4 min read

The Greatest Show on Earth

Lava flows and floods
flood scouring
Ice Age floods dramatically scooped out this canyon, cutting old stream valleys in half and leaving a series of hanging valleys high on these cliff faces, photo by David Lukas

I grew up exploring and falling deeply in love with Pacific Northwest landscapes at the intersection of two of the Earth's greatest natural events.

But it is only since moving to north-central Washington that I've come to fully appreciate the power and splendor of these two overlapping events.

What makes these events so spectacular is that they occurred over vast areas—and relatively recently—so their features are well preserved and easily observed.

Palouse Falls
Palouse Falls is one very popular landmark at the intersection of lava flows and Ice Age floods, photo by Jim Black from Pixabay

First Lava...

The first event was a series of lava flows that originated from a giant field of fissures around northeastern Oregon.

However, these were no ordinary lava flows. These lavas were remarkably fluid, so they flowed quickly and easily over vast areas, with some flows extending from eastern Oregon to the Pacific Ocean.

Columbia River basalts
Lava flows covered western Idaho, plus much of Oregon and Washington all the way to the Pacific Ocean

Over 300 different lava flows happened, one after another, for nearly 11 million years (from 17 to 6 million years ago); with each new flow being added on top of older flows, creating a distinctive landscape that looks like layered cake.

lava flows
Layered lava flows are a characteristic feature of this landscape, photo by Jim Black from Pixabay

These types of lava flows are known as "flood basalts," and while the Columbia River Basalts of the Pacific Northwest are not the largest flood basalts in the world they are the youngest, best preserved, and easiest to see from popular roads and viewpoints.

lava flows
It is so much fun to explore these mazes of cliffs, alcoves, and boulder fields, photo by David Lukas

I am deeply in love with these Columbia River Basalt formations because they form beautiful cliffs of six-shaped columns with sprawling talus fields and hidden alcoves. I have spent years of my life walking along the bases of these complex cliffs, looking for great horned owls sleeping in cracks, and admiring colorful lichens that come alive after rains.

lichens on basalt
I never tire of exploring the nooks and crannies around these basalt cliffs, photo by David Lukas

...Then Water

As if these lava flows and basalt cliffs weren't dramatic enough, the final touches came 18,000 to 15,000 years ago when the most massive floods the Earth has ever witnessed swept across this region.

These floods originated when a lobe of glacial ice extending from southern Canada into the northern United States blocked a major river in western Montana, creating an immense 3000-square-mile lake near Missoula.

At some point, the rising lake waters lifted and weakened the ice lobe so that it broke and released the entire lake in an instant. These flood waters rushed across eastern Washington then funneled down the Columbia River along the Oregon-Washington border, carving dramatic and massive canyons, channels, and cliffs in the basalt.

graphic of Missoula floods
A lobe of the Canadian ice field blocked the Clark Fork River in western Montana, creating the 3000-square-mile Lake Missoula (blue), with the path of the massive Missoula Floods shown in yellow

Each time the lake emptied, the ice lobe reformed, blocking the river again and making another lake. It is believed that this process repeated about 40 times, meaning that 40 massive floods (many of which were 400 times the volume of the Mississippi River!) repeatedly scoured and sculpted this landscape.

To get a sense of the scale of these Ice Age floods, imagine the sand bars and ripples you see on the edge of a lake being so large they can be seen from space! Photo by amar42 from Pixabay

Every feature of these floods has been documented—from ripples and sand bars, to waterfalls and channels—and you can now drive this landscape with guidebooks that describe these features in fascinating detail, which makes for an absolutely incredible, must-see road trip for nature nerds like us!

channeled scablands
Driving for hours (or days!) through this landscape while studying its complex geologic history is the ultimate road trip, photo by David Lukas


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