Favorable conditions for geyser exist in regions of geologically recent volcanic activity, especially in areas of more than average precipitation. For the most part, geysers are located in three regions of the world: New Zealand, Iceland, and the Yellowstone National Park area of the United States. The most famous geyser in the world is Old Faithful in Yellowstone Park. Old Faithful erupts every hour, rising to a height of 125 to 170 feet and expelling more than ten thousand gallons during each eruption. Old Faithful earned its name because, unlike most geysers, it has never failed to erupt on schedule even once in eighty years of observation.