- [Host Joe Hanson] The Rocky mountains are famed for their beauty,
but behind that exquisite facade,
a predator lurks.
Avalanches.
Powerful and mysterious,
they are one of the most deadly natural disasters in the US.
But to avoid the big one,
you have to do something unexpected.
[blasting]
You have to start them.
[exciting techno music]
♪
- [Woman] Attention all mitigation routes, radio check.
- [Man] We got fire in 100 seconds.
We got 4 1/2 round 23.
[wind blowing]
- [Joe] This is Solitude Mountain Resort
in Northern Utah.
[exciting music]
Thousands of people are drawn here every year
by peaks that reach 10,000 feet into the sky.
They are both breathtaking and avalanche prone.
- [Ian] 60 to 75% of our terrain
at the resort is what's considered avalanche terrain.
- [Joe] For the past 27 years.
It's been Ian Reddelle's job
to make sure ski holidays don't become tragedies.
- [Ian] The most deadly avalanches are slab avalanche.
You get this crack that forms.
And then the snow starts to move down the hill
in one, like, solid block.
- [Joe] Avalanches like this can reach speeds upwards
of 80 miles per hour.
- [Ian] Those big, massive powder clouds.
Those are slab avalanches that are causing that.
And they're very destructive.
[wind blowing]
- [Joe] With several inches
of fresh fallen snow and high winds,
the avalanche danger today is high.
[exciting music]
- [Ian] Every time it snows,
we go up into our avalanche terrain.
We have to hike up there.
It's very narrow.
It's quite steep.
One false step might be the difference
of you going home in an ambulance or not.
[exciting music]
- [Joe] Sometimes the slopes need
a good strong shove to start an avalanche.
[match striking]
- [Man] Fire!
- [Joe] The best method they've found
is to use explosives.
- [Ian] Explosives produce a tremendous shockwave
[blasting]
that is able to penetrate the snow pack
and make a weak layer veil.
When that weak layer fails an avalanche happens.
[exciting music]
Our goal is to create lots and lots of small avalanches,
[blasting]
so we don't have these big avalanches.
[blasting]
If we just waited for the snow to build
and build and build - [Man] Fire!
It sets us up for disaster
[blasting]
or having more catastrophic and destructive avalanches.
[wind blowing]
- [Joe] But what makes some areas more avalanche prone?
- [Man] The angle of the slope is a major factor
and the sweet spot's right around 38 degrees
- [Joe] Slopes between 30 and 45 degrees are
at high risk of avalanche.
Slopes under 30 degrees
aren't steep enough to overcome the friction
between the snow layers
and slopes over 50 degrees are usually too steep
for the snow to accumulate.
[snow crunching]
Sometimes the slope just needs a little gentle encouragement
to avalanche.
That's what ski cutting does.
- [Man] You're pushing down the slope, giving it more force
than what you would if you were just a ski over it.
And then you get your skis straight again and keep going.
- [Joe] Don't try this on your own.
These are professionals equipped
with special avalanche gear.
- [Man] The risks that we face are very real.
If you can't make it to your safe area
then you shouldn't be doing the ski cutting
because that exposes yourself to be caught in an avalanche.
[exciting music]
- [Man] Avalanche! Avalanche!
[walkie talkie clicking]
- [Man] Your heart does not stop beating for days.
I remember thinking I did everything right.
- [Joe] Chago Rodriguez researches avalanche science
and teaches avalanche safety
and his close encounter with death in the mountains
of Argentina caused him to question everything
he thought he knew.
- [Chago] That avalanche took my confidence away.
I had to go back to the science
and try to understand what was the mistake.
If you are in an avalanche,
You made a mistake.
- [Joe] Together with Hans Peter Marshall
and a team of researchers,
he's trying to understand the root causes of avalanches.
To do this, they're researching in the back country,
remote areas outside the boundaries
of traditional ski resorts.
[exciting music]
- [Chago] There is avalanche danger.
[exciting music]
Everything might look stable
but they're pockets of instability.
- [Joe] Idaho sees hundreds to thousands
of avalanches each winter.
[snow crunching]
To look for signs of unstable snow
these researchers dig snow pits.
- [Chago] We dig a hole
from the surface all the way to the ground.
We are looking at all of the structure of the snow pack.
- [Joe] The snow pack is built like a layer cake.
Each time it snows a new layer is added.
Some layers are thick, some thin, some strong, some brittle.
When new snow falls
on top of feathery crystals, it doesn't bond well
and a weak layer is created.
Slab avalanches occur when additional weight
is added rapidly to the snow pack,
overloading, buried, weaker layers of snow.
These weak layers or facets are more brittle
and easier to break and slide.
Understanding how and where these weak layers
in the snow pack exist helps prevent disaster.
[scratching]
- [Chago] You can be on a safe area
and you only move several meters
and you entered it, then you're sunk.
How do you anticipate that?
[exciting music]
- [Joe] To solve this
the researchers are trying to develop new
and more efficient ways
to detect instability in the snow pack.
They're using technology, both on the ground
[machine whirring]
and up in space.
A new satellite being launched
in 2022 could allow scientists to actually measure
from space changes in the amount of snow on the ground.
- [Hans-Peter] We are going to start getting these maps
of snow information that we've never had before.
The new technology, what it's enabling us to do
is make measurements much quicker, more objective
and at higher resolution.
And that's teaching us something
about how these properties vary over the landscape.
[exciting music]
- [Joe] What they're learning could one day
lead to advances that will help people like Ian Reddell.
[blasting]
For now Ian and the team rely on more traditional methods.
- [Ian] The best part of the job is skiing
your favorite ski line at the resort
without having to worry about an avalanche coming
down after you.
- [Woman] Whoo!
[exciting techno music]
♪