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What is a Geyser?


Old Faithful Geyser - Yellowstone National Park

Old Faithful geyser of Yellowstone National Park blasts water about 150 feet into the air. © iStockphoto / Zuki.

What is a Geyser?

A geyser is a vent in Earth's surface that periodically ejects a column of hot water and steam. Even a small geyser is an amazing phenomenon; however, some geysers have eruptions that blast thousands of gallons of boiling-hot water up to a few hundred feet in the air.

Old Faithful is the world's best-known geyser. It is located in Yellowstone National Park (USA). Old Faithful erupts every 60 to 90 minutes and blasts a few thousand gallons of boiling-hot water between 100 and 200 feet into the air.




Conditions Required for a Geyser

Geysers are extremely rare features. They occur only where there is a coincidence of unusual conditions. Worldwide there are only about 1000 geysers, and most of those are located in Yellowstone National Park (USA).

Conditions Required for Geysers
1) hot rocks below
2) an ample groundwater source
3) a subsurface water reservoir
4) fissures to deliver water to the surface

El Tatio Geyser of Chile

El Tatio: Geysers of El Tatio, northern Chile. © iStockphoto / Rob Broek.


lady knox geyser new zealand

Lady Knox: Eruption of Lady Knox Geyser, New Zealand. © iStockphoto / Halstenbach.

Where are Geysers Found?

Most of the world's geysers occur in just five countries: 1) the United States, 2) Russia, 3) Chile, 4) New Zealand, and 5) Iceland. All of these locations are where there is geologically recent volcanic activity and a source of hot rock below.

Geysers in the United States
Umnak Island, Alaska
Kanaga Island, Alaska
Lassen Volcanic National Park, California
Long Valley Caldera, California
Hot Creek and Little Hot Creek, California
Morgan Springs, California
Salton Sea, California (extinct)
Beowawe Geyser Field, Nevada (extinct)
Black Rock Desert, Nevada
Great Boiling Springs, Nevada
Steamboat Springs, Nevada (extinct)
Mickey Hot Springs, Oregon

Countries With Active Geysers
1) United States - Yellowstone National Park
2) Russia - Dolina Geiserov
3) Chile - El Tatio
4) New Zealand - Taupo Volcanic Zone
5) Iceland - Many locations



strokkur geyser - Iceland

Strokkur Geyser is one of Iceland's most famous. It erupts to heights of seventy feet every ten to twenty minutes. © iStockphoto / Tetra2000.

Map of Active Geyser Fields
Map of World Geysers

Map showing the location of world countries with active geyser fields.

Yellowstone's Old Faithful: YouTube video of Old Faithful Geyser in eruption at Yellowstone National Park. Note how many people are present to witness the eruption!

Yellowstone's Old Faithful: YouTube video of Old Faithful Geyser in eruption at Yellowstone National Park. Note how many people are present to witness the eruption!

Iceland's "Strokkur Geysir": YouTube video of Iceland's Strokkur Geyser in eruption. Strokkur erupts to heights of up to 70 feet about every 10 to 20 minutes.

Iceland's "Strokkur Geysir": YouTube video of Iceland's Strokkur Geyser in eruption. Strokkur erupts to heights of up to 70 feet about every 10 to 20 minutes.

steamboat geyser

Steamboat Geyser of Yellowstone National Park. A rare eruption photo taken by E. Mackin, National Park Service in 1961.

old faithful geyser - California

California's Old Faithful: The United States has two "Old Faithful" geysers, both of which produce predictable eruptions. This one is near Calistoga, California. © iStockphoto / Stephan Hoerold.

How Often Do Geysers Erupt?

Most geysers erupt irregularly and infrequently. However, a few are known for regular eruptions. The most famous, named "Old Faithful" in recognition of its regular eruptions, is located in Yellowstone National Park (USA) and erupts about every 60 to 90 minutes. More details on the eruption intervals of Yellowstone geysers are given in the table below.

Old Faithful is Getting Slower
Research done at the United States Geological Survey suggests that long-term drought conditions in the Yellowstone area have lengthened the time interval between Old Faithful's eruptions. The delay is thought to be caused by a smaller water supply.

