Category Archives: Europe

São Jorge Earthquake Swarm, Update 07.04.2022

Good morning!

The earthquake swarm is continuing on São Jorge as we write, albeit it at a much lower intensity.  The swarm is located on the Manadas Fissure system.  INVOLCAN has sent a team to assist the local scientists (CIVISA and IVAR).   CIVISA advised on 6 April 2022 that volcano-tectonic earthquakes had been detected suggesting magma movement at depth.

Fig 1: Image of Fajã dos Cubres, São Jorge, Azores, cropped from one by Jules Verne Times Two.  Published under CC BY-SA 4.0 (Source: São Jorge Island – Wikipedia).

While we wait to see what transpires, here are some statistics.

  • Number of earthquakes ≥2.0 reported on IPMA’s site: 793
  • Maximum number: 127 on 20 March 2022
  • Minimum number: 5 on 31/03/2022 and 06/04/2022 (7/04/2022 is not a complete day)
  • Maximum magnitude: 4.0 (29/03/2022, 21:56:16, 38.686°N, 28.215°W, 10km)
  • Maximum depth: 26km on 20 March 2022 and 28km on 28 March 2022.
Fig 2: Number of earthquakes by day by the author.  © remains with the author; all rights reserved, 2022.
Fig 3: Earthquake depth and magnitude by day by the author. © copyright remains with the author; all rights reserved, 2022.

We have updated our earthquake plots for 38.548°N, 27.677°W to 38.769°N, 28.350°W from 19th March 2022 to 7th April 2022.

Fig 4: Video of geoscatter and scatter plots of the earthquake swarm from 19th March 2022 to 7th April 2022.  Keys are in the video. © copyright remains with the author; all rights reserved, 2022.

Armchair Volcanologist

© copyright remains with the author; all rights reserved, 2022.

Sources

 IPMA – Seismic Map (for raw earthquake data)

Volcano-tectonic tremors recorded for first time on quake-hit Azores island | Reuters

São Jorge, Large Earthquake Swarm May Herald an Eruption or Large Earthquake

Good Afternoon! (Updated 30/03/2022 to include Background)

On 19 March 2022 an earthquake swarm started on São Jorge, an island in the Azores.  The swarm is ongoing at the time of writing.  By 28 March 2022, c.14,000 earthquakes had been recorded.   This swarm is likely to be caused by a magmatic intrusion. 

Fig 1: Image of Fajã dos Cubres, São Jorge, Azores, cropped from one by Jules Verne Times Two.  Published under CC BY-SA 4.0 (Source: São Jorge Island – Wikipedia).

INVOLCAN have estimated that up to 20 million cubic meters of magma may have accumulated under São Jorge during the swarm, based on satellite measurements of ground deformation.  CIVISA (Centro de Informação e Vigilância Sismovulcânica dos Açores) has raised the alert level to V4 (out of a scale to V6. V5 and V6 are in eruption, based on size of the eruption).

There are four likely outcomes:

  1. An eruption occurs in the next few days to weeks, possibly with little warning.
  2. A larger earthquake occurs alongside changes in the magma intrusion leading to an eruption or stalling of the intrusion.
  3. The current swarm and deformation end without eruption.  Future swarms and deformation lead to an eruption.
  4. The activity ceases and the intrusion cools with no further activity.

Locals have been advised to prepare to evacuate due to the risk of eruption or larger earthquakes.  Our thoughts are with them.

Let’s take a look at what is going on underground.  We have downloaded the earthquake data reported by The Portuguese Institute for Sea and Atmosphere, I. P. (Source: IPMA – Seismic map).  This shows earthquakes ≥2.0 magnitude.  At the time of our download c. 840 earthquakes ≥2.0 had been recorded for São Jorge from 19/03/2022. 

 Our video shows geoscatter plots by day, showing the north-westward migration of the swarm, and 3D rotating scatter plots.

Fig 2:  Video by the author of earthquake plots for São Jorge from 19th March 2022 to 29th March 2022 (am) (earthquake greater than or equal to 2.0 magnitude) .  © copyright remains with the author; all rights reserved, 2022.

Background

Around 8,400 people live on the island in settlements around the coast.  Transport links have historical been by sea as land transport was inhibited by the harsh volcanic terrain. The economy is reliant on dairy farming, including the export of São Jorge cheese, fishing and some cereals, vineyards and local vegetables. The opening of an airport in 1982 led to the expansion of the export of cheese, farming and small crafts.

São Jorge Island, itself, is 55km long and 6km wide volcanic ridge in the Azores Archipelago.  The Azores are located at a triple junction between the North American, Eurasian and Nubian Plates; the Mid Atlantic Ridge forms the eastern boundary of the North American Plate. The Azores Plateau is considered to be a large igneous province generated from a plume interacting with the Mid Atlantic Ridge between 20 and 7 million years ago. Fissural volcanic activity arising from the interaction and tectonics created the islands.

There are four known centres of volcanic activity on São Jorge: the São João area on the south eastern end of the island; the Topo Volcanic Complex, occupying most of the eastern side of the island; the Rosais Volcanic Complex, with basalt and andesites; and Manadas Volcanic Complex on the west side of the island. The earliest known subaerial lava is alkaline enriched  c.1.32 – c.1.21 million years old from deep partial melting of an enriched  garnet peridotite mantle source. This is located at the south east end of the island at São João with a NW-SE to NNW-SSE direction oblique to the current WNW -ESE axis of the island. The period includes at least thee episodes of magma differentiation from alkaline basalts to mugearites in a shallow magma reservoir.  Subaerial activity resumed c. 750,000 years ago at the Topo Volcanic Complex, with several overlapping episodes migrating westward along the axis of the island. Activity in the western side of the island started c. 731,000 years ago. The lavas generated 750,000 years ago and subsequently were also generated from an enriched mantle source.  The different phases of subaerial growth are attributed to different episodes of deformation reopening the magma feeding system. It is possible that submarine activity occurred during the period of apparent quiescence.

GVP lists 11 confirmed Holocene eruptions for São Jorge, of which one is VEI 3 (1580), one is VEI 2 (1800) and one is VEI 1 (1808).  Three are submarine: 1964, off the SW coast; 1902, off Ponta do Topo; and, 1800, also off Ponto do Topo.  The eruptions in 1580 and 1808 caused widespread damage. In the 1580 eruption, magma ascended from 23km or more, ponded at 16km and then erupted in three lava flows along the Ribeira da Almeida, Queimada and between Ribeiro do Nabo and the beach of Cruzes;  ten people were killed.  In the Urzelina eruption in 1808 , fractionated residual ponded magma from the 1580 eruption emerged as andesite-basaltic lava to flow south west of Pico do Pedro to Urzelina.  This eruption caused gases and chloric, sulfuric and carboxylic acid vapours to be emitted from the Manadas Ridge, which along with eight large earthquakes, caused significant damage to property and farmland.  Eight people were killed in the 1808 eruption.

The island and surrounding area is heavily faulted.  Submarine fractures between the São Jorge and Pico have resulted  in large damaging earthquakes.  In 1757, an earthquake centred in Fajã dos Vimes resulted in destruction of property in Manadas and the death of c. 20% of its population (1,000 people).  

A series of seismic swarms in February 1964 associated with an offshore eruption 6.5km northwest of Velas led to large earthquakes which destroyed most property in the western side of the island.  The eruption was preceded by seismic activity starting tremors felt on 21 August 1963, followed by a swarm which lasted from mid-December 1963 to January 1964 and the cutting of submarine cables on 29 January and 1 February 1964.  Volcanic tremors started on 14 February 1964, resulting in a large damaging  earthquake on 15 February after a lull in activity.   The earthquakes initially impacted Urzelina, Manadas, San António and Norte Grand before migrating north west to include Rosais, Beira, Velas, and Santa Amaro.  Low intensity tremors occurred in the period before the next large events on 21 February 1964 when three large tremors caused more damage; this phase ended on 24 February 1964.  Earthquake foci near the centre of the island had depths of 5km, whereas those near Velas were 10-20km in depth.  Neighbouring islands also experienced large tremors.  The event ended on 25 February 1964. 5,000 people were evacuated from the island during this time, not an easy task as storms in the channel between Terceira, Pico an b d Faial hampered relief efforts, along with lack of planning. This time with monitoring the authorities are better prepared.

Time will tell when the next eruption occurs on São Jorge.  In the meantime, here’s hoping that the disruption to local residents is short-lived.

Armchair Volcanologist

© copyright remains with the author; all rights reserved, 2022.

Sources and Further Reading:

Anthony Hildebrand, Pedro Madureira, Fernando Ornelas Marques, Inês Cruz, Bernard Henry, Pedro Silva, “Multi-stage evolution of a subaerial volcanic ridge over the last 1.3 Myr: S. Jorge Island, Azores Triple Junction”, Earth and Planetary Science Letters, Volume 273, Issues 3-4, 15 September 2008, Pages 289 -298.

