Churning Caldron

Heat and gas rising from Yellowstone’s magma chamber make this muddy pool froth, fume, churn, and cook. Earthquakes repeatedly shake the area, opening vents that let gases rise, rumble, and bubble to the surface, causing the scalding hot water to roil even though it is not boiling. Its changing temperature has repeatedly transformed it over time: in 1971, mats of microorganisms grew on its warm, calm surface; after a swarm of earthquakes in 1978 and 1979 raised its temperature, gases bubbled up, the microbes died, and the pool began to churn again; and nearly five hundred earthquakes between July 1 and July 15, 1995, shook the area, while its water still roiled violently in 2002 as gases escaped from below.

Wyoming · United States