible that the guy triggered it in this upper layer and then it broke down low.
28:25And look.
28:26There is not one weak layer, but several.
28:30And there's that one.
28:32That's the one that...
28:33Carl puts the results of this investigation together to form two possible scenarios.
28:38In one, the lower weak layer breaks first and brings down the whole snowpack.
28:47In the other, the top layer makes the initial break.
28:51Then, as the slab begins to move, its weight breaks the second weak layer below, resulting in the near-fatal avalanche.
28:59But as Carl knows, understanding an avalanche after the fact is the easy part.
29:09Okay, ready?
29:10Let's go!
29:11Woo!
29:12Woo-hoo!
29:13Beautiful!
29:15It's heading the mall that remains extremely difficult.
29:20We've been shut down by a pretty big storm, and we've had a total of 45 inches of new snow.
29:28Okay, we're going to go in and land. Are you coming in?
29:31My job is an avalanche forecaster, and I work closely with the highway crews to ensure that the safety of the road crews in the traveling public.
29:40This is Colorado's Highway 550. With over 100 avalanche paths lining its route, this roadway is one of the most dangerous in America.
29:57Here, no one can afford to take any chances.
30:00This stuff can build up and build up, and then it'll run when we don't want it to run.
30:07So any time the avalanche danger is on the increase, we'll recommend that the highway is closed.
30:14Then, when the storm's over, we can get our helicopters in with explosives to dislodge these pockets of unstable snow.
30:24I didn't know if you wanted to buy a bottle. I ran out of 25.
30:27With helicopters and hundreds of pounds of explosives, the operation entails a half-dozen sorties in a day-long pre-emptive strike.
30:38Fire now on a number one. Fire now on a number one.
30:46Fire now on a number one.
30:48Fire now on a number one.
30:51Fire now on a number one.
30:54Fire now on a number one.
30:55Fire now on a number one.
30:56Fire now on a number one.
30:57Fire now on a number one.
30:58Fire now on a number one.
30:59Fire now on a number one.
31:00Fire now on a number one.
31:01Fire now on a number one.
31:02Fire now on a number one.
31:03Fire now on a number one.
31:04Fire now on a number one.
31:05Fire now on a number one.
31:06Fire now on a number one.
31:07Fire now on a number one.
31:08Fire now on a number one.
31:09Fire now on a number one.
31:10Fire now on a number one.
31:11Fire now on a number one.
31:12Fire now on a number one.
31:13Fire now on a number one.
31:14Fire now on a number one.
31:15Fire now on a number one.
31:16Fire now on a number one.
31:17Fire now on a number one.
31:18Fire now on a number one.
31:19They give the avalanche room to run wild, to exhaust its deadly potential in an awesome
31:26display of power, speed and reach.
31:35But knowing ahead of time how far an avalanche can travel would help reduce the risk.
31:42A group of researchers at Montana State University are probing the hidden dynamics of the avalanche.
31:48To help people protect themselves from its destructive power.
31:53They do what no other research team would dare attempt.
31:58Trigger an avalanche onto themselves.
32:07Their risky experiment takes them to the cutting edge of avalanche science.
32:12What we would like to learn is what are the mechanics involved at the base of the avalanche
32:17because if you can figure out what's going on at the base of the avalanche then you can
32:20figure out what the overall avalanche is going to do.
32:25You're building a road through mountainous terrain.
32:28It would be really nice to be able to locate that road so that it doesn't sit in a hundred
32:33year avalanche path and get wiped out.
32:36In order to do that you need to know some of the mechanical properties of the flow.
32:41The actual experiment will take place later in the winter when the conditions are right.
32:46Today they prepare a shack that will be a window on the avalanche and the only protection from
32:52its force.
32:53The bomb goes off and about 10 seconds later after about 10 seconds of quiet and anticipation
33:03suddenly there's just a big whoosh as the avalanche goes by and over the top of you.
33:08That's pretty exciting.
33:10From inside the shack Jim will observe the avalanche first hand.
33:19He will monitor an array of instruments designed to capture the transformation of the snowpack
33:23from a subtle mass to a raging torrent and finally into ice hard debris.
33:28There's going to be four velocity sensors in there and as the avalanche goes by what
33:33we're interested in is how does the velocity change from the surface up into the avalanche.
