Accretion (geology)

In geology, accretion is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses.

The added material may be sediment, volcanic arcs, seamounts, oceanic crust or other igneous features.

[3] In addition to accumulated ocean sediments, volcanic island arcs or seamounts present on the subducting plate may be amalgamated onto existing continental crust on the upper plate, increasing the continental landmass.

[3] Most continents are composed of multiple accreted "terranes", pieces of low-density continental crust with different origins.

For example, North America is made up of multiple accreted terranes that collided with the Laurentian proto-continent, such as the Proterozoic Yavapai, Mazatzal, and Grenville Province Terranes.