HOW GEYSERS WORK - Geysers like Old Faithful create eruptions of this scale every day, to the delight of the millions of visitors who witness them each year. Yet, despite the unbelievable forces that drive their eruptions, geysers are among the rarest and most fragile natural phenomena on Earth. Landslides, earthquakes and many other factors can alter a geyser's eruptions or destroy the geyser altogether. There are only about a thousand geysers left active on the planet, in geyser fields in such diverse locales as Iceland, New Zealand, Chile and the U.S. The one thing all of these locations have in common with one another is a high level of geothermal activity, one of the key components of geyser formations. Geothermal energy, which is taken from heat within the Earth, drives volcanoes, hot springs and other forms of geothermal activity. Still, a geothermal energy source is just one necessary part of a typical geyser formation. In this article, we'll explore what else it takes to form a geyser, what exactly causes one to erupt and what makes some geysers so unique. Along the way, we'll also take a look at some springs that look and act like geysers, but operate in a completely different way. In addition to a heat source, geysers need a constant supply of water and an underground plumbing system that holds the water supply as it heats up. A geyser needs a water supply. What might not be so apparent is where the water in a geyser's eruption comes from. Many geysers are located near rivers and pull water from them. Others seem to depend more on rain and snow filtering miles beneath the ground for their water supply.

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How Geysers Work

BY JONATHAN ATTEBERRY

Imagine taking all of the water from your neighborhood swimming pool, pouring it into a massive, magma-powered pressure cooker and shooting the water hundreds of feet in the air. 

Old Faithful may be the world's most well-known geyser.

Geysers like Old Faithful create eruptions of this scale every day, to the delight of the millions of visitors who witness them each year.

Yet, despite the unbelievable forces that drive their eruptions, geysers are among the rarest and most fragile natural phenomena on Earth. 

Landslides, earthquakes and many other factors can alter a geyser's eruptions or destroy the geyser altogether.

What's more, nature isn't the only thing that can impact a geyser: Man has helped to destroy numerous geysers as well, sometimes unintentionally and sometimes through deliberate acts of vandalism.

As of 2009, there are only about a thousand geysers left active on the planet, in geyser fields in such diverse locales as Iceland, New Zealand, Chile and the U.S.

The one thing all of these locations have in common with one another is a high level of geothermal activity, one of the key components of geyser formations. 

Geothermal energy, which is taken from heat within the Earth, drives volcanoes, hot springs and other forms of geothermal activity.

Still, a geothermal energy source is just one necessary part of a typical geyser formation.

In this article, we'll explore what else it takes to form a geyser, what exactly causes one to erupt and what makes some geysers so unique.

Along the way, we'll also take a look at some springs that look and act like geysers, but operate in a completely different way.

How Geysers Form and Erupt

In addition to a heat source, geysers need a constant supply of water and an underground plumbing system that holds the water supply as it heats up.

We'll examine each of these separately and then explore how they work together to cause geysers to erupt.

·      Water supply: Clearly, a geyser needs a water supply. What might not be so apparent, however, is where the water in a geyser's eruption comes from.

The answer depends on the geyser. Many geysers are located near rivers and pull water from them.

Others seem to depend more on rain and snow filtering miles beneath the ground for their water supply.

·      Plumbing system: A geyser's plumbing system is a series of fissures in the Earth that start at the geyser's mouth and run miles beneath the Earth's surface, where the system connects to the geyser's heat source.

Each geyser's plumbing system is different: Some consist of a single long, vertical shaft, while others connect to large pockets of water beneath the surface.

Certain types of soil are much more suitable for the plumbing system's formation, particularly soils that contain a high concentration of rhyolite, a volcanic rock that contains minerals that seal the geyser's plumbing system.

This mineral lining is crucial to the geyser's formation, as geysers operate under tremendous pressure and the plumbing system must be able to contain this pressure for the geyser to function.

·      Heat source: We already know that geysers occur in areas of high geothermal activity, but where does that energy come from?

The water in geysers is heated by magma that lies around 3 miles (4.8 kilometers) beneath the surface of the Earth.

While that might seem like a long way down, magma underneath a geyser field is actually relatively close to the Earth's surface.

There are different reasons why the magma is so close to the Earth's surface, though many geyser fields are located on the edges of the Earth's tectonic plates.

These plates, which compose the Earth's lithosphere, are constantly in motion, creating faults and generating tremendous energy.

This activity can cause earthquakes and volcanoes, and it can also create heat sources for geysers.

In the next section, we'll learn why the boiling point of water is so critical to understanding how a geyser erupts.

How Do Geysers Erupt?

Now that we understand how the key components of a geyser work, let's figure out how these parts work together to create such spectacular eruptions.

The process begins as water migrates to the geyser's plumbing system through fissures in ground.

