Hot climate could shut down plate tectonics
May 12, 2008A 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
Jul 27, 2009 |
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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!
You beat me to it. I didn't even have to read the article to think "WTF"? (on the subject of internet acronyms)
Sadly all of science will pay a price in future credibility for allowing this AGW nonsense to get so far out of control.
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"...
Wrong!
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.
I'll check out Malthusian concepts along the way.