Is the Super Volcano Beneath Yellowstone Ready to Blow?

About 4 miles beneath Yellowstone National Park's beautiful scenery is a forty-mile-wide chamber full of molten rock under incredibly high pressure. This magma is what powers Yellowstone's fantastic geysers and hot springs, but is it about to erupt in a cataclysmic explosion that will decimate the western United States and push mankind to the brink of extinction?

Yellowstone is the crown jewel of the United States national park system. Its mountain vistas, wildlife and geographic features are visited and admired by people from around the world. More than any of those, however, it's the park's thermo-geological features that make it unlike any other part of the globe. No place on earth has as many steam vents, hot springs and active geysers as Yellowstone.

To create these features requires two elements in abundance: lots of water and lots of heat. The water is provided by the generous rain and snow the region gets. The heat comes from deep inside the earth: volcanic heat. Though you might not be able to tell from just looking at it, Yellowstone National Park is built on an ancient volcano. Not just a regular volcano, either. It lays on top of what some people have started to call a "super volcano."

Super Volcanos

There is no exact definition for a super volcano, but the term is often used to refer to volcanos that have produced exceptionally large eruptions in the past. When one of these large eruptions occurs, a huge amount of material is blasted out of the super volcano, leaving a giant crater or caldera. Such a caldera can be as much as forty or fifty miles wide. At Yellowstone, the caldera is so big that it includes a fair amount of the entire park. In fact, it is so big that scientists confirmed that the region had a caldera by looking at photographs from space.

Since there is no firm definition of what a super volcano is, it's hard to say how many of them are found on the earth. Usually people list Long Valley in eastern California and Taupo in New Zealand as super volcano sites along with Yellowstone. The last known explosion of what might be considered a super volcano was Toba in Indonesia. Toba erupted with a titanic explosion about 74,000 years ago. The force of the explosion was estimated to be 10,000 more powerful than the blast that destroyed Mount St. Helens, in Washington. Tremendous amounts of rock and ash were ejected into the air, blocking the sun for months. The temperature around the globe was thought to have plummeted as much as 21 degrees. Perhaps as much as 75% of plant life on the North American continent may died out.

A super volcano differs from a regular volcano in that there is often no mountain peak associated with it. In a regular volcano hot magma under pressure flows up from the depths of the earth. A hole forms in the surface and the magma, now lava, pours out. As it cools, it forms a cone that eventually builds up into a mountain. If the passage is blocked off, the pressure can build up in the mountaintop and explode with a monstrous force. That's what happened at Mount St. Helens. The pit formed by the explosion becomes the new caldera.

In a super volcano the magma is blocked from ever reaching the surface. Instead, the pressure just builds and builds until more and more rock in the area melts and becomes magma too. The area under the surface becomes one huge underground sea of semi-molton rock. Finally, the pressure becomes too much to hold back and the entire surface above the underground chamber, which can be many miles wide, is blown away by a titanic explosion that can be thousands of times more powerful than that of a regular volcano.

Yellowstone's Catastrophic Eruption

This last happened at the Yellowstone volcano approximately 650,000 years ago. The caldera that it left is 53 miles long and 28 miles wide. In the area surrounding Yellowstone, 3000 square miles were subjected to a flow of pyroclastic material composed of 240 cubic miles of hot ash and pumice. Ash was also thrown into the atmosphere and blanketed much of North America. It can still be identified in core samples from as far away as the Gulf of Mexico.

Since this occurred more than a half million years ago this is all ancient history, right? Not quite. Yellowstone continues to be geologically active even today. Smaller explosions caused by hydrothermal activity (water or steam heated in an underground chamber until the top blows off) have been much more common and recent in Yellowstone's history than the massive caldera-forming eruptions. One of these happened as recently as 13,000 years ago, creating a three-mile wide crater that is now a portion of Yellowstone Lake called Mary Bay. Also, smaller volcanic eruptions with flows of lava, ash and pumice have occurred. Flows like these have filled in much of the old caldera since its creation.

Another catastrophic eruption is also possible. The effects of such a disaster are hard to even comprehend. Bill McGuire, professor of geohazards at the Benfield Greig Hazard Research Centre at the University College of London told the UK Daily Express, "Magma would be flung 50 kilometers into the atmosphere. Within a thousand kilometers virtually all life would be killed by falling ash, lava flows and the sheer explosive force of the eruption. One thousand cubic kilometers of lava would pour out of the volcano, enough to coat the whole USA with a layer 5 inches thick." He adds that it would once again bring "the bitter cold of Volcanic Winter to Planet Earth. Mankind may become extinct."

Reasons to Worry?

