A team led by Alberto Caracciolo of the University of Perugia examined clinopyroxene crystals erupted during the El Charco eruption of 1712, the Teneguía eruption of 1971, and the Tajogaite eruption of 2021, the destructive nine-week event that devastated parts of the island and displaced thousands of residents. Clinopyroxene is an ideal mineral archive: it crystallizes over a wide range of depths, and its slow rates of chemical diffusion preserve trace element zoning that records the temperature, pressure, and composition of the magmas through which the crystal grew. By reading these zoned crystals like tree rings, the researchers reconstructed the pre-eruptive history of each eruption in remarkable detail.

The team combined quantitative trace element mapping by laser ablation inductively coupled plasma mass spectrometry, electron microprobe analyses, clinopyroxene-based thermobarometry, and unsupervised machine learning cluster analysis. The clustering, applied to more than 316 single-spot analyses and nearly 400,000 mapped pixels, resolved six geochemically distinct populations of clinopyroxene. Two of these populations, found exclusively in resorbed crystal cores, turned out to be the smoking gun for the deep evolved reservoir: they crystallized from melts so differentiated that up to 80 to 90 percent fractional crystallization of a primitive basanite would be required to generate them, matching the degree of differentiation needed to produce phonolite from basanite beneath La Palma.

Thermobarometry told the researchers where and how hot these processes occurred. Primitive clinopyroxene cores record crystallization pressures of roughly 6 to 9 kilobars, equivalent to depths of about 22 to 32 kilometers, well below the local Moho at 10 to 14 kilometers. Evolved cores, the green, sodium-rich crystals that grew in the phonolitic mush, record the coolest temperatures in the entire dataset, between 1000 and 1025 degrees Celsius, at depths of roughly 17 to 21 kilometers. In contrast, the primitive inner rims that overgrow these cores record much hotter conditions of 1100 to 1150 degrees Celsius, the signature of fresh, mafic basanitic magma invading the reservoir from below.

The geometry of the zoning is what makes the story so compelling. In nearly every crystal examined, a chromium-rich, magnesium-rich inner rim abruptly overgrows an evolved, resorbed core, marking the moment when hot basanitic recharge disrupted the resident mush and swept its antecrysts into the ascending magma. Using measured rim thicknesses of roughly 40 to 50 micrometers and growth rates borrowed from comparable alkaline systems such as Mount Etna, the team estimated that these recharge events occurred at least four to seven days before eruption. In other words, the crystals recorded a countdown: the mush was unlocked days to weeks before magma reached the surface.

Yet the recharge was not the immediate trigger. In the early-erupted tephrites, the recharge signature is followed by a slightly more fractionated rim composition, indicating that after the mafic input the system cooled and fractionated rather than erupting immediately. The authors argue that eruption onset was more likely driven by progressive pressurization of the reservoir as volatile exsolution during continued crystallization raised the internal overpressure until the surrounding rock failed. This interpretation is consistent with independent evidence from the 2021 Tajogaite eruption, where phase equilibrium experiments and olivine zoning indicate pre-eruptive cooling of the tephritic magma.

Perhaps the most remarkable result is the temporal consistency of the system. Across eruptions separated by as much as 259 years, the same crystal populations appear, the same storage depths recur, and the same recharge-to-fractionation trends hold. The microcrystalline matrix compositions, which serve as crystal-free proxies for the carrier melts, cluster around 4.7 to 4.9 weight percent MgO in all three eruptions, and thermodynamic fractional crystallization modeling shows that the transition from basanite to tephrite within each eruption required only about 10 to 20 percent crystallization. The plumbing system beneath Cumbre Vieja, in short, has been operating in a stable configuration for centuries, with magma storage dominantly in the upper mantle and only transient stalling in the crust at depths of roughly 5 to 10 kilometers, a zone also suggested by fluid inclusion data and shallow seismicity during the 2021 eruption.

To test whether this deep-mush model applies beyond La Palma, the team compiled clinopyroxene major element data from low-flux ocean island basalt volcanoes around the world, including the Canary Islands, Cape Verde, the Azores, and the Galápagos, and projected the data into principal component space. The analysis revealed that volcanoes in the early, high-flux stage of island evolution, such as La Palma, El Hierro, Fogo, and Pico, commonly preserve clinopyroxene compositions consistent with recycling of evolved mush in their mafic lavas. Mature islands with waning magma flux, such as Tenerife and Gran Canaria, lack this signature in their mafic rocks, suggesting that as a volcanic system ages and its magma supply declines, the deep evolved mush solidifies between recharge events and its record is erased.

