FAQ







Hierro

Google Earth Placemark
  • Country
  • Subregion Name
  • Volcano Type
  • Last Known Eruption
  • 1500 m
    4920 ft
  • 27.730°
  • -18.030°
  • Elevation
  •  
  • Latitude
  • Longitude

27 March-2 April 2013

On 18 March seismic activity at El Hierro sharply increased. Earthquakes were initially located around the NW tip of the island, at about 20 km depth, then later migrated W about 12-15 km offshore W of El Hierro Island, at similar depth. About 100 earthquakes of Mb 3.5 (body wave measurement) or greater had been located, many of them felt by residents. The biggest events occurred on 29 March (Mb 4.7) and 31 March (Mw 4.6, moment magnitude) both at 20 km depth. IGN's GPS data showed inflation of the island, with maximum deformation at the westernmost station of about 10 cm in the horizontal component and about 11 cm in the vertical. Deformation rates reached a maximum during 23-24 March. An increase in carbon dioxide flux was observed in the W area.

Rockfalls were reported on the steep slopes, especially during 26-29 March. On the evening of 27 March the Plan de Protección Civil por Riesgo Volcánico (PEVOLCA) raised the Volcanic Alert Code for the population to Yellow, and closed the access to the W part of the island.

Sources: Instituto Geográfico Nacional (IGN)



 Available Weekly Reports




2013: March |
2012: January | February | June | July |
2011: September | October | November | December |

27 March 2013              Back to Top

On 18 March seismic activity at El Hierro sharply increased. Earthquakes were initially located around the NW tip of the island, at about 20 km depth, then later migrated W about 12-15 km offshore W of El Hierro Island, at similar depth. About 100 earthquakes of Mb 3.5 (body wave measurement) or greater had been located, many of them felt by residents. The biggest events occurred on 29 March (Mb 4.7) and 31 March (Mw 4.6, moment magnitude) both at 20 km depth. IGN's GPS data showed inflation of the island, with maximum deformation at the westernmost station of about 10 cm in the horizontal component and about 11 cm in the vertical. Deformation rates reached a maximum during 23-24 March. An increase in carbon dioxide flux was observed in the W area.

Rockfalls were reported on the steep slopes, especially during 26-29 March. On the evening of 27 March the Plan de Protección Civil por Riesgo Volcánico (PEVOLCA) raised the Volcanic Alert Code for the population to Yellow, and closed the access to the W part of the island.

Sources: Instituto Geográfico Nacional (IGN)

11 July 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 11-17 July both seismic activity and deformation at El Hierro decreased. There were 87 seismic events located, most of them offshore SW of El Hierro Island at about 20 km depth. Only six earthquakes were M 2.7 or higher, and the maximum magnitude recorded was 3.4, corresponding to two events: 14 July at 1952 and 17 July at 0746. The deformation rate decreased, with maximum values of less than 1 cm in the horizontal components.

Sources: Instituto Geográfico Nacional (IGN)

4 July 2012              Back to Top

On 11 July Instituto Geográfico Nacional (IGN) reported that seismic activity and deformation at Hierro had decreased since the previous week. During 4-10 July there were 650 seismic events located, most of them offshore SW of El Hierro Island at 20 km depth. The maximum magnitude recorded was 3.8, which occurred on 10 July at 0504, and 77 earthquakes were M 2.7 or higher. The total number of located events had reached more than 2,200 since the anomalous activity began on 24 June. The deformation during this period had maximum values of about 1.5 cm in the horizontal component and 1.5 cm of vertical displacement.

Sources: Instituto Geográfico Nacional (IGN)

27 June 2012              Back to Top

On the night of 24 June, a M 3.1 earthquake occurred offshore N of El Hierro island at a depth of 20 km. After that event, both the seismic activity and the deformation greatly increased. The seismicity, initially located N of the island in the El Golfo area, migrated S, then later to the W, along the E-W rift zone. On 27 June, the Plan de Protección Civil por Riesgo Volcánico (PEVOLCA) raised the Alert Level to Yellow (on a three-color, traffic-light scale) for areas near El Julan (along the SW coast) and La Dehesa; The Alert Level remained at Green for the rest of the island.

