#piston peak

Note: Any time you see information followed by an asterisk (*), it is a reference to my own, personal WOC headcanon.

Igneous rock formation is the easiest for humans to comprehend because the basic principals--melting and freezing--are very familiar to us AND happen on time scales that our silly, monkey brains can actually understand.

Behold! An igneous rock!

In all seriousness, if not for being man-made, this horrifying Spongebob popsicle could be classified as an igneous rock!

How?

Igneous rocks form from the cooling of molten rock (called magma or lava depending on whether it is underground or above ground, respectively).

Ice, believe it or not, IS an igneous rock. This is because the ice crystals that comprise it meet all the criteria to be classified as a mineral: They are naturally occurring, inorganic, crystalline solids with definite chemical compositions. To make ice, or any other igneous rock, a molten medium must be chilled to its "freezing point." Water has a freezing point of 32 Degrees F (0 degrees C). At this temperature the movement of individual water molecules is so slow that they start bonding with other water molecules into a repeating, three-dimensional lattice which we call a crystal.

As crystals continue to form and grow at the expense of the melt, they start bumping into other crystals, fusing with them along their edges. Once all the water has been used up, we're left with a solid composed of thousands of interlocking ice crystals.

Igneous rock forms in basically the same way, except that the freezing temperature of molten rock varies between 1,100 and 2,400°F (600-1,300°C)! This is why if you ever see scientists getting close to fresh lava, they wear special, heat-resistant suits that look like they'd fit in to any 1950's era science fiction motion picture.

*Note* I'm not going to into the details of magmagenesis (the formation of magma)...it could be it's own article, tbh. Suffice to say that molten rock is only generated in very specific environments along very specific plate boundaries. Volcanoes are the surface expression of magmagenesis, and most of them can be found in a belt of tectonic activity that "rings" the Pacific ocean, hence it's colloquial name "The Ring of Fire." Most of y'all don't need to worry about a volcano popping up in your backyard...

Ok...so let's apply what we've learned so far to the World of Cars, starting with volcanism.

A "volcano" is a mountain created when "volcanic materials," such as ash and lava, pile up over a fissure in the Earth's crust. There are many different types of volcanoes, each with their own eruptive styles and geomorphology (aka physical traits).

The only actively erupting volcano we see in the WOC is the unnamed mountain in Cars on the Road Episode 1: Dino Park.

Lookit how 'dorbs it is! Such a cute, widdle guy....

Note the steep sides and "cone" shaped profile. This shape is characteristic of "stratovolcanoes," a family of volcanoes that are built from alternating layers ("strata") of hardened lava and "tephra" (fragmented rock of varying sizes). Normally the slopes aren't as steep as what's depicted here, though there are exceptions (Ol Doinyo Lengai, Goma, etc...). Compare this to the much more realistic depiction of Mt. Fuji--also a stratovolcano--in Cars 2.

Fuji's sleek and beautiful cone was built on the remains of older volcanoes over a vast swath of geologic time (the earliest eruption on record was from 12,000 BE (Before Exodus--4.12 million years B.P.*). It warms my heart--no pun intended--that the animators really did their best to convey her size and natural beauty on the digital canvas.

Evidence of Plutonic (i.e. underground) processes: Piston Peak National Park (PPNP):

PPNP was modeled VERY heavily off of an Old World landmark: Yosemite National Park. After analyzing DOZENS of screencaps, it appears that the underlying geology is comparable to Yosemite, and I headcanon that the modern V6 valley is located in approximately the same location as Yosemite, albeit different due to a combination of time, terraforming and geologic processes.*

Piston Peak National Park is located within the heart of the Sierra Nevada, a massive, 300-mile long mountain range in California.* Most of the rocks in and around the valley are classified as "granitoids" AKA granite-like igneous rocks.

Most of you may be familiar with the word "granite." Maybe your ma installed some fancy, new "granite" countertops or you were touring a building that had "granite" floors. Notice I'm using a lot of quotation marks here...mostly because the word "granite" has become something of an umbrella term that folks use whenever they encounter something made out of sparkly rock. To a geologist, the word "granite" brings to mind an igneous rock that is "coarse-grained" (its component minerals are large enough to identify without a microscope) and contains the minerals quartz, alkali feldspar and plagioclase feldspar in a specific proportion (see graph below):

So...what does the rock actually look like? Below is a sample of rock that was collected from a long-since weathered landform called Half-Dome (close to where modern-day Piston Peak is located*).

