Main Entry: plate tectonics

Function: noun plural but singular in construction

Date: 1969

1 : a theory in geology: the lithosphere of the earth is divided into a small number of plates which float on and travel independently over the mantle and much of the earth's seismic activity occurs at the boundaries of these plates
2 : the process and dynamics of tectonic plate movement; also : a similar process on a body other than earth

— plate–tectonic adjective