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MAN: My rappel!

MAN: Oh, my gosh, it's beautiful.

MAN: Good morning, everybody.

Woo!

Let's do it again!

MAN: Nicely done!

MAN: Oh, yeah!

Fourteen and a half.

Yes, that was awesome!

[ people cheering ] There you go, up, up... STEVE AMEN: Tonight, on Oregon Field Guide: MAN: This is my favorite place in the Gorge, right here.

We team up with geologist Scott Burns for a fun exploration of the Columbia Gorge.

- GILFILLAN: Here we are.

- BURNS: Yep, Rowena Crest.

GILFILLAN: Uhh, gorgeous!

Find out the geologic forces that created this amazing place.

MAN: I'm sure it's very interesting.

Well, it is.

Geology is always interesting.

WOMAN: It's very nice!

You know what they say: geology rocks.

But first... MAN: It's a walk down memory lane.

Remember the spectacular glacier caves at Mt.

Hood from years ago?

Well, look at them now.

How many millions of tons of ice have just ceased to exist?

MAN: In such a short order.

How could caves so massive disappear so quickly?

We return to the dangerous slopes of Mt.

Hood with scientist to find out.

In 2013, we explored a spectacular series of glacier caves here on the slopes of Mt.

Hood.

Those caves are all but gone now, while some new passages are starting to work their way up the mountain.

This all happened in just a few years' time.

Now, you might be thinking this all comes down to climate change, but as we return to Mt.

Hood, you'll see there are some surprising twists to the story.

[ ?

?? ]

MAN: High five.

- We made it.

- We made it.

MAN: This is the entrance to Snow Dragon Cave.

Eddy's axe is punched through.

What a beautiful... beautiful entrance.

ED JAHN: This is where it all started.

In 2011, a small hole in Mt.

Hood's Sandy Glacier lowered Eddy Cartaya, Brent McGregor, and a team of explorers into a world as beautiful as it was treacherous.

MAN: Okay, uh... everything's good.

The winter trip we did, if anything had happened, whoever had been injured probably would've died of exposure.

[ man exclaiming ] This is dangerous caving.

There's just no room for error.

MAN: Watch out!

Rocks!

- You okay after that?

- Yeah, I can do this.

In a series of increasingly ambitious expeditions, Eddy and Brent's team would become the first to map and fully explore not one but three distinct caves that extended more than a mile through the ice.

The largest glacier cave system in the lower 48 states had been found just 50 miles from Portland.

It's just hard to believe that there's wild places out there that nobody's stepped foot on.

But in just a few years, it would all be gone.

McGREGOR: It's a walk down memory lane.

CARTAYA: So we have a ton of coordinates kind of in this area here.

We did the surface survey of this section.

- Yeah.

- And so we had...

It was 100-plus... of ice.

Over 100 feet of ice over this thing.

In 2013, these images of Snow Dragon became the iconic symbol of the Mt.

Hood glacier caves.

Today, a thin cover of snow over bare rocks is all that's left.

CARTAYA: This is amazing.

It's just like a drained swimming pool.

It's like how many millions of tons of ice have just ceased to exist?

McGREGOR: In such a short order.

The collapse happened quickly.

This wasn't seasonal warming, this was a wholesale retreat of the glacier.

CARTAYA: You saw images of this beautiful blue tunnel and us ice-climbing a wall to get to new passages and beautiful waterfalls coming in.

If you look at that exact same spot on Earth now, there is nothing but air and an empty dirty canyon full of rocks and some residual snow.

I mean, it hasn't just changed, it's gone.

No one expected a world made of ice to remain unchanged, but the Sandy Glacier has lost a staggering 50% of its mass in just the last 100 years.

When geologist Andrew Fountain trekked to the caves in 2013, he had a bleak take on what was happening.

These giant caverns are a sign the glacier's dying?

I think so, yeah.

It'll begin to open up this kind of slot canyon going down the glacier.

