World's tallest geyser erupts

Steamboat: First major eruption since 1991

By BBC News Online science editor Dr David Whitehouse

The world's tallest active geyser burst back into life this week.

Campers thought it was an earthquake

The geyser at the Yellowstone National Park in the United States, threw up a giant column of hot water and steam at about 0500 hrs on Tuesday.

It is the first time in nine years that Steamboat, as it is affectionately known, has erupted in a major way.

Two park visitors, sleeping nearby in their camper van, said they were abruptly awakened by what they thought was an earthquake.

They were frightened by what had happened and drove south toward Madison. Only when they looked back did they see the huge vapour plume and decided to return to the geyser basin.

Tremendous roar

By the time a park employee had arrived on the scene, a dense wet mist had enveloped most of the area around the geyser. Steamboat was said to be emitting a tremendous roar and to have pushed a vapour plume 150 metres (500 feet) into the air.

Experts say that Steamboat Geyser rarely erupts this dramatically. More commonly, it ejects water in frequent bursts of 3-12 metres (10-40 feet) in height. Most major eruptions will go over 90 metres (300 feet), showering viewers with mineral-rich waters.

But this is an extremely rare event. Steamboat was dormant from 1911-1961. In recent years, it has erupted in 1989 (3 times), 1990 (1 time), and 1991 (1 time).

There are hundreds of geysers at Yellowstone, more than in any other part of the world.

The most famous is Old Faithful which throws up a column more than 30-metres (100-feet) high every hour or so.