# Does the climate have any effect on plate tectonics?

After reading the question and answer Is there any correlation between La Niña/El Niño and seismic activity?, I am wondering if there is any evidence (case studies) to suggest that longer term climatic dynamics (long term trends in seasonality, ambient temperature and pressure, such as ice ages, warm epochs) has any effect on plate tectonic dynamics (rate of plate movement, frequency of megathrust events, earthquake and volcanic eruption frequency and severity etc)?

• Could you just clarify slightly what climate time-scales you are referring to? I'm slightly mislead by the mention of La Nina events/seasonality, ambient pressure etc., and how this would link to plate tectonic motions which are on the order of centimetres per year? There is also this question: (earthscience.stackexchange.com/questions/560/…) which is along similar lines. – decvalts Nov 24 '14 at 0:00
• @decvalts have clarified the question – user889 Nov 24 '14 at 0:03
• @decvalts the 2nd paragraph of your answer would make a great start to your answer - please consider undeleting it and expanding on the second paragraph in particular. – user889 Nov 24 '14 at 0:10
• @BHF thank you for adding the tag - makes good sense! – user889 Nov 27 '14 at 7:11

According to the article Cenozoic climate change as a possible cause for the rise of the Andes, the climate could affect mountain building by altering the amount of erosion, and therefore sediment deposits, which could act as a lubricant in subduction zones. In the example given, the lack of sediment increased friction, causing "crumpling" and the building of the Andes.

Given that the climate impacts erosion, that erosion may then affect the stress loading of thrust faults, affecting the earthquake frequency and magnitude, the same as post-glacial rebound.

Isostatic rebound resulting from melting glaciers may also impact volcanics, by changing the pressures, and so lowering the melting point if the rocks. "The average melting rate is increased by about 30 times its steady state value when a 2-km-thick ice sheet melts in 1000 years." In Iceland, the melting of the glaciers at the end of the last ice age correlates with a 30-fold increase in eruption rate. (Source)in

• Now, that article is amazing - what a study! Linking climate change to the rise of the Andes, with climate change as the cause! – user889 Dec 10 '14 at 4:50

Isostatic depression and Post-glacial rebound are something that we can definitely observe, are definitely caused by climate changes, and pretty clearly count as an "effect on plate tectonics", since they change the vertical profile of the plates and thus must have an effect on how they move.

So I would say the answer is "yes".

• He was asking about plate tectonics. I'm not sure isostatic rebound fits that. – Gimelist Nov 23 '14 at 18:56
• Perhaps, the inclusion of a link between isostasy and tectonics would strengthen this answer. – user889 Nov 23 '14 at 23:59
• Nicely done, certainly food for thought +1 – user889 Nov 24 '14 at 9:32

I would argue that the heaviest impact on plate tectonics is not only climate, but the atmosphere and oceans as whole.

Oxygenation from the atmosphere and hydratation from the oceans will lead to a decrease in viscosity of minerals that are subducted with them. This can make sense if you think about it: $H_2 O$ and $O_2$ would be volatiles under lithospheric pressures and temperatures, however by subduction they are forced into the minerals' crystal lattice and can act as mobile defects.

Thus, lattice chemistry plays a role in defining the macroscopic material variables as viscosity, thermal conductivity and diffusivity of the melt. If my interpretation of the possibly-existing supercontinent-cycle is correct, this would mean that a significant portion of mantle-material 'sees' the surface every ~300-500Myears and then has the potential to be altered by surface/ocean chemistry for the next subduction cycle.

Update:

So I had a quick discussion with a Geophysics Prof about this. He didn't know out from his head any good source for the viscosity due to $O_2$/$H_2O$ in minerals. However he has pointed me to this article discussing a much stronger effect on Venusian plate tectonics: Surface temperatures.

The paper argues that as viscosity goes like $\sim exp(E_{activation}/k_B T)$, a varying surface temperature from 750 to 1000K this can have quite an impact on the viscosity or the Peclet number (energy transport by convection over diffusion). The latter can vary in this range from <1 to >100.
But as the surface temperature obviously only poses a boundary condition, we don't know for sure how far down into the mantle those differences can propagate.

Coming back to Earth it's obvious that this effect would obviously be much smaller, as surface Temperature variations won't be 250K over Gyr timescales. However interesting to note.

• This sounds like a very pertinent and interesting answer - I look forward to when you are able to find some sources. – user889 Nov 25 '14 at 3:26
• "H2O and O2 would be volatiles under lithospheric pressures and temperatures, however by subduction they are forced into the minerals' crystal lattice and can act as mobile defects." I don't understand it. Do you mean that they enter the lattice as integral constituents (e.g. water in gypsum) or as defects in otherwise anhydrous minerals? Even so, what does it have to do with climate change? Water and oxygen are around regardless of climate change. – Gimelist Dec 10 '14 at 6:29
• I'm no mineralogist, I just know that they definetly can act to alter viscosity by 1-2 orders of magnitude when 'entering' the minerals. And ofc this has to do with climate change: Think about how oxygen has evolved throughout of Earth's history. Also Water evaporating on Gyr timescales may not play a role on Earth, but on other planets. – AtmosphericPrisonEscape Dec 11 '14 at 15:46
• @AtmosphericPrisonEscape there is a difference between oxygen evolution throughout the early Earth history (great oxygenation event, etc) and contemporary climate change. I don't see how contemporary climate change can change the composition of mantle minerals. – Gimelist Dec 19 '14 at 7:06