Africa is an ancient landmass defined by colossal landforms, resulting from its position largely on the stable African Plate. Composed of several Precambrian cratons dating back over three billion years, the continent has experienced uplift and rifting rather than the continental collisions that formed younger, folded mountains elsewhere. The scale of these features—from vast plateaus to enormous river basins—reflects the continent’s long and relatively undisturbed geological history.
The Great Rift Valley System
The most dramatic geological feature of the continent is the East African Rift System (EARS), a developing divergent plate boundary actively splitting the African Plate. This enormous fracture zone extends approximately 4,000 kilometers from the Afar Triple Junction in the north down to Mozambique. The process involves the Somali Plate pulling away from the larger Nubian Plate at a slow rate of about six to seven millimeters each year.
The rifting creates a distinctive landscape known as horst and graben topography. Grabens are the deep, elongated rift valleys formed by the sinking of the land between parallel faults, while horsts are the uplifted blocks of crust bordering these valleys. This tectonic activity is responsible for the formation of the African Great Lakes, many of which are deep, narrow basins like Lake Tanganyika and Lake Malawi that occupy the rift floor.
Volcanism is linked to this extensional faulting as the crust thins, allowing magma to rise closer to the surface. Though situated outside the immediate valley floor, towering peaks like Mount Kilimanjaro and Mount Kenya were created by this activity. The EARS remains one of the largest seismically active rift systems on the planet, with earthquakes and ongoing volcanism continuing to reshape the eastern portion of the continent.
The High Plateau Continent
Africa is commonly referred to as the “Plateau Continent” because its interior is dominated by uplifted blocks of ancient crust, rather than low-lying plains. Much of the land sits at a high elevation, dropping off steeply toward the coastlines. This structure is supported by cratons, such as the Congo and Kaapvaal, which are tectonically stable shields of rock forming the continental core.
The edges of these elevated interiors are often marked by massive, steep-sided escarpments. The Drakensberg mountains in Southern Africa are a prime example, representing the Great Escarpment that defines the boundary between the high central plateau and the narrow coastal plain. Large-scale domal uplift, driven by forces deep within the Earth’s mantle, created features like the Ethiopian Highlands. This massive region is an uplifted shield that contributes significantly to the continent’s overall high relief.
Africa’s Vast Arid Zones
The continent contains immense deserts that are landforms shaped primarily by climate and erosion. The Sahara Desert, the world’s largest hot desert, covers nearly a third of the continent’s northern portion. Contrary to popular belief, the Sahara is not primarily a landscape of towering sand dunes, but is largely composed of hamadas, which are barren, rocky plateaus and stone-covered plains.
The great sand seas, known as ergs, are massive dune fields, but they constitute only a fraction of the desert’s total area. The dunes within these ergs are often monumental, with some reaching heights exceeding 180 meters. In contrast, the Namib Desert along the southwestern coast is created by the cold Benguela Current flowing northward from the Antarctic. This current cools the air above the Atlantic Ocean, suppressing the formation of rain clouds and resulting in a desert that receives minimal rainfall, though it is often shrouded in coastal fog.
Defining River Basins
Africa’s major river systems structure the landscape through their drainage basins and flow characteristics. The Nile River, historically recognized as the world’s longest, is an exotic river, meaning it flows through arid lands but draws most of its water from distant, humid regions. The river’s flow is heavily dependent on the Ethiopian Highlands, which supply approximately 84 percent of its water volume measured at Aswan.
The Congo River Basin forms a vast, low-lying sedimentary depression within the ancient Congo Craton. This basin contains the world’s second-largest tropical rainforest by area, linked to the river’s immense volume. The Congo is the world’s second-most voluminous river, but its utility for navigation is limited by a series of rapids and waterfalls that fragment the waterway, preventing a seamless connection to the Atlantic Ocean.