In Yellowstone National Park, large crowds watch in awe as Old Faithful erupts with a roar, launching a spire of water about 150 feet in the air.

Old Faithful erupts at regular intervals throughout the day, but it was not always so predictable.

Fossilized wood found on Old Faithful’s geyser mound suggests that the geyser once stopped erupting long enough for trees to grow there.

“Trees do not grow on active geyser mounds,” says Shaul Hurwitz of the United States Geological Survey.

His team sent samples of the wood for radio carbon dating, and found that all were from the 13th and 14th centuries.

“So looking into it, we found out that that was probably one of the driest periods in the region for last 1,200 years,” Hurwitz says.

He says that as climate change causes more severe droughts, something similar could happen again.

“There’s a chance that some of the geysers will change their frequency of eruptions and maybe even stop erupting, depending on the availability of water,” Hurwitz says.

A complete shut-off is not likely – it would take many years of continued drought. But Old Faithful could erupt less frequently, and eager tourists might have to wait longer to see the show.

Reporting credit: Robert Mullhaupt/ChavoBart Digital Media.