Since the plumbing system is miles deep, the water at the bottom of the geyser's plumbing is under incredible pressure from the water above it. Think of the entire system as a giant pressure cooker.

Pressure cookers work by creating a sealed, pressurized enclosure that helps to cook food much faster than cooking it in a normal pot.

Pressure cookers can do this because water's boiling point rises as it's pressurized. Think of what actually happens when water boils: Water starts to churn and bubbles of air begin to surface.

If more pressure pushes down on the water, water needs more and more energy (in the form of heat) to overcome that pressure and start pushing bubbles to the surface.

This explains why water inside a pressure cooker can reach temperatures of more than 125 degrees Celsius (257 degrees Fahrenheit), while the boiling point of water at standard pressure is only 100 degrees Celsius (212 degrees Fahrenheit).

Now consider the massive pressures placed on water within a geyser's plumbing system.

Water in such a system can reach incredibly high temperatures (and store incredible amounts of energy as a result) before it starts to boil.

As the magma at the base of the geyser transfers heat throughout the system, more energy gets trapped in the water. Eventually, pockets of water begin to reach their boiling point and become turbulent.

This turbulence pushes a relatively small quantity of water out of the opening of the geyser, decreasing the amount of pressure on the water remaining in the geyser.

With this sudden pressure drop (and corresponding drop in boiling point), the water in the geyser flashes into steam.

The steam quickly expands to 1,500 times the volume of water and this expansion violently pushes water and steam from the mouth of the geyser in an eruption.

These eruptions last as long as the water in the geyser remains hot enough to push water out of the geyser opening.

Eventually, the entire system will either run out of water or the water will cool down enough for the eruption to stop. The cycle, of course, starts all over again.

COLD GEYSERS

While most geysers are hot enough to scald you, so-called cold-water geysers are a different story.

These geysers, such as Crystal Geyser in Utah and Brubbel Geyser in Germany, are driven by carbon dioxide-rich water trapped beneath the surface of the Earth.

Similar to how heat-driven geysers work, when pressure on a cold-water geyser decreases, the carbon dioxide bubbles in the water expand and push water out of the geyser in an eruption.

Exploring the World's Most Famous Geysers

While every geyser operates in fundamentally the same way, all geysers are not created equal. In this section, we'll explore some of the world's most famous geysers and what makes them stand out above the rest.

·      Geysir: This geyser, located in Iceland's Haukadalur valley, was first discovered in 1294, making the Geysir the oldest known geyser on the planet. Geysir's activity slowed toward the end of the 19th century and it became dormant around 1915.

In 1935, however, an earthquake reactivated the geyser, which currently erupts about every eight to 10 hours. Geysir remains a major tourist attraction to this day.

·      Old Faithful: Probably the most famous geyser on Earth, Old Faithful is famous for its 100- to 180-foot (30 to 55 meter) high eruptions, as well as for the regularity with which these eruptions occur (hence the name).

The geyser takes about 45 to 110 minutes between eruptions, though more recently, its eruptions have tended to be larger and consequently farther apart as more water is needed to replenish the geyser.

Old Faithful is also a great example of a cone geyser.

Unlike fountain geysers, which erupt from a pool of water, cone geysers erupt from a cone shaped structure formed from the mineral-rich water that constantly shoots from its opening.

·      Grand Geyser: The tallest regularly erupting geyser on Earth, Grand Geyser routinely fires water up to 200 feet (61 meters) into the air.

Located in Yellowstone National Park, Grand Geyser is a great example of a fountain geyser.

Unlike cone geysers, which tend to produce a fairly vertical, constant column of water, fountain geysers erupt in a much more chaotic fashion.

·      Strokkur Geyser: This geyser, named after the Icelandic verb "to churn," is known for its frequent eruptions, which occur five to 10 minutes apart.

First active in 1789, Strokkur became inactive in 1896 after an earthquake hit the area and blocked its plumbing system.

In 1963, locals cleared the blockage and the geyser has remained active ever since.

·      Steamboat Geyser: Don't bother waiting for one of Steamboat's massive eruptions.

While Steamboat is considered to be the world's tallest active geyser, shooting water up to 300 feet (91 meters) in the air, the geyser is also notoriously finicky.

At one point, the geyser went 50 years without an eruption.

·      Waimangu Geyser: The highest geyser eruption of all time took place at New Zealand's Waimangu Valley.

In 1902, a geyser in the valley reportedly spouted water 1,475 feet (450 meters) in the air.

Unfortunately, the geyser became inactive after a landslide in 1904, putting a premature end to a truly spectacular sight.

WHAT'S WITH THE NAME?

You probably don't have to stretch your imagination to figure out how geothermal features like hot springs and mud pools get their names.