The implications for hazard assessment are significant. Because a large share of magma evolution at low-flux ocean island volcanoes occurs at depths of 18 to 25 kilometers or deeper, much of the pre-eruptive process may be poorly resolved by conventional geophysical monitoring, which is most sensitive to shallower crustal signals. The 2021 Tajogaite eruption did produce deep seismicity at 20 to 25 kilometers in the days before magma broke the surface, and the new petrological evidence suggests that such deep signals may mark the critical moment when basanitic recharge begins to evacuate the mantle mush. Recognizing that evolved, potentially more explosive melts can be generated and stored near the Moho without prolonged shallow accumulation, and that their mobilization may precede eruptions by only days to weeks, gives monitoring networks a clearer target: the deep, hidden reservoirs where La Palma’s eruptions, and perhaps those of many ocean island volcanoes, truly begin.

Subject of Research: Magma storage and mush evacuation in the ocean island volcano La Palma revealed by clinopyroxene chemistry

Article Title: Recurrent evacuation of mantle mush in ocean islands revealed by clinopyroxene from La Palma

Article References: Caracciolo, A., Ubide, T., Ágreda-López, M., Herrera, R., Marquez, A., González-García, D., Huertas, M. J., Ancochea, E., Chicharro, N., Coello-Bravo, J. J., & Petrelli, M. (2026). Recurrent evacuation of mantle mush in ocean islands revealed by clinopyroxene from La Palma. Nature Communications, 17(1), Article 9362. https://doi.org/10.1038/s41467-026-77213-9

Image Credits: AI Generated

DOI: 10.1038/s41467-026-77213-9

Keywords: La Palma, Cumbre Vieja, clinopyroxene, crystal mush, magma recharge, thermobarometry, ocean island basalt, phonolite, Canary Islands, volcanology, Tajogaite eruption, magma plumbing system

The study, led by Serafin Corral, addresses what the author calls the narrative–biophysical gap, a chronic weakness in scenario planning. Futures studies has long produced compelling stories about alternative tomorrows — energy self-sufficiency, green tourism, resilient agriculture — but the plausibility of those stories is usually asserted rather than tested. A scenario may describe an attractive future without checking whether the energy and water flows it presupposes are physically attainable given the island’s renewable potential, infrastructure and sectoral metabolism. On a small island, where every drop of water and every kilowatt-hour can be accounted for, that gap between narrative and physics is not an academic quibble; it is the difference between futures that can guide the allocation of scarce public resources and futures that merely exercise the imagination.

To close the gap, the framework joins two powerful traditions. The first is Gallopín’s structural scenario method, which decomposes any future into critical dimensions, driving forces, strategic invariables, critical uncertainties and narrative images, and then evaluates each scenario against three criteria: plausibility, feasibility and desirability. The second is MuSIASEM — Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism — a fund–flow accounting framework that treats a society like a metabolism, tracking how energy, water and money flow through sectors defined by their human activity, land and capital. Together they produce a seven-step procedure in which qualitative narratives are screened against an empirical metabolic baseline: any scenario requiring resource flows the baseline cannot support is judged biophysically inadmissible.

The metabolic baseline for La Palma, compiled from official statistics for 2020–2023, is revealing in itself. Agriculture withdraws 68.0 cubic hectometres of water per year — a staggering 86.3 percent of total island use — overwhelmingly for banana irrigation, making water the binding constraint on every conceivable future. Residential and commercial demand together account for roughly three-quarters of electricity consumption. Gross value-added stood at €1,385.6 million in 2021, with public administration, health, education and recreation forming the largest branch on remarkably low resource footprints, while tourism and hospitality combine high metabolic density with high per-capita intensity. Comparative profiling places La Palma at 2,856 kWh per capita per year — between tourism-saturated Lanzarote at 4,123 and agro-ecologically governed Menorca at 2,144 — suggesting real efficiency headroom.

Crucially, the numbers were not imposed from above. Over three six-and-a-half-hour workshops in 2025, a standing multi-actor panel of 48 participants — spanning the Cabildo and municipalities, irrigation communities and banana cooperatives, tourism operators and the Instituto de Astrofísica de Canarias, scientists, and volcano-affected residents’ platforms — validated the causal map of the island system, scored the direct influence of eleven system variables on one another, tested draft scenarios against the feasibility filter, and co-designed the resulting policy roadmap. The process followed FAIR and CARE principles for knowledge governance, with written informed consent, anonymised reporting, and the knowledge returned to the community as a shared roadmap and a proposed Island Sustainability Observatory.

