Platemotion

Platemotion refers to the movement of Earth's lithospheric plates relative to one another as described by plate tectonics. The Earth's outer shell is divided into tectonic plates that move at rates measured in millimeters to centimeters per year due to convection in the semi-fluid asthenosphere beneath them. Movement occurs at plate boundaries: divergent boundaries where plates move apart; convergent boundaries where they collide; and transform boundaries where they slide past one another. The motion is driven by mantle convection, slab pull, and ridge push, and is influenced by gravity, density contrasts, and thermal structure. Measurements rely on GPS geodesy, seafloor magnetic anomalies, earthquake distributions, and hot spot tracks.

Evidence for platemotion includes symmetrical magnetic reversals on either side of mid-ocean ridges, age progression of oceanic crust away from ridges, and the distribution of earthquakes and volcanoes along plate boundaries. Impacts of plate motion include the formation of mountain ranges (orogeny), ocean basin evolution, and seismic and volcanic hazards.

Historically, the concept arose from late 19th to mid-20th century ideas of continental drift proposed by Wegener, with strong support from paleomagnetism and seafloor spreading data compiled in the 1960s, leading to the modern theory of plate tectonics. The term platemotion is used informally to describe the velocity vector fields of plates or to discuss relative motion between plates, sometimes in geodynamic modeling and kinematic reconstructions.

See also: Plate tectonics, Continental drift, Seafloor spreading, Mantle convection.