page_title: Cumbre Vieja
section_title: 1949 eruption
hierarchical_section_title: Cumbre Vieja / Volcanic history / 1949 eruption
caption_attribution_description: English: Crater del Hoyo Negro, La Palma, Spain
context_page_description: Cumbre Vieja is an active although dormant volcanic ridge on the volcanic ocean island of La Palma in the Canary Islands, Spain, that erupted twice in the 20th century – in 1949, and again in 1971.
  The ridge of the Cumbre Vieja trends in an approximate north-south direction and covers the southern two-thirds of the island. Several volcanic craters are located on the summit ridge and flanks.
context_section_description: The onset of the eruption was witnessed by a shepherd who was tending his flock of sheep on the flank of the Nambroque – (Bonelli-Rubio 1950, is explicit that the shepherd was only tending sheep). He was startled to hear noises emanating from the Duraznero vent and became extremely alarmed when material started being expelled from the vent. In a state of panic he fled the area and sought refuge as far from the vent as he could. The only contemporaneous account of the eruption was published in 1950 by one of the scientists – Juan Bonelli-Rubio who witnessed the eruption first hand and recorded details of the various phenomena that occurred during the eruption. All other published accounts are based upon Bonelli-Rubio's observations. The next report regarding the eruption was a joint publication by Ortiz and Bonelli-Rubio published in 1951. This drew heavily on Bonelli-Rubio's observations and also analysis of various phenomena associated with the eruption. Both accounts are published in Spanish.
  The eruption started on 24 June 1949 – the feast day of St John, which is why in Spanish texts the eruption is referred to as "la erupcion del Nambroque o San Juan," which in English is "The Eruption of the Nambroque or St John's volcano." During the 1949 eruption, eruptive activity was located at three vents—Duraznero, Llano del Banco, and Hoyo Negro—mild strombolian activity occurred at the Duraznero vent. Lava was erupted from the Llano del Banco vents, whilst only mild phreatomagmatic emissions occurred at the Hoyo Negro vent. Then on 30 July – the last day of eruptive activity, lava was erupted at the Duraznero fissure and vent. During the eruption on 1 and 2 July, two strong earthquakes with an estimated intensity of VIII on the Modified Mercalli Scale also occurred, the epicentre was calculated to be near Jedey. Following the earthquakes a fracture was noted and it had a length of approximately one and half kilometres. It was traceable to the Hoyo Negro and Duraznero vents, making a total length of about two and half kilometres or about 1/10 of the exposed length of the Cumbre Vieja, and parts of the western half of the Cumbre Vieja ridge had apparently moved about 1 metre sideways and 2 metres downwards towards the Atlantic Ocean. It was only in the vicinity of the Duraznero and Hoyo Negro vents that the vertical displacement attained about 4 metres. As of 2009, the fracture is still visible and still has the same dimensions recorded in 1949.
  The timeline for the eruption, according to Bonelli-Rubio, is as follows: The first reported seismic activity was noted on the southern rim of the Caldera de Taburiente on 23 July 1936 at about 23:30 (11.30 pm) local time, with further activity noted over the next two days. During the following years periodic seismic activity occurred, but due to the absence of monitoring equipment, the only reports are those recorded in the media. Then at about 09:00 (local time) on 24 June 1949, the Duraznero vent opened with mildly explosive activity, venting of gases, and rocks; with eruptive activity continuing in this manner until 6 July. During this phase a strong earthquake occurred on 1 July and again on 2 July with an estimated intensity of VIII on the Modified Mercalli Scale. Visits to the summit region revealed a crack about 1.5 km (~1 mile) long which extended in a northerly direction from the Hoyo Negro (Black Hole) and about 1 km (~0.5-mile) south to the Duraznero vent making a total length of about 2.5 km (~1.6-mile), (this crack is the subject of research and heated debate as to whether it indicates initial failure of the western flank – or not). Later analysis placed the epicentre north of the township of Jedey. Eruptive activity at the Duraznero vent ceased on 6 July with only degassing continuing. No eruptive activity occurred on 7 July. On 8 July eruptive activity commenced at the Llano del Banco vents – about 4 km (~2.8miles) north of the Duraznero vent, as lava was erupted and flowed down the western flank. The vents opened progressively up the barranco (ravine), forming a serie
caption: Crater del Hoyo Negro, 2008
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