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The Theory of Plate Tectonics

The theory of plate tectonics provides a comprehensive model for understanding the large-scale movements and features of Earth's surface. It posits that the planet's outer layer, the lithosphere, is broken into several large and small rigid plates. These plates are not static; they float on the semi-fluid asthenosphere beneath them and are in constant, slow motion. The movement of these plates, driven by convection currents in the underlying mantle, is responsible for some of the planet's most dramatic geological phenomena, including earthquakes, volcanic eruptions, and the formation of mountain ranges.

There are three main types of boundaries where these tectonic plates interact: divergent, convergent, and transform. At divergent boundaries, plates move apart, allowing magma from the mantle to rise and create new crust, as seen at the Mid-Atlantic Ridge. At convergent boundaries, plates collide. Depending on the types of plates involved, one may be forced beneath the other in a process called subduction, leading to volcanic arcs and deep ocean trenches. If two continental plates collide, they can buckle and fold, forming massive mountain ranges like the Himalayas.

The third type of boundary is the transform boundary, where plates slide horizontally past one another. The friction between the plates prevents them from sliding smoothly; instead, stress builds up until it is released in a sudden jerk, causing an earthquake. The San Andreas Fault in California is a well-known example of a transform boundary. The theory of plate tectonics, developed in the mid-20th century, revolutionized the earth sciences by providing a unified explanation for a wide range of observations that had long puzzled geologists.