Lava fountains look like pure violence, yet the rock feeding them can be strangely slow to change. In laboratory runs, magma that had been heated above the temperature at which crystals are stable held off forming new crystals for more than eight hours. Magma that had not been superheated started crystallizing in about 20 minutes. A team led by the University of Manchester says that gap could decide whether a volcano pours or sprays.
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The experiments used magma from the 2021 eruption on La Palma in Spain’s Canary Islands, and they were filmed in three dimensions as the rock cooled.
Seeds that dissolve and a delay that stretches
The study, announced by the University of Manchester on June 8, 2026, was published in Nature Communications with Dr Barbara Bonechi, a research associate at Manchester, as lead author. Its formal name is “Superheating in mafic magmas controls clinopyroxene nucleation delay and magma ascent dynamics,” and the paper’s DOI carries the full methods. Magma normally contains tiny pre-existing crystals that act as seeds, giving new crystals a place to grow as the melt cools on its way up. Superheating dissolves those seeds and also makes the melt’s internal structure more uniform, so it becomes less able to start crystals from scratch.
The result is a long pause. Bonechi’s team watched it happen rather than inferring it afterward, and she said the setup let the group observe these processes in situ, as the EurekAlert copy of the release also reports. The seeds, the delay and the eight-hour figure all come from that direct observation, not from a back-calculation after the fact.
X-ray tomography on a pressurized magma sample
The imaging was done at Diamond Light Source, Britain’s national synchrotron, where an X-ray-transparent pressure vessel let researchers hold magma at volcanic pressures and temperatures while fast X-ray microtomography recorded crystals appearing. Diamond’s account of the work says additional runs in Prague allowed longer observation times than the beamline schedule permits. The delays measured in both settings were then fed into numerical models of magma rising through a conduit.
The University of Bristol’s petrology group, whose member Richard Brooker was on the international team, described the experiments in its own summary as the first full four-dimensional tomography runs from its pressure vessel. Bristol’s page adds that the superheated case rose about an order of magnitude faster in the models.
From a crystal delay to fountain or flow
Crystal content sets viscosity, and viscosity sets how fast magma climbs and how easily gas escapes. When crystals form early, the magma stiffens, slows, and lets gas bleed off gradually, which favors gentler effusive eruptions. When crystallization is held back, the magma stays fluid, races upward, and arrives at the surface still carrying its gas. In the models, such a long delay could promote what the Manchester release calls dramatic lava fountaining. The wording is conditional because the fountains come from simulations built on lab measurements, not from watching a real vent.
Dr Margherita Polacci, a senior lecturer in volcanology at Manchester and a co-author, framed the gap in current practice. Volcanic hazard models, she said, typically focus on magma chemistry, gas content and pressure changes, while pre-eruptive thermal history and crystallization kinetics may also play an important role in controlling how magma ascends and erupts. Bonechi’s own summary line is that the history of crystal and bubble growth can dramatically control how a magma erupts.
The authors also say the findings could improve how monitoring signals are interpreted. A volcano whose magma carries extra heat from deep storage might be capable of fast, fountain-style ascent even when its chemistry and gas content look ordinary, and that is a distinction current hazard models do not capture.
The contrast in clocks is what makes the numbers useful. When crystals form within about 20 minutes, they stiffen the melt while it is still climbing. When the delay stretches past eight hours, the melt can stay fluid for the whole trip, which is the scenario the models link to fountaining. Working from the Manchester-led measurements, the researchers fed the delays into ascent models to compare the two cases, and the superheated case rose about an order of magnitude faster, according to the Bristol summary.
Limits of a single magma type
Everything above rests on one kind of material, the mafic magma erupted at Tajogaite, and on crystals of one mineral family, clinopyroxene. The study does not tie the delay to any particular eruption’s fountains, and the project’s releases give no measurement of how superheated real magma is before it leaves a chamber. The ScienceDaily write-up that circulated on Nov. 13 repeats the study’s core contrast of eight hours against 20 minutes, but the underlying paper is the one to cite for the experimental conditions.
Whether superheating is common enough beneath real volcanoes to matter for forecasts is the question the authors leave open, and answering it would take temperature estimates from erupted rocks at fountaining volcanoes, set beside the delays measured here.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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