The timing of magma appearing in Gondwana rift systems is remarkable. In the Ferrar magma was not emplaced in the middle of the rift, as might be expected, but into the rift shoulder. And this apparently happened rapidly, perhaps taking only a few 100,000 years, and this rapidity may also be common to the Eastern North American system (ENA), but the emplacement pattern was in striking contrast. The ENA dolerites came late in the rifting sequence, after more than 5 km of sediment had already filled the developing rift, and the dolerites are not tightly tied to the rift faulting itself. And these sediments were not generally highly consolidated, so the ENA dolerites formed bulbous, irregular bodies at high levels in the system. The Ferrar sills are, in comparison, highly regular, reflecting the well consolidated section of sediments characterized by the Beacon Supergroup. This also suggests that this crustal section was not a normal rift, filled with a thick section of still-compacting sediments, but instead a mature section of continental crust.