The position of the Green Mountains is a function of the structure of the rocks and their resistance to erosion. At the same time that the mica-albite-quartz schist was being developed under conditions of heat and pressure the region was tightly folded by the same forces. It is likely that this folding continued after the metamorphism during the declining stages of mountain-making. This period of mountain-building probably raised the rocks to a higher level but it was the later repeated uplifts and erosion of the overlying rocks which finally produced the present mountain topography. It is postulated that the folding and crumpling of the schists were accompanied by a westward movement of large masses of rock. That is, segments of the earth’s crust are believed to have been pushed westward by pressure from the east. Thus, it is believed by many geologists that the rock which now occurs in the Green Mountains may have been derived in early times from an area ten to forty miles to the east. The basic structure of the Green Mountains is an anticlinorium, a large complex fold. An _anticline_ is an upward fold in which individual rock layers if traced through the _structure_ have a shape similar to that of an arch; the opposite structure is a syncline in which the individual layers are shaped like a trough or basin. An _anticlinorium_ is a large anticline upon which are superimposed many smaller anticlines and synclines. Figure 3 is a diagrammatic sketch showing the relation of the topography to the structure of the rocks in the Mount Mansfield area. The structure of the rocks is reflected in the topography of Mount Mansfield, but such correspondence is not necessary, for the form of any hill or mountain is a function of its erosional history and resistance of the rock to erosion. In some folded areas, the rock in the trough of a syncline is so resistant to erosion, that it persists in hills or mountains after neighboring anticlines have been more deeply eroded to form valleys. [Illustration: Figure 3. Diagrammatic sketch showing the relation between the topography and the structure of the Green Mountains in the Mount Mansfield area. The section has been drawn to approximately pass through The Chin, Smugglers Notch, Spruce Peak and Sterling Pond, and looking N 20° W.] THE CHIN SMUGGLERS NOTCH SPRUCE PEAK STERLING POND