In search of Africa's superplume

Africa Array's mission to revive African geophysics and advance understanding of the planet's thermal forces.

Credit: Penn StateCreative Commons

I am sitting in Andy Nyblade's office, with towering piles of papers around us and a diagram spread out on the desk.

"See this right here?" asks Nyblade, professor in Penn State's department of geosciences. He points to a drawing that shows a multicolored, cut-away view of the earth's layers. "The mantle is the earth's thick rocky interior," Nyblade explains. "What this model shows is that there's a large region of low seismic wave speeds beneath southern Africa, deep in the mantle. We call this region the African superplume."

Pointing to another diagram, he says, "During an earthquake, we can measure the speed at which seismic waves travel. The fact that waves travel one to two percent slower in this superplume region means the rock is hotter than normal."

Using mathematical algorithms similar to those used for medical imaging, geophysicists can convert seismic data into three-dimensional models. "In this way," Nyblade tells me, "we can image the interior of the earth. It's like a CT scan used to see inside a person, but in this case, the mantle is the body."

"And how is the body doing?" I ask.

"Well, its temperature is up about half a percent—meaning it's 250-350 degrees hotter than what we'd expect to find," he answers. Nyblade has a calm, soft-spoken demeanor, but there's unmistakable excitement behind his words.

"The superplume is a massive blob of hot rock pushing up beneath southern Africa," he explains. "Geophysicists theorize that as the superplume rises towards the surface, it may be pushing up much of southern Africa as it ascends. There are areas of uplift we believe are associated with this deep mantle structure," he continues. These surface manifestations include rifting, where the earth's crust and lithosphere pull apart, and volcanism, specifically the active volcanic region in northeastern Africa that includes the Continent's highest peaks, Mount Kilimanjaro and Mount Kenya.

"I've termed the entire area of anomalous topography the African superswell," says Nyblade. He pauses before adding, "It's huge—bigger than the lower 48 states. Underneath it is the superplume, the most enigmatic feature in the planet's mantle and possibly the oldest distinct structure on earth. We know they're linked but we don't fully understand how."

An ambitious initiative

Andy Nyblade, Professor in department of Geosciences at Penn State

Andy Nyblade testing seismic equipment in Tanzania.

Gaining a better understanding of the relationship between the African superplume and superswell is just one facet of the AfricaArray initiative, which Nyblade helped found and now co-directs. As its name suggests, AfricaArray has a complex and evolving mission to promote scientific research and training programs "in Africa, with Africans, for Africa" as Nyblade puts it.

Africa—the poorest of the earth's continents, beset by disease, famine and violence—was the home of 90 percent of the planet's gold before colonialism. Today, the continent's still-abundant natural resource sector (in particular, its petroleum, minerals and water) remains the driving force behind its economic development. As AfricaArray points out on its Web site, "Africa is a primary source of strategic and base metals for the world market. Petroleum production from sub-Saharan African countries alone may provide 25 percent of U.S. oil imports by 2015."

Despite these riches, if the continent doesn't have its own training programs and scientists who will stay and work in their home nations—"'brain drain' is a real problem" says Nyblade—it will be hampered in its ability to respond to development opportunities and channel profits back into its own economically marginalized countries.

In the fall of 2003, the effort to increase opportunities within Africa was much on Paul Dirks' mind. From his Johannesburg office, a hopeful Dirks made flight arrangements for Pennsylvania. Head of the geosciences department at University of the Witwatersrand (or 'Wits' as its known), Dirks had heard about Penn State's College of Earth and Mineral Sciences new Alliance for Earth Sciences, Engineering and Development in Africa (AESEDA), created to be an interdisciplinary hub for research, education, and outreach on georesources management for sustainable development in Africa. "I knew about Andy Nyblade and his long interest in Africa," Dirks reflects. "So I went to AESEDA's first symposium at Penn State with the specific intent to link up with Andy and explore the possibility of collaboration."

Nyblade adds, "Paul came here hoping to gain ideas and support. He told me 'Geophysics in Africa is dying.'" According to Dirks, Wits was the last stronghold for geophysics in Africa and the program was going downhill.

The crisis at Wits was part of a more endemic Catch-22: After a slump in the field during the 70s and 80s, the demand for African geophysicists was again increasing, particularly in oil-producing countries such as Algeria, Libya and Nigeria. Yet, as Nyblade explains, "What little capacity there is in Africa for geophysics training is disappearing fast, even though interest from students is high."

