plattornas

Plattornas, or tectonic plates, are the large, rigid sections of Earth's lithosphere that move slowly over the partially molten mantle beneath them. Each plate comprises crust and a portion of the upper mantle, and they vary in size, composition, and thickness. Continental plates tend to be granitic and less dense, while oceanic plates are denser and primarily basaltic.

Movement and boundaries: Plate motion is driven by convection currents in the mantle and occurs at about a few centimeters per year. Interactions at plate boundaries produce much of the planet’s seismic and volcanic activity. Divergent boundaries see plates move apart and new crust form; convergent boundaries involve collision that can create mountain ranges or cause subduction and volcanic arcs; transform boundaries feature horizontal slip that often triggers earthquakes.

Major and microplates: Among the major plates are the Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, and South American plates. In addition, numerous smaller or microplates—such as the Nazca, Cocos, Caribbean, and Philippine Sea Plates—play significant roles in regional geodynamics.

Evidence and history: The theory of plate tectonics integrates Alfred Wegener’s continental drift with geophysical data gathered in the mid-20th century. Key evidence includes patterns of magnetic stripes on the seafloor, age distribution of oceanic crust, earthquake and volcano locations, and direct measurements from geodetic networks.

Impact: Plate tectonics explains the distribution of continents and oceans, the formation of mountains, volcanic activity, earthquakes, and long-term changes in climate and geography through the rearrangement of Earth’s lithosphere over geological time.