By Lee Anna Sherman
When the Earth burps, WeiLi Hong listens. Whether Earth’s gaseous emissions bubble up from “mud volcanoes” on the planet’s surface or seep out of fissures on the ocean floor, the Oregon State University Ph.D. student has his monitoring gear to the ground.
And sometimes, he’s actually in the ground.
“I fell in twice,” Hong admits, describing the hazards of surveying mud volcanoes in his home country of Taiwan. “I was trapped in thick mud up to my waist. There was nothing solid to grab onto. I had to kind of roll across the surface of the mud until I could pull myself out.”
Which brings up a couple of questions: What is a mud volcano, anyway? And why would anyone risk life and limb traipsing around these oddities of nature?
The answer is methane — millions and millions of tons of it trapped in ancient sediments. Under pressure from the bumping and grinding of tectonic plates, the gas migrates upward through Earth’s crust, seeking the atmosphere. Certain countries, such as Taiwan, Indonesia, Pakistan and Azerbaijan, are “burping gas like overfed infants,” to borrow a metaphor from one New York Times writer on the subject of methane emissions. As the methane escapes, creating a slurry of fluids and dissolved solids, volcano-like mud domes mound up across the landscape. They can be as small as a toddler’s backyard swimming pool and as big as several kilometers in diameter.
But that’s not the only way methane migrates. It comes up through the bottom of the ocean, too. On the seafloor, where it’s super-cold, seeping methane gets locked into ice-like structures called “hydrates,” Hong explains. Studying methane emissions on land, despite the pitfalls, is a walk in the park compared to studying them 2,000 feet beneath the sea.
“With mud volcanoes, we’re looking at how much methane is emitted to the atmosphere,” says Hong, who specializes in chemical oceanography in the College of Earth, Ocean, and Atmospheric Sciences. “With cold seeps, we’re looking at how much methane is emitted to the water column. To do that, we need a vessel with the ability to drill.”
The discomforts of being at sea for two months didn’t deter Hong two summers ago when, along with OSU researcher Marta Torres, he joined an exploratory expedition to Korea’s East Sea hunting for hydrates aboard the research ship Fugro Synergy. His job was to analyze the physical properties of sediment samples taken from the depths.
For scientists and engineers, this trapped methane presents both threats and opportunities. On one hand, Hong says, melting hydrates could trigger Earth-warming greenhouse-gas emissions and tsunami-causing landslides. On the other hand, methane could be an energy bonanza — if it could be safely harnessed. That’s why the Korean government and the U.S. Department of Energy cosponsored the 2010 Ulleung Basin Gas Hydrate expedition.
“We were looking at porosity, permeability, texture, composition,” he says. “We used an X-ray machine to get 3-D images of the cores.” Opening his laptop, he clicks on a grainy gray image from the bathysphere. As he toggles the image this way and that, he points out traces of long-dead organisms in the long-buried layers. “On the computer,” he notes, “you can rotate the sediment column to see how the geosphere, hydrosphere and biosphere interact.”
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