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Professional Contributions
Hazards and Havoc:
Isaac E. Pope
ln a world dominated by quiescence, it is the erratic disruptions in the landscape that demand attention, yet few have created such unremittent surprises of late as the recent eruptions on La Palma Island. Located in the Canary Archipelago off the coast of Morocco, La Palma Island developed from the steady turmoil typical of oceanic hotspot island chains. Nonetheless, the erratic volcanic history of the archipelago seemed to suggest that eruptions are few and far between though dangerous in the extreme. Naturally, the identification of growing unrest beneath the Cumbre Vieja rift zone on La Palma’s southern limits from 2017 to 2020 led researchers to conclude it was a warning “most likely decades before a potential eruption” (Fernandez et al., 2021), yet this was merely the rising curtain before the main act. Beginning in September 2021, fissure eruptions released basaltic lavas across the countryside, continuing the intricate volcanic history of the archipelago. Even so, the eruptions on La Palma Island are but the budding expressions of a long, luxurious history of volcanism.
The Canary Archipelago: A Luxurious History
The saga of volcanism in the Canary Archipelago rests upon a backdrop stretching to the breakup of Pangea (Troll and Carracedo, 2016a). As rifting sliced through Pangea, a series of basaltic eruptions fed by the upwelling mantle produced an extensive large igneous province in Jurassic time. Since then, continued decompression melting led to the development of a hot spot which fed a series of submarine volcanoes along the rigid passive margin of the African Plate. Though speculation abounds on the exact nature of the hot spot (van den Bogaard, 2013), its effects have remained consistent in the region, as evidenced by the Canary Archipelago, yet even the obviousness of its extreme duration is perhaps a greater mystery than the hot spot itself. Indeed, the Canary Archipelago and Hawaiian Islands are, for all intents and purposes, nearly identical except in one detail: their age. The oldest Hawaiian Island still above sea level is dated at nearly 5 Ma, while the oldest island in the Canary Archipelago is dated as four times older at 20 Ma (Carracedo, 1999). The immense volume of the shield volcano gently warps the adjoining oceanic lithosphere, and the volcanic islands gradually subside and eventually become seamounts. Many oceanic island chains have ages similar to that of the Hawaiian Islands, yet it appears the curious ancientness of the Canary Archipelago may be due indirectly to the rifting of Pangea. Some geologists have proposed that the rigid passive margin of Africa may be helping to offset the subsidence of the Canary Archipelago, allowing individuals islands to remain above sea level for as
Figure 1. Located off the western coast of Morocco, the Canary Archipelago resulted from an intricate volcanic history stretching back to Jurassic time. As the westernmost and youngest member of the Canaries, La Palma Island and its various mapped volcanic centers provides a window into oceanic hotspot volcanism. Note that each historic eruption has been sourced from novel fissures, as is the case of the 2021 (not mapped) eruption along the Cumbre Vieja Rift Zone. Produced after Fernández et al. (2021).
much as four times longer than at the Hawaiian Islands (Troll and Carracedo, 2016a). Having so much of its volcanic history yet exposed above the waves has greatly aided geoscientists in deciphering the story of the Canary Archipelago.
Just off the coast of Morocco, the five islands of the Canary Archipelago have been investigated since the earliest days of geology, even receiving visits from Lyell and others. Later work on the Hawaiian Islands provided keys to solving mysteries long buried in the Canaries, yet few places have the entire life story of oceanic islands arcs so clearly presented as the Canaries themselves. Indeed, two developmental phases have been identified: the shield stage and post-erosion stage (Carracedo, 1999). In the initial shield stage, the volcano’s emergence from the sea appears to be the most disruptive. Frequent upticks in volcanism steadily builds the shield, while intermittent periods of comparative calm allows erosion to set in. The high eruptive output often oversteepens the shield, which coupled with the shield-weakening forces of erosion, causes massive sector collapses (Hunt and Jarvis, 2017; Maccaferri et al., 2017). These debris avalanches, in turn, often remove so much overburden that dikes are exposed near the surface, catalyzing another phase of increased volcanism (Thiele et al., 2020). Over time, the rejuvenating turmoil of volcanism grinds to a halt and is replaced by destructive forces during the post-erosion phase. During this time, incision is the norm and only rarely punctuated by the occasional eruption.
