Reprinted 1979
Reprinted 1984
Reprinted 1989

Grand Teton Natural History Association
Moose, Wyoming 83012

CONTENTS

[Foreword] 6 [THE STORY BEGINS] 8 [First questions, brief answers] 9 [An extraordinary story] 10 [An astronaut’s view] 12 [A pilot’s view] 14 [A motorist’s view] 15 [View north] 15 [View west] 18 [View south] 19 [A mountaineer’s view] 20 [CARVING THE RUGGED PEAKS] 24 [Steep mountain slopes—the perpetual battleground] 24 [Rock disintegration and gravitational movement] 24 [Running water cuts and carries] 26 [Glaciers scour and transport] 28 [Effects on Jackson Hole] 30 [MOUNTAIN UPLIFT] 36 [Kinds of mountains] 36 [Anatomy of faults] 38 [Time and rate of uplift] 40 [Why are mountains here?] 41 [The restless land] 43 [ENORMOUS TIME AND DYNAMIC EARTH] 45 [Framework of time] 45 [Rocks and relative age] 45 [Fossils and geologic time] 46 [Radioactive clocks] 47 [The yardstick of geologic time] 48 [PRECAMBRIAN ROCKS—THE CORE OF THE TETONS] 51 [Ancient gneisses and schists] 51 [Granite and pegmatite] 55 [Black dikes] 58 [Quartzite] 63 [A backward glance] 64 [The close of the Precambrian—end of the beginning] 64 [THE PALEOZOIC ERA—TIME OF LONG-VANISHED SEAS AND THE DEVELOPMENT OF LIFE] 66 [The Paleozoic sequence] 66 [Alaska Basin—site of an outstanding rock and fossil record] 66 [Advance and retreat of Cambrian seas; an example] 69 [Younger Paleozoic formations] 74 [THE MESOZOIC—ERA OF TRANSITION] 79 [Colorful first Mesozoic strata] 79 [Drab Cretaceous strata] 81 [Birth of the Rocky Mountains] 82 [TERTIARY—TIME OF MAMMALS, MOUNTAINS, LAKES, AND VOLCANOES] 86 [Rise and burial of mountains] 88 [The first big lake] 92 [Development of mammals] 95 [Volcanoes] 98 [QUATERNARY—TIME OF ICE, MORE LAKES, AND CONTINUED CRUSTAL DISTURBANCE] 102 [Hoback normal fault] 103 [Volcanic activity] 103 [Preglacial lakes] 104 [The Ice Age] 105 [Modern glaciers] 112 [THE PRESENT AND THE FUTURE] 113 [APPENDIX] 115 [Acknowledgements] 115 [Selected references—if you wish to read further] 116 [About the authors] 117 [Index of selected terms and features] 118

FOREWORD

Geology is the science of the Earth—the study of the forces, processes, and past life that not only shape our land but influence our daily lives and our Nation’s welfare. This booklet, prepared by two members of the U.S. Geological Survey, discusses how geologic phenomena are responsible for the magnificent scenery of the Teton region.

Recognition of the complex geologic history of our Earth is vital to the enjoyment and appreciation of beautiful landscapes and other natural wonders, to the planning of our cities and highway systems, to the wise use of our water supplies, to the study of earthquake and landslide areas, to the never-ending search for new mineral deposits, and to the conservation and development of our known natural resources. Who can say, in the long run, which of the many uses of this knowledge is the most compelling reason to seek an understanding of the Earth?

W. T. Pecora, Director
U.S. Geological Survey

This booklet is based on geologic investigations by the
U. S. Geological Survey in cooperation with the National Park Service,
U. S. Department of Interior.