The Geography of KwaZulu-Natal
The Geography of KwaZulu-Natal
Before and After Gondwanaland
Geo-scientific circles generally agree that the continents of today’s world only began acquiring any semblance of their present outlines and locations some 300 million years ago. Prior to that, all were subsumed within a single giant super-continent named Pangaea – from the Greek for ‘All Earth’ – with the remainder of the globe covered by ocean.
Pangaea’s foundation rocks - known as ‘The Basement’ and clearly visible in KwaZulu-Natal’s deepest river valleys - were, according to radio-active dating, laid down some 1100 million years ago. These are crystalline granites, gneisses (laminated quartz, feldspar and mica) and schists (foliated rock presenting layers of different minerals split into thin, irregular plates) that reformed from pre- existing crustal rocks many kilometres below the surface. Under pressures of hundreds of atmospheres and at temperatures of between 400 and 800 degrees Centigrade, the original chemical elements recombined into new minerals such as those just mentioned, plus the calcium, magnesium and iron silicates known as hornblende that form a primary constituent of granite. All are now found as separate, easily identifiable crystals averaging 5mm in length but reaching a maximum size of some 25mm.
During their transformation these materials often created intricately contorted rock structures, while those subjected to ‘superheating’ turned molten, resulting in large masses of granite with uniform crystals or seeping as veins into adjacent rock structures.
Formation of The Basement was followed, some 430 million years ago, by the Paleozoic Era which consisted of the Silurian, Devonian, Carboniferous and Permian geological periods. These, in turn, ushered in the Karoo System, which comprised the Dwyka, Ecca, Beaufort and Stormberg Series of geological change.
Increasingly weighed down by cataclysmic outpourings from the earth’s molten core, the ancestral super- continent split in two along the equator some 300 million years ago. The northern half, named Laurasia, contained the embryonic continents of today’s Northern Hemisphere, while future India, South America, Australia/New Zealand, Africa and Antarctica lay within the southern half – Gondwanaland.
The ‘new’ southern proto-continent itself began to segment 75 million years later, under pressure from further deposits of lava plus erosion debris moving towards its centre from the mountainous outer rim. Within this ring had already lain vast basins of mud and sand, each thousands of metres thick and which, solidified, today appear as sedimentary shales and sandstones in all southern continents. These sediments were overlaid with yet more hundreds of metres of basaltic lava and erosion deposits, heralding the imminent segmentation of Gondwanaland. This separation occurred during the Mesozoic Era that incorporated both the Triassic and Jurassic periods. It was the latter that witnessed the completion of Gondwanaland’s primary division - into two halves longitudinally and begun in the south by the Prince Edward Fracture Zone. This progressed north until the split reached finality with the Owen Fracture Zone off what is now the Eastern Horn of Africa. Further fragmentation was followed by the dispersion known as continental drift. These processes saw Gondwanaland’s mountainous outer rim become the ancient peaks of Antarctica, the chains of Australia and New Zealand, Atlas range of Africa, the Indian subcontinent’s Himalayas and South America’s Andes. The marked geological similarity between all these and Northern Hemisphere ranges such as the American Rockies primarily led scientists to discover that all were once part of the ‘fundamental’ Pangaea super-continent.
When Gondwanaland began to segment, our future province lay within the just described seething centre, and came into being during the Lower Cretaceous Period around 100 million years ago, courtesy of the Falklands-Agulhas Fracture Zone. This developed at the opening of the South Atlantic Basin, just a few hundred kilometres west of the Gondwanaland- breaking Prince Edward Fracture Zone.
Moving north, this new fracture created the eastern seaboard of Southern Africa and left the island of Madagascar protruding up from between the two. Thus, too, was born the new Indian Ocean basin.
Our sub-continental margin was stretched and thinned, causing the Karoo sandstones and lavas of Gondwanaland to flex down towards the new coast, a pivotal development that gave the province its definitive ‘Natal Monocline’ description. The original Karoo sandstones and shales today cover the entire western half of the province, while the dark basaltic lava floods of Gondwanaland form the mountain wall of our westernmost boundary and World Heritage Site – the High Drakensberg range.
