The iconic US geyser called Old Faithful, now a symbol of reliability, has not always lived up to its name: it stopped erupting in the thirteenth century because of droughts.
Today, tourists flock to Yellowstone National Park in Wyoming to see Old Faithful dramatically and predictably spewing boiling water and steam about 20 times a day. It is powered by geothermal heat, which turns water into pressurized steam in underground cavities. When some of that vapour leaks out, the pressure drops and the mixture suddenly boils and erupts.
Shaul Hurwitz at the US Geological Survey in Moffett Field, California, and his colleagues gathered fossilized wood embedded in the mound of geological debris that surrounds Old Faithful. This wood came from trees that must have grown during a period when the geyser was not erupting.
Radiocarbon dating showed that the trees lived in the thirteenth and fourteenth centuries. That’s also when severe droughts wracked the Yellowstone region, tree-ring records show. Less rainfall would have meant less groundwater to supply the geyser’s eruptions.
Future warming could lead to more droughts and a slowdown of Old Faithful, the authors say.