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Since 1964 there have been six earthquakes of Mw ≥ 5.5 in east Africa whose centroid depths have been demonstrated to be in the range of 25–40 km. These depths are significantly greater than the 5‐ to 15‐km range typical of most other regions of continental extension. The March 10, 1989 earthquake (Mw 6.1) in Malaŵi is the first such deep event to have occurred within the main topographic expression of the late Cenozoic east African rift system. Its focal mechanism and depth (32 ± 5 km) allow it to be plausibly associated with slip on a deep part of a major normal fault zone bounding the Malaŵi rift. We cannot determine whether the earthquake occurred in the crust or mantle or whether the postulated fault zone exists as a continuous seismogenic surface from the upper crust to depths of ∼30 km: it is possible that the fault zone exists as an aseismic shear zone in the lower crust. In the Malaŵi rift the width of the half graben (up to 50 km), the effective elastic thickness of the lithosphere (∼35 km), and probably the largest fault segment lengths (>50 km) are greater than is typical in rifts outside Africa. We suggest that these features and the greater earthquake depths are all related to the likelihood that the upper part of the lithosphere is colder and stronger than is typical elsewhere. These observations are consistent with earlier suggestions that normal faulting and significant strength can exist throughout the bulk of the crustal thickness. If this is the case, wide half graben can form without requiring shear strengths on the bounding faults to be greater than 1–10 MPa (10–100 bars), which is the typical level of stress drop observed in earthquakes.

We show that intraplate magmatism occurred 1106 to 1112 million years ago over an area of two million square kilometers within the Kalahari craton of southern Africa, during the same magnetic polarity chron as voluminous magmatism within the cratonic core of North America. These contemporaneous magmatic events occurred while the Rodinia supercontinent was being assembled and are inferred to be parts of a single large igneous province emplaced across the two cratons. Widespread intraplate magmatism during Rodinia assembly shows that mantle upwellings required to generate such provinces may occur independently of the supercontinent cycle.

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The physiography of southern Africa comprises a narrow coastal plain, separated from an inland plateau by a horseshoe‐shaped escarpment. The interior of the inland plateau is a sedimentary basin. The drainage network of southern Africa is characterized by three river divides, broadly parallel to the coastline. These features contrast strongly with the broad dome and radial drainage patterns predicted by models which ascribe the physiography of southern Africa to uplift over a deep mantle plume. The drainage divides are interpreted as axes of epeirogenic uplift. The ages of these axes, which young from the margin to the interior, correlate closely with major reorganizations of spreading regimes in the oceanic ridges surrounding southern Africa, suggesting an origin from stresses related to plate motion. Successive epeirogenic uplifts of southern Africa on the axes, forming the major river divides, initiated cyclic episodes of denudation, which are coeval with erosion surfaces recognized elsewhere across Africa.

The Northern Marginal Zone of the Limpopo Belt in southern Africa comprises a Plutonic Assemblage of granitoids including a distinctive suite of porphyroclastic granites. and a much less abundant Supracrustal Assemblage of metabasites and iron formations. These rocks are at granulite facies above a normal thickness of continental crust. Most of the Plutonic Assemblage are intrusive rocks that crystallized from dry melts from 2800 to 2 6 0 Ma, with a relatively simple thermal history. They may have been derived from partial melting of a mafic source. Some supracrustal rocks have experienced two thermal events at granulite facies.A reverse-sense shear zone forms the boundary of the Northern Marginal Zone with the Zimbabwe craton. The southern boundary is the Triangle shear zone, which is proven as a continuous structure along a much greater strike length than previously documented. A widespread sub-vertical foliation in the Northern Marginal Zone and the reverse shear zone formed during progressive NNW-SSE shortening. Crustal thickening occurred both magmatically and tectonically in the late Archaean, and was accompanied by synchronous uplift. Protracted magmatism provides a mechanism to incorporate supracrustal rocks into the lower crust, and can explain the occurrence of more than a single thermal event.

Archean ultramafic-mafic complexes have been the focus of important and often contentious geological and geodynamic interpretations. However, their age relative to the other components of Archean cratons are often poorly-constrained, introducing significant ambiguity when interpreting their origin and geodynamic significance. The Lewisian Gneiss Complex (LGC) of the northwest Scottish mainland -a high-grade, tonalite-trondhjemite-granodiorite (TTG) terrane that forms part of the North Atlantic Craton (NAC) -contains a number of ultramafic-mafic complexes whose origin and geodynamic significance have remained enigmatic since they were first described. Previous studies have interpreted these complexes as representing a wide-range of geological environments, from oceanic crust, to the sagducted remnants of Archean greenstone belts. These interpretations, which are often critically dependent upon the ages of the complexes relative to the surrounding rocks, have disparate implications for Archean geodynamic regimes (in the NAC and globally). Most previous authors have inferred that the ultramafic-mafic complexes of the LGC pre-date the TTG magmas. This fundamental age relationship is re-evaluated in this investigation through re-mapping of the Geodh' nan Sgadan Complex (where tonalitic gneiss reportedly cross-cuts mafic rocks) and new mapping of the 7 km 2 Ben Strome Complex (the largest ultramafic-mafic complex in the LGC), alongside detailed petrography and spinel mineral chemistry. This new study reveals that, despite their close proximity in the LGC (12 km), the Ben Strome and Geodh' nan Sgadan Complexes are petrogenetically unrelated, indicating that the LGC (and thus NAC) records multiple temporally and/or petrogenetically distinct phases of ultramafic-mafic Archean magmatism that has been masked by subsequent high-grade metamorphism. Moreover, field observations and spinel mineral chemistry demonstrate that the Ben Strome Complex represents a layered intrusion that was emplaced into a TTG-dominated crust. Further to representing a significant re-evaluation of theLGC's magmatic evolution, these findings have important implications for the methodologies utilised in deciphering the origin of Archean ultramafic-mafic complexes globally, where material suitable for dating is often unavailable and field relationships are commonly ambiguous.