Most of the world's geysers are found in the United States, Russia, Chile, New Zealand and Iceland. Worldwide, there are only about 1000 geysers. Over 50 percent of the world's active geysers are located in Yellowstone National Park.
The volcanic rock rhyolite is particularly effective at hosting geysers. Most of the geyser fields in the world have formed in rhyolite or similar silica-laden rocks, such as ignimbrite. The conditions required for geysers to form include hot rocks below the geysers, an ample ground water source, a subsurface water reservoir and fissures to deliver water to the surface.
The most famous geyser in the world is "Old Faithful" in Yellowstone National Park, which erupts regularly about every 60 to 90 minutes. The tallest active geyser in the world as of 2014 is the Steamboat Geyser, also located in Yellowstone National Park. Some of its eruptions blast water as high as 400 feet into the air. Until 1902, Waimangu Geyser in New Zealand was the tallest geyser in the world, with eruptions blasting jets of water up to 1600 feet in the air. Since the 1960s, the volcanic heat and abundant water found in geyser fields have been increasingly harnessed to produce geothermal energy.