The recognition of terranes and terrane accretion has fundamentally changed the way we view the development of continental crust. The terrane concept originated from studies of the western Cordillera of North America, where it was demonstrated in the 1970s that microplates had travelled substantial distances before being amalgamated to cratonic North America. Since these early studies, the terrane concept has been widely applied to older orogenic belts, including the Appalachians and most of the Precambrian shields.
Despite the acceptance of the terrane concept, a number of fundamental questions remain regarding the process of terrane accretion and its interaction with transform faulting and igneous and metamorphic events. Still not fully understood are: the coupling processes of mantle with deeper crust, and of deeper crust with upper crust; how pieces of continental crust with different histories respond to juxtaposition; the mechanism of the Mono's formation; and the behavior of fluids (melt and aqueous) with the changing stress field during accretion.