- I'm buried under two meters of snow
somewhere in the backcountry.
If I can't get out of here in the next 10 minutes,
then chances are I'm never going to escape.
In what may be our final episode of "Atomic Frontier,"
just how do you survive an avalanche?
(dramatic music)
In order for us to properly understand how avalanches work,
we first need to appreciate what they're made of,
and what better way to do that
than with a little bit of downhill skiing.
Snow requires two things in order to form:
low temperatures and high humidity.
Unfortunately, very cold air
can't hold all that much moisture,
which means that at times
it can literally be too cold to snow.
Because of that, snow clouds will often form in regions
where we have a mixing of both the warm, wet air,
as well as the cold, dry air.
We get that around large lakes,
in places where we have cold fronts,
and also where we have mountains
pushing up the warmer wet air
in order to mix with this cooler dry stuff we have up here.
With these ingredients
and a bit of encouragement from atmospheric dust,
a winter wonderland is sure to follow.
Snow by itself is fine,
but once it starts piling up, forming layers,
we get some serious problems.
To find out how this works,
I'm going to need to do some digging.
After nearly an hour of digging
with no help from the cameraman,
I've made it to the bottom of a hole.
From where we started,
we've since descended about 1.3 meters.
Along the way, we can notice various layers of snow
culminating in the ground at the very bottom.
As we descend, the snow changes in a few of its properties.
Near the top, it's relatively soft.
As we descend, it slowly becomes more and more firm,
eventually becoming near impenetrable near the bottom.
The reason for this is that while snowflakes fall
as delicate flakes,
they don't stay that way for very long.
Soon, their arms get snapped off
and cohesively bond with their neighbors
in order to form a much more strongly packed structure.
This process is known as sintering.
The lower layers are more densely packed
because there's just more pressure pushing down on them
and more time for the sintering process to occur.
One layer of snow which doesn't follow that trend
is this one.
It seems to be all flaky, just falling apart in my fingers.
This is called depth hoar
and is the reason why avalanches can be so devastating.
It's caused by the difference in temperature
between air pockets near the warm, insulated ground
and those near the much colder exposed surface.
Warm air holds more moisture than cooler air
and this extra water vapor rapidly diffuses upward.
Along the way, rougher surfaces
will preferentially accept the vapor,
over time reforming our sintered snow
into flat hexagonal crystals.
If the local temperature gradient is big enough,
then you are able
to completely reverse the sintering process,
forming an uncharacteristically weak layer of depth hoar.
Ski patrol will often dig holes much like this one,
taking temperature measurements
in order to build a profile
and work out where depth hoar is most likely to form.
But this layer is often pretty deep.
So why do we need to worry about it?
To find out, and to allow me to warm up a bit,
I'm gonna go inside to give you a demonstration.
Welcome to my custom-built avalanche simulator of doom,
otherwise known as whatever I could find in the kitchen.
Our slope is going to be represented
by a cutting board mounted onto a cardboard box.
For our different types of snow,
I've got powder snow as some flour,
the depth hoar as some sugar granules,
and, finally, the sintered, bonded snow
is going to be a sheet of pastry.
To keep with the baking theme,
a gingerbread man is going to be our skier.
Here's what our slope is meant to look like.
A strong base of sintered snow
followed by a light sprinkling of powder.
When our skier comes across it, they're pretty fine.
Now let's see what happens
when we add the layer of depth hoar
onto our regular base,
covering it with a layer of fresh powder,
some sintered snow,
and a little bit more fresh powder,
giving it the outward appearance of a regular slope.
This is a slab avalanche,
the least predictable and most deadly
of all the avalanche types.
The applied load
causes the thin layer of sintered snow to break.
The reason why depth hoar is so dangerous
is because it's this layer
which allowed the upper surface to slide down the slope,
taking the skier along for the ride.
We now know how they work,
but how can we survive one?
You're out skiing
and an avalanche is coming right towards you.
What now?
Avalanches can travel at up to 120 kilometers per hour,
so you can't outski it by going directly down the hill.
According to the Prometheus school
of running away from things,
your best chance is to go at 90 degrees to the avalanche
and try to get out of the way, perhaps to the treeline.
However, if you've got a slab avalanche,
then chances are you're already inside
that churning mass of snow.
About 25% of people who die during an avalanche
do so due to injuries sustained
by hitting trees and rocks along the way.
To survive that, you should be wearing a helmet, a backpack,
and hope that you just don't hit anything major.
The remaining 75% of fatalities occur
after the victim gets buried underneath the avalanche.
Therefore, our next priority
should be to ensure that we stay above the surface.
We do that using one of these.
It's called an airbag pack.
It works by increasing your volume,
reducing density so that you stay above the surface.
They're actually extremely effective,
even if they look a little bit ridiculous
A common misconception
is that you can somehow dig yourself out of an avalanche,
spitting to work out which way is up
and then digging in that direction.
However, this is a fundamental misunderstanding
of what post avalanche snow is like.
The energetic events of an avalanche
knock the corners of many of the snow crystals,
which allow them to sinter back into a formation
that is very much like ice.
You can barely move your fingers in this sort of snow,
let alone dig your way out.
The only option is to hang tight and hope for rescue.
In an ideal world,
we'd then have a specialist rescue team come and get you,
ideally with a nice big dog
carrying warm drinks and a bit of cider.
However, that's unlikely to get to you
in the time before you go into hypothermia
and run out of oxygen.
So the people who are actually going to rescue you
are going to be the people you're skiing with.
To help them out, we often carry one of these.
Each skier has this transmission beacon
in its transmission mode.
If someone goes missing when they get into an avalanche,
we then put it into receiver mode
and it's able to detect signals being transmitted.
In order to have a bit of fun,
I've had my camera team bury a transmitter
somewhere in this park
connected to some buried treasure.
It's my job now to use just this receiver
in order to find our missing loot.
(receiver beeping)
(receiver beeping rapidly)
At this point, I'm pretty much
as close as we're going to get
by using the proximity sensor alone.
The beeper is going a bit crazy.
Now that we know we're in roughly the right area,
I'm going to be using this slightly massive pole
in order to jab it into the ground
in a slowly increasing radius
from where we think our object might be.
Eventually, I think we hit something.
Because time is of the essence,
a shovel will really help us get to our chance victim
as quickly as possible.
With a bit of digging,
yeah, I think we found something,
a box of Weet-Bix, a true treasure.
And inside is our beacon.
The best way to survive an avalanche
is to not get into one in the first place.
But if you do, a bit of preparation
and some very cool tech go a long way,
as does having a cameraman
who actually remembers where he buried you.
This has been James Dingley from the "Atomic Frontier."
Keep looking up.
(dramatic music)
Okay, you can dig me out now.
Hello?