How large is the magma chamber that is currently under Yellowstone?

Yellowstone is underlain by two magma bodies. The shallower one is composed of rhyolite (a high-silica rock type) and stretches from 5 km to about 17 km beneath the surface and is about 90 km long and about 40 km wide. The chamber is mostly solid, with only about 5-15% melt.  The deeper reservoir is composed of basalt (a low-silica rick type) and extends from 20 km to 50 km beneath the surface.  Even though the deeper chamber is about 4.5 times larger than the shallow chamber, it contains only about 2% melt.

The method that scientists use to discern this information is similar to medical CT scans that bounce X-rays through the human body to make three-dimensional pictures of internal tissue. In an analogous manner, a method called seismic tomography uses hundreds to thousands of earthquakes recorded by dozens of stations to measure the speed of seismic waves through the Earth--data that allow geophysicists to make 3-D pictures of structures beneath the surface. Scientists compare these seismic velocities and infer the composition from deviations of these from average, thermally undisturbed values.

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Can earthquakes trigger volcanic eruptions?

Sometimes, yes. A few historic large regional earthquakes (greater than magnitude 6) are considered by scientists to be related to a subsequent eruption or to some type of unrest at a nearby volcano. The exact triggering mechanism for these historic examples is not well understood, but the volcanic activity probably occurs in response to a change...

When will Yellowstone erupt again?

We do not know. Future volcanic eruptions could occur within or near Yellowstone National Park for the simple reason that the area has a long volcanic history and because there is hot and molten rock, or magma, beneath the caldera now. USGS scientists monitor Yellowstone for signs of volcanic activity using seismographs (to detect earthquakes) and...

Is Yellowstone monitored for volcanic activity?

Yes. The Yellowstone Volcano Observatory (YVO), is a partnership between the United States Geological Survey (USGS), Yellowstone National Park, the University of Utah, the University of Wyoming, UNAVCO, the Montana Bureau of Mines and Geology, the Idaho Geological Survey, and the Wyoming State Geological Survey. YVO closely monitors volcanic...

What type of eruption will occur if Yellowstone erupts again?

The most likely explosive event to occur at Yellowstone is actually a hydrothermal explosion —a rock-hurling geyser eruption—or a lava flow . Hydrothermal explosions are very small; they take place every few years and form a crater a few meters across. Every few thousand years, a hydrothermal explosion will form a crater as much as a few hundred...

How far in advance could scientists predict an eruption of the Yellowstone volcano?

The science of forecasting a volcanic eruption has significantly advanced over the past 25 years. Most scientists think that the buildup preceding a catastrophic eruption would be detectable for weeks and perhaps months to years. Precursors to volcanic eruptions include strong earthquake swarms and rapid ground deformation and typically take place...

Can we use the heat from Yellowstone for energy?

Geothermal energy (heat energy from the Earth's interior), is used to generate electricity in a variety of places throughout the world. Although Yellowstone and its surroundings are a significant geothermal resource, the Park itself is off limits to development. Because geothermal developments often cause a decrease in flow of nearby hot springs...

Can you release some of the pressure at Yellowstone by drilling into the volcano?

Scientists agree that drilling into a volcano would be of questionable usefulness. In addition to the enormous expense and technological difficulties in drilling through hot, mushy rock, drilling is unlikely to have much effect. At near magmatic temperatures and pressures, any hole would rapidly become sealed by minerals crystallizing from the...

How can we tell when a volcano will erupt?

Most volcanoes provide warnings before an eruption. Magmatic eruptions involve the rise of magma toward the surface, which normally generates detectable earthquakes. It can also deform the ground surface and cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters. Steam-blast eruptions, however,...

What is the difference between "magma" and "lava"?

Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth's surface.

Can an eruption at one volcano trigger an eruption at another nearby volcano?

There are a few historic examples of simultaneous eruptions from volcanoes or vents located within about 10 km of each other, but it's very difficult to determine whether one eruption caused the other. To the extent that these erupting volcanoes or vents have common or overlapping magma reservoirs and hydrothermal systems, magma rising to erupt...
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July 18, 2016

Inside USGS, No. 6, Ken Pierce, Heavy Breathing of Yellowstone Caldera

Dr. Kenneth Pierce studied the geology and geomorphology of the greater Yellowstone area for nearly his entire career with the U.S. Geological Survey. From 1965 to present, Dr. Pierce has mapped glacial deposits, pioneered Quaternary dating techniques, conducted research on the Yellowstone Hot Spot, studied the geothermal areas, explored the geology of archaeological sites

January 22, 2014

The Yellowstone Volcano: Past, Present and Future

Public Lecture on Yellowstone Volcano by Jake Lowenstern at Menlo Park, CA on January 23, 2014. The Q&A at the end of the talk can be found on the original source video (Source URL).

September 28, 2010

Caldera Demonstration Model

A caldera is a large, usually circular volcanic depression formed when magma is withdrawn or erupted from a shallow underground magma reservoir. It is often difficult to visualize how calderas form. This simple experiment using flour, a balloon, tubing, and a bicycle pump, provides a helpful visualization for caldera formation.

video thumbnail: Yellowstone Volcano Observatory (Part 2 of 3)
January 29, 2009

Yellowstone Volcano Observatory (Part 2 of 3)

USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers
the following questions to provide a tour of the Yellowstone Volcano Observatory: "What is YVO?", "How
do you monitor volcanic activity at Yellowstone?", "How are satellites used to study deformation?", "Do
you monitor geysers or any other aspect of the Park?", "Are

video thumbnail: Yellowstone Eruptions (Part 3 of 3)
January 29, 2009

Yellowstone Eruptions (Part 3 of 3)

USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers
the following questions to explain volcanic eruptions at Yellowstone: When was the last supereruption at
Yellowstone?", "Have any eruptions occurred since the last supereruption?", "Is Yellowstone overdue for
an eruption?", "What does the magma below indicate about a

video thumbnail: Yes! Yellowstone is a Volcano (Part 1 of 3)
January 29, 2009

Yes! Yellowstone is a Volcano (Part 1 of 3)

USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers
the following questions to explain volcanic features at Yellowstone: "How do we know Yellowstone is a
volcano?", "What is a Supervolcano?", "What is a Caldera?","Why are there geysers at Yellowstone?",
and "What are the other geologic hazards in Yellowstone?"