BLAST Vredefort Dome Tours

04/09/2026

AMAZING REBIRTH OF A TREE
Four days from dormant to flourishing

An absolutely stunning transformation took place in the great old oak tree on our lawn during the past week. On Monday it was completely bare after winter. By Friday it was in full green leaf. This year the oak has - most unusually - beaten the willows at the river to put on spring garb.

We live beside the Vaal River on the Highveld of South Africa which is cold and very dry in winter. The season we have just gone through was all browns and faded yellows. Suddenly everything is rupturing the stillness.

Summer seems to have arrived very early with the kind of hot days more typical of October than the end of August. The oak took this as its signal to get going.

But something else scientifically fascinating prompts me to ask a question: how does such a mighty tree find the energy to burst into leaf at the end of a long winter with no rain and harsh cold spells?

Part of the explanation - obviously - is that its underground root system finds water and "pumps" it up as lifegiving sap into the trunk, branches and twigs. But something else is involved. This is no mechanical pump.

I'm no botanist but I am curious about what's going on the tree, so investigated.

We need to understand what a strange substance water is. It is plentiful in the solar system but it has extraordinary properties that have made all life possible. Its molecules cling strongly to one another and to other surfaces, allowing an unbroken thread of water to be drawn upwards through the finest vessels of a tree against gravity.

These same unusual properties—along with its remarkable ability to dissolve substances and store heat—are among the reasons water makes life as we know it possible.

Water molecules stick to one another — cohesion — and to the walls of the microscopic xylem vessels in the tree — adhesion. Surface tension and capillary forces help maintain columns of water inside the tree.

But the main driving force begins at the top, not the bottom. Once leaves start developing, water evaporates from their surfaces through microscopic pores called stomata. This evaporation, or transpiration, creates negative pressure — tension — within the xylem.

Because water molecules cohere to one another through hydrogen bonding, water lost from the leaves effectively pulls the column behind it upwards, all the way down through the trunk to the roots.

So a great oak is less like a building with a pump in its basement than an extraordinary biological wick (as in a paraffin lamp) under tension, with evaporation from above pulling water upwards from below.

One puzzle is how a tree with no leaves can begin its rejuvenation to start with.

Before there are open leaves, the oak cannot generate much transpiration to pull through stomata. The initial awakening is powered and supplied differently.

During the previous summer and autumn, the oak stored carbohydrates—especially starch—in its roots, trunk and woody tissues. When winter dormancy ends, enzymes convert some of that starch back into soluble sugars. Those sugars provide both the energy and raw material needed for dormant buds to resume cell division and expansion.

From now on I will look at our oak tree with a good deal more respect for its scientific know-how. It is beautiful AND clever. So are all growing things.

The oak presents a lovely chicken-and-egg story: it needs leaves to operate its main water-lifting system, yet it needs water and energy to make those leaves. The solution is that the tree carries enough stored resources and has enough pre-formed machinery to get the first leaves open.

Then the solar-powered, evaporation-driven system takes over.

Would that we were so clever.

Visit Otters Haunt Eco Retreat. 084 245 2490
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03/09/2026

WHO COMES TO SEE A CRATER?

People who come to explore our neck of the woods are often curious about who else drives off the beaten track to find the world's largest known meteorite impact structure. Well, I did some research into 25 years of records since we started doing tours and briefings here.

One truly dedicated group are the UNESCO World Heritage Site visitors who systematically tick off sites on a list that now runs to more than 1,200 across the globe. They key in from Machu Picchu, Angkor Wat, the Grand Canyon and Robben Island.

Then there are visitors from the world's space agencies: representatives of NASA, European and Chinese agencies, Japan, and various institutes of astronomy from Russia, Brazil and Mexico. They're usually very well primed about planetary defence — which means, among other things, hunting the heavens for potentially dangerous near-Earth objects (NEOs). They want to see what kind of damage a really big one can do.

Plenty.

