Geysers are a rare phenomenon that exist in only a few places on the Earth. Some of the tallest are in New Zealand, Iceland, Geyser Valley in Russia, and Wyoming’s Yellowstone National Park. Yellowstone’s 500-ish geysers — a handful of which are shown in this video — are the product of the geothermal heat of a massive, ancient and active volcanic caldera (an exploded crater) that is a majority of the park. 

Geysers such as Old Faithful are a type of geothermal feature that periodically erupt scalding hot water. Increased pressure exerted by the enormous weight of the overlying rock and water prevents deeper water from boiling. As the hot water rises it is under less pressure and steam bubbles form. They, in turn, expand on their ascent until the bubbles are too big and numerous to pass freely through constrictions. At a critical point the confined bubbles actually lift the water above, causing the geyser to splash or overflow. This decreases the pressure of the system and violent boiling results. Large quantities of water flash into tremendous amounts of steam that force a jet of water out of the vent: an eruption begins. Water (and heat) is expelled faster than the geyser’s recharge rate, gradually decreasing the system’s pressure and eventually ending the eruption.

Old Faithful, a cone geyser named in 1870, is called the most predictable in this geothermic process, erupting for 2.5 minutes every 91 minutes.

Our favorite: Beehive. Bonus: immediate rainbow sighting.