Vast regions of the Islamic world frequently experienced earthquakes during both medieval and modern times. The main zones of high seismicity within the Islamic heartlands have been areas such as the Red Sea, the valley of the Jordan, and the Anatolian fault zone, which are situated on the borders between the Eurasian plates to the north and various plates to the south (most importantly the Arabian, the African, the Anatolian, and the West Iranian Plates). These zones display significant differences in their tectonic evolutions: whereas some are characterized by spreading and the formation of new oceanic crust (Red Sea), others are characterized by collision and subduction (Eastern Mediterranean). However, these regions have in common a long-standing history of active tectonic developments, and these have continued through the present. Alternatively, some regions (e.g., the Arabian Peninsula situated on the Arabian shield) belong, with the exception of Yemen and the Hejaz (incorporating Mecca and Medina), to the most seismically stable areas in the world. Although the inland of North Africa (the modern states of Egypt, Libya, and Sudan) is rather aseismic, it has been subject to infrequent earthquakes of considerable size.