Each speck of color you see here is a different mineral: The pinks and whites are various feldspar minerals, the grey-ish white ones are quartz and the darker minerals are hornblende and biotite. And while there is no scale bar in this image, the largest black mineral is about .5-1cm long. Big enough that you can see it without a microscope. To get crystals this big, magma must cool slowly...and usually that means staying underground for 10s or 1000s to millions of years (otherwise it would cool so quickly that the mineral crystals would be microscopic).

Now that we know what type of rock we're dealing with, let's zoom out a bit and look at ancient Yosemite and it's modern equivalent, V6 Valley.*

Most all of the rock that you see in these images is granite or granodiorite. That's a hell of a lot of cooled magma, well over 100 square kilometers of it. And due to the course-grained nature of the rock, all of it should have originated as huge, underground magma chambers that cooled slowly over tens of thousands of years.

So...how did it get to the surface?

The short answer is regional uplift. Most of the solidified magma (AKA "plutons") was emplaced during the Triassic, Jurassic and Cretaceous periods. Much later, during the Neogene period, new tectonic forces caused blocks of the now mostly-solid Sierra Nevadas (and the underlying igneous rocks) to rise upward. This exposed the rocks to greater amounts of wind and water erosion. Westward-flowing streams, especially, began to carve down through the rock creating deep, v-shaped valleys. Many times these rivers cut down a LOT faster than their "tributaries" (the smaller streams that flow into a larger one), creating "hanging valleys" and waterfalls. The waterfall at Augerin Canyon is an excellent example.

Other interesting features:

Desquamation (essentially, "removing or loss of scales"):

Remember how all this rock used to be deep underground? Once all of the overlying rock and sediment (collectively "overburden") was removed, the rocks were exposed to surface pressures, and began to to depressurize, breaking along curved fractures, creating an onion-skin like appearance to many exposed rock surfaces.

Image above: Desquamation on granite in Ancient Yosemite.*

Images above: Desquamation on modern Canopy Dome, Piston Peak and on the canyon walls near the park entrance!

Bonus Cabbie butt for...aesthetic reasons.

*Bonus geology--not igneous related*

Another thing you'll also notice in PPNP is that large swaths of rock appear to have been smoothed out. While you could chalk this up to animators not having the time/budget to render "accurate" rock texture, this type of erosion is VERY common in mountainous areas that have been affected by glaciers. A "Glacier" is channelized ice that flows downhill under its own weight. As the ice descends, it picks up sediment, everything from boulders to clay, and then drags it over the topography. Rugged crags are rounded or carved into sharp blades or spires (if they weren't covered), and v-shaped canyons and valleys take on U-shaped profiles (check out the group shot below).

I'm certain that if we zoomed in on some of the exposed rock, we'd also see "glacial striations" and/or "glacial polish," where the rock was scratched and/or polished by the sediment laden ice.

There's also some cool, structural stuff going on elsewhere in the park (Thunderbolt Bluffs and Rail Ridge...), but we'll discuss them in a future essay.

Ok, back to igneous stuffs...

Hot springs and Geysers:

Hot springs and geysers (collectively called "geothermal" features), are manifestations of volcanic activity. They form when groundwater, heated by magma or hot rock deep under ground, reaches the surface. A geyser differs from a hot spring in that the heated water flashes to steam and explodes upward in a stunning spray of steam and mist. Gasket Geyser is one such example.

The only feature in the park that appears out of place is Piston Peak, itself.

Piston Peak is a combination of two, different geologic landforms: a "hoodoo" and an "arch." Unfortunately, these delicate features require specific conditions to form: Variation in rock type (usually layered, sedimentary rock) and minimal moisture. The rocks in and around V6 valley are similar enough, compositionally and structurally, that they erode in a more uniform way compared to, say, the rocks in Monument Valley. Furthermore, there's quite a bit of water present in PPNP, flowing as rivers, and falling as rain or snow. Ice that forms within a crack or fracture can actually wedge the rock apart over long periods of time, a process called "frost wedging." Combined with desquamation, and Piston Peak should have been reduced to a pile of rubble within a few centuries. The same holds true for the arches inside Augerin Canyon (below). They're simply much too delicate to exist in a climate with severe winters that can dump as much as 15' of snow during a single event.

It is possible that these features were carved from existing features to accent their natural shapes, but since we don't have any canon evidence for that, such an assumption falls withing the realm of conjecture/headcanon.

That's all I got for now. Stay tuned for WOC Geology Part 3: Sedimentary Rocks.

Cheers!