And then there are the geologists, either singly, or with geotour groups, or as professors with their students. They spend days examining and sampling rocks metamorphosed by the shock of impact. They never seem to tire of debating the real effects of planetary bombardment, especially over sundowners and braais.

As one told me: "Geology is beer and guesses."

The South African domestic market for our tours began to shrink from about 2015 as more whites left the country or simply grew too old to care about speeding space rocks that might one day make us all extinct. But after COVID there was an explosion of black visitors who couldn't get out of lockdown fast enough.

That largely middle-class black audience is growing fast. At the same time, government schools have overtaken private schools on the educational adventures we offer. These are days that start with talks, demonstrations, videos and problem-solving, and end with hikes into the Dome Bergland.

World Heritage Sites form part of the geography curriculum in high school. Come here on a weekday and you may see a hundred or more teenagers grouped around our instructors, learning about South Africa's gold — exposed at the surface partly because of the extraordinary geological upheaval and subsequent erosion associated with the impact structure — as well as the history, biology and ecology of the region.

One very attractive way to see what the asteroid did to the planet is to drift downriver in a raft. The Vaal River has helped to erode and expose the deep geology of the Dome Bergland in a way that driving the roads never reveals.

Our traditional white visitors haven't disappeared, but they often come in mixed groups, which says something about how society is integrating across racial lines. The couples who call are mostly just curious to know what all the fuss is about. They love Parys with its coffee bars, restaurants, antique shops and art galleries.

All in all, what we've seen over the past two and a half decades is a steady and increasing flow of visitors from everywhere. Our biggest problem is that government has so far failed to capitalise on this tourist node in the heart of the country.

There are virtually no functioning state visitor facilities. Signage is woefully inadequate. Museums and interpretation centres have struggled to remain operational. Much of what visitors actually experience is provided by private enterprise, guides and civic associations.

That lack of sustained official support is a scandal, particularly when tourism is repeatedly identified as an important generator of jobs and local economic activity alongside farming, mining and industry.

The crater isn't the problem. It is a miniature picture of how South Africa itself is changing. There is more interest in science, from schools upwards. There is grassroots entrepreneurship. There is a bustling boom town, Parys, at the centre of it.

For 25 years the visitors have been coming. The Dome has moved from specialist geological curiosity towards mainstream heritage tourism, while the public infrastructure has failed to follow.

* Visit and see. 084 245 2490
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29/08/2026

THE GHOST THAT SHOOK EARTH

Visitors are surprised when I say — as a guide to the biggest, baddest impact crater on Earth — that it’s nothing exceptional. What? Have they come all this way for nothing?

Not exactly. It is vast, impressive and — despite being what I call a “ghost crater” — it is still the largest confirmed impact structure on Earth. It is literally the Everest of impact craters.

Everest because, when it formed from the unimaginable violence of a huge asteroid striking what is now South Africa some 2.023 billion years ago, it produced an enormous crater perhaps 250–300 kilometres across. Mountains were thrown up around the impact structure, while rocks deep beneath the impact rebounded upwards in a gigantic central uplift. In geological terms, the transformation was almost instantaneous — measured in minutes rather than millions of years.

Today it is a ghost crater because, during the two billion years since its formation, erosion has stripped away kilometres of rock. We are not really looking at the original crater surface at all. We are looking into its deeply eroded roots. What remain are fragments of the extraordinary geological architecture produced by the impact.

The first picture shows a visitor standing in the centre of the crater - where the distant rim of mountains can barely be seen. People who come looking for a hole in the ground are not going to find one. And the asteroid completely vaporised, leaving nothing of itself except mineral traces.

The second picture is the extraordinary hand drawn map drawn by geologist Louis Nel and his assistant, a Mr A Parrott, in 1927 - long before the Dome was understood as the centre of a meteorite crater. They had no theory about how it formed.