On 28 June, seismicity migrated to the SW in Las Calmas Sea and remained SW of the island, mainly offshore, until 3 July. The depth of the events was concentrated around 20 km. Since 24 June, more than 1,500 events have been located, and more than 250 of those events were M 2.7 and higher and often felt by residents. The biggest event was a M 4.4 that occurred on 2 July at 2242, located offshore SW the island, at 19 km depth. High deformation rates were measured by every GPS station on the island, reaching 8 cm in the horizontal component and about 10 cm of vertical displacement.

Sources: Instituto Geográfico Nacional (IGN)

29 February 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 29 February-6 March the seismic amplitude detected by every IGN station in El Hierro remained at very low values. Neither water discoloration nor activity was observed on the sea surface over the emission area. On 5 March, the Scientific Committee stated that the submarine eruption was over, but the volcanic process that started on mid July 2011 had not finished. The Canary Islands Government lowered the Volcanic Alert Code from Red to Yellow, maintaining a maritime exclusion zone around the emission area.

Thirty four seismic events were located, most of them in the central part of the island, extending offshore to the S. Depths of the hypocenters varied between 7 and 24 km, and magnitudes were 0.1-2.1 (twenty eight events were magnitudes equal to or greater than 1). One of these events was felt by residents and had a maximum intensity value of II (EMS-98). GPS data did not show persistent trends in any horizontal or vertical components.

Sources: Instituto Geográfico Nacional (IGN)

22 February 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 22-28 February the seismic amplitude recorded at every IGN station on El Hierro Island remained at very low values. Weak and intermittent discoloration was observed on the sea surface over the emission area. Only once were emitted lava fragments observed during the reported period.

One-hundred and seven seismic events were located, most of them in the central part of the island, with a few extending offshore to the S. Depths of the hypocenters varied between 8 and 20 km and magnitudes between 0.1 and 2.6 (46 events with magnitude 1 or greater). Three events were felt by residents with a maximum intensity value of III (EMS-98). GPS deformation analyses showed a slight trend to N in the stations located at the N of the island.

Sources: Instituto Geográfico Nacional (IGN)

15 February 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 15-16 February the amplitude of the tremor showed very low values, and after 17 February the tremor signal could not be clearly recognized in the seismic records. Very weak and intermittent discoloration was observed in the emission area. By the end of the reported period, there was no clear instrumental evidence of continuous eruptive activity.

One hundred and thirty-five seismic events were located, most of them in the central part of the island, with offshore events extending to the S. Depths of the hypocenters varied between 6 and 20 km and magnitudes between 0.2 and 2.5 (91 events with a magnitude equal or greater than 1). One event was felt by residents with a maximum intensity value of II (EMS-98). GPS data pointed to a slight uplift in some stations located at the N of the island.

Sources: Instituto Geográfico Nacional (IGN)

8 February 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 8-14 February the submarine eruption continued S of El Hierro Island. The mean amplitude of the tremor remained low overall, but was variable. Very few emissions of lava fragments were observed over the vent area.

Fifty seven seismic events were registered during this period, most of them located in the central part of the island, with offshore events extending to the S. Depths of the hypocenters varied mainly between 6 and 17 km and magnitudes between 0.6 and 2.2. GPS data pointed to a slight subsidence at some of the stations.

Sources: Instituto Geográfico Nacional (IGN)

1 February 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 1-7 February the submarine eruption continued S of El Hierro Island. The amplitude of the tremor signal started to increase on 1 February around 0700, maintaining significant values until 6 February, when it dropped again to almost no signal. On 7 February the amplitude values increased for a few hours. Scarce emissions of lava fragments were observed over the vent area.

Fifty seismic events were registered during this period, most of them located in the central part of the island, with offshore events extending mainly to the S. Three of them were felt by residents, with a maximum intensity value of III (EMS-98). Depths of the hypocenters varied between 6 and 23 km, and magnitudes between 0.6 and 3.2.

