Taking the mystery out of volcanic gas sampling
Ever wonder what scientists are doing when you see them with strange equipment near hot springs and fumaroles? They're collecting some of nature's most revealing secrets – volcanic gases!
When you visit California's volcanic areas, you might notice white clouds of steam rising from hot springs, bubbling pools, and fumaroles, especially in the morning. But there's more than just water vapor escaping from beneath the surface. Invisible gases like carbon dioxide, hydrogen sulfide (that rotten-egg smell!), nitrogen, methane, and helium are also making their way up from deep underground. These gases are like a volcano's vital signs – they tell us what's happening with magma movement deep in the Earth's crust and can provide early warnings of changing volcanic activity.
The trick is collecting high-quality samples without contamination from the atmosphere or equipment. Scientists use pre-evacuated glass bottles with special stoppers, often holding an alkaline solution that helps capture acidic gases and concentrate the non-reactive ones like helium. The real challenge is safely getting close enough to sample near gas vents, which are usually surrounded by unstable ground and hot, corrosive conditions.
Our sampling setup depends on what we're working with. Sometimes we insert a titanium tube directly into a fumarole or use an inverted plastic funnel buried in steaming ground or placed on a bubbling pool's surface – like you see in this photo from the Salton Buttes geothermal field. For dangerous or hard-to-reach features, we might need long lengths of tubing and a painter's pole to keep our distance. Once we've gotten a good seal and purged all the air from our system, we open the sample bottle and let gas flow in while steam condenses – a process that can take up to 30 minutes. We often cool the bottle with a wet cloth to encourage condensation.
As part of our comprehensive monitoring program, CalVO scientists regularly sample gases from California's moderate to very-high-threat volcanoes, including Medicine Lake volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Mono Lake Volcanic Field, Long Valley Caldera, Mammoth Mountain, Coso Volcanic Field, and Salton Buttes. Every sample helps us better understand and monitor these sleeping giants.
Learn more about CalVO's monitoring work!