Would a geologically ancient world be habitable?
Assuming an earth-like planet, but with several billion more years of cooling and settling (and with no moon to create tides). I'm imagining this planet would be geographically and tectonically tedious, with most mountains worn down and the sea levels relatively even across the surface apart from a few flat islands.
My questions: Assuming the sun is still relatively consisted, Is there some reason human(like) beings wouldn't be able to inhabit said planet? As a follow-up--what would the atmosphere and weather look like?
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If the planet has reached an age where internal heat is no longer sufficient to maintain active tectonics, it will enter what is known as a "Stagnant-lid Regime".
One of the first things that happens at this point, is that the global carbon cycle grinds to a halt. Volcanism is severely reduced and ultimately extinguished, which means that carbon ceases to be recycled into the atmosphere. Within a handful of millions of years, the atmosphere of the planet will be devoid of significant carbon dioxide.
The climate of the planet will suffer a reduction in greenhouse effect due to loss of carbon dioxide, so it will be cooler that is otherwise would be, and furthermore, in the absence of carbon dioxide, photosynthesis as we know it becomes impossible. Plant life, and all life that depends on it, goes extinct.
https://en.wikipedia.org/wiki/Geodynamics_of_terrestrial_exoplanets
https://en.wikipedia.org/wiki/Lid_tectonics
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