Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the modern theories of sea-floor spreading, continental drift, and plate tectonics. Each module consists of two booklets: a teacher's guide and student investigation. The teacher's guide contains all of the information present in the student investigation booklet as well as: (1) a general introduction; (2) prerequisite student background; (3) objectives; (4) list of required materials; (5) background information; (6) suggested approach; (7) procedure, including number of 45-minute class periods required; (8) summary questions (with answers); (9) extension activities; and (10) list of references. Activities in this module focus on the nature and operation of isotasy (principle of buoyancy applied to solid materials of the earth's crust). Students identify conditions under which one substance floats in another substance, predict movement of earth's crust when material is added to or substracted from the crust, and predict relative thickness of crustal areas from average density and elevation data. (Author/JN)