#read hte psot and learn something enw cmon

[flying-potato2]

Plate Tectonics With Grain!

Nearly everyone knows the the earth is made of layers (like an onion, or an ogre) and that we live on the crust, the outermost layer. But very few people understand the magicly and wizardry behind the formation, destruction, and recreation of the crust.

So Let's Get Started :)

The earth's crust is composed of big funky dudes called plates. These are major slabs of rock that have well defined boundaries where they meet other slabs of rock.

These plates all like to push and shove against each other, and sometimes they gang up into cool lil creations called supercontinents.

but before we get to the cool fun epic stuff, two things must be established:

Plate types

Plate boundaries

First, plate types. There are two major types of plates:

continental

oceanic

Continental plates (more commonly called continental crust) are what make up continents and large landmasses. They are generally less dense than oceanic plates and are made mostly of the epic rocks you know as granite and andesite, with sedimentary sandy rocks on top.

Oceanic plates (or crust) are generally denser and made of darker, heavier rocks like basalt. Continental plates, because of their lower density, float higher than oceanic plates on the spicy mantle. this allows them to create landmasses where oceanic crust cannot.

Secondly, plate boundaries. There are three kinds of boundaries that can form where plates meet:

a convergent boundary

a divergent boundary

and a transform boundary

A convergent boundary is where two plates violently collide with each other, usually with one plate sliding under the other into the mantle, where it violently melts into molten magma lava rock. This causes the plate that is above to bunch up like when you ram two flatish slabs of clay into each other on a flat surface, forming mountains in the process. A great example of this type of boundary is on the American west coast, where the pacific plate subducts (goes under) the north american one. This is what drives the formation of the Rocky mountains that run north-south along the entire pacific coast, as well as what causes the increased geologic activity along that coast (earthquakes and volcanoes). Such boundaries tend to occur between continental and oceanic crust, because the oceanic crust usually goes down into the mantle because it's denser than the continental stuff. Funny enough, once it's sorta melted in the mantle it floats back up as granite and adds to the continental crust. Anyway, these also like to form big underwater trenches where the seafloor subducts and is why the Mariana Trench exists.

A diverging boundary is the exact opposite, where two plates are sliding apart under pressure from the mantle, where fresh magma pours out and cools into freshly baked igneous rock seafloor. This is (to my knowledge, feel free to fact check) what causes phenomena like the east african rift valley and mid-atlantic ridge. Generally such divergent zones will have a trench or a ridge along the fault line and can be some of the places where the crust is the thinnest on earth. The diverging plates will push other plates in turn, and cause the formation of convergent boundaries. due to the rising hot stuff (spicy rocks) from where the plates are pulling apart, new oceanic crust is usually formed because the fresh magma pours out from below.

The final type of boundary is a transform line (not related to the geometric function of taking a shape and moving it to a different space on a coordinate plane), which is responsible for most silly little majorly devastating tiny little silly earthquakes like the very recent one in Turkey. Such boundaries are places where crust is not created (like in divergent boundaries) or destroyed (in convergent boundaries). Instead, plates slide past each other in opposite directions. Structures built on top of such a boundary would slowly split down the line, as one side is dragged in one direction and the other is carried in the opposite direction. One of the most well-known examples of such a boundary is the San Andreas fault line, off the coast of California.

With the types of boundaries covered, it's now very very important to understand how oceanic and continental crusts are created. Oceanic crust is formed at divergent boundaries, where new magma can rise up and solidify into the igneous rocks that form the seafloor. these rocks are then slowly pushed towards continental plates, which subduct them back into the mantle to be melted again. This time around, they are pushed up into the continental crust and cool there, turning into granite and other metamorphic rocks. This is then weathered down back into sand and sent into the ocean or plains, where eventually it might find itself as a sedimentary rock until it can be carried all the way back to the mantle.

As for how continents move and collide, it actually relies on the same force that creates the ocean currents and jet streams. like boats on a strong current, the plates move based on the convective motion of the mantle. They rely on the coriolis effect, convection, and even the gravitational pull of the sun and moon to move as well as pressure from the new seafloor at divergent boundaries, and they essentially act as a giant jigsaw puzzle of stones and spicy rocks. The movement of magma within the mantle carries the plates around, and they can then crash into, slide past, or move away from each other. Below is a helpful diagram:

Plate tectonics are visible nearly everywhere you go, in the coastlines of continents to the mountains you might aspire to climb. A lot of geology relies on plate tectonics turning up old rock layers like they have in the massive formations of rocky mountain national park or in the east African rift valley, where much of human evolution can be found in the fossil record.

The East African Rift Valley, which is the result of diverging continental plates

The Pacific Ring Of Fire, which is the result of converging plates

The Himalaya Mountains, the result of converging plates

The Rocky Mountains, see above

The Andes Mountains, see above

The Atlas mountains, see above

The Alps, see above

The Mediterranean, same(ish) reason as the alps, just with the caveat of being formed by the drifting of the African plate closing in the Arabian peninsula through the oligocene and miocene periods.

The Japanese archipelago, again from plate subduction (pacific ring of fire)

Fun fact actually, what happened with the Himalayan Mountains is pretty unique when it comes to plate tectonics, since they weren't formed by subduction or divergence. See, they were formed by the Indian and Asian plates colliding some 40 million years ago, but both plates had more or less the same density. This means that neither could subduct into the mantle, so instead they both began to buckle and crush the stone upwards, forming what is now the Himalayas. This is unique in that both plates began to form mountains instead of only one, and that the Himalayas are now the tallest mountains on the planet because these two massive plates came together when they did.

Final note, the Hawai’ian islands as well as a few other are not formed along plate boundaries. They are formed through a different phenomenon called Hotspots. This is when a jet of ridiculously hot magma is shot up through  the seafloor and ocean to make new islands. the plate then moves while the hotspot stays in the sameish spot, so the islands are formed in a line that follows the movement of the plate. This is what happened with the hawai’ian islands and probably a few others that I dont know about.

For further reading on plate tectonics check out the US National Oceanic and Atmospheric Administration(NOAA) and the US National Park Service (NPS) resources, as well as the wikipedia page if you want an in depth summary that goes into a lot more detail than me.