Horizon

This is really exciting.

We've been sitting in the UK

waiting for just the right snow conditions for ages.

Then, two days ago, we got the call to say that now is the time.

So, here we are, about to set off an avalanche

just there, on that mountain.

Avalanches are unstoppable forces of nature

that kill hundreds of people every year.

It was kind of a bloodcurdling feeling, really.

I had snow jammed down my throat,

in my eyes, up my nose,

and I really, really needed air.

Even in Britain, around 30 people have lost their lives to avalanches

since the year 2000.

Yet we know surprisingly little about them.

We can't predict when or where they'll strike,

or how big or devastating they'll be.

I'm Danielle George, an engineer and physicist...

Wow!

I've never been in a room where it's snowing.

...and I've gathered an international team of scientists

in the Canadian Rockies for a unique and dangerous mission.

We're going to rig an entire mountain

with cameras and instruments,

and then we're going to load this helicopter with explosives...

Good luck, boys.

Thanks.

...and use it to send a massive avalanche hurtling

down these slopes.

We want to find out why avalanches happen,

where they will strike...

So she's dropping...

...and why some of them become devastating killers.

Are you OK? Big, deep breath. Yeah. You survived an avalanche.

That is a truly...

...frightening experience.

No-one has attempted an experiment quite like this before.

If it works, it will revolutionise our ability to predict

and prevent avalanches.

OK. Here we go.

Wow, look at that!

It's early on a Sunday morning, in March 2018,

and a team of snow scientists arrives in a remote valley

in the Canadian Rockies.

For many, this is their first sight of The Fortress,

a 3,000m peak in the Kananaskis Range.

We've brought these scientists here now

because, for the next few days,

the avalanche risk will be at its highest.

We had about 45cm of snowfall this past week,

and we're heading into another warm-up cycle here.

You know, pretty concerned about the hazard.

I think we'll see a lot of activity in the next couple of days.

OK, so, you see those two trails?

I think that might be a good place for a scan location.

Over the next two days,

the team will be surveying the mountain...

One of the things that's really interesting

is the snow stays so much colder at the top

than lower down the mountain,

that affects how fast it moves.

...trying to learn all they can about the snow conditions,

before we trigger what will be one of the most closely-studied

avalanches of all time.

All right, that's it. Installed.

We've designed this experiment to fulfil three key aims.

First, we want to test our understanding of avalanches

by trying to predict the size, path and power

of the one that we're going to set off.

Second, by studying that avalanche,

we want to learn more about how they work,

why they start and how they do so much damage...

...and thirdly, I want to understand the human cost of avalanches.

Whilst the other guys investigate the avalanche remotely,

I'm going to be getting hands-on with the snow,

finding out what it's really like to be caught in an avalanche.

I want to know what makes them so dangerous,

and if there's anything we can do to survive them.

The star of the show will be this car,

which is going to become a mobile laboratory.

We're going to rig it with sensors,

and then drop it into the surging heart of the avalanche.

If it all works, we will come away with valuable new information

that could help save lives.

We're in a real race against time here.

The slopes above us are covered in fresh snow,

so they are primed for avalanches.

At any time, that snow could come at us,

so we don't want to be down here for longer than absolutely necessary.

So, we need to get this experiment ready and done.

The worst thing that could happen

is that the avalanche triggers spontaneously before we're ready.

So I think, realistically, we've got about 48 hours

to get everything in place.

It's going to be busy.

The next two days will not just be busy,

they'll also be dangerous.

The team will be working in an active avalanche zone.

So, to prepare us for the possibility of being caught

in an avalanche, the day starts with a safety briefing

from local guide and avalanche forecaster Jason Kuruc.

All right, folks,

I just want to take the next few minutes

and show you some of the avalanche safety equipment

that we're going to be using.

We're going to start off with the transceivers.

Danielle, can I ask you to help me out here? Yeah.

So, we're going to put it on underneath your top layer. OK.

So, we're just going to put it over your arm

and then over your head,

and then we'll snug it up, so it's sitting right about here.

I'm going to hand out...

These portable transceivers

are the most important piece of equipment we have.

If any of us are buried in an avalanche,

they'll send out a signal that will alert the rescuers to our position.

For those of us not used to working in the mountains,

it's a daunting prospect.

So, I have a question.

What should I do if I get caught in an avalanche?

So, you want to be trying to do this back crawl swimming motion

to try and keep yourself at the surface of the snow,

and at the very last moment,

when you feel yourself stopping moving,

you want to try and punch a hand up, as well.

That might help us to find you easier.

I feel quite breathless.

You know, when you're talking about it... Mm-hm.

...you know, the feeling of being buried, I'm like...

You know, panicking.

Yeah, it can be...

...the most exciting and worst few minutes of your life, for sure.

To get some idea of the devastating impact

of being caught in an avalanche, we have to leave The Fortress

and go to the quiet college town of Missoula, Montana.

Avalanches had never been an issue here,

but in early 2014, the town had become a winter wonderland.

It had snowed for 16 of the 28 days of February...

...and everyone wanted to make the most of it.

So, about four o'clock in the afternoon,

I'd just gotten home, I was sitting inside the front room here,

and the kids asked to come out and play.

And I said, "Sure, go play."

And it was about five minutes after that,

I heard a noise coming around the corner here.

And it sounded like a plough truck that was ploughing snow,

like, coming round on this back road, which was really weird,

because they weren't even ploughing the main streets,

the weather was so crazy.

It felt like an earthquake.

It shook the whole house.

You could hear the windows shudder.

And I saw this plume of white snow, it looked like smoke in the air,

just almost like a whiteout.

My wife and I were just sitting in the living room

and thinking about what we were going to do for dinner that night,

and all of a sudden, and instantaneously,

I went from sitting on the couch

to being covered by my house.

It was like a bomb went off,

and my house was sitting on top of me.

And within seconds, I heard my wife screaming,

and, you know, I said, "What's going on?"

and she was just screaming, "My babies, my babies!"

A river of snow had come sweeping off the mountain,

flattening Fred Allendorf's house and burying Casey's kids.

Ten-year-old Coral clambered out unharmed,

but there was no sign of eight-year-old Phoenix.

I saw the lady scrambling about

and wondering what the heck had happened to her son.

I know the statistics.

People don't live that long underneath snow.

You know, it's like, you're sitting there,

you're trying to tell your wife that he's still alive

and, like, really, you know that he's dead.

I was lying there, thinking that either

I was going to suffocate, freeze to death

or somebody's going to find me.

People were coming up with shovels and avalanche probes.

People were shouting out stuff. There was live electric wires.

So, it was quite chaotic.

It was quite a long time before they actually found him -

45 minutes.

He ended up being trapped in this window down here,

in an air pocket.

He was pushed up against the window in an air pocket,

and that's actually what kept him alive.

So, it's almost a miracle that he survived.

And while Phoenix was rushed to hospital,

the search continued for Fred Allendorf and his wife.

We started off five feet away from one another,

and my understanding is she was found about 20m away,

and she was obviously really hypothermic,

and she had lots of internal injuries.

And that was on Friday afternoon, and she died two days later.

The striking thing about the Missoula avalanche

is that it came out of the blue.

No-one had thought the town was in danger.

One of the main reasons we're doing this experiment

is to prevent similar tragedies happening in the future,