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Old Faithful was once called “Eternity’s Timepiece” because of the regularity of its eruptions. However, this geyser never erupted at exact hourly intervals as many believe. Ranger Darlene Bos explains how we predict eruptions for this popular geyser. Additional filming by David Restivo and Jay Elhard. 
Predict Old Faithful
Calculate your own prediction for Old Faithful's next eruption. 
Hydrothermal Features
More than 10,000 hydrothermal features are found here, of which more than 500 are geysers. 
Current Geyser Activity
Get the latest geyser eruption predictions. 
Old Faithful FAQs
Is Old Faithful slowing down. Learn that and more. 
In Depth: Geysers
Learn about the mechanics of geysers, their role in the park's history and what they teach us about the world in which we live. |
Last updated: April 17, 2025