Along the Barberton Makhonjwa Geotrail, some of the oldest rocks on earth are creating quite a stir
Words and Pictures Sue Adams
If you thought Star Wars was riveting, just wait until you hit this geotrail in the Lowveld, where tsunamis, volcanoes, meteorites and colossal tides caused all the excitement.
Many of the oldest rocks in the world can be found here in this small corner of Mpumalanga between Barberton and the Swaziland border. And they are rocks that have given us one of the most intriguing stories of where it all began.
More than three billion years old, the rocks are only just beginning to reveal how our planet was formed. Yes, geologists have waxed lyrical about this area for at least 40 years, but to most of us they’re a dry bunch that chip away at rocks and mumble unpronounceable words. And, after all, what can be that interesting about rocks? Or that’s what I used to think.
Author and environmentalist, Tony Ferrar, met some of these geologists tramping about the hills, and the more he learned the more fascinated he became. He now offers guided tours along the Barberton Makhonjwa Geotrail that give us a new perspective on this geology.
In the 1960s, the Viljoen brothers were both doing their PhDs on the geology of this area when they found undescribed lava in the Komati River valley that was three times hotter on emerging from the earth than was any other lava. They called it Komatiite, something that had geologists across the world sitting up to focus on this area known as Barberton Mountain Land.
This has led to ongoing discoveries, most significant that there were signs of life one billion years earlier than initially thought. Suddenly this area became Geology Heaven, with hundreds of international geologists arriving here annually to hopefully unlock more secrets.
In 2008, Tony and a few other enthusiasts were inspired to apply for World Heritage Status for Barberton Mountain Land because of its incredible geological value. This is ongoing and the story has been a long one. Funds are an issue, but in the meantime the Barberton Chamber of Business and their project development agency, the Barberton Tourism and Biodiversity Corridor, have used funds to develop tourism projects, the biggest so far the new Barberton Makhonjwa Geotrail.
The 40km self-guided, self-drive route begins in Barberton and heads out on the R40 towards Josefsdal, south to Bulembu at the Swaziland border, near the old, now-inactive Havelock asbestos mine. Along the way there are 11 developed geosites, all with well-designed plaques crammed with interesting information about the geology, the wildlife, the history and the culture of the area. There is also a wonderful 50-page guide book on the geotrail written by Tony Ferrar and Dr. Christoph Heubeck, a research geologist from the Free University of Berlin, who heads for South Africa every European summer to study our rocks. Each geosite has something special to make a different aspect of that time come alive.
A huge boulder with black crinkly lines on it, one I would normally have leant against and not given another thought to, reads like a storybook. The little black lines are traces of fossilised biomats and are the first signs of life on Earth that you can see with the naked eye. “There is so much information in this rock alone that Christoph says he could get a student to write an entire thesis on it,” says Tony.
There is another story to this particular rock. Its original position was somewhat inaccessible and dangerous for people to stop at so the 20-ton boulder was moved by a local breakdown company. “We had a fun day throwing rocks around,” says Tony with a cryptic smile.
What looks like a bad erosion scar of white sand has a very different tale to tell. White tidal sands like these have unlocked new information – when this rock was formed the moon was much closer to earth, the tidal pull was stronger and the water rushing around the earth, with no land mass to slow it down, made for huge tidal water surges. “Isn’t it amazing what geologists can deduct from this white, layered, sandy rock?” asks Tony.
Further on, a rather chaotic jumble of different coloured rocks mashed together is the basis for a detective story. At some stage there must have been an underwater seismic event that caused the sediment to break up at the same time, and possibly cause a tsunami. “Because there are still such long, unbroken pieces of sediment, this event must have occurred quite slowly,” says Tony. “And because the edges of this chert conglomerate are sharp and not rounded off they didn’t tumble far.”
The Barberton-Bulembu road has been in existence since miner Alan Andrews pegged it out on horseback so that he had access to mining and timber. The first ten kilometres out of Barberton are now tarred, but only recently has the rest of the road been upgraded, creating newly cut slopes. This opened up a new story, exposing geology never seen before and also creating potential for the geotrail.
Tony laughs as he remembers a conversation with a master blaster working on the new Bulembu roadworks. “After a large blast I picked up a piece of grey sandstone and showed him the black crinkly lines and explained to him that they were the first signs of life on Earth. He turned to me and said, ‘Jislaaik, and we just sommer blow it up, hey.’”
Like the master blaster, now I also have a new perspective on rocks. Now I’m the one in the car that crawls past each road cutting, in the hope of finding a fascinating new rock. I even have some pet rocks on my windowsill that might not speak much but can still tell a fascinating story.