Volcano Information

    Mount St. Helens
    Volcanic Alert Level: NORMAL Aviation Color Code: GREEN

    • Current Update, last updated Aug 1, 2008 04:11 PDT:
      The 40-month-long lava-dome eruption of Mount St. Helens that began in autumn 2004 ended in late January of this year. Earthquakes, volcanic gas emissions, and ground deformation are all at pre-eruptive background levels. The alert level and aviation color code were reduced to NORMAL/GREEN on July 10, 2008, following five months with no sign of renewed activity.

      Even with the end of lava dome growth, some hazards persist. The new lava dome remains hot in places and capable of producing small hot avalanches or minor explosions that could dust areas with ash up to tens of miles downwind. Rock fall from the crater walls can produce clouds of dust that rise above the crater rim, especially during dry, windy days, as has happened in the past. Also, heavy rainfall or rapid snowmelt can send small debris flows onto the Pumice Plain north of the crater.


      Recent observations:
      This week field crews made repairs to monitoring equipment, deployed photo targets for geodetic control points, continued tracking northward advance of Crater Glacier, and mapped geology on the volcano's flank. Scientists from the Cascades Volcano Observatory continue to monitor the volcano remotely. The past week's seismic record is dominated by rockfalls in the crater and glacier quakes caused by motion of the ice.



    • Volcanic History Overview: Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but few lava flows extended beyond the base of the volcano. The modern edifice was constructed during the last 2200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.
    • Location: Western US, WA

      Latitude: 46.2
      Longitude: -122.18
      Elevation: 2549 m

      Recent Eruption: Ongoing current eruption cycle.
    • Hazard Assessments: Wolfe and Pierson, 1995, Volcanic-Hazard Zonation for Mount St. Helens, Washington, USGS Open-File Report 95-497.
    • Link to monitoring data: CVO Web Site Volcano Monitoring