PIRE-AfricaArray Project Components
Research / Education and Outreach
In this project we are addressing a first-order Earth Science question that cannot be answered without strong intellectual collaboration and partnerships between scientists in the U.S. and Africa and their respective institutions: “What is the structure and origin of the African Superplume?” The African Superplume is a large region of low seismic wave speeds in the lower mantle under southern Africa that has long been recognized as one of the most prominent features in the mantle. Seismic wave speeds within the Superplume are typically a few percent lower than average, and the anomalous seismic structure extends upward from the core mantle boundary to at least 1500 km. Above the African Superplume lies the African Superswell, which encompasses much of eastern Africa, southern Africa, and the southeastern Atlantic ocean basin. The uplift, volcanism, and rifting that define the African Superswell suggest a geodynamic link between lower mantle dynamics and geologic processes shaping the African plate.
It is well established that two major components of Earth’s heat engine are convection within the mantle and the motion of tectonic plates, and while the Theory of Plate Tectonics, which revolutionized the Earth Sciences in the 1960’s, describes how lithospheric plates translate horizontally across Earth’s surface, it does not explain the dynamics of mantle convection. Some 40 years after the Plate Tectonics revolution, there still remain many outstanding questions about the modes and scale of convection in the mantle. Characterizing the structure of one of the largest mantle upwellings (i.e., the African Superplume) and investigating its origin will lead to fundamental advances in our understanding of mantle dynamics and consequently the internal workings of Earth’s heat engine.
To address the structure and origin of the African Superplume, we will conduct a 4-year (2006-2010) passive seismic experiment comprised of broadband seismic stations in Uganda and Tanzania spaced about 100 km apart, and more widely spaced (>200 km) stations in Zambia, Malawi and Mozambique to collect new seismic data that sample a critical region in the mid-mantle where existing seismic images indicate there could be a connection between anomalous upper mantle under eastern Africa and anomalous lower mantle beneath central and southern Africa. Establishing an unambiguous connection between upper and lower mantle structure would place first order constraints on the origin of the Superplume by pointing to a buoyancy source near the core-mantle boundary. Data from widely spaced permanent AfricaArray seismic stations in eastern and southern Africa will supplement the data collected from the seismic experiment and will provide broader constraints on structure within and surrounding the Superplume.
Several proven modeling methods, as well as some methods recently developed, will be applied to the seismic data to image the Superplume. These include improving existing global and regional P and S body wave and surface wave tomographic images of mantle structure, modeling teleseismic P and S waveforms, stacking and modeling receiver functions, jointly inverting receiver functions with surface wave dispersion measurements, using shear wave splitting and surface wave dispersion measurements to constrain mantle anisotropy, and modeling waveforms from regional and local earthquakes.
Built around the core research program to image the seismic structure of the African Superplume is a multi-faceted educational and outreach effort that strives to catalyze a cultural change in U.S. institutions by promoting a new model for how U.S. institutions can effectively run international education and research projects that are truly collaborative and sustainable, and that also contribute to the development of a diverse workforce.
The basic elements of the model, as applied to this project are:
- Developing e-education and field courses linked to the research for undergraduates at U.S. minority-serving institutions and in Africa;
- Involving undergraduates in international field work;
- Requiring graduate students to:
- take a foreign language;
- spend one semester at a university in Africa; and
- develop tutorials covering a range of introductory geophysics topics for undergraduates
- Faculty visits to Africa for collaboration with their colleagues at African universities;
- Weekly U.S.-Africa web-conference seminars; and
- Setting up a public-private funding partnership that includes academic and government agencies in the U.S., Europe, and Africa, and multinational mining and petroleum companies.
Undergraduate students, particularly those from minority-serving institutions, will be offered opportunities to participate in field work in Africa and also to attend the AfricaArray geophysics field course in South Africa.
There are opportunities for graduate students to participate in all aspects of this project, and there are also opportunities for faculty to participate by:
- Helping to supervise undergraduate and graduate student projects;
- Teach the field course;
- Assist with field work and operating seismic stations in Africa; and
- Teach short courses at AfricaArray-affiliated universities in Africa.