Plate Tectonics Quiz

Key evidence includes the fit of continental coastlines, matching fossils found on separate continents, and identical rock formations across ocean basins. Alfred Wegener used these observations when he proposed continental drift in 1915, and later discoveries like seafloor spreading provided further support. The existence of subduction zones, mid-ocean ridges, and volcanic island arcs all confirm that plates are in constant motion.

The supercontinent Pangaea began breaking apart about 200 million years ago, which marks a major milestone in the history of plate movement. Pangaea was a single landmass that gradually split into the continents we recognize today. The underlying processes driving plate motion are thought to have been active for billions of years before that breakup.

Plate motion is driven largely by convection currents in the mantle, where heat from Earth's interior causes slow circulation of molten rock. Slab pull, where a dense oceanic plate sinks at a subduction zone, is also considered a major force. These mechanisms work together to move plates toward, away from, or past one another.

Volcanoes form at subduction zones when an oceanic plate sinks beneath another plate and melts due to increasing heat and pressure. The resulting magma rises through the crust and reaches the surface. When this happens in the ocean, a chain of volcanoes called a volcanic island arc is created.

The three types are divergent, convergent, and transform boundaries. At divergent boundaries, plates move apart; at convergent boundaries, they collide, with one sometimes subducting beneath the other or both crumpling to form fold mountains like the Himalayas. At transform boundaries, plates slide sideways past each other, which is where earthquakes are most likely to occur.

Subduction is the process where one tectonic plate sinks beneath another. When two oceanic plates converge, the denser one subducts and forms a deep ocean trench. The melting of the subducting plate also produces magma that rises to form volcanic island arcs at the surface.