Published by the American Geophysical Union as part of the Geodynamics Series, Volume 18. The International Lithosphere Program (ILP) was established in 1981 to encourage interdisciplinary, international research on the nature, dynamics and origin of the lithosphere. To do this various working groups and coordinating comittees were set up to focus on specific aspects of ILP. The mandate of Working Group 2 (WG2), which was chaired by Rob Van der Voo of the University of Michigan, was "Phanerozoic plate motions and orogenesis."