YELLOWSTONE NATURE NOTES

INTRODUCTION

The 17th of August 1959 began as a typical day in Yellowstone National Park. Automobiles laden with vacationers from all parts of the United States passed steadily through the five entrances to the park, their occupants motivated by a strong desire to see and enjoy the marvels of nature that make this national park one of the wonders of the world.

By sunset 6,000 people had settled in the campgrounds, 8,000 had found lodging in the hotels and cabins. In addition some 4,000 employees of the concessioners and the National Park Service brought the population count to 18,000. It was a warm, clear moonlight night, unusually warm for this altitude, and as the evening activities ended, people wandered back to their quarters and prepared to settle down for the night. Little did they realize that events were taking place underground destined to make this a night to be remembered.

The Madison River, formed by the confluence of the Firehole and Gibbon Rivers, flows in a westerly direction out of Yellowstone Park toward the town of West Yellowstone, and then continues its journey in a northerly direction through Ennis, Montana, and on to its junction with the Missouri River. Twelve miles west of the park boundary an artificial dam impounds the waters to create Hebgen Lake and the shores of the lake and canyon are dotted with resorts, cabins, and campgrounds. For many of the inhabitants of the Madison Canyon the night of August 17th was to be a night of terror bringing death to nine and leaving at this date some 19 still considered missing.

At 11:37 P.M. M.S.T. a sudden displacement of rock occurred along a fault at a depth of ten miles beneath the earth's surface at 44° 50' N. Latitude and 111° 05' W. Longitude. Shortly following this displacement these events occurred in rapid succession. An estimated 43.4 million cubic yards of rock slid as a unit into the Madison Canyon burying the road and river under several hundred feet of rubble for a distance of a mile impounding the waters of the Madison River to create a second lake below Hebgen Dam. Hebgen Lake basin was tilted causing the south side to rise and the north side to depress resulting in oscillations of the lake surface that caused it to crest the dam four times and kept the surface in motion for a period of 11 hours.

Within the park rockslides buried many sections of the roads, buildings were damaged at Old Faithful and at Mammoth Hot Springs, and 298 geysers and hot springs erupted, 160 of which had no previous record of eruption. Nature was on a rampage and man's faith in terra firma was suddenly put to the supreme test.

As shock waves radiated out from the center of disturbance they were felt throughout an area of 500,000 square miles and recorded at seismograph stations around the world.

This earthquake with a magnitude of 7.1 on the Richter Scale has been equaled or exceeded only 14 times within recorded history in the United States.

The geologic phenomena of earthquakes, landslides, and volcanoes excite the layman and scientist alike because these are examples of dynamic earth processes. Within a matter of minutes more geologic changes occurred than would normally happen in several thousand years.