Millions of years ago, Earth’s landmasses were united in a single, immense supercontinent known as Pangea. This vast landform existed during the late Paleozoic and early Mesozoic eras, roughly from 335 to 175 million years ago. Pangea gradually began to fracture and drift apart. This breakup initiated the long process that ultimately shaped the distinct continents and oceans we recognize on Earth today.
The Initial Dissolution
The fragmentation of Pangea commenced around 200 to 230 million years ago, during the Triassic period. This initial stage involved rifting, primarily between what would become Africa, South America, and North America. Magma welled up through weaknesses in the Earth’s crust, forming volcanic rift zones and new oceanic basins.
Pangea first split into two major landmasses: Laurasia in the northern hemisphere and Gondwana in the southern hemisphere. The Tethys Sea started forming between these two supercontinents. Simultaneously, the nascent Central Atlantic Ocean began to open as North America and Africa drifted apart.
Continents on the Move
Following the initial split, Laurasia and Gondwana continued their fragmentation during the Jurassic and Cretaceous periods, from approximately 200 to 66 million years ago. Gondwana, the southern supercontinent, underwent significant breakup, giving rise to South America, Africa, Antarctica, Australia, and the Indian subcontinent. For example, the South Atlantic Ocean began opening around 140 million years ago as South America and Africa separated.
Laurasia, the northern supercontinent, also continued to divide, splitting into North America and Eurasia (Europe and Asia). The Atlantic Ocean widened, further separating North America from Eurasia. Concurrently, the Indian Ocean began to form and expand as India started its northward journey after detaching from Antarctica and Australia around 150 million years ago.
Shaping the Modern World
The movements of continents continued into the Cenozoic Era, leading to their current configurations. The Indian subcontinent collided with Asia around 55 to 40 million years ago. This impact crumpled the Earth’s crust, resulting in the formation of the Himalayan mountain range.
Australia, having separated from Antarctica, embarked on a northward trajectory. This separation, largely completed around 33.5 to 30 million years ago, opened the Tasmanian Gateway, allowing the development of the Antarctic Circumpolar Current. This current played a role in Antarctica’s thermal isolation and the growth of its ice sheets. North and South America eventually connected, forming the Isthmus of Panama, which significantly altered ocean currents. Africa’s movements finalized its position, and parts of the ancient Tethys Sea closed, leaving behind remnants such as the Mediterranean, Black, and Caspian Seas.
The Driving Forces
The movement of Earth’s continents is primarily driven by plate tectonics. The Earth’s rigid outer shell, the lithosphere, is broken into several pieces known as tectonic plates. These plates constantly move across the semi-fluid asthenosphere beneath them.
This movement is powered by convection currents within the Earth’s mantle, the layer below the crust. Heat from the Earth’s core causes mantle material to become less dense and rise; as it cools near the surface, it becomes denser and sinks, creating a slow, circulating motion. This circulation exerts forces on the overlying tectonic plates, causing them to move. Plate boundaries are categorized into three main types based on their relative motion: divergent (plates move apart), convergent (they collide), and transform (they slide past each other).