33:40And so we will have sensors in here at various depths to measure that velocity.
33:46What they're aiming for is a computer model of flow.
33:51From it a more understandable picture of the avalanche should emerge.
33:56One that will foresee the worst a slope might produce.
33:59I think what we're shooting for is to build a model that will predict avalanche runouts.
34:04Whether it will cross a road, whether it will pick up a bridge and carry it down into the
34:11river bottom.
34:12In order to do that you need to know some of the physical properties about the avalanche,
34:16how hard it's going to hit these structures and again that relates to the mechanical properties
34:22of the flow.
34:24But we're waiting for more snow now.
34:28We get another couple feet of snow and we're in business.
34:32Success here is no small matter.
34:35Misjudging the potential of avalanche terrain can lead to the most catastrophic disasters,
34:41as it did in flattery Iceland.
34:46The steep walls of a rocky fjord dwarf this fishing village 30 miles from the Arctic Circle.
34:55Avalanches were a fact of life here.
34:57The community felt it was prepared.
34:59We've had avalanches from the mountain.
35:02We've had avalanches even that have affected our houses.
35:06But in another part of flattery, not in this part of flattery.
35:13In choosing where to build their houses, the people of flattery took history as their guide.
35:21Over the years many different avalanche paths emerged.
35:25But none reached beyond a certain zone and that defined the avalanche danger.
35:33When an avalanche warning was declared, only homes in the danger zone were evacuated.
35:43As they were on October 25, 1995, after a week of heavy snows.
35:48On Tuesday night, there was warning and people closest to the mountain, they left their houses.
35:58And people thought, okay, we are safe because we are down here.
36:02It's only a danger of avalanches up there.
36:07But townspeople learned that the mountain was about to declare a new danger zone.
36:13While the village slept, a disaster was building above them.
36:19At four o'clock in the morning, it descended.
36:24Scientists believe the avalanche began when a quarter-mile long, twelve-foot-high slab broke from the mountain.
36:32Within seconds, an enormous powder cloud formed on top, moving at more than 125 miles an hour.
36:42The avalanche soon took a path unknown in the history of flattery, bypassing evacuated homes and roaring deep into town.
36:54In all, 250,000 tons of snow came to rest in the village of flattery, killing 20 people, destroying 17 houses, and crippling its sense of security forever.
37:18In Fladri, we have always knew that there was a danger of avalanches.
37:44But we wouldn't have believed it if somebody would have told us that this could happen.
37:56In their complacency, the people of flattery are not alone.
38:04In Alaska, the city of Juneau may be facing a similar fate.
38:08The people know well what looms above the city, a phalanx of seven avalanche paths.
38:19Every once in a while, one will remind Juneau of its presence,
38:23as an avalanche did spectacularly in 1972,
38:28when its powder cloud rolled right through the center of the city.
38:33No one was hurt, but Juneau hasn't always been so lucky.
38:38Ten years earlier, a massive avalanche swept through one neighborhood on the city's edge,
38:46damaging 35 homes.
38:50This disaster sent a clear message of what the mountains are capable of.
38:56But has the warning been heard?
38:58Many homes remain dangerously close to the mountain.
39:02This has been described over the years by a number of people
39:13as being the largest potential avalanche disaster in the makings.
39:19Avalanche educator Doug Fessler has been sounding the alarm for decades.
39:23It's an infrequent running path, but when it comes down big, look out.
39:30Flying over the most threatening path, the danger is obvious.
39:35But not to the residents below.
39:38People that live here love it.
39:42It's so convenient and yet cozy.
39:44I don't know if I'm naive or in denial or what,
39:50but the last time anything happened was 30-some years ago.
39:55The house has been here since 1950, and it's still here.
40:00It's something we're aware of,
40:01and it's not nice to have this sort of Damocles over your head,
40:05but we're more than delighted to get this house.
40:09I doubt that any of these people or very many of these people
40:15have ever been through a bad avalanche
40:17or they've ever seen dead bodies or seen buildings ripped apart.
40:23The bottom line with this path is that it's really not a question
40:26of if they're going to get nailed by a big one.
40:29It's like a ticking time bomb sitting there waiting,
40:32and at some point when the conditions are right, they'll come.
