The highlands in the Namibian interior were formed 128 million years ago when structural shifts in the crust of the earth raised the outer rim of southern Africa. Their great age as a physical feature notwithstanding, they are for the most part made of even older rock, the remnants of earlier mountains that originated before terrestrial life evolved on earth.
The atmosphere at that time was thin and poisonous. Solar radiation beat down day in and day out. The earth was bare, devoid of vegetation. Not a blade of grass grew upon it. No animals of any kind, not even insects, moved upon its surface. No birds flew in the sky. Confined to the seas, the only forms of life were bacteria, algae and plankton.
The earlier mountains were built as a number cratons or land masses in primitive seas converged and ultimately collided to form the Gondwana supercontinent 550 million years ago. They formed under immense stress wherever the margins of cratons met. Sediments on the seabeds were simultaneously changed to rock and squeezed out of the water to become part and parcel of the mountains.
The land that would become Namibia lay at the junction of three cratons. It straddled a diagonal belt where two cratons had joined together to form part of the African continent, while lengthwise it was attached to South America in the west. Apart from Africa and South America, Gondwana consisted of the future Antarctica, Arabian Peninsula, Australia, India, Iran and Madagascar.
Mountains would not be built again in Namibia for 420 million years after the formation of Gondwana. In the interim life forms on earth would diversify and multiply in the sea and on land. Remote ancestors of vertebrates such as fishes, reptiles, birds and mammals would appear and begin to evolve. The animal and plant kingdoms would colonise the planet.
Reptiles were the dominant form of animal life when mountains were next formed. Gargantuan dinosaurs still walked the earth, while lizardlike pterosaurs with wings that stretched 6 m across flew in the air. Mammals were primitive, none bigger than a rat.
Subjected for aeons to erosion, the earlier mountains had been levelled, or greatly reduced in size. Nevertheless their remnants were substantial enough to give body to the highlands when tectonic forces tore Gondwana apart and uplifted the Namibian interior.
The Khomas Hochland with its rolling hills of schist, located in the centre of Namibia around Windhoek, was once an extensive tract of mountainland. Now a mere stump of the original, it nevertheless is the highest part of the highlands, with altitudes that generally range between 1 700 and 2 000m above sea level.
The limestone-and-dolomite bulk of the Naukluft, a mountain range in the southern part of the Namibian escarpment with an area of 2 100km² and a height of 1 966m, actually originated in another place altogether. Dislodged and sent sliding when Gondwana was formed, it finally came to rest about 120km away in its present position.
Granite and basalt mountains in the northern half of the highlands arose from volcanic activity that presaged the disintegration of Gondwana.
The earth opened up in Namibia before southern Africa parted from South America 132-128 million years ago. Near the coast in the north-west magma gushed out of deep rifts in the continental crust. It buried low-lying land north of the Huab rivercourse -- now named the Etendeka Plateau -- under lava to a depth of 2km over an area of 78 000km².
Elsewhere in Namibia volcanoes erupted as the continents parted. They formed a broad belt of fire that ran far inland from the coast, from a point near present-day Cape Cross to the town of Grootfontein, along a fault line where two cratons had merged long before. The fires would burn on and off for five million years.
The volcanic mountains grew ever bigger on foundations of their own lava until they finally caved in under their own weight. As erosion wore the lava away in the course of geological time, granite plutons or inselbergs emerged from the rubble, where volcanoes had previously dominated the horizons.
Formed underground from molten granite that intruded into the volcanic craters and later solidified, a score of inselbergs with a circular structure -- among them the Brandberg, the Erongo massif and the Spitzkoppe -- remain today on a great peneplain, between the Kuiseb and Huab rivercourses, that extends into the highlands from the inner Namib.
A flat-topped inselberg that is much older than the others stands alone in the escarpment on the edge of the Khomas Hochland. The 2 349m Gamsberg consists of pink granite with a quartz plateau. An erosion relic of a pluton that was formed even before Gondwana came to exist, it is 1 100 million years old or about a quarter of the age of the earth.
When at last the highlands were uplifted, mountains of a quite different kind also appeared, neither out of volcanoes nor the sea.
One of them is the 1 885m Waterberg near Otjiwarongo. The bulk of the mountain consists of red sandstone derived from a desert that once covered much of Gondwana. Its mesalike cliffs rest on a basement of older rocks, formed much earlier in the aftermath of an ice age, from sediments deposited in a glacial lake.
The desert that once prevailed on Gondwana is long gone, its red sands carried away on wind and water. Of its few relics in Namibia, the Waterberg remains only because its sandstone escaped the worst ravages of erosion under cover of harder rock, thrust over it during uplift.