E. Escarpment, S. Africa

In March of 2023, I had the opportunity to trek and explore the “Panorama Route” of South Africa. The “Panorama Route” in South Africa is a 160 km stretch of road that lies in the province of Mpumalanga and is surrounded by the Drakensberg Mountain Range.

A google map of the general location of the Panoramic Route in South Africa.

The most popular stretch of the route is the R532 that winds its way from the town of Sabie (370 km east from Johannesburg) via the “Three Rodavels, Bourke’s Luck Potholes and the Blyde River Canyon.

Google Earth Map of the Panorama Route of South Africa and the places we visited.

One of the country’s most scenic self-drives, the “Panorama Route”, explores the north-eastern section of “The Great Escarpment”. In these rugged mountains (the Drakensburg) the “Bushveld Plateau” comes to an abrupt and dramatic halt, falling steeply away into the Lowveld accompanied by incredible views out over the grasslands and Kruger National Park of Africa.

A public domain image of the generalized geographical areas of South Africa. (The black and red line depicts “The Great Escarpment”).

South Africa is renowned for its magnificent landscapes and much of the spectacular scenery can be traced back to the break-up of the Gondwana supercontinent, which started more than 140 million years ago. This resulted in large-scale rifting of the continental margins, the creation of new oceans, uplift of southern Africa, down-cutting by coastal rivers and massive denudation. The uplift is due to large-scale vertical uplift (or epeirogenesis) that has for millions of years buoyed up the subcontinent, the cause of which is thought to be from anomalously hot conditions deep within the underlying mantle (imaged below). This phenomenon is known as the Africa Super Swell, which is essentially a massive long-lived mantle plume (imaged below).

Image of the Epeirogenesis process on the earth, (image taken from C.Cramez, adapted from http://www.gercities.com/CapCanaveral/)

Following marginal rifting, the break-up of Gondwana and the creation of new coastlines, erosion on a vast scale resulted in the formation of new coastal plans that were separated from the high, slightly westward-sloping interior plateau by the rugged Great Escarpment that wraps right around southern Africa.

Public domain image of the Great Escarpment in South Africa.

Some 20-5 million years ago southern Africa again experienced periods of considerable continental uplift, up to 1,200m in the east, but much less in the west. These uplifts increased the elevation of the “Great Eastern Escarpment”, which led to large-scale marginal erosion and cut down deep valleys and gorges along the eastern and southern coastal plains.

Image focused on the rise of south-east Africa with the uplift and erosion of a dome and the development of the continental margin. Sedimentary layers taken out.

The coastal Great Escarpment of Southeastern Africa likely was rapidly eroded from near the coast toward the interior, as the Floodwater was running more perpendicular off the uplifting large dome and towards the
oceans. Erosion did not form a second escarpment west of the rising dome
likely because of the slower water movement caused by much less differential vertical motion in the interior of southern Africa. The erosion of the Great Escarpment caused the erosion of the African Surface from near the coast to its present location and formed a coastal plain, (imaged below).

Image of the erosion of the Great Escarpment in Southeast Africa.
The escarpment erodes to the left as sediments continue to pile up on the
continental margin. Eventually, the Great Escarpment separates the high African Surface from a coastal plain.

During the Cretaceous, the wetter tropical climate created the ideal situation for weathering, erosion and removal of material by many youthful, eastward-flowing rivers that cut back into the newly formed coastal scarp. The result was the geologically rapid retreat of the scarp across the coastal plain, a forerunner of today’s Great Eastern Escarpment. The earlier coverings of Karoo and Transvall sequences have long since been removed by erosion.

Abel Erasmuspas on the northern end of the “Great Eastern Escarpment” from R36 in South Africa 2023.

On our way from Tzaneen to Nelspruit, our first walking-trek was to explore the Kadishi Tufa Falls within northern end the “Great Eastern Escarpment” on R36. The Kadishi Tufa Falls was near the Blyde Dam and considered one of the largest tufa falls in the world. Once we passed the Abel Erasmuspas pass on R36, we turned off onto the Forever Resort road. The Kadishi Tufa Falls is on the Forever Resort property, (pictured below).

Forever Resort map of the Kadishi Tufa Falls location.
I’m beginning a hike down to the Kadishi Tufa Falls at the Forever Resorts Restaurant Parking Lot in 2023.

