INTRODUCTION

YELLOWSTONE NATIONAL PARK

GEOGRAPHIC DESCRIPTION

Yellowstone, the largest of the national parks, with an area of approximately 3,500 square miles, is in the northwestern corner of Wyoming (Fig. 1), with narrow strips along its northern and western margins extending into the states of Montana and Idaho. The park is perhaps best known for its hot-water phenomena, there being more geysers here than in the rest of the world combined. As a wild animal sanctuary, Yellow-stone is second only to the great African preserves. The absence of roads and trails over the greater part of the area, and the dense forests (PL 1), make geologic exploration difficult.

With the exception of the Gallatin Range in the northwest, Yellowstone Park belongs in the Middle Rocky Mountain Province. The Gallatin Range is part of the Northern Rockies, and the Yellowstone River north of the park is the boundary between the two.

The park (Fig. 2) is essentially a vast forested lava plateau, 8,000 feet above sea level and surrounded on three sides by lofty mountains. The encircling highlands present a magnificent panorama of snow-clad summits towering from 10,000 feet to more than 13,000 feet above sea level. It is only on the west that the mountain border is lacking, and there, a short distance beyond the park boundary, the Yellowstone plateau drops abruptly a thousand feet to the Snake River Plains.

Thus, the high surface of the plateau is the floor of a partially closed basin. It is a . . .