Sources: Instituto Geográfico Nacional (IGN)

25 January 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 25-31 January the submarine eruption continued S of El Hierro Island. Mean tremor amplitude maintained very low values during this report period. Frequent and persistent emissions of large steaming lava fragments were observed on the sea surface, some of them about 3 m wide.

Seventy-eight seismic events were registered during this period, most of them located in the central part of the island, with offshore events extending primary to the S. Depths of the hypocenters varied between 10 and 23 km, and magnitudes between 0.4 and 2.8. Analyses of GPS deformation showed stability both in vertical and horizontal components.

Sources: Instituto Geográfico Nacional (IGN)

18 January 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 18-24 January the submarine eruption continued S of El Hierro Island. Mean tremor amplitude has oscillated considerably since 19 January, including abrupt changes from rather high values to periods of almost no tremor which lasted a few hours. Emissions of large steaming lava fragments were observed every day of this report period.

Thirty-two seismic events were registered during this period, most of them located in the central part of the island, extending offshore to the S, at depths between 8 and 19 km with a maximum magnitude of 2.2. Analyses of GPS deformation showed stability both in vertical and horizontal components.

Sources: Instituto Geográfico Nacional (IGN)

11 January 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 11-17 January, the submarine eruption continued S of El Hierro Island. The mean amplitude of the tremor moderately increased during the week. Eighteen seismic events were located during this period, two of them felt by residents of the island. Most of the events were grouped in the central part of the island, extending offshore to the S, at depths between 6 and 29 km, with a maximum magnitude of 2.5. Analyses of GPS deformation showed stability both in vertical and horizontal components.

Sources: Instituto Geográfico Nacional (IGN)

4 January 2012              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 4-10 January, the submarine eruption continued S of El Hierro Island. The mean amplitude of the tremor slightly increased during the week. During this period, large floating lava fragments were observed close to the vent area and generating steam. The production of these fragments was especially intense during 6-8 January.

Nineteen seismic events were located during this period, most of them were grouped in the central part of the island, extending offshore to the S, at depths between 10 and 18 km, with a maximum magnitude of 2.0. GPS data analyses showed little deformation, with a trend to subsidence in the stations at the S of the island.

Sources: Instituto Geográfico Nacional (IGN)

28 December 2011              Back to Top

Instituto Geográfic Nacional (IGN) reported that during 28 December-3 January, the submarine eruption continued S of El Hierro Island. The tremor signal almost disappeared for a few hours on 28 December, after three hours with pulses every 30 seconds. The tremor amplitude started increasing again at approximately 16:35. Most of the days, large lava fragments and fine material could be observed on the emission area.

Twenty-four seismic events were located during this period, most of them grouped in the central part of the island, extending offshore both to the N and S. The depth of most of these events ranged between 9 and 23 km, with a maximum magnitude of 2.5. GPS data analyses showed very little deformation, with a slight trend to the N in the stations located at the N of the island.

Sources: Instituto Geográfico Nacional (IGN)

21 December 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 21-27 December the submarine eruption continued S of El Hierro Island. The mean amplitude of the tremor signal remained stable during the week. Twelve seismic events were located during this period, most of them offshore, both to the N and S of the island, at depths between 12 and 26 km with a maximum magnitude of 2.8. GPS deformation data analyses showed stability in the horizontal components and trends to stability in the vertical component.

Sources: Instituto Geográfico Nacional (IGN)

14 December 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 14-20 December the submarine eruption continued S of El Hierro Island. During the beginning of the week, high-amplitude pulses were registered in the tremor signal every 5-10 minutes. On 15 December there were two long pulses around 7 minutes each, and after the second one the mean tremor amplitude values remained similar to those of previous weeks.

Six seismic events were located during this period, both offshore to the N and inland, at depths between 3 and 22 km. GPS deformation data analyses showed stability in the horizontal components and deflation in the vertical component.

