Hydrothermal explosion

A hydrothermal explosion is the process in which water rapidly converts from its liquid to boiling state causing an explosion. Hydrothermal explosion activity drives geothermal activities such as geysers.

Cause of explosion

Water usually boils at 100 degrees Celsius but under increasing pressure the boiling point increases. If very hot liquid water confined under pressure is released from that pressure, pockets of water boil very suddenly and quickly; in this change of state an explosion is often caused, hence hydrothermal explosions.

Yellowstone

It is estimated that the temperature of the magma reservoir below Yellowstone exceeds 800 degrees Celsius causing the heating of rocks in the region. If so, the average heat flow supplied by convection currents is 30 times greater than anywhere in the Rocky mountain range. Snowmelt and rainfall seep into the ground at a rapid rate and can conduct enough heat to raise the temperature of ground water to almost boiling. The phenomena of geyser basins are the product of such extraordinary events; hot ground water rising close to the surface, and sometimes even bubbling through. Water temperatures of 238 degrees Celsius at 332 meters have been recorded at Norris Geyser Basin.

Geysers

One well-known hydrothermal geyser is Old Faithful which throws up plumes of steam and water approximately every half an hour. Rarely has any steam explosion violently hurled water and rock thousands of feet above the ground; however in Yellowstone’s geological history these colossal events have been recorded numerous times and have been found to have created new hills and shaped parts of the landscape.

The largest hydrothermal explosion ever documented was located near the northern edge of Yellowstone Lake, on an embankment commonly known as “Mary Bay”. Now consisting of a mere 1.5 mile crater, it was formed relatively recently, approximately 13,800 years ago. It is believed this crater was formed by a sequence of several hydrothermal explosions in a short time. What triggered this series of events has not been established, but volcanologists and scientists believe a large earthquake could have played a role by accelerating the melting of nearby glaciers. Alternatively, rapid changes in the level of Yellowstone Lake may have been responsible.

Recent explosions

Most of Yellowstone’s recent large hydrothermal explosions have been the consequence of sudden changes of pressure deep within the hydrothermal system. Generally, these larger explosions have created craters in a north-south pattern (between Norris and Mammoth Hot Springs). It is estimated that all the hydrothermal craters seen now were created between 14,000 and 3,000 years ago. Volcanologists believe no magma has ever broken through the fragile crust of Yellowstone Park or stirred the movement of magma in the reservoir beneath Yellowstone. These phenomena are now considered to be mutually exclusive events; hydrothermal explosions are not correlated with volcanism, although throughout the world all hydrothermal systems are heated and caused by magma.

References

* [http://www.solcomhouse.com/yellowstone.htm Supervolcano Yellowstone ]

External links

* [http://pubs.usgs.gov/fs/2005/3024/images/fs2005-3024_fig_09.jpga photo of a Hydrothermal explosion]