Mt. Fitzherbert

The recent "extraordinary" behaviour of one of the world's most notorious volcanoes, Mount St Helens in the US, may mean it is preparing for a dramatic eruption, geologists warned on Tuesday.

In late September 2004, a series of earthquakes signalled that the volcano was awakening. Since then, enough lava has oozed into the volcano's crater to build a dome the size of an aircraft carrier. The new dome, standing 275 metres off the crater floor at its highest point, is now taller than a nearby dome built by a previous set of eruptions over the course of six years.

"Something extraordinary is happening at Mount St Helens. We are scratching our heads about it," says Dan Dzurisin of US Geological Survey's Cascades Volcano Observatory (CVO) in Vancouver, Washington, US. The new dome has grown so quickly - almost four cubic metres every second - that it has bulldozed a 180-metres-thick glacier out of its way.

VANCOUVER, Wash. - A new lava dome growing in the crater of Mount St. Helens is about one-third the size of the old lava dome.

The U.S. Geological Survey says since fresh magma started pushing into the mountain in October the new structure is about 1,600 feet long, 650-feet wide and 900 feet high.