The collision and joining of crustal fragments to a continent is called continental

Answer;

Continental accretion

Explanation;The collision and joining of crustal fragments to a continent is called the continental accretion.Accretion is the process through which materials such as sediment, volcanic arcs, or seamounts or blocks,  etc. are added to the tectonic plate or land mass. Many astronomical bodies, such as stars, galaxies or planets are formed by this process. Where the process of accretion has occurred the tectonic plates may have dense basaltic rocks which are indicative of oceanic lithosphere.