Of hot springs and gases

30/01/1998
Down To Earth

Of hot springs and gases each year, thermal features such as hot springs at the Yellowstone national park in the us emit millions of tonnes of carbon dioxide (co₂), the most important greenhouse gas, according to researchers at Pennsylvania State University (psu), usa.

This is more than the emissions from a typical industrial power plant, they claim. Industrial smokestacks are primarily blamed for the increase in co₂ emissions. But hot spring systems, such as those in Yellowstone national park, produce enough co₂ to be considered an important source of global co₂ emissions, the researchers contend.

Cindy Werner, a geoscience graduate student at psu , spent the summer of 1997 sampling gases emerging from thermal vents, mud pots and adjacent ground in Yellowstone's Mud Volcano area. Much of the co₂appeared to escape along fault lines running through the area.

Werner, along with Susan Brantley, professor at psu , presented the results of the studies during a special session on the Yellowstone national park at the annual meeting of the American Geophysical Union in San Francisco, usa , in the third week of December. They observed that Yellowstone's Mud Volcano area produced about 1,76,300 tonnes of co₂ each year.

After expanding these figures in accordance with the park's underlying geology, the researchers estimate that the entire park may be emitting about 44 million tonnes of co₂ each year. On the other hand, a medium-sized power plant that runs on fossil fuels can be estimated to release 4.4 million tonnes of co₂ each year. "We believe that geothermal systems are significant contributors to global emissions of co₂ ' said Werner.

co₂ levels in the Earth's atmosphere have increased to more than 350 parts per million (ppm) at present from 290 ppm in 1860. Most of the blame for the increase has been levelled at burning of fossil fuels and a widespread loss of tropical forests that have an important role in converting the gas into oxygen. Many scientists and environmentalists contend that global temperatures will rise significantly due to the increasing levels of co₂ , which will trap and retain heat from sunlight. This process is similar to what happens in a greenhouse. Such a trend could lead to rising sea levels, cause severe droughts and storms, and disrupt the Earth's biological systems.

Scientists have long known that volcanic systems, such as those in Yellowstone national park, emit large amounts of co₂ along with their heat. But little attention has been paid to measuring the extent of the emissions from geothermal systems not associated with volcanoes. The researchers focused on the Mud Volcano area because its features are primarily gas-driven. They do not produce the prodigious amounts of water that flows from the park's main hot spring basins. Gases emerging from vents in the area also include high levels of helium-3, a helium isotope present in the Earth's mantle, but not the atmosphere. The helium-3 at Mud Volcano suggests that the heat, which keeps the area simmering, has taken a direct course from the mantle to the surface.

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