Though volcanism plays a key role in both phases, the resultant hazards are most pronounced during the initial shield stage. During this time, eruptions can range from effusive subalkaline flows to explosive highly differentiated silicic tephra expulsions, creating an intricate patchwork of lavas and pyroclastics of various compositions across the islands (Carracedo, 1999). Such a loose agglomeration of volcanics have contributed to repeated debris avalanches, including dozens of mapped turbidites from the youthful La Palma Island alone over the past 5 Ma (Hunt and Jarvis, 2017). Some of these deposits rank among the largest submarine sector collapses on the globe, stimulating research on their origin and potential hazards. Curiously, these collapses appear to feed a positive feedback loop, often occurring during periods of volcanism and seismic unrest to only allow more dikes to feed eruptions at the surface (Thiele et al., 2020). On the other hand, displacement of the water column could cause tremendous tsunamis reaching shores as distant as the Eastern Seaboard of the United States. Modeling by Ward and Day (2001) suggested that waves cresting at 15 m of more could reach the eastern United States, but more recent calculations suggest a more conservative value no greater than 1 m (Troll and Carracedo, 2016a). Nonetheless, the tsunamigenic potential of these events may pose hazardous to a variety of communities nearby.
Figure 2. After a week of over 20,000 earthquakes, a fissure opened along the Cumbre Vieja Rift Zone on September 19, unleashing basalt lava through the forest and into residential areas across La Palma’s southern limits. Courtesy of Eduardo Robaina under the CC BY-SA 3.0 license.
La Palma Island: A Youthful Terror Reawakens
Among the westernmost and youngest islands of the Canary Archipelago, La Palma Island is comprised of several volcanic complexes, each representing a key phase of the island’s shield stage development. Though its age is not yet well constrained, La Palma is believed to have formed perhaps as far back as 5 Ma due to turbidites extending towards the abyssal plain (Hunt and Jarvis, 2017). The island was certainly well established as a submarine volcano and finally surpassed sea level between 4 to 3 Ma and has since been superimposed by three distinct volcanic complexes in the northern region of the island (Fernandez et al., 2021). Several major sector collapses, including that of Caldera de Taburiente, have unearthed the interior of the northern volcanic complexes in cross-section, yet more recent volcanism has shifted south, building yet another volcanic complex along the Cumbre Vieja Rift Zone. Despite its age being as much a mystery as that of the island itself, the Cumbre Vieja Rift Zone has fueled six eruptions on the island in the past 500 years (Troll and Carracedo, 2016b). Of these eruptions, the most recent had been the 1971 Teneguía eruption, which was primarily a series of basalt flows restricted to the southeastern coastline of the island. Periods of volcanic unrest have intermittently punctuated the relative quiet, a better appreciation for the subsurface causes of these events would not be possible until the 2017–20 seismicity events. By studying deformation patterns and seismicity across the island, Fernandez et al. (2021) mapped potential magma pathways which suggested an impending eruption within the upcoming decades. Rather than a few decades, however, it would be only a matter of months before this suspicion would be confirmed. Beginning on September 11, 2021, a swarm of earthquakes eventually numbering over 20,000 recorded the ascension of
Infrared Signal
Cumbre Vieja
Biography
Writing from western Washington, Isaac
Pope is a sophomore undergraduate fascinated by geoscience, sharing his passion through outdoor geoscience education and publishing his research. Isaac co-chairs AEG’s Communications Committee and is the
Book Review Editor of Environmental & Engineering Geoscience.
Figure 3. Growing to the largest recorded eruption on La Palma, the 2021 eruption displaced as many as 10,000 people, extended across over 2,000 acres, and created over 70 acres of shoreline.
COURTESY OF COPERNICUS SENTINEL 2021 DATA COURTESY OF THE EUROPEAN SPACE AGENCY.
magma to the surface, culminating in an eruption on the 19th (Suarez, 2021). Fueled by a newly opened vent, the basalt overflowed into the surrounding forests on what would become a 2-km trek to the ocean. Though initially a purely effusive eruption at Volcanic Explosivity Index (VEI) 0, the eruption quickly built to a VEI 2 as other vents opened, releasing ash deposits across the island (Global Disaster Alert and Coordination System, 2021). Lava flows continue pouring from continual opening of new fissures and the eventual collapse of the dome on 25 September (Martinez and Nazca, 2021). In what has become the largest historic eruption on La Palma, the lava flow has displaced as many as 10,000 people (Suarez, 2021) while covering over 2,200 acres with fresh lava (Copernicus, 2021) and adding a further 70 acres of coast along a new lava delta (Canarian Weekly, 2021). As evidenced by satellite imagery from the Copernicus, the eruption appears to have not yet reached its climax, promising further additions to this volcanic landscape.
