Permeability Heterogeneity in Enclave Bearing Dome Lavas: A Mechanism for Cyclic Explosive Gas Venting

Gas escape from volcanic systems is regulated by permeable pathways. When gas escape is hindered, pressure within the edifice can increase, possibly resulting in explosive eruptions. We present a study on enclave bearing dome lavas from Chaos Crags and Lassen Peak, California, to understand the impact of mechanical and textural heterogeneities on the permeability fabric of dome lavas. We combine field and laboratory measurements of permeability and porosity. The data show that in the presence of mechanical heterogeneities, shear deformation induces permeability anisotropy and heterogeneity with higher permeability parallel to the shear fabric and varying on decimeter scale around mechanical heterogeneities. Based on these insights we discuss implications for the accumulation of gas pockets in the conduit margin, which may contribute to cyclic explosive gas venting commonly observed at dome forming volcanoes.