Persistent activity at explosive volcanoes is often characterized by short explosive bursts, which occur at periodic intervals numerous times per day, sometimes lasting for years to decades. Many of these systems present relatively evolved compositions (andesite to rhyolite), but the same periodic behavior can also be observed at open systems with more mafic compositions, such as Semeru in Indonesia or Karymsky in Kamchatka for example.
I use numerical modeling of magma ascent (DOMEFLOW), to identify the conditions that lead to and control periodic eruptions in basaltic andesite systems, where the viscosity of the liquid phase can be drastically lower. The characteristic timescale and magnitude of the eruptive cycles are controlled by the overall viscosity of the magma, with higher viscosities leading to shorter cycles and higher flow rates. My results suggest that periodicity can exist in more mafic systems with relatively lower chamber pressures, and may explain why such eruptions sometimes persist for decades.
![Comparison of model output with observed data at Semeru. The timing and magnitude of explosion cycles can be reproduced in both the deformation [top] and degassing [bottom] observed at the surface.](https://i0.wp.com/www.jfsmekens.com/wp-content/uploads/2021/05/Figure06.png?fit=730%2C487&ssl=1)