Can warming of atmosphere affect plate tectonics?

Just wondering (and please point me straight there if a thread already exists).

Does a raising of global temperature affect plate tectonics? It could do this in a couple of ways:

1) The increased temperature would cause the surface of the crust to expand. Would the hetaing effect eventually penetrate deep enough into the crust to cause a generalised expansion of the tectonic plates, thereby increase pressure at plate boundaries? Only a few degrees, and only a tiny expansion, but the plates are so big the effect at the edge could be significant.

2) Extra heat in the air would cause the air to become less dense, possibly upper layers being lost to space as the atmosphere expands (??). Would this result in an overall lowering of pressure on the crust by the atmosphere? Could this ever be significant enough to affect pressures of the plates? I need to revise my physics of pressure, as I am not sure that the pressure on the ground would change at all.

Thanks for input and corrections to my physics.

Rob.

Originally posted by d60944
Does a raising of global temperature affect plate tectonics?

No. Infact, its the other way around. Plate Tectonics can be a big driver of global temperature.

1) The increased temperature would cause the surface of the crust to expand.

The atmosphere doesn't get hot enough to do that.

Would this result in an overall lowering of pressure on the crust by the atmosphere?

Even if it did it wouldn't be enough to have any effect.

Interesting ideas though.

I think that only in Antarctica, if the warming is enough to melt all the ice, it will be a change big enough to affect the tectonic plate.

Originally posted by ArMaP
I think that only in Antarctica, if the warming is enough to melt all the ice, it will be a change big enough to affect the tectonic plate.

Yes, the melting of continental glaciers, removing a great amount of weight from the continent as well as rising sea levels due to the melted water plus heat expansion of the water changing the waterlevel, putting pressure on now dry areas, could cause plate movements.

Yes! I agree with what djohnsto77 says - it is a secondary effect of increased water weight and adjustments made to accomodate same.

Originally posted by ArMaP
I think that only in Antarctica, if the warming is enough to melt all the ice, it will be a change big enough to affect the tectonic plate.

If the ice is gone, then yes, there will be a 'rebound' the land.

dl.ccc.cccd.edu...

This infact is occuring right now, in northeastern america.



When there are earthquakes there, its usually because of this rebound from the melting of the glaciers at the end of the last ice age.

it is a secondary effect of increased water weight and adjustments made to accomodate same.

The melt water doesn't have any effect on the plates. Continental Ice Sheets can compress the crust, and if they are removed, it will slowly rebound.
This doesn't effect, however, things like the rate of movement of the plates. The added water to the oceans isn't enough to increase the weight of the oceans and cause a significant effect on it.

Originally posted by Nygdan

Originally posted by d60944
Does a raising of global temperature affect plate tectonics?

No. Infact, its the other way around. Plate Tectonics can be a big driver of global temperature.

1) The increased temperature would cause the surface of the crust to expand.

The atmosphere doesn't get hot enough to do that.

If there were a sustained (I mean over centuries) higher temperature in the atmosphere, why would the crust not eventually warm up to the same temp? It is just a matter of time for the conduction to work its way.

Using these rough and ready figures:
Coefficient of Expansion ~ 10 (no idea what the correct value would be, but that seems a fair guess as it's a little less than iron and concrete, and it makes convenient maths) parts per million per degree,

Length ~ 40,000km (approx circumference of the earth)

Temp change ~ 5 degrees

Increase in length = 2km

That seems significant to me, but I have no idea how it would translate into pressure at plate boundaries.

Cheers.

Rob.

[edit on 19-11-2006 by d60944]

That would probably be 2km that would probably go into subduction zones, so there might be more activity in the Ring of Fire, but not much.