So maybe next five years, ten years?

The collapse took less than two years... but why?

Was it just global warming, or was something else at play?

[ indistinct conversations ] Three years after our original journey to the mountain, Oregon Field Guide joined the expedition on Mt.

Hood once more to find out what happened.

McGREGOR: I was just dumbfounded.

I couldn't believe it.

It's a completely different story than what we came to, where we had these tubes that went for hundreds of feet, beautiful passageways, lots to look at and photograph and study, and now it feels like you're at your last leg of the cave.

The cave known as Snow Dragon is gone, as is most of Pure Imagination Cave, except for some new passages higher up the glacier.

The expedition this time includes a team of scientists from Germany.

One of our objectives is to, first thing in the morning, maybe probably just Andreas and I will go in.

If you meet us down below... Dr. Andreas Pflitsch typically studies air flow inside closed systems like caves and subways.

[ speaking in German language ] He's come to Mt.

Hood for the rare opportunity to study what's happening to the Sandy Glacier from the inside out.

[ speaking in accented English ] Just above camp is an enticing new cave opening, but a collapsing and unstable ceiling make it far too dangerous to enter.

So the team heads higher on the Sandy Glacier to look for another way in.

[ ?

?? ]

PFLITSCH: Yeah, it is exhausting, so... it's really exhausting.

It's extremely hard, but it's fun in kind of a masochistic kind of way.

About 800 feet above camp, the team spots a nasty-looking hole in the ice.

MAN: Rope!

This is how it looked in 2013 when we entered through 150-foot hole called a moulin that offered a spectacular doorway into Pure Imagination Cave.

Today the hole is wider and not as deep, but it's much trickier to find a safe way in.

[ laughing ] MAN: What we've got is three pickets.

These are used for mountaineering anchors.

You could use them vertically or you can put them horizontally.

We've got three of them set up across here.

Basically, we bury these, and it holds the rope.

CARTAYA: Andreas first, then Brent.

So you can go to the back, and you can take - the anemometer shots.

- Yep.

Yep.

Okay, I'm next?

Let's give you a check.

Buckle?

Okay.

My rope!

The descent into the opening is tricky, with overhanging ice threatening to come down at any moment in the July heat.

CARTAYA: Take it slow and carefully.

[ water rushing ] Once inside, Andreas eyes a beautiful cave large enough to house a fleet of school buses.

PFLITSCH: They look like subway tunnels here.

They are so huge!

In some ways, the new passages are as stunning as what the team found in the original Pure Imagination Cave.

While Eddy and Brent focus on exploring, the main goal of this trip is on science, and Dr. Pflitsch has brought something which has never been used here before.

It's a thermal imaging camera.

So here we see the mixing water on the walls.

It's coming... water out of the ice, which has made water which is 32 degrees cold, but the main water here is much too warm.

We are up to 40 degrees Fahrenheit.

That means this water is heated up by something.

This is a stunning find, and within minutes, Andreas locates several more hot springs inside the cave.

Yeah, I found a hot spot here in the water.

This is much warmer than the surrounding water.

You see it is up to 55.9 degree Fahrenheit.

The hot springs Dr. Pflitsch has found aren't exactly soaking temperature, but they seem to be a clue as to how these caves were created.

Then we came to this misty bend where the mist, the fog, is starting, and then we found really hot spots in the water.

In some places, the hot springs measure up to 78 degrees Fahrenheit.

It's not surprising to find hot springs on a volcano, and yet these hot springs, hidden beneath the Sandy Glacier, have never been detected before... because no one's ever looked.

[ speaking in German language ] Well, we have a lot of cavers in the world.

We have just a few climatologists who are doing cave climatology and less people who are doing ice cave climatology, but we have no people which I know who are doing glacial cave climatology.

CARTAYA: You could tell he gets excited about the data and wants to -- he said, "This is great!

We must put data loggers here and there!

This one will interact with that one, and we'll get this awesome model of the climate and what's going on inside the cave!"

