Geology of the Western United States,
With emphasis on Tectonics, Basin and Range
And Suspect Terraines
The following is based on a conversation/lecture? Ozymandias and I had while traveling through the desert, he thought I should share.
I was a science nerd from about 6 years old, Apollo and such, then we had a big earthquake in ’71 and I asked “WTF?” and added Geology to my bag of tricks. Astronomy, chemistry, electricity, all fun things but this Earth stuff was very cool.
At the time, that would be the early ‘70s, plate tectonics was not quite accepted in the science world, and it had been roundly criticized when the idea was first broached in 1912 by Alfred Wegener (others came before him, but he was the loudest) and then was “cancelled” by the scientific community for his troubles.
In the glorious 1960s we were going places, the moon, into the micro realms of quanta, electronics and submersibles. Taking these minisubs waaaay down in the Atlantic Ocean we found something curious, the seafloor was erupting with lava and spreading, this gave geologists a lot of evidence for the actual mechanism behind Continental Drift.
Next came satellites and sensors, that’s when we could begin to map the seafloor and lo and behold, we found a series of ridges to the east and the west, proving the expansion of the Atlantic Ocean, now we are getting somewhere..but where?
The west coast of the continental plate is actually subsuming the Pacific plate, and the heavier, basaltic Pacific plate rides down under the continental plate. This does two things, one, the plates enter the asthenosphere, which is below the crust, and sections melt as chunks of stuff; and two, the entire region is uplifted by the extra volume, creating basins, now we are getting somewhere.
Believe it or not, the Rocky Mountains are only about 85 million years old, this iteration, truth is, they have grown and eroded several times, again due to two things, constant uplift by the Pacific plate melting under the continental plate, and the fact that granite is lighter than basalt. Basalt is the real dark rocks you may see, and granite has big crystals in black, grey and blue, like a polished counter top. That doesn’t stop water and wind, so the Rockies have been built up and worn down many times, hence the wonderful soil of the Midwest, that’s for the next part…