South Africa's Minerals
On Friday, we decided to revisit an area we had already been to. This section covers the contact between the Bushveld rocks (green, colors as seen on the map) and the leptite (purple), granophyre (yellow) and granite (pink) rocks that we are interested in.
What the map doesn’t show is topography. Pink granite can be very resistant, meaning it doesn’t weather away as much as other rocks, forming very steep cliffs. We hiked for some time up steep valleys without quite reaching the top. On the way, I think we met just about every type of pricker bush South Africa has to offer.
The day was long, but came with a reward. On Friday night we had a large “braai,” or barbeque, with some of the farmers who helped us gain access to the lands. We ate chicken, lamb chops, t-bone steaks, a type of sausage made from kudu meat and “putupap,” a crumbly type of maize meal with the texture of coucous. One local farmer also brought fresh “amassi,” boiled, unpasturized milk that is left to sit in yogurt culture overnight. The result is a tangy/sour thin drinking yogurt. I thought it was delicious, but most of the farmers dislike it. I was especially grateful for the feast because Friday was my birthday.
We woke the next morning and headed to the top of the plateau to collect more lava samples and try to finish the section we started on Friday. There is a town directly on top of the valley that we were hiking the day before, so we decided to drive there and see if we could find the rest, from the top this time. Thankfully we were successful.
While we were sampling, some local children grew curious about what we were doing and followed us as we worked. On previous trips, Ed and I have carried a Polaroid camera with us so that we can take pictures of the children and give them aways. The kids are always amazed and delighted to see themselves in the photos. Today we used up our final packs of film, and because Polaroid stopped manufacturing it last year, we won’t be able to do this in the future.
On Tuesday we drove to the Steelpoort River Valley, about a hundred kilometers away. Work on a new dam and road has begun since we were here last, in 2006 and 2007. Once it’s finished, the dam will flood much of our field area, submerging some of the rocks we are studying. It’s a good thing we collected some when we did. The project will bring running water to the Sekhukhune villages, where most people still rely on outhouses and water delivered in drums.
To build the dam, the department of water affairs is buying up the surrounding farms but ownership is not always clear. Electric fences and locked gates line much of this land and on our first day of sampling, we had to contact both the farmers and the department of water affairs to ask for access. We also notified the district magistrate and local police to be safe.
In this region, we’re studying how Bushveld Complex rocks were intruded, or thrust, into “country rock,” a mix of granite, granite-lavas called granophyres, and other lavas we were sampling earlier in the week. My research suggests that the lavas and possibly the granophyre originated in the Bushveld Complex. In that case, the Bushveld would not have been intruded into these rocks. The contact among these layers is particularly important for us in testing this hypothesis while we are here.
Today we slogged up a valley of thorny trees where the Bushveld, granophyre, granite and lavas have all been mapped. At one point, while stopping for water, we heard loud barking – almost like a dog. I worried it might be an angry animal. We never caught a glimpse but figured out later it was probably a bushbuck, similar to a deer.
On our hike we found a black rock with pink cross-sections of feldspar, probably lamprophyre, the rock that cross-cuts the rocks we are studying and that may be related to a younger magmatic event in this area. Eventually, we locate a place where Bushveld rocks are touching leptite, a rock formation that has been heated, melted and recrystallized. The leptite in this area has pink veins of granophyre surrounding what may be sedimentary rocks. If you squint, you can almost imagine the granophyre melting into the grey blobs of sedimentary rock.
In the coming days, we hope to visit more areas with this type of contact to collect samples that will tell us how the chemistry is changing from one place to another.
We started the morning with breakfast and shopping for lunch provisions. We bought a large bag of oranges grown in the groves that surround this region for the equivalent of $1.50, along with cheese and, of course, biltong. The butcher offered many kinds of biltong, from the shaved, proscuitto-like variety to the serious cowboy jerky type. We stocked up on two varieties–chili bites and cabanossi–and headed for the road.
The lava flows we are studying are more than two billion years old yet some of their structures are still intact. The lava in one, the Kwaggasnek formation, is full of frozen air bubbles.
Another, the Schrikkloof, shows how the lava once flowed. Geologists named these lavas in the 1990s. In Afrikaans, a “kwagga” is a cross between a donkey and zebra, now extinct while “nek” implies a valley. “Schrik” is Afrikaans for fright while “kloof” means cliff. The geologists who mapped this area were apparently chased by a rhino while doing their work.
On our third day, traveling down a deserted, gravel road we got a flat. Fortunately, we had a spare which we used to drive to the next town to repair the original. It’s a good thing we did. By the time we reached our destination, our spare was also flat. After fixing both tires, we were back on the road to collect more samples.
Heading home to our lodge, we saw several animals through the fence: an ostrich with skinny white legs, a small herd of impala – smallish antelope – and springbok, similar to impala but with short pointy horns on their heads. Close to the road were kudu, which are twice the size of deer with white stripes on their side, curly horns and white tails. We also saw warthogs and wildebeests. Apparently dusk is the time to observe wildlife. Maybe they enjoy the sunset as much as we do?
