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

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/yellowstone-supervolcano-4160977

VOLCANIC ASHFALL HAZARD - Ashfall is the most widespread and frequent volcanic hazard. Ashfall rarely endangers human lives, but it can have devastating effects on the things that we rely upon from day to day. As a result of its fine-grained abrasive character and widespread distribution by wind, ashfall and volcanic ash clouds are a major hazard to aviation. Ash fallout to the ground can pose significant disruption and damage to buildings, transportation, water and wastewater, power supply, communications equipment, agriculture, and primary production leading to potentially substantial societal impacts and costs, even at thicknesses of only a few millimetres or inches. Fine grained ash, when ingested can cause health impacts to humans and animals.

Ash buries cars and buildings after the 1984 eruption of Rabaul, Papua New Guinea.

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Ash deposits inside the jet engine that
encountered the ash cloud from
Redoubt Volcano on 15 December 1989.

Volcanic Ashfall Hazard

Ashfall is the most widespread and frequent volcanic hazard

USGS Volcano Hazards Program

Explosive eruptions produce ash.

All explosive volcanic eruptions generate tephra, fragments of rock that are produced when magma or rock is explosively ejected.

The largest fragments, blocks and bombs (>64 mm, 2.5 inches diameter), can be expelled with great force but are deposited near the eruptive vent.

Lapilli-sized material (6-64 mm, 0.24-2.5 inches diameter) can be carried upward within in a volcanic plume and downwind in a volcanic cloud, but fall to the ground as the eruption cloud cools.

The smallest material, volcanic ash (<2 mm diameter) is both easily convected upward within the plume and carried downwind for very long distances; as it falls out of suspension it can potentially affect communities and farmland across hundreds, or even thousands, of square kilometers (miles).

Ash endangers aviation and infrastructure.

Ashfall rarely endangers human lives, but it can have devastating effects on the things that we rely upon from day to day.

As a result of its fine-grained abrasive character and widespread distribution by wind, ashfall and volcanic ash clouds are a major hazard to aviation.

The primary hazard from Alaska volcanoes is ash clouds impacting aviation and ashfall reaching areas downwind, owing to widespread dispersal by wind.

Ash fallout to the ground can pose significant disruption and damage to buildings, transportation, water and wastewater, power supply, communications equipment, agriculture, and primary production leading to potentially substantial societal impacts and costs, even at thicknesses of only a few millimetres or inches.

Additionally, fine grained ash, when ingested can cause health impacts to humans and animals.

Impacts from ashfall are more complex and multi-faceted than for any of the other volcanic hazards.

Variabilities include the distance from the eruption source, orientation and dispersion of the eruption cloud, the amount of ashfall received, physical and chemical properties of the ash, characteristics of the receiving environment (such as climate and land use), and the ability of affected community to adapt to ashfall.

The USGS sponsored Volcanic Ashfall Impacts Working Group offers resources and guidance for ashfall preparedness and impact.

https://volcanoes.usgs.gov/vhp/tephra.html

Ash covered the pasture reducing livestock access to feed in Futaleufú following the 2008 Chaitén eruption.