Digging your way out of a problem
The largest man-made hole in Africa, the Palabora copper mine (left), located 360km northeast of Pretoria, South Africa, and its problematic ground subsidence, will now be monitored with an innovative deformation-measuring method.
The pit was developed into an underground mine in 2002. Though excavations are being carried out more than a kilometre underground, surface instabilities have caused more than 60 million tonnes of debris from the north wall of the pit to collapse.
The mine's owner, Rio Tinto, concerned about the threat to the infrastructure posed by the pit's east rim, hired international engineering firm AMEC to evaluate the problem. Working with the European Space Agency, AMEC tested a new technique known as Synthetic Aperture Radar Interferometry (InSAR).
Through InSAR, multiple satellite radar images of the same site can be combined to highlight slight changes in surface elevation that occur between the image acquisitions.