Activity at Alaska’s Mount Redoubt caused rapid changes on the nearby landscape in early April 2009. This pair of images acquired by the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite shows the area around the volcano on April 1, 2009 (top), and April 4, 2009 (bottom). These images show the area immediately east of the volcano, between Mount Redoubt and Cook Inlet. (In these images, north is to the right.)
In the image acquired on April 1, 2009, nearly the entire area northeast of the volcano is charcoal brown, coated with a layer of volcanic ash. The river channel that connects with Cook Inlet is barely discernible given the surrounding ash-covered landscape. A plume from the volcano blows toward the east.
In the image acquired April 4, 2009, a plume still blows toward Cook Inlet, but the landscape has changed. Fresh snowfall has apparently buried the previous coating of volcanic ash. Extending from the volcano (just off the top edge of the image) toward the northeast, the Drift River Valley appears in deep brown, thanks to a recent lahar. South of the river valley, however, a triangular-shaped patch of land now appears brilliant white, thanks to fresh snow. Local snow cover actually preserved a sequence of alternating snow and ash layers in early April 2009, as a picture on the Volcanism Blog shows.
Unlike the soft material resulting from burned vegetation, volcanic ash consists of tiny shards of rock and glass. Dangerous to inhale, volcanic ash is also mildly corrosive and able to conduct electricity when wet. Too tough to dissolve in water, this ash can be preserved in snow and ice for centuries. Geologists also use ancient volcanic ash layers to calculate the ages of rock strata.
NASA image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 Team. Caption by Michon Scott.
After keeping volcanologists waiting for weeks, Mount Redoubt erupted five times in one night, beginning on March 22, 2009. The volcano followed up with more eruptions in April, and showed continued signs of unrest in early May.
References & Resources
U.S. Geological Survey. (2009, February 3). Volcanic Ash. Accessed April 8, 2009.
The Volcanism Blog. (2009, April 7). Redoubt. Accessed April 8, 2009.
In contrast to the explosive eruptions of the previous week, ash emissions from Mount Redoubt became more frequent but confined to lower altitudes on March 30, 2009. The commercial satellite GeoEye-1 captured a high-resolution view of the volcano the same day.