Part of the active Cordillera Mountain Belt on the eastern margin of the Pacific Ocean, the Andes extend approximately 10 000 km from the Caribbean Sea to the Scotia Sea. They developed during the Mesozoic and Cenozoic eras, largely as a result of the subduction of normal oceanic lithosphere. Unlike the N. American Cordillera, very few allochthonous terranes have been recognized, and there have been no collisions of major continental masses as in the Himalayas. These differences have led to the concept of a distinctive ‘Andean-type orogeny’.