40:39To help end this perilous guessing game,
40:441,500 miles away,
40:45the research team from Montana State University
40:48heads back out into the Bridger Range.
40:58Beautiful day.
40:59They plan to follow through on their experiment
41:02to look at an avalanche from the inside
41:05and undermine forever its weapon of surprise.
41:10But first, they must find their shack of instruments,
41:14lost for now in the storm.
41:19They take care as they move,
41:22knowing that at any moment they could trigger a slide.
41:25I think that our concern today is wind loading off the cornices,
41:30and since we don't have any wind coming through this general area,
41:33I feel like this is going to be good,
41:35but if you'll just keep an eye on me,
41:36I'll give a quick ski cut.
41:39They risk only one person at a time
41:41across the most treacherous slopes.
41:44It didn't feel like it moved much,
42:00but you might want to make your run next to the tree.
42:02Yeah.
42:03You want to go, Fred?
42:04Go ahead.
42:05I'll go, Fred.
42:09For a few brief seconds,
42:11each is on his own.
42:14Once they locate the shack,
42:27they have to remove the accumulated snow.
42:32Well, I don't know if I broke it,
42:33because I didn't want to have to stand up now, Jim.
42:37Hunched is hunched.
42:41They prepare their instruments
42:43and take measurements of depth and density.
42:47They will compare these numbers
42:48with those they find later
42:50in the avalanche and its aftermath.
42:52About 130 at the top,
42:54ranging down to about 280.
42:56Sounds good.
42:57Their chance to observe the dynamics of the avalanche
43:00will last only a few brief seconds.
43:03We've got a couple more.
43:04Colored powder will help them measure velocity.
43:09To ensure the slide is triggered,
43:15they use four five-pound hand charges.
43:22Jim and Jay will be inside the shack.
43:25The rest of the team watches from a safe spot near the trees.
43:28All are tense.
43:31They have one shot.
43:32I cannot move.
43:48You need to be dug out.
43:49I'll see if they're all right in there.
43:54Someone got a radio?
43:54I got it.
43:55They're alive.
43:56Are they happy?
43:57Well, Scotty, Jay and I cannot move.
44:00We are buried inside the hut.
44:01Help me, get me out of here.
44:03How you doing?
44:05You got that?
44:06Yeah, but you're going to dig fast,
44:07because I'm, like, in a bad position.
44:09Being buried alive was not part of the plan.
44:13The size of the avalanche caught them off guard.
44:16I was pinned.
44:17Data log.
44:18We got data.
44:19Good.
44:20But in risking themselves,
44:21the researchers have obtained valuable information.
44:24They clocked the avalanche at nearly 50 miles per hour.
44:27There's two distinct layers in the flow,
44:30and it's really homogeneous.
44:31Despite its chaotic appearance,
44:33they find evidence of a multi-layered structure.
44:35And we saw something similar to that last week, remember?
44:37A lot of times it'll pick up some structure in the debris,
44:42like some finer chunks and stuff,
44:43but it also would be pretty smooth.
44:46It could very easily have come down,
44:49filled in all the irregularities that we left,
44:52deposited that,
44:54and then float over the top of that as a separate layer.
44:58These findings offer numerical clues
45:00to the rules that govern the power and extent of flow.
45:04They will soon be used with the computers
45:07to predict avalanche run-out,
45:09a tool of the future
45:11that could hold the key
45:12to protecting people, towns, and roads.
45:20In Switzerland,
45:21nearly two-thirds of mountain roads
45:23wind their way through avalanche terrain.
45:25There are a lot of avalanche defense structures there already,
45:38but to make the whole road absolutely safe
45:42would cost a fortune.
45:43A new approach is spearheaded
45:45by Dr. Tom Roussi of the Swiss Institute.
45:48He is leading the development
45:50of the most advanced early detection system in the world.
45:54The plan is to capture a precise picture
45:58of what's happening where avalanches start,
46:01thousands of feet above the roadways.
46:03Here, on the shoulder of a 10,000-foot peak,
46:08Tom and his colleagues have come to where avalanches are born,
46:12an area known as the starting zone.
46:16They are looking for a spot to place a high-tech station,
46:19one that will keep a watchful eye
46:22on the snow that accumulates here.
