Old Faithful was the first geyser in Yellowstone to be named by the 1870 Washburn-Langford-Doane Expedition.
The geyser's eruption interval has lengthened over time due to seismic activity and changes in underground water supply.
The water temperature at the vent is approximately 204°F (95.6°C), while the steam temperature can exceed 250°F.
Geologists estimate the geyser has erupted more than a million times since Yellowstone became a national park.
The geyser is part of a complex system where underground channels are interconnected with nearby features like the Beehive Geyser.
Over 10,000 sensors and real-time data logs are used by researchers to analyze the geyser's subsurface plumbing.
The cone of the geyser is composed of siliceous sinter, a mineral deposit left behind as water cools near the surface.
Old Faithful is a cone geyser located in the Upper Geyser Basin of Yellowstone National Park, renowned for its predictable hydrothermal eruptions. Eruptions typically eject between 3,700 and 8,400 gallons of boiling water to heights ranging from 90 to 184 feet. The interval between eruptions currently fluctuates between 60 and 110 minutes, dictated by the volume of water discharged in the previous event. The geyser's plumbing system reaches depths of at least 75 feet below the surface. Eruptions last anywhere from 90 seconds to five minutes. The site is monitored by the National Park Service, which provides live eruption predictions based on geological data. It remains the most famous feature in a park containing more than 500 active geysers.
The elevated observation point on the Observation Point Trail offers a panoramic view of the geyser with the historic lodge in the background.
Download the NPS Yellowstone app to view live eruption predictions directly from the park's geological monitors.
Arrive at the boardwalk viewing area at least 30 minutes before the predicted eruption time to secure a front-row seat.
Stay on the designated boardwalks at all times, as the ground surrounding the geyser is fragile and potentially unstable due to high heat.
Do not attempt to walk on the hydrothermal crust off-trail, as the ground can be thin and hides scalding water.
Open year-round, though access to the area via park roads may be restricted by snow in winter months.
Maintain silence during the eruption countdown; do not throw objects into the vent; stay strictly on boardwalks.
