Cumbre Vieja volcano eruption
19 September 2021 12:00 UTC-4 October 15:00 UTC
Photo credit: ISS
The Cumbre Vieja volcano on the Canary Island of La Palma erupted on 19 September 2021, causing thousands to be evacuated.
10 June 2022
20 September 2021
By Ivan Smiljanic and Alen Berta (CGI), Sancha Lancaster (Pactum), HansPeter Roesli (Switzerland), Jochen Kerkmann (Germany) and Miguel-Angel Martinez Rubio (AEMET)
The Meteosat-11 Ash RGB imagery from 19 and 20 September (Figure 1) shows higher concentration of SO2 emitting from the volcano in the hours after the eruption.
The GOES-16 24-hour Microphysics animation (Figure 2) shows the volcano mouth as a blue hotspot (higher temperatures), as well as the SO2 plume around it in cyan/green shades.
Comparing the GOES-16 VISO.6 Band (Figure 3, left) and 24h Microphysics RGB (Figure 3, right) imagery, highlights that GOES-16 'sees' ash more clearly in the visible channel (due to strong forward scattering in morning hours). Because of the low altitude of ejected ash (an indication of a not very violent eruption) the 24-hour Microphysics RGB product does not detect it. This is because the component of this RGB, responsible for ash detection, relies on the temperature difference between background (sea/land) and the observed ash cloud — which in case of low ash cloud is minimal. Also there are few stratocumulus clouds aloft, obscuring the view at times — ash cloud is visible as more static cloud in the animated GOES-16 visible imagery (Figure 4)
It is worth mentioning that the SO2 signal is also absent in Airmass RGBs (not shown here), because the SO2 cloud is not high enough. Due to water vapour absorption, only mid to high SO2 clouds can be detected in the Airmass RGB. An SO2 signal in an Airmass RGB can be seen in many other eruptions, for example, in this Etna eruption case from 2015, with its plumes higher than 3km, but for the Cumbre Vieja volcano eruption where the plume is at ca. 500–1500m.
With time the lava flow around the crater became larger, detectable even with the near-infrared channel of the GOES ABI instrument — namely the NIR1.6 band which provides red contribution to the Natural Color RGB in Figure 5.
The hotspot could also be detected in the Optimized Fire Radiative power for Copernicus Sentinel-3 (OFRP-CS3) product in Near Real Time (Figure 6). This is based on Processing Baseline 1.2 released in May 2021. The key parameter here is the Standard MWIR detection with a high enough confidence score (40% clear-sky), so no false alarms are caused by ash plumes or clouds.
1 October — Gravity waves
This volcano exhibited quite unique gravity-wave oscillations, seen by several satellites. See the example from 1 October in Figure 7.
4 October — Strong (low level) ash ejection
The strongest ash ejection from the beginning of this volcanic activity, mostly likely happened on 4 October. As well as ground level time lapse videos, several satellites captured this event, including the Terra polar orbiting satellite in Figure 8.
Interestingly, when comparing the Ash and Airmass RGB animations (Figures 10 and 11), the plume of SO2 is visible in the Ash RGB (green), but not in Airmass RGB (typically red). This is due to an inversion at around 500 hPa which constrained the plume height, so the component of Airmass RGB, normally sensitive to SO2 presence — the WV7.3 channel — did not see it due to its weighting function peaking higher up in troposphere (i.e. due to a water vapour absorption above the SO2, as well as the ash cloud). The Ash RGB could see it since it utilises the IR8.7 channel to detect SO2 (this channels has comparably much less H2O absorption, explained further in this EUMeTrain module). Ash is normally red in Ash RGB, pale green in Airmass RGB.
A similar episode of low level ejection occurred on 9 October. This time ash and SO2 plumes were constrained to even lower levels, at around 3km according to a nearby radiosounding (Guimar, Tenerife).
2 October — La Palma land extension
Lava flow towards the ocean changed the local landscape. A new peninsula was formed out of cooled magma, which, by the evening of 2 October (five days after the lava reached the sea), measured approximately 25 hectares (Figure 12).
Another Sentinel-1 RGB image (not shown here), created by combining the VH polarisation, confirmed that by 14 October the peninsula had grown another 2.5 hectares.
Thousands flee as lava spewing from volcano on Spain's La Palma island destroys houses (Reuters)
La Palma, Canary Islands: seismic crisis Sep 2021 - updates (Volcano Discovery)
Video of the eruption (Iván López/Twitter)