Anthony Hildebrand, Dominique Weis, Pedro Madueira, Fernando Ornelas Marques, “Recent plate re-organisation at the Azores Triple Junction: Evidence from combined geochemical and geochronological data on Faial, S. Jorge and Terceira volcanic islands”, Lithos, 210-211, (2014), 27-39.

Vittorio Zanon, Fátima Vieros, “A multi-method re-evaluation of the volcanic events during 1580 CE and 1808 eruptions at São Jorge Island (Azores Archipelago, Portugal), Journal of Volcanology and Geothermal Research, Volume 373, 15 March 2019, Pages 51–67.

Smithsonian Institution National Museum of Natural History Global Volcanism Program (GVP): São Jorge https://volcano.si.edu/volcano.cfm?vn=382030

1964 Rosais earthquake – Wikipedia

São Jorge Island – Wikipedia

Mount Etna, Not One Volcano But Many

Part 1: Tectonic Setting and History

Good Afternoon!

Fig 1:  Cropped image of Mount Etna with Catania in the foreground from a photo by BenAveling in 2007, published under CC BY-SA 4.0.  Source: Mount Etna – Wikipedia

Today we are looking at Mount Etna, Europe’s largest and most active volcano, sited on the eastern side of Sicily. Sicily has been at the heart of many Mediterranean trading routes. As a result, the volcano has been widely studied.  Etna has been designated a Decade Volcano by the UN.  She is home to indigenous species, Etna Broom, which thrives on its lower slopes.  In 2013, she was designated a UNESCO World Heritage Site.

Apart from the widely reported recent activity, she caught our eye because of the interesting tectonic setting between the African Plate, Eurasian Plate, Adriatic Plate and additional micro-plates.  The area has some of the deepest subduction in the Mediterranean region.  We start with her tectonic setting.

Fig 2: Cropped from an image by Velela of Etna Broom, published under CC BY-SA 3.0.  Source: EtnaBroom8142 – Genista aetnensis – Wikipedia

Mount Etna is a c.3,320m high complex volcano with four summit craters: the North East, Voragine, Bocca Nuova and the South East Craters and many cinder cones.  The volcano is made up of an old shield volcano, topped by stratovolcanoes, Ellittico and  Mongibello. It is truncated by small nested calderas. 

The volcano has erupted basalts, viscous granitic lava, trachyte and again basalt.  The last is rich in iron with microscopic gold particles.  The basalt is used for building and sculpture.  Until health and safety concerns banned it, the fluid lava was collected to be made into souvenirs  for tourists. 

The source for Etna’s lavas is not clear.  You will see from our earthquake plots below that there is little evidence of subduction beneath Etna, herself, although there is clear evidence of subduction beneath the neighbouring Aeolian Arc.  Various theories have been proposed: rifting; a hot spot; and, the intersection of breaks in the crust associated with the subduction of the African Plate under the Eurasian Plate, providing a channel for magma.

Tectonic Setting

The collision of the Eurasian and African Plate has a complex history. In the vicinity of Sicily, the Tyrrhenian and Ionian Seas opened, the Aeolian – Calabrian Arc suffered subduction, bending and compression and the edge of the Eurasian Plate was thrust over the edge of the African Plate.  The Adriatic Plate broke off and the Ionian Plate was subducted under the Tyrrhenian Sea.

Sicily

The main tectonic features of Sicily are the crystalline units of the Calabrian arc; the Neogene Maghrebian fold and thrust belt created during the opening of the Tyrrhenian Basin; the Catania – Gela foredeep; and the Hyblean Plateau. 

Fig 3:  Map by FieldsetJ, published under CC BY-SA 4.0.  Source: Geology of Sicily – Wikipedia

The Calabrian Arc unit is located in the north eastern part of Sicily.  It is the tectonic unit that connects the Apennines with the North African Maghrebide.  The Arc migrated to the south east, driven by the subduction of the Ionian slab east of Sicily.  In the early Miocene, Calabria was attached to Sardinia.  Trench roll back to the east and extension in the middle Miocene, caused Calabria to break off from Sardinia. By the early Pliocene, back arc volcanism relating to subduction of the Ionian slab had created new crust in the Tyrrhenian Sea.  From the Pleistocene, the eastern portion of the Arc formed the Apennine mountains in Italy, while the Calabrian block had migrated to Sicily.  The migration is ongoing.  Palaeozoic igneous and metamorphic basement rocks are exposed at this part of the island.  Triassic late Cretaceous carbonate is overlain by Paleogene – Middle Miocene turbidites, Middle Miocene to – Messinian rift deposits, Messinian evaporites and early Pliocene chalk.

The Maghrebian fold and thrust belt, part of a subduction regime, comprises frontal accretion and detached nappes of Mesozoic carbonate, which has been folded in to a syncline, underlying the anticline of the Caltanissetta region.

The Catania – Gela foredeep extends from the northern margin of the Hyblean Plateau to the offshore Gela basin of southwestern Sicily.  It was formed due to bending of the carbonate platform caused by loading at the front of the Gela nappe.  In the late Miocene – Pleistocene sediments were deposited, including limestones, evaporites and sandy clays.

The Hyblean Plateau is on the Nubian Plate. In the early Miocene, regional uplift caused by thrusting and volcanism resulting in the emergence of a carbonate platform in the eastern Hyblean Plateau.  In the late Miocene, sea level fall and uplift caused the deposition of evaporites in the Mediterranean basin.  This was followed by subsidence in the foreland and deposition of sediments.  In the late Miocene – early Pleistocene, basaltic volcanic activity occurred; alkaline basalts were erupted during the late Miocene.  In the late Pliocene, large volumes of tholeiitic basalt was erupted and the foredeep north of the Hyblean foreland collapsed.

Mastrolembo et al(1) found evidence for independent lithospheric blocks by studying GPS velocities relative to the Eurasian and Nubian Plates. The Sicilian domain rotates clockwise with respect to Eurasia and is fragmented into three distinct blocks: the south eastern, the central and the north eastern Sicily blocks, which move independently from the African Plate.  

Fig 4: Plot of earthquakes from 01/10/2004 to 13/02/2022 in eastern Sicily by the author.  Colour denotes earthquake depth: magenta 0 – 33km, green 33km – 70km, yellow 70km – 150km, orange 150km-300km, red 300km – 500km.  Blue triangles denote Holocene volcanoes. The orange triangle denotes Mount Etna.  Earthquake epicentres roughly delineate the boundaries of the tectonic blocks identified by Mastrolembo et al(1): STYR is the South Tyrrhenian block, NESI the North Eastern Sicily block, SC the central Sicily block, SECI the South Eastern Sicily block and CALA Calabria.  The yellow, orange and red dots are the Ionian Plate subducting under STYR.  © Copyright remains with the author; all rights reserved, 2022.

Deep faults transect the island.  Currently, the Tyrrhenian side of Sicily is being compressed and the Ionian side extended.  Mount Etna, itself, is located near to the junction of three major lithospheric faults which may reach the mantle: the east to west Mt Kumeta -Alcantara fault; the north -northeast to south-southwest Messina – Giardini fault which delimits the north coast of Etna; and, the Aeolian-Maltese fault which extends from Vulcano to Malta.

Mount Etna’s History

Mount Etna is a complicated volcanic system; she is thought to have evolved in four stages: 1) tholeiitic basalt; 2) Timpe shield-building; 3) Valle del Bove Central Volcanoes; and 4) Stratovolcanoes.

Tholeiitic Basalt Stage

Earliest activity at Etna has been identified as being the sporadic eruption of tholeiitic pillow lavas from fissures more than 500,000 years ago in the submarine environment of the Gela-Catania foredeep basin at Aci Castello.   300,000 years ago, Na affinity lavas were erupted in fissure eruptions on the alluvial plain of the Simento  River, forming a lava plateau.

Timpe Shield Building Stage

220,000 years ago, extension tectonics of the NNW-trending Timpe fault system drove activity. Sub alkaline – Na alkaline were lavas erupted in fissures along the Ionian coast built a 22 km NNW -SSE aligned shield volcano.  Volcanic activity also occurred to the south west and south east of the location of the now current edifice. 129,000 to 126,000 years ago, activity shifted to a location at the central portion of the location of the current volcano.

A 15km horseshoe depression in the east flank of the edifice was created during this period.  The edifice rested on basement rocks of Miocene argillaceous turbidites in the north and west, but on Pleistocene clay rich marine sediments to the south and the east.  The clays were unable to support the weight of the edifice, resulting in slippage and subsidence to the east. 

Valle Del Bove Central Volcanoes Stage

During this period magma ascent through the crust became more localised, allowing the building stratovolcanoes.  Several monogenetic volcanoes are visible in the Valle del Bove scars. Na-alkaline lavas were erupted.

121,000 years ago, effusive eruptions occurred on the southern edge of the volcano in the N – S aligned  Tarderia and Rocce volcanoes in the Valle Del Bove area.   Activity at Tarderia and Rocce  ended between 106,000 and 102,000 years ago, respectively. 

