Mount Spurr, an ice- and snow-covered volcano about 125 km (80 miles) west of Anchorage, has grown restless in recent months, and hundreds of small earthquakes have occurred deep beneath its summit. A circular melt pit in the summit ice cap has opened, suggesting the presence of volcanic heat. The increased seismicity, heat, and volcanic gas emissions most likely indicate that new magma has risen into Mount Spurr. But not all magmatic intrusions lead to eruptions. At Mount Spurr, scientists will race the onset of winter to add instrumentation over the next several weeks to increase their monitoring capabilities. The only two historical eruptions of Mount Spurr, in 1953 and 1992, were from Crater Peak vent on the south flank of the volcano. These eruptions were relatively small but violent. In 1992, volcanic ash blanketed south-central Alaska and forced the closure of Anchorage International Airport for 20 hours. The effects were felt well beyond Alaska as the ash cloud drifted across the continental United States and Canada, shutting down airports in the Northeast and Midwest two days after the eruption. The north Pacific air routes connecting Alaska to the Far East carry more than 10,000 people per day over one of the most active volcanic areas in the world. Alaska has over 100 volcanoes, and over 40 of these have been active in historic time. For updates and images see http://www.avo.alaska.edu/avo4/atlas/volc/spurr/spurr2004/index.html. For more, contact Carolyn Bell at 703-648-4463 or cbell@usgs.gov.
