Earth-Science Reviews publishes review papers of all aspects of Earth Sciences or treatises on an expanding Earth Sciences subject. Covering a much wider field than the usual specialist journals, it allows the readers to see their particular interest related to the earth sciences as a whole. Because of the breadth and depth of its approach to subjects of current interest, the journal is an important vehicle of information gathering for instructors; students; research scientists; government agencies involved in program support and management and in environmental assessment and control; private industries concerned with planetary resources and the independent consultant