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Exercise 3: Lava detection: crisis images and maps - continued 
The FCCs containing mid-IR (e.g. 4-5-3) enable you to distinguish between lava ages: hot lava becomes clearly visible and pops up as bright green (remember that the mid-infrared band has been assigned to green).
The plume, however, is not seen as distinctly. Previously, both the true colour image (3-2-1) and the 4-3-2 composite showed a giant plume, and lava appeared homogeneous. The thermal image (band 6)clearly shows the hot surface temperature of the whole surrounding area of the lava, as well as a hot area north of the volcano. The plume is clearly visible as a much cooler object than the surrounding areas. Etna’s vegetated areas also have significantly lower values (darker) than the lava-covered areas. Let’s have a look at the second images, recorded on 29 July. File > Open etna_2001-07-29_all. Close all the images from before, but leave the lava map open. Create some FCCs again and study the image.
6. What differences can be seen between the images?
7. Can you identify hot lava in the 4-5-3 or 7-4-2 composites? Why or why not? Look at the date of the image acquisition 8. Can you see a volcanic plume? 9. Has there been a significant weather event?
10. What is cool and what is hot in the image? Compare it with the 4-5-3 FCC.
11. Do you see the lava stream in the thermal band?
13. Why don’t you see the other lava streams?
14. Check if you can distinguish the lava stream from older lava in any of the other bands or in the 4-5-3 FCC. Compare and explain why you can or cannot.
Last update: 17 April 2013
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