In Africa, the interplay between economics, mining, and geophysics is "a very complex issue with both national and international explanations," notes Dirks. "In the last twenty years, the mining industry has become increasingly shareholder-driven. Whenever commodity prices fall, the exploration activity in the mining industry gets cut drastically. The people in exploration are firstly geologists and geophysicists and they are the first to lose their jobs in a downturn."

Today, jobs are once again there to be filled: According to a recent survey of mining and oil companies, at least twenty new geophysics graduates are needed per year by African government agencies and industry, particularly in water resource development. "The oil and gas sector is also crying out for geoscientists," Dirks says. "There just isn't the academic infrastructure to supply the needed trained specialists." In fact, in a nation that is the world leader in mining geology, Wits is theonly remaining university in South Africa with a full geophysics program.

Strengthening African geoscience

Recalls Nyblade, himself a native of Tanzania, "After our initial meeting at the AESEDA symposium, Paul and I brainstormed a lot about this problem. I said 'Let's look at this in a bigger context. Let's not just think about rebuilding geophysics at Wits, let's try to do something on a larger scale for all of Africa.'"

The idea was hatched to put together an initiative that would encompass many universities across the continent—eleven institutions to date—and get scientists from different African nations working on an array of shared geoscience projects. Initially envisioned as a twenty-year project and funded through a private-public partnership of academic, government and industry organizations, AfricaArray was born in January of 2005. Its three founding partners—Wits, Penn State, and the Council for Geoscience (CGS) in Pretoria, South Africa—provided $1.7M in in-kind support at its launch.

Andy Nyblade in Africa

Nyblade inspects a seismic station in Cameroon.

AfricaArray's development plan includes three phases over the first decade. "The aim of the first three years is to build on existing programs and expertise within our partner institutions," explains Nyblade. "A primary focus is to rebuild the program at Wits and use that as a model to strengthen other geophysics programs throughout Africa."

As Nyblade points out, to create a viable training program at the master's and doctoral levels, you have to have a research infrastructure. That means you have to have good research projects for students, along with access to new and interesting data sets. "So how do you create all that?" he asks. "Well, I'm a seismologist and one way to do it is to develop a network of seismic stations to record earthquakes in Africa."

These stations—twenty-four now in place, primarily throughout eastern and southern Africa—serve many purposes: they provide data sets for students to use for their research projects; they form networks of shared scientific observatories, which help catalyze scientific community-building through educational and research collaborations; and they capture and interpret seismic data needed to better understand the African superplume.

"AfricaArray is truly an amalgamation of different projects," Nyblade says, "but the common thread is that students can work on African problems, in Africa, with African data sets."

The focus of these research projects is informed, in part, by the practical needs of different industries. For instance, remarks Nyblade, the diamond mining industry is primarily interested in the lithosphere—the rigid outer layer of the earth. "The lithosphere is thickest beneath the oldest parts of the continent and that's where you find diamonds," he explains. Seismic data can help map out those areas.

Another project involves the Bushveld complex in the northern part of South Africa, which holds the largest reserves of platinum in the world. "It's 400 km long and wide and 8-10 km deep. They're mining at the sides of this feature, but what's at the middle, they don't know. We're using seismic data to better understand what it looks like," Nyblade explains.

"I've been doing geophysical research in Africa for twenty years," he adds, "so I knew what many the issues and problems were. I thought these would be fundable scientific projects that would also attract funding from the National Science Foundation (NSF)."

Collaborating in the field

Undergraduate student collecting data in Africa

Undergraduate student Candra Gross collecting electrical resistivity data in South Africa.

The NSF has provided significant resources for AfricaArray, notably through a program called Partnerships for International Relationships in Education (PIRE), which funds American-based scientists seeking collaborative international research experience. PIRE has permitted AfricaArray to fund Penn State and African post-doctoral associates, graduate students and research associates to work on the program, and Nyblade is hoping to involve more Penn State scientists as the initiative evolves.

