Original subtitles

Avalanches are mesmerizing killers,

stunning when observed from afar,

yet fatal when caught in their trail.

I just thought I would die.

The worst thing, of course,

was to see the people that were dead

and the people that were really bad.

Broken legs and stuff, yeah.

It was horrible.

These steamrollers of nature

can travel at incredible speeds

of up to nearly 300 kilometers per hour,

generating pressure waves strong enough

to knock a bus off a bridge,

with an impact force

powerful enough to level forests

and deadly enough to take lives.

If you’re trapped in an avalanche,

there’s almost certainly nothing that you can do.

The power and speed

of these mountainside phenomena,

coupled with their unpredictability,

makes it particularly difficult

to safeguard against avalanches.

When the avalanche happens, it happens so fast,

people could not outrun it.

With fascinating expert insights

and first-hand accounts from survivors,

in this episode we’ll be investigating

two disaster avalanches that struck Everest

in 2014 and 2015,

resulting in a devastating number of casualties.

We’ll also be taking a look at a series

of major avalanche incidents in the Alps.

So, what exactly are avalanches and what causes them?

Snow is an extremely dynamic

and complex medium to understand,

and the same applies to avalanches.

So from a scientific point of view,

we can predict a lot, but not everything,

and we rely on both historical data

and also snowfall records to get an idea

on where the danger zones are.

It’s all statistical, it’s like a weather forecast.

You might say it’s an 80% chance of rain today

and avalanches are the same.

You could say, you know, there’s a high risk

of an avalanche happening there today but you can never predict

exactly when it’s going to happen.

The Canadian government page

dedicated to mountain safety

describes the forecasting of avalanches

as being as much an art as it is a science.

There are two aspects that are going to decide

when an avalanche will occur.

So there is the strength of the snow

and there’s the, the gravitational force on it.

So when the load on the snow exceeds the strength,

the snow, then it will slide.

The difficulty with predicting avalanches

is that snow is a very variable and dynamic material.

The strength of snow can vary enormously

and it’s very hard to predict how,

at what point

the snow slope will fail

and that can change a lot over time

with the weather conditions,

so snow accumulating on the ground

is really just the beginning of the story.

But although avalanches come

in a variety of shapes and sizes

and might be tricky to label,

they always consist of three key features.

The starting zone, the avalanche track

and the runout zone.

The starting zone is usually situated

at a higher point of a mountain

and is the most unstable point of the slope.

This is where the avalanche begins.

The avalanche, now set in motion,

crashes down along a natural path,

which is the avalanche track.

Finally, the avalanche course ends

and it comes to a stop in a pile of snow and dross

at the bottom of the slope.

This is the runout zone.

But what actually triggers an avalanche

at the starting zone in the first place?

A series of factors including the terrain, snowpack,

and weather conditions

are all key triggers

that can kickstart an avalanche event.

Avalanches are most prevalent

around the Northern hemisphere in winter months,

with the highest risk period

usually during snow storm events.

For an avalanche to happen, you need a ’cake layer’ effect.

a surface bed of snow,

a weaker layer that can collapse,

and an overlaying snow slab.

Most avalanches actually happen

in the middle of snowstorms

and it’s just fresh snow accumulation

and they don’t cause so much trouble mostly.

But then other things that can trigger them

are the sun if the snow starts melting

and you get water, and this can start an avalanche

or if the snow weakens, so it can happen many weeks

after the snow’s fallen,

if the snow crystals are continuously changing

and if they get weaker, then that avalanche can also happen.

And then there are other effects.

Like, there can be earthquakes that can trigger them sometimes

and then also animals.

All of these natural variables

affect when and how an avalanche will occur.

But one of the biggest triggers

are actually the ones caused by ourselves.

Human activity is responsible

for a staggering 90 percent of avalanche events.

If you ride a snow scooter or you ski or snowboard

you can also unfortunately create an avalanche

at the wrong time and then you could be caught in it.

I turned on the main part of the face

before the slide actually caught up with me.

Basically, after the slide started to move

and propagated out, I just got swept down

into the main gutter of that chute.

Once I went over the cliffs I was under,

you know, definitely under the snow.