On Saturday morning, Ed and I left Pretoria for the next phase of our trip: field work near the Loskop Dam in Mpumalanga Province where a large volcano once existed about two billion years ago. No one has been able to find where this ancient volcano stood but lava flows in the area suggest there was once volcanic activity. We will be collecting rocks and analyzing their structure to piece the story together.
On our way, we passed through Witbank, one of South Africa’s largest coal-mining operations. From the road, we spotted the coal plants’ big cooling towers as well as coal trucks parked along the road.
The Loskop dam area where we will be working for the next several days is more mountainous than Pretoria, with cliffs and rolling hills. The dam is also a spectacular structure that has created a large lake where crocodiles and hippos like to hang out. Unfortunately, the extensive mining in this region, at Witbank and the Bushveld Complex, has taken an ecological toll. Acid from the mines has drained into the lake, gnawing away at the bones of the crocodiles living there. Only juvenile crocodiles live there now.
One lava formation that we will be studying is called the Damwal, or “Dam Wall.” Nearby are several game reserves where Impala, Kudu, Zebra, and Wildebeest are raised. The game keepers have warned us about the leopards that live in some of the surrounding mountains and valleys. We’ve been told about a wild leopard breeding area in the valley across the river where animal carcasses are often found dangling from the trees.
Luckily for us, a tall wire fence lines most of the road where we are working and the only animals we’ve seen so far are baboons. We typically sample along the road, not out of laziness but because this is where the rock is most exposed. (Road building often involves blasting away rock, creating fresh surfaces that have not been exposed to weathering for very long.) It is much easier to collect here than to dig through layers of sediment or hammer away at boulders.
After a morning lecture about the Bushveld Complex and the processes of concentrating ores in magma bodies, Ed and I had to go to the University of Pretoria for Thursday afternoon. I was invited to give a lecture and we were able to have some very interesting conversations about Bushveld research with the people who have been working on it for many years.
While we were gone, Natasha, Jay and Chris helped the teachers develop presentations for sharing the material they learned this week with other teachers. Nearly all said they would start incorporating the material into their lesson plans immediately. Each teacher sees 200 to 300 students per day. With 20 teachers in our workshop, this means that 4,000 to 6,000 students will potentially benefit. If the teachers pass on this knowledge to other teachers, the impact could be even greater.
Friday was the last day of our workshop. The teachers gave their presentations and we gave each one a certificate for participating. We have had so many great discussions about geology, education, global economies, global politics, and so much more. I have learned so much from each one of them. The teachers also had presents for us–a vuvuzela and South African flag and futbol scarf for each of us. Our day ended with singing, clapping and smiling.
We woke up Wednesday morning to find out that all unionized government workers, including public school teachers, were on strike. All schools were shuttered and we worried that no one would show up for our workshop.
But we arrived at class to find all of our teachers present. They told us this was a once in a lifetime opportunity and they didn’t want to miss a moment.
For the day’s activities we traveled to the Cullinan diamond mine, where one of the world’s largest diamond—the Star of Africa—was discovered. With help from a Cullinan tour guide, Ed and I discussed how diamonds form deep in the Earth. The mine is still active today and we watched as rock was transported to the surface to be crushed and washed for diamond separation. This sparked a discussion about the types of careers that are available in the mining industry – everything from geologists to engineers to miners to doctors.
After the trip, we talked about other potential field trips and how to plan a teaching curriculum around them. One major reason I went into geology was to be out in the field exploring. Field trips are a great way to teach students to observe the world around them and gain a deeper understanding of the subject material.
Our teaching workshop continued Tuesday with a lecture about mineral resources and their economic importance. South Africa has abundant platinum and gold but also lesser-known elements like vanadium, chromium, and manganese. Vanadium and chromium, important to the steel industry, are found predominantly in the Bushveld Complex where our research is focused. Chromium gives steel much of its strength while vanadium stabilizes it to prevent expansion and contraction, allowing oil pipelines in Alaska and Russia, for instance, to resist cracking during extreme temperature swings.
Later that day I gave lectures on the formation of coal and gold, two of South Africa’s leading resources. The country gets more than 75 percent of its energy from coal and more than 40 percent of the gold mined on Earth has come from the Witwatersrand deposit near Johannesburg. Some estimate that more than 50 percent of the world’s reserves still remain here. In fact, the discovery of the ‘Rand’ deposit is what led to Johannesburg’s founding. The South African currency, the rand, is named for this gold deposit.
The teachers seemed to especially appreciate Chris Emdin’s discussion of how to engage students in the classroom–here students are called “learners” – to explore the material on their own terms. South Africa has 11 official languages. While all formal education and exams are done in English, English is almost never the student’s first language. This makes science especially challenging to teach. Chris showed the teachers one activity for helping students translate vocabulary words across English, science, their native language and slang. This way the students can incorporate the words they hear in class into their lives.
During the morning session one teacher told me that he had gone through five textbooks the night before searching for text on plumes, or hot spots. My lecture the previous day had discussed how islands like Hawaii, Iceland, and Reunion – off the coast of Madagascar – form from magma rising deep from Earth’s mantle. The teacher told me that in Afrikaans there is no word for “plume” and that none of his textbooks included it. He asked me for a definition and some pictures and said he would approach the Afrikaans textbook publishers in Johannesburg about including the term in their next editions.
