Superheated magma may fuel towering lava fountains, study finds
Lab experiments on rock from the 2021 La Palma eruption point to heat history as a factor in how volcanoes erupt.
Key points
- Manchester-led scientists examined material erupted in 2021 at Tajogaite on La Palma, Spain.
- Strong superheating delayed crystal formation in lab tests by more than eight hours, compared with about 20 minutes without it.
- Less crystal growth may let magma rise faster, which could favour dramatic lava fountains.
- The findings were published in Nature Communications.
- Researchers say the work could help improve volcanic hazard models.
Scientists from several countries, working under the direction of researchers at The University of Manchester, say extra heat inside magma may change how a volcano erupts. According to ScienceDaily, their study examined material erupted in 2021 at Tajogaite, on the Spanish island of La Palma. The findings appeared in the journal Nature Communications.
The team concentrated on superheating, a condition in which magma is heated past the point where its crystals would usually hold together. Their experiments indicate that such heating can slow crystal growth while the molten material climbs toward the surface.
Why heat changes crystal growth
Magma consists of liquid rock, gas and, at times, solid crystals beneath the surface. Once it breaks out of a volcano, people refer to it as lava. Crystals typically start to appear as magma cools, frequently attaching themselves to minute crystals already present that act as surfaces for new growth.
Extreme heat can interfere with that sequence in two ways. It can melt the tiny seed crystals that would otherwise prompt new ones to form, and it can reorganise the internal structure of the melt so that it is more evenly mixed and less inviting to fresh crystals. This matters because a higher crystal content makes magma thicker and harder to move, which in turn influences its rate of rise and the escape of trapped gases.
To watch these changes, the researchers used a specially built pressure vessel that lets X-rays pass through it. Working at Diamond Light Source, a large research facility, they applied synchrotron X-ray microtomography, a method that maps a material’s interior in three dimensions without cutting it open. Additional tests in Prague allowed samples to be studied over longer periods.
A much longer delay
The lab results showed a clear contrast. Magma that had not been superheated started forming crystals after roughly 20 minutes. In samples given a strong dose of superheat, crystallisation was held back by more than eight hours.
The team entered these measured delays into computer simulations of magma moving through the crust. The models produced two distinct scenarios. With delayed crystallisation, magma stays fluid and can climb faster, which may favour dramatic lava fountains. Lava fountains form when escaping gases throw molten rock high above a vent.
When crystals form earlier, magma thickens and ascends more slowly. That gives gases more time to leave, and the result tends to be a calmer effusive eruption, in which lava mainly spills across the surface.
What this means for forecasting
Monitoring teams track earthquakes, ground movement and gas output to spot changes in active volcanoes. Even so, forecasting the exact course of an eruption is still hard, since volcanoes with similar chemistry and gas levels can behave very differently.
The researchers argue that the heating history of magma before an eruption deserves more attention in forecasting models. Dr. Margherita Polacci, Senior Lecturer in Volcanology at The University of Manchester, noted that current hazard models mainly consider chemistry, gas content and pressure shifts. She said thermal history and crystallisation timing may also matter for hazard assessment. The team stresses that heat alone does not decide how violent an eruption becomes; it is one piece of a complex picture.
Frequently asked questions
What is superheating in magma?
It describes heating magma beyond the temperature where its crystals would usually stay intact. According to the research, this extra heat can hold back crystal formation.
Where was the magma studied?
The samples came from material erupted in 2021 at Tajogaite on the Spanish island of La Palma. The researchers recreated volcanic conditions in the laboratory.
Does this mean lava fountains can be predicted?
Not yet. Magma temperature by itself does not settle how violent an eruption becomes, though the findings may support better volcanic hazard assessment.
Sources
- ScienceDaily: Superheated magma could fuel towering lava fountains
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