Modern glaciers
About a dozen small rapidly dwindling glaciers exist today in shaded reentrants high in the Teton Range. They are probably vestiges of ice masses built up since the climatic optimum, during the so-called “Little Ice Age.” These glaciers, while insignificant compared to those still present in many other mountain ranges, are fascinating working models of the great ice streams that shaped the Tetons during Pleistocene time.
The Teton Glacier ([fig. 6]) is one of the best known. It is an ice body about 3,500 feet long and 1,100 feet wide that lies at the head of Glacier Gulch, shaded by the encircling ridges of the Grand Teton, Mount Owen, and Mount Teewinot. Ice in the central part is moving at a rate of more than 30 feet a year.
THE PRESENT AND THE FUTURE
The geologic story of the Teton country from the time the earth was new to the present day has been summarized. What can we learn from it? We become aware that events recorded in the rocks are not a chaotic jumble of random accidents but came in an orderly, logical succession. We see the majestic parade of life evolving from simple to complex types, overcoming all natural disasters, and adapting to ever-changing environments. We can only speculate as to the motivating force that launched this fascinating geologic and biologic venture and what the ultimate goal may be. New facts and new ideas are added to the story each year, but many unknown chapters remain to be studied; these offer an irresistible, continuing challenge to inquisitive minds, strong bodies, and restless, adventurous spirits.
Most geologic processes that developed the Teton landscape have been beneficial to man; a few have interfered with his activities, cost him money, time, effort, and on occasion, his life. Postglacial faulting and tilting along the southern margin of Grand Teton National Park diverted drainage systems (such as Flat Creek, southwest of the Flat Creek fault on the south edge of the [geologic map]), raised hills, dropped valleys, and made steep slopes unstable. Flood-control engineers wage a never-ending struggle to keep the Snake River from shifting to the west side of Jackson Hole as the valley tilts westward in response to movement along the Teton fault. Each highway into Jackson Hole has been blocked by a landslide at one time or another and maintenance of roads across slide areas requires much ingenuity. We see one slide (the Gros Ventre) that blocked a river; larger slides have occurred in the past, and more can be expected. Abundant fresh fault scarps are a constant reminder that public buildings, campgrounds, dams, and roads need to be designed to withstand the effects of earthquakes. Some of these problems have geologic solutions; others can be avoided or minimized as further study increases our understanding of this region.
Man appeared during the last one-fiftieth of an inch on our yardstick of time gone by. In this short span he has had more impact on the earth and its inhabitants than any other form of life. Will he use wisely the lessons of the past as a guide while he writes his record on the yardstick of the future?
APPENDIX
Acknowledgements
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.