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The Theory of Plate Tectonics

The theory of plate tectonics, established in the 1960s, revolutionized the field of Earth sciences. It posits that the Earth's outermost layer, the lithosphere, is broken into a mosaic of large and small rigid plates. These plates are not static; they are in constant, slow motion, floating on the semi-fluid asthenosphere beneath them. This theory provides a unified framework for understanding many of the planet's most significant geological features and events.

The movement of these plates is driven primarily by convection currents in the underlying mantle, where hot rock rises and cooler rock sinks. Plate boundaries are the primary sites of geological action. At divergent boundaries, such as the Mid-Atlantic Ridge, plates pull apart, and magma rises to create new crust. At convergent boundaries, plates collide, which can result in one plate sliding beneath the other in a process called subduction, forming deep ocean trenches and volcanic mountain ranges. This constant interaction makes plate boundaries zones of intense activity.

Plate tectonics is the fundamental explanation for earthquakes and volcanic eruptions. Earthquakes are most common at transform boundaries, where plates grind horizontally past one another, like the San Andreas Fault. Stress builds up along the fault line until the rocks rupture, releasing energy as seismic waves. Most of the world's active volcanoes are located along convergent plate boundaries, forming the "Ring of Fire" around the Pacific Ocean. Understanding these processes is critical for assessing natural hazard risks and working to mitigate their impact on human populations.