The “Kadishi Tufa Falls” trail winds itself through a forested, lively canyon through quartz arenite cliffs of the Black Reef Quartzite Formation and Wolkberg Group – some 2.5 – 2.6 billion years old rocks, (pictured below).

My trekking buddy, Mike Stevens, hiking down the Kadishi Tufa Falls trail in South Africa 2023. Looking East
Looking west down the Kadishi River Canyon on the “Great Eastern Escarpment” in South Africa 2023.

A Tufa Waterfall is created when water running over dolomite rock absorbs calcium, and becomes supersaturated with calcite. Supersaturation typically occurs at a waterfall, when the water is highly aerated, has an accelerated flow velocity, and an enlargement of the air/water interface area. This accelerates the release of carbon dioxide, which promotes calcite precipitation. It is believed that algae and mosses, which grow abundantly on the porous tufa deposits, assist with the removal of carbon dioxide, and also create the necessary substrate to trap the calcite precipitation.

The lake behind the Kadishi Tufa Dam in 2023.
The lake behind the Kadishi Tufa Dam in 2023.

Pictured above, the Kadishi River, before its fall into Blyde (Motlatse) Canyon, flows through dolomite layers above. Over many thousands of years, the water of Kadishi dissolved the lime in the dolomite. When the water with lime reached the rim of the canyon and fell through the air, the lime was deposited over thousands of years and had formed a weird tufa cliff and dam.

I’m standing near the swimming hole found at the bottom of Kadishi Falls in South Africa 2023.

Dominated by dramatic granite ridges, the 24 km long Blyde (Motlatse) River Canyon cuts through the “Great Eastern Escarpment”, and winds its way to the Blydepoort Dam at Swadini. At one time the waters of the Blyde (Motlatse) River blasted through the rock, carving a 800 meter deep canyon, (the third largest in the world), and one of the most beautiful landscapes in Africa.

Looking east from the Blyde (Motlatse) Canyon Viewpoint, off of R532, south of the Kadisha Tufa Falls turn-off at the Forever Resort, in South Africa 2023.

Pictured above, today the Blyde (Motlatse) River threads through canyon-sides cloaked in temperate rainforest and evergreen shrub-like plants known as fynbos. On one side stands the Three Rondavels, three enormous spirals of dolomite rock, that rise out of the canyon walls like giant space rockets. Their tops are iced with the green of vegetation and their sides stained with the orange of lichens. [They get their local name from a similarity to the circular thatched huts common to indigenous peoples.] (Pictured below).

The 3 Rondavels over the Blyde (Motlatse) River on the “Great Eastern Escarpment” in South Africa 2023.

Pictured above, this is the easternmost part of the Transvaal Basin, a depository that started to form around 2.7 billion years ago. At the top of the dissected plateau the formation immediately underlying the surface is mostly mapped as the 2.65 billion year old Black Reef Formation, deposited blanket-like on the sedimentary formations stratigraphically underlying and preceding the Transvaal Supergroup. The older, underlying strata are of the precursor basin of the Wolkberg Group, comprising mostly alternating layers of quartzite and shale, here at their thickest and magnificently exposed in the walls of the canyon. [All formations dip very slightly to the west, as can be seen on the flat-topped mountains across the canyon].

Interpretive sign found at Bourke’s Luck Potholes, south of the Blyde (Motlatse) River overlook on R532 in South Africa 2023.

The Blyde (Motlatse) River and the Treur River meet at Bourke’s Luck Potholes. Here the Treur is channeled into a narrow cataract that turns almost 900 into the Blyde (Motlatse) River.

Looking northeast at the Blyde (Motlatse) & Truer River Gorge at Bourke’s Luck Potholes within the “Great Eastern Escarpment” of South Africa 2023.

Pictured below, there is good evidence that here the north-northeast direction of the Blyde (Motlatse) River is controlled by a probable fault zone in the flat-lying rock strata.

Looking southwest at the Blyde (Motlatse) River Gorge at Bourke’s Luck Potholes within the “Great Eastern Escarpment” of South Africa 2023. [Note the straightness of the river suggests that its course is the result of a linear geological fault-structure].

Pictured above, the abrupt change of direction in the Treur River causes the swirling water, and the boulders it carries from the hills upstream, to carve out a series of huge, bowl-shaped depressions or “potholes” up to 6 meters deep in the soft red and yellow colored dolomite rock.

