The South Iceland Seismic Zone is aligned E-W across the Southern Lowlands. The earthquake faults have N-S direction. So why is that? It can be easily explained according to the framework of mantle convection cells between the edge of the Western Volcanic Zone on one hand and the edge of the Eastern Volcanic Zone on the other. This leads to the fact you can almost use the system of faults as a compass! As convection takes place 120 km below the surface, the regularity found within the top 10 km of brittle crust is just amazing. The South Iceland Seismic Zone is one of the clearest manifestations of the mantle current system within the Earth.