Yellowstone: Monitoring the Fire Below

Signs of Restlessness

Rising surface temperatures could mean that magma is inching closer to the surface, or that underground heat and fluid flow has shifted in some manner. It also can be a tip-off to groundwater pressure changes, which can alter the boiling point of underground fluids. Over large areas, surface temperature is detectable by satellite. But in 2002 a research team flew an infrared camera aboard a twin-engine aircraft over Yellowstone Park to get a initial sense of its surface heat patterns in higher resolution. “It’s like sensing the temperature of skin—in this case, the “skin” of the hot ground or hot water coming off of thermal features,” says park geologist Cheryl Jawoworski.

In fall 2005, Jawoworski and National Park Service colleagues commissioned flights over the park’s geyser basins, which include Old Faithful, to establish a solid set of baseline measurements for Yellowstone’s heat flux. The team will be able to compare future heat maps to this baseline to detect temperature changes and alert visitors to danger zones before they learn the hard way. Other scientists are testing another novel technique to image Yellowstone’s heat aerially: infrared cameras strapped to 2 m wide helium balloons.

Recent Unrest—In summer 2003, a portion of Norris Geyser Basin turned up the heat. Ground thermometer measurements revealed that cool soil along the Back Basin Trail shot up to 94 degrees C. A new mud pot also formed, spurting hot, acidic ooze onto the trail. These events indicated changes not in magmatic activity, but in underground water pressure. By looking back at the heat patterns on the 2002 aircraft map, park staff decided to reroute the Back Basin Trail and add wooden boardwalks to prevent accidents on hot ground. Jawoworski and her colleagues are still analyzing the results from the fall 2005 baseline flight.

GAS

The Monitoring—“We know that magmas are down there, they're putting off a lot of heat,” says Lowenstern. “They also put out a lot of gas. And one way that geologists and volcanologists can understand what magmas are doing is to look at that gas.” Lowenstern and his colleagues manually collect these gases in glass bottles, going face to face with acrid emissions of carbon dioxide, sulfur, helium, and hydrogen sulfide. They find the gases dissolved in the hot waters around Yellowstone and percolating from soils and hissing steam vents called fumaroles.

Analyses can reveal the chemical compositions and sources of the gas, whether from magma or shallow groundwater. By sampling gases 30 times a year in different locations, Lowenstern and his colleagues can understand what areas of Yellowstone are more affected by the magma chamber. Knowing if any unhealthy gases are building in particular areas also helps inform visitor safety.

Recent Unrest—A few months before the temperatures increased at Norris, a line of new fumaroles opened in a forested portion of the basin. Beyond this, no major changes in gas activity have occurred recently at Yellowstone. But even normal gas emissions can prove deadly in concert with certain weather and geographical conditions. In March 2004, biologists discovered five dead bison near the Gibbon River in the Norris Geyser Basin. The bison were lying on their sides with their legs straight out. Gas testing and blood and lung samples revealed that gas vents uphill from the bison emitted denser-than-air carbon dioxide and hydrogen sulfide, which stagnated in the low river valley on a cold, windless night. The group of bison roaming into the valley was asphyxiated en masse.

Print friendly format