Climbing to the Giant Forest

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Well, okay folks, we've been in Sequoia National Park for a little while now, but we still haven't seen any sequoias. Well, that's because they just don't live down here. So, to see them, we're gonna have to climb. 

So, wave farewell to the foothills section of the park, because we're heading way, way up to the giant forest itself. Now, the road ahead gets extra twisty, so drivers, keep your eyes on the road. Now, as we check out these rockin' landscapes, why don't we talk a little bit about geology? Sequoia National Park is nestled in a mountain range called the Sierra Nevada. 

The Sierra Nevada

Now, Sierra in Spanish means mountain range, and Nevada means snowy. The entire Sierra Nevada runs about 400 miles or 644 kilometers from Southern California to the state's northern border, and it's about 100 miles or 160 kilometers wide. Now, around these parts, Sequoia's remote eastern side is home to 11 peaks that are over 14,000 feet high. 

They include Mount Whitney, the tallest mountain in the lower 48 states. Towering at over 14,500 feet, or around 4,400 meters above sea level, it's about a dozen times as tall as the Empire State Building. Whoo! Now, unfortunately, there are too many mountains in the way between here and Mount Whitney, so we're not going to be able to see it today.

The Formation of the Sierra Nevada

But, if you happen to drive around the Sierra Nevada to the other side, near the town of Lone Pine, it's a whole lot easier to see Mount Whitney. In fact, it's kind of hard to miss. All right, now that you've got the lay of the land, let's get down to the nitty-gritty.

Where did these mountains come from in the first place? I know you want to know. The answer is plate tectonics. All right, now let's see. 

Plate Tectonics 101

It's been a minute since our last geology class, and here's a refresher on the theory of plate tectonics. The top layer of the Earth is the crust, and that crust is broken up into different pieces of all shapes and sizes called plates. Those plates sit on top of the mantle, a mostly solid but malleable layer of rock, kind of like molasses, you know? Now, floating up on the top of this rocky molasses, these tectonic plates are constantly moving around and banging into each other. 

The Nevadan Orogeny

Actualist, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Now, about 200 million years ago, in the late Jurassic period, a mountain-building process called the Nevadan Orogeny got started. That's when an ancient oceanic plate called the Farallon plate was pushed under the North American plate. And when one plate gets pushed under the other, that's called subduction. 

Now, with this subduction, extreme heat and pressure melt the edge of the plate, and that forms liquid hot magma. Now, some of this magma reached the surface through volcanoes, but most of it stayed several miles underground and cooled very slowly. And that, my friends, is how we get granite. 

Yeah! You see, the Sierra Nevada is almost entirely made of granite. Think, you know, granite countertops or those shiny floors in an office building, but in the form of mountains. Yeah! The core of the Sierra Nevada is what's called a granite batholith. 

Granite Batholith

Batholith! I'll bet you can't say that word three times, huh? Well, anyway, a batholith forms underground when a bunch of globs of granitic magma combine to create one great big glob. It cools down, solidifies, and becomes one giant hunk of granite. We're talking about the size of the whole mountain range. 

400 miles long and 100 miles wide, and we don't even know how many miles deep. But when the batholith formed, it was still underground. So, you say, how did it get up here? Well, the first layers of rock above the granite slowly eroded away, one by one, until the granite was finally exposed on top. 

Glacial Influence

As far back as 40 million years ago, another tectonic movement uplifted this area. The granite shot up into the sky. I mean, you know, over millions of years, and that became the Sierra Nevada.

Now, in mountain years, even 40 million is still pretty young. You know, you gotta wonder, if 40 million is young, then when is a mountain considered to be, you know, over the hill? During their short lifespan, the Sierra Nevada has seen at least four glacial periods. Now, these glaciers made their way through the mountains very slowly, carving out the valleys and the peaks and smoothing them out as they carried away the rocks and debris. 

It's just kind of nature's way of putting on a little spit shine, you know? But actually, these mountains aren't even finished. No, they are still growing. About a millimeter each year. 

That's a twenty-fifth of an inch, which is smaller than the average grain of sand. But hey, when it comes to mountains, every millimeter counts.