(bright music) - Whoa, there it is.

- [Arlo] This is Mount Erebus in Antarctica.

- [Jessie] There is hot magma right pretty much beneath our feet.

- [Caitlin] The southernmost active volcano in the world.

- [Jessie] So it's this pretty hulking mass of a volcano.

It just makes you get a sense of how small you are in the grand scheme of things.

- [Arlo] It's the most extreme Antarctic Extreme.

- [Caitlin] Mount Erebus is located on Ross Island, just a few miles from the largest research station in Antarctica, McMurdo Station.

(upbeat music) - [Arlo] Almost everywhere we went, the volcano loomed over us.

- [Caitlin] Ross Island is a volcanic island made up of jagged rock, treacherous glaciers, and cracks that can be hard to find.

So, flying is the only practical way to get there.

- But that doesn't mean it's easy.

We've been delayed over and over and over again.

- We've been here two weeks trying to get this flight off.

- [Arlo] Conditions have to be perfect to fly up to Mount Erebus because we do not want to get stuck up there in bad weather.

The remnants of what can happen if we do are still visible.

- [Caitlin] How high are we now?

- [Pilot] We're at 12,000.

- [Caitlin] Almost there.

The volcano is 12 1/2 thousand feet high.

So we use canisters of oxygen to help us breathe.

- [Arlo] When I open the window to take photographs, my fingers go numb.

Extreme cold at this altitude is no joke.

- [Caitlin] At Erebus's summit is a crater billowing with gas, mostly water vapor and carbon dioxide from the volcano.

Did you see any bubbling lava?

- No bubbling lava, a lot of vapor.

- Sometimes you can spot a bubbling lava lake.

It's one of only eight volcanoes in the world that has one.

And this is one of the reasons scientists want to come here.

Today, we're landing on the flanks of the volcano with Jessie Crane, who's spent three seasons studying the volcanic gases on Mount Erebus.

Negative 30 degrees, oh my god.

This is probably the coldest weather I've ever been in in my entire life.

The first thing I notice when I get out of the helicopter, my snot is freezing.

- [Jessie] And so is your hair.

- Oh gosh, is it gonna like break off?

(laughs) - [Arlo] When I got off the helicopter, the first thing I noticed was that something wasn't right.

I felt dizzy, I started to have tunnel vision, and I was completely zoned out.

- [Caitlin] At first, I thought Arlo was just spellbound by the view or something.

It took me a little while to realize he was actually suffering from altitude sickness.

- [Arlo] I couldn't think, I was just dazed.

- [Caitlin] And we're not even at the summit where much of the science is done.

- [Jessie] It's not so bad being up there, but you have to hike another 2000 feet, uphill.

- At altitude, yeah.

- At altitude, in the cold.

So it can be pretty tough.

- [Caitlin] Turns out, getting to the crater rim can be treacherous for another reason, too.

- [Jessie] It actually has pretty regular Strombolian eruptions.

That's where a volcano just builds up some pressure on the inside and then it goes pop, and it blows a bunch of lava out the top of it.

- [Caitlin] Strombolian eruptions get their name from the Stromboli volcano in Italy, which regularly has this type of eruption.

They're relatively small eruptions, and release the pressure from inside the volcano.

But these small eruptions are also what keeps McMurdo safe, since pressure is released in small spurts instead of big disasters.

- [Jessie] It's not building up a ton of pressure so it's not like Mount St. Helens.

It's just off-gassing a little bit at a time, and you can see from looking around that it has had eruptive periods that have lava flow associated with them.

That's how the volcano was built, one lava flow at a time.

- [Caitlin] While the most visible activity is at the crater, we're actually standing right next to another scientific marvel.

(gentle music) - [Jessie] Sort of like a hollow, upside down icicle.

These are fumaroles, we call them ice towers.

- [Caitlin] Fumaroles are normal volcanic features.

On most volcanoes, like this one in Hawaii, they look just like steam seeping out of the ground.

- [Jessie] You get all of that gas, water vapor, and carbon dioxide coming up through the side of the volcano, but here, when it hits the air, that steam freezes.

- [Caitlin] These towers are fascinating because they're castles for exotic bacteria that can survive in the dark, steamy, and nutrient-poor environment.

It looks like something out of Dr. Seuss.

- [Jessie] It does look like something out of Dr. Suess.

Yeah they're crazy, and every one of them sort of has its own personality.

- [Arlo] It seems crazy that anything can live here, in these high altitude volcanic ice towers.

But it also seems pretty weird that in this land of ice, there's an active volcano.

How did this volcano come to be?

- [Jessie] We're sitting on top of a large feature called the Terror Rift.

And that's the source of the volcanism.

That's why there's magma coming up near the surface and feeding this volcano.

- [Caitlin] There's actually a rift zone that runs across Western Antarctica.

A rift is where a continent is stretching apart and thinning, which allows hot magma to come close to the surface.

That's why there's a volcano here that's emitting carbon dioxide.

No matter how cold it gets on the surface of Earth, the inside of the planet is still hot.

And that's a really good thing because many scientists think that hundreds of millions of years ago, the whole world was covered in ice.

But because volcanoes like this one continue to churn away under the ice, they finally put out enough CO2 to heat up the planet again.

So this place isn't only spectacular to visit and study today, but it's also kind of like a window into our planet's past.

- [Arlo] And for me, this was a glimpse into just how extreme the conditions can be for the scientists who come here.

Fortunately, I recovered pretty quickly once I got back in the helicopter.

(gentle music) - So we just got back from probably what was the most amazing helicopter flight of either of our lives.

- No no no.

- Our entire life.

- Not the most exciting helicopter ride of our lives.

The most exciting moment of our lives!

This is the greatest, we've peaked, this is it.

(ethereal music) (bright music)