List of tectonic plates
This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around thick and consist of two principal types of material: oceanic crust (also called "sima" from silicon and magnesium) and continental crust ("sial" from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks. Current plates. Geologists generally agree that the following tectonic plates  currently exist on Earth's surface with roughly definable boundaries. Tectonic plates are sometimes subdivided into three fairly arbitrary categories: "major" (or "primary") "plates", "minor" (or "secondary") "plates", and "microplates" (or "tertiary plates"). Major plates. These plates comprise the bulk of the continents and the Pacific Ocean. For purposes of this list, a major plate is any plate with an area greater than 20 million km. Minor plates. These smaller plates are often not shown on major plate maps, as the majority do not comprise significant land area. For purposes of this list, a minor plate is any plate with  an area less than 20 million km but greater than 1 million km. Microplates. These plates are often grouped with an adjacent major plate on a major plate map. For purposes of this list, a microplate is any plate with an area less than 1 million km. Some models identify more minor plates within current orogens (events that lead to a large structural deformation of Earth's lithosphere) like the Apulian, Explorer, Gorda, and Philippine Mobile Belt plates. There may be scientific consensus as to whether such plates should be considered distinct portions of the crust; thus, new research could  change this list. Ancient continental formations. In the history of Earth many tectonic plates have come into existence and have over the intervening years either accreted onto other plates to form larger plates, rifted into smaller plates, or have been crushed by or subducted under other plates. Ancient supercontinents. The following list includes the supercontinents known or speculated to have existed in the Earth's past: Ancient plates and cratons. Not all plate boundaries are easily defined, especially for ancient pieces of crust. The following list of ancient cratons, microplates, plates, shields, terranes, and zones no longer exist as separate  plates. "Cratons" are the oldest and most stable parts of the continental lithosphere and "shields" are the exposed area of a craton(s). "Microplates" are tiny tectonic plates, "terranes" are fragments of crustal material formed on one tectonic plate and accreted to crust lying on another plate, and "zones" are bands of similar rocks on a plate formed by terrane accretion or native rock formation. Terranes may or may not have originated as independent microplates: a terrane may not contain the full thickness of the lithosphere.