Yellowstone National Park/Super Volcano
Cheryl Kalman

Many people visit Yellowstone National Park every year to go hiking, to enjoy the wild life, or to see the famous geysers. What most people don’t know about Yellowstone is that is sits on top of a super volcano.
The way a super volcano differs from a regular one is first, there is no mountain peak. In a regular volcano when lava pours out and cools it creates a cone which builds up the mountain. If the lava passage is blocked off pressure builds and this causes an eruption. In a super volcano the magma never reaches the surface. Pressure just builds until it melts more rocks which becomes more magma. When the pressure becomes too much the entire surface above the magma chamber is blown off causing an eruption thousands of times larger than normal volcanoes. When these eruptions occur a huge amount of material is thrown out of the volcano, leaving a giant crater called a caldera. The Caldera at Yellowstone is so large it can be seen from space.
The last time Yellowstone had an eruption of that magnitude was 650,000 years ago. The caldera it left is 53 miles long and 28 miles wide, that’s roughly the size of the Los Angeles Basin. 3,000 square miles were subjected to a flow of pyroclastic material containing 240 cubic miles of hot ash and pumice. Ash was also thrown in to the atmosphere which blanketed most of North America.
So what would happen if another catastrophic eruption took place today? Bill McGuire, professor of geohazards at the Benfield Greig Hazard Research Centre at the University College of London said "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 […] the bitter cold of Volcanic Winter to Planet Earth. Mankind may become extinct."
Many recent events at Yellowstone have caused people to worry about another eruption. First, in August 2003 a high resolution sonar map showed a bulge, 2,000 feet long and 100 feet high at the bottom of Yellowstone Lake. Second, at about the same time, areas that were formerly dry suddenly had hot springs and a long dormant geyser became active again forcing some of the parks trails to be closed down. Lastly in the mid 1970’s Robert Smith, a geophysicist at the University of Utah found that the ground had risen 3 feet in 5 decades. The caldera continued to rise an inch a year until 1985 when it began falling an inch a year. However, in 1995 the caldera once again stated bulging towards the southwest.
But is this any reason to worry? Geologists say no. The bulge on the bottom of the lake could have been there for thousands of years but not discovered until this new high resolution camera was developed. Changes in geysers are normal, and rangers often shut down trails as needed. As for the caldera floor, it has risen and fallen at least three times in the last 10,000 years.
Studies done by a research team at the University of Wisconsin analyzed crystals within hardened lava and concluded that the super volcano in Yellowstone is dying, but still in a potent cycle of volcanism. Some people believe the hot spot is moving under the Rocky Mountains and because it is a colder thicker part of the continent it will be capped, while others believe this won’t stop the force of this super volcano.
Smith and Robert Christiansen of the U.S. Geological Survey say they are not sure what this will do but they the volcano is not dead and there is no reason it won’t blow again.
Christiansen says he doubts the likelihood of another cataclysmic eruption soon, but because there have only been three catastrophic eruptions in the past there is not enough data to tell when the next one will occur. He suggests a blowout on the scale of Mount St. Helens is possible adding “we need to be prepared.”
Until then, the Yellowstone Volcano Observatory keeps a close eye on continuous geological changes happening in the park. It is unlikely that today’s modern instruments would not pick up on the threat of an eruption. Right now however, activity in the park is “business-as-usual.”
References: http://www.unmuseum.org/supervol.htm, http://news.nationalgeographic.com/news/2001/08/0828_wireyellowstone_2.html
Geology and Earth Science