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Posts Tagged ‘thermal’

Plate tectonics key to life on Earth?

Tectonic plates. Courtesy US Geological Survey

Tectonic plates. Courtesy US Geological Survey

Is our vital blue planet the last of its kind?  Or has it always been one of a kind?  From the perspective of post-modern geologists, planet Earth is like no other solar body yet discovered.

“I think when you live on the Earth, you take it for granted,” says Katie Cooper, who thoughtfully considers such esoteric questions for a living. As one of a relatively new group of geologists who use computer simulations to study the thermal and tectonic evolution of our planet, her viewpoint is decidedly celestial.

Cooper, assistant professor in the School of Earth and Environmental Sciences, studies the broad area of geodynamics—particularly the evolution of Earth as a planetary system. Specifically, she models how the three main layers of our planet—core, mantle, and crust (lithosphere)—interact and change over time.

“I look at the Earth as a giant heat engine which drives all of the geologic activity we see at the surface,” she says. “In the past, the core was hotter than it is today. The planet is slowly cooling and that affects everything on the lithosphere.”

That cooling takes place in large part through thermal convection. Like boiling water or the slow movement of oil blobs in a lava lamp, hot plastic rock from the Earth’s mantle is constantly rising toward the surface, where heat and energy are released in hot springs, earthquakes, or volcanic eruptions. At the same time, cooler rock is sinking toward the interior core.

This steady interplay leads to the phenomenon of plate tectonics where vast puzzle-like sections of Earth’s crust “float” on top of hot rock in the mantle—and imperceptibly migrate across the globe.

Earth stands alone

Although plate tectonics is often taken for granted as standard planetary modus operandi, it turns out that Earth is a world apart from other planets.

“Plate tectonics is unique to Earth as far as we know right now,” says Cooper. “The big question is if this is unique to our solar system? Our galaxy?  The universe?”

Not only unique, but possibly essential to life itself. Through its part in cooling the planet’s interior, plate tectonics allows Earth to maintain a magnetic field that shields our world from dangerous solar radiation and, in effect, creates a safe haven for life to flourish. Which presents Cooper with another question—did plate tectonics create optimal conditions for the initial occurrence of life?  No one knows for sure.

Plate tectonics—the next generation

For the first half of the twentieth century, geologists suspected that Earth’s continents had once formed a single land mass before breaking up and drifting aimlessly apart. The continental drift hypothesis was backed up by fossil evidence but no one could explain the actual physical processes driving it.

That changed in 1963, however, when Princeton professor, Harry Hess, used WWII submarine-hunting technology to discover unusual magnetic polarity in the ocean floor. It was concluded that hot rock from the mantle was rising up through the lithosphere and pushing the sea floor—and the continents on either side—apart.

This finding provided the mechanism to explain the purposeful movement of Earth’s plates and led to the development of the first theory of plate tectonics.

Today Cooper is among a new generation of geologists who study what could be called “post” plate tectonics. Taking the field up a notch, she investigates similar processes on other planets and asks why Earth has plate tectonics in the first place.

“Is it the preferred mode of operation?” she asks. “Does it help the planet lose heat most efficiently? Is it a coincidence?”

Using a computer cluster of 600 processors working together as a single unit, Cooper attempts to unlock these mysteries by crunching enormous calculations that often run days or weeks to generate results.

Doing these “paper and pencil calculations” as she refers to them, Cooper builds computer models of planets and applies basic laws of physics to see if the theories are applicable.


Even Extremophiles Know When to Back Off

A few years ago, I was working on a story involving a somewhat personal fact of life for women. It was the sort of think most would feel uncomfortable about discussing for the Sunday front page of Washington’s largest newspaper. I wanted to talk about this fact of life with a high-profile and female captain of industry, so I called the assistant of a Seattle bank president. The response was quick but polite: ixnay on the intervieway.

When I mentioned this outcome to a fellow reporter, she said, “People don’t get to a position like that by taking a lot of chances.”

Malcolm Gladwell had a similar thesis in a New Yorker piece earlier this year, asserting that entrepreneurs–seeming swashbucklers of the capitalist set–actually prefer to take the cautious if not sure route to wealth. (You can read the top here.)

It turns out that one of  the most crazy seeming animals is a pretty risk-averse creature as well.

The extremophile sulfide worm lives on the edge, but not too on the edge.

This character is known to science as Paralvinella sulfincola. It’s an extremophile–one of several recently discovered microbes and animals capable of living in environments of seemingly unbearable heat, pressure and acidity.

In a paper just out in the journal Nature Communications, a Washington State University biologist and New Zealand collaborator ask just how harsh the sulfide worm might like things. It turns out, not too much.

Raymond Lee, an associate professor in the WSU School of Biological Sciences, and lead author Amanda Bates of New Zealand’s University of Otago tested inch-long sulfide worms found on thermal vents a mile below the ocean surface on the Juan de Fuca ridge off British Columbia. They placed the worms in aquariums with hot and not-so-hot sections and found that the worms made a point of going to the cooler areas, even if they could handle temperatures of up to 55 degrees C, or 131 degrees F.

“The surprising finding is they are very conservative,” said Lee, who explored the vents using the Woods Hole Oceanographic Institution research submarine Alvin on a National Science Foundation grant. “They have a high thermal tolerance, but they don’t prefer to be near that high thermal tolerance. That tolerance is more a safety mechanism.”

The finding rebuts speculation that surfaced in the mid 1990s that these types of worms live between 60 and 80 degrees C., or 140 to 176 degrees F. In separate experiments, Lee and Bates found none of the worms could survive above 60 degrees C.

Lee said the work gives some insight into how animals work and the more limited environmental extremes that multicellular organisms can handle.

It’s a lesson we can all take to heart. It may look like deep-ocean bugs, acid loving worms, and captains of industry love heat and pressure. But over the course of a lifetime or the run of a species, it makes sense to take it easy out there.

Read more about Lee’s work in the Winter 2006 Washington State Magazine.