Trifoglietto volcano was also active at this time.  While the onset of activity at Trifoglietto is not known (there are no rocks outcropping to date), activity is believed to have ended c. 99,000 years ago with explosive benmoreitic Plinian eruptions. 

Activity then shifted to Monte Cerasa, Giannicola, Salifizio and Cuvigghiuni volcanoes.  Monte Cerasa volcano is a large composite stratocone in the central part of the present Valle del Bove with explosive eruptions and pyroclastic flows which transitioned to more effusive eruptions. Activity ceased here 93 ka ago. Giannicola volcano is a 300 m neck intruded in the northern flank of Trifoglietto volcano about 85 ka ago followed by alternating pyroclastic deposits and lava flows.  The main vent Salifizio volcano was located 1 km east of Trifoglietto.  She produced effusive lavas that covered the eastern sides of Trifoglietto and Monte Cerasa. Cuvigghiuni erupted intrusive bodies into the western side of Trifloglietto, followed by lava flows , spatter deposits and pyroclastic flows between c. 80,000 and 65,0000 years ago.  The final stage of her activity was effusive lava flows.

The Valle Del Bove, itself, was created during this period.  Subsidence of the Trifloglietto volcano to the east led to reduction in magma pressure, successive violent hydro-magmatic eruptions and debris avalanche flows which carved out the Valle. 

Stratovolcanoes Stage

In the fourth phase of growth , c. 60,000 years ago, Etna’s magmatic plumbing system had stabilised at its current position.  Two overlapping stratovolcanoes were formed, which form the current upper edfice: Ellittico between 60,000 and 15,000 years ago and Mongibello from 15,000 years ago to present.  Ellittico erupted trachybasalt, followed by mugearites, benmoreites and trachytes, reaching a height of 3,700m before 4 caldera-forming Plinian eruptions signalled the end of activity at Ellittico.

From 15,000 years ago to present, activity at Mongibello has been a mix of lava flows and a few Plinian to sub-Plinian eruptions of basaltic / picritic magma.  Silicic eruptions occurred in 8,460, 7100, 6100, 5000 and 4280 years ago.  In 122BC a Plinian eruption formed the Cratere del Piano, the summit caldera.  Other eruptions were basaltic, filling the caldera and building the cone.

GVP lists 241 Holocene eruptions for Etna, of which 196 have been confirmed.  These include 2 VEI 5, 1 VEI 4, 26 VEI 3, and 167 VEI 2 or less.  The VEI 5’s are the 122BC Cratere del Piano and another in 1500 BC.

Subsidence is continuing on the eastern flanks of the edifice, creating a series of rift faults and fault scarps.

Recent Seismicity

We have plotted earthquakes downloaded from EMSC for the period 1st October 2004 to 13th February 2022 for the area 37°N, 14°E to 39°N, 16°E. 

There is little evidence of a Wadati-Benioff zone under Etna, although the area is seismically active. Our plots clearly show the subducted Ionian slab under the South Tyrrhenian Sea.

Fig 5: Earthquake plots by the author for Southern Italy from 1st October 2004 to 13th February 2022 for the area, 37°N 14°E to 39°N,16°E.  In the left plot green dots denote earthquakes less than 3M, cyan stars over 3M.  In the right plot, colour denotes year.  Blue triangle are Holocene volcanoes, red Pleistocene, orange (left) and black (right), Etna. © Copyright remains with the author; all rights reserved, 2022.
Fig 6: Video of earthquake plots by the author for Southern Italy from 1st October 2004 to 13th February 2022 for the area, 37°N 14°E to 39°N,16°E.  © Copyright remains with the author; all rights reserved, 2022.

An Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2022

Sources & Further Reading

There is no shortage of reading matter about Mount Etna.  A quick internet search will probably fund you what you want.  Here are the resources we used:

  1. 1.       Brunella Mastrolembo Ventura, Enrico Serpelloni, Andrea Argnani, Alessandro Bonforte, Roland Bürgmann, Marco Anzidei, Paolo Baldi, Giuseppe Pulisi, “Fast geodetic strain-rates in eastern Sicily (southern Italy): New insights into block tectonics and seismic potential in the area of the great 1693 earthquake – ScienceDirect”, Earth and Planetary Science Letters 404 (20 14) 77-88.
  2. Stefano Branca, Mauro Coltelli, Emanuela De Beni & Jan Wijbrans , Geological evolution of Mount Etna volcano (Italy) from earliest products until the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data | SpringerLink
  3. Alwyn Scarth, Jean-Claude Tanguy, “Volcanoes of Europe”, Terra Publishing, 2001
  4. Geology of Sicily – Wikipedia
  5. Mount Etna – Wikipedia
  6. Raw earthquake data: https://www.emsc-csem.org/

A Christmas Present for La Palma; Eruption Declared Over 25th  December 2021

Good evening!

There was some good news for La Palma over the week end; the eruption was declared over on 25 December 2021.  The eruption, itself, ended on 13 December 2021 at 22:21.  There was a precautionary period of waiting before announcing the end of the eruption.

This is an important milestone in the process to recover and rebuild.

Fig 1:  Seismic signal showing the end of the eruption. Source: IGN

Statistics

Eruption

The eruption started on 19 September 2021 as a flank eruption on the Cumbre Vieja volcano and ended on 13 December 2021.  The duration of the eruption was 85 days and 8 hours – the longest for which there are historic records.

The eruptive style is described as Strombolian fissural with phreatomagmatic pulses.

The average height of the plume was 3.5km and its the maximum height was 8.5 km on 13 December 2021.

Edifice

The cone’s height is now 1,121m.

There are six craters, with diameters ranging between 106m and 172m.

Lava

200 million cubic meters erupted, covering an area of 1,219 hectares with an average thickness of 12m and maximum width of 3,350m.

The maximum temperature was 1,140°C.

Two lava deltas were created covering c. 48 hectares (one c. 43 hectares and the other 5 hectares).

Damage

2,988 buildings were destroyed and 138 damaged, according to satellite data. This is initially analysed by the local authorities as 1,345 residential properties, 180 agricultural, 75 industrial, 44 leisure, 16 public and 16 other; the shortfall is attributed to properties having more than one building within their boundaries.

Infrastructural damage includes: 73.8 km of road have been damaged along with streets and crossings; and, 130km power lines, 85 medium voltage towers, 1500 low voltage poles and 19 distribution centres.

We do not have an up to date analysis of the extent of the damage to crops and livestock.

Around 7,000 people were evacuated.

There was sadly one fatality which is under investigation.

Seismic Activity

9,135 earthquakes were recorded in the period from 11 September (the onset of the swarm) and today, 27 December 2021.  Due to the severity of the volcanic tremor, many smaller quakes were not recorded.

We have plotted the sequence.  The results are shown in the video below.

Fig 2: Earthquake plots by the author of the swarm from 11/09/2021 to 27/12/2021. © Copyright remains with the author; all rights reserved, 2021.

 Earthquake activity is continuing at the time of writing.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources:

El Time: ElTime.es

Raw earthquake data: Instituto Geográfico Nacional (IGN)

Cumbre Vieja Eruption, Update 19 November 2021

Good evening!

The eruption of Cumbre Vieja continues unabated with Strombolian activity, lava fountains from many vents, lava flows, and ash emissions. .  As of 16 November 2021, Copernicus reported that 1,042.1 hectares of land have been covered by lava.  Rainfall now adds to the hazards created by volcanic ash.  The cone reached a height of 1,130m by 10 November 2021. Sadly, one fatality has occurred; one person who had gone to assist with ash clearance was found dead in his home.

Fig 1: Screenshot on 19/11/2021 from RTVC’s webcam monitoring the eruption.  Source: DIRECTO | Erupción del volcán en La Palma – YouTube

Seismicity picked up again in the last few days along with a ground uplift detected at GPS stations LP03 and LP06.

Fig 2: Earthquake count by day by the author for earthquakes from 11/09/2021 to 19/11/2021 (part day), created from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.
Fig 3: Ground deformation at GPS stations LP03 and LP06.  Source: IGN

 To date there have been 5 earthquakes of 5 Mag. or more.

Fig 4: List of earthquakes greater than or equal to 5 Mag. for earthquakes from 11/09/2021 to 19/11/2021 (part day), extracted from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.

Here are updated earthquake plots.  All of the action is centred around two depths: 7 -16 km and 30 -39 km, with a very few earthquakes in between; there are a few earthquakes with depths of more than 39 km.

Fig 5: Earthquake count by depth by the author for earthquakes from 11/09/2021 to 19/11/2021 (part day), extracted from publicly available earthquake data provided by IGN.  © Copyright remains with the author; all rights reserved, 2021.

For the updated video, we have provided the scatter plots for only earthquakes greater than  or equal to 3.0 Mag. because the smaller earthquakes obscure the action; all earthquakes are included in the geoscatter plots.

Fig 6: Video by the author of geoscatter plots for earthquakes from 11/09/2021 to 19/11/2021 (part day) and scatter plots of earthquakes greater than or equal to 3.0 Mag. for the same period.  © Copyright remains with the author; all rights reserved, 2021.