The workshop that we are here leading is designed to help South Africa high school teachers make geology come alive for their students. We want to share basic concepts, such as how rocks and minerals form, but also provide activities and materials that can make the concepts more accessible.
In planning the workshop, we outlined basic geologic themes that we wanted to get across: geologic time, plate tectonics and the rock cycle. As the “themes ambassador,” I’ll be giving lectures on all three topics on the first day of the workshop.
It was an exhausting first day but rewarding. The high school teachers were so engaged and asked so many great questions that both of my lectures went significantly over the time limit. We discussed how teaching geologic time can conflict with religious teaching, the formation of hot spots and how volcanoes can impact climate. After the first lecture, Jay shared some simple activities around plate tectonics and plate motions that the teachers could reproduce in their classrooms.
After the rock cycle lecture, Jay hosted a show-and-tell with our New York City rocks. He explained to the teachers that he typically gets his rocks for free at city construction sites. Usually the construction companies pay people to haul the rocks away so workers are happy to let Jay take as many as he wants. The teachers clapped and applauded when he handed out our samples of Manhattan schist, a metamorphic rock, Palisades sill, an igneous rock, and New Jersey arkose, a sedimentary rock, for them to take back to their classrooms. He also distributed a map showing where the rocks were collected and discussed how the teachers could make a similar map for rocks in their area.
It was a great first day and I’m looking forward to a fun and educational week.
We arrived in the city of Tshwane (formerly named Pretoria) on Sunday after a day-long journey from New York. Tshwane is the executive capitol of South Africa and according to several locals we met while walking through the city, home to the most national embassies after Washington D.C. More importantly, Tshwane is where the U.S. defeated Algeria in the World Cup just two months ago. The city is dear to my heart because it is where my grandfather came many years ago for surgery while working for a hunger relief program in Zambia.
We spent the day exploring the city and trying to beat our jetlag. We visited the spectacular gardens surrounding the city’s government buildings as well as the former home of Paul Kruger, the president of South Africa before the British took control from the Boers, or its Dutch-speaking settlers, in 1900. The Kruger House Museum chronicles the Transvaal and Boer Wars and showcases the furniture, clothing and even kitchen appliances of late 19th Century South Africa.
We later stopped at a café near the main square and got a much-needed caffeine jolt and tried “biltong,” a type of cured meat made from wild game that tastes like prosciutto. On our way to our hotel, we passed Tshwane’s Brooklyn neighborhood and joked about traveling 24 hours just to end up where we started.
I’m flying to Johannesburg on Friday in what will be my third expedition to South Africa. In the past I’ve traveled here to study the Bushveld Complex, a huge lava formation that provides over 70 percent of the world’s platinum as well as other valuable ores, such as vanadium and chromium, both used to make steel.
This year I’ll continue my fieldwork in the Bushveld but first we will provide a week of geology-education training to South African high school teachers from Pretoria and the surrounding areas. South Africa’s mines provide the single largest source of jobs in this country yet most South Africans know little about the earth processes that created its mineral wealth—its gold, diamonds, platinum and coal. Over five days, we will provide lectures and hands-on activities that the teachers can use in their classrooms. We hope to teach basic geologic concepts through the lens of how and where different ores form.
The workshops grew out of conversations that my Ph.D. advisor, Ed Mathez, and I had with our Bushveld hosts since my first visit in 2006. That year Ed and I brought many gifts for the local landowners who allowed us access to their farms so that we could chisel away chunks of rock on their property. These gifts were mainly hats, t-shirts, and children’s toys. But when we asked what they would like us to bring on future trips they overwhelmingly answered “education.”
Back in New York City, at the American Museum of Natural History (AMNH), where Ed is a curator of the petrology collection, we worked with the education director, Maritza MacDonald, to plan the workshop we will hold in Pretoria next week–a collaboration between AMNH and the South African Agency for Science and Technology, funded in part by the National Science Foundation. The workshop has evolved substantially since then with help from three other New York City educators who will accompany us: Natasha Cooke-Nieves, Christopher Emdin, and Jay Holmes.
Right now we are busily boxing up our educational materials: books on coal and platinum, movies produced by the AMNH, maps, posters, and even a few New York City rocks—pieces of Manhattan schist and the Palisades Sill and even beach sand from Coney Island and Far Rockaway. We will use these samples to show the teachers how to make a “geological” map by collecting different rocks from nearby areas.
For the second half of our trip, Ed and I will drive to the eastern-most part of the Bushveld Complex, approximately 2.5 hours away. We are investigating how this huge amount of magma rose from Earth’s mantle into the crust more than two billion years ago and how it cooled and solidified to become what it is today.
I’m preparing for this leg of the journey by studying geological maps of the area, like the one pictured above. Because the Bushveld is so old and has had so much time to erode away, we need precise geological maps to tell us where we might find the rocks at the surface today. The map above will tell us where we can find samples of the Bushveld Complex (the green) and also Bushveld-related lavas (the red, pink, and yellow). The white stickers on the map represent samples collected by others in the past. But I will tell you more about that in the coming posts.