for National Geographic News
A massive fin-shaped slab of hot rock has recently been seen growing in the crater of Washington State's Mount St. Helens.
The feature is the seventh such structure to rise in the volcano's crater since it began slowly erupting in October 2004, say scientists with the U.S. Geological Survey's (USGS) Cascade Volcano Observatory.
Clear skies following a long, cloudy, wet winter in the U.S. Pacific Northwest recently lifted the veil on this latest formation.
"This one has created a stir, in part because it began to emerge in the dead of winterin the middle of November '05," said Daniel Dzurisin, a volcanologist at the Vancouver-based observatory who studies the dome.
"It was a particularly snowy winter in the Northwest. We didn't get many views, and we hadn't seen this feature before recently."
The newest creation currently stands about 300 feet (90 meters) tall and is 330 feet (100 meters) wide at the base, Dzurisin says.
The feature is growing at a rate of 4.6 feet (1.4 meters) a day.
Some past features looked like this fin, while others looked more like whaleback spines.
All of them eventually reached a maximum size, broke apart, and were shoved aside by the next feature.
The current fin is destined to meet a similar fate.
"It's an unstable column of rock. It will likely fall apart," Dzurisin said.
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