Magma still appears to be stalling at the two depths: 7 -16 km and 30 -39 km prior to ascent (refer to La Palma: Earthquakes and Magma Plumbing for more information).  How much of it reaches the surface remains to be seen.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources:

Raw earthquake data: Instituto Geográfico Nacional (IGN)

Other links are provided in the text.

La Palma, Update 26.10.2021

Good evening! 

New Earthquake Plots

It has been a week since we updated our last earthquake plots for La Palma so time to take another look.  The eruption has continued in the meantime, with seismicity and seismic signals increasing.  Earthquake activity continues mainly within the two levels 7 -16km and 30 to 42km identified in our previous plots.

Fig 1: screenshots of the eruption 26.10.2021 from local webcams: left, TV Canarias live stream (source: https://www.youtube.com/watch?v=INvrtMg5tSQ); and, right, Hotel Galeon (source: https://eruption.acme.to/slideshow.php?getcam=hotelelgaleon)  (still photos).

Several partial collapses of the main cone have occurred.  The latest was yesterday, releasing a large amount of the lava to the west, which went over existing lava flows.

The latest statistics reported on 26th October 2021 are:

  • 908.2 hectares of land have been affected by lava. 
  • 2,162 buildings haven been destroyed by lava, with a further 124 suffering damage.
  • 66.2km of roads have been lost, with  a further 3.4km damaged.
  • 6,800 hectares of land have been covered by ashfall (reported 22nd October 2021).
  • Cost of lost banana plantations c.100m Euros, 150 hectares are under lava and others are in the exclusion zones; other crops, vineyards and livestock farming are also impacted.
  • SO2 emissions 40,800 tons per day. CO2 emissions up.

In the last 24 hours ground uplift of 10cm has been recorded at the station on the south of the volcano near the eruption site, which the volcanologists monitoring the eruption think may signal an increase in lava flow or the opening of a new vent.

Fig 2: Ground deformation at the station nearest the eruption site.  We have circled the latest data point to make it easier to spot.  Green line marks the onset of the eruption (added by IGN). Source: IGN
Fig 3: Seismic signal today.  Source: IGN

Recent Seismicity

Fig 4:  Plot by the author of earthquake number by day; Day 1 is 1 October 2021, Day 26 is 26 October 2021.  © Copyright remains with the author; all rights reserved, 2021.
Fig 5:  Plot by the author of earthquake depth and magnitude by day; Day 1 is 1 October 2021, Day 26 is 26 October 2021.  © Copyright remains with the author; all rights reserved, 2021.

We have made geoscatter and scatter plots of the swarm from day 21, the onset of the deeper earthquakes.  We have also made plots of the earthquakes over 3.0M, as these tend to get lost in the in the middle level swarm (7-16km). 

Fig 6: Geoscatter and scatter plots of the earthquakes between 1st October 2021 and 26th October 2021 (08:06:14) by the author.  © Copyright remains with the author; all rights reserved, 2021.
Fig 7: Geoscatter and scatter plots of the earthquakes greater than 3.0M between 1st October 2021 and 26th October 2021 (08:06:14) by the author.  © Copyright remains with the author; all rights reserved, 2021.

There are now a few earthquakes between the two swarms but little in the way of reported earthquakes heading for the surface; the latter may mean that lava is flowing freely through the existing conduit, or that a new conduit may be in the offing.  The hike in ground deformation reported above near the eruption site may indicate that whatever ensues, it is likely to be near the current eruption site – speculation on our part.

The eruption is now in its sixth week, lasting longer than recent previous eruptions, with no sign of waning. Has the initial eruption of magma created the right conditions for new magma to erupt from a greater depth, e.g. by creating a pathway for it and/or removing some of the constraining pressure? Only time, and a lot of research by the experts, will tell.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources

News reports: El Mundo,  https://www.elmundo.es  and El Time, https://www.eltime.es/

Raw earthquake data: Instituto Geográfico Nacional (ign.es)

La Palma, 2021: Earthquakes and Magma Plumbing

Fig 1: Screenshot of the main cone of the current eruption, taken 19 October 2021. Source: TV Canarias, https://www.youtube.com/channel/UCTQrUTmzCWIfG6h4EVCdOCQ

We have updated our earthquake plots to 19.10.2021 8:41:10.  Since our previous update there has been more seismic activity, mainly between depths of 9-15km and 32- 42km.  The former is consistent with the initial and subsequent stages of the swarm; the latter is consistent with the deeper earthquakes which started on day 21 (1.10.2021).

Fig 2: Analysis of earthquakes, number by day, by the author for days 32 (12.10.2021) to 39 (19.10.2021) at La Palma.  © Copyright remains with the author; all rights reserved, 2021.

Update earthquake plots are contained in the following video.

Fig 3: Video by the author of geoscatter plots and scatter plots by day of the earthquake swarm on La Palma from day 1 (11.09.2021) to day 39 (19.10.2021).  Note: day 19 is not a complete day.  © Copyright remains with the author; all rights reserved, 2021.

Magma Plumbing under Cumbre Vieja

We’ve Googled around to see what’s likely to be going on at these depths.  The 1585, 1949 and 1971 eruptions may shed some light on this.  Researchers have found that the erupted lavas are formed by fractional crystallisation and stored in the upper mantle; during ascent, these lavas stall in the lower crust or near the Moho; there are no long-lived shallow magma reservoirs.  

Fractional crystallisation is an indicator of the depths at which magma stalls in reservoirs.  Earthquakes tend to occur  around magma reservoirs or during the ascent of magma in response to the stresses on rock that changes in magma produce. Hence our interest in them.

The 1585 eruption produced 0.03km3 of lava, which was composed of basanites, tephrites, tephriphonolites and phonolite.  The eruption is famous for the extrusion of phonolitic spines, named “Devil’s horns” by eye-witnesses, at the start of the eruption.  Examination of the 1585 lavas indicate that the more evolved lavas were the result of fractional crystallisation.  Magma differentiated at three levels: in the deeper mantle, c.20km depth, basanite evolved to tephrite 1550 to 1750 years, collecting in more than one reservoir, before the eruption;  basanite also stagnated at the base of the crust, c.14km depth, to differentiate to tephrite; and, differentiation also occurred in the edifice.  Further evolution of to tephriphonolite / phonolite may have occurred in the lower crust and upper crust. The basanite erupted may have originated from a different batch of magma than the erupted tephrite.  14km is the depth of the Moho under La Palma.

The 1949 eruption started on 24 June 1949 and ended on 30 July 1949. It had been preceded by weak seismic activity from 1936.  Seismic activity picked up in February 1949, being felt mostly at the southern tip of the island and accompanied by ground cracking.  Stronger seismicity and ground cracking immediately preceded the opening of the first vent. The primary melt was sourced at depths between 80-100km.  Fractional crystallisation occurred at 20 to 26km with some possibly at 26-36km. Magma was stored temporarily in the crust before eruption. Magma mixing occurred in the mantle three months prior to eruption, causing a dike to propagate southwards. A 3km long fissure eruption started with the Duraznero crater emitting tephrite for 14 days.  This was followed by the Llano Blanco crater opening to erupt tephrite for three days, followed by basanite for three days.  The Hoyo Negra crater opened 4 days later to erupt basanite, tephrite and phonotephrite, during which the Llano Blanco crater continued to erupt basanite. The Duraznero crater then erupted basanite.  The eruption started on 24 June 1949 and ended on 30 July 1949. The primary melt was sourced at depths between 80-100km.  Fractional crystallisation occurred at 15 to 26km with some possibly at 36km. Magma mixing occurred in the mantle three months prior to eruption, causing a dike to propagate southwards. Magma was stored temporarily in the crust between 7-14km before eruption.  Later calculations put the depth of fractional crystallisation at 35-45km.

In 1971 Cumbre Vieja erupted again, this time at Teneguía, emitting 135,000 m2 of lava and created a 290,000 m2 lava platform – 40 million m3 of lava in total.  This eruption produced basanitic to phonolitic lavas.  The eruption was Strombolian and in two phases: initially a 300m fissure opened on 26th October 1971, producing effusive lava flows from vents; and, new vents opened on 8th November 1971, with rhythmic explosions, lapilli, scoria and lava bombs.  CO and CO2 were emitted; these gases were thought to be the cause of death for the eruptions two fatalities.   Examination of the lavas showed that magma stalled at two depths:  clinopyroxene and plagioclase crystallised at depths of 20-45km; and the crystallisation of aluminium augite indicated that magma then ascended to 20-35km.  Variations in the samples tested indicates that magma formed in batches over a range of depths in the lithospheric mantle to combine before ascent.

Taburíente, Cumbre Nueva and Bejenado each have zones of clinopyroxene crystallisation between 25-45km.  Earlier Cumbre Vieja eruptions had shallower zones of 15-30km, before the deeper zones of the 1949 and 1971 eruptions (35-45km and 25-45km, resp.).  In the earlier Cumbre Vieja eruptions magma stalled beneath the Moho and the in the later eruptions magmas depths were more in line with Taburíente, Cumbre Nueva and Bejenado.