Sources: Instituto Geográfico Nacional (IGN)

7 December 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 7-13 December the submarine eruption continued S of El Hierro Island, with steaming lava fragments sporadically observed floating on the sea. During this period, the mean tremor amplitude oscillated between decreasing and increasing trends during the first days of the week, and since 10 December high-amplitude pulses occurred every 5-10 minutes.

Only seven seismic events were located during this period, most of them offshore to the N of the island at depths of 17-23 km and with a maximum magnitude of 2.0. GPS data analyses showed stability in the horizontal components and trends to deflation in the vertical component.

Sources: Instituto Geográfico Nacional (IGN)

30 November 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 30 November-6 December the submarine eruption continued S of El Hierro Island, with lava balloons sporadically observed floating on the sea. During this period, the mean tremor amplitude was similar to the previous week. Twenty-eight seismic events were located, most of them offshore to the N of the island at depths of 15-24 km and with a maximum magnitude of 2.8. Only one of these events was felt by residents at a maximum intensity value of II using EMS-98 (European Macroseismic Scale). GPS data analyses showed stability in the horizontal components; the vertical component at stations located on the S and NE parts of the island showed subsidence.

Sources: Instituto Geográfico Nacional (IGN)

23 November 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 23-29 November the submarine eruption continued S of El Hierro Island. During this period, the mean amplitude of the tremor showed a slight increase. On 26 November large steaming fragments of lava appeared intermittently floating over the emission center. On 27 November, the emissions were more intense and a few hundred fragments could be observed floating simultaneously, with mean dimensions between 0.5 and 2 m. Some samples of the fragments were collected from a ship near the emission area.

During the period, 121 seismic events were located, most of them offshore to the N of the island at depths of 15-23 km and a maximum magnitude of 3.3. Seven of these events were felt by residents at a maximum intensity value of III using EMS-98 (European Macroseismic Scale). GPS data analyses trended towards stability in the horizontal components, while in the vertical component most of the stations showed subsidence while stations in the NE of the island also trended towards stability.

Sources: Instituto Geográfico Nacional (IGN)

16 November 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 16-22 November the submarine eruption continued S of El Hierro Island. During this period, the amplitude of the tremor showed two rapid changes, a decrease in amplitude at 2200 on 17 November and an increase at 1710 on 19 November. Seismic amplitudes decreased between late 20 November and mid-day on 21 November, and then remained stable at values similar to those noted during 19-25 October. Superficial activity over the emission center was rare, characterized by alternating days without seawater discoloration and days where there was minor gas and tephra content in the water and persistent discoloration.

During the period, 200 seismic events were located, most of them offshore to the N of the island at depths of 16-23 km and a maximum magnitude of 3.7. Seventeen of these events were felt by residents at a maximum intensity value of III using EMS-98 (European Macroseismic Scale). GPS data analyses showed little deformation in the horizontal components, while in the vertical component stations located in the N of the island showed uplift and the rest showed subsidence.

Sources: Instituto Geográfico Nacional (IGN)

9 November 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 9-15 November the submarine eruption continued S of El Hierro Island; mean amplitude of tremor was similar to that of the previous week. During the period, 245 seismic events were recorded, most of them located offshore to the N of the island, at depths of 16-23 km. Twenty one of these events were felt by residents at a maximum intensity value of IV-V using EMS-98 (European Macroseismic Scale). The maximum magnitude was 4.6, for an event located 2.5 km offshore to the N at 21 km depth on 11 November, and was the largest of the 11,604 total events detected since 16 July. GPS deformation analysis continued to show different behaviors between N and S stations; N stations showed deformations to the N up to the time of the M 4.6 event, when the deformation then changed to S. Stations located in the S showed deformation trends to the N.

On 9 November, access to two creeks (Tacorón and Punta Naos) in the S of the island was prohibited due to the possibility of significant concentration of volcanic gases. On 14 November, residents of La Restinga were allowed to return to their homes. That same day, many big steaming lava blocks (more than 1 m in diameter) were observed over the submarine emission center.

