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Geologist Uses Archaeology To Understand Climate Change

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Dr David Powars overlooks his office.
Sabri Ben-Achour
Dr David Powars overlooks his office.

The history of the past 100 million years is in a box in David Powars' home office in Winchester, Va. Powars is a geologist with the U.S. Geological Survey. So it kind of makes sense that his home office is basically an archeological site in and of itself. There are piles 6 feet high of maps and papers and boxes, fist-size drill bits and a steel drum.

He pulls out cylinders of rock and clay he drilled a few miles south of D.C. on the Potomac River. The cylinders are samples of the bedrock from hundreds of feet below, so you can see all the layers of soil, mud, and rock from ages past.

The ones he pulls out are mostly blackish green. Powars can read this record like a book, but instead of words, he sees microscopic fossils, types of minerals... and 55 million-year-old-poop.

It's called green sand because of the tiny little feces, from the bugs that were living in it, explains Powars.

From looking at that old, poopy clay, and the fossils inside, Powars can tell that 60 million years ago the D.C. area was a calm, shallow sea in which microscopic bugs could live their little bug lives gently swimming and pooping in peace. And then, 55 million years ago, "Bang! Everything changes."

In the geological blink of an eye, the Earth totally changed, and it can be seen in Powars' rock sample.

The next layer in Powars' sample is cream colored, because all those happy green pooping bugs are gone. All the shell fossils are gone in this layer, because the creatures that left them went extinct. The oceans acidified and dissolved their shells.

"The sedimentation rate increased ten-fold," says Powars.

This bizarre new Earth is home to a lot of rain, and a ton of massive storms. Mega rivers form between the Potomac and the Susquehanna and dump huge amounts of mud into the calm sea we used to have.

"This was a big river-dominated shelf like the Amazon," he says. "That's what these sediments tell us."

The Washington region, according these rocks, looked like the Amazon. "Something had to happen dramatic to do that."

What happened was climate change. In fossils all over the planet from this time, the carbon changes. Massive amounts of carbon entered the atmosphere and the oceans, and the greenhouse effect intensified.

"We had this major thermal maximum, the hottest time we know of," says Powars. "A spike all of a sudden, and it came on very fast worldwide."

How hot did it get? The Earth's temperature rose between 5 to 8 degrees Celsius. That's about 40 degrees Fahrenheit.

"The sea level was high, the shoreline was some place west of Richmond, west of D.C., west of the Piedmont," says Powards. "We just dated marine sediments west of Richmond, and it rose another 10, 20 meters. Some say 5 meters."

In the space of a few thousand years, the world was transformed. Powars says Washington, Virginia and Maryland were transformed from a calm shallow sea to a rainy misty hurricane buffeted tropical river system.

In fact, the same bacteria found in those cores from the Potomac are now found at the mouth of the Amazon.

Nobody knows where the carbon that caused this change came from. But scientists were able to calculate how much of it was released.

"The total quantity of carbon added to the atmosphere was something on the order of the quantity of carbon we have in known fossil fuel reserves today," says Lee Kump, a professor of geosciences at Penn State University. "So when we think about it in that regard, we have a similar amount of carbon to what we could put in the atmosphere from fossil fuel burning."

So are we headed toward a future in which the Blue Ridge Mountains are ocean front property? Gavin Schmidt, a climate scientist at the NASA Goddard Institute for Space Studies, says the world 55 million years ago was hotter to begin with.

"There was no ice around — no huge Antarctica, no Greenland, no melting glaciers, so a lot of the things that we're worried about are associated with features unique to this climate," he says. "We have to worry about how fast Greenland is going to melt, we have to worry about west Antarctic ice shelf, ice caps melting."

Another difference: the thermal maximum carbon release took 20,000 years and lasted 170,000. Humans could easily burn up all their fossil fuels in a couple hundred, and Lee Kump says in this case, speed matters.

"The temperature rise in the worst case scenario could be comparable to this extreme weather event in Earth's history, but even more critical here is that the rate of change is maybe a factor of ten faster," he says. "Rates do matter in the ability of ecosystems to adapt to those changes."

The one thing that the David Powar's box of mud does have to tell us for sure is that if anyone thinks that burning all our fossil fuels will have a mild effect on our world, they would be wrong.

[Music: "A Message" by Coldplay from X&Y]

Photos: Archaeology-Climate Change


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