This is the Vredefort Dome in central South Africa, about 120 kilometres from Johannesburg. Johannesburg itself lies within the much larger original impact structure, although the Witwatersrand ridges were not created by the impact. They are vastly older rocks which were deformed, tilted and exposed by it.

And here lies one of Vredefort’s great historical consequences. The impact did not create the Witwatersrand gold. That gold was already there. But by overturning, faulting and later helping expose the ancient gold-bearing rocks, the Vredefort event played an important part in the geological story that eventually made the world’s greatest goldfield accessible to human beings.

Yet, while Vredefort is the largest confirmed “star scar” — or astrobleme — preserved on Earth, enormous impacts themselves are nothing exceptional when we look across the whole history of the planet.

The early Solar System was a violent place. During its first hundreds of millions of years, the young Earth was repeatedly struck by asteroids, planetesimals and other bodies left over from planetary formation. Some impacts must have dwarfed Vredefort. Almost all traces of them have disappeared through erosion, burial, metamorphism and plate tectonics.

Impactors also contributed water and other volatile compounds to the developing Earth, although we should be cautious about saying they brought “most” of our water.

Where Earth’s oceans came from remains an active field of research. Water was probably supplied and redistributed through several processes, including material already incorporated into the forming Earth and later delivery by water-bearing asteroids, with comets probably making a smaller contribution.

That is what makes Vredefort so special. UNESCO designated the Vredefort Dome a World Heritage Site in 2005 because it preserves outstanding evidence of the world’s largest known impact structure and provides an extraordinary window into the immense forces generated by planetary collision.

But here is the question that increasingly fascinates me.

Large impacts are not merely surface events.Long before the impact origin of Vredefort became accepted, some geologists tried to explain the Dome through versions of the old “cryptoexplosion” idea — an enormous, mysterious explosion from within the Earth.

That explanation was eventually displaced by overwhelming evidence for meteorite impact. Ironically, however, some of those early observations drew attention to something genuinely important: Vredefort has deep roots.

Modern geophysics shows that very large impacts can fracture, melt, displace and reorganise enormous volumes of crust. At still larger scales, researchers are investigating whether the colossal bombardment of the early Earth could have influenced crustal differentiation, mantle dynamics and perhaps even the development of the earliest continental nuclei.

That does not mean science has established that impacts created the continents. It hasn’t. The hypothesis ranges from well-supported impact physics at one end to much more speculative ideas about the origin of cratons and plate tectonics at the other.

The jury is still out. Yet history gives us reason to keep asking awkward questions. Scientists once doubted that stones could fall from the sky. For much of the twentieth century, many geologists resisted the idea that enormous meteorite impacts had profoundly affected Earth history. Both positions eventually changed when the evidence became overwhelming.

The old geologists were wrong about the cause, but their attention to deep structural disturbance was not necessarily misplaced.

Maybe another revision is now beginning — not about whether great impacts happened, but about just how deeply they helped shape the planet beneath our feet.

Come to the Vredefort Dome and see the ghost for yourself.

You may be shocked. The Earth certainly was.

* Post was written by me, Prof Graeme Addison, not AI. The latter proofread my text.

29/08/2026

THE GHOST THAT SHOOK EARTH

Visitors are surprised when I say — as a guide to the biggest, baddest impact crater on Earth — that it’s nothing exceptional. What? Have they come all this way for nothing?

Not exactly. It is vast, impressive and — despite being what I call a “ghost crater” — it is still the largest confirmed impact structure on Earth. It is literally the Everest of impact craters.

Everest because, when it formed from the unimaginable violence of a huge asteroid striking what is now South Africa some 2.023 billion years ago, it produced an enormous crater perhaps 250–300 kilometres across. Mountains were thrown up around the impact structure, while rocks deep beneath the impact rebounded upwards in a gigantic central uplift. In geological terms, the transformation was almost instantaneous — measured in minutes rather than millions of years.

