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March 2025 ESRFnews

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VOLCANO is erupting at the BM18 beamline.

Not a real volcano of Krakatoan proportions,

but something dynamically similar – an

alumina vessel the size of a piece of chalk, part filled with

synthetic rock. Suspended in the beamline well away

from anything that is likely to catch fire, this model

volcano is heated above 800 C until the rock melts

becoming a magma that bubbles and rises Depending

on the experimental conditions the magma erupts with

Hawaiian fluidity or as in Krakatoa it explodes

In real volcanoes the precise conditions that result in

an explosion rather than calm effusive lava flow are

highly contested Studying his model at BM18 ESRF

scientist Benoît Cordonnier has a major advantage in

this debate in that he can directly observe the dynamics

of the processes leading to the eruption in particular

the key parameters of decompression rate and apparent

magma viscosity His results point towards new modes

of decompression never observed before with the

implication that explosive volcanoes can occur at lower

rates of pressure drop than previously thought. Such

insights are thanks partly to his novel volcano model,

but also to the matchless flux of EBS X-rays, which are

able to image much thicker apparatuses and samples of

rock and magma than those of any other synchrotron.

We need to take more measurements but so far were

very enthusiastic about our results says Cordonnier

Whats more theyre attracting wellknown

European volcanological teams from Manchester in

the UK to Camerino in Italy they all want to use this

instrumentation too

Still there has been a limit to how accurately

volcanoes can be modelled at synchrotrons even for a

skilled experimenter such as Cordonnier Although

eruptions can happen quickly underlying geological

conditions can develop over years far longer than

typical synchrotron experiments which usually take

place over a single sixthmonth scheduling period

Climate change, earthquakes and volcanoes all

involve geological systems that change too slowly for

typical synchrotron experiments. A new mode of

ESRF access will change that.

Taking it slow

Benoît

Cordonnier’s

model volcano

at the BM18

beamline.

E S R F/ S T E F C A N D É