Exploring the Role of a Mushy Compliant Region in Sombrero Uplift Above the Socorro Magma Body

The Socorro Magma Body (SMB), one of the largest mid-crustal magma bodies in the world, is a pancake-shaped region located ~19 km under Socorro, NM. Nearly 100 years of geodetic measurements of surface deformation reveal that the ground above the center of the SMB has been uplifting at a nearly constant rate of 2.5 mm/yr. These measurements show the SMB is also undergoing enigmatic “sombrero uplift” where the center of uplift is surrounded by a ring of subsidence. This style of surface deformation has only been observed at the SMB and the Altiplano-Puna Magma Body in Bolivia. Current models explaining this include a rising diapir feeding the magma body, and a deep deflation source and shallow inflation in the crust. We propose a new, more physically and geologically justifiable model in which the sombrero is caused by a thermally weakened, mushy, compliant region surrounding the body. We construct finite element models and produce sombrero uplift without the need for the more complicated mechanisms used previously. Additionally, the duration of sombrero uplift is strongly controlled by the pressurization rate of the system. These findings impact our understanding of lithospheric magma plumbing systems which informs our knowledge of volcanoes and their hazards.