The 2011 El Hierro submarine eruption seen in MSG and Metop images.
06 December 2022
04 November 2011
By Jochen Kerkmann and HansPeter Roesli (EUMETSAT)
During 2011, an underwater volcano was active for a many months and located close the southern tip of El Hierro in the Canary Islands. Accoring to Wikipedia it began on 17 July 2011, and increased seismic activity was detected by the Instituto Vulcanologico de Canarias and the National Geographic Institute's seismic monitoring station located in Valverde. In October 2011, the earthquake behaviour changed to a harmonic tremor.
Harmonic tremors are produced by magma movements and can indicate that an eruption has begun. In early November the 600 residents of La Restinga were evacuated for a second time. A confirmed surtseyan type of eruption phase started at the fissure on 7 November 2011. On 28 November 2011 the eruption was still ongoing with vigorous phreatic bubbles emerging.
On 23 October 2011, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured a true color view of El Hierro and the North Atlantic Ocean surrounding it (Figure 1). According to NASA Earth Observatory, a milky green plume in the water stretched 25–30km at its widest and perhaps a 100km long, appearing as a large blob near the coast and then becoming thin tendrils as it spread to the southwest.
The plume was likely a mix of volcanic gases and a blend of crushed pumice and seafloor rock. The plume was also visible in strongly enhanced Meteosat-9 HRV images (Figure 2). Since this broad-band channel (see filter function) has a significant contribution from blue and green light (around 0.4 and 0.5 micrometer), it is the most suitable MSG channel for viewing this type of ocean feature.
The image below from Metop-A AVHRR demonstrates that the ongoing submarine eruption is not only spewing debris into sea, but also warming the water. On 5 November, the Metop-A AVHRR hot spot produced by the submarine eruption is warmer than the surrounding waters by 1–2K. Locally, and on a smaller scale, much higher sea surface temperatures can be expected. According to geologist and blogger Erik Klimetti, the eruption was warming the water by as much as 10°K.
EO-1 Advanced Land Imager (ALI) image on 2 November 2011 (Source: NASA)