And it's just really fun and exciting to see that.

Though the results are preliminary, Dr. Pflitsch thinks the warm springs may be the first domino in a sequence of events that are causing the caves to grow and then collapse unusually fast.

PFLITSCH: What is the effect of the warm water?

So the warm water flows through the cave and warms up the air above the water.

So this air is con-- is moving convectively inside the tunnel and makes the tunnel bigger because we have warm air, and this widens the cave.

So the caves are wider, so the entrances are wider.

And then more warm air can move into these wide entrances.

When we have two openings, we have a chimney effect, and sucks the warm air into the cave.

And finally, yes, there's global warming.

For decades the average snowfall across Mt.

Hood's glaciers has been offset by melting during the summer.

All of Mt.

Hood's glaciers are shrinking, and the ice is getting thinner.

CARTAYA: We're about to start a survey into a new cave that's intersected Pure Imagination.

So it's never been surveyed before, hasn't been explored.

So we're gonna just survey right on in and see where it takes us.

There is no stopping the collapse of these caves.

Station 18.

So Eddy and Brent have made it their goal to record the changes as they're happening for science and for history before it's all gone.

As you lose more and more layers of glacial thickness, it's kind of like ripping pages out of a history book.

If you imagine a history book, and every day you ripped one or two pages out, it's not that big of a loss day by day, but as time goes by, that's history you don't get anymore.

Fourteen and a half degrees elevation.

When we first started this project, our goal was to map each cave for five years.

We only got three out of Snow Dragon because it collapsed and died before we could finish.

Pure Imagination, today we finished our fifth study, but we've lost over half the cave.

This is what the cave looked like when we explored it in July 2016.

Just a few months later, this is all that was left.

One more sign that the disintegration of the Sandy Glacier is accelerating, and with consequences no one can anticipate.

McGREGOR: My idea of how these caves were going to go away and what actually happened was completely different.

I don't think I've ever had a project in my life that can remotely compare to what we're seeing up here, so I'm totally committed to staying with this and seeing it to the end.

The Columbia River Gorge has some of the most spectacular landscape in our region, and if you're anything like me, every time you drive through it, you're like, "How did that form?"

or, "Where did that come from?"

Well, we found just the right guide for a geology tour of the Gorge.

This whole thing is a result of the eruption of Mt.

Hood in 1782, and it filled up this whole valley.

See, it continues on the other side.

JULE GILFILLAN: Anyone who travels knows the best tour guides are those who love their subjects.

Where are we headed now, Scott?

So we're heading out to Chanticleer Point.

It's also called Women's Forum State Park, and...

So we were delighted when geologist Scott Burns invited us to explore his favorite subject: the Columbia River Gorge.

This is my favorite place in the Gorge, right here.

An interesting thing about the Gorge is it's a story of two major floods.

The first floods were from 14 to 16 million years ago -- all of the basalt flows coming from eastern Oregon and filling up the area where the ancestral Columbia River was.

One flow on top of another on top of another of basalt.

So right over here we've got Vista House, and that whole promontory there is one basalt flow.

One basalt flow.

The basalt flow came in and filled up totally from the bottom all the way to the top with one flow and solidified.

And that is the flow that formed this particular headland.

Scott points out an intriguing difference between the two sides of the river.

The Oregon side is straight up and down.

The Washington side is very, very low angle going up.

Flow on top of flow on top of flow of the Columbia River basalt, but the whole thing has been uplifted and then tilted to the south.

So the whole Washington side, the tilted side, is all landslide.

The Oregon side has all the waterfalls because it's straight up and down -- water comes out to the edge and comes over.

[ birds chirping ] The other story that we have here are the Missoula Floods.

Between 15- and 18,000 years ago, you had an ice dam that had formed up in northern Idaho.

And then all of a sudden that dam broke, and it took three days for all the water to leave, and then that came down through Spokane, across eastern Washington -- all that water got back into the Columbia River, and it came down the Gorge.

