Felsic rock was rare on Young Earth. It formed in the process of differentiation. As the molten surface of the Earth solidified, it "froze" in stages because different components of the rock have a different "freezing point". Just as the dark, iron rich minerals of granite crystallize first from magma, then feldspar, and last quartz, silica rich minerals like those that make up granite tend to separate from basaltic minerals like olivine as they solidify and, because they are less dense, they float on top of the basalt.
So every time oceanic crust melts and rehardens (part of what geologists call the "rock cycle"), a little more continental crust precipitates out.
I hate seeing the foamy sludge that collects on urban streams but, conversely, the way it floats on the water is entrancing and educational. It seems to try to stay in place while the water moves under it. Eventually, the foam will be washed downstream but, until it does, it piles up behind obstacles, even if the water pours over them. It swirls around in whirlpools. It's so buoyant, and rides so high on the surface that the water doesn't have much to push against.
And that's the way continental crust rides on oceanic crust. Early chunks of continental crust tended to hang around forming the cores of landmasses. They persist even today. Geologists call them "cratons".
Just like rafts of foam tend to collide to form larger masses of foam on streams, and then break apart to forms smaller islands, these cratons collide to form "supercontinents" and then break apart as smaller pieces float away on the oceanic crust to form smaller, individual continents.
This "tectonic plate theory", the idea that the Earth's crust is broken up into rocky plates that move around, was a little hard for scientists to swallow when Alfred Wegener, a meteorologist, first proposed it in 1915. In fact, he was treated sorta badly by the geological community. After all, what would it take to break the crust apart and where was the evidence of such a stupendous force?
Of course, it turned out that Wegener was right. You can see the force if you cook. If you start heating a liquid, it will stay quiet for a while, but then you will notice that the surface becomes bumpy before the liquid begins to boil. The bumps are the tops of convection currents in the fluid. The bottom of the pot is hotter than the surface of the fluid and hot materials are less dense than cooler materials. The less dense liquid rises through the cooler fluid and, when it cools at the surface, sinks again to create currents up and down throughout the liquid.
The Earth has layers. The top part of the crust is relatively cool and solid, but the bottom part is, at least, plastic with pockets of molten magma. If you travel into the Earth's interior, you would find that the deeper you go, the hotter it gets. Materials under pressure get hot but there is another thing that fires Earth's inner furnaces. The heavier an element is (meaning, the larger an element's nucleus is and the more protons and neutrons are there) the more unstable it is and, when it breaks apart, it gets hot. You know where the heavier elements went when the Earth formed...straight to the center. The Earth is a nuclear furnace.
The top part of the mantle, the layer beneath the crust, is also plastic. The plastic layers of the Earth's crust and mantle are known as the asthenosphere. The crust floats on the asthenosphere. Deeper layers of the mantle and the outer part of the core are molten, liquid rock. Like a pot of hot broth, the inner part of the Earth has convection currents. If you can imagine crackers floating on boiling broth or a film on the surface of gravy, you should be able to imagine why Earth's crust is broken apart.
There have been at least five supercontinents on Earth. Columbia (aka Nuna) formed around 1.8 billion years ago and broke apart about 1.3 billion years ago. Rodinia lasted from 1,130 million years ago to 750 million years ago. Pannotia stayed together from 633 million years to 573 million years. Gondwana lasted from 550 to 175 million years ago. The last supercontinent, Pangaea formed about 336 million years ago and broke apart about 175 million years ago
There were probably other landmasses before Colombia. The first continental crust is sometimes called "Vaalbara". Some geologist calls it a craton (continents come and go but the cratons we have now are from the original craton) and some just call it a continent. A lot of continental crust has been added on since then and Vaalbara may not have been big enough to justify the "super-" prefix
What are continents without water to surround them? Where did the water come from?
A lot of it was already here. I've said that oxygen is very reactive and doesn't like hanging around in it's elemental state. Much of it is bound with hydrogen to form water, otherwise there would be no hydrogen on Earth because it's light enough to float away out into space. Early on, most of that water was trapped in rock and only came to the surface through volcanic venting. A lot of water has been added by bombardment by icy space junk.
Nature recycles. Everything is used and reprocessed to use again. Air, water, rock, plants, animals...all recycled. There's no waste.
What geologists call the rock cycle is driven by erosion and tectonic drift. The Rocky Mountains...
was preceded by flat plains and before that, the Ancestral Rocky Mountains and the current mountains are in the process of being worn down to flat plains again to be again uplifted to form another mountain chain.
The dust formed as the Rockies are ground down are carried by streams like the Colorado, South Platte, Arkansas, and Rio Grande Rivers to be packed into sand bars, dunes, and beaches where they become buried and harden to sedimentary and metamorphic rock.
There are 16 principal tectonic plates that have formed since Earth's crust fractured around 3.4 billion years ago. They're pretty much the same plates and, although most of what you see around you is continental crust, that's just what you see. It rides on a surface of oceanic crust. That's what the tectonic plates are made of. They're constantly being extruded from Earth's molten interior, typically on ocean floors, at mid-oceanic rifts, but there are places like Iceland and northeastern Africa where you can see it happening on dry land.
If land is being created at one place on the globe, it has to be un-created somewhere else. That happens at the other side of a tectonic plate at a place called the "subduction zone". There, one plate pushes under another and is melted to merge with the Earth's mantle. There, it's mixed and churned out at a rift zone to be reused as solid crust. The continents just float on top....crash together...tear apart...like a crust over a pot of boiling gravy.
Where was Colorado, and, thus, Walnut Hill back during Columbia's time?
It wasn't. The North American craton extended as far as Wyoming, but Colorado isn't on a craton. It's been added on since Columbia. There has been land at this latitude and longitude, but it wasn't Colorado. Also, there was still no oxygen to breathe. It was all in rust and water.
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