The Geology of MT. MANSFIELD STATE FOREST _By_ ROBERT A. CHRISTMAN DEPARTMENT OF FOREST AND PARKS Perry H. Merrill, _Director_ VERMONT DEVELOPMENT COMMISSION VERMONT GEOLOGICAL SURVEY Charles G. Doll, _State Geologist_ 1956 [Illustration: Cover photo: Smugglers Notch looking northeast from the top of Mount Mansfield.] GEOLOGY OF MOUNT MANSFIELD STATE FOREST _By_ ROBERT A. CHRISTMAN INTRODUCTION Included within Mount Mansfield State Forest are Mount Mansfield, Smugglers Notch and a number of the mountains of the Green Mountain range to the northeast and southwest of these famous landmarks. Because much of the area is easily accessible by trails, ski lifts, and roads (see the index map of Figure 1), the visitor has ample opportunity to observe the minerals, rocks, and mountains. Undoubtedly, these observations have provoked questions which, for lack of sufficient information, have gone unanswered in the mind of the observer. In the hopes of remedying this situation—a very grievous situation in the eyes of a geologist—this brief geologic pamphlet has been written to help the visitor to the State Forest obtain a greater appreciation of the handiwork of nature. To begin with, _geology_ can be defined as the study of the history of the earth as recorded in the rocks. It includes the study of minerals, rocks, fossils, the structure of the rocks, and the forms of the land. Although only a few have been fortunate enough to choose this subject as a profession, the field is wide open for amateurs. This report is divided into four sections. The first describes the rocks; the second deals with the detailed structure of the rocks and the mountains; the third treats the glacial history of the area; and the fourth part describes the geology that may be seen at various localities within the park. DESCRIPTION OF THE ROCKS _Introduction_ With a few exceptions, the rock found in Mount Mansfield State Forest is a mica-albite-quartz schist. This name indicates that it is a metamorphic rock[1] of a particular composition and texture as described in the following paragraphs. The schist forms the cliffs at Smugglers Notch and the bare-rock faces exposed along the crests of the mountains and elsewhere. It varies slightly in appearance because of variation in the proportions of the different mineral constituents. [Illustration: Figure 1. Index mapping showing location of Mount Mansfield State Forest.] _Origin of the schist_