46:26It should be at an altitude
46:27where major avalanches actually start,
46:30but it's always a trade-off.
46:31The closer you get to the places
46:33where avalanches occur,
46:35the more problem you have to find a safe place.
46:39Already, these mountains are being watched
46:41by a nearly invisible web
46:44of over 40 weather towers
46:45designed to safeguard the region's vital roads,
46:48like Simplan Pass.
46:52A bloodline that links Switzerland with Italy,
46:55it has long been a victim to surprise avalanches.
47:00But maybe no longer,
47:02because high above the most vulnerable stretch of road,
47:05one experimental tower stands vigil.
47:10To be effective, it needs to be accurate.
47:15Tom takes the snow depth and temperature manually
47:17to compare to the readings taken by the tower.
47:22Along with snowpack data,
47:24the tower measures humidity and air temperature,
47:27all information vital to forecasters.
47:30For wind statistics,
47:33he relies on another tower perched 1,500 feet above.
47:37For the past few days,
47:39it has mysteriously gone silent.
47:44Wind direction and speed indicate whether snow is drifting
47:48from one side of the mountain to the other,
47:50overburdening the snowpack that threatens the road below.
47:55At this height, above any peaks or obstacles,
47:58true wind speed can be obtained.
48:01But it makes repair of the instruments a deadly challenge.
48:06Tom finds it encrusted with ice.
48:09With a few blows, Tom frees the wind meter.
48:12Now the station is ready to resume its work,
48:18giving local forecasters the vital statistics
48:21from the very locations where avalanches form.
48:24The next morning,
48:37Tom dials up the station he just visited.
48:40He confirms his repair of the wind station.
48:44Well, a couple of days ago,
48:46we didn't get any data,
48:47and now that the station works,
48:50the wind speed is about 20 kilometers.
48:52Then he checks the manual readings
48:54of temperature and humidity he gathered in the field.
48:57To his relief,
48:58they match the transmissions from the station.
49:03This constant stream of information
49:05is also being downloaded into computers
49:07at the Swiss Institute
49:08to help them better understand avalanches and forecasting.
49:13Exactly.
49:14What we want to know in the end
49:16is what the mechanical properties are.
49:18We are far away from that.
49:19In the past,
49:20weather forecasting was based
49:21on the forecasters' experience and intuition.
49:26And nowadays,
49:28weather forecasting is based on computer models.
49:32In avalanche forecasting,
49:33our understanding of the physics of snow and ice
49:36has improved a lot.
49:37Because we measure the snow depth with...
49:40And we now need to put this knowledge
49:42into computer models,
49:43and that will help to improve avalanche forecasting significantly.
49:47Wow.
49:48A rendering of the layers in the snowpack
49:52is at last emerging,
49:54fueled by vast amounts of data from the stations
49:57and a better understanding of snow dynamics.
50:00Half a world away,
50:05over another mountain range,
50:07Carl Berkland is also conducting research
50:10to sharpen the tools of forecasting.
50:12Today's ambitious experiment
50:19is simple in design,
50:20but complex in execution.
50:23He's devised a way to measure
50:25how snow stability changes
50:27over the entire Bridger range.
50:32Since dawn,
50:33the helicopter has been ferrying volunteers
50:35in teams of two
50:37to designated sites along the 20-mile ridge.
50:40They head down
50:43with the goal of digging
50:44as many snow pits as possible in one day.
50:48One of the first things we have to do
50:49is get out here,
50:51dig 70 to 80 pits,
50:53and try and map
50:54what's going on
50:55on one given day
50:57throughout a mountain range.
50:58And no one's done that before.
51:01Stability tests find the weak layer.
51:04And a ram penetrometer
51:05measures how much force it takes
51:07to break through all the layers.
51:09These results,
51:11plus slope angle and direction,
51:14are carefully recorded.
51:15And the hope is that
51:16we can take all this data
51:17and combine it in such a way
51:19that we can start to describe
51:21how snowpack changes
51:23with changes in terrain.
51:26Eventually,
51:27Carl is able to map snow strength
51:29across the entire range.
51:33The red marks areas
51:34most prone to avalanche,
51:37a deadly convergence
51:38of steep incline
51:39and weakly bonded snow.
