Is Yellowstone National Park losing steam?
That's what U.S. Geological Survey scientist Bill Evans is hoping to find out by studying the rings of lodgepole pine trees in the park.
Although scientists can't measure how much steam is released by the park's famous geothermal features, it can find a record of carbon dioxide that derives from magma and is released into the atmosphere after it is trapped in trees. Scientists are fairly certain that the release of steam and CO2 are coupled, Evans said. Yellowstone is a huge producer of carbon dioxide, an estimated 45,000 tons a day.
With trees that date back to the 1500s found near Mammoth Hot Springs, Evans is hoping to find definitive proof of whether carbon dioxide output has remained the same, gone up or settled down.
In the December issue of the U.S. Geological Society of America, Evans was the lead author of a study detailing the first research into the tree ring-carbon dioxide link in Yellowstone. The study began about five years ago in the Mud Volcano thermal area north of Yellowstone Lake.
Specifically, Evans was looking for a tie between the release of carbon dioxide and an earthquake swarm that took place in 1978.
"We consider the Yellowstone caldera restless," Evans said. "The caldera floor goes up and down. Some of the nice lake basins are explosion craters. In the USGS, we worry about being able to recognize what leads up to one of these explosions.
"We don't know exactly what to look for," he said, although scientists figure that indicators may include the release of carbon dioxide, increasing seismic activity or increased heat at the earth's surface.
"The 1978 seismic swarm was associated with a huge cloud of carbon dioxide," Evans said, prompting the theory that the upflow of high-pressure CO2 was the cause of the seismic swarm, not intrusion by magma. Water and the flexing of the earth's brittle crust over the Yellowstone caldera are also causes of earthquake swarms.
With mobile CO2 monitors, scientists in the future can set up in the vicinity of earthquake swarms to measure carbon dioxide output. Studies in other countries, such as Japan, have shown a CO2-seismic swarm link. Evans thinks that tree core samples can tell scientists where and how to monitor in Yellowstone.
"If we can identify some seismic events that are caused by carbon dioxide, then we can look for the characteristics of it that are identified in the next swarm," Evans said.
Co-authors of the study were USGS scientists Deborah Bergfeld and John McGeehin, John King of Lone Pine Research in Bozeman and Hank Heasler of Yellowstone National Park.