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Mt. St. Helens awoke Tuesday afternoon with a mild eruption, spewing a plume of steam and ash into the Washington State sky.
The event was most probably was caused by growth of the new lava dome inside the crater, experts said.

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Expand (2.14mb, 2288 x 1712)
Credit: Dan Dzurisin, Cascades Volcano Observatory, USGS

A new rock slab is growing at more than one meter a day on the Mt. St. Helens volcano in Washington, USA. The rock slab, growing since last November, now extends about 100 meters out from one of the volcano's craters.

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Latitude 46.198510 longitude -122.190391


Webcam pointing at Mount St. Helens from the Johnston Ridge Observatory

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The Cascades Volcano Observatory is reporting that a large fin has developed in the mile-wide Mount St. Helens crater, the result of lava upsurges.

Scientists say they expect the 300-foot-tall spire -- the size of a tilted-up football field -- to collapse into the crater's expanding dome, as others have since the volcano began erupting again 18 months ago.
The tip of the fin is about 7,698 feet above sea level, boosted by the volcano's rising lava dome. The lava has been emerging from a crater vent at a rate of 1 to 2 metres a day.

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A large part of the growing lava dome on Mount St. Helens fell Saturday, sending an ash plume above the crater rim.

A rock fall had caused what scientists called a "substantial seismic signal'' and knocked the chunk off the lava dome, which rises from within the main crater that was created in the mountain's historic eruption in 1980. The volcano was relatively quiet for the rest of the day.

"Otherwise, the volcano remains relatively quiet and there are no significant changes in seismicity or deformation" - USGS statement.


An image of the dome taken June 30.

The USGS and the University of Washington have monitored the volcano closely since it rumbled back to life Sept. 23 with shuddering seismic activity that peaked above magnitude 3 as hot magma broke through rocks in its path.
Molten rock reached the surface Oct. 11, marking resumption of dome-building activity that had stopped in 1986.
On March 8, it shot ash higher than 30,000 feet, but it has since maintained low-key activity, with wispy smoke regularly floating from the crater.

Scientists have said a more explosive eruption, possibly dropping ash within a 10-mile radius of the crater, is possible at any time.
The lava dome had built to a point some 500 feet taller than before the spate of eruptions began last fall. But in recent weeks it has been crumbling, and scientists said it was probably lower than its peak but had not recently been measured.

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