Crystal‐Rich Magma Is Solid‐Like and Liquefies When Deformed

Abstract The rheology of highly crystalline magma regulates its mobility, which may, in turn, determine the occurrence and styles of volcanic eruptions. We measured the rheology of high‐temperature magma with a basaltic‐andesite composition to document the properties that govern the transition from solid‐like to liquid‐like behavior. The measured elasticity in the solid‐like regime is three orders of magnitude lower than the shear modulus for a viscous silicate melt at high frequency. A considerable reduction of shear modulus is observed by increasing strain amplitude, indicating that the crystals unjam and the magma undergoes liquefaction. Crystal‐rich magma behaves as a dense suspension in which rheology changes rapidly with increasing strain and strain rate. Such characteristics enable the rapid mobilization of magma to trigger eruptions.