occur before and during the 1971 eruption but was not on the scale associated with the 1949 eruption. Residual thermal emissions continue. 2021 eruption An earthquake swarm started under Cumbre Vieja on 11 September 2021. It slowly migrated to the surface, with earthquakes up to around 5 on the Richter scale, and over 25,000 recorded in the space of 10 days. On 19 September at 15:15 local time (14:15 UTC), the volcano started erupting, in Cabeza de Vaca in the Montaña Rajada mountains, in the Las Manchas section of El Paso municipality, A yellow warning was issued, covering 35,000 people in the municipalities of Los Llanos de Aridane, Fuencaliente, El Paso and Villa de Mazo, later raising to its highest level—red—due to the eruption. A total of around 7,000 people were evacuated from the area. The eruption stopped on 13 December 2021, and was declared to be over on 25 December 2021. Potential megatsunami Day et al. (1999) indicated that the Cumbre Vieja may be in the initial stages of failure. The authors of the paper also said that the geological development of La Palma had undergone changes due to the southerly migration of the hotspot and the collapse of the earlier volcanoes. Subsequent to this, a triple-arm rift system had evolved with the eventual closing down of volcanic activity associated with two of the arms—the north-west and north-east rifts. The reasons can only be hypothesised. This caused the southern arm—the Cumbre Vieja—to be the sole location of volcanic activity. As a result, they postulated that the western flank may be in the initial stages of failure. In October 2000, the British Broadcasting Corporation (BBC) transmitted a Horizon programme called "Mega-tsunami: Wave of Destruction", which suggested that a future failure of the western flank of Cumbre Vieja could cause a megatsunami. On 18 April 2013, the BBC transmitted a follow-up programme entitled Could we survive a Mega-Tsunami? The programme was presented in a "breaking news" reporting style. It painted a scenario in which the western flank of the Cumbre Vieja had collapsed and the initial wave had an amplitude of about 1,000 metres. The programme used computer generated graphics to present a story line that is based on a hypothesis. The programme interviewed several scientific personnel to give credence to the story. One scientist claimed, "This is a true story—only it hasn't happened yet!" Day et al. (1999), Ward and