Faithful, yes . . . in its fashion. Yellowstone National Park’s most famous geyser, Old Faithful, operates on what you might call flextime, erupting every 65 to 90 minutes. The sight of 3,700 to 8,400 gallons of boiling water rocketing from the earth roughly 130 feet into the air is a demonstration of nature’s power and beauty that’s worth waiting for.

IT’S ALL IN THE NAME
Members of the Washburn Expedition, credited with the 1870 "discovery" of Yellowstone, bestowed the title of Old Faithful on the geyser after observing its somewhat predictable behavior.

WARM-UP ACT
Old Faithful bubbles and sputters for about 10 minutes before erupting—a period geologists refer to as preplay.

CHEAP THRILLS
Yellowstone’s early visitors dropped sticks and other debris into the geyser to watch it all get blown back out.

TINY TENANTS
Thermophiles—microorganisms suited to temperatures as high as 284° F—are thought to exist within Old Faithful’s underground fissure.

CRANK IT UP
Park employees positioned a large hand crank near the geyser in 1969 and worked it furiously during a burst as bemused spectators looked on.

AD NAUSEAM
A 2002 commercial that simulated a ranger pouring a fiber supplement down Old Faithful’s cone to "keep it regular" irked park officials working to prevent people from tossing stuff into geysers.

IF YOU’RE GOING . . .
Old Faithful is located along Grand Loop Road in the Wyoming section of Yellowstone National Park. (307) 344-7381, www.nps.gov/yell.