Hydrothermal Activity at Yellowstone

Besides the animals, what really helps make Yellowstone so wonderful are all the signs of the volcanic activity and hydrothermal activity that occur in the park.  The Yellowstone area is the largest volcanic system in North America.  The US Geological Service maintains an observatory to provide timely monitoring and hazard assessment of the volcanic, hydrothermal, an earthquake activity in the Yellowstone Plateau region.  Earthquakes do occur regularly in the area but the last major abruption occurred more than 70,000 years ago, but the most current activity are hydrothermal explosions.
The Yellowstone Caldera, sometimes known as the Yellowstone Supervolcano, is located in the northwest corner of Wyoming, where the vast majority of the Park is located.  It measures about 34 x 45 miles.

Map of the Yellowstone Caldera

The USGS host a new geologic information tool to help anyone learn more about the geology and other features of the site, internet map service for the Yellowstone Plateau area http://vscmaps.wr.usgs.gov/yellowstone
Everything, from Old Faithful, all the other geysers, Hot Springs, and mud holes are a result of the underlying volcanic activity.

.Of course,the most famous geyser is Old Faithfull, since it is the most predicable geyser and everyone that comes to Yellowstone usually visits it.

There are even more spectacular geyser eruptions, in fact one occurred while I was photographing Old Faithfull.  I was in the wrong location and needed a longer lens to capture that one which occurred in the Castle Geyser area.
The colors and beauty of all the areas are worth viewing and enjoying