Yellowstone National Park Geothermal Features

Geothermal Features of
Yellowstone National Park

In 1872 Yellowstone National Park was established as the world's first national park. It is located in northwest Wyoming and extends into Montana and Idaho. Covering 2,219,791 acres, it is about the size of Rhode Island and Delaware combined! Yellowstone National Park is in a huge volcanic basin which was the site of several massive volcanic eruptions, the last of which occured about 600,000 years ago. Yellowstone National Park is a region of incredible beauty, abundant wildlife and amazing geothermal features. Among the geothermal features found in Yellowstone are numerous geysers, hot springs, bubbling mud pots, and hot spring terraces.

Hot Springs

Hot springs are pools of hot water that have seeped to the Earth's surface to form small ponds. Much of Yellowstone is on a giant volcanic crater and hot magma (molten rock) is still lies below the surface. This is the source of heat for Yellowstone's hot springs and other geothermal features. Cold water from rain or snow melt seep through pourous rock and cracks in the ground to a depth of close to 10,000 feet where it drips and flows onto rocks heated by the magma below Yellowstone Park. The water is heated to temperatures of around 400 Fahrenheit (well above the boiling point of water) but it remains in a liquid state due to the pressure of the rocks above. This superheated water is less dense than cooler water and more buoyant. As a result the superheated water can rise back towards the surface, dissolving silica and other minerals along the way. When the water finally reaches the surface it deposits some of the silica along the edges of the hot spring giving it a light colored edge.


More than 75% of the world's geysers, including the world's largest are found at Yellowstone. A geyser is a hot spring which erupts periodically. These eruptions are caused by the buildup of hot water and steam trapped by constrictions in the "plumbing system" of a hot spring. When enough pressure builds up the geyser erupts, ejecting a column of hot water and steam into the air. As the eruption begins, and water is released at the surface, the pressure of the hotter water much farther below the surface drops suddenly. This causes huge explosions of steam and the bursting of superheated water into the sky. Old Faithful, the park's most famous geyser, is the most frequently erupting large geyser in Yellowstone National Park. It erupts every 66 to 80 minutes.

Hot Spring Terraces

The terraces at Mammoth Hot Springs were created when hot water containing carbonic acid rose through ancient limestone deposits (rather than through silica rich rock as is common at most hot springs) causing some of the limestone to dissolve. As the water reaches the surface and flows, the dissolved limestone that it carries, causes a much different effect than is seen at most hot spring. The limestone in the water solidifies forming beautiful terraces.


Mudpots are hot springs which do not have much water. The water in a mudpot is very acidic and it dissolves nearby rock into small pieces of clay. This clay then mixes with the hot water to create mud. Hot steam rising from below causes the mud to bubble and pop as the steam is released into the air.

Back to the Infrared Yellowstone Lesson Plans