Scientists have known about Yellowstone's explosive history for quite some time, but events in the fall of 2003 suddenly had people concerned about the possibility of another massive explosion.

In August of 2003 a new high-resolution sonar map of the bottom of Yellowstone Lake showed a bulge, or "inflated plain" there that was 2000 feet long and 100 feet high. Was it being pushed up by hydrothermal or even volcanic forces?

At about the same time there were some unusual changes at Norris Geyser basin some 20 miles north of the lake. Areas formally dry suddenly had hot springs. Other hot springs dried up. A long dormant geyser became active and forced the closing of some of the trails through the basin.

A report released in December of 2010 further raised concerns. Scientists published a study in the Geophysical Research Letters entitled "An extraordinary episode of Yellowstone caldera uplift, 2004-2010," that showed that the caldera had risen 7 centimeters a year between 2004 and 2006.

Some amateur geologists connected these events with the history of the Yellowstone volcano and came to some troubling conclusions: The catastrophic caldera making eruptions have occurred. at 2.1 million, 1.3 million and 650,000 years ago. Was another one about to happen? Was the next explosion overdue? Interest in these developments quickly mounted. Several Internet sites sprang up predicting another explosion very soon and suggesting that the only way to avoid such a disaster was to drill holes into the magma chamber to release the pressure. In a January 2011 interview City University of New York physicist Michio Kaku said, "It's black magic trying to predict exactly when it's going to blow, but we do know one thing: one day it will blow" and "…all you can do is run."

Conditions Normal

As fascinating as the history of Yellowstone volcano is, however, most professional geologists who study the site are not concerned that the park is on the brink of a catastrophic eruption. The bulge on the bottom of the lake may have been there for thousands of years, but not noticed until the recent survey. Changes in the geyser activity is not unusual. New geysers have appeared throughout the history of the park, while others go dormant. Rangers often shut down parts of trails or alter them as needed.

The land near the center of the caldera did rise more than three feet between 1923 and 1985. However, between 1985 and 1992 it actually subsided six inches. Studies of the shorelines of Yellowstone Lake have led scientists to believe this is a regular phenomenon. The caldera floor has risen and fallen at least three times in the last 10,000 years, moving as far as 65 feet.

An author of the 2010 study,Bob Smith of the University of Utah, said "At the beginning we were concerned it could be leading up to an eruption, but once we saw [the magma] was at a depth of ten kilometers [six miles], we weren't so concerned. If it had been at depths of two or three kilometers [one or two miles], we'd have been a lot more concerned."

Yellowstone Volcano Observatory in a statement in 2011 added, "Geological activity over the past five years includes widespread ground uplift and two notable earthquake swarms. Though scientifically interesting, such events are common in large caldera systems like Yellowstone, and are not indicative of an imminent eruption."

The idea that Yellowstone may be "overdue" is also faulty. With only three catastrophic eruptions and two intervals between to go on there is not enough data to say that another one should be occurring in the near future.

Even if there was, there is little mankind could do about it. Drilling into the magma chamber to release pressure, as some have suggested, would be impractical and ineffective. The material in the chamber has the consistency of a sponge and any "hole" opened up to the surface would quickly seal as the molten rock crept up and cooled.

The Sleeping Dragon

That doesn't mean that there isn't (as one scientist put it) a proverbial giant dragon sleeping under Yellowstone. It may well one day awake and lay waste to much of the western United States. The Yellowstone Volcano Observatory, however, watches the park carefully and analyzes the continuous geological changes occurring in the region. It is likely that the imminent threat of another catastrophic explosion would not go unnoticed by their modern instruments. So far, however, activity is business-as-usual at the park.

Still, the super volcano at Yellowstone, and its kin around the world are a credible threat to man. Even the United States Geological Survey, usually conservative about such matters, admits that should a major eruption occur the results would have "global consequences that are beyond human experience and impossible to anticipate fully."

A Partial Bibliography

Yellowstone: Restless Volcanic Giant, by Daniel Dzurisin, Robert L. Christiansen, and Kenneth L. Pierce, USGS Report, http://vulcan.wr.usgs.gov/Volcanoes/Yellowstone/OFR95-59/OFR95-59.html, 1995.

Yellowstone Volcano Observatory Future Volcanic Activity FAQ, http://vulcan.wr.usgs.gov/yvo/faqs4.html, 1995.

A Monster Awakens?, by Ian Gurney, Online Journal, http://www.onlinejournal.com/Special_Reports/091103Gurney/091103gurney.html. September 11, 2003.

Scientists' Interest Bubbling, by Scott Canon, Knight Ridder News Service/Philadephia Inquirer, November 27, 2003

Copyright 2011 Lee Krystek. All Rights Reserved.