Revision 1 1 A Multi-faceted Experimental Study on the Dynamic Behavior of MgSiO 3 Glass in the 2 Earth ’ s

21 Pressure-induced structural modifications in silicate melts play a crucial role in controlling 22 dynamic processes in deep interiors of the Earth and other planets. The correlation between 23 structural and macroscopic properties of silicate liquids (densification, viscosity, chemical 24 differentiation, etc.), however, remains poorly understood. Here we report the evolution of 25 structural modifications and elastic properties of MgSiO3 glass to pressures up to ~70 GPa using 26 a combination of experimental techniques including micro-confocal Raman spectroscopy, angle 27 dispersive X-ray scattering, and Brillouin spectroscopy in the diamond anvil cell. Our combined 28 dataset provides consistent and complementary evidence of a series of pressure-induced 29 structural modifications in MgSiO3 glass at ~2, ~8, ~20, and ~40 GPa. Based on these results, a 30 structural evolution model for MgSiO3 glass is proposed. We also discuss the role of Mg-O 31 component in MgSiO3 and Mg2SiO4 glasses in controlling pressure-induced structural 32 modifications and mechanical responses in these supercooled liquids. 33