Not that any mountain wall existed a hundred million years ago – the smooth, undulating ‘inherited’ landscape was the norm, although it now tilted south-east towards the ocean, carrying even the basalts down below sea level. The volcanic and seawards-leaning Lebombo Mountains of Zululand that stretch southwards from our northeastern borders with Swaziland and Mozambique show fascinating evidence of this phenomenon. Near the town of Empangeni in southern Zululand the earth-changing Natal Monocline clashed with The Basement to squeeze the latter’s granite up above ground level to form the impressive Ngoye Range and Mpemvu Hills.
In southern KwaZulu-Natal, the tilting steepened to the point where the earth ‘broke’ into blocks that eventually slid below the ocean to join the continental shelf originally formed when Gondwanaland had segmented itself. All along the province’s 480km coastal length, erosion acting upon the tilted landscape sent enormous quantities of land waste into the ocean, where it settled on this shelf to create the first series of marine sedimentary rocks. These now underlie Zululand’s coastal plain, and it’s thanks to the fossils they contain that the Natal Monocline’s original bending can be dated at a minimum of a million centuries ago. Add to the ‘earth-blocks’ caused by this dramatic flexing the deep valleys carved out by seaward-heading rivers and streams, and you have the rugged and varied prototype of today’s wonderfully scenic Zulu Kingdom. The flora species of the time were, however, no match for the splendours of today – even grass did not then grow and the highly erosion-prone, dark and inhospitable basaltic soils would barely have been able to hold the roots of whatever scattered plant life tried to establish itself. (Visit our Bush site for an overview of the varied greenery awaiting today’s visitor.)
And this was the Reptilian Age, when dinosaurs and their primitive ilk roamed the earth, evidence of their presence in our part of the world only partly retained due to a relative lack of land-deposited Cretaceous strata in which their remains could have been preserved.
The Great Wall
It was during the middle of said Cretaceous period that the Natal Monocline experienced its first so- called ‘rejuvenation’, the interior uplifted by an estimated 1 200 metres and the sea floor beyond the coastal hinge simultaneously depressed. The most outstanding evidence of this event can today be seen in the Drakensberg although, at the time, the majestic sheer rock faces were yet to be created.
The 80 million or so years between mid-Cretaceous and – Cenzoic eras is known as the ‘Moorland Cycle’, a period of denudation of the aforementioned uplifted terrain. By its end, most of KwaZulu-Natal was reduced to a smooth plain, bounded in the west by the proto-Drakensberg escarpment. Erosion had steadfastly eaten away at its constituent mass from a point beyond the seashore, causing it to ‘retreat’ inland until the definitive great wall of the Drakensberg was left standing. Ironically, the debris caused by this erosion created a fill that effectively reduced the mountain range’s vertical height.
A gentle uplift of some few hundred metres province-wide resumed in Early Miocene time around 20 million years ago, but with the hallmark tilting in evidence only near the coast. This led to the wide development of Rolling Landscape, distinguished from its predecessor by scarps and cliffs of less than a hundred metres in height. Our Valley of a Thousand Hills offers good examples.
Soil erosion slowed as the Miocene period progressed, and the rivers developed widely meandering courses across this Rolling Landscape. The process remains underway in our southern inland region of East Griqualand.
Fourth Active Episode
Towards the Miocene period’s end, the first of two gigantic upheavals affected the province’s entire width, lifting the Midlands region by some 600 metres and further accenting the seaward-tilting Monocline. This led to renewed denudation of the Rolling Landscape and the production of independent basins that remain prominent throughout the Midlands and extending north. Our twin capital and gateway to the Midlands, Pietermaritzburg, is situated in a prime example, as are several of the towns along our equally historic and much-visited Battlefields route.
