Alaska Volcano Observatory (AVO) Warns of Possible New Volcano Activity

Anchorage, Alaska (HDW) July 26, 2004 - Alaska Volcano Observatory (AVO) has identified an increase in earthquake activity beneath the summit of Mount Spurr volcano located about 130 km (80 mi) west of Anchorage. Some of these earthquakes can be interpreted to reflect the beginning stages of volcanic unrest. Because this is a notable departure from the normal background seismicity of the volcano, AVO is raising the level of concern color code to YELLOW. However, there are no indications that an eruption is imminent. Often this type of seismicity will decline without producing an eruption.

Retrospective analysis suggests that the current increase began slowly, perhaps as early as February 2004. At present, AVO is locating 15-20 earthquakes below the volcano each day. This is a rate greater than any observed since the last eruptive period in 1992. All earthquakes are less than magnitude 1.5 and range in depth between 1 and 6 km (0.6 and 4 miles) below sea level. To date, relatively few earthquakes have been located beneath the Crater Peak vent, the site of the 1953 and 1992 eruptions. The current earthquake activity differs markedly from that seen prior to the 1992 eruption, which started with a small cluster of earthquakes directly beneath Crater Peak nearly a year before the eruption began. Recent volcanic activity tracked by the AVO in the Russian Kamchatka Peninsula (volvanos Shiveluch, Sheveluch, and Bezymianny are shown being active in early 2004 in the picture above) near to Alaska, give fear to large volcanic plumes which can disrupt over flying air traffic.

AVO geologists visited Spurr by fixed-wing aircraft on July 15 and observed no indications of recent volcanic activity. On July 11, a pilot flying by the volcano reported a sulfur smell and new area of steaming, but neither was noted during the AVO flight, although a significant portion of the Crater Peak area was obscured by low clouds. AVO geologists did document several fresh-looking, dark debris flow/avalanche deposits on the southeast and south face of the summit dome complex suggesting water flow at the surface, but this may simply reflect recent unseasonably warm and sunny conditions.