Scott says these floods were the greatest known to have ever occurred in North America.

And we're talking velocities coming out of the Gorge at 50 to 60 miles an hour, eroding things and big huge boulders being bounced around on the bottom.

We believe that there were 40 different floods that reached down here, and so they really had a significant effect on the Gorge.

And then way off in the distance, you can see Beacon Rock sticking up, and Beacon Rock is the heart of an old volcano.

And the Missoula Floods have really scoured it away, and so we call it a volcanic plug or a volcanic neck.

GILFILLAN: And why does that plug remain?

BURNS: Because it is very, very dense.

That's all big andesite, and it just doesn't weather very rapidly.

The other thing is, it's very young.

And it's the youngest volcano in the whole Portland area -- 55,00 years old.

And so those are some of the things that we can see.

GILFILLAN: Wow.

[ birds trilling ] Our route takes us along the old Columbia River Highway and through some pretty tight turns.

Good thing you can shoot and be in a car at the same time, Todd.

SONFLIETH: Yeah.

Let me know if you get carsick.

SONFLIETH: All right.

Yeah, we're almost through most of the hairpin curves.

Latourell Falls is pretty close.

GILFILLAN: Latourell Falls is my favorite falls.

Oh, it is special.

Well, it's got a good story.

- Oh, I can't wait to hear it.

- The geology, yeah.

I love hiking in here in the summertime -- it's just wonderful.

Latourell Falls is known for its beautiful columnar architecture, a characteristic of basalt's multifaceted structure and the way it cools.

See, this is another place where a flow has completely filled up a canyon.

Can you see the round canyon?

The lower part that we have got down here are columns.

And what happens is the flow will stop.

And when it stops, it cools from the top down and the bottom up.

And as it does that, the rock forms a big crack because it shrinks in sometimes four-, five-, six-sided shapes.

And so all up and down the Columbia Gorge, you will see these beautiful basalt columns.

We use a lot of those columns in our gardens, and it is very Northwest.

GILFILLAN: So what is going on with that patch of lichen?

BURNS: Lichen is a symbiotic relationship of algae and fungus.

So one has the house and one is the food, and so it's a marriage.

And in fact, in the whole world, this is the only marriage on the rocks that actually works.

[ Gilfillan laughs ] Surprisingly, Scott's favorite feature here at Latourell doesn't have anything to do with the falls.

So this is the rock that I wanted to show you.

It's completely different from all the other basalt.

Primarily a volcanic rock we call dacite, and this is really the dome of an old volcano from 25 million years ago.

We're just talking geology here.

MAN: I'm sure it's very interesting.

Well, it is.

Geology is always interesting.

WOMAN: It's very nice.

You know what they say: geology rocks.

[ men and women chuckle ] Our next stop takes us to another spectacular waterfall.

You know which one.

BURNS: We're at Multnomah Falls, and it is probably the most photographed place in the state of Oregon.

And this really exemplifies the geology of the Columbia Gorge, especially on the Oregon side.

You have a major waterfall.

Also you have got five to six major flows of the Columbia River basalt.

And the lower waterfall that we have right here is one flow, just filled up to that point.

Then as you go up, there are like three major flows, maybe four, and then up to the very, very top where it's really, really irregular, that's pillow basalt.

That is where the actual flow flowed into a lake that was here at that particular time.

This magnificent falls is also the site of a cautionary tale.

Back in 1995, about halfway up, just above Benson Bridge, a 400-ton piece of rock the size of a school bus broke off and fell into the plunge pool, and it was like a tsunami that went over the top of it.

We can see remnants of that on the side of the plunge pool.

So landslides and rockfall is very, very common here in the Columbia Gorge.

Next stop is going to be Cascade Locks.

What's at Cascade Locks?

The Bridge of the Gods landslide.

But it's actually a complex of a whole bunch of landslides that we have got across here.

