Platetectonics

Platetectonics, commonly written as plate tectonics, is the scientific theory that explains the large-scale movement of Earth's lithospheric plates. The outer shell of the planet consists of several rigid plates that ride atop the partially molten asthenosphere. These plates interact at their boundaries, producing most of Earth's seismic and volcanic activity. Major plates include the Pacific, North American, Eurasian, African, Antarctic, and Indo-Australian plates, along with numerous smaller plates such as the Cocos, Nazca, and Caribbean plates.

Plate boundaries are classified as divergent, where plates move apart; convergent, where they move toward one another; and transform, where they slide past each other horizontally. Divergent boundaries create new lithosphere at mid-ocean ridges; convergent boundaries can form mountain belts, volcanic arcs, and subduction zones; transform boundaries produce significant earthquakes along faults.

The theory integrates evidence from seafloor spreading, paleomagnetism, earthquake distributions, and hotspot tracks. Mechanisms driving plate motion include mantle convection, slab pull, and ridge push. The theory explains the supercontinent cycle and patterns of volcanism, mountain building, and crustal recycling over geological time.

Historically, the idea built on Alfred Wegener’s continental drift proposal in the early 20th century and gained broad acceptance in the 1960s with supporting geophysical data. Plate tectonics remains a unifying framework for understanding Earth’s geology and its dynamic processes.