How does this Compare to the Current Earthquakes?

To make any conclusions we need to wait until there is a detailed analysis of the erupted lavas. However, we can note that the current earthquakes are at two distinct depth ranges:  7 -16km and 30 to 42km, with not much in between.  7-16km correlates to a possible zone of magma storage beneath the crust and magma migration through the crust.  30 to 42km correlates to part of the lower zone of fractional crystallisation of the 1949 and 1971 magmas. 

Time will tell how this eruption will pan out.  In the meantime, the eruption is still going strong.  Our thoughts continue to be with those affected.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021

Sources and Further Reading:

Raw earthquake data: Instituto Geográfico Nacional (ign.es)

Kursten Galipp, Andreas Klügel, Thor Hansteen, “Changing depths of magma fractionation and stagnation during the evolution of an oceanic island volcano: La Palma (Canary Islands)”, Journal of Volcanology and Geothermal Research Volume 155, Issues 3–4, 15 July 2006, Pages 285-306. Link: Source

T. S. Johansen F. Hauff K. Hoernle , A. Klügel, T.F. Kokfelt, “Basanite to phonolite differentiation within 1550–1750 yr: U-Th-Ra isotopic evidence from the A.D. 1585 eruption on La Palma, Canary Islands”, Geology; November 2005; v. 33; no. 11; p. 897–900. Link: Source

Andreas Klügel , Kaj A. Hoernle, Hans-Ulrich Schminck , James D. L. White, “The chemically zoned 1949 eruption on La Palma (Canary Islands): Petrologic evolution and magma supply dynamics of a rift zone eruption”,  Journal of Geophysical Research, Vol 105, No. B3, Pages 5997-6016. Link: Source

Abigail K. Barker, Valentin R. Troll, Juan Carlos Carracedo, Peter A. Nicholls, “The magma plumbing system for the 1971 Teneguía eruption on La Palma, Canary Islands”, Contributions to Mineralogy and Petrology 170, Article number: 54 (2015).  Link: Source

Tagoro, the 2011-2012 Submarine Eruption of El Hierro

Good Afternoon!

The eruption at La Palma is continuing unabated, sadly with more evacuations for areas in the path of the lava. 

Let’s take a moment to look at her fellow island, El Hierro.  La Palma and El Hierro occupy the same N-S line at the western end of the Canary Island archipelago: La Palma to the north and El Hierro to the south.  El Hierro experienced a N-S aligned fissure eruption between October 2011 and March 2012.

Fig 1: La Restinga as seen from the harbour wall.  Image captured from Google Maps, 2021.

Background

El Hierro is a shield volcanic island which formed around 1.2 million years ago. It is made up of three volcanoes, Tiñor, El Golfo, and, later rift volcanism.

The island has a population of c. 10,000.  The capital is Valverde, located near the eastern end of the island. The earliest known inhabitants were the Bimbaches, thought to be descendants of the Guanches who had migrated from Tenerife.  Sadly, many of the Bimbaches were sold as slaves by the son of the first Spanish conquistador.  The island was then populated by both the Spanish and Normans.  Some the slaves were later returned to the island having won their freedom.

The island’s climate is influenced by the Trade Winds.  Warm moist air is deposited on the northern side of the island.  The climate varies from  warm-summer Mediterranean climate in the centre of the island, to mild semi-arid and to a tropical mild, desert climate on the coasts.

The island, home to endemic species such as the endangered El Hierro giant lizard, has been designated as a  Biosphere by UNESCO to preserve its natural and cultural diversity.

Fig 2:  The island of El Hierro.  Image captured from Google Maps, 2021. El Golfo, El Julan, Las Playas and Tiñor added by the author.  The embayment of El Golfo can be seen as the cliffs encircling La Frontera.

Tiñor was the first subaerial volcano to emerge, comprising primitive basalts to trachybasalts and tephrites. It is dated between 1.2 – 0.88 million years old, having developed rapidly in the Lower and Middle Pleistocene.  It has three units: the lowest unit with steep sides and thin steep-dipping lava flows; a middle unit of thicker lavas; and, an uppermost unit, the Ventejis Group, with craters  After the emergence of the Ventejis Group, the north western flank of Tiñor suffered a large gravitational collapse which may have taken out more than half of the Tiñor edifice.

The El Golfo volcano emerged c. 545,000 years ago, located near the current town of Frontera.   This volcano has two identifiable layers:  a lower unit made up of basalt Strombolian and Surtseyan pyroclasts with dykes implying the presence a triple rift system; and, the upper unit made of lava flows, overlain with trachybasalts and trachyte lava flows and block-ash deposits.   The youngest lavas are the trachyte, aged at c. 176,000 years.  Gravitational collapse of the southwestern flank of the volcano occurred at El Julan.

The San Andrés fault system on the north east rift developed between 545,000 -176,000 years ago.  The presence of cataclasites and pseudotachylytes, rocks typically found in the early stages of volcanic collapse indicate that there was incipient gravitational collapse that did not develop further.  Cataclasites are formed through faulting or fracturing in the upper crust.  Pseudotachylytes may be formed by frictional melting of the wall rocks during rapid fault movement during an earthquake.

The impressive El Golfo embayment resulted from gravitational collapse of the El Golfo volcano.  This may have occurred in a single or multiple events.  One possible is scenarios is that an initial subaerial lateral collapse of the volcanic edifice occurred 130,000 years ago and a second one occurred 17,000 – 9,000 years ago affecting the submarine lava platform.

Rift volcanism, defined as when the three arms of the rift were active at the same time without a central vent, occurs along the three arms of the island, with vents occur along the ridges of the rifts. Before the 2011-2012 eruption, rift volcanism had been dated to between 134,000 years ago to 500BC.  GVP lists 6 eruptions prior to the 2011-2012 eruption: 3 confirmed in 550BC, 950BC and 4790 BC; and, 3 unconfirmed in 1793, 1692 and 1677. The associated lavas are  alkaline picro-basalts, basanites and tephrites.

2011 -2012 Submarine Eruption

Fig 3:   Stain from the submarine eruption south of the island.  Image cropped from NASA Earth Observatory EOSDIS on 10 February 2012.  Source: El Hierro Submarine Eruption (nasa.gov). “El Julan” and the “Eruptive vent” added by the autho

In 2011 a submarine flank eruption commenced, preceded by an intense seismic swarm.  The submarine cone has been named Tagoro, from the Guanche language for meeting place or circular enclosure of stones.

Build up to the eruption

Before the eruption, El Hierro had been quiet since a seismic episode in 1793, which may or may not have been connected to an eruption.  In the absence of eye-witness accounts then, it has been suggested that there was an eruption of Lomo Negro volcano, a submarine eruption or a magma intrusion.

Fig 4:  Crater of Tanganasoga. Image cropped from one by Areuland, 5th January 2017. published under CC BY-SA 4.0. Source: Wikipedia

In July 2011, a seismic swarm started under El Golfo at a depth of 20-25km.  Seismicity then ascended to 11±3km and headed southward across the island, after which it ascended to 3km between 8-9 October prior to the eruption on 10 October 2011.  A 4.4M earthquake at a depth of 10km 1.5km south of La Restinga preceded the eruption.  Magma had risen under Tanganasoga, the main volcano on El Hierro, to migrate south towards La Restinga.

Basanite fractionation and magma replenishment may have occurred during these seismic swarms while magma was being injected into the lower crust.

The eruption

The eruption occurred in phases.  The lavas in the first phase were evolved basanites.  The second phase was more primitive lava with 8-9 wt% MgO.  

A harmonic tremor started on 10 October 2011 between 04:15 and 04:20 and is thought to indicate the start of the eruption.  Magma had risen from the base of the ocean crust to the vent in c. 30 hours.  Areas of discoloured, sulphurous-smelling water and dead fish were seen off the coast of La Restinga. Vigorous bubbling in the sea resembling a jacuzzi was observed above the vent, caused by gas emissions and heat from the vent; bubbling reached several metres high on occasion.

On 15 October 2011, lava bombs were observed.  These comprised white to grey pumice encased in black basanite lava.  Basanites are typical of the western Canary Islands. A small amount of U-depleted rhyolite was found in the lava bombs, though to have originated from differentiated trachyte incorporating quartz-rich sediment during melting when mobilised by the basanite. The boundary between old oceanic crust, continental crust and volcanic island may act as a magma trap where sediments can be assimilated.  A few days later basanite lava balloons were emitted.

Fig 5 :  Simplified drawing  of magma migration by the author (not to scale) during the early phase of the eruption by the author, modified from one found in the Bulletin Report, March 2012 (BGVN 37.03), Global Volcanism Program | Hierro (si.edu).  The white arrows and column denote the path of the magma; Vs, volcanic sediments; and, Mm, magma mixing –where it is thought that the white pumice and black basanite lava bombs were created. © Copyright remains with the author; all rights reserved, 2021.

