The role of tuffs in sealing volcanic conduits

In volcanoes, hot fluids circulate through the rocks and change their physical and chemical properties. Here we study how these changes occur in different rocks within the volcano's interior. We find that in lavas, rocks that generally have a low volume of pores, these fluids create new pathways to flow through by dissolving the rock-forming minerals. In contrast, fluid pathways in tuffs, which are inherently highly porous rocks, are blocked by the precipitation of new minerals in the pore spaces. Compaction under the pressure of overlying rocks in the volcano's interior can further reduce the fluid pathways through tuffs. Such reduction in fluid pathways within the volcano can aid the build-up of pressure, making them prone to explosive eruptions.