Today it is a ghost crater because, during the two billion years since its formation, erosion has stripped away kilometres of rock. We are not really looking at the original crater surface at all. We are looking into its deeply eroded roots. What remain are fragments of the extraordinary geological architecture produced by the impact.

The first picture shows a visitor standing in the centre of the crater - where the distant rim of mountains can barely be seen. People who come looking for a hole in the ground are not going to find one. And the asteroid completely vaporised, leaving nothing of itself except mineral traces.

The second picture is the extraordinary hand drawn map drawn by geologist Louis Nel and his assistant, a Mr A Parrott, in 1927 - long before the Dome was understood as the centre of a meteorite crater. They had no theory about how it formed.

This is the Vredefort Dome in central South Africa, about 120 kilometres from Johannesburg. Johannesburg itself lies within the much larger original impact structure, although the Witwatersrand ridges were not created by the impact. They are vastly older rocks which were deformed, tilted and exposed by it.

And here lies one of Vredefort’s great historical consequences. The impact did not create the Witwatersrand gold. That gold was already there. But by overturning, faulting and later helping expose the ancient gold-bearing rocks, the Vredefort event played an important part in the geological story that eventually made the world’s greatest goldfield accessible to human beings.

Yet, while Vredefort is the largest confirmed “star scar” — or astrobleme — preserved on Earth, enormous impacts themselves are nothing exceptional when we look across the whole history of the planet.

The early Solar System was a violent place. During its first hundreds of millions of years, the young Earth was repeatedly struck by asteroids, planetesimals and other bodies left over from planetary formation. Some impacts must have dwarfed Vredefort. Almost all traces of them have disappeared through erosion, burial, metamorphism and plate tectonics.

Impactors also contributed water and other volatile compounds to the developing Earth, although we should be cautious about saying they brought “most” of our water.

Where Earth’s oceans came from remains an active field of research. Water was probably supplied and redistributed through several processes, including material already incorporated into the forming Earth and later delivery by water-bearing asteroids, with comets probably making a smaller contribution.

That is what makes Vredefort so special. UNESCO designated the Vredefort Dome a World Heritage Site in 2005 because it preserves outstanding evidence of the world’s largest known impact structure and provides an extraordinary window into the immense forces generated by planetary collision.

But here is the question that increasingly fascinates me.

Large impacts are not merely surface events.Long before the impact origin of Vredefort became accepted, some geologists tried to explain the Dome through versions of the old “cryptoexplosion” idea — an enormous, mysterious explosion from within the Earth.

That explanation was eventually displaced by overwhelming evidence for meteorite impact. Ironically, however, some of those early observations drew attention to something genuinely important: Vredefort has deep roots.

Modern geophysics shows that very large impacts can fracture, melt, displace and reorganise enormous volumes of crust. At still larger scales, researchers are investigating whether the colossal bombardment of the early Earth could have influenced crustal differentiation, mantle dynamics and perhaps even the development of the earliest continental nuclei.

That does not mean science has established that impacts created the continents. It hasn’t. The hypothesis ranges from well-supported impact physics at one end to much more speculative ideas about the origin of cratons and plate tectonics at the other.

The jury is still out. Yet history gives us reason to keep asking awkward questions. Scientists once doubted that stones could fall from the sky. For much of the twentieth century, many geologists resisted the idea that enormous meteorite impacts had profoundly affected Earth history. Both positions eventually changed when the evidence became overwhelming.

The old geologists were wrong about the cause, but their attention to deep structural disturbance was not necessarily misplaced.

Maybe another revision is now beginning — not about whether great impacts happened, but about just how deeply they helped shape the planet beneath our feet.

Come to the Vredefort Dome and see the ghost for yourself.

You may be shocked. The Earth certainly was.

* Post was written by me, Prof Graeme Addison, not AI. The latter proofread my text.

084 245 2490

25/08/2026

STONES OF A CIVILISATION
The empty wind sings a lament over ruins

Scattered across the hills throughout the Highveld of South Africa are the ruined stone remains of a vast trading civilization. These are not structures built by aliens from space, as some storytellers wish us to believe.

