On 12 August 2011, Etna had its tenth paroxysm of the year, captured in the Meteosat-9 Ash RGB product.
22 February 2021
12 August 2011
by HansPeter Roesli (EUMETSAT)
Etna spewed first an SO2 cloud (green colour) followed by an ash cloud (red colour).
On 12 August 2011, Etna had its tenth paroxysm of the year (the volcanology term paroxysm for a short violent burst). The plumes moved south-eastwards and only rising a few hundred metres above the craters. In rapid succession Etna spewed some SO2; a thick white plume; a plume of black ash and SO2 and, finally, ash only. These details may be gleaned from a sequence of Meteosat-9 SEVIRI images that shows: a) the HRV channel (top images), b) the Ash RGB product (central images) and c) the Dust RGB product blended with HRV and IR3.9 (the hottest pixels).
|Time (UTC)||HRV Channel||Ash RGB Product|
|08:30||light-green smudge (SO2 cloud)|
|09:00||white smudge (water cloud)||light-green plume (more SO2)|
|10:00||short dark plume (ash)||pale-yellow smudge (SO2 and ash)|
|10:45||longer dark plume (more ash)||reddish-yellowish-green plume (ash, SO2 and ash, SO2)|
The full evolution of the paroxysm is shown in a sequence of images (04:30–13:30 UTC) of the channel combination mentioned above. The temporary westward extension of the hot spot at top of Etna is an artefact of the IR3.9 detectors that go in saturation when the sensed temperature goes above ~336 K. By the day after the brief eruption the SO2 cloud has travelled as far as the eastern coast of Libya (see Ash RGB animation, 12 Aug 06:00 UTC–13 Aug 09:00 UTC).
MODIS on Terra overflew the paroxysm just after 09:40 UTC. A comparison with the SEVIRI images shows more details of the complexity of the plume in this instance. The bottom row shows SEVIRI images with the Ash RGB product, the VIS0.6 channel and a combination of them. The top row is from MODIS and shows the same using proxy channels.
More details including various photos on this paroxysm are given in a report by the Istituto Nazionale di Geosfisica e Vulcanologia (INGV) in Catania, only in Italian though.
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