The early geologic history of Calvin Coolidge State Forest Park is known from the rock formations discussed in the previous section of this pamphlet. The Pinney Hollow, Ottauquechee, Bethel and Missisquoi formations of Cambrian and Ordovician age were deposited, essentially horizontally, from the shallow seas which covered this area 550 to 450 million years ago (See cross section A, Fig. 5). During some of this time these seas were at least partially restricted as evidenced by the Ottauquechee and Missisquoi black phyllites. Other Ordovician formations were deposited on top of these four formations, but have been completely stripped away by erosion during the millions of years since their deposition. Some of these later Ordovician sediments contain great thicknesses of volcanic rocks which probably covered the Coolidge Park area. Sometime after these later Ordovician rocks formed, great stresses within the earth’s crust folded and in some places faulted these older rocks. The pressure and resultant heat created during these earth movements converted the rocks into metamorphic schists, phyllites and quartzites which are seen today (See cross section B, Fig. 5). Exactly when these diastropic events took place is still open to question, but they probably occurred near the end of Ordovician time or perhaps millions of years later during the last phases of the Devonian Period. Probably since late Paleozoic time the Coolidge Park area has been subjected to breaking-down rather than building-up processes. Eventually this whole region was reduced to a flat plane with only a few hills, called monadnocks, rising above the general flatness of the landscape. Still later in the history of Coolidge State Forest Park this flat plane was lifted high above its former position and streams began to shape the land into its present form. The more resistant rocks were lowered by the forces of erosion at a much slower rate than the less resistant types. The hills and valleys which you see today are primarily the result of this general uplift followed by the wearing away of the softer rocks at a more rapid rate than the harder rock types. Since the formations trend in a north-north-west direction, the hills and valleys are also oriented in this general direction, as the different resistive qualities of the rocks are presented in this pattern.