The Geology of Mount Blue State Park


Mount Blue State Park is located in the townships of Weld, Carthage, and Avon in Franklin County and is the third largest state park in Maine. It is easily accessible by automobile from State Highway 142. Though referred to as one park, Mount Blue State Park is in fact composed of three distinct, separate areas. The largest area contains Mount Blue itself, providing a climb to the top of the mountain by the Mount Blue Trail and a magnificent view from the fire tower on the summit. From the parking lot, the climb comprises a vertical ascent of 1800 feet and takes between one and two hours. The descent is accomplished in half that time. A cold brook offers a refreshing pause at an altitude of 2050 feet, approximately three-eighths of the way up the mountain. Another area of Mount Blue State Park contains Center Hill. There are picnic facilities at the edge of the parking lot, from which is also offered a superb panorama of the Tumbledown Mountain - Jackson Mountain - Blueberry Mountain range. A very short hike to the top of Center Hill will reward one with a splendid view of Lake Webb and the mountains to the south and west. The smallest area of Mount Blue State Park is on the west shore of Lake Webb. It offers a fine sandy beach, facilities for launching boats, and large tracts of land designed for tenting.

The purpose of this booklet is to give the visitor to Mount Blue State Park some idea of its geologic setting. What is meant by geology? Geology is the study of the earth, and especially of the matter that forms the surface of the earth. This matter is present in two distinct forms: as bedrock, that is attached to and thus part of the solid rocky crust of the earth; and as loose surficial material overlying the bedrock in the form of boulders, cobbles, gravel, sand and clay. The problems which arise in the study of these two distinct forms are so different that geology is divided into two main branches, bedrock geology and surficial geology.

A bedrock geologist attempts to find out how rocks were formed, what they are composed of, and how they got to be where they are now. All rocks fall into two basic types, igneous and sedimentary. Igneous rocks formed from molten matter, named magma or lava. The difference between these is that whereas magma solidified into rock below the surface of the earth, lava was extruded onto the surface before solidification. Sedimentary rocks formed either through accumulation of sediments such as sand and mud, or through precipitation of substances out of sea water, in which they were dissolved. The term metamorphic or metamorphosed denotes that a rock, whether of igneous or sedimentary origin, has been subjected to very high temperature and pressure, which caused a change in its form. Such changes are noted by growth of minerals which would not have been present in the original rock. Most of the rocks present within Mount Blue State Park are metamorphosed sedimentary rocks.

A surficial geologist studies the topographic features of the land and learns of the processes that shape the surface of the earth. Among other phenomena he concerns himself with the erosional work of glaciers and with the deposits that were left after the glaciers melted and disappeared.

Introduction   Geologic History   Objects of Interest   Glossary   Geologic Map (pdf)

Last updated on January 11, 2008