That was when I started to get really scared

because I knew how fast slides consolidate

and how little chance you have once you’re set up.

So that’s when I really started to struggle

and really, really fought as hard as I could for my life.

In North America and Europe,

avalanches kill around 150 people each year,

a significant increase since the 1950s.

This rise in fatalities has been directly linked

to an increase in snow sports,

snow mobiles, skiers and hikers.

A 29-year-old snowboarder in the U.S.A.

was tragically buried and killed

when he and his friends inadvertently triggered

an avalanche while coming down the slopes

of Jackson Hole Mountain Resort in Wyoming.

Backcountry skiers and snowboarders are advised

to carry avalanche beacons that emit radio waves,

in case they are buried beneath the snow,

in order to alert rescuers who can dig them out.

But the U.S.A. is not the only region

to experience avalanches where humans are present.

Mount Everest, the highest and most famous

mountain on the planet,

attracting world-class mountaineers

from all across the globe.

But on the 18th of April 2014,

the mountain was in the spotlight

for a very different and tragic reason.

There are a lot of avalanches in the spring

and these are caused by the longer days

and the increased heat from the sun

and this melts the snow.

So then the water then trickles down

to the snowpack to the bottom of the snow.

And this can lubricate it, so you can get huge avalanches

because all of the snow all the way down to the ground

can come down, and these are often the most,

the most dangerous and the biggest.

At around 6:45 a.m., disaster struck.

A powerful avalanche descended

upon a group of Nepalese mountain guides,

known as Sherpas, who were in the middle

of preparing the route and transporting equipment

for seasonal climbers.

Sixteen Sherpas were killed by the landslide,

making it one of the deadliest single incidents

ever recorded in the history of the summit.

The avalanche struck at the Khumbu Icefall,

a treacherous passage between Base Camp and Camp 1

riddled with vast open crevasses

and gigantic columns of ice known as seracs.

The avalanche was caused

when one of these titanic seracs dislodged.

The dislodged ice block would go on to trigger

a powerful avalanche made up of ice, rock and snow.

This snowslide bombarded through the Khumbu Icefall,

descended on the Sherpas and buried them entirely.

Every time you go through the Khumbu Icefall,

you’re taking your life in your hands.

You can be hit by avalanches.

You can fall into crevasses or you can have blocks

of the walls of the crevasses falling off on you.

And I think in total there are

hundreds of people who’ve been killed there.

This type of avalanche

is known as an ice slide or ice avalanche.

Ice slides are particularly deadly

due to their unpredictability.

They are birthed by erratic fractures,

rapidly spreading through gigantic ice blocks.

Minimal exposure

or complete avoidance of ice fields

is the only real warning forecasters can offer.

In the tragic event of Everest, however,

there was no chance of a forecast

to prevent the incident.

All that remained was a community

and families left to mourn their dead.

The Sherpas are highly skilled and strong climbers

indigenous to Nepal,

with some of the most skilled amongst them

called ’Ice Doctors’.

According to the Himalayan database,

an estimated 350 to 450 Sherpas are hired above the base camp

during climbing peak season as guides

for Western mountaineering tourists to Everest.

These guides are charged with the most dangerous

and laborious tasks of expeditions.

Such tasks include hauling heavy equipment

and stock up the slopes,

fixing ropes and carving out routes in the ice

for their foreign clients,

who are usually stationed in the base camp below

as these preparations are underway.

The Sherpas and the local community

know that each time they head up

through the glacial crevasses of Everest’s slopes,

it could well be their last expedition.

But in one of the world’s poorest nations,

it’s a risk that many guides must take

in order to provide financially for their families.

It is difficult to get exact figures

on just how much Mount Everest contributes

to Nepal’s tourism industry,

but estimates suggest that the great mountain may bring in

over $3 million from climbers alone every season.

The resulting avalanche tragedy saw Everest shut down

for the rest of the season, an economic blow

to both the country’s tourism industry

and communities like the Sherpas,

dependent on the mountain for their livelihoods.

But given the scale of the disaster,

it was the most appropriate and safe response

the government could offer.