They are the remnants of indigenous Sotho-Tswana cattle-herding, iron age communities that thrived from at least 1500 years ago until wars and land dispossesion broke their existence. They traded amongst each other but also up through exchange routes in Africa to India, China and Indonesia.

Glass beads and pottery from the Far East, found among the ruins, attest to this trade. In exchange the people of the interior send hides, ivory and possibly precious metals to distant lands. What I have called the "African Silk Road" trading artery through East Africa came crashing down when Portuguese slavers allied to Arabs and coastal tribes, plundered the continent for human captives.

At the tail end of the trading system in southern Africa, the rise of the militant Zulu state and the arrival of Voortrekkers and British colonialists combined to shatter the pastoral life of the inhabitants. What they left behind is covered in a fascinating YouTube video here: https://youtu.be/HDufZTjMQe4?si=QbzXE5-vl5u5tUgM

The architecture of these settlements has been compared to fractal geometric patterns. The circles repeat and seem to flower outwards.

Hundreds of stone ruins have so far been counted and there are undoubtedly many more. From the Magaliesberg to Klerksdorp, Melville Koppies to the Vredefort Dome, Pretoria to Klipriviersberg and Suikerbosrand, people

One interesting thing about the ruins of huts and kraals that we see today is that they are built from readily available stones throughout what is known as the Bankenveld biome. This biome is a mixture of grassland and bushveld ideal for year-round cattle grazing.

The rocks, however, range through quartzites, granite, basalt and limestone - all sufficiently small to make handy building blocks. Perhaps the sharp temperature differences and weathering of the Highveld helped to break up more solid boulders into these useful pieces.

The hills and kloofs of the Bankenveld provided grassland, sheltered valleys, wooded slopes, reliable water, cultivable pockets and different grazing environments within relatively short distances. A community could therefore hedge against climatic variability by moving cattle between ecological niches rather than migrating great distances.

Archaeological evidence from Suikerbosrand shows an evolution from relatively dispersed pastoral homesteads into increasingly concentrated settlements and eventually substantial towns.

I have studied the Bankenveld in the Vredefort Dome Bergland but the biome extends across parts of Gauteng, North West, northern Free State and into Mpumalanga. It contains at least 16 major vegetation types and is really a loose aggregation of zones that cross the fairly well watered Witwatersrand into much drier areas.

Many South Africans, white and black, are unaware of this history and of the landscsoe that made it possible.

Join me for a tour or briefing on the Vredefort Dome and it's fascinating past. Prof Graeme Addison 084 245 2490 https://vdome.co.za

10 Ancient Stone Ruins in South Africa No One Can Explain

23/08/2026

23/08/2026

GOING NOWHERE HAPPILY
Deserted roads in the Free State platteland

Limitless views. Late winter rains turned dust into mud, then deep ruts that are now now dry and hard, crumbling under my wheels. What's not crust is dust.

C'est magnifique!

Today I was alone on this route, just mulling over how to finish my latest book (No.16) and get done with it. It's a popular treatment of the Vredefort Dome - where my wheels took me today. Occasionally I do this circuit of 60km with others on ebike outrides.

It's easy and the wide open spaces really get inside your head, as if all the world is forever.

Graeme: 084 245 2490

Join me for an ebike tour. Bikes for hire. Fully guided and vehicle supported. See the Vredefort Dome on two wheels.

19/08/2026

19/08/2026

THE DOME IS NOT WHAT IT WAS
The biggest known impact crater is a ghost

On a long haul flight in a jetliner you may cruise at up to 42000 feet or 10,7km above the ground. Now consider this.

The world's biggest and best preserved meteorite crater is just a ghost of its former self. A jet would have been at ground level when the crater was formed.

If you could restore about 10 km of vanished Vredefort rock vertically above where you can stand in the Dome today, its top would be roughly where an airliner cruises, around jet-stream altitude.

