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The Development of Plate Tectonics Theory

The theory of plate tectonics, which describes the large-scale motion of Earth's lithosphere, is the cornerstone of modern geology. However, this idea was not widely accepted until the mid-20th century. For many years, most scientists subscribed to the belief that the continents and oceans were permanent, fixed features of the Earth's surface. The first comprehensive theory of continental drift was proposed by Alfred Wegener in 1912. He presented evidence that the continents were once joined together in a single supercontinent he called Pangaea, citing the puzzle-like fit of coastlines, fossil similarities across oceans, and related rock formations.

Wegener's theory of continental drift was initially met with widespread skepticism. The primary objection from the scientific community was the lack of a plausible mechanism to explain how entire continents could move. Wegener proposed that continents plowed through the oceanic crust, but he could not provide a convincing force that could drive this movement. Without a mechanism, his radical ideas were largely dismissed for decades, though they continued to interest some geologists who saw merit in his extensive evidence.

The acceptance of Wegener's core idea came with new discoveries in the 1950s and 1960s. Ocean floor mapping revealed mid-ocean ridges, deep-sea trenches, and patterns of magnetic striping in the oceanic crust. These findings led to the development of the concept of seafloor spreading, which provided the missing mechanism. It was proposed that magma rises at mid-ocean ridges, creates new crust, and pushes the plates apart. This process, driven by convection currents in the Earth's mantle, finally provided a robust explanation for continental movement and evolved into the comprehensive theory of plate tectonics.