Overview

(gentle music) - [Joe] Deep ancient channels, so massive in scale, they can be seen from space.

Ripple marks, like something you'd typically see on a beach, but they're the size of sand dunes.

This is no ordinary river channel.

It's the scar from one of the most violent, Earth-changing events to happen in the last 20,000 years.

(static crackles) - Rolling.

- All right, here we go.

(grunting) As you might have guessed, these are not ordinary photos.

They were created by shooting lasers at our planet's surface.

This unique view of Earth's terrain lets us peer into the past of how the landscape was sculpted and shaped by massive forces.

Scientists have been piecing together that story for over a century.

But this new way of seeing into Earth's past is uncovering new secrets and it's even helping us prepare for future disasters.

(gentle music) This is the Colorado River, and the site of perhaps one of the largest floods in Texas history.

(rain pattering) July 1869.

Several days of relentless rainfall swept across northwest Texas.

As that water rushed across the state to meet the sea, the river swelled to more than 10 miles wide.

No flood in Texas since has come close to matching this unthinkable volume of water.

But today, the marks of that historic flood are invisible to the naked eye.

But scientists have developed a way of looking at the Earth which uncovers the scars of the past, using a technology called LIDAR.

This fingerprint of the Colorado River tells us its entire life story, showing how it flowed and evolved over hundreds, even thousands of years.

It uncovers hidden marks, one of the biggest floods in Texas history.

But one of the most violent and catastrophic floods in Earth's history was here in the Pacific Northwest.

(gentle music) (wind blowing) Daniel Coe is a graphics editor and cartographer with the Washington State Geological Survey.

He uses LIDAR to study the earth's surface.

- LIDAR stands for light detection and ranging or light radar, and it's a technology that uses light pulses to measure distance.

So LIDAR really allows us to visualize rivers in a new way because we can just focus on very subtle changes.

It's often collected from a small airplane flying over the land that shoots billions of light pulses down at the ground.

It measures the amount of time it takes for that light pulse to go to the ground and then back to the plane.

And that just allows us to digitally remove all the vegetation from the earth's surface as well as structures so we just see the bare ground.

And by using color to do that, it allows you to see where past channels of that river flowed.

- [Joe] Adding color not only aids our ability to see these invisible, sometimes ancient changes to the landscape, it also creates works of art.

- It really allows you to see these geologic fingerprints that these processes have left behind.

This is an excellent example here at Potholes Coulee of this giant land form that LIDAR can allow us to see in new ways.

- [Joe] Daniel is mapping the Channeled Scablands to uncover a violent history of how these huge channels were carved into the landscape.

And he's following the footsteps of a geologist who studied this landscape over 100 years ago.

- J Harlen Bretz was a science teacher in Seattle in the early 1900s, and he happened to see this new USGS map of this region that we're standing in right now, the Quincy Quadrangle.

This is actually the map that J Harlan Bretz saw that piqued his interest about these landscapes out here in the Channeled Scablands.

And it's interesting because you see this, it's a very flat landscape east of here, and then all of a sudden, there's this very steep drop off we can see behind us.

There should be something here that would've clearly caused this dramatic change in landscape, but there wasn't a clear explanation for it.

- [Joe] Bretz had a revolutionary idea for what carved these giant features into the landscape.

Around 15,000 years ago, giant ice sheets blanketed most of Canada and the Northwestern United States.

In this narrow valley, a colossal ice dam, half a mile high and 23 miles wide, ruptured, unleashing the waters of a giant inland lake: Glacial Lake Missoula.

A deluge of water equivalent to one of the Great Lakes surged across the Pacific Northwest from Idaho to the Pacific Ocean in a matter of days, a colossal ancient Megaflood, scouring the land and carving an entirely new landscape in mere hours.

But Daniel and his colleagues are uncovering new secrets about this ancient disaster that are only visible with their LIDAR technology.

- With LIDAR, it's just that next level of spatial awareness.

We can see things that would've been unimaginable to Bretz.

It's a new way of perceiving the shape of the Earth.

- Joel and I embarked on a project recently, creating some new maps of the geomorphology of the Channeled Scablands.

This area had not been covered by LIDAR data up until a few months ago.

- [Joe] The story of Earth is written in the curves and scars of its surface.

LIDAR shines literal light on this invisible past, allowing us to time travel back to one of the most destructive events in Earth's history.

- The thing that amazes me about these landscapes, the Channeled Scablands, is just how huge they are.

When you're standing here in person walking through the landscape, you really understand their scope and their scale.

- [Joe] Dry Falls is a staggering geological wonder, a remnant of an ancient waterfall that was five times wider and over two times the height of Niagara Falls.

By adding LIDAR data, we can uncover details in the massive, dry cliff face.

These huge ripple marks along the Columbia River near Trinidad, Washington, reveal the impact of enormous amounts of water rushing over the surface.

And these tiny streams hide a far more dramatic story.

Since Bretz first hypothesized these ancient floods, waters flowing from Montana, mainly Glacial Lake Missoula, were believed to be solely responsible for carving the Scablands.

But LIDAR's powerful ability to see through hidden terrain is uncovering a new twist to that story.

- It's always exciting to find a new dramatic feature on the landscape that has been there the whole time, sort of hiding in plain sight.

Geologist Skye Cooley was looking at some LIDAR in the area near Omak and found these giant current ripples.

Those were interesting because they're in the Okanagan Valley.

Prior to LIDAR, we were not aware that there were major floods that came down into the Columbia River Valley.

We can look at the spacing between the ripple crests as well as the amplitude or the height from the crest to the trough.

So not only can we say that there was a flood there, we can begin to estimate the depth and the flow velocity of that flood based on the geometry of those ripples imaged in the LIDAR data.

We now know because of the discovery of those ripples, that there were floods coming from Canada down the Okanagan Valley.

And since then, we've been finding them in other valleys as well to the north of the Channeled Scabland.

So we're starting to develop a picture of ice age flooding from multiple sources, not limited to glacial lake Missoula.

It's exciting to be some of the first people to see something about the earth, particularly features that are ancient.

The new way of seeing is incredibly exciting.

- [Joe] This is a reminder that our study of the past is never complete, and there are always new chapters to be uncovered in Earth's long and violent geologic history.

- What we're doing here in the Channeled Scabland will motivate people in other parts of the world to do the same type of geomorphic investigations.

And the more we look, I guarantee, the more we will find.

- Studying these ancient stories has another benefit.

They also give us clues about our future.

- We're now going through another deglaciation due to global climate change, and we expect the same sets of events to take place in currently ice-covered regions like Greenland and Antarctica.

So our understanding of how this ancient deglaciation process here played out informs what we should expect in the coming decades and centuries in ice-covered regions that we know are melting and changing.

- Researchers predict that climate change will put river flooding on steroids across the United States during the next century.

And because LIDAR is able to see how a river has flooded going back thousands of years, it can predict how rivers may flood in the future.

- LIDAR is often used as the base for models.

And the higher the accuracy of the topography, the higher the accuracy of your flood models.

- Predicting the effects of our changing climate is an exercise in telling the future.

But a more detailed look at Earth's past, like that we get from LIDAR, brings our possible future into clearer view.

(gentle music)