We have seen in Chapter 5 that an eastward widening oceanic gap existed between Eurasia and the Gondwana continents in a Pangea configuration. This ocean is called the Tethys. In post-Triassic time, when the Gondwana continents dispersed and the Atlantic Ocean began opening, the Tethys Ocean gradually began closing. As the Gondwana continents collided with Eurasia in Tertiary times (Africa–Arabia against southern Europe, Turkey and Iran; India against Tibet; and Australia against Indonesia), the resulting orogenic belts formed some of the most impressive mountain ranges of the world, such as the Alps and the Himalayas.

The overall orogenic belt, marking the closure of the Tethys, is one of extreme complexity. Rather than a simple belt of continent–continent collision, it includes ancient microplates and displaced terranes, upthrusted oceanic remnants (ophiolites), successor ocean basins, and plutonic/volcanic complexes related to multiple subduction zones. On the northern side, this broad zone contains mountain belts ranging from the Pyrenees in the west through the Alps, Carpathians, the Caucasus, and on to the Tien Shan and Far Eastern mountain ranges in Asia (Figure 7.1). These belts form the deformed southern margin of the Eurasian continent. On the southern side, one finds the Betic Cordillera in Spain, the Riff, Tell and Atlas Mountains in northwest Africa, the thrust belt of Sicily and the mainland Italian Apennines, Greece, the Taurides in Turkey, the Zagros Belt in Iran, the Oman mountains, the Salt Range in Pakistan, the Himalayas, Indo-China's mountain ranges in Burma, Thailand and Malaya, the western Indonesian (the Sunda Block) and eastern Indonesian tectonic zones, and New Guinea.