Mount St. Helens rumort

[Angie]

Nächstes Update:

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Mount St. Helens updates
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08 Nov 04 MSH Update
 
MOUNT ST. HELENS VOLCANO
Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE

Growth of the new lava dome inside the crater of Mount St. Helens continues, and is accompanied by intermittent emissions of steam and ash.
As long as this eruption is in progress, episodic changes in the level of activity can occur over days, weeks, or even months. Increase in the intensity of eruption could occur suddenly or with very little warning and may include explosive events that produce hazardous conditions within several miles of the volcano. Small lahars (volcanic debris flows) could suddenly descend the Toutle River valley if triggered by heavy rain or by interaction of hot rocks with snow or glacier ice. These lahars pose a negligible hazard below the Sediment Retention Structure (SRS) but could pose a hazard to people along the river channel upstream of the SRS. At this time of year, it is not unusual for rivers draining the volcano to contain high concentrations of sediment that turn the water murky.
Although considered less likely at this time, the current eruptive activity could evolve into a more explosive phase that affects areas farther from the volcano and sends significant ash thousands of feet above the crater where it could be a hazard to aircraft and to downwind communities.

Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), coupled with eruption models, show that ash clouds that rise above the crater rim today would drift northward to northeastward depending on their altitude.

Visibility is excellent and likely will remain so throughout the day.  A steam plume is rising passively and drifting northward out of the crater. The plume occasionally contains minor ash, which falls out in the crater and on the flank of the volcano, darkening the snow.

Seismicity remains at a low level compared to that observed early in this unrest.  The current seismicity is consistent with a continuing, slow rise of magma driving uplift of the crater floor and feeding a surface extrusion of lava.  The overall low rates of seismicity and gas emission suggest that the lava reaching the surface is gas poor, thereby reducing the probability of highly explosive eruptions in the near term.

Aerial observations yesterday showed that the new dome continues to expand and move upward.  Small aprons of rockfall debris are accumulating at several sites around the new dome.  Some ash emissions may be caused by these rockfalls as collapsing hot dome lava disintegrates into smaller fragments.  No field investigations are planned for today.

see also:
http://story.news.yahoo.com/news?tmpl=story&cid=519&e=15&u=/ap/mount_st__helens


Viele Grüße,
Angie

[Angie]

MOUNT ST. HELENS UPDATE

   Current Volcano Alert Level WATCH ; Aviation Color Code ORANGE : Growth
   of the new lava dome inside the crater of Mount St. Helens continues,
   accompanied by low rates of seismicity, low emissions of steam and
   volcanic gases, and minor production of ash. During such eruptions,
   changes in the level of activity can occur over days to months. The
   eruption could intensify suddenly or with little warning and produce
   explosions that cause hazardous conditions within several miles of the
   crater and farther downwind. Small lahars could suddenly descend the
   Toutle River if triggered by heavy rain or by interaction of hot rocks
   with snow and ice. These lahars pose a negligible hazard below the
   Sediment Retention Structure (SRS) but could pose a hazard along the
   river channel upstream.

   Potential ash hazards: Wind forecasts from the National Oceanic and
   Atmospheric Administration (NOAA), coupled with eruption models, show
   that any ash clouds rising above the crater rim today would drift
   southeast.

   Potential ash hazards to aviation: Under current eruptive conditions,
   small, short-lived explosions may produce ash clouds that exceed 30,000
   feet in altitude. Ash from such events can travel 100 miles or more
   downwind.

   Recent observations: Mount St. Helens is hidden by clouds this morning.
   Weather forecasts for Columbus Day indicate sunny weather and excellent
   opportunities to view the crater. Data from deformation-monitoring
   instruments located on the 1980-86 and 2004-2006 lava domes indicate
   that extrusion of the new lava dome continues, despite relatively low
   seismicity levels. Mount Rainier's M 4.5 earthquake at about 7:50 PM
   last night registered on the Mount St. Helens seismic network