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| ||Exercise 2: Hot spot and plume detection|
Hot spot detection
Volcanic activity can be identified by detecting thermal hot spots. Hot thermal anomalies of volcanoes detected by infrared sensors can be due to the lava flow of any thermal anomaly (e.g. fumaroles). A warning is given when indices calculated by infrared bands exceed a certain threshold (see Hot spot monitoring with MODIS). The term ‘hot spot’ must not be confused with ‘hotspot volcanism’.
Open the Bands 21 and 22 and apply stretching:
File > Open > etna_mod_2001-205_bd21 > Enhance > Interactive Stretching
File > Open > etna_mod_2001-205_bd22 > Enhance > Interactive Stretching
MODIS: Bands 21 and 22
In both bands data in the range of ~ 4 µm (3.929 - 3.989 µm) was recorded and is suitable for hot spot detection. Band 22 is used, which measures up to -330 K, but when band 22 is saturated, band 21 can be used, which has a saturation temperature of -500 K. In both images the hot spot is clearly detectable as an area of bright pixels in the summit area of Etna.
Volcanic Plume Detection
A volcanic plume is a mixture of particles and gas emitted by an eruption. The plume is generated by fragmentation of magma. Plumes may reach heights of 80 km in large eruptions. Volcanic ash can be transported to the atmosphere and reach the height of air traffic within ten minutes. The detection, monitoring, and forecasting of plumes is essential to provide safety for air traffic. To find out more about this, have a look at the Toulouse Volcanic Ash Advisory Center.
Open these two images and stretch them:
File > Open > etna_mod_2001-205_bd31 > Enhance > Interactive Stretching
File > Open > etna_mod_2001-205_bd32 > Enhance > Interactive Stretching
You can see that in both bands the volcanic plume, as well as the clouds (top right of the image) appear dark.
Monitoring of volcanic hot spots and plumesWorksheet introductionExercise 1: Exploring the volcanoExercise 3: Monitoring a plume - animation
Eduspace - DownloadEtna_MODIS.zip
Eduspace - SoftwareLEOWorks 3LEOWorks 3 Tutorial
Related linksHot spot monitoring with MODISVolcanic Ash Advisory Centres