The origin of the word "geyser," on the other hand, is a bit more mysterious.

The word "geyser" actually relates back to the first geyser ever discovered, Iceland's Geysir. Geysir, discovered in 1294, is fittingly named after the Icelandic verb "to gush" (gjósa).

Human Interaction with Geysers

People should be careful around geysers. In 2001, an erupting geyser
in Kuirau Park, New Zealand, damaged trees in the area and splattered
 the park with mud.

Now that we've taken a comprehensive look at how geysers work, we're ready to look at man's past and present interaction with them.

Considering the spectacle of a geyser eruption, it's no surprise that tourism is the most common way that people interact with geysers.

Tourism serves to educate the public both on how geysers work and on what it takes to protect these natural resources.

Parks often take great care to control how tourists interact with geysers, in part because tourists can harm geysers with their trash and debris, but also because geysers are quite capable of harming tourists as well.

In 1903, four tourists visiting New Zealand got caught in a geyser jet in Waimangu Valley. The eruption killed all four people and carried them more than a mile (1.6 kilometers) away from its source.

While such incidents are rare, we should always remain conscious of the amazing forces behind geysers.

Geysers serve as more than tourist attractions, however.

The same geothermal energy that drives geyser activity can also be used to generate power for houses and businesses.

While geothermal energy can provide a clean source of electricity, tapping into that source can sometimes create major consequences for geothermal features in the area by draining the geyser fields of their water or energy.

People have also been known to intentionally destroy geysers through vandalism, throwing trash and debris into a geyser's opening and blocking its plumbing system.

It's somewhat ironic, then, that man has also gone to great lengths to create "artificial" geysers by digging wells that tap into a geothermal heat source.

While that type of geyser has a man-made plumbing system, its eruptions are driven by the same forces that power its natural counterparts.

People have also put a lot of energy into repairing natural geysers, as in the case of Iceland's Strokkur Geyser.

As we understand more about how fragile geysers are, we'll see more measures put in place to protect these natural wonders.

Articles on HowStuffWorks that were written by Planet Green bloggers represent those bloggers' own opinions and viewpoints on subjects related to the environment and conservation. To provide feedback or corrections to these articles, please visit our Contact Us page and select "Planet Green feedback."

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THE YELLOWSTONE SUPERVOLCANO - There's a powerful and violent menace lurking under northwestern Wyoming and southeastern Montana. It's called the Yellowstone Supervolcano and the resulting geysers, bubbling mudpots, hot springs, and evidence of long-gone volcanoes make Yellowstone National Park a fascinating geologic wonderland. The official name for this region is the "Yellowstone Caldera", and it spans an area about 72 by 55 kilometers in the Rocky Mountains. The caldera has been periodically sending lava and clouds of gas and dust into the atmosphere, and reshaping the landscape for hundreds of kilometers. Yellowstone Caldera is among the world's largest such calderas. The caldera, its supervolcano, and the underlying magma chamber help geologists understand volcanism and is a prime place to study first-hand the effects of hot-spot geology on the Earth's surface. The Yellowstone Caldera is really the "vent" for a large plume of hot material that extends hundreds of kilometers down through Earth's crust. The plume has remained relatively stable while the North American continent has passed over it. Geologists track a series of calderas created by the plume. These calderas run from the east to northeast and follow the motion of the plate moves to the southwest. Yellowstone Park lies right in the middle of the modern caldera.

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Exploring the Yellowstone Supervolcano

By Carolyn Collins Petersen

There's a powerful and violent menace lurking under northwestern Wyoming and southeastern Montana, one that has reshaped the landscape several times over the last several million years.

It's called the Yellowstone Supervolcano and the resulting geysers, bubbling mudpots, hot springs, and evidence of long-gone volcanoes make Yellowstone National Park a fascinating geologic wonderland.

The official name for this region is the "Yellowstone Caldera", and it spans an area about 72 by 55 kilometers (35 to 44 miles) in the Rocky Mountains.

The caldera has been geologically active for 2.1 million years, periodically sending lava and clouds of gas and dust into the atmosphere, and reshaping the landscape for hundreds of kilometers. 

Yellowstone Caldera is among the world's largest such calderas.

The caldera, its supervolcano, and the underlying magma chamber help geologists understand volcanism and is a prime place to study first-hand the effects of hot-spot geology on the Earth's surface.

The History and Migration of the Yellowstone Caldera

The Yellowstone Caldera is really the "vent" for a large plume of hot material that extends hundreds of kilometers down through Earth's crust.

The plume has persisted for at least 18 million years and is a region where molten rock from Earth's mantle rises to the surface.

The plume has remained relatively stable while the North American continent has passed over it. Geologists track a series of calderas created by the plume.

These calderas run from the east to northeast and follow the motion of the plate moves to the southwest. Yellowstone Park lies right in the middle of the modern caldera.

