So what happens to existing continents when new supercontinent forms?

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SUMMARY

The discussion centers on the geological processes involved in the formation of supercontinents, specifically referencing the "Supercontinent cycle" as detailed in the Wikipedia article. It highlights that existing continents do not simply sink but are rearranged during the formation of new supercontinents, with some magma from the mantle contributing to the crust. The conversation also notes that continental crust is lighter than oceanic crust, which affects subduction rates. Additionally, it mentions that some crust in regions like Canada and Australia is over 4 billion years old, indicating its formation shortly after the moon's creation.

PREREQUISITES
  • Understanding of the Supercontinent cycle
  • Basic knowledge of geological processes such as subduction and crust formation
  • Familiarity with the composition and characteristics of continental and oceanic crust
  • Awareness of geological time scales, particularly regarding the age of the Earth's crust
NEXT STEPS
  • Research the mechanisms of the Supercontinent cycle in detail
  • Study the differences between continental and oceanic crust
  • Explore the geological history of ancient crust, particularly in Canada and Australia
  • Investigate the implications of mantle dynamics on crustal formation and rearrangement
USEFUL FOR

Geologists, earth science students, and anyone interested in the processes of continental formation and the history of Earth's crust will benefit from this discussion.

swampwiz
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I had always known about Pangaea, but that always begged the question of what was before; since there didn't seem to be anything before, I just presumed that the crust was monolithic (i.e., as a general adjective, not "one rock", even though that it was it is, LOL), and under the sea, and a gigantic volcano just spit out all the magma (which I presume is simply the mantle that gets spit out) that cooled into Pangaea. And indeed, this fit with the evolution of lungfish (like Tiktaalik?) 400 Mya.

But this Wikipedia article is "Supercontinent cycle" - https://en.wikipedia.org/wiki/Supercontinent_cycle - so obviously this happens with some regularity (i.e., according to one theory), and thus this begs the question of what happens to the old continents. Do they just sink into the seabed? I suppose some of the magma for the new supercontinent gets spit up on top of some of the old continents. This also begs the question that if magma is being spit up, somehow that volume of the mantle has to contract, which perhaps means that the old continents and seabed falls relative to the geocenter? I suppose that this also means that the total crust grows with each new supercontinent adding to the crust.
 
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The continents mostly just get rearranged to form a supercontinent. Continental crust is lighter than oceanic crust and rarely subducts. Some of the crust in Canada and austrlia is older than 4 billion years, ad must have formed right after the formation of the moon.
 
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