Etna outbreak
In the middle of March mount Etna has been systematically erupting for several days. The first eruption has been recorded on Wednesday March 15th (11:30 am local time) and the activity has spread until a second outbreak on Saturday, with a series of pyroclastic flows, up to the next Monday (March 20th). A few persons got injured and the Catania airport has been closed for several hours.
This activity has been observed and captured by ESA Sentinels 2A and 3A (Copernicus Programme) from March 16th to March 19th, where the lava flow erupted at 2700 m of altitude and ran up to 1800 meters high.
Here below a gif composed by two consecutive images acquired by Sentinel-2A. The lava flow path appears very clear, thanks to the MSI multispectral SWIR-NIR bands composite, just like its descent along the slope of the volcano. The two images acquired three days apart allow to distinguish the bright hot lava from the cold snow surface. The particular RGB composition with the exploitation of two SWIR channels permits also to discern between clouds (in white) and snow (in light blue). At a first glance also the snow melting can be seen at lower altitudes.
Mount Etna is one of the most active Volcano in the World with its eruption all over the five different craters on the summit. Those eruptions could be explosive in some cases, but rarely dangerous for the inhabited area around the volcano. In any case Etna eruptions have a variable pattern that could lead also to voluminous lava flow travelling for tenth of kilometres, just like it is shown in the two images above captured by S2-A.
Sentinel 3 OLCI gives us another taste of this phenomenon with its 300m spatial resolution. Here below an RGB with natural colour captured in the morning of March 19th shows the black smoke trace after one of those eruptions, spreading for hundreds of kilometers in the sky
The lava has been also detected and isolated by the thermal bands of S3-A SLSTR. Here below there are two different classification of the same thermal response (almost 4000 nm band), captured at the same time of the OLCI product shown above.
In both cases a land mask has been applied in order to show only the thermal response of the land zones, then projected on google earth. The temperature legend is expressed in Kelvin. The first classification has a colour bar scale equally distributed. There are several pixels on Mount Etna corresponding to the lava flow in green and red, with a detected temperature up to 450 K, i.e. almost 200°C, compared to the very lower temperatures observed all over the Sicily.
The lava temperature is normally higher than 600°C, on the other hand SLSTR thermal bands offer a resolution of 1km, so the detected temperature is basically an average of 1 Km^2 pixel area.
The last image below is the same thermal response but with a not equally distributed color scale classification. In this case are highlighted both the lava and the snow on the Mount Etna, obviously colder than the other continental zone.
All the Sentinels products have been downloaded from: https://scihub.copernicus.eu/
The eruption of Mount Etna volcano is also visible in the Proba-V 100m image of the 19/03/2017. The image below is a false-color image in the short-wavelength infrared. In this image, ice appears as blue and hot pixels appear as red.
Proba-V products have been dowloaded from:
http://www.vito-eodata.be/PDF/portal/Application.html#Home
Insights:
https://www.volcanodiscovery.com/etna/news.html; http://geology.com/volcanoes/etna/; http://palermo.repubblica.it/cronaca/2017/03/18/news/etna_l_eruzione_continua_aeroporto_di_catania_chiuso_nella_notte-160819520/#gallery-slider=160836779
Contains modified Copernicus Sentinel data 2017.
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