Mt. Redoubt Volcano started a new phase of activity with a series of eruptions on March 22, 2009. These eruptions were preceded by an increase in seismic activity around the volcano. The Alaska Volcano Observatory has released a series of satellite images that show large ash clouds drifting to the north of the volcano and continuing to the northeast over Anchorage, Alaska.
Pre-eruptive Activity of Mt. Redoubt
Mt. Redoubt is often seismically active, but a marked increase in seismic activity on January 23, 2009, raised the Aviation Color Code to ORANGE and raised the Volcano Alert Level to WATCH. At the time, volcanologists at AVO forecasted that the volcano would erupt within days to weeks of this increase in seismic activity.
Satellite Images of the 2009 Mt. Redoubt Eruption
Multiple satellite sensors detected the eruption cloud emitted by Mt. Redoubt. The composition of this cloud was a combination of ash, sulfur dioxide and ice particles. The satellite sensors that have detected atmospheric emissions from the Mt. Redoubt 2009 eruption are:
- The Ozone Monitoring Instrument (OMI) on NASA's Aura satellite
- The Advanced Very High Resolution Radiometer (AVHRR) on NOAA's polar-orbiting satellites
- The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua satellites
- The Multi-Functional Transport Satellite (MTSAT)
Images from these sensors can be used to study the transport of volcanic cloud species such as ash and sulfur dioxide.
Ash Clouds are an Aviation Hazard
The emplacement of ash clouds into the atmosphere from Mt. Redoubt eruption can be very hazardous to aircraft. For this reason, volcanologists routinely use satellite data of ash clouds in the atmosphere to warn pilots and air-traffic controllers about the location of these hazardous clouds. A very large eruption, such as the March 22, 2009 eruption, can emit thousands of kilotons of ash into the atmosphere at very high altitudes. Local and global wind patterns can then transport the ash in the cloud thousands of kilometers, making it a hazard to aircraft that may be nowhere near the erupting volcano.
Both the AVHRR and MODIS satellite sensors have been detecting ash emission from Mt. Redoubt. The ash can be seen in both the visible spectrum and the infrared spectrum. Being able to detect the ash cloud in the infrared spectrum makes it conveniently useful for detecting volcanic ash clouds at night.
Sulfur Dioxide Gas Clouds from Mt. Redoubt
Sulfur dioxide is often emitted in high amounts during a large volcanic eruption, such as the current Mt. Redoubt eruption. One of the tools volcanologists use to detect and measure the amount of sulfur dioxide emitted during an eruption is the OMI sensor. OMI was originally developed to measure ozone concentrations in the Earth's atmosphere, but due to the spectral signature of sulfur dioxide, OMI is also used to detect and measure sulfur dioxide within volcanic clouds. These kinds of measurements assist scientists in determining how greenhouse gases emitted from volcanoes, such as sulfur dioxide, impact the atmosphere.
Volcanologists will continue to get important satellite data about volcanic cloud emissions from Mt. Redoubt as the eruption progresses. This data not only aids in volcanic hazard awareness and mitigation, but it is also used towards developing better sensors for use in natural hazard research.
Source:
Alaska Volcano Observatory Mt. Redoubt Volcano Activity Page
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Alexandra Matiella Novak - With a PhD in Geology and expertise in science education, Alexandra is passionate about increasing the public's Earth science literacy.
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