Sources: Instituto Geográfico Nacional (IGN)

2 November 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 2-8 November the submarine eruption continued S of El Hierro Island. Tremor amplitude reached higher values than during previous weeks, getting closer to the values detected during 11-12 October, just after the beginning of the eruption. During 3-4 November an increase of the activity could be observed over the submarine emission center, with large circles of light blue color on the sea surface, followed by foam rings and turbulent water with volcanic material. Close to sunset on 5 November, big bubbles rose to the sea surface and ejected sea water and volcanic material a few meters above the water. This activity continued during the following days.

During 2-8 November, 364 seismic events were recorded, most of them located offshore to the N of the island, at depths of 16-23 km. The maximum magnitude was 4.4, and 32 of these events were felt by residents at a maximum intensity value of V using EMS-98 (European Macroseismic Scale). The total number of located events since 17 July was 11,294. GPS deformation analysis showed trends towards no deformation during the first days of the reported period, and a slight trend towards deformation to the S at the stations located on the N side of the island in the last days.

During 4-5 November authorities evacuated about 80 residents from areas in Frontera due to landslide risks from seismic activity. Residents of La Restinga were evacuated on 5 November. According to a news article, ships and aircraft were banned from the area.

Sources: Instituto Geográfico Nacional (IGN) , Gobierno de Canaries , Associated Press

26 October 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 26 October-1 November tremor continued to be registered by every seismic station on El Hierro Island; 540 seismic events were registered and located, and the mean amplitude increased slightly during the last two days. Most of the events were located offshore to the N of the island, at depths of 16-23 km. The maximum magnitude was 3.9, and 36 of the total events were felt by residents at a maximum intensity value of IV using EMS-98 (European Macroseismic Scale). The total number of located events since 17 July was 10,930.

Preliminary analysis of GPS deformation data showed an inflation-deflation sequence at one station on the N side of the island, with the main deformation trending N-S and in vertical components. GPS stations located in the W and S showed different behavior, with mean deformations to the SW and NE, respectively.

Sources: Instituto Geográfico Nacional (IGN)

19 October 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that during 19-25 October tremor continued to be registered by every seismic station on El Hierro Island; 270 seismic events were registered and located. The mean amplitude was lower than during previous days but indicated that the submarine eruption continued. Since 21 October, most of the events were located in the N part of the island, aligned NNW-SSE from the center of the island to around 13 km offshore. Most of these earthquakes occurred around 20-25 km depth. Superficial analysis of GPS deformation data from the last few days of the reporting period showed different behaviors between the stations located at the N of the island and the station located at the S, close to the submarine eruptive vent.

Sources: Instituto Geográfico Nacional (IGN)

12 October 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that tremor, registered by every seismic station on El Hierro Island, continued during 12-18 October. Deformation decreased during this period, with significant inflation-deflation episodes registered by the stations located in the NW part of the island. On 12 October, at about 1430, the amplitude of the tremor signals abruptly decreased and smaller amplitudes persisted during the following days. During the afternoon of 12 October a large light-green colored area was observed in the sea to the S of La Restinga village (at the southernmost point of Hierro); the evolution of this anomaly was observed from land and by helicopter. The extension of the anomaly was controlled by the ocean currents, but a small area was detected as the emission center due to its intense discoloration and concentration. During a helicopter flight on 15 October, steamy lava fragments in this small area were observed. In the same area, during 15-17 October, frequent episodes of emission, forming big turbulent rings of gas and foaming, were observed on the sea surface. Since the night of 17 October, the amplitude of the tremor signal had decreased slowly. On 18 October, deformation further decreased and the sea-surface disruption from gases was not observed.

Sources: Instituto Geográfico Nacional (IGN)

5 October 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported more than 700 new seismic events were detected at Hierro during 4-11 October, 52 of them were felt by residents. A M 4.3 earthquake was detected on 8 October, located 1.5 km from the SW coast of the island at 14 km depth. Following the event, the trend of the superficial deformation changed, suggesting deflation of the system. During the night of 8 October through the following day, low-magnitude seismic events occurred at depths of less than 2 km. Since 0515 on 10 October volcanic tremor was clearly recorded by all of the seismic stations on the island, with highest amplitudes recorded in the southernmost station. All data suggested a submarine eruption.

