The separation of South America and Africa fundamentally reshaped global geography and influenced the evolution of life. This continental divergence is a powerful demonstration of plate tectonics, the process by which the planet’s rigid outer shell moves across the mantle. Defining the timeline requires looking back across hundreds of millions of years, tracing the slow forces that pulled the two massive landmasses apart. The split was not a single moment but a prolonged process that continues today.
The Precursor: Setting the Stage
The process of separation began when the two continents were joined as a single landmass. Africa and South America were the western components of Gondwana, a supercontinent that also incorporated Antarctica, Australia, and India. Gondwana was itself part of the larger supercontinent Pangea.
The initial instability started in the Early Jurassic Period, roughly 180 million years ago (Ma). Forces within the Earth’s mantle created zones of weakness across Gondwana, leading to widespread stretching and thinning of the continental crust. These movements formed a network of rift valleys across the future boundary, but did not immediately create an ocean.
The Rifting Phase: Initial Breakup and South Atlantic Formation
The active separation of South America and Africa began around 140 million years ago (Ma), marking the onset of the Cretaceous Period. Tensional forces ruptured the continental crust, transitioning the rift valleys into a true spreading center and systematically creating the South Atlantic Ocean basin.
The continental breakup progressed over tens of millions of years, essentially unzipping the continents from south to north. The southernmost parts pulled apart first, while northern regions remained connected longer. This progression is evident because the oceanic crust is older near the southern tips and younger toward the equator.
As the plates diverged, magma from the mantle rose, solidifying to form new oceanic crust along the spreading center, which became the Mid-Atlantic Ridge. The period between 140 Ma and 100 Ma was the most dynamic, transforming the narrow rift valley into a widening sea.
Measuring the Distance: Rates of Separation and Ongoing Movement
The creation of the South Atlantic Ocean is a direct result of seafloor spreading, a process that continues to widen the distance between the continents. The rate of movement is not constant and varies along the Mid-Atlantic Ridge.
Currently, the separation between the South American and African plates is relatively slow, averaging approximately 2 to 4 centimeters per year. This velocity is comparable to the rate at which human fingernails grow. Although this rate seems insignificant on a human timescale, it accounts for the thousands of kilometers of ocean separating the landmasses over geological time.
The Mid-Atlantic Ridge acts as the boundary where this movement occurs, a submerged mountain range where new oceanic crust is continuously generated. This ongoing activity confirms that the separation is a continuous process driven by the planet’s internal heat and convection currents.
Geological and Biological Evidence
The timeline and mechanism of this massive separation are supported by multiple lines of scientific evidence gathered from both continents and the ocean floor. One compelling observation is the remarkable fit between the eastern coastline of South America and the western coastline of Africa, much like pieces of a jigsaw puzzle. This fit becomes even more precise when comparing the edges of the continental shelves.
Geologists have also found that rock formations and ancient mountain belts on one continent align perfectly with corresponding structures on the other. For instance, geological complexes in Brazil share identical mineral compositions and age with those found in West Africa, proving the landmasses were once fused together.
Biological evidence further validates the timeline of connection and subsequent isolation. Paleontologists have discovered fossils of the same ancient species of terrestrial and freshwater animals across both continents. For example, the presence of closely related titanosaur sauropods, such as Paralititan in Africa and Argentinosaurus in South America, suggests a shared evolutionary heritage before the land bridge was severed.