No surface deformation detected

A March 1996 EDM survey of the active Cumbre Vieja rift volcano indicated no significant surface deformation since installation of the network in October 1994. The network contains 11 benchmarks (incorporating two Spanish survey triangulation pillars) and was measured using the infrared EDM method. Together with one 3-component seismic station NE of the main rift, the network provides the only current means of monitoring activity on the island.

The deformation network covers the area affected by faulting associated with the July 1949 eruption (figure 1), a zone where W-facing normal faults showed a maximum vertical displacement of ~4 m. The Cumbre Vieja ridge lies between the two 1949 eruptive centers (Duraznero and San Juan). Eyewitness accounts (Bonnelli, 1950) and detailed mapping of the eruptive products showed that during the 1949 eruption, fault displacements also had westward components with downslope movement on the volcano's flanks. La Palma is comparable in form and structure to other Canary Islands that have undergone large-scale slope failure. Steep topography, together with the prospect of a future magma intrusion, cause concern for the long-term stability of the Cumbre Vieja ridge.

Figure 1. Sketch map of the Cumbre Vieja rift volcano showing the distribution of benchmarks, vents, and faults associated with the July 1949 eruption at La Palma. Courtesy of J.L. Moss and W.J. McGuire.

The wedge-shaped island of La Palma contains two large volcanic centers. The northern one is cut by the massive Caldera Taburiente. The southern Cumbre Vieja rift volcano, oriented N-S, has been the site of historical eruptions recorded since the 15th century. An eruption from the S tip of La Palma in 1971 produced the Teneguia cinder cone. Fissure-fed eruptions from vents ~1 km S of the 1677 San Antonio cone produced lava flows that reached the SW coast.

Reference. Bonnelli, R., 1950, Contribucion al estudio de la erupcion del volcan del Nambroque o San Juan (Isla de la Palma), 24 de Junio - Agosto de 1949: Instituto Geografico y Catastral, Madrid, Spain.

Information Contacts: J.L. Moss, W.J. McGuire, and S.J. Day, Center for Volcanic Research, Cheltenham & Gloucester College, Francis Close Hall, Swindon Road, Cheltenham GL50 4AZ, United Kingdom; S.J. Saunders, Brunel University, Department of Geography & Earth Science, Borough Road, Isleworth, Middlesex TW7 5DU, United Kingdom; J-C. Carracedo, Estacion Volcanologica de las Canarias, Tigua Carretera de la Esperanza 3, Apartado de Correos 195, 38206 La Laguna, Tenerife, Canary Islands, Spain.

Information is preliminary and subject to change. All times are local (unless otherwise noted)

October 1971 (CSLP 90-71)

Eruption produces lava fountains from three vents

Card 1305 (27 October 1971) Gas and tephra emission after several days of seismicity

The following cable was received from E.M. Fournier d'Albe on 27 October. "On 26 October after several days microseismic activity fissures opened in southern extremity Isla de La Palma Canaries with emission of gases and ejection rock fragments. No lava emission yet observed. Spanish Institute Geological Research sending team to observe eruption."

Card 1307 (28 October 1971) Three vents generated lava fountains and flows that reached the sea

The following cable was received from E.M. Fournier d'Albe on 28 October. "On 26 October 1640 GMT through the opened fissure mentioned in the previous report emission of gases and tephra started. Three main vents are working simultaneously. The vents evolved to lava fountains and formed two main lava flows which reached the sea at the southern tip of the island. Prof. Fuster and teams from Research Council of spain and University of Madrid and La Languna will arrive at La Palma 27 and 28 October."

Information Contacts: Card 1305 (27 October 1971)Jose M. Fuster-Casas, University of Madrid, Spain; E.M. Fournier d'Albe, UNESCO, Paris, France.
Card 1307 (28 October 1971)Jose M. Fuster-Casas, University of Madrid, Spain; E.M. Fournier d'Albe, UNESCO, Paris, France.

November 1971 (CSLP 90-71)

Activity from six different vents through 18 November builds Teneguia cone

Card 1309 (02 November 1971) Northern vent builds spatter cone 180 m high

". . . during 28 through 30 October only three vents were active. The fracture is 300 m long, its strike being 345 degrees. The northern vent throws lapilli and large bombs to a height of 500-700 m. It has a rhythm of 45 pulses per minute. This vent has built a spatter cone 180 m high and has spread a thin cover of lapilli over the area SE of the cone. The southern vent only throws bombs and scoriae. Lava is emitted through the upper vent and through a point in the middle of the fracture of the southern end of the island 2,500 m away from the vent. The flows from the central vent reached the sea forming a new platform. The lavas are alkaline basalts with hornblende phenocrysts. Casualties have happened but there is very little damage reported by Fuster."