Bourke’s Potholes on the “Great Eastern Escarpment” in South Africa 2023.

Under precisely the right-conditions, potholes can form in rivers when the debris, (small boulders pebbles and sand), being transported by the current wears away the rocky river floor in a process of abrasion. Loose material becomes trapped temporarily in bedrock-hollows and is rapidly swirled around by eddies in the fast-flowing water. The hollows gradually grow wider and deeper, and the loose rocks can drill down several meters to produce large cylindrical potholes. Adjacent potholes eventually overlap and merge, (pictured below).

Bourke’s Potholes on the “Great Eastern Escarpment” in South Africa 2023.

At one time a farmer called Tom Bourke owned the site. He speculated that as prospectors upstream upstream were successfully panning for gold, he should find gold nuggets in his potholes. He was right, and the feature became known a Bourke’s Luck. Gold was later found in sulfide-rich secondary-hydrothermal veins within fractures in the quartzite, close to a north-trending dyke. Nearby Bourke’s Luck gold mine closed down only in 1955, having produced 4.5 tons of gold from a number of spread-out workings, plus by-product copper.

Video of Bourke’s Luck Potholes on the “Great Eastern Escarpment” within South Africa 2023.

The setting here at Bourke’s Luck Potholes is part of the “Great Eastern Escarpment”, showing the eastern part of the large Transvaal Basin. Here, the underlying formation is the Black Reef Formation, which does not exceed a thickness of a few meters. It forms the basal unit of the Transvaal Supergroup and is around 2.65 billion years old. The Black Reef itself lies upon much thicker quartzites of the upper part of the slight older Wolkberg Group, which formed under similar depositional conditions.

Bourke’s Potholes on the “Great Eastern Escarpment” in South Africa 2023.

In 1840, a party of Boer pioneers explored the area, looking for places to settle. The men struck out to the east leaving their women and children encamped beside a river. When they failed to return on the arranged date the women thought their men had died and they called the river Treur, meaning “river of sorrow”. Later, however, husbands and families were reunited at a second river and they called it Blyde, meaning “river of joy”. However, the Blyde has been renamed the Motlatse River because of the 300 km2 surrounding nature reserve proclaimed in 1965 called the “Motlatse Canyon Provincial Nature Reserve.

The Treur River as it cascades into the Blyde (Motlatse) River before reaching Bourke’s Luck Potholes within the “Great Eastern Escarpment” in South Africa 2023.
The Treur River as it cascades into the Blyde (Motlatse) River before reaching Bourke’s Luck Potholes within the “Great Eastern Escarpment” in South Africa 2023, {There is an old mine remnants in the distant background}. Looking southwest.

A landscape of weirdly eroded pillars of quartzite is not uncommon in the area, created by preferential rock weathering and different rates of erosion, and this is certainly influenced by the pattern of rock jointing and assisted by the pattern of rock jointing and assisted by the higher rainfall along the escarpment edge.

Strangely eroded pillars nearby Bourke’s Luck Potholes on the “Great Eastern Escarpment” in South Africa 2023.

Around 2.65 billion years ago, rifting and stretching of the Kaapvaal Craton, followed by subsidence, resulted in the development of the Transvaal Basin, (a major elongated depository, which can now be traced for over 500 km east-west and some 200 km north-south). This basin filled with the large, shallow Transvaal Sea and sedimentation on the submerged continent took place under fairly stable conditions until around 2.1 billion years ago.

Strangely eroded rocks of the Black Reef Formation, nearby Bourke’s Luck Potholes on the “Great Eastern Escarpment” in South Africa 2023.

Pictured above, this thin, hard quartzite Black Reef formation, almost horizontal in attitude, blankets the landscape of the “Great Eastern Escarpment” . It was deposited on the floor of the inland Transvaal Sea as a clean, pebbly sandstone less the 2.65 billion years ago. It formed a covering that long resisted strong erosion, and protected the underlying softer Basement graite-gneiss and Wolkberg rocks.

“Looking east across the “Lowveld” from the Wonder View R532 on the “Great Eastern Escarpment” in South Africa 2023.

Later, we drove further south on R36 along the “Great Eastern Escarpment” to the R532 turnoff. Pictured above, we stopped at the “Wonder Viewpoint” to look across the “Lowveld” towards Kruger National Park. This almost unrivalled view-site reaches 1,700 m, the total drop to the Eastern Lowveld far below is around 800 m.

