(used with a singular verb) the science dealing with dynamic processes or forces within the earth.
Origin of geodynamics
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
(functioning as singular) the branch of geology concerned with the forces and processes, esp large-scale, of the earth's interior, particularly as regards their effects on the crust or lithosphere
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012