During the summer of 2007, PIRE enabled Penn State geoscience graduate students Angela Larson and Aubreya Adams to travel to Tanzania and Uganda for a month as part of a three year project aimed at better understanding the crustal and upper mantle structure of the Western branch of the Eastern African Rift (EAR) zone. Part of the Great Rift Valley—a fissure in the earth's crust that stretches 6,000 miles from Lebanon to Mozambique—the EAR's Western branch is characterized by a complicated succession of rift segments with an evolutionary history that remains the subject of intense debate.

While there, Larson and Adams will work alongside Fred Tugume and
Gabriel Daudi Mulibo to install twenty new broadband seismic stations. Tugume and Daudi Mulibo, from Uganda and Tanzania respectively, are currently getting their doctorates in geoscience from Penn State thanks to funding from AfricaArray.

One concern that the program's founders wanted to address from the outset was how to ensure that Africa and African institutions ultimately reaped the full benefit of the training afforded to Africans who come to the US as students and decide to settle here. In order to maximize the benefit to Africa, Nyblade set in place "a sandwich program," whereby African students could come to the U.S. and work with a supervisor for no more than six months out of twelve. "This past year, I brought in Fred and Gabriel," says Nyblade. "Fred works with the Uganda Geological Survey and Gabriel teachesat the University of Dar es Salaam in Tanzania. "They're absolutely intending to go back," Nyblade says, "and they'll spend a lot of time doing field work in their home countries, operating and maintaining the seismic stations, as part of their degree programs."

Tackling key questions

The majority of NSF's funding to AfricaArray is centered on imaging the African superplume. Remarks Nyblade, "The foundation recognizes that we are addressing a first-order Earth Science question, one that cannot be answered without strong intellectual collaboration and partnerships between scientists in the U.S. and Africa and their respectiveinstitutions. And that question is, 'What is the structure and origin of the African superplume?'"

The answer to this question will take time to reveal itself. As Nyblade remarks, geophysicists must measure progress on a different clock: "The mantle is convecting on a geological time scale," he explains, "so although over millions and millions of years the rock actually is moving like a fluid, in our lifetimes nothing is really moving."

Notes Nyblade, "We think our work may hold the key to understanding how the mantle works. "A lot of competing models have been put forward. This superplume-superswell structure—if it goes from the core all the way to the surface—argues for the theory that the whole mantle is circulating in one big

If this theory can be confirmed, he adds, it would advance the whole field of plate tectonics. "In the 60s," says Nyblade, "there was a revolution in our field when we finally understood that the earth's surface is broken into plates that translate horizontally across the surface. Yet forty years later, we still don't fully understand about the coupling between the plates or the process of convection—what is happening at the surface." And that, says Nyblade, is why AfricaArray has caught the attention of a lot of geoscientists, and why NSF has put a lot of money into it. "This project potentially holds the key to addressing a lot of uncertainty in our field."

Fulfilling their vision

Seismic Station in Africa

Inside a seismic station in Malawi. The small metal canister with blue wire is the ground motion sensor.

While the ultimate outcome of the scientific mission won't be clear for years to come, the immediate success of AfricaArray is easier to measure.

"We're ahead of schedule," Nyblade comments with pride. "We've already done all we hoped for in our first phase. Within two and a half years we've successfully rebuilt the geophysics department at Wits."

Affirms Dirks, "AfricaArray has given tremendous impetus in revitalizing our program." Since the initiative began, Wits has five times as many undergraduate students enrolled in the geophysics honors program and has almost tripled the number of students receiving master's degrees. AfricaArray's coupling of training and research, says Dirks, "has made high officials in the University and Government realize that geophysics needs to be supported more strongly." Looking ahead, Nyblade hopes to increase the number of permanent observatories and expand them to include sensors from other scientific fields. To this end, he has begun discussions about this with the Penn State Institutes of the Environment and Penn State's meteorology department.

Ultimately, agree Nyblade and Dirks, AfricaArray is the result of a shared vision that grew out of their first conversation four years ago—the hope that geoscience education and training for Africans could help combat disenfranchisement and empower Africa's citizens to take leadership
roles in an array of scientific fields vital to the development of the continent's vast and rich natural resources.

Andrew A. Nyblade, Ph.D., is professor of geosciences in the College of Earth and Mineral Sciences; Paul Dirks, Ph.D., is director of the School of Geosciences at the University of the Witwatersrand, Republic of South Africa;

Last Updated August 27, 2007