Card 1310 (04 November 1971) Description of lava composition

The following cable from Professor Fuster was received on 4 November. "Teneguia volcano mineralogical lava composition 10 per cent of phenocrysts, including 5 DF augite 3 of basaltic hornblende of ore. Ninety per cent matrix containing mainly ore and augite and less abundant plagioclase microlites. Some samples have the same phenocrysts in a glassy matrix with plagioclase microlites."

Card 1311-1311a (04 November 1971) Eruptions and lava flows during 31 October-4 November

The following report was received through the courtesy of the Office of Naval Research, Washington, D.C., via Carl Hartdegen, Associate Director, Palisades Geophysical Institute, Sofar Station, Bermuda Island, who telephoned the Center and gave the following report radioed from the Hydrophone Station, La Palma, Canary Islands.

31 October. The activity of the fissure is located in two vents; the northern one, Teneguia One, is the most active erupting thick blocky lava flows which reached the sea to the E of the lighthouse of Fuencaliente. The emission of scoria bombs and lapillus is practically continous. The cinder and spatter cone that has been formed reaches 150 m and changes its form very quickly. The southern vent, Teneguia Two, emits only blocky lava flows which fall from the sea cliff to the sea. An exogenous dome is forming in this area, south of Teneguia One.

1 November. The activity of hot vents increases. Teneguia One emits a less viscous lava and the dome in the area of Teneguia Two also grows. At noon a new vent, Teneguia Three, opened 300 m to the north of Teneguia One. This vent erupts intermittently bombs and scoria bombs but no lava flow. During the afternoon in the Teneguia Two dome, multiple fissures began to appear and it started to collapse, fracture, and slumping slowly to the SE.

2 November. The activity of Teneguia One is similar to the previous days. Teneguia Three increases its activity during the morning, decreases the frequency and magnitude of the explosion in the afternoon. During the night it emits only gases. The dome of Teneguia Two has changed to a huge heap of lava block with secondary lava flows.

3 November. Teneguia Two emits very viscous lava flow and continues to emit bombs and lapillus relatively slowly 1-3 m/hour in the frontal part. Teneguia Three emits only some gases. Teneguia One also less active than yesterday. " The lava of the eruption is always anchibrolic trachy basalt and changes with time to a more vesicular type reported by Fuster-Casas."

The following report from Dr. Fuster-Casas was relayed to the Center by Leslie Schofield, Palisades Geophysical Institute, on 5 November.

4 November. The most important vent, Teneguia One, has emitted abundant lava flows that are always of block type. The flows have reached the seas to the E of the lighthouse. Aerial projections are less abundant than previous days. The other vents, Teneguia II and Teneguia III have been inactive and emitted only gases."

Card 1314-1314a (08 November 1971) Activity continues during 5-7 November; lava flows reach the sea

The following report was received through the courtesy of the Office of Naval Research, Washington, D.C.

5 November. Teneguia No. 1 has continued its activity of aerial projection and lava emission. A vertical crack has grown from the rim to the base of its cone. The cone has reached at this moment about 100 m from the surrounding plain. Teneguia No. 2 has had intermittent outbursts of aerial projection and during the night of 5-6 Nov. had enormous quantity of lava running in four lava flows from the western sea-cliff to the sea. Teneguia No. 3 has emitted only a little smoke and in an intermittent way.

6 November. During the early hours of this morning all the southern wall of the cone of the main vent, Teneguia No. 1, collapsed, and now the direction of the lava flows from this vent runs to the south towards Teneguia No. 2. At 1245 GMT all the materials of the former cones between Teneguia No. 1 and Teneguia No. 2 collapsed and a new cloud of pyrotechnic dust and gases at high temperatures ascended from this place falling over SW seaslope. This cloud ran also in NW direction along the western coast of island. During the afternoon and evening continous lava flows from Teneguia No. 1 and Teneguia No. 2 reached the sea on the SW coast.

7 November. The only change in the activity of Teneguia Volcano, that continues its aerial projections and outbursts of lava, is the apparition of fumaroles at crack in the western slopes of Teneguia No. 1 vent.

Card 1315 (10 November 1971) New vent opens on 9 November with strong bomb ejections

The following report was transmitted from Dr. Fuster-Casas.

8 November. The activity of Teneguia Volcano remains as during 7 November. Teneguia One vent emits abundant blocky lava which reaches the sea W of Fuencaliente lighthouse and projects continously lapilli and lava bombs. Teneguia Two and Three remain inactive. The fissures between Teneguia One and Three are growing steadily and new ones began to appear on the SW slope of the cone of Teneguia Three. The fissures emitt abundant white gases, rich in SO₂.

