One of the most famous geothermal features in the world, Old Faithful is a cone geyser located at the heart of Yellowstone National Park. Since accurate measurements have been recorded, the geyser has been tracked at “faithfully” erupting every 45 to 125 minutes, making it the best chance for visitors to plan to see an erupting thermal geyser. There are dozens of other geysers in the basin, but their eruption schedules can vary by up to 20 hours, and so they can’t be counted on for an eruption with any regularity.
The eruption of Old Faithful usually lasts 3 to 10 minutes and discharges anywhere from 3,700 to 8,400 gallons of nearly boiling water up to 185 feet high. The interval of eruptions has been increasing slightly in recent years, which may be caused by small earthquakes affecting the water table below ground.
Old Faithful Inn and Old Faithful Visitor Center make up an increasingly large campus around the geyser basin, which makes a great place to get some food, stay the night, and learn a lot more about the science and history behind Old Faithful, the other geysers, and the entire Yellowstone Caldera.