Read an Academic Passage

The Theory of Plate Tectonics

The theory of plate tectonics, widely accepted since the 1960s, is the cornerstone of modern geology. It proposes that the Earth's rigid outer layer, the lithosphere, is broken into numerous large and small plates. These plates are not static; they move slowly over the underlying, semi-molten asthenosphere. This movement is the primary driving force behind many of the planet's most significant geological phenomena, including earthquakes, volcanic eruptions, and the formation of mountain ranges.

Early evidence for the theory came from Alfred Wegener's concept of continental drift, proposed in the early 20th century. He noted the remarkable jigsaw-puzzle fit between the coastlines of continents like Africa and South America. Further support emerged from the fossil record, which showed identical prehistoric species on continents now separated by vast oceans. However, the most conclusive evidence came later from studies of the ocean floor, which revealed seafloor spreading at mid-ocean ridges, where new crust is generated and pushes the plates apart.

The interactions at the boundaries where these plates meet are of three main types: convergent, where plates collide; divergent, where they pull apart; and transform, where they slide past one another. Each type of boundary is associated with distinct geological features and events. For instance, convergent boundaries are responsible for creating massive mountain chains like the Himalayas. By explaining these large-scale processes, plate tectonics provides a unified framework for understanding the dynamic nature of our planet.