The Earth's continents and oceans are not static but have undergone a dynamic evolution over billions of years, a process best explained by the unifying theory of plate tectonics, built upon earlier foundational ideas. The journey began with Alfred Wegener's concept of Continental Drift in the early 20th century. Wegener proposed that continents were once joined in a supercontinent called Pangea, which later broke apart and drifted to their current positions. His evidence included the 'jigsaw fit' of continents, matching fossil distributions across oceans, similar rock types and mountain ranges on separated landmasses, and paleoclimatic indicators like glacial striations. While compelling, Wegener lacked a plausible mechanism for continental movement.

This mechanism emerged with the development of the Seafloor Spreading hypothesis in the 1960s by Harry Hess and Robert Dietz. They proposed that new oceanic crust is continuously generated at mid-ocean ridges and then moves away from the ridges, eventually being consumed at deep-ocean trenches. Evidence for seafloor spreading came from magnetic anomalies on the ocean floor, which showed symmetrical patterns of magnetic reversals parallel to the ridges, and the increasing age of oceanic crust with distance from the ridges.

These ideas culminated in the theory of Plate Tectonics, which posits that the Earth's lithosphere is divided into several large and small rigid plates that move relative to each other over the semi-fluid asthenosphere. The driving force for this movement is believed to be mantle convection, where heat from the Earth's core creates convection currents that drag the plates.

Plate interactions at their boundaries define the evolution of continents and oceans:

• Divergent Boundaries: Where plates move apart, new oceanic crust is created through volcanism at mid-ocean ridges. This process leads to the opening and widening of ocean basins, such as the Atlantic Ocean, which formed from the breakup of Pangea. Rift valleys, like the East African Rift, represent the initial stages of continental rifting that can eventually lead to new ocean formation.
• Convergent Boundaries: Where plates collide, oceanic crust is typically subducted beneath another plate (either oceanic or continental), forming deep-ocean trenches, volcanic arcs (e.g., Andes Mountains, Mariana Trench), and consuming oceanic crust. When two continental plates collide, neither subducts significantly due to their buoyancy, resulting in intense compression, folding, and faulting, leading to the formation of massive mountain ranges like the Himalayas.
• Transform Boundaries: Where plates slide past each other horizontally, crust is neither created nor destroyed, but significant seismic activity occurs (e.g., San Andreas Fault).

The continuous cycle of supercontinent assembly and breakup, known as the Wilson Cycle, illustrates the long-term evolution. Continents coalesce into supercontinents, which then rift apart, forming new ocean basins. These oceans eventually close as plates converge, leading to the formation of new mountain belts and the assembly of another supercontinent. This cyclical process, driven by plate tectonics, has shaped the distribution of landmasses and oceans, influencing global climate, biodiversity, and geological processes throughout Earth's history.