Satellite Detects Chaiten Eruption
Chaiten Volcano, Chile Erupting Ash into the Atmosphere
The ash being emitted by the May 2008 eruption of Chaiten Volcano is detected using earth observing satellites
Chaiten Erupts
On May 2, 2008, Chaiten Volcano, located in southern Chile, emitted an ash column to a height of about 10-16 km (6-9 miles). This ash plume is large enough to be detected by earth observing satellites and the data the satellites are sending to us is telling us a lot about the eruption.
A May 3 image taken from NASA’s Terra satellite shows an ash cloud stretching approximately 650 km (400 miles) from Chaiten Volcano southeast across the entire country of Argentina. Ash retrievals can be done on the image to find the ash characteristics of the cloud, such as the total fine ash mass of the cloud and areas where ash is more concentrated.
Satellite Detection of Volcanic Ash
An ash retrieval was done on this NASA image – the difference in temperature between wavelengths at 11 µm and 12 µm is measured and related to the amount of ash in the atmosphere. Where ash is present, subtracting the temperature at 12 µm from the temperature at 11 µm will produce a negative value. Most earth observing satellite sensors are capable of recording temperatures at these wavelengths, so detecting ash clouds in the atmosphere is a common method of studying volcanic eruptions all over the world.
Volcanic clouds that are erupted into the upper atmosphere (>10 km), like the one erupted from Chaiten Volcano, are more easily observed from satellites than from the ground. These kinds of eruptions are also extremely hazardous to aircraft because they reside at heights that are frequently the flying altitudes for most aircraft. For this volcanic eruption, the Buenos Aires Volcano Ash Advisory Center (VAAC), located in Buenos Aires, Argentina, will be in constant communication with pilots and air traffic controllers in the area.
VAACs all over the world use satellite sensors to detect volcanic ash clouds in the atmosphere and relay information such as height and location of the cloud to the aviation community. In most cases, satellite data is free and easily accessible, making communication of ash cloud information efficient.
The Chaiten Volcano Ash Cloud
For this image, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Terra satellite, an ash mass of about 200,000 metric tons was calculated using the temperature difference technique. The area of greatest ash concentration of the cloud is closer to the volcano, suggesting that the volcano was still emitting ash when the satellite image was taken.
Source: Smithsonian Institute's Global Volcanism Program
