- [Teacher] What does it mean to be curious?

For my students, curiosity creates opportunities for a bigger and brighter future.

(inspiring music) (emphatic music) (ethereal music) - That's a pretty big canyon over there, and this is a basalt ridge, but would you believe it?

There's another huge canyon right over there.

Why would you have two major canyons side by side right next door to the mighty Columbia River?

In other places in the world, you would assume that rivers slowly carved these two canyons.

That's normal.

But there were never any rivers here.

That's not what happened here.

And the story at Potholes Coulee is completely different and we need to up the level of water and energy.

(adventurous music) (spirited music) Ah, yes.

Hiking in the deserts of Central Washington.

You can smell the sage.

Doesn't get much better than this.

And this place, Potholes Coulee is a rather special place in the history of geological thought here in the Pacific Northwest.

We're not far from the Gorge Music Amphitheater, a world-famous venue, but you'd never know it here.

In the middle of these Quincy Basin agricultural fields of hay and corn, right in the middle of all of that are these gargantuan canyons, so severe in dimensions that a young geology professor, J Harlen Bretz, came up with an idea that shocked the geological community for decades.

(thrilling music) Topographic maps are works of art.

With a two-dimensional piece of paper and contour lines, they can show the map reader what a landscape looks like, even without being there, and in 1910, the Potholes topographic map was published, and a young Bretz in Seattle, Washington saw that map, having never been here, deduced that something outrageous must've taken place.

Why would you have two canyons with curved cliffs at the head of the canyons, no river in the bottom, dry plunge pools at the bottom of the cliffs?

It was the beginning, the germ of an idea of what we now know as the Ice Age floods.

Water coming directly from the Canadian ice sheet, crossing the border, thousands of years ago.

More than 15,000 years ago, this water's coming through here and carving these canyons quickly.

Start the flood quickly, end the flood quickly.

It's a outrageous hypothesis of Ice Age powerful water, not lazy rivers carving slowly.

(mystical music) But these lava flows are beautiful out here and you're looking at one flow.

I know it looks like two.

There's columns down low and there's not columns in the upper half of the cliff, but that's one lava flow for sure.

We know that the lower half is called the colonnade and those columns form from bottom to top as the lava flow cooled 16 million years ago, but what we still do not understand is the upper half.

That's called the entablature, and there's a bunch of closely spaced horizontal fractures, and sometimes they're not that horizontal.

They're chaotically arranged.

Nobody seems to have a good idea what that portion of the lava flow is telling us, but that's okay.

We can still have some mystery.

What's important here is that when we bring in the Ice Age floods and excavate to create these incredible canyons, the water needs to get ahold of the rock and get it outta here, and because this basal is precut and ready to be hauled off by vertical and horizontal cracks, that's the key to understanding how coulees this big, gargantuan canyons, are formed.

(solemn music) So, the columns, the entablature, the lava flows, the cracks.

That's definitely a big part of the story for why the Ice Age floods were able to take so much rock away, but there's more here to talk about Ice Age floods.

The locals call this Ancient Lakes and there are lakes in the floor of Potholes Coulee, but those are not ancient lakes.

A hundred years ago when Bretz was here, there was no water at the base of those cliffs.

That's irrigation water that seeped in more recently.

So, why would you have holes, deep holes that are more than a hundred feet deep at the base of each of these cliffs?

They're plunge pools, where an old waterfall during the Ice Age time was, the water was free-falling and pounding on the floor of the coulee.

But that gets us to wondering, what did that Ice Age waterfall look like?

Did it really look like Niagara Falls, and the answer is no.

That cliff is 200 feet high.

We know there was 200 feet of water coming over the cliff that had the same dimension.

What did that look like from the air?

If you're a hummingbird floating above, is that really a waterfall?

I'm not sure it is.

The visual is a slight dip, maybe some white water on this surface, but we are inundating this landscape with water.

There's way too much water to have a Niagara Falls.

So, under this kind of cloud and storm of brown water, you're plucking the columns away and creating this amazing landscape, not only in the Grand Coulee, not only in Moses Coulee, but in this place, Potholes Coulee, first studied in the 1920s by J Harlen Bretz.

(desolate music) - [Announcer] This series was made possible in part with the generous support of Pacific Science Center.