9 November. At 2200 last night a new vent, Teneguia Four, was opened in the N-S fissure located in the place where the fumaroles were stronger. The new vent consists of three openings that emit gases at great pressures and project lava bombs 100 to 150 m high. During the night the three openings have built a spatter cone 20 m high and changed into a double jet that ejects two columns of incandescent gases and pulverized lava at a great pressure. The double jet sounds like the engine of a jet plane taking off. The activity of fumarolic area is growing and Teneguia One remains as in former days. Teneguia Two and Three remain inactive."

Card 1316 (12 November 1971) Increased activity at all active centers

The following report from Dr. Fuster-Casas was telephoned to the Center by Kevin Laudadio.

10 November. Teneguia One emits more lapilli than preceding days. The lava flowing from its center is more viscous and flows very slowly, forming blocks 5 to 25 m long. The lapilli shower is more abundant in the north SW zone of the volcano.

Teneguia Four continues acting as a powerful jet engine expelling a moderate amount of lava lumps and lapilli; the spatter cone formed around the double vent coalesces with the N slope of Teneguia One cone.

At 0345Z a little vent was opened 75 m ENE of Teneguia IV vent in the fumarolic area located between Teneguia One and Teneguia Three cones. The white gases of the fumarole formed white sulfur deposits in the surrounding field.

The activity of fumarole increased until 2200 Z but afterwards production of gases was smaller.

In the last hours of the day activity of all active centers inreased: Teneguia One emits abundant fluid lava through five or more points in the N-S fissure. In the Teneguia Four NE zone, five little vents are acting in the same forrm and rhythm as Teneguia Four.

Card 1317-1317a (15 November 1971) Continued activity from six centers during 11-14 November

The following report from Dr. Fuster-Casas was received on 15 November.

11 November. Teneguia One was very active during all the day. The effusion of the fluid lava started last night changed to a more viscous lava early this morning. During all the day projected continously lava fragments up to 400 m high. Teneguia Four acted exactly like the previous day increasing its activity from 2240 Z on. The new vents opened have formed two small spatter cones in the N slope of Teneguia Five, which started with two openings ended with one. The other one, Teneguia Six, had a single opening. Both centers were very active, expelling a powerful jet of gas and fragments of lava and emitting two small lava flows in a northeasterly direction at 0700 Z. The fumarole field has the same intensity as the last hours of yesterday.

12 November. Teneguia One, Four, and Five are sending lava lumps, scoria and lapilli continously. Teneguia One produces pyroclastic material with about 20 pulses per minute. Teneguia Four and Five alternate in periods with pulsating emissions and periods of continuous jet emission, and periods of continous jet emission, jointed by big noise. The spatter cone of Teneguia Four and Five are growing continuously reaching 50 and 25 m respectively; they coalesce with Teneguia One cone which reaches about 110 m.

Teneguia Six spatter cone is being buried by Teneguia Five. The lapilli and scoria from the vents have changed to a more vitreous black and vesiculated-type which floats on the sea; there are some fragments of white pumice, perhaps formed by fussion of phonolitic rock of the substrata.

Teneguia One keeps the emission of viscous lava which reaches the sea on the W coast. Teneguia Five has produced some short flows.

13 November. In the morning Teneguia Four emitted abundant lava which reached the W coast in the afternoon. Meanwhile, Teneguia One increases its activity emitting more lava than usual; this lava flows to the W coast by four branches. The lava is more fluid and has some olivine phenyl crystals. The aerial projections are abundant in all active vents, Teneguia Four, Five, and Six. After 2000 Z the emission of lava is less abundant.

14 November. The intensity of the eruption was less strong than yesterday. Teneguia One emits lava, lapilli and bombs. Teneguia Four, Five and Six emit only lapilli and some bombs and scoria."

Card 1318-1318a (19 November 1971) Complex cone growth and collapses during intense activity

The following report from Dr. Fuster-Casas was received on 19 November.

15 November. The activity of the volcano increased during the morning but maintained the same characteristics as the previous day. Teneguia One vents were pouring lava flows in an intermittent way. Teneguia Four and Five alternate the projection of jets of gases with the emission of clouds of lapilli. After a period of being practically inactive, at 1245 Z that lasted about half an hour, the Teneguia Five erupted a big lava flow that nearly reached the road to the lighthouse of Fuencaliente in a southeasterly direction. During the afternoon Teneguia One and Teneguia Four were increasing their activity with continuous projection of scoria and bombs that continued until midnight. The scoria and cinder cones of Teneguia One, Four, Five, and Six coalesced. The height is 125 m on the previous ground.

16 November. The activity of the several craters was intense. Teneguia One continues pouring blocky lava in six flows which increase in velocity in the scarp, adjoining the W coast where the lava is forming six blocky deposits. Teneguia Four is as active as Teneguia One, forming an elongated crater with at least four projection points--a line in a NW direction. Teneguia Six is acting in the same way with three or four projection points--a line in a NNE trend--and was pouring lava from their bases.

