This booklet could not have been prepared without the cooperation and assistance of many individuals and organizations. We are indebted to the National Park Service for the use of facilities, equipment, and photographs, and for the enthusiasm and interest of all of the park staff. We especially appreciate the cooperation, advice, and assistance rendered by the late Fred C. Fagergren, former superintendent of Grand Teton National Park; Willard E. Dilley, former chief park naturalist; and R. Alan Mebane, former assistant chief park naturalist. Profs. Charles C. Bradley and John Montagne of Montana State University and Bruno J. Giletti of Brown University generously provided us with unpublished data. Cooperators during the years of background research were the late Dr. H. D. Thomas, State Geologist of Wyoming, and Dr. D. L. Blackstone, Jr., Chairman, Department of Geology, University of Wyoming. Helpful suggestions were made by many of our colleagues with the U. S. Geological Survey; S. S. Oriel, in particular, gave unstintingly of his time and talents in the review and revision of an early version of the manuscript. A later version had the further benefit of critical review by three other people, all experienced in presenting various types of scientific data to public groups: John M. Good, former chief park naturalist of Yellowstone National Park; Bryan Harry, former assistant chief park naturalist of Grand Teton National Park; and Richard Klinck, “1965 National Teacher of the Year.” We are indebted to Ann C. Christiansen, Geologic Map Editor, for advice and guidance on the illustrations and to R. C. Fuhrmann and his staff for preparation of many of the line drawings. Block diagrams and photo artwork were prepared by J. R. Stacy and R. A. Reilly. All photographs without specific credit lines are by the authors. From the beginning of the Teton field study to editing and proofing of the final manuscript, our wives, Jane M. Love and Linda H. Reed, have been enthusiastic and indispensable participants. Selected references—if you wish to read further