The Berkshires are characterized by varied topography and bedrock geology which in turn have contributed to the exquisite diversity of species and biotic communities. Environmental forces, including the role of human activities, have conspired to make the landscape of the Berkshires a mosaic of biological communities in a dynamic state of change: From most places in the Berkshire region one can sample biological communities that are typical of an area extending 1000 miles from central Canada to the mid-Atlantic states. The biological communities also vary in age from newly mown suburban lawns and cultivated farm fields to ancient woodlots and fragments of the pre-colonial forest.
Topography & Bedrock Geology
Envision the Berkshires as a broad, longitudinal valley forming a conduit for the Hoosic River in the north and the Housatonic River in the south. The valley is defined by the Taconic Range (ca. 2400’ above sea level) on the west, forming the boundaries between New York State and three states to the east: Vermont, Massachusetts, and Connecticut. The Taconics are comprised predominately of phyllite shist. The Hoosac Range, with a complex of phyllite, quartzite, and granitic bedrock, defines the eastern flank of the valley as its summits form the Berkshire Plateau, at around 2400’ in the north, decreasing to about 2000’ in the south. The Berkshire Plateau merges to the north with the granitic Green Mountains of Vermont. Mt. Greylock rises as a massif in the northern Massachusetts portion of the region. Its summit at 3491’ being the highest peak in Southern New England. While the geographic position of Mt. Greylock aligns with the Green Mountains to the north, its bedrock geology is more closely related to the Taconic Range to the west. The Hoosic-Housatonic valley bottom (ca. 700’ above sea level) is punctuated by marble hills rising to 1200’ or so.
The southern portion of the Berkshires is drained by the Housatonic River whose major branches arise on the southwestern flanks of Mt. Greylock and the east-central Berkshire plateau and converge in Pittsfield, MA. The Housatonic River then meanders through the broad valley of the southern Berkshires flowing south through Connecticut and eventually entering Long Island Sound. The North Branch of the Hoosic River flows south from Readsboro, VT to North Adams, MA where it joins the South Branch that originates in Lanesborough, MA. The Hoosic then flows west through Williamstown, MA, north into Pownal, VT and then north and west through eastern New York, entering the Hudson River at Stillwater, NY.
Pleistocene Geologic History.
During the peak of the most recent geologic epoch -- the Pleistocene -- some 18,000 years ago. the entire Berkshire region was covered by a kilometer-thick ice sheet that scoured out the U-shaped valley as it crept southward toward Long Island. As the ice sheet receeded northward through the region14,000 years ago, the Hoosic River valley below the1000’ elevation contour was filled by Lake Bascom as the glacier dammed up the melt water, preventing its drainage to the northwest. Lake Bascom persisted for about 800 years until it emptied toward the Hudson River in a series of dramatic flood events. Similarly, in the late Pleistocene Lake Ashley filled the Housatonic Valley from what now is Great Barrington, MA to Falls Village, CT.
The diversity of biological communities in the Berkshires is the product of the fortunate convergence of environmental variations, the human history of land-use, and regional species richness. The valley bottom has a great diversity of wetland types ranging from flowing and flooding rivers to ponds and lakes (many of which have been produced by human activities) to vegetative wetlands such as wet meadows, marshes, fens, swamps, and bogs. The uplands usually have boreal coniferous forest dominated by balsam fir above 3000’ and red spruce from 2400 – 3000’ above sea level. At lower elevations north- and east-facing slopes are inhabited by deciduous forests typically dominated by sugar maple, yellow birch, eastern hemlock, and beech. South- and west-facing slopes are generally dominated by deciduous oaks, hickories, and beech. The warmest and driest sites may have species such as pitch pine, sassafras, and chestnut oak that are typical of the Mid-Atlantic region. Underlying these generalities of biological community distribution are the interactions of the landscape with a rich land-use history dating back to the inhabitation of the region by Native Americans and the later advent of colonists of European extraction in the early 18th Century. During the 19th and early 20th centuries, much of the forest cover was converted to agricultural uses, and the vast majority of the residual forests were used as woodlots for timber, fuel, and other forest products. With the regional decline in agriculture and the dominance of a fossil fuel based economy in the 20th Century, forests commenced to reclaim much of the land that was previously cleared for agriculture. Residential and commercial developments are also important features of the post-agricultural landscape.
This Web Site.
This web site should be viewed as a series of field trips to the diverse sites in the Berkshire region. This site was established in 2005 to provide information to students enrolled in the Williams College course INTR 225 – Natural History of the Berkshires as well as the public at large. The initial web design has largely been the result of the creative genius of Benjamin J. Brooks ’08, Pamela C. Council ’07, and Jason C. Ren ’08.Henry W. Art