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

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

(upbeat music) (dramatic music) - This is Washington Pass in the North Cascades of northern Washington.

Towering cliffs of granite that reveal two major chapters in the development of North America's west coast.

Collisions between North America and major pieces of land out in the Pacific Ocean created two batches of granite right here at the pass.

Let's investigate.

(dramatic music) That's Liberty Bell, a famous landmark overlooking Washington Pass.

It's well known by rock climbers that come from all over to climb those steep faces of granite, similar to Yosemite National Park and the Sierra Nevada Batholith.

But there's a batholith here too.

A batholith is a vast amount of magma that was once underground in the dark, feeding volcanoes, and that red hot molten magma, the magma chamber, slowly lost its heat and turned from liquid into solid granite.

The last step with a batholith, lifting it slowly, getting it to the surface, eroding overlying material.

And right here we have a 48 million year old batholith that was once deep under the surface of the earth.

(upbeat music) If you stop at Washington Pass, and you come to this overlook, you're gonna be walking right on top of this orange bedrock, and it's the golden horn.

It's the batholith.

It's like we're walking on top of a magma chamber, but we're not walking on top of a magma chamber because the peaks behind me are thousands of feet above us.

We're in the middle of the magma chamber that fed this volcanic system 48 million years ago.

And the orange color is distinctive because of the orange minerals inside of the granite.

Potassium feldspar, ortho clays, that's the orange color.

Beautiful crystals of it.

And there's gray quartz.

There's hardly any black mineral content.

So you want a good looking granite, the golden horn batholith is full of it.

But not all of the mountain peaks on this drive are golden.

(dramatic music) But there's actually two batholiths here, not just one.

Over this shoulder is the Black Peak Batholith.

It's 90 million years old, and it's salt and pepper tonalite, which is a close cousin to granite.

The white feldspars are plagioclase feldspar.

There's a little bit of horn blend and other black minerals inside.

The mountain itself looks dark, and in the hand sample here, you can see that salt and pepper look, 90 million year old black peak.

But as we continue up the trail, and we zoom out, and we see this entire ridge here in the Okanogan-Wenatchee National Forest, we've got two mountains with the two batholiths.

Liberty Bell made out of the golden horn, 48 million year old pink granite, and this ridge above blue lake that's made out of the salt and pepper, dark colored material of the black peak.

Both batholiths in direct contact with each other in the same ridge.

(upbeat music) So yes, the battle of two granites, different colors, different minerals, different ages, one almost twice as old as the other.

But there's a story here that is incredible.

The Black Peak Batholith formed in response to a collision between North America and a huge island called Wrangellia.

The collision happened a hundred million years ago, and shortly after that collision, an incredible amount of magma welled up into the North American crust, down in California and Mexico.

That's right, that's magma that was originally 2,000 miles to the south of us.

Then that black peak started moving north, all the way up here to northern Washington by 50 million years ago, just in time for another collision, this time between North America and an oceanic plateau out in the water called Siletzia.

That collision 50 million years ago created the magma of the golden horn batholith that came up right here.

So this is an old versus young magma story, but the old magma was far traveled.

The young magma is local, and they're both from major collisions with oceanic islands long ago.

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