Lava, steam... and a little lesson in physics. Exploring the Leidenfrost effect in volcanic eruptions
06/2025
Volcanic eruptions sometimes reveal fundamental physical phenomena that have yet to be fully exploited. Using the example of Mount Etna, this article highlights the Leidenfrost effect — a key mechanism at the heart of the European project LeidenForce, supported by the Horizon Europe programme. This project aims to push the boundaries of our understanding of this phenomenon in order to explore its technological potential.
Over the last few days, impressive images of Etna erupting have once again captured the world's attention. Columns of ash, lava fountains, incandescent flows: the Sicilian volcano, one of the most active in Europe, reminds us of its power.
But watching lobes of lava rush down the snow-covered slopes of the Valle del Bove, generating lahars (mudflows of volcanic origin composed of water and volcanic debris) and producing intense clouds of steam upon contact, an unexpected question came to mind:
What connection could there be between a volcanic eruption and a water droplet “dancing” on a hot plate?
A strange parallel? Not so much.
When lava meets water: Physics comes into play
When a lava flow suddenly comes into contact with water — whether seawater, lake water, or snowmelt — one might expect it to solidify immediately. But this is not always the case.
In fact, a well-known phenomenon in physics comes into play: the Leidenfrost effect.
What is the Leidenfrost effect?
It occurs when a water droplet falls onto a surface much hotter than its boiling point (like a hot plate). The droplet doesn’t evaporate instantly: it forms a vapor cushion which temporarily protects it from the heat, allowing it to “levitate” on that vapor layer.
A similar phenomenon can occur with lava. When lava meets cold water, a layer of water vapor instantly forms at the contact surface, which slows down the cooling of the still-fluid lava inside.
This mechanism explains the formation of Pillow Lavas
In underwater or wet environments, lava encountering water sometimes forms curious structures: solidified tubes or cushions called pillow lavas.
Behind this characteristic shape, the Leidenfrost effect plays a crucial role: the steam acts as a shield, giving the lava time to move slightly beneath its crust before solidifying. The result is stacked lava cushions, typical of submarine eruptions or eruptions in the presence of water.
Understanding to act better
Incorporating this phenomenon into lava flow simulation models allows for more accurate predictions of their progression, which is crucial for risk management. This helps design more effective monitoring tools, better plan evacuations, protect infrastructure, and thereby reduce the impact of eruptions on populations.
This connection between volcanology and fluid physics was first formulated in 1984 by A.A. Mills, in a pioneering article titled Leidenfrost layers and lava published in Nature.
Read the original article:
MILLS, A. A. (1984). LEIDENFROST LAYERS AND LAVA. NATURE, 312(5995), 684.
The eruption of Mount Etna reminds us how essential it is to understand the physical laws at work in geological phenomena in order to better anticipate and adapt to them.
The LeidenForce project is driven by this same scientific curiosity: by exploring the boundaries of the Leidenfrost effect, our ambition is to push forward the limits of its understanding and to reveal its potential at the crossroads of fundamental science and applied innovation.