At the time, the avalanche of 2014

was the biggest disaster in the history of Everest

with the highest number of fatalities

ever recorded on the mountain.

No one could imagine a tragedy of that magnitude

happening again any time soon.

In April 2015,

the mountain was reopened again for the season.

Climbers and adventurers from all across the globe

flocked to the legendary heights once more,

ready and eager to scale its peaks.

Everest was back in business.

But almost a year to the day of the 2014 incident,

disaster struck the great mountain once again.

A regular Saturday afternoon, on the 25th of April 2015,

in Nepal’s bustling capital city of Kathmandu.

Suddenly, the earth moved.

A quake located 225 kilometers west of Mount Everest

and measuring in at 7.9 on the Richter scale,

tore through the capital, killing nearly 9000 people.

For Nepal, still recovering

from the events of the previous year,

this was a horrific blow.

But up on its highest peaks,

more tragedy was to follow.

Minutes later, on Mount Kumori,

a 7000-meter mountain,

situated just a few kilometers from Everest,

a powerful avalanche triggered by the quake roared down

and ripped through the middle of the busy Everest base camp,

submerging it in snow.

I’m just looking up on my left

and just watching this huge cloud.

It really was like an explosion.

Very impressive and then just basically diving

almost into the tent, under the table.

I remember telling everyone, "Get down, get down, get down."

What? You know,

you just listen and I ducked under the dining table--

It was the dining tent-- And I closed my eyes.

I don’t even remember hitting the floor

when this sound was just like,

wind just coming

and then just, it just hits you it’s like,

something hits you, I don’t know,

and you start rolling, tumbling

and I remember hearing the sound like...

things accumulating, like, falling on top of us

and that’s when I thought, I said,

"This is it, I’m gonna be buried alive,"

and panic, just pure panic, you know, not wanting to die.

When it hit, you think, "This is it," you know.

"I hope if it ends,

I hope it’s painless, I hope it’s fast."

Mount Everest has a tumultuous origin

that can be traced to the Earth’s

earliest tectonic activities.

Millions of years ago, the Himalayan mountains

gradually emerged from the crust

as Earth’s Indian and Eurasian plates collided.

And today, Everest towers

at 8848 meters above sea level.

But the seismic activity

which birthed the great mountain,

continues to have an impact,

specifically on avalanche events.

Earthquakes can act as triggers for slab-type avalanches

on slopes and mountains by inducing ruptures

in the weaker layer of snowpacks.

These ruptures then spread through the weakened snowpack,

till the slab of snow above gives way and starts to slide,

becoming the starting zone of an avalanche.

Some of the biggest earthquake events

around the world have been followed by avalanches,

including the 7.1 magnitude New Zealand earthquake in 2010,

the 7.9 magnitude Peru earthquake in 1970

and the 9.2 magnitude Alaska earthquake in 1964.

When an earthquake happens,

we get seismic waves generated

and these are waves that make the ground move

and actually cause all of the damage that we see

to buildings and in photographs and on the news.

But because the ground is moving,

if the ground is particularly unstable,

or if snow on top of the ground is particularly unstable,

that movement of the ground,

and we’re not talking very much,

we’re talking millimeters or smaller amounts of movement,

that can actually destabilize rock

or snow or ground

and cause avalanches or landslides.

On that fateful day

on the 25th of April,

those two plates

that birthed Everest

collided once again.

April is peak season on Mount Everest.

Close to 1000 people were on the mountain

at the time disaster struck, with a majority of that number

settled down in the south side base camp,

preparing for expeditions in the upcoming weeks.

The vast tent city known as Base Camp

has been described as a temporary home

to people from all across the world.

There’s several hundred people that come together there

every year in spring and they wait

for the right conditions and they prepare

for their bit to climb Mount Everest.

So it’s a big hub of activity.

This was a particularly busy month,

and there were more people than usual in the camp.

Figures show it was

an almost record-setting year

for Everest, in climber numbers,

with nearly 400 climbers

securing permits for the mountain.

Survivors have remarked

on the relaxed lunchtime atmosphere

at Base Camp that fateful day, with groups enjoying meals,

socializing and checking the Internet.