Teneguia Five was less active. Between Teneguia Four and Teneguia Five there are two little openings which emit continous bright flames and a few lava blocks. Teneguia One and Four send intermittently big columns of scoria and lapilli which cover the previous lava flows and the surroundings especially in the SE direction. Teneguia Six projects mainly scoria and lava lumps. The lava is changing to a more olivine type.

17 November. During the night of the 16th to the 17th the cone of Teneguia Four has grown steadily and buried the vents of Teneguia Five and Teneguia Six. A new opening was formed just under the NE rim of this crater. The whole day both Teneguia One and Four have continued emission of aerial projections with enormous amounts of lapilli and lava flows, the former one in a more intermittent and less powerful way. The lava from Teneguia Four is forming an intense platform at the foot of the W sea cliff that penetrates into the sea. During the afternoon a part of the N rim of the Teneguia Four vent collapsed under its own weight and its incandescent materials originated a big secondary flow of semi-fluid scoria and lava that filled the area between the main volcano and the little cone of Teneguia Three.

18 November. At 0130 Z Teneguia six started to produce fluid lava flows from an opening at the cone base. Teneguia Four decreased its lava emission. Teneguia One, Four and Six project simultaneously scoria, lapilli, and lava lumps; Teneguia One and Six with pulses, Teneguia Four continuously. Until noon Teneguia Six had periods of fast production of lava flows and periods of attenuated activity; until midnight only activity was emission of moderate amounts of gas from the vents. Seismic agitation stopped at the same time as the volcanic activity.

Information Contacts: Card 1309 (02 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Sr. Firmado, special delegate of the government of the Canary Islands.
Card 1310 (04 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain.
Card 1311-1311a (04 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Carl Hartdegen, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1314-1314a (08 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1315 (10 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1316 (12 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1317-1317a (15 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.
Card 1318-1318a (19 November 1971)Jose M. Fuster-Casas, Instituto Lucas Mallada, Madrid, Spain; Palisades Hydrophone Station, La Palma Island, Canary Islands, Spain; Kevin Laudadio, Palisades Geophysical Institute Sofar Station, Bermuda.

June 1996 (BGVN 21:06) Cite this Report

No surface deformation detected

A March 1996 EDM survey of the active Cumbre Vieja rift volcano indicated no significant surface deformation since installation of the network in October 1994. The network contains 11 benchmarks (incorporating two Spanish survey triangulation pillars) and was measured using the infrared EDM method. Together with one 3-component seismic station NE of the main rift, the network provides the only current means of monitoring activity on the island.

The deformation network covers the area affected by faulting associated with the July 1949 eruption (figure 1), a zone where W-facing normal faults showed a maximum vertical displacement of ~4 m. The Cumbre Vieja ridge lies between the two 1949 eruptive centers (Duraznero and San Juan). Eyewitness accounts (Bonnelli, 1950) and detailed mapping of the eruptive products showed that during the 1949 eruption, fault displacements also had westward components with downslope movement on the volcano's flanks. La Palma is comparable in form and structure to other Canary Islands that have undergone large-scale slope failure. Steep topography, together with the prospect of a future magma intrusion, cause concern for the long-term stability of the Cumbre Vieja ridge.

Figure 1. Sketch map of the Cumbre Vieja rift volcano showing the distribution of benchmarks, vents, and faults associated with the July 1949 eruption at La Palma. Courtesy of J.L. Moss and W.J. McGuire.

The wedge-shaped island of La Palma contains two large volcanic centers. The northern one is cut by the massive Caldera Taburiente. The southern Cumbre Vieja rift volcano, oriented N-S, has been the site of historical eruptions recorded since the 15th century. An eruption from the S tip of La Palma in 1971 produced the Teneguia cinder cone. Fissure-fed eruptions from vents ~1 km S of the 1677 San Antonio cone produced lava flows that reached the SW coast.

Reference. Bonnelli, R., 1950, Contribucion al estudio de la erupcion del volcan del Nambroque o San Juan (Isla de la Palma), 24 de Junio - Agosto de 1949: Instituto Geografico y Catastral, Madrid, Spain.

Information Contacts: J.L. Moss, W.J. McGuire, and S.J. Day, Center for Volcanic Research, Cheltenham & Gloucester College, Francis Close Hall, Swindon Road, Cheltenham GL50 4AZ, United Kingdom; S.J. Saunders, Brunel University, Department of Geography & Earth Science, Borough Road, Isleworth, Middlesex TW7 5DU, United Kingdom; J-C. Carracedo, Estacion Volcanologica de las Canarias, Tigua Carretera de la Esperanza 3, Apartado de Correos 195, 38206 La Laguna, Tenerife, Canary Islands, Spain.