The largest discrete structure in the Earth's interior, known as the African superplume, has been found beneath southern Africa within the outer layer known as the mantle. The mantle, comprising solid but flexible rock about 3000 km (1800 mi) thick, is where the flow associated with plate tectonics occurs. While it is not certain what the African superplume is exactly, it may be a giant upwelling of mantle material. Southern Africa's high topography and unusual land surface are indicative of uplift that may be dynamically supported by this rising superplume. This interpretation is qualitatively consistent with a range of observations showing that Africa is experiencing active intraplate volcanism and rifting, as well as with seismic and other quantitative evidence of anomalous mantle features below the continent.