It was an idyllic scene.

But that would all tragically change

in the blink of an eye.

The ground is shaking.

The whole ground is shaking.

Do you hear that?

One of the guys from our four-man team

started shouting "get down, get down,"

and as we looked behind there was a big powder dust,

you couldn’t see at all, coming towards us.

Pull. Pull.

Pull!

"Come under my jacket. Come under my jacket."

Are you okay?

Yeah.

The shaking stopped.

I opened my eyes and everything was white.

There was just a lot of snow

and I remember trying to scrape it away

so I could breathe

and my hands were covered in blood.

Then when you hear it, there was nothing,

no sound at all, just pure stillness

and it was pretty haunting.

No, no, wait, wait!

Wait, maybe there’s coming more.

Maybe in the kitchen tent. Yeah, maybe.

Stay together, stay together

and we try to find the kitchen tent.

Oh, no. There is no kitchen tent left.

The kitchen tent. "Yeah."

The avalanche appeared like a nuclear mushroom cloud

and rapidly descended on Base Camp.

The tent city was buried in snow.

An estimated 21 people were dead,

with 120 left injured.

There was over 200 volunteers

and we received maybe 73 injured climbers

that we safely evacuated back down to Kathmandu.

And just as we’d finished, there was another earthquake.

Casualties included both local Sherpas

and tourists of various nationalities.

Among the dead were Sherpa guides,

Nepalese, and tourists from America and China.

The force of it was incredible.

It comes over you lightly

and then you’re just totally entombed

in rock and snow and everything

like all sorts of propellants coming at you.

So, like, a lot of them hit me in the back and took me over

and I started flipping like a rag doll.

The devastation was extensive.

What had been only a few hours before,

a functioning settlement,

was turned into a desolate scene of flattened tents

and blocks of rock,

all scattered around a site

entombed in snow.

Rocks and the winds had taken them out completely.

I mean, I can’t describe it. Our kit was everywhere.

Those who were not at base camp

also found themselves trapped by the avalanche.

These were the Sherpa guides who had gone ahead

to set up the camps, and mountaineers

stuck on Camp 1 and 2 above Base Camp.

Although there were no fatalities,

the group, made up of approximately 200 individuals,

were struck from above, with some sustaining injuries.

The earthquake, aftershocks and avalanche

destroyed the route through the Khumbu Icefall,

the same hazardous region where the powerful avalanche of 2014

had barreled through, killing 16 Sherpas.

There was one positive

for the climbers on Base Camp 1 and 2.

Due to the multitude of "up and back" trips

required in preparation for an Everest Climb,

there were enough provisions

to see the stranded climbers through several days.

But both those at base camp

and the climbers camped above

were locked in a desperate attempt

to treat and care for their wounded comrades.

There are really three main causes

of fatalities in avalanches.

The first would be trauma.

If you’re hit by something

that is moving fast and is heavy

and you can be very easily swept away by a large avalanche

so you’ll also be bashed against rocks,

possibly swept over cliffs.

If you survive that, as the avalanche stops,

there is considerable danger of being buried in the snow

and then the next cause of death would be suffocation.

Snow is a porous material

with a lot of air trapped in it.

So it’s not an immediate suffocation.

Statistically, if people can be dug out of the snow

within about five minutes

they have a very high chance of survival.

After half an hour there’s quite a low chance of survival,

maybe in places where emergency services would take

more than a half an hour to get to you.

So in that situation,

people are really relying on being rescued

by other members of their own party.

It’s also possible to be partially buried

by an avalanche

so you may still be able to breathe.

But the avalanche snow, once it’s settled,

will set very hard. It can be very difficult

to dig yourself out of an avalanche.

So after that there’ll be a risk of hypothermia.

With numerous fatalities and injuries,

surviving climbers sent desperate messages

for helicopter rescue.

According to reports,

22 of the most seriously injured at Base Camp

were flown to Pheriche village, the closest medical facility.

However, bad weather and communications

were hindering helicopter rescues.

Fortunately, I think,

nobody died in the higher camps.

They all managed to be rescued by helicopter

or managed to climb back down.

