In recent years, much public attention has focused on the fact that Yellowstone sits astride one of the world's largest active volcanic systems.  Questions routinely arise in regards to the likelihood of a volcanic eruption in Yellowstone and the impact of such an eruption.

It is true that earthquakes are a daily occurrence in the Yellowstone region, yet most are under 3.0 magnitude, and very few are actually felt.  However, there is little to worry about in terms of actual danger at this time.

According to the United State Geological Survey, "Yellowstone has produced several giant volcanic eruptions in the past few million years, as well as many smaller eruptions and steam explosions. Although no eruptions of lava or volcanic ash have occurred for many thousands of years, future eruptions are likely. In the next few hundred years, hazards will most probably be limited to ongoing geyser and hot-spring activity, occasional steam explosions, and moderate to large earthquakes. To better understand Yellowstone’s volcano and earthquake hazards and to help protect the public, the U.S. Geological Survey, the University of Utah, and Yellowstone National Park formed the Yellowstone Volcano Observatory, which continuously monitors activity in the region."

Below is a USGS map of volcanic and seismic history in the Yellowstone region (you may click on the map for a larger version):

Historically, four types of volcanic events have taken place in Yellowstone (you may click on each one to learn more):

1.  Caldera Forming Eruptions -- 2.1 and 1.3 million years ago
2.  Lava Flows -- about 30 between 640,000 and 70,000 years ago
3.  Earthquakes -- 1000 to 3000 yearly; last notable quake was in 1959
4.  Hydrothermal (Steam) Explosions -- small explosions in the 20th century; a
     dozen or so major explosions between 14,000 and 3,000 years ago

According to the USGS, none of these events are common in Yellowstone. Although visitors to Yellowstone National Park in the immediate future may never experience such events, some hazardous events are certain to occur in the future. However, Yellowstone Volcanic Observatory scientists are monitoring volcanic activity in the region in an effort to alert the public well in advance of any major volcanic eruptions, to ensure public safety.

Yellowstone's Geysers are a result of the volcanic activity.