Superheated magma delays crystal formation, fueling explosive lava fountains

Scientists analyzing rock from the 2021 Tajogaite eruption on La Palma identified a heat-driven mechanism that can alter volcanic behavior. When magma becomes hotter than the temperature at which crystals are stable, tiny seed crystals dissolve, and the melt’s internal structure becomes more uniform, hindering new crystal growth. Laboratory tests at the Diamond Light Source, combined with longer-term experiments in Prague, showed that superheated magma can avoid crystallization for over eight hours, compared with about twenty minutes for cooler samples.

Simulations incorporating these delays indicate that the melt remains fluid enough to ascend rapidly, generating the dramatic lava fountains observed in some eruptions, whereas earlier crystallization leads to slower, effusive flows. Lead author Barbara Bonechi highlighted the use of a novel X-ray transparent pressure vessel to observe these processes in real time. Co-author Margherita Polacci noted that current hazard models rarely consider pre-eruptive thermal effects, implying that this insight could improve eruption forecasts.