How Geysers Work

Old faithful geyser erupting with sunset in the background
View of the Old Faithful Geyser in Yellowstone National Park as it erupts against a dark sky, Wyoming, 1941. Getty Images

Right now, in a few rare places on Earth, people are enjoying the sight and sound of superheated water rushing from deep below ground and into the air. These unusual geological formations, called geysers, exist on Earth and throughout the solar system. Some of the most famous ones on Earth are Old Faithful in Wyoming in the United States and the Strokkur Geyser in Iceland.

Geyser eruptions happen in volcanically active areas where superheated magma sits fairly close to the surface. Water trickles (or rushes) down through cracks and fractures in the surface rocks. These "conduits" or "pipes" can reach a depth of more than 2,000 meters. Once the water contacts rocks that have been heated by volcanic activity, it starts to boil. Eventually, the pressure rises and that sets a series of actions in motion. When the pressure gets too high, the water rushes back up the pipe, carrying minerals along with it. Eventually, it blows out, sending a rush of hot water and steam into the air. These are also called "hydrothermal explosions." (The word "hydro" means "water" and "thermal" means "heat.")

How Geysers Work

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The mechanics of a geyser and how it works. Water seeps down through cracks and fissures, encounters heated rock, is heated to superboiling temperatures, and then erupts outward. USGS

Think of geysers as natural plumbing systems that deliver water heated deep within the planet out to the surface. They come and go depending on the underground activity that feeds them. While active geysers can be easily studied today, there's also ample evidence around the planet of dead and dormant ones. Sometimes they die out when the rock "pipes" get clogged with minerals. Other times mining activities turn them off, or hydrothermal heating systems used by people to warm their homes can drain them.

Geologists study the rocks and minerals in geyser fields to understand the underlying geology of the structures that stretch below the surface. Biologists are interested in geysers because they support organisms that thrive in hot, mineral-rich water. These "extremophiles" (sometimes called "thermophiles" due to their love of heat) give clues to how life can exist in such hostile conditions. Planetary biologists study geysers to better understand the life that exists around them. And other planetary scientists use them as ways to understand similar systems on other worlds.

The Yellowstone Park Collection of Geysers

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Old Faithful geyser at Yellowstone National Park. This one erupts about every 60 minutes and has been probed with space-age cameras and imaging systems. Wikimedia Commons

One of the most active geyser basins in the world is at Yellowstone Park. It sits atop the Yellowstone supervolcano caldera in northwestern Wyoming and southeastern Montana. There are around 460 geysers rumbling at any given time, and they come and go as earthquakes and other processes make changes in the region. Old Faithful is the most famous, attracting thousands of tourists throughout the year.

Geysers in Russia

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Valley of the Geysers in Kamchatka, Russia. This picture was taken just prior to a mudflow that engulfed some of the geysers. This remains a very active region. Robert Nunn, CC-by-sa-2.0

Another geyser system exists in Russia, in a region called the Valley of the Geysers. It has the second-largest collection of vents on the planet and is in a valley about six kilometers long. Scientists are studying this and the Yellowstone region to understand the types of life forms that exist in these systems.

Iceland's Famous Geysers

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Strokkuer Geysir erupting, November 2010. Copyrighted and used by permission of Carolyn Collins Petersen

The volcanically active island nation of Iceland is home to some of the most famous geysers in the world. The word "geyser" comes from their word "geysir", that describes these active hot springs. The Icelandic geysers are associated with the mid-Atlantic Ridge. This is a place where two tectonic plates—the North American Plate and the Eurasian Plate—are slowly moving apart at a rate of about three millimeters a year. As they move away from each other, magma from below rises up as the crust thins. This superheats the snow, ice, and water that exist on the island during the year, and creates geysers.

Alien Geysers

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Plumes of water ice crystals, possible cryogeysers, jet out from cracks in Enceladus's south polar region. NASA/JPL-Caltech/Space Science Institute

Earth isn't the only world with geyser systems. Anywhere that interior heat on a moon or a planet can warm up water or ices, geysers can exist. On worlds such as Saturn's moon Enceladus, so-called "cryo-geysers" spout from beneath the frozen surface. They deliver water vapor, ice particles, and other frozen materials such as carbon dioxide, nitrogen, ammonia, and hydrocarbons to the crust and beyond.

Europa and ocean
Europa may have a hidden ocean beneath its icy crust. We see a cutaway here, against a backdrop of Jupiter and the tiny volcanic moon Io. Geysers may well be erupting from deep beneath the surface. NASA

Decades of planetary exploration have revealed geysers and geyser-like processes on Jupiter's moon Europa, Neptune's moon Triton, and possibly even distant Pluto. Planetary scientists studying activity on Mars suspect that geysers can erupt at the south pole during spring heating.

Using Geysers and Geothermal Heat

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The Hellesheidi Power station in Iceland, which uses boreholes to capture heat from underground geothermal deposits. It also provides hot water to nearby Reykjavik. Creative Commons Attribution 2.0

Geysers are extremely useful sources of heat and electricity generation. Their water power can be captured and used. Iceland, in particular, uses its geyser fields for hot water and heat. Depleted geyser fields are sources of minerals that can be used in various applications. Other regions around the world are starting to emulate Iceland's example of hydrothermal capture as a free and fairly unlimited source of power.

Beyond Earth, the geysers of other worlds might actually be sources of water or other resources for future explorers. At the very least, studies of those distant vents will help planetary scientists understand the processes at work deep inside those places.