The elicited judgements were then formalised through a MICMAC-type cross-impact analysis, in which the influence matrix is multiplied by itself repeatedly until rankings stabilise, capturing effects transmitted along chains of intermediaries rather than only direct links. The result reorders the island’s power structure in instructive ways. Climate and water variability, scored modestly on direct links, rises to the determinant region once its influence through water quality, tourism and employment is traced. Environmental and water quality migrates from a mere outcome to a central transmission belt. And public policy emerges as the master lever — the only actionable determinant in a system where biophysical insularity is fixed and climate is exogenous. Tourism, energy and water quality occupy the relay region: the channels through which every intervention propagates and every shock is amplified.

Three scenarios to 2050 were constructed and quantified through a transparent delta model. In the Sustainable Island trajectory, electricity reaches 100 percent renewables by 2040 at about €0.10 per kWh, wastewater reuse covers half of agricultural irrigation, and the economy shifts toward higher value-added astro-, geo- and nature-based tourism — a reorientation already visible in the geotourism emerging around the Tajogaite edifice. Business-as-Usual restores the pre-eruption configuration behind modernised infrastructure. Decline compounds governance failure, climate stress and emigration. The quantified outcomes are stark: annual value-added changes of plus €63.7 million, plus €14.1 million and minus €127.4 million respectively, and cumulative balances to 2050 of roughly plus €1,100 million for Sustainable against plus €149 million for Business-as-Usual and about minus €2,600 million for Decline.

One of the study’s most striking findings is the asymmetry of choice: the potential loss is nearly three times the potential gain, and it is concentrated in a single variable. Tourism accounts for roughly three quarters of the value-added movement in both directions — the island’s greatest exposure and its greatest opportunity are the same sector seen from two ends. The water results deliver the most instructive lesson. Agricultural water volume falls by similar amounts under both Sustainable and Decline, yet the composition tells opposite stories: under Sustainable the reduction comes from reuse and precision irrigation at near-constant cost, buying supply security; under Decline the same physical reduction reflects an aquifer failing, forcing a shift to fossil-powered desalination at €0.80 per cubic metre. Identical movements in a physical indicator can carry opposite meanings — which is precisely why metabolic composition must be reported alongside aggregate numbers.

A sensitivity analysis stresses the conclusions honestly. The Sustainable balance of €1,116 million compresses to €480–970 million under the most adverse single assumptions and turns negative, at minus €132 million, only in a deliberately extreme case combining every adverse value with 5 percent discounting. But the ordering — Sustainable above Business-as-Usual above Decline — holds in every variation tested. The policy sequencing that follows is equally disciplined: enter through the one actionable determinant, public policy; deliver through the relay variables, starting with network rehabilitation that recovers the 25–30 percent of water now lost to leakage; and let renewable-powered desalination buffer the ungovernable climate determinant. The renewable transition is what makes the water strategy affordable, a synergy that exists only if the energy shift arrives first.

The deeper vulnerability, the study argues, is institutional rather than technical. Because public policy is the only governable lever, the entire trajectory depends on the most volatile variable in the system — one renewed at every electoral cycle — while the key investments have payback periods spanning several mandates. An Island Sustainability Observatory publishing the metabolic baseline, and a participatory long-term territorial plan aligning the island’s five governance tiers from municipalities to the European Union, would not guarantee continuity, but both raise the cost of abandoning it. The framework itself is designed to transfer to any island where sectoral energy, water, land and value-added data can be assembled, from the Azores to the Caribbean. Its value, the author concludes, is anticipatory: rendering the long-run consequences of present reconstruction choices legible while those choices remain open — before the next bifurcation point arrives unannounced, as on a September morning in 2021.

Subject of Research: Biophysically grounded scenario building for sustainability governance on the island of La Palma

Article Title: Biophysically-grounded scenario building for Island sustainability governance: A methodological framework and application to La Palma (Canary Islands, Spain)

Article References: Corral, S. (2026). Biophysically-grounded scenario building for Island sustainability governance: A methodological framework and application to La Palma (Canary Islands, Spain). Environmental and Sustainability Indicators, 32, Article 101531. https://doi.org/10.1016/j.indic.2026.101531

Image Credits: AI Generated

DOI: 10.1016/j.indic.2026.101531

Keywords: La Palma, scenario planning, MuSIASEM, island sustainability, Tajogaite eruption, water security, renewable energy, tourism, MICMAC analysis, socio-ecological metabolism, Canary Islands, post-disaster governance