South of “God’s Window” R532 of the “Great Eastern Escarpment” in South Africa 2023.

Pictured above, the “Great Eastern Escarpment” is one of the world’s most impressive landscapes, and God’s Window is one of its highest points, (1,730 meters). The underlying, almost horizontal and well-bedded quartzite is geologically mapped as being the upper Wolkberg Formation. This sequence was the first to form of the Transvaal Supergroup, deposited within a smaller proto-basin (2.7 billion years ago), and it is exceptionally well show-cased at the God’s Window, under the Black Reef Formation.

Entrance sign to the Sudwala Caves within the “Great Eastern Escarpment” near and just northwest of Nelspruit, South Africa 2023.

As we approached Nelspruit (34 km) from the north on R539, we stopped and explored the Sudwala Caves. The caves are found within a rugged dolomite hillside known as Mankelexele. The caves are located on the farm Sudwalaskraal, hidden by dense woodland in the valley of the Houtbosloop, (a tributary of the Crocodile River).

Google map of the Sudwala Cave location near Nelspruit, South Africa

The cave system has developed within the Oaktree Formation, the lowermost dolomite formation of the Malmani Subgroup, which lies immediately above the Black Reef Formation. The Malmani dolomite (or dolostone), deposited around 2.5 billion years ago, is within the lower part of the Transvaal Supergroup, a thick sequence of mostly sedimentary rocks that were deposited within the Transvaal Sea on the continental basement.

Aragonite formations found inside the Sudwala Caves in the “Great Eastern Escarpment” South Africa 2023.

As mentioned, the predominant rock in the area is dolomite which formed in the bed of a shallow sea 2.5 billion years ago. [Dolomite, (a variety of limestone), consisting mainly of calcium-magnesium carbonate (CaMg(CO3)2). Another name for this is ‘dolostone’]. The Sudwala Caves, aragonite crystal chambers were about 2 km from the cave entrance and were formed about 450 million years ago, while the caves were still filled with water and remained undisturbed for millions of years. Around 400 million years ago due to movements in the earth’s crust, the ancient sea-beds were tilted, and the sea water swept away. The main section of the Sudwala Caves was created by slightly acidic groundwater, seeping down, and dissolving the dolomite to form cavities beneath the water table. Around 250 million years ago, the water table dropped and the caves became air-filled in which stalactites and stalagmites could form.

The elephant skin of dolomite in the Sudwala Caves in South Africa 2023

The local name for this ‘Dolomite’ rock in the Sudwala Caves is “Elephant-skin” rock as it has the light grey wrinkled texture of an elephants skin. As mentioned above, this dolomite is a sedimentary rock formed 2.5 billion years ago in the Pre-Cambrian time period when the lowveld area was covered by warm shallow inland seas. At that time the only life that existed on earth were primitive algae plants. Fossilized remains of these plants are called stromatolites, and can be seen throughout the caves.

The Lowveld Rocket in the Sudwala Caves, South Africa 2023.

Pictured above, the “Lowveld Rocket is 14 m high and 2.5 meters in diameter. It is approximately 150 million years old. This calcium formation is a pillar. A stalactite from above and a stalagmite from below. Once the two dripstones met, they were called a pillar and water runs down on the outside without dripping. It is still active during the wet seasons. At the top, you could see the black soot marks remaining from the attempts by Mswati, the rightful heir to the Swazi throne, to smoke out his half brother Somcuba and his followers in the 1800’s. These attempts were futile because the natural fresh airflow in the caves blew the smoke out.

My trekking buddy, Mike Stevens, striking Somcuba’s Gong with a rubber-mallet inside the Sudwala Cave, South Africa 2023

Pictured above, Somcuba’s Gong is a flowstone formation named after Chief Somcuba of the Swazi people, who together with his followers used the caves as a refuge in the 1800’s. This formation is porous and when hit produces a hollow sound which can be heard throughout the cave.

The ceiling of the Sudwala Caves in South Africa 2023.

Pictured above, on the ceiling of the cave, you can see the magnum ice-cream formation. This flowstone has a chocolate brown color on it, caused by staining from the mineral, manganese. Bat Guano is a very valuable fertilizer which the prospectors excavated about 2000 tons from the Sudwala Caves throughout the 1900’s and sold to farmers in the Crocodile Valley.

