Celestia Forums

Presumably there will come a point when the oceans boil off as the sun's luminosity increases. Now as I understand it, water helps lubricate the subduction zones, so presumably the planet's plate tectonics will start to seize up. So what is likely to happen in this situation - presumably new crust formed at ridges would not get hydrated, but would the already hydrated oceanic (ok, formerly oceanic) plates stay hydrated (and thus allow subduction to continue for a while), or would the water get removed from the rocks?

In short, how far can the tectonics go once the water has been removed before it all jams up?

I've never heard any time frames specifically, but I would assume that they would seize up relatively quickly. Say, less than a million years? I have no idea how long it would take for the water to be baked out of the plates.

In the end, though, I think we would end up with a planet very similar to Venus. Not only would the evaporated oceans create a massive greenhouse effect (on top of the already enlarged Sun's influence), but the current volcanism might continue on and pump more CO2 and sulfur compounds into the atmosphere, while the crust thickens. Before the atmosphere finally gets blown out into space, Earth and Venus (former Venus, anyway) might be indistinguishable.

...John...

Presumably an Earth-like planet would go through a period of wet greenhouse atmosphere before it turned dry and Venus like. This could be quite a long phase, especially if the planet has slightly more mass than the Earth.
Because a slightly more massive Earth-like world would retain its hydrogen longer, the moist-greenhouse phase would last longer. Such a world could be very Venus like, but there might be the chance of some life surviving in the upper atmosphere. (assuming it existed beforehand)

Yeah, but that life could be destroyed if that planet's magnetic field were to fail, letting all the deadly radiation to come in.

Just because the plate motion locks surely doesnt imply core and mantle thermal processes stop. The interior is still hot so why would magnetic field fail?

scaddenp wrote:Just because the plate motion locks surely doesnt imply core and mantle thermal processes stop. The interior is still hot so why would magnetic field fail?

That's what i meant--i was talking about once the interior HAD cooled down.