North of Ellensburg, Washington, in the back country, plenty of orange bedrock like this.

Weird.

It's green on the inside, by the way.

You'd think that'd be enough for this episode, hiking around, but there's a whole 'nother kind of rock, granite of the Stuart Range north of here.

Orange rock.

Gray rock.

How old are they?

Why are they together?

Did they form here in Washington?

Or down south in Mexico?

Or even out in the middle of the Pacific Ocean?

This is the Stuart Range.

93 million year old granite magma chamber rock that cooled underground.

We've been hiking in this area just south of the Stuart Range in the Okanagan Wenatchee National Forest.

Great stuff.

The granite has a specific story to tell, and it's not a subduction zone Cascades story.

It's way too old for that.

More interestingly, the granite has been studied carefully for paleomagnetic signatures.

And that study, a major discovery made more than 60 years ago, tells us that that granite crystallized at 23 degrees north latitude, way down in Mexico.

And now the granite has been moved up here.

It's at 47 degrees north latitude now.

So what's the story there?

How do you get something from Mexico to northern Washington?

But there's even a more interesting twist into an earlier history with not only the 93 million year old granite, but the older orange bedrock that this granite ate its way up through.

So what's with the orange bedrock?

Seems pretty weird and rare.

And it kind of is.

And the orange is basically a rusty exterior.

These are iron rich rocks from the oceans.

If you look carefully, it's really not orange rock.

It's green.

Green waxy rock called serpentinite.

That's 162 million years old.

And there's a matching mountain made of the same 162 million year old green serpentinite down in southern Oregon in the Klamath Mountains.

So this is not a one off.

There's plenty of this stuff up and down the west coast of North America, but it's the green serpentinite that has all sorts of detail that's pretty fun.

Let's go down the mountain just for a bit, get on the trail, look at some wildflowers, and look carefully at the variety of greens of the Ingalls serpentinite.

On the trail down low, it's the same orange serpentinite, but now we get a very detailed look, a gorgeous look, at this green serpentinite.

Look at this stuff.

It's got a high ping to it.

This is an metamorphic rock that was originally igneous rock.

This was created at a spreading ridge, out in the Pacific somewhere, where the ocean crust was being created.

And high temperatures involving the hot mantle surging to the surface between two tectonic plates is preserved in this beautiful serpentinite.

It feels like snakeskin.

Serpent skin.

Serpentinite.

And all the patterns and textures.

Talk about the high temperatures and the high pressures.

When this stuff was created 162 million years ago.

Now let's zoom out and think about the whole tectonic story with the serpentinite and the granite of the Stuart Range.

So to put it all together.

We need that don't we.

We need to visualize things together.

There's a couple new wrinkles on this story that I think might work for you, but we have to think big.

The orange rock is really green rock.

We've seen that, right?

That's inside.

That's the green serpentinite.

162 million years old.

That dominates this ridge.

If we go 70 million years after that, the granite is coming up through the serpentinite.

It's invading from below.

Salt and pepper magma.

The cool thing is that there's new evidence that the ocean floor rock, serpentinite, and a volcanic arc, the granite of Mount Stewart, were both happening out in the Pacific Ocean, some sort of microcontinent or super terrain or something.

God knows where it was, but it was a party in the Pacific Ocean.

The serpentinite and the granite.

North America plows into both of them about 100 million years ago, and then these Mexican rocks worked their way north between 90 and 50 million years ago.

Earthquake by earthquake by earthquake.

Sending the stuff closer and closer to us.

Where these rocks belong today.

Serpentinite, green ocean rock.

Granite of Mount Stewart.

An intimate relationship going all the way back to the Pacific Ocean during the age of the dinosaurs.