I did a thought experiment to imagine how it is that the original crater surface, that formed on impact about 2,023 billion years ago, can have eroded by the height that a jetliner flies. We know it has eroded from various kinds of scientific evidence.

For one thing, the shatter cones that formed around the rim of the crater tend to orientate themselves towards a vanished point sky between 8 and 12 km above the present surface. These conical shaped rocks were deformed by extreme shock.

Another indication is the rocks now at the surface which would originally have roared up from deep down and overturned. They have clearly been exposed by later ice, water and weather erosion over vast spans of time. They show marks of glacial grooving and scouring l, showing they are what remains of thicker layers.

And then there is the Vaal River itself, which has cut down from a surface far above the original crater. This surface was deposited during Karoo times on top of the older crater, burying the Dome and its surrounding rings of mountains. The river is what geologists call a superposed watercourse that, as it wore away the land, found radial cracks pointing towards the centre.

These cracks cross the concentric rings of the huge three-ringed crater. The landscape is like a pane of shattered glass hit by a stone. See the illustration.

So what we have at Vredefort is the remnant of a much more prominent feature - a ghost. My thoughts experiment asked how much a landscape needs to be eroded, per year, to reduce it by 8-12 km over two billion years.

The answer astonished me. A mere ,005 mm annually will produce what we have today. To do this experiment I added the later Karoo overlay to the Dome's original surface, giving a total depth of 10,5km of combined surface. That's a very cautious guess as the Karoo may have been a lot thicker.

About 0.005 mm per year is five micrometres a year, or expressed more intuitively, 1 millimetre every 193 years. No-one can notice this amount of erosion without precise instrumental measurement.

The Dome does not require some fantastically violent, continuous stripping process to account for its present exposure. Almost imperceptible average denudation, sustained over deep time, is enough to remove a mountain-sized thickness of crust.

Of course the actual history was nothing like steady erosion. There were probably pulses of rapid uplift and erosion, long intervals of near-stasis, burial beneath sediment, glacial scouring, Karoo deposition, renewed uplift and later stripping. But the arithmetic gives us an extremely useful baseline.

The processes doing the enormous work can be almost invisible on the human timescale. A person standing in the Dome for a lifetime might see virtually no lowering of the landscape attributable to regional denudation. Yet given two billion years, that same rate can remove a rock column higher than Everest.

Next time you take a long flight and reach cruising altitude, look down. You don't have to imagine the vanished portion of this very old crater: there it is.

Join me on a tour or to get a self-drive briefing. Prof Graeme Addison, author and tour guide. 084 245 2490 https://vdome.co.za

* I am currently working on the third and final draft of a new book on the Dome, Crater of Gold. This post and others like it are summaries put online for comment and reaction. It is not the work of AI but my own research using diverse sources, personal observation and some sourcing by ChatGPT and from Google.

12/08/2026

THE RIVER RISES ..and we plan the Dome rafting season

Bad weather has its benefits. Today the Vaal River - our home for a quarter century - rose fast after the winter rains and snow across the Highveld.

With summer near the weather will warm up. This year - and all the way into April 2027 - THE RIVERMAN will be running whitewater and calm water trips through the spectacular Vredefort Dome. The Vaal is one of the world's oldest rivers and is the only major river to flow through an impact crater - the biggest crater, at that.

Our raft-camping expeditions can be two or three nights, sleeping out on islands. Or if you prefer, you can stay in accommodation overnight.

The halfday and full day whitewater trips have been The Riverman's winner since 2002. And our popular Dome Drift winds down the glacial valley near Venterskoon on calm but flowing water.

Take your pick! Contact The Riverman for details of all three options. Only 120 km from Johannesburg and the ideal way to see the Vredefort Dome crater with an expert guide - Prof Graeme Addison - to explain it all. No experience needed.

Call or WhatsApp 084 245 2490 Https://Riverman.co.za/