Yellowstone Geysers
Eruption Intervals, Duration, Heights
LocationAverage IntervalDurationHeight (ft)
Old Faithful65 or 92 min1.5-5 min106-184
Artemisiairregular5-25 sec30
Aurum2-4 hours70 sec20
Baby Daisy35-55 min3 min25
Beehive12-18 hours5 min150+
"Boardwalk"irregular5-10 min20
Castle12.5 hours15-20 min75
Daisy2.5 hours3.5 min75
Depression5-9 hours6 min10
Echinusirregular3-5 min30+
Fan & Mortar6-10 days?45 min100+
Fountain5.5 hours9 min78
Giantlast eruption 9/28/151 hour200+
Giantesslast eruption 1/30/144-48 hours150+
Grand8.5 hours8-12 min160+
Great Fountain12.5 hours45 min70-200+
Lion - initial to initialabout 8 hours1-7 min60
Lion - within seriesabout 90 min3-5 min30
Little Cubabout 55 min10 min5
Plate3.5-4 min4 min5
Plumerecent periods of dormancy1 min25
Riverside6.25 hours20 min75
Steamboatlast eruptions 5/23/05, 7/31/13, 9/3/1410+ min300+
Data from National Park Service
(Measurements done in 2002)

Great Fountain Geyser

Great Fountain: Great Fountain Geyser at sunset, Yellowstone National Park. © iStockphoto / Geoff Kuchera.

Which Geyser is the World's Largest?

The tallest active geyser in the world is Steamboat Geyser in Yellowstone National Park. Some of its eruptions blast water as high as 400 feet into the air. Don't go to Yellowstone expecting to see it erupt because it has erupted fewer than ten times in the last twenty years.

Waimangu Geyser in New Zealand used to be the tallest geyser in the world. Its eruptions were spectacular, blasting jets of water up to 1600 feet in the air. Unfortunately, a landslide altered the hydrology around Waimangu, and it has not erupted since 1902.

Geyser Strokkur - Iceland erupts

Geyser Strokkur erupts: A sequence of three photos showing an eruption of Geyser Strokkur, Iceland's most famous geyser. © iStockphoto / Christoph Achenbach.

How Do Geysers Work?

To understand how a geyser works, you must first understand the relationship between water and steam. Steam is a gaseous form of water. Steam is produced when water is heated to its boiling point. When water converts into steam at surface conditions, it undergoes an enormous expansion because steam occupies 1600 times as much space as the original volume of water. The eruption of a geyser is powered by a "steam explosion" when boiling-hot water suddenly expands into the much more voluminous steam.

To summarize: a geyser erupts when superheated groundwater, confined at depth, becomes hot enough to blast its way to the surface.

geyser-like eruption on Jupiter's moon, Io

Geyser-like eruption on Jupiter's moon, Io: Eruption of Tvashtar, a "geyser" on Jupiter's moon, Io. NASA Image.

Here's what happens in the ground...

Cool groundwater near the surface percolates down into the earth. As it approaches a heat source below, such as a hot magma chamber, it is steadily heated towards its boiling point. However, at the boiling point the water does not convert into steam. This is because it is deep below the ground, and the weight of cooler water above produces a high confining pressure. This condition is known as "superheated" - the water is hot enough to become steam - it wants to become steam - but it is unable to expand because of the high confining pressure.

At some point the deep water becomes hot enough, or the confining pressure is reduced, and the frustrated water explodes into steam in an enormous expansion of volume. This "steam explosion" blasts the confining water out of the vent as a geyser.

Enceladus remote sensing

Enceladus remote sensing: Monochrome and color-enhanced views of geyser activity on Enceladus. NASA Image.


artists impression - enceladus geyser

Enceladus geyser: Artist's impression of a cryovolcano on Enceladus. NASA artwork by David Seals.

Are There Geysers on Other Planets?

So far, geysers have not been discovered on other planets; however, geyser-like activity has been documented on some of the moons in our solar system. Jupiter's moon, Io, has eruptions of frozen water particles and other gases through vents in its surface. Triton, a moon of Neptune, and Enceladus, a moon of Saturn, also have these cold geysers sometimes called "cryovolcanoes." They are thought to erupt from pools of liquid water located a short distance below the surface of these moons. On the surface the eruptions are like a "volcanic snow."

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