How did Lava help form the Columbia Plateau?

How Lava Flows REALLY Made the Columbia Plateau

Ever stood in the middle of Washington, Oregon, or Idaho and just felt…small? Awe-struck? Well, you might have been standing on the Columbia Plateau, a landscape forged by some seriously epic volcanic events. Forget your typical cone-shaped volcanoes; this was a whole different ballgame. We’re talking about a lava deluge of truly biblical proportions.

This wasn’t your garden-variety eruption; it was a series of flood basalt eruptions, a geological saga that unfolded between 17 and 6 million years ago. Think of it as nature hitting the “reset” button on a massive chunk of the Pacific Northwest. These eruptions, collectively known as the Columbia River Basalt Group (CRBG), didn’t just tweak the scenery; they completely rewrote it.

So, what exactly is a flood basalt eruption? Imagine cracks – huge, miles-long fissures – opening up in the earth, and instead of explosive bursts, you get rivers of molten rock just pouring out. That’s basically it. These weren’t dainty trickles either; we’re talking about over 300 individual lava flows, each one a potential landscape-altering event. Geologists believe a mantle plume, similar to the one simmering beneath Yellowstone, fueled this molten mayhem.

Now, picture this happening not just once, but over and over again, for millions of years. The most intense period was between 17 and 14 million years ago. I mean, can you even wrap your head around that timescale? It’s mind-boggling! During this peak, lava flows occurred roughly every 10,000 years. Later on, the eruptions became less frequent, spaced hundreds of thousands of years apart. The Grande Ronde Basalt, the heavyweight champion of these flows, accounts for a whopping 72% of the total volume. It erupted for around 400,000 years!

Over those millions of years, layer upon layer of lava spread across the region, eventually piling up to over 6,000 feet thick in some spots. That’s taller than some mountains! All that weight did a number on the Earth’s crust, causing it to sink gradually. This sinking action created the vast, slightly depressed plain we now call the Columbia Basin, or Columbia River Plateau.

The lava flows even played a role in rerouting the Columbia River itself. As the molten rock advanced, it filled valleys, creating natural dams and forming lakes. These ancient lakebeds are like time capsules, preserving fossil leaf impressions, petrified wood, and even the bones of ancient animals. It’s like nature’s own museum, buried beneath layers of basalt. And the river? Well, it was forced to find a new path, carving out the course we see today.

The Columbia River Basalt Group is made up of seven major formations, each with its own unique story to tell: Steens Basalt, Imnaha Basalt, Grande Ronde Basalt, Picture Gorge Basalt, Prineville Basalt, Wanapum Basalt, and Saddle Mountains Basalt. These formations are further divided into members and flows, each identifiable by its chemical fingerprint, physical appearance, and magnetic properties. It’s like a geological family tree, with each branch telling a part of the story.

One of the coolest features you’ll see in the basalt flows is columnar jointing. As the lava cooled, it contracted and fractured, forming these amazing six-sided columns. You can see them in cliffs and pillars all over the plateau. It’s like nature’s own art installation!

Today, the Columbia Plateau covers a massive area – around 63,000 square miles! It’s a landscape of seemingly endless flatlands, punctuated by deep river canyons and incredibly fertile farmland. And let’s not forget the Missoula Floods, which added another layer to the story, carving out the Channeled Scablands at the end of the last ice age.

The Columbia Plateau is more than just a pretty landscape; it’s a testament to the raw power of volcanic activity. It’s a place where you can literally stand on the solidified remains of ancient lava flows and imagine the earth-shattering events that shaped the world we know. So, next time you’re out that way, take a moment to appreciate the incredible forces that created this unique and fascinating region. You might just feel a little bit smaller, and a whole lot more awestruck.