The “Three Praying Nuns” within the Sudwala Caves, South Africa 2023.

Pictured above, the “Three Praying Nuns” formation is only a stalagmite. The water drips too fast for a stalactite to form on the ceiling. For a stalactite to form, the drop of water must remain for several hours before it drops, giving the water time to evaporate leaving behind calcium. These three nuns have been praying for about 40 million years.

The “Screaming Monster” formation within the Sudwala Caves in South Africa 2023.

Pictured above, the “Screaming Monster” formations are also called speleothems taken from the Greek for cave deposit. The formation consists of a combination of Stalactite, (pointed pendant growing from the ceiling), Stalagmite, (counterpart of a stalactite growing from the ground up), and Flowstone, (sheet like layering). To age the formation, scientists drill a small diameter core near the base of the stalagmite. These samples are then dated using uranium-thorium dating.

Lot and Lot’s Wife formations within the Sudwala Caves at South Africa 2023.

Pictured above, these two stalagmites are known as “Lot and Lot’s wife. Lot is an active formation in winter when water drips slowly enough to deposit calcium. In summer, during the rainy season the water flows too quickly and “Lot” is slowly eroded away. Lot’s wife on the other hand is like a pillar of salt and has not been active for a long time.

The “Dental Care Corner” in Sudwala Cave, South Africa 2023.

Pictured above, the “Dental Care Corner” are a group of stalactites and stalagmites that look like teeth. A natural airflow circulates through the cave, keeping the temperature at a constant 17-18 degrees Celsius, all year round. Although the Sudwala Caves are not the biggest caves in the world, they are thought to be the oldest known dolomite caves in the world. Additionally, the Sudwala Caves have approximately 6 km of explored passages, (explored and mapped in the 1970’s).

The “Devils Workshop” within the Sudwala Caves, South Africa 2023.

Pictured above, this area is called the “Devils Workshop” because it is warmer than the rest of the cave as all the hot air rises up here. It is about 24 degrees Celsius. The humidity is 100%. This formation with the red light is known as “Old Nick”, the cave Devil. Nick is a fallen stalactite. He fell a very long time ago and when he fell he tumbled and landed upside down. He is still active and growing, depending on the amount of rain we receive. {You are looking just at his head upside down. The dark spot in the center is his eye. His ear is to the left and his long nose to the right. His mouth is the dark area at the top and at the very top is his point chin}.

Fossilized Stromatolites in the Sudwala Caves, South Africa 2023.

Pictured above, on the roof, we could see the round shapes of fossilized stromatolites. These are fossils of the first oxygen-producing plants on the earth. Fossilized stromatolites are the oldest evidence for life on Earth and grew in the Lowveld area around 2.5 billion years ago when the Lowveld was covered by warm shallow seas. These cyanobacteria or blue green algae were the first oxygen producing plants which helped to create the atmosphere we have today. It is calculated that one centimeter of stromatolite takes around 25 years to form.

The “Weeping Madonna” within Sudwala Caves, South Africa 2023.

Pictured above, the “Weeping Madonna” is a flowstone formation. Flowstones are formed from a build-up of calcium deposits as a result of slow flowing water. This is different to drip formations. If the waterflow is too fast, the calcium is eroded away instead of being deposited. This continuous erosion could mean a formation like the “Weeping Madonna” could eventually disappear completely.

“Samson’s Pillar” within the Sudwalla Caves, South Africa 2023.

Pictured above, Samson’s Pillar is the highest point in the cave, approximately 60 m below the surface. “Samson’s Pillar” is the oldest formation in the cave. It is about 180 million years old. It is made up of a large stalagmite and only a small stalactite.

Fairy Land within the Sudwala Cave, South Africa 2023.

Sudwala Caves is a dissected remnant of that which existed before the break-up of Gondwana. The once overlying Pretoria Group rocks have been removed and valleys have cut down through the Malmani dolomite and Black Reef quartzite, exposing the underlying Archaean granitic basement nearby. The residual massif of dolomite is crossed by north-trending linear structures, probably faults and dikes, which have allowed surface water to penetrate and erode along points and fractures.

This surrounding landscape reflects dissected terrain of the Crocodile River catchment, eroding back strongly along the “Great Eastern Escarpment”, and separating Mpumalanga’s Lowveld from the Highveld plains.

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