The caldera experienced "super-eruptions" 2.1 and 1.3 million years ago, and then again about 630,000 years ago.

Super-eruptions are massive ones, spreading clouds of ash and rock over thousands of square kilometers of the landscape.

Compared to those, smaller eruptions and the hot-spot activity Yellowstone exhibits today are relatively minor.

The Yellowstone Caldera Magma Chamber

The plume that feeds the Yellowstone Caldera moves through a magma chamber some 80 kilometers (47 miles) long and 20 km (12 miles) wide.

It is filled with molten rock that, for the moment, lies fairly quietly below Earth's surface, although from time to time, the movement of the lava inside the chamber triggers earthquakes.

Heat from the plume creates the geysers (which shoot superheated water into the air from underground), hot springs, and mudpots scattered throughout the region.

Heat and pressure from the magma chamber is slowly increasing the height of the Yellowstone Plateau, which has been rising more rapidly in recent times.

So far, however, there is no indication that a volcanic eruption is about to occur.

Of more concern to scientists studying the region is the danger of hydrothermal explosions in between major super-eruptions.

These are outbursts caused when underground systems of superheated water are disturbed by earthquakes. Even earthquakes at a great distance can affect the magma chamber. 

Will Yellowstone Erupt Again?

Sensational stories crop up every few years suggesting that Yellowstone is about to blow again.

Based on detailed observations of the earthquakes that occur locally, geologists are sure that it will erupt again, but probably not anytime soon.

But make no mistake about it, a Yellowstone super-eruption will happen again, and when it does, it will be a catastrophic mess.

What Happens During a Super-Eruption?

Within the park itself, lava flows from one or more volcanic sites would likely cover much of the landscape, but the bigger worry is ash clouds blowing away from the site of the eruption.

Wind would blow the ash as far as 800 kilometers (497 miles), eventually blanketing the mid-section of the U.S. with layers of ash and devastating the nation's central breadbasket region.

Other states would see a dusting of ash, depending on their proximity to the eruption.

While it's not likely that all life on earth would be destroyed, it would definitely be affected by the clouds of ash and the massive release of greenhouse gases. 
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On a planet where the climate is already altering rapidly, a additional discharge would likely change growing patterns, shorten growing seasons, and lead to fewer sources of food for all of Earth's life.

The U.S. Geological Survey maintains a close watch on the Yellowstone Caldera.

Earthquakes, small hydrothermal events, even a slight change in the eruptions of Old Faithful (Yellowstone's famous geyser), provide clues to changes deep underground.

If magma starts to move in ways that indicate an eruption, the Yellowstone Volcano Observatory will be the first to alert surrounding populations. 

Carolyn Collins Petersen

Astronomy Expert

Education

M.S., Journalism and Mass Communications, University of Colorado - Boulder

B.S., Education, University of Colorado

Introduction

Author/co-author of seven books on astronomy and planetary science, including Astronomy 101 and Space Exploration: Past, Present, Future

CEO of Loch Ness Productions, a production company specializing in educational materials for planetariums and science centers

Member of the American Astronomical Society and International Planetarium Society

Experience

Carolyn Collins Petersen is a science writer, producer, and former research astronomer. She is the CEO of Loch Ness Productions, a production company specializing educational documentary shows for planetariums and science centers. She has published 7 books on astronomy and planetary science, including Astronomy 101, Space Exploration: Past, Present, Future, and Hubble Vision. 

In addition to her own books and articles on astronomy, Carolyn has written exhibition texts for the Griffith Observatory in Los Angeles, the NASA/Jet Propulsion Laboratory in Pasadena, and the California Academy of Sciences in San Francisco.

Previously, Carolyn worked on a Hubble Space Telescope instrument team and served as an editor for Sky Publishing, which publishes Sky & Telescope and Skywatch. Carolyn has written more than 40 documentaries and several webcasts on space science, and she regularly gives public presentations and lectures on topics in astronomy.

Education

Carolyn earned a master's degree from the University of Colorado – Boulder, where she studied astronomy, astrophysics, and science communication. She also received her B.S. from the University of Colorado.

Publications

Space Exploration: Past, Present, Future, 2017, Amberley Books

Astronomy 101: From the Sun and Moon to Wormholes and Warp Drive, Key Theories, Discoveries, and Facts about the Universe, 2013, Adams Media

Visions of the Cosmos (with J.C. Brandt), 2005, Cambridge University Press

Hubble Vision (with J.C. Brandt), 2003, Cambridge University Press (two editions)

The New Solar System (editor, with K. Beatty and A.C. Chaikin), 1999, Cambridge University Press and Sky Publishing

Jupiter! 1989, Facts on File.

ThoughtCo and Dotdash

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