The second phase of the eruption started in November 2011 with seismicity at depths of 10-15km and a decrease in tremor intensity.  This correlated with the eruption of more primitive lavas.

During November 2011, the eruption was confirmed as Surtseyan.  Several plumes of material aligned N-S were visible from the air, confirming a fissure eruption. Tanganasoga experienced rapid inflation and released CO2. On 24th November a sulphur smell was reported in El Golfo.  On 4th December 2011, vigorous phreatic bubbling (“the jacuzzi”) was observed.  In December 2011, there was a temporary lull: the harmonic tremor and seismicity decreased.

The eruption picked up again in January 2012 with increased seismicity, a larger area of eruption and pumice clasts.  In late February 2012, seismic activity, deformation and gas emissions decreased.  The eruption was declared over in March 2012.

Tagoro’s cone was found to be 85m below sea level in April 2012. The eruption has been classified as a VEI 2.

Post eruption

Magma movements were detected from seismic swarms.  In June 2012,accompanied by rapid inflation, magma moved south-westward towards El Julan-La Dehesa, northwest of the submarine vent.  Earthquakes picked up again in September 2012 indicating magma movement under Tanganasoga.   

The last reported seismicity was in March 2013 when another swarm occurred near the NW tip of the island, initially at 20km depth, migrating westward at a depth of 12-15km.  The swarm was accompanied by inflation and CO2 emissions.

Plotting Seismicity

We have downloaded the earthquake data from IGN’s publicly available database and plotted the earthquake swarms for the period July 2011 to December 2012.   The results are shown in the video below.

Fig 6:  Earthquake numbers vs time for the period July 2011 to December 2012at El Hierro by the author, showing the five swarms seen in the video below.  © Copyright remains with the author; all rights reserved, 2021.
Fig 7: Video by the author of the first five earthquake swarms associated with the 2011 to 2012 eruption of El Hierro. © Copyright remains with the author; all rights reserved, 2021.

Only time, and a lot of work by the various scientists studying the eruption on La Palma, will tell how many similarities are shared between the two eruptions.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources & Further Reading

“Classical Geology in Europe 4: Canary Islands”, Juan Carlos Carracedo, Simon Day, Terra Publishing, 2011 (reprint).

The Smithsonian Institution’s Global Volcanism Program: Global Volcanism Program | La Palma (si.edu)

Instituto Geografíco Nacional: Instituto Geográfico Nacional (ign.es) (link for La Palma)

El Hierro: Wikipedia

Updates on Activity at Fagradalsfjall, Cumbre Vieja, and Askja as of October 2021

We are no longer updating this post; future updates will be included in new posts.

Update 2 12.10.2021: Plots of the Earthquake Swarm SSW of Mount Kelir, 27/09/2021 to Date

Fig 16: Mount Kelir, cropped from an image by Michal Klajban, published under CC BY-SA 4.0.  Source: Wikimedia Commons

Mount Kelir is at the northern end of the earthquake swarm which started on 22 February 2021. In that swarm, earthquakes started near Mount Kelir and migrated towards and beyond Fagradalsfjall prior to the eruption at Geldingadalir on 19 March 2021.

The current swarm which started on 27 September 2021 near Mount Kelir is ongoing at the time of writing.  Over 10,000 earthquakes have been recorded, of which IMO have confirmed c. 1,245.  It is thought that an eruption may ensue near Mount Kelir.

We have plotted the earthquakes and made a video of the geoscatter and scatter plots.

Fig 17:  Analysis of the swarm by depth and magnitude by the author.  © Copyright remains with the author; all rights reserved, 2021.
Fig 18:  Video of geoscatter plots and scatter plots of the current swarm by the author.  © Copyright remains with the author; all rights reserved, 2021.

Whether or not a new eruptive site emerges, magma migrates to the existing site at Fagradalsfjall, or, it all quietens down, only time will tell.  At the moment the swarm is migrating SSW. 

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Source for raw earthquake data:  Icelandic Met Office: IMO

12.10.2021 1: Update on La Palma Seismicity

Good Morning!

Let’s take look at status of the eruption and seismicity at La Palma.

The eruption is still going strong.  The cone has grown substantially, despite partial collapses.

Fig 11: Cone growth.  On the left, the new cone on 20 September, 2021, cropped from an image by Eduardo Robaina, published under CC BY-SA 3.0; on the right, screen shot earlier today from RTVC

The following was reported earlier today:

  • The lava reached the cement works, Callejón de la Gata, today.  Local residents were confined to their homes due to the risk of toxic fumes from burning chemicals.
  • A  large volume of lava was emitted after the wall of the lava lake [cone?] was destroyed.
  • The northern arm of the lava flow is now 300 metres from the sea and expected to make a new lava delta near the beach of Perdido.
  • 591.1 hectares have been affected by lava.  This includes 132 hectares of crops , of which 70 hectares were banana crops; 33 hectares vineyards; and, 8 hectares avocado crops.
  • The maximum width of the lava flow is 1,520 metres.
  • 1,281 buildings have been impacted, of which 1,186 have been destroyed.
  • The lava delta is now 34 hectares.
  • Seismicity remains high.  To  date, over 35,000 earthquakes have been recorded.  The most recent earthquakes remain below 10km, with depths reaching more than 20km.

The high level of seismicity is thought to indicate rising magma because there have been spasmodic tremors and a strong volcanic tremor at 18 Hz; the latter may be from depressurisation of magma at a depth of c. 10km.  In the absence of increased ground deformation, it is not known when or how magma may reach the surface.  If it reaches the surface, it may follow the current conduit or emerge at new fissures.

Fig 12:  Amplitude of seismic signal, source: IGN.  Green line denotes onset of the eruption.
Fig 13:  Seismic signal, source: IGN

We have updated our earthquake data and have plotted the swarm from 27 September 2021to present.  The results are shown in the video below.

Fig 14: Analysis of the earthquake swarm from 11 September 2021 to present by the author.  © Copyright remains with the author; all rights reserved, 2021.
Fig 15: Video showing geoscatter plots and scatter plots by the author of the swarm from 27/09/2021 to present

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources:

El Mundo: www.elmundo.es

VolcanoDiscovery:  www.volcanodiscovery.com

IGN: www.ign.es

04.10.2021: Update Fagradalsfjall Seismic Swarm near Kelir

The swarm near Mount Kelir is ongoing.  IMO report that 6.200 earthquakes have occurred in the swarm, although c.624 have been confirmed at the time of writing (Sources:  IMO_Earthquakes and  Skjálfta-Lísa (vedur.is)).

Fig 8: Geoscatter plot of the current swarm SSW Mount Kelir by the author. Colour denotes time (using earthquake number), red is the oldest and yellow the youngest.  © Copyright remains with the author; all rights reserved, 2021

We have analysed and plotted the swarm.  It would appear that the swarm is ascending but still in the crust. The largest earthquake with a magnitude of 4.16 had a depth of 5.669 km. 

Fig 9: Numerical analysis of the swarm by the author.  © Copyright remains with the author; all rights reserved, 2021.

The possible ascent of the swarm is more visible in the scatter plot looking at it in an easterly direction.

Fig 10: Scatter plot of the swarm by the author.  Colour denotes time (using earthquake number), red is the oldest and yellow the youngest. © Copyright remains with the author; all rights reserved, 2021.

04.10. 2021: Update on the Cumbre Vieja Eruption

Fig 6: Plot of earthquakes from 11/09/2021 to 04/10/2021 10:13:11 by the author.   © Copyright remains with the author; all rights reserved, 2021
  • Part of the main cone collapsed at c. 9:10 pm last night; some vents have now merged.
  • Effusive activity has increased.  Lava flows have merged; the flow is 1km wide at its widest point.
  • The lava delta is now 29.7 hectares.  This has impacted the surfing beach at Los Guirres.
  • 400 hectares of land has been covered by lava and 4,819 hectares covered by ash.  1,047 buildings have been damaged, including 947 destroyed.
  • 20% of the banana crop has been lost. The village  of La Bombilla, built for banana plantation workers, is now under threat.
  • The seismic swarm is ongoing, with most recent earthquakes between 7km  – 14km depth.

We have updated our earthquake plots for the most recent swarm (11/09/2021 to 04/10/2021 14:30:59).  The swarm reactivated on Day 17.

Fig 7: Earthquake  plots by the author for the swarm 11/09/2021 to present. © Copyright remains with the author; all rights reserved, 2021

Sources for updates as before: El Mundo and IGN.

01.10.2021 (original post)

Good Morning! Today we provide an update on Fagradalsfjall, Cumbre Vieja (with video of earthquake swarms) and Askja.

Fagradalsfjall, Iceland

Fig 1: Mount Kelir, cropped from an image by Michal Klajban, published under CC BY-SA 4.0.  Source: Wikimedia Commons

Fagradalsfjall celebrated the six-month anniversary of the start of the eruption, which occurred on 19 March 2021, by taking a break.  Low level activity has been observed since 18 September 2021.