It also proved extremely difficult

to evacuate climbers trapped above Base Camp

as the route back through the dangerous Khumbu Icefall

was severely damaged.

However, the sheer scale of the disaster

and the casualties needing relief

was an enormous task for rescuers.

Tightly wrapped sleeping bags

containing the bodies of the dead

lay scattered across the battered encampment.

Transporting the injured and the deceased

off Mount Everest was a monumental endeavor.

Due to the large number of casualties,

a series of multiple trips were required

as only two or three people could be transported at a time.

This was an unforeseen mass-casualty event

that would put a strain on even an urban hospital.

In order to effectively treat the large influx of victims,

those in the most critical condition

were labeled with an "E" for "Evacuation" sign.

The entire rescue helicopter operation

and assignment of transportation

was a massive and difficult endeavor.

Eventually, on the Monday,

two days after the avalanche struck,

most of the climbers who had been stuck on Camp 1 and 2,

above Base Camp, were transported down.

There were only three small helicopters,

making multiple two-minute trips.

But, at last,

all the survivors were safely brought back down

to the eerily silent base camp below.

They might have been unsuccessful

in fulfilling their ambitions

to reach the top of the famous mountain,

but, incredibly,

they have all come away still alive.

Because the avalanche ran straight through Base Camp,

a lot of the infrastructure and logistics

of all the crews that were preparing

for the mountain Everest bit was destroyed.

And, of course, there was a lot of...

human suffering,

not only in the local area

where the avalanche happened,

but all through Nepal.

So the entire infrastructure

for the climbing season disappeared

and the government decided

to close the mountain that year

and no summit bits occurred.

For some communities, the threats of avalanches

are an ever-constant feature in their lives

and one they have had to adapt to over generations.

This is the case

for alpine inhabitants and communities.

Avalanches pose a greater threat to human life

and property in the Alps

than in any other region in the world.

This is due to the high population density

of the region as well as the large number

of visitors to the mountains.

There’s now a lot more development

in some of these mountain regions because

they are very attractive tourist destinations.

So tourist industry has evolved in the mountains

for skiing and mountaineering.

Like the Himalayas,

the Alps are a major attraction,

enticing an estimated tens of millions of tourists

to their slopes every year.

Emerging roughly

44 million years ago,

the Alps are the youngest mountain range in Europe.

And covering more than 207,000 square kilometers

of the landscape, they are a prominent feature

of Western Europe’s physiographic regions.

Human settlement is not

a recent phenomenon on the Alps,

with humans living amongst the towering peaks

since prehistoric times.

And with the presence of human activity,

the tragedy of avalanche disasters has followed.

In December 1916,

at the height of World War I,

more than 10,000 troops were killed

in a single-day avalanche disaster,

triggered by artillery fire on slopes of unstable snow.

The mortality rate from avalanches

has remained fairly stable over the last hundred years.

But the increase

in recreational winter activities

led to the avalanche deaths nearly doubling

in uncontrolled terrains between the 1960s and 1980s.

Between 1950 and 1951, however,

the Swiss-Austrian Alps experienced a series

of deadly and devastating avalanche events.

The extreme winter

known as the "Winter of Terror,"

saw 650 avalanches strike the region

over a three-month period.

High precipitation and strong winds

led to the heavy snowfall piling up on slopes,

till the weak layers gave way and collapsed.

The winter report

from the Institute for Snow and Avalanche Research

documented and described

the events of that terrifying winter.

The report describes the rolling and crashing sound

of the descending avalanche.

It also describes the darkness that covered a village

as well as the destroyed houses and homes

which tragically became graveyards for entire families.

Several villages and thousands of acres

of forest were obliterated.

If you think about an avalanche as it picks up speed,

it also creates friction and that generates heat,

and with the heat you can have melting of the ice granules

and they form these icy blocks or these boulders.

And that makes it very dangerous

because it’s not the fluffy white stuff anymore,

It’s actually hard big chunks

that can really damage structures or hurt people.

In Switzerland,

1000 buildings were destroyed.

At the village of Vals in Switzerland,

the deadliest single event of the winter killed 19 people.

In total, 265 people in Austria and Switzerland

lost their lives in the disasters.