The sea was pushed back by this activity and gigantic sand dunes formed at the new shoreline. These were then partially reclaimed by the ocean and became spectacular underwater wonderlands. Most popular of these is probably the fossilised sand dune called Aliwal Shoal off Umkomaas, that was joined by an early shipwreck to form one of the world’s premier dive sites. Other much-frequented ‘fossil dives’ include the Trafalgar Marine Reserve along our lower South Coast and locations within our first World Heritage Site, the Greater St Lucia Wetland Park. The latter witnessed, in deep waters at the turn of the New Millennium, the surprise discovery of a coelacanth colony – ‘living fossils’ dating back some 400 million years – that has sparked scientific and tourism interest from around the world.
On the subject of ocean sports, while we may not boast the ‘reef breaks’ that attract globe-trotting surfers to volcanic sites such as Hawaii, our sand formations close to shore have ensured for the South Coast, Durban Metro, the Sugar Coast and Dolphin Coast fine reputations for providing consistent ‘beach breaks’.
Another Monocline Steepening
The second mighty upheaval took place some 2 million years ago at the end of the Pliocene era, with vigorous southeast tilting on the Monocline again affecting the entire province. The northern Drakensberg was lifted to its present height of 3000 metres, increasing the existing seaward tilt and injecting new life into the province’s watercourses. This episode completed the Monocline structure as found today, bestowing upon KwaZulu-Natal its modern elevation. Subsequent changes to the scenery have been the result of erosion, and in the most part witnessed in the major river valleys. Evidence of some ebbing and flowing of the shoreline has been ascribed to minor fluctuations in positioning of the Monocline’s hinge.
The Youngest Landscape
With added impetus bestowed by these two great steepenings, the primary watercourses have since gouged out dramatic valleys. While these are evident throughout the Kingdom, our ‘Waterfall Country’ centred on the National Monument falls at Howick is particularly scenic and a highly popular tourist attraction. So are the coastal lakes of Zululand, that reached their present state during this same era, and whatever reshaping of the KwaZulu-Natal scenery is currently taking place results from the same influence of erosion in the major river valleys. The overall picture leaves many remnants of the ancient surfaces still visible on the uplands and interfluves.
Rock Formations and Scenery
As is already evident, the rock series of KwaZulu-Natal – with the notable exception of the coastal region’s Cretaceous and Cenozoic marine sediments – belong to the ancestral Gondwanaland and are thus older than the province itself. Because the Basement rocks were formed deep within the earth’s crust, their component minerals are often unstable at the surface and prone to rapid decay into clay, sand and grit. Most of the province’s major rivers now have deep infills of these ‘secondary’ substances. While valleys formed by both the Thukela and Mgeni Rivers show well the mineralogy and structure of the Basement, they also clearly evince the deterioration caused by weathering. Along our lower South Coast, the Oribi Gorge is a world-famous abseiling site carved through the Basement granites. It is also well known for its white marble –. the marble is older than these granites and intruded by them, giving birth to several new minerals under the effects of heat and pressure, and in certain instances affording the marble itself delicate blue and green hues. A particularly dark and hardy type of granite lines the shore at our southernmost resort of Port Edward, while a little further north, the International Blue Flag status seaside town of Margate boasts a mass of red granite at the water’s edge.
Apart from coal – mined predominantly in the northern regions of our historic Battlefields – most of our Kingdom’s somewhat meagre mineral deposits are found in the Basement rocks. Gold, asbestos, chromite, galena, vanadium and iron ore have all been won in small quantities in Zululand. These were mainly the efforts of mid-19th Century settlers from Britain and Europe, although the first black tribes to arrive from the Great Lakes of Central Africa brought with them limited Iron Age skills. The last attempt to mine gold in Zululand was during the mid-1940s.
Dune mining continues there around the port city of Richards Bay and nearby town of Empangeni, and a comprehensive visitors programme run by Richards Bay Minerals provides a fascinating overview of the unique dune mining process plus subsequent rehabilitation of exploited areas. The annual 2 million tonnes of titanium, ilmenite, high purity pig iron, rutile and zircon from this region satisfies a large proportion of global demands for these particular heavy metals.
As already stated, the Basement rocks with their contorted, east-west structures are exposed mainly within the deep valleys of major watercourses. The overlying systems, on the other hand, are sub-horizontal in the west – in line with how they were deposited - and tilting seaward in the east as determined by the slope of the Natal Monocline.