On 11 October at about 0700 the amplitude of the tremor increased. During that morning residents on the S of the island reported feeling vibrations. After midday, the Government of the Canary Islands raised the Alert Code to Red for Restinga village (at the southernmost point of Hierro) and evacuated the residents. A maritime exclusion zone extended about 4 nautical miles from Restinga.

Sources: Instituto Geográfico Nacional (IGN)

28 September 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported a drastic increase in the seismic activity at Hierro during 27 September-3 October, with more than 1,100 new seismic events detected, 83 of them felt by residents, with a maximum intensity value of IV using EMS-98 (European Macroseismic Scale). Most of the hypocenters were located offshore, SW of the island, at around 14 km depth. The maximum magnitude recorded during this week was 3.8. The total number of located events had reached more than 9,300 since the anomalous activity began on 16 July. The superficial deformation measured by the GPS network had reached 35 mm.

Sources: Instituto Geográfico Nacional (IGN)

21 September 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported more than 900 new seismic events at Hierro during 20-26 September, five of them felt by residents. The maximum magnitude recorded was 3.4. The total number of located events had reached more than 8,100 since the anomalous activity began on 16 July. The rates of both GPS deformation and seismic energy release had significantly increased during the previous seven days. On 23 September, the Canarian Autonomous Government raised the Alert Code to Yellow.

Sources: Instituto Geográfico Nacional (IGN)

14 September 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported more than 900 seismic events at Hierro island during 8-19 September, three of them felt by residents. The total number of located earthquakes had reached more than 7,200 since anomalous activity began on 16 July, with patterns alternating between relatively calm and high-energy periods. The GPS local network showed similar deformation rates compared to previous weeks.

Sources: Instituto Geográfico Nacional (IGN)

7 September 2011              Back to Top

Instituto Geográfico Nacional (IGN) reported that since 16 July, seismicity at Hierro was high above the background levels. Until 7 September more than 6,200 events had been located, most of them in the El Golfo area with hypocenters that were 10 km deep, all magnitudes were below 3. The seismic activity alternated between relatively calm periods and high-energy periods. GPS local network stations showed deformations of about 2 cm. High rates of carbon dioxide flux were measured in the anomalous area.

Sources: Instituto Geográfico Nacional (IGN)



Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1793 May ] [ 1793 Jun ] Uncertain 0   NW rift (Volcán de Lomo Negro)?
[ 1692 ] [ Unknown ] Uncertain    
[ 1677 ] [ Unknown ] Uncertain    
550 BCE ± 75 years Unknown Confirmed   Radiocarbon (uncorrected) Montañas Chamuscada-Entremontañas
950 BCE ± 150 years Unknown Confirmed   Radiocarbon (uncorrected) East flank (Soliman)
4790 BCE (?) Unknown Confirmed   Radiocarbon (uncorrected)

The triangular island of Hierro is the SW-most and least studied of the Canary Islands. The massive Hierro shield volcano is truncated by a large NW-facing escarpment formed as a result of gravitational collapse of El Golfo volcano about 130,000 years ago. The steep-sided 1500-m-high scarp towers above a low lava platform bordering 12-km-wide El Golfo Bay, and three other large submarine landslide deposits occur to the SW and SE. Three prominent rifts oriented NW, NE, and south at 120 degree angles form prominent topographic ridges. The subaerial portion of the volcano consists of flat-lying Quaternary basaltic and trachybasaltic lava flows and tuffs capped by numerous young cinder cones and lava flows. Holocene cones and flows are found both on the outer flanks and in the El Golfo depression. Hierro contains the greatest concentration of young vents in the Canary Islands. Uncertainty surrounds the report of an historical eruption in 1793.