What do volcanoes smell like?

We asked CVO scientists what volcanoes smell like; here is what they said.

By Cascades Volcano Observatory September 25, 2024

We asked CVO scientists what volcanoes smell like; here is what they said.

It smells like:

• Dry, dusty rock (like on Mount St. Helens’ Pumice Plain in the height of summer);
• Warm, moist rock (near vents where steam is escaping);
• Like whatever is nearby (pine needles, blooming plants, stinky wetland plants, animals with wet fur);
• It certainly doesn’t have typical neighborhood smells, like car exhaust, restaurants, BBQs, etc., since volcanoes are generally in remote locations (rarified air?);
• Rotten eggs or an acrid smell, like a struck match (just downwind of a fumarole).

Recently, smells were reported in southwest Washington, mainly in Clark and Cowlitz Counties. These areas are relatively close to Mount St. Helens and the question was posed if the smell could be volcanic in nature.

The answer is no.

The USGS Cascades Volcano Observatory has two volcanic gas monitoring stations at Mount St. Helens. One is called “SNIF” and is located in the crater. It measures the compositions of gases (water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide) coming from vents on the 2004-08 lava dome. The other station, located northeast of the crater, measures the amount of sulfur dioxide emitted from Mount St. Helens.

Together, these two monitoring stations show that there has not been an increase in the composition or amount of gases being emitted from Mount St. Helens. In fact, Mount St. Helens is presently releasing only very small amounts of water vapor, carbon dioxide, and hydrogen sulfide, which is consistent with background behavior.

CVO is very confident in the measurements from SNIF because in the last 48 hours winds have shifted quite a lot (from the NW, S, and E, at an average speed of about 13 ft per second (4 m/s)), so the station has sampled gases from a variety of upwind directions. CVO crews were also conducting field work at Mount St. Helens on September 24, and did not report any significant or new smells.