It was one of the greatest human tragedies

the nation had experienced since the World Wars.

But there were important lessons

around avalanche safeguarding

learnt from these tragic events.

In 1953, major safety measures were implemented in the region.

These included the implementation

of effective avalanche barriers,

as well as the use of hazard maps

and the expansion of forecasts

by the Institute for Snow and Avalanche Research.

These improvements would play a significant role

in minimizing the number of fatalities

in a similar major avalanche disaster in 1999.

In some areas above settlements

where you know where the risk is

and you know where the exposure is

then structures can be built in the mountains,

so fences high in the mountains

in the initiation zone of avalanches

to prevent them from sliding in the first place,

or large structures rather like dams

that could divert avalanches once they have started.

The 1999 Galtur disaster

was the worst avalanche to strike the Alps in 30 years.

On February 23rd of that year, a series of massive avalanches

hit the Austrian alpine village of Galtur.

In just a couple of minutes,

the tiny village was overwhelmed

and buried in towering walls of snow.

It was terrible.

What happened? It was terrible!

The avalanches, labeled by some newspapers

as "the white deaths," caused severe damage.

Thirty-one people were killed,

26 of whom were tourists

and five who were locals.

Many more were injured.

It’s almost a mountain that came down.

It’s incredible.

One moment, you’ll see nothing,

you’ll hear nothing and then I get no more air.

After the avalanche, it had gone, it was silent.

We saw some light shining, some daylight.

We opened the window, and as we were in the basement,

we were safe because the rest of the house,

all the floors just had vanished.

So it’s a fundamental question,

if we can have this mass tourism growing.

Ski resorts in the region were shut down.

This was a huge blow to the resort industry,

costing more than $6.5 million for each day of closure.

The avalanche was the biggest human tragedy

the Alps had witnessed since the 1951 disaster.

But the snow fences and avalanche protections

put in place since 1953

helped minimize

the number of fatalities.

And rescue workers managed to save 26 people

in the 24 hours following the disaster.

We are here now already for 60 hours

and I sleep for four hours.

I’m a psychologist and I’m going to Galtur

and this is my own dog and he has a good taste

and perhaps also my dog can help

and perhaps he can find somebody there.

However, the occurrence of the avalanche itself

in the village was a scientific mystery.

Galtur was

a popular mountain village,

known as a winter sports destination,

and although minor avalanches

were a frequent occurrence in the region,

they would never usually reach the village.

This was due to the fact

that Galtur was located in the Green zone,

designated an avalanche-safe zone.

And yet, paradoxically, it was this exact area

that had experienced the most significant avalanche damage.

Nature can do strange things.

There are certain areas where we know avalanches occur

but then patterns change, weather patterns change.

Climate is changing, and therefore,

our historical records may not be accurate anymore

and our predictions where there are dangerous areas

may not be correct either.

Scientists got to work

investigating the event

and pointed to a number of weather phenomena

preceding the avalanche.

Throughout February 1999,

three massive weather fronts

had caused the largest deposits of snow ever recorded

to amass on the mountain.

The strong winds piled up the snow

into even deeper drifts.

Deep below, the melt crust supported

an ever-increasing weight of snow.

Finally, the crust collapsed,

giving way for the snow mass

to come crashing down the mountain.

The resulting disaster would impact the region

for many years to come

and change future understanding

of avalanche events.

Avalanches are inevitable.

There are millions of avalanches

that happen every year across the world.

Most of them cause no trouble

and kill nobody and destroy nothing.

But what’s dangerous is when people go into places

that are threatened by avalanches.

In Europe, things are very well organized.

Areas are being divided

into green, yellow and red areas.

The red areas, you’re not allowed

to build any structures.

In the yellow areas, you can build structures

but they need to be reinforced.

And in the green areas you can build anything.

And this is instigated by the local government

or the national government even.

And so people need to abide by those rules.

The main way to prevent avalanches from causing trouble

and killing people and destroying property

is just not to build things

in the places that are threatened.

The disaster events on the Alps and Mount Everest

are tragic reminders of just how devastating

and deadly avalanches can be.