51:42It is only a fleeting glimpse
51:44of conditions
51:45under constant change.
51:47But mapping
51:48is a first step
51:49in the eventual improvement
51:50of avalanche forecasting.
51:54But places like Iceland
51:56can't wait
51:57for better forecasting methods
51:58to be refined.
51:59Here,
52:01a town prepares
52:02for another winter.
52:04It's been a little over a year ago
52:05since the disaster in Flattery
52:07which killed 20 people.
52:09And
52:10in this past year,
52:12we've been
52:13contemplating and designing
52:15defence structures
52:18for the town of Flattery.
52:20We've come up with a
52:21design
52:22called
52:24a deflecting wall
52:25which is aimed at
52:26diverting avalanches
52:27away from the village.
52:30The mission
52:31is to anticipate
52:32the worst
52:33so the town
52:34will not be fooled again.
52:40At the base of the mountain,
52:42a wall is rising.
52:4320 million cubic feet of earth
52:46reaching 60 feet high.
52:48It is designed
52:49to divert avalanches
52:50twice the size
52:51of the one
52:52that surprised Flattery.
52:53Avalanche comes down,
52:54it comes shooting down
52:55this way
52:56and hopefully
52:57it'll hit the wall
52:58right over here
53:00and it'll be deflected
53:02down alongside the wall
53:04and
53:05it may not look like
53:06much right now
53:07but we do have
53:08half of it built.
53:10We'll go another
53:11seven or eight meters up
53:12and
53:13this way
53:15we hope to give them
53:16a really good sense
53:18of security.
53:18Cool.
53:19More help
53:25may be on the way.
53:27The scientists
53:28around the world
53:28work slowly,
53:30painstakingly
53:31to unravel
53:31one of nature's
53:32most daunting puzzles.
53:35New technologies,
53:37new techniques
53:38and new understanding
53:40are transforming
53:41the tools of avalanche,
53:43prediction
53:43and control.
53:44But while the future
53:47may hold promise,
53:50the snows
53:50will not wait
53:51and with the coming
53:53of each winter season,
53:55those living
53:56among the mountains
53:56must brace once again
53:58for what might
53:59come their way.
54:02The avalanche.
54:04NOVA pioneered
54:18the natural disaster
54:20documentary.
54:21At NOVA's website,
54:23enter the danger zone.
54:25Watch an expert
54:25capture an avalanche,
54:27the white death,
54:28on film.
54:28Go to www.pbs.org.
54:34To order this show
54:44for $19.95,
54:45plus shipping
54:46and handling,
54:47call 1-800-255-9424.
54:52And to learn more
54:53about how science
54:54can solve the mysteries
54:55of our world,
54:56ask about our many
54:57other NOVA videos.
55:01Next time on NOVA,
55:03take off.
55:04Contenders battle
55:05the odds
55:06and the elements
55:07in a balloon race
55:08around the world.
55:09But hazards loom
55:10every step of the way.
55:12I've just entered
55:12Libyan airspace.
55:14Danger in the jet stream.
55:16One oom
55:20is here.
55:21Justine rFrom.
55:29The��
55:29is here.
55:30So,
55:31Junei,
55:31the DIRECTOR
55:31they're
55:32there.
55:32It's here.
55:33This wyпол
55:33seemsanche
55:34to have a good
55:38change in the future.
55:38Before we can see
55:38their radio
55:39from the clock,
55:39ř придумando
55:39and hurling
55:40from ...
55:40and how they're
55:40we're being
55:41with a beautiful
55:41LA
55:41and adventure
55:42from the outside.
55:43For the science
55:44NOVA is a production of WGBH Boston.
55:59Major funding for NOVA is provided by
56:02The Park Foundation, dedicated to education and quality television.
56:08And by the Corporation for Public Broadcasting and viewers like you.
56:14This is PBS.
56:26Coming up on NOVA.
56:28When the best T-Rex ever is found, everyone wants a piece of the action.
56:33The feds, the ranchers, the scientists.
56:36Who gets the dinosaur? Curse of T-Rex.
56:44The End
56:46The End
56:48The End
56:50The End
Recommended
1:05
|
Up next
1:13
1:53
29:13
1:27
1:52
1:03
1:40
4:40
28:36