Hot climate could shut down plate tectonics

May 12, 2008

A new study of possible links between climate and geophysics on Earth and similar planets finds that prolonged heating of the atmosphere can shut down plate tectonics and cause a planet's crust to become locked in place.

"The heat required goes far beyond anything we expect from human-induced climate change, but things like volcanic activity and changes in the sun's luminosity could lead to this level of heating," said lead author Adrian Lenardic, associate professor of Earth science at Rice University. "Our goal was to establish an upper limit of naturally generated climate variation beyond which the entire solid planet would respond."

Lenardic said the research team wanted to better understand the differences between the Earth and Venus and establish the potential range of conditions that could exist on Earth-like planets beyond the solar system. The team includes Lenardic and co-authors Mark Jellinek of the University of British Columbia in Vancouver and Louis Moresi of Monash University in Clayton, Australia. The research is available online from the journal Earth and Planetary Science Letters.

The findings may explain why Venus evolved differently from Earth. The two planets are close in size and geological makeup, but Venus' carbon dioxide-rich atmosphere is almost 100 times more dense than the Earth's and acts like a blanket. As a result, Venus' surface temperature is hotter than that of even Mercury, which is twice as close to the sun.

The Earth's crust -- along with carbon trapped on the oceans' floors -- gets returned to the interior of the Earth when free-floating sections of crust called tectonic plates slide beneath one another and return to the Earth's mantle. The mantle is a flowing layer of rock that extends from the planet's outer core, about 1,800 miles below the surface, to within about 30 miles of the surface, just below the crust.

"We found the Earth's plate tectonics could become unstable if the surface temperature rose by 100 degrees Fahrenheit or more for a few million years," Lenardic said. "The time period and the rise in temperatures, while drastic for humans, are not unreasonable on a geologic scale, particularly compared to what scientists previously thought would be required to affect a planet's geodynamics."

Conventional wisdom holds that plate tectonics is both stable and self-correcting, but that view relies on the assumption that excess heat from the Earth's mantle can efficiently escape through the crust. The stress generated by flowing mantle helps keep tectonic plates in motion, and the mantle can become less viscous if it heats up. The new findings show that prolonged heating of a planet's crust via rising atmospheric temperatures can heat the deep inside of the planet and shut down tectonic plate movement.

"We found a corresponding spike in volcanic activity could accompany the initial locking of the tectonic plates," Lenardic said. "This may explain the large percentage of volcanic plains that we find on Venus."

Venus' surface, which shows no outward signs of tectonic activity, is bone dry and heavily scarred with volcanoes. Scientists have long believed that Venus' crust, lacking water to help lubricate tectonic plate boundaries, is too rigid for active plate tectonics.

Lenardic said one of the most significant findings in the new study is that the atmospheric heating needed to shut down plate tectonics is considerably less than the critical temperature beyond which free water could exist on the Earth's surface.

"The water doesn't have to boil away for irrevocable heating to occur," Lenardic said. "The cycle of heating can be kicked off long before that happens. All that's required is enough prolonged surface heating to cause a feedback loop in the planet's mantle convection cycle."

Source: Rice University

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2.8 / 5 (9) May 12, 2008
OMG how stupid... Just laying groundwork for more alarmism in the future around GW. Soon Global Warming, specifically that caused by Evil American Capitalism, will be blamed for the eventual collapse of the universe. Are there no real scientists left on this planet?! Maybe Global Warming fried all their brains?
2.8 / 5 (9) May 12, 2008
Ball point pens leak worse in hot weather.... I need to study the effect that global warming will have on ball point pens... anyone out there willing to help me fill out funding request.... we could use the headline.... Global Warming theatening the writing industry.... or Global warming will affect ink consuption.... or Global warming will cause the destruction of trees, since ball point pens will become less reliable in the heat..... or Global warming ????
2.3 / 5 (8) May 12, 2008
Jburchel and Thinking I am so happy to see that these stupid and biased papers to promote the black side of science corrupted by money did not get smart people like you.
OMG, when we talk about tectonics we are thinking on a temperature gradient significantly higher (thousands) than tenths of a degree on the these fallacy of Global Warming.
Well done JBurchel and Thinking!
3.3 / 5 (6) May 12, 2008

OMG, when we talk about tectonics we are thinking on a temperature gradient significantly higher (thousands) than tenths of a degree on the these fallacy of Global Warming.

You beat me to it. I didn't even have to read the article to think "WTF"? (on the subject of internet acronyms)
3 / 5 (8) May 13, 2008
No doubt some alarmist media type will pick this paper up and claim that if we don't raise taxes, shut down the economy, and ban capitalism we will all be buried by lava -- like on Venus.

Sadly all of science will pay a price in future credibility for allowing this AGW nonsense to get so far out of control.
3.7 / 5 (7) May 13, 2008
The article is clearly not about human caused global warming, it is about the temperature range in which an earth like planet is feasible. If the article has a flaw, it is that it fails to mention the rather important factor that the Earth has a very large moon, and Venus does not. The heat generated within the planets may also vary, which surely will have a huge bearing. In addition, it seems likely that a higher temperature would lead to more convection, not less, so I suspect there would be another, higher temperature, at which plate tectonics would resume, and be more intense. Composition of the planet would also have a large affect - a planet with less oxygen or more sulpher than the Earth would presumably behave differently. I think that, other than bulk density, we don't know much about the composition of Venus. So overall, the article is only useful in that it points out that, in theory, if you ignore all other variables, a hotter surface temperature could result in less plate tectonics, maybe.
2.3 / 5 (6) May 13, 2008
The scorn and criticism should be directed at the NSF, who probably funded this research. What idiots!
May 13, 2008
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1 / 5 (5) May 13, 2008
Look Pogsquog,

I hate to say that but you are completely wrong!
And worst, you write with this pseudo literacy such as, composiiton...large moon...and people with little grasp on science might think you are right.
Unfortunately, your considerations are like piss in the wind (W. Shakespeare). The core of your statement is bluntly wrong!
I will cote you:"In addition, it seems likely that a higher temperature would lead to more convection"...
Convection runs on GRADIENT, which means difference of anything such as, pressure, salinity or temperature. If you increase the surface temperature until it is the same as the core of the Earth all convection would cease!
So, at least in this point the article that I criticised firstly is right. The nonsense on the article is exactly what I have pointed: In Global Warming issues we are considering increases in temperature in the order of 0.3 to 0.4 C and this is insignificant to cause any variation in plate tectonics that is driven by temperatures in the order of 2200 C!
Daily temperature variation would affect plate tectonic harder as they are in the order of some Celsius degrees. In other words, daily temperature variations are more than 10 times higher than the temperature range suggested by this infamous article.
Hope I was clear enough now.
5 / 5 (1) May 16, 2008
It is you who does not understand - it is impossible for the surface of Venus to be at the same temperature as the core, because heat is made within the planet, thus the core will always be hotter than the outside, and there will always be a large temperature gradient. However, at higher temperatures, the crust will be thinner and more of the planet's interior will be liquid, and hence able to convect. If you raised the temperature of the Earth's atmosphere to the same as its core temperature now, the crust would be entirely molten - but the core temperature would also rise correspondingly, and the planet would bubble quite nicely thank you.
not rated yet May 16, 2008
So in a way, humans found a cure to prevent the common earthquake. And to thinking global warming was a bad thing...

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