Detecting the Holuhraun Volcanic Eruption with NPP VIIRS
A volcanic eruption North of the Vatnajökull glacier in Iceland has been ejecting lava through the Earth's crust for a few weeks now, and the event is now being hailed as "comparable to some of the most famous volcanic eruptions in human history."
I wondered if there was still evidence of these eruptions taking place on the surface, so rather than flying to Iceland, I went to NOAA's CLASS website to see if I could find anything. After some time searching through imagery taken by the NPP VIIRS sensor, I found the right one.
I loaded the imagery in to ENVI to do radiometric calibration, GLT-reprojection, and bowtie correction to get rid of the striping that occurs in NPP VIIRS. Once finished, it looks like this:
Image from NPP VIIRS, taken at 14:17 GMT on September 23
The bands used in this image are at 640, 865, and 1610 nanometers. This means that the blue band is tied to visible light, the green band to near Infrared, and the red band to short wave infrared. This is why highly reflective ice, snow, and clouds are blue, and areas with plant life on land are green.
But what about the red band? If we zoom in on Iceland, this is what we see:
It is no surprise that there is a strong thermal signature in red coming from the Holuhraun area, as there is lava on the surface of the planet. This area is hot, and will continue to emit thermal radiation for some time. Lava has actually been flowing in Holuhraun since the last volcanic eruption there - this newest spurt of volcanic activity has merely added to the already existing lava on the surface.
NPP VIIRS has an extremely wide swath and large pixel size, making it hard to use for spatially smaller events. However, weather patterns and volcanic eruptions are on a scale large enough to be not only detected with NPP, but monitored as well. With ENVI becoming time aware with the imminent release of ENVI 5.2, there are going to be some amazing analytics to employ that can show how these large scale events evolve.