Caldera chronicles: Clarifying confusing classifications for volcanoes

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week’s contribution is from Michael Poland, geophysicist with the U.S. Geological Survey and scientist-in-charge of the Yellowstone Volcano Observatory.

The paintpots are acid sulfate springs, one of three different types of thermal features in Yellowstone. Steamboat Geyser, located nearby in Norris Geyser Basin, had one water eruption on Sept. 18, the ninth major eruption of 2022. Learn about these events occur. (video courtesy of Yellowstone National Park)

When the subject of volcanoes comes up, you’ll often hear the words “active,” “dormant” and “extinct.” But what precisely do they mean? Admittedly, use of these terms by volcanologists has been somewhat inconsistent and evolved with time, which has resulted in understandable confusion among non-volcanologists. A simple search for the terms online produces a number of contradictory results. So let’s try to clear this up, and describe the terms in the way that most volcanologists would use them (although we’ll note right off the bat that opinions vary, and not all volcanologists would wholeheartedly agree with the definitions below).

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