Yet as Professor Ian Stewart has noted,

we still know less about them

than we do the surface of the moon.

A process known as artificial triggering

has been offering an increasing insight

into the workings of avalanches.

Artificial triggering is the practice

of initiating avalanches

through controlled explosions

in order to safeguard against possible starting zones,

and prevent larger-scale avalanche events,

which could pose a danger to the public.

Artificial triggering of avalanches is generally done

using explosives which could be dropped out of a helicopter.

It could be simply tossed by hand onto a slope

by ski patrollers traveling at the top of the slope

or artillery shells could be fired at the slope

to trigger the avalanche.

Switzerland has been using artificial triggering

for many years as a means of mitigating

avalanche disasters in its Alps

and protecting its communities,

transport links

and winter sports resorts.

So in a ski resort, if there’s been a lot of fresh snow

or they think the risk has gone up,

then they’ll go out and they’ll blast anywhere

that they think an avalanche might occur.

So that will either trigger an avalanche

or if it doesn’t trigger an avalanche

then they’ll think probably the slope is safe.

So that often happens early in the morning

before they open the lifts.

There are numerous methods

employed to set off a controlled avalanches event.

These include hand

and manually-charged deliveries...

helicopter drop-off of charges,

as well as permanently installed triggering devices.

Permanently installed devices are increasingly used

due to their relative safety.

In comparison

with manual and helicopter detonations,

these devices allow for remote operating

and remove the need of a human presence in proximity

to the hazards of a detonation zone.

An example of these devices is the Gazex,

an explosive tube containing an oxygen-propane gas mixture

that can be remotely triggered to start an avalanche.

As well as offering increased safety,

the devices have proved efficient.

The devices create slab-type avalanches

by effectively making fractures

in the weaker snowpack layer

and thereby creating a starting zone.

In Switzerland, there are a few hundred

such preventative systems that have been set up.

But the choice of triggering method

is very much dependent

on the specific topographical need

of each individual peak as well as costs.

Artificial triggering can improve safety

and save lives in many different ways.

The primary thing is that when you’re triggering,

you keep people out of the way.

The other thing is that

if an avalanche doesn’t get triggered

then you can decide the slope is safe

and people can go back in.

And also, it can prevent too much snow building up

so it might be a spot

that threatens a town or something

and then if you let the snow build up

it could be a really big avalanche that would hit it.

The control

and proximity to avalanches

offered by artificial triggering

is being harnessed by scientists

to enable better understanding of these snow events.

Artificial triggering systems

along with technology-driven warning devices

and reinforced buildings may be

effective preventative measures for avalanches,

but they are not cheap nor always safe.

For avalanche-prone regions

in low and middle-income countries

such as Nepal and India,

these measures may not be the most cost effective

nor sustainable options

to deal with this natural event.

Mountain forests, age-old natural barriers

used in Alpine regions,

are increasingly being offered as cost-effective

and efficient protection

against avalanches and rockfalls.

Now it’s recognized that

forests can be really important

for preventing avalanches from happening.

So there’s a big effort

to reforest a lot of areas of the Alps.

And if you plant a forest

in an avalanche starting zone

this can stop them happening.

If it’s lower down the mountain,

they can also stop smaller avalanches

but they won’t stop a really big one.

So the main use of forest

is to prevent avalanches from happening

rather than to protect from them directly.

With treetops equalizing temperature and wind conditions

as well as giving stability on mountainsides,

forests could be described

as nature’s perfect blanket against avalanches.

However, natural phenomena such as storms or wildfires

can put these forests at risk.

Deforestation, climate change and global warming pressures

are also impacting on mountain forests

and any protection they may offer in future.

Some scientists have theorized that warming temperatures

and climate changes could also be behind

avalanche disasters on Everest,

regions which might potentially benefit

from the use of mountain forests.

But all mountain ranges have diverse topography

and not all regions are suited or capable

of sustaining forests in a similar way to the Alps.

For now, there is no individual solution

to combat the unpredictable force of avalanches.

And until we can find

more cost-effective and accurate methods

of tracking their trajectory,

they will continue to be

one of nature’s most unpredictable killers.