Lithospheric flexural stresses beneath volcanic loads are horizontally strongly compressive towards the top of the lithosphere. Thus, while magma transport through the brittle lithosphere occurs via fractures, the fracture paths under the volcanic center are predicted by stress trajectories to be horizontal and thus unable to supply melt to the volcanic edifice where eruptions are observed. Moreover, the magnitude of the compressive stresses under large loads would close down any vertical magma paths. Both problems may be resolved by additional stresses due to melting or thermomechanical erosion of fracture walls developing over the life-span of the volcano. Fractures form and close frequently in the seismogenic zone of the lithosphere, with each fracture eroding away a small amount of material. The total amount of material removed makes the stress field more tensile, thereby facilitating the long-lived and vertically oriented magma pathways necessary to build discrete volcanic structures. ¿ 2001 American Geophysical Union