An earthquake swarm stared on 27 September 2021 south of Mount Kelir.  This is located near the northern end of the earthquake swarms earlier this year which preceded the eruption at Geldingadalir.

We have plotted the swarm to see what is going on.

Fig 2a: Plots by the author of the earthquake swarm from 27/09/2021 to present. Geodensity plot on the left and geoscatter plot on the right.  The colour code in the geoscatter plot is time: red is the oldest, yellow the newest. Time is approximated by earthquake sequence.  © Copyright remains with the author; all rights reserved, 2021.
Fig 2b: Plots by the author of the earthquake swarm from 27/09/2021 to present. Scatter depth v longitude plot on the left and scatter depth v latitude plot on the right.  The colour code is time: red is the oldest, yellow the newest. Time is approximated by earthquake sequence.  © Copyright remains with the author; all rights reserved, 2021.

While it is not clear what the cause of the swarm is (new magma or the crust adjusting to changes in tension), people are advised to avoid the area for the time being.  If an eruption does occur near Kelir, it is expected to be similar to that at Fagradalsfjall.   The aviation code is still orange.

Cumbre Vieja, Canary Islands

Fig 3: Cumbre Vieja eruption on 20/09/2021, cropped from an image by Eduardo Robaina, published under CC BY-SA 3.0.  Source: Wikimedia Commons

The eruption is still going strong.  The vents have produced ash columns, jetting lava and effusive lava flows.

Lava reached the sea, following the opening of a new vent earlier this week, which emitted more effusive lava. The lava travelled at 300 m/hr, crossing the coastal road and cascading over 100m high cliffs at Los Guirres. The lava is forming a delta, which has reached an impressive size 21 hectares. 

There are now four eruptive vents: a new effusive vent opened 400m north of the main vent on Thursday; and, two more opened on Friday 15 metres apart and 600m north west of the main cone.  Lava from Thursday’s new vent also made it to the sea via a flow parallel to the original one.  A fumarolic field has developed on the north side of the main vent.

Over 80 million cubic metres of lava have been erupted.  Sadly, this has damaged 1,005 buildings, of which 870 have been destroyed.  30.2km of road has been impacted, of which 27.7km have been destroyed.  Ash now covers 3,172.9 hectares of land.

SO2 levels are higher but not considered a risk for the population at the moment.

Earthquakes are occurring near the area start of the swarm which preceded the eruption.  They are deeper than the earlier swarm leading to concern that lava may be fed from a deeper reservoir.   We have plotted the current swarm and previous swarms from 2017 to date. 

Fig 4: Plots by the author of the most recent earthquake activity at Cumbre Vieja.  For plotting purposes, the activity has been labelled as a new swarm, which started on 27 September 2021. Green circles are the current swarm earthquakes < 3.0M; red stars are current swarm earthquakes ≥3.0M; grey circles are earthquakes < 3.0M from 2017 to 26.09.2021; and cyan stars are earthquakes ≥3.0M from 2017 to 26.09.2019 (all are in fact from the previous swarm starting 11 September 2021).  © Copyright remains with the author; all rights reserved, 2021.

We have compiled a video of the earthquake swarms from 2017 to present.

Fig 5: Video by the author showing the progress of the earthquake swarms from 2017 to present. © Copyright remains with the author; all rights reserved, 2021.

Askja

Seismicity is still occurring.  The Icelandic authorities are continuing to monitor this.  The aviation code is still yellow. 

We have not had time to update our earthquake plots, but will do so in due course.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021

Sources:

Plots are the authors own work.

Information and raw earthquake data:

Fagradalsfjall: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is)

Cumbre Vieja: Instituto Geográfico Nacional (ign.es) & EL MUNDO – Diario online líder de información en español

La Palma, Canary Islands, Spain, Eruption Commenced 19 September 2021 (updated to 27.09.2021)

Good Morning!

This post has been updated as the eruption progresses. New updates will be provided in new posts.

Fig 6:  Image cropped from a photo by Eduardo Robaino, published under CC BY-SA 3.0.  Source: File:LUN 8401.jpg – Wikimedia Commons

Our thoughts are with those impacted by the eruption. While no lives have been lost, the economic damage and personal impact could be huge.

The official source for updates is IGN. You can find them on Twitter at IGN-CNIG @IGNSpain.

Update 27.09.2021

Fig 10:  The volcano taking a short break this morning, looking deceptively tranquil. The main cone is in the centre of the image.  Source: screen shot from TV Canarias: www.youtube.com
  • The eruption is now in its ninth day. The volcano took a break for a couple of hours today, to resume with a thick ash column and a few explosions.  The new seismic swarm today may indicate that the volcano is recharging.  It would be unusual for an eruption here to be so short.
Fig 11:   Earthquake swarm 27.09.2021.  Green circles are today’s earthquakes < 3.0M; red stars are today’s earthquakes ≥3.0M; grey circles are earthquakes < 3.0M from 2017 to 26.09.2021; and cyan stars are earthquakes ≥3.0M from 2017 to 26.09.2019 (all cyan stars are in fact from the previous swarm starting 11 September 2021).  © Copyright remains with the author; all rights reserved, 2021.
  • The airport was closed for a period over the weekend while ash was cleared.
  • The cone broke in its southern section releasing a new lava which flowed over the older flow.  The new lava reached speeds of 250 – 300 metres per second. Sadly, the church and other buildings in Todoque were razed.
  • Lava may now reach the sea. It is now between 800m and 1,000m from the sea, reaching the outskirts of Tazacorte. People in San Borondón, Marina Alta, Marina Baja and La Condesa are confined to their homes with their doors and windows closed due to the risk of ash and gases. We can only imagine the stress they are under right now.
  • There have been up to 4 eruptive centres and two lava flows.  New emission points emerged in the NE section of the cone; they have since merged. 
  • On 26 September 2021, the lava covered an area of 2.62 km2, with an average thickness of 12.1 metres  a maximum thickness of 50 metres and a volume of 31 million cubic metres.  The latest estimate of damage at the time of writing is that over 500 homes and 237.5 hectares of land are now covered by lava.  18.9 km of roads have been destroyed. 1,507 hectares of land are covered by ash.
  • The Ramón Margalef is to carry out a survey of the sea floor to check for submarine emissions.
Fig 12: Drop in seismic signal and subsequent resumption.  Source: National Geographic Institute (ign.es)

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources as below.

24.09.2021

  • The explosive phase, combined with the opening of new vents on the south west of the cone, has led to the evacuation of Tajuya, Tacande de Arriba and Tacande de Abaja.
  • The total number of evacuated is now 6,200.
  • Large pyroclastic materials are being ejected, and highly fluid lava with speeds of 60-80m/s is being discharged from the new vents.
  • There are fears that the main cone may collapse as a result of new vents and more explosions.  This would lead to high-speed pyroclastic flows.  You cannot outrun a pyroclastic flow.
  • The eruption column reaches 6km above sea level.
  • Although airspace is still open, Iberia, CanaryFly and Binter have suspended flights to / from La Palma, and Vueling has cancelled its Saturday flight from Barcelona to La Palma.
  • The Roque de los Muchachos Observatory has closed its telescopes to protect the mirrors from ash; it is still monitoring the gas and ash clouds from the volcano.
  • Lava covers 190 hectares; 420 buildings and 15.2 km of roads have been lost.
  • The area impacted by the volcano to be formally been declared a disaster zone.
  • It is thought that the older lava flows are slow due to the gradients they are on; they may speed up if they hit a higher gradient.
Fig 8: Increasing amplitude of the tremor, reflecting the more explosive phase.  Source for image: Instituto Geográfico Nacional (ign.es)
Fig 9: Seismogram and spectrogram reflecting the increased explosive activity.  Source: Instituto Geográfico Nacional (ign.es)

Sources for the update: as before.  A live webcam operated by TelevisionCanaria can be found here: DIRECTO | Erupción del volcán en La Palma – YouTube

23.09.2021

  • The eruptive style has changed from effusive to more explosive: of the two lava flows, the northern flow has nearly stopped and the southern is c.2,100 metres from the sea, advancing at 4 metres per hour having fanned out.  It is now thought that it is unlikely that lava will reach the sea.  IGN have reported several large explosions.
  • The aviation code for La Palma has been raised from orange to red, due to gas and ash.  Airspace remains open except for two restricted areas. Airlines are advised to get flight plans checked before planes depart.
  • 2 more fissures have opened since our previous update.
  • Ground uplift is now c. 24cm.
  • 26 million cubic metres of lava have been emitted, razing 220 hectares of land and covering 180.1 hectares. The northern flow is 12m thick at the front and the southern flow, 10m thick.
  • 390 properties and 14km of roads have been destroyed.
  • Banana harvesting has been suspended in the area to allow people to collect their belongings.
  • Farmers in restricted areas require permission from PEVOLCA to irrigate their crops.
  • More than 6,000 people have been evacuated to date.
  • The Official College of Psychology of Santa Cruz de Tenerife has reminded us that those losing property to the eruption are suffering trauma; they are not helped by seeing images of this repeated multiple times on social media.

