Prediction of Silicate Melt Viscosity from Electrical Conductivity: A Model and its Geophysical Implications Anne Pommier1, Rob L. Evans2, Kerry Key3, James A. Tyburczy1, Stephen Mackwell4 and Jimmy Elsenbeck2 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA 3Scripps Institution of Oceanography, La Jolla, California, USA 4Lunar and Planetary Institute, Houston, Texas, USA The auxiliary material of this paper aims to provide the reader with the calculation of optical basicity of melts.