Conclusions
With an intricate volcanic history stretching back to Jurassic time, the Canary Archipelago has aroused both wonder and curiosity in geologists since the field’s earliest days. Due to its unique position along the rigid passive margin of Africa, the archipelago offers keys to better understanding not only the history typical of oceanic hotspots but also a live presentation of the processes and associated hazards. Indeed, the recent reawakening of the Cumbre Vieja Rift Zone on the southern region of La Palma Island provided an opportunity to comprehensively record the seismic triggers and eventual release of volcanism across the island, now peaking as the most devastating recorded eruption on La Palma. With the formation of several new fissures, lava flows have extended across over 2,000 acres and currently show no sign of slowing. As the eruption continues, opportunities abound for investigating both local and ocean-wide hazards associated with these seemingly small yet significant members of Earth’s volcanic community.
References
Canarian Weekly, 2 October 2021, The ‘New Land’ Created by the Lava from the Volcano Now Measures 27.7 Hectares” Canarian Weekly: https://www.canarianweekly.com/posts/new-land-created-by%20volcano. Accessed 26 October 2021. Carracedo, J.C., 1999. Growth, structure, instability and collapse of Canarian volcanoes and comparisons with Hawaiian volcanoes: Journal of Volcanology and Geothermal Research, v. 94, pp. 1–19, https://doi.org/10.1016/S0377-0273(99)00095-5. Copernicus, 2021, EMSR546: Volcano eruption in La Palma, Spain, Copernicus, https://emergency.copernicus.eu/mapping/list-of-components/EMSR546. Accessed 26 October 2021. Fernández, J., Escayo, J., Hu, Z., et al., 2021, Detection of volcanic unrest onset in La Palma, Canary Islands, evolution and implications: Nature Scientific Reports, v. 11, 2540, https://doi.org/10.1038/s41598-02182292-3. Global Disaster Alert and Coordination System, 2021, Overall Orange alert Volcanic eruption for La Palma, Global Disaster Alert and Coordination System, https://www.gdacs.org/report.aspx?eventtype=VO&eventid=1000031, accessed 26 October 2021. Hunt, J.E., and Jarvis, I, 2017, Prodigious submarine landslides during the inception and early growth of volcanic islands: Nature Communications, v. 8, 2061, https://doi.org/10.1038/s41467-017-02100-3. Maccaferri, F., Richter, N. and Walter, T.R., 2017, The effect of giant lateral collapses on magma pathways and the location of volcanism: Nature Communications, v. 8, 1097, https://doi.org/10.1038/s41467-017-01256-2. Martinez, G. and Nazca, J., 25 September 2021, Airport closed as La Palma volcano eruption intensifies. Reuters: https://www.reuters.com/world/europe/red-hot-lava-spews-la-palma volcano-eruption-intensifies-2021-09-25/. Suarez, B, 19 September 2021, Lava pours out of volcano on La Palma in Spain’s Canary Islands. Reuters: https://www.reuters.com/world/europe/people-evacuated-spanish-island-lapalma-after-volcano-eruption-warning-2021-09-19/. Thiele, S.T., Cruden, A.R., Micklethwaite, S. et al., 2020, Dyke apertures record stress accumulation during sustained volcanism: Nature Scientific Reports, v. 10, 17335. https://doi.org/10.1038/s41598-020-74361-w. Troll, V.R. and Carracedo, J.C., 2016a, The Canary Islands: An Introduction, in Troll, V.R., and Carracedo, J.C., eds., The Geology of the Canary Islands, Elsevier, pp. 1–41, https://doi.org/10.1016/B978-0-12-809663-5.00001-3. Troll, V.R. and Carracedo, J.C., 2016b, The Geology of La Palma, in Troll, V.R., and Carracedo, J.C., eds., The Geology of the Canary Islands, Elsevier, pp. 101–180, https://doi.org/10.1016/B978-0-12-809663-5.00001-3. van den Bogaard, P., 2013, The origin of the Canary Island Seamount Province – New ages of old seamounts: Nature Scientific Reports, v. 3, 2107. https://doi.org/10.1038/srep02107. Ward, S.N. and Day, S., 2001., Cumbre Vieja Volcano––Potential collapse and tsunami at La Palma, Canary Islands: Geophysical Research Letters, v. 28, no. 17, pp. 3397–3400, https://doi.org/10.1029/2001GL013110.
