2011–12 El Hierro eruption  The 2011-2012 El Hierro eruption occurred just off the island of El Hierro, the smallest and farthest south and west of the Canary Islands (an Autonomous Community of Spain), in the Atlantic Ocean off the coast of Africa. The island is also the youngest in the volcanic chain. The October 2011 - March 2012 eruption was underwater, with a fissure of vents located approximately 2 km to the south of the fishing village of La Restinga on the southern coast of the island. As of June 2012, increased seismicity to the north-west of the vent suggests another phase in the area's volcanic activity - comprising just deep-seated magma movements with associated earthquakes and deformation of the island at this June 2012 stage - is under way. A second phase of eruptive activity has not yet occurred, and it does not necessarily follow that it will occur. Beginning on 17 July 2011, increased seismic activity was detected by the Instituto Vulcanológico de Canarias (Volcanological Institute of the Canary Islands) and National Geographic Institute’s seismic monitoring station located in Valverde. The seismic monitoring network was increased in density on 21 July to allow better detection and location of the seismic events. There was an earthquake swarm with in excess of 400 minor tremors between 20 July and 24 July; by  27 July a further 320 earthquakes had been recorded. On 25 August there were reports that some horizontal deformation had been detected, but that there was no unusual vertical deformation. At that time, the total number of tremors had exceeded 4000. By the end of September, the tremors had increased in frequency and intensity, with experts fearing landslides affecting the town of La Frontera, and also a small possibility of a volcanic eruption through a new vent. In late September emergency services evacuated several families in the areas at most risk, and made plans to evacuate the island if necessary. Between 4.15 and 4.20am on 10 October 2011 the earthquake swarm changed behaviour and produced a harmonic tremor. Harmonic tremors are produced by magma movements and can indicate that an eruption has begun. That same day, patches of pale-coloured and sulphurous smelling water with dead fish were seen off the coast of La Restinga. A small submarine eruption had begun, 2 km south of La Restinga. Eruption 'jacuzzis', occasionally reaching 10-15m high above the surface of the water, were seen during the most energetic eruptive episodes.