Churning deep beneath the Earth’s surface, the awesome power of tectonic pressure is hard to conceive, but its influence is everywhere to see. Across hundreds of millions of years, these incredible geological forces have crafted our landscapes, creating towering mountains, deep rift valleys, and expansive plateaus where extraordinary ecosystems have evolved. They have also forged invaluable materials that humans have utilized, adapted, and treasured—from malleable metals to precious stones. In southern Africa’s Okavango River Basin, this incredible dynamism of pressure and time has combined to create two of the most beautiful and unique phenomena on the planet—diamonds and the Okavango Delta, the “Jewel of the Kalahari.”
There is a reason diamonds are unique: They are the result of extraordinary serendipity. A diamond is a pure, crystalline form of carbon—the building block of life on Earth. In some cases, carbon circulates in the fiery mantle beneath the Earth’s crust where, when pressure and temperature are just right, it can crystallize into a diamond. But the tremendous 45,000 to 60,000 atmospheric pressures this transformation needs normally occur more than 85 miles beneath the surface, where it’s too hot for diamonds to form. However, in unusual tectonic regions beneath the most ancient continental crust, known as archaean cratons, the pressure in the mantle is high enough, but temperature cool enough (a mere 1200°C (2192°F)) for carbon to transform into diamonds. And there they would stay, buried beyond human reach, but for another tectonic phenomenon.
On sporadic occasions over the last billion years, parts of the Earth experienced deep-rooted volcanic eruptions where small but aggressive magma surges exploded to the planet’s surface. Some of these happened to pass through the diamondiferous pockets of mantle—carrying the diamonds with them. However, to survive as diamonds they had to travel up to 19 miles an hour—incredibly fast when moving through solid rock—needing to reach the surface before the lower pressure allowed the atoms to rearrange themselves into graphite, the low-pressure form of carbon. When the magma neared the surface, some of it erupted explosively to form a volcanic crater, beneath which the rest cooled into a column of bluish-green igneous rock. This is called a kimberlite pipe. Of the approximately 6,400 kimberlites clustered across the globe, only 15 percent carried diamonds to the surface, and barely 60 are viable to mine.
Southern Africa is endowed with a concentration of kimberlites. Like the formation of diamonds and the eruption of diamond-bearing kimberlites, the emergence of Africa’s present-day landscape owes much to the profound tectonic forces at play beneath the Earth’s surface. For around the same time that Orapa, one of Africa’s richest kimberlites, erupted in Botswana, massive tectonic shifts started to forge another astounding and beautiful phenomenon—the formation of the Okavango Delta.
Like tectonic pressures, geological time is immense. The continent of Africa split from the ancient supercontinent of Gondwana over a hundred million years ago. For the next 40 million years, while dinosaurs roamed the planet, the area that now includes Botswana was wracked by tectonic events as the landscape warped and arched to begin forming what is now the Okavango Basin. Around 65 million years ago, the region’s arid climate eroded rocks into sand that formed the Kalahari Desert. And after that time, a deep upwelling of magma lifted a domelike area into what is now the Angolan Highlands—the water source that sustains southern Africa.
For good reason, local tradition describes the Angolan Highlands as Lisima Lya Mwono, meaning “Source of Life.” For millions of years, rivers flowed from the rainy Highlands into the Okavango River Basin, their courses shifting with the geological rising, falling, and reshaping of the landscape. Five million years ago, about 4.7 million years before Homo sapiens appeared, three mighty rivers flowed into a depression in the Okavango River Basin, where the water pooled into a vast Paleolithic lake—Lake Makgadikgadi. Then, tectonic forces changed everything again.
Northern Botswana has a series of deep fault lines, the continuation of the East African Rift through southern Africa. At certain times over the last two million years, seismic shifts diverted the flow of the rivers eastwards away from Lake Makgadikgadi, which dried up to leave the vast salt pans visible today. But water continued to flow from the Highlands, and its new course carried it into the Kalahari Desert. Here, a tectonic trough, the extension of the East African Rift, formed a basin and the waters fanned out to form the Okavango Delta.
The result is a geomorphological anomaly: A rare inland delta whose rivers never reach the sea. And its waters are unusually fresh. The Angolan rains that fall in the Highlands and feed the Delta are filtered as they flow downhill through papyrus, peat, and sand, giving exceptional purity. And just enough water escapes the Delta to avoid its salination, the fate of Lake Makgadikgadi. These serendipitous circumstances created the unique, pristine habitat of freshwater marshes, channels, and lagoons that is now home to remarkable biodiversity. Alongside crocodile, buffalo, zebra, hippo, and an abundance of birdlife, it is also a haven for endangered cheetah, lion, white and black rhinoceros, and the world’s largest population of elephant—making the Okavango Delta crucial to the survival of the species.
But the survival of the Delta depends on the source waters that feed it—and these are at risk. Increasing population, development, water diversion, commercial agriculture, and climate change are impacting the unprotected Highlands, threatening the flow of its waters into the Delta and endangering the biodiversity that thrives here. But in an elegant symbolism, one remarkable geological phenomenon is helping to protect the other. The region’s diamonds are helping to support the preservation of the Delta’s source waters in Angola, along with their rivers through Namibia into Botswana.
Leading diamond company De Beers has joined with National Geographic through Okavango Eternal. The Okavango Eternal partnership is working to preserve and protect the source waters of the Okavango Delta, from the Angolan Highlands, through Namibia, and into Botswana. Together, De Beers and National Geographic are working with local communities to protect wildlife and build sustainable livelihoods across the region, funding research and education in Angola, Namibia, and Botswana. They are also mapping and monitoring the area around the source waters to better understand the system, an important prerequisite for securing formal protection.
Diamonds and the Okavango Delta share a powerful bond. Their stories are deeply entwined in the astonishing geological journey that has forged southern Africa’s landscape, and both owe their beauty to enormous tectonic pressures over immense spans of time. Through Okavango Eternal, this shared history becomes part of a new effort to protect one of the planet’s most extraordinary habitats, ensuring that the wildlife and people of the Okavango can continue to thrive.
Find out how De Beers creates positive impacts here.
