The objectives of Reviews of Geophysics are to provide an overview of geophysics and the directions in which it is going and to serve as an integrating force in geophysics. Authorship is by invitation, but suggestions from readers and potential authors are welcome. Reviews of Geophysics distills and places in perspective previous scientific work in currently active subject areas of geophysics. Contributions evaluate overall progress in the field and cover all disciplines embraced by AGU.