Back in approximately the year 1450, a large landslide broke away from the peak to the left and came all the way down across the Columbia River and dammed it up.

Native Americans could cross from one side to the other side, and so they called it the Bridge of the Gods.

There wasn't an area with water flowing underneath it most likely; it was just a huge dam.

And then eventually what happened is that landslide dam broke, and all of that water went catastrophically down into Portland, probably a wall of water 50 feet high, wiping out probably many of the Native American villages that were along the river.

You can still see remnants of the landslide -- the little island that is right out in the middle of this area and then these big rocks that are sticking out.

As we travel along the Gorge... Oh, here comes the rain!

along with the change in the weather comes a change in vegetation.

And we start losing the Doug fir and western hemlock and start picking up the ponderosa pine.

And then a dramatic change in landscape.

GILFILLAN: Oh, wow.

- There's the Coyote Wall.

- BURNS: Yep, there it is.

There's the Coyote Wall.

On the Oregon side, most everything is flat, all the bedding is flat, but on the Washington side, a lot of times it's tilted.

And the reason is the whole Pacific Northwest is rotating in a clockwise manner.

Oregon for some reason is rotating as a solid block and pushing into Washington, and all of southern Washington is being scrunched, squeezed together, and the flat-lying beds are now becoming tilted.

And so when we look across the river, we can see these tilted beds.

We're about 75 miles from Portland now, but the landscape is not getting any less dramatic.

So this is where we're going to get off up here.

GILFILLAN: Okay.

We get off the interstate at Mosier and start climbing.

BURNS: So we're on the old highway, and we're heading to Tom McCall State Park and the Rowena Overlook.

GILFILLAN: Wow.

BURNS: Yes, this valley here is just unbelievable.

- GILFILLAN: Here we are.

- BURNS: Yep, Rowena Crest.

GILFILLAN: Uhh, gorgeous!

We've arrived at the end of the Gorge.

Here, the landscape opens up to the high desert of eastern Oregon.

BURNS: Yeah, I love it!

But this is the part of the Gorge that everybody doesn't know about.

If you look on the other side, you can see layers of the Columbia River basalt.

And in fact you go up the slope, and then all of a sudden you lose them, and you have just nice smooth rounded hills that are up there -- that's windblown silt.

And so it tells us how high the Missoula Floods got.

And then as you start looking at those Columbia River basalt flows, one on top of another, you go down, and all of a sudden, the flows are going like this.

And then on the other side, they're flat again.

What's going on there?

Well, that's a fault.

And so originally you had rocks like this, and then if you pushed them, it goes down like this, and so you still had the flat ones on one side, but you have the other ones going down.

These dramatic angle shifts in solid rock are another example of the powerful forces that shaped the Columbia River Gorge.

If it seems like Scott knows pretty much everything about how all these features came to be, think again.

I really wanted to look down onto these surfaces down here.

GILFILLAN: Oh, okay.

BURNS: And you can really see the differences, - because the green versus tan.

- GILFILLAN: Oh, yeah!

What did those come from?

This is the mysterious part of this whole thing, so...

There are areas that are very, very green, and then in between, it's dry.

And if we go down to them, they're mounds, and they're called mima mounds.

What caused them?

For many, many years we thought it's freeze/thaw processes, but then all the specialists from around the world got together, and they basically said, "Eh, no.

We don't like that."

One of the current things is that the gophers caused them.

I'm a believer in the earthquake hypothesis.

If you take a piece of plywood, put sand all over it, and then hit it, what will happen is the sand will go into a whole bunch of little piles.

And if you take this hard surface and have a big earthquake, what will happen is those loose sediments will form into piles.

Whatever the hypothesis is of the day, they're intriguing, and that's another interesting story that we have in the area.

- And still a mystery.

- It's still a mystery.

AMEN: If you would like to see any of these stories again or want more information, please visit our website.

And for a more behind-the-scenes look, you'll find us on Facebook.

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