Sources: El Mundo (link below) & IGN-CNIG (link above)

We have updated our earthquake plots for the current swarm.  We have put them together in a short video.

Fig 7: Video by the author of geoscatter plots and scatter plots of the earthquake swarm from 11/09/2021 to 22/09/2021. © Copyright remains with the author; all rights reserved, 2021.

21.09.2021

  • Air traffic is not affected; the airport remains open.  Visitors are encouraged to the island.
  • 166 homes have been confirmed as lost.  More than 6,000 have now been evacuated.
  • Land covered by lava will not be cultivatable; to date, 103 hectares of land are covered. Contaminated soil may take 20 years or more to be usable. Loss of land is expected to cause considerable poverty.
  • Lava is approaching the Todoque in Los Llanos de Aridane.
  • Several roads are closed in the vicinity of the eruption: LP-211, LP-212, LP-213, LP-215 and LP-2.
  • At the time of writing lava has not been reported as reaching the sea.  When it does, clouds of toxic and acid vapours, including chlorine, sulphur, carbon and hydrogen sulphides, hydrochloric acid, carbonic acid and CO2, will be released, forcing further evacuations.
  • SO2 emissions reached between 7,997 – 10,665 tons per day on the second day.  SO2 emissions have reached the cost of Africa.
  • It is too early to say how long the eruption will last.  The 1971 Teneguía eruption lasted 24 days and the 1949 Cumbre Vieja eruption lasted 33 days.

20.09.2021

  • No lives have been lost or injuries reported.
  •  The airport remains open.  Air traffic is not currently affected.
  • 2 fissures had opened 200m apart, with 8 vents.
  • The temperature of the lava is over 1,000°C (last reported: 1,113°C).
  • The ground is continuing to inflate; more earthquakes are possible.
  • The south west coast of the island is at risk of landslides and rock falls.
  • The lava discharge rate is 0.7km per hour. The lava is expected to reach the ocean at c.8:00pm (has not happened yet; the lava slowed and diverted).  When the lava reaches the ocean, toxic vapours will be released due to the chemical reactions between the hot lava and sea water; the areas impacted would be Tazacorte, near Playa Nueva, Los Guirres.
  • Between 6,000 and 9,000 tons per day of SO2 were emitted on the first day.
  • 5,500 people evacuated. 
  • A 3.8M earthquake signalled the opening of a new vent (the 10th) 900m from the main vent. The new stream of lava led to the evacuation of Tacando.

Sources for the updates: El Mundo (https://www.elmundo.es) and AS (https://.en.as.com).

19.09.2021 (original post)

An earthquake swarm which started on 11 September 2021, accompanied by uplift, resulted in PEVOLCA raising the alert level for La Palma to yellow on 13 September 2021. 

The eruption, itself, started on 19 September 2021 at 2:15pm (UTC) in Cabeza de Vaca, El Paso; the alert level is now red.  c.5,000 people have been evacuated.  To date, no lives have been reported as lost, property damage is yet to be assessed. Our thoughts are with those affected.

Fig 1a: Seismographs and spectrogram showing the onset of the eruption.  Source: Instituto Geográfico Nacional (ign.es)
Fig 1b: Displacement and ground deformation measured pre-eruption. On the left, displacement is for the period 10/09/2021 and on the right, deformation is for the period June 2021 to September 2021 (to date). Source: IGN (link below).

At the time of writing, there are lava fountains and a large lava flow that is threatening people’s homes.

There are many videos on YouTube.  Here are live streams via Reuters: LIVE: Volcano erupts on La Palma in the Canary Islands – YouTube ; and, SixtyMedia: Erupción volcánica en La Palma – YouTube

La Palma

Fig 2: La Palma. Source: Google Earth

La Palma is a volcanic island with an area of 708 km2, located at the northwest end of the Canary Island archipelago above the Canary Island hotspot.  The population of the island is c85,840; 15,720 live in the capital Santa Cruz de la Palma and 20,470 in Los Llanos de Aridane. The climate is tropical semi-arid. Its economy relies on agriculture and tourism; banana cultivation is centred in the valley of Los Llanos de Aridane; and, other crops include oranges, avocados and grapes. Fishermen operate from Tazacorte, Puerto Naos and Santa Cruz de la Palma. The island has abundant flora and fauna.

The island is comprised of many volcanoes, including an extinct Pliocene – Pleistocene northern shield volcano and the active Pleistocene – Holocene Cumbre Vieja. Cumber Vieja is the most active volcano in the Canary Islands, last erupting in 1971.

The northern shield lavas comprise basanites, alkali basalts, tephrites, phonolites and trachytes, reflecting magma evolution during the shield-building stage.  The younger Cumbre Vieja volcano has more basaltic lavas.

Fig 3: Caldera de Taburiente, Bejenado and Cumbre Vieja.  Source:  Google Earth

Building the Island

The island emerged in five stages: the initial submarine-building of a seamount, followed by the creation of four volcanoes during the shield-building stage, as shown below.

Time scaleVolcanoLavas
PlioceneSea-mountBasalt, trachybasalt, phonolite, trachyte
1.7Ma -1.2MaGarafíaBasalt
1.2Ma – 0.4MaTaburienteBasalt, tephrite, phonolite
0.56-0.49kaBejenadoBasalt, tephrite, phonolite
125ka-presentCumbre ViejaBasalt, basanite, trachyte, phonolite

Garafía is covered by the later Taburiente volcano; its rocks being visible only in a few outcrops.  Around 1.2Ma gravitational collapse of its southern flank left debris avalanche deposits in the sea.

Activity at Taburiente volcano commenced without a break following the collapse at Garafía.  Its growth included the development of triple rift zones – parallel swarms of dikes at c 120° angles, indicative of magma doming.  Activity then migrated southwards.

A landslide, clearly visible on maps, occurred between the building of Taburiente and Bejenado, and was responsible for the creation of the Caldera de Taburiente.  Bejendo volcano is a small volcano that emerged to fill the collapse embayment.  Subsequent erosion enlarged the caldera.

Cumbre Vieja emerged after activity had ceased in the north.  From c. 125,000 years ago, volcanic activity built the north-south ridge until 80,000 – 20,000 years ago when activity declined.  From 20,000 – 8,000 years ago activity picked up again, focusing on the north-south rift and also north-west and north-east rifts. Activity now focuses on the north-south rift.  There is concern that another flank collapse could occur following the emergence of west facing normal faults during the 1949 eruption. 

Eruptive History

GVP records 13 Holocene eruptions for La Palma, seven of which were VEI 2s, with mild explosive activity and lava flows that caused property damage (the remaining 6 have not been assigned a VEI number).   Eruptions during the last 7,000 years have formed cinder cones and craters along the north – south axis of Cumber Vieja.  Lava flows reached the sea in 1585, 1646, 1677-78, 1712, 1949, and 1971; a large lava field emplaced during the 1677-78 eruption covers the southern tip of the island. 

GVP lists the lava types as Trachybasalt / Tephrite Basanite, Phono-tephrite / Tephri-phonolite, Phonolite, Basalt / Picro-Basalt, Trachyte / Trachydacite.

Seismic Activity

The current swarm was preceded by others: one in 2017, one in 2018, five in 2020, and three in 2021. The earthquakes in the previous swarms were deeper, between 20 and 30 km, and were less intense than the current swarm.

We have downloaded the earthquake data from IGN for 2021 to 19.09.2021 11:09 to see what has been going on.  While these are only the earthquakes that have been located (there are thousands that have not), the plots clearly indicate magma ascent. 

We do not have a precise location for the vents of the current eruption so are unable to compare it to the earthquake plots.

Fig 4: Geodensity plot and a latitude v depth (slightly rotated round) by the author of earthquakes occurring on La Palma from 1.01.2021 to 19.09.2021 11:09 by the author.  Colour in the right plot is indicative of age (red oldest, yellow newest). The current swarm started around earthquake 1051. © Copyright remains with the author; all rights reserved, 2021.
Fig 5 : Geoscatter plot and a longitude v depth (slightly rotated round) by the author of earthquakes occurring on La Palma from 1.01.2021 to 19.09.2021 11:09 by the author.  In the left plot, yellow circles denote earthquakes ≥ 2.0M and red stars, ≥3.0M. Colour in the right plot is indicative of age (red oldest, yellow newest). The current swarm started around earthquake 1051. © Copyright remains with the author; all rights reserved, 2021.

If you wish to follow the eruption as it progresses, IGN has up to date information on the eruption at La Palma on: Instituto Geográfico Nacional (ign.es).

Further updates will be provided in new posts.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021

Sources and Further Reading:

“Classical Geology in Europe 4: Canary Islands”, Juan Carlos Carracedo, Simon Day, Terra Publishing, 2011 (reprint).

The Smithsonian Institution’s Global Volcanism Program: Global Volcanism Program | La Palma (si.edu)

Instituto Geografíco Nacional: Instituto Geográfico Nacional (ign.es) (link for La Palma)