Geology and Ecosystem
The Pocumtuck Range is composed of Sugarloaf arkose, a weather resistant sedimentary rock capped in places by a thin ridge of volcanic trap rock. The arkose is most apparent on Sugarloaf Mountain and the western cliff of Pocumtuck Ridge, while the trap rock is most apparent on the north and east side of Pocumtuck Ridge and throughout the summit ridge of Rocky Mountain in Greenfield. The range is a non-contiguous extension of the Metacomet Ridge that extends through New England from Long Island Sound to the Vermont border. The Pocumtuck Range forms the bottom and middle layers of a geologic layercake. The arkose is the oldest (bottom) layer, followed by the middle trap rock layer, which in turn gives way to a conglomerate rock top layer most visible across the Connecticut River as Mount Toby. These layers were formed between 190 to 210 million years ago as the continent of North America began rifting apart from Africa and Eurasia. A series of erosion and deposition (geology) episodes interspersed with heavy basalt lava flows created the layered strata; faulting and earthquakes tilted the layers diagonally while subsequent erosion and glacial activity exposed the tilted "layers" of sandstone, basalt, and erosion-resistant conglomerate rock visible today.
The Pocumtuck Range hosts a combination of microclimate ecosystems unusual to the region. Eastern red cedar, a dry-loving species, clings to the barren edges of cliffs. Backslope plant communities tend to be similar to the adjacent upland plateaus and nearby Berkshires, containing species common to the northern hardwood and oak-hickory forest ecosystem types. Eastern hemlock crowds narrow ravines, blocking sunlight and creating damp, cooler growing conditions with associated cooler climate plant species. Talus slopes are especially rich in nutrients and support a number of calcium-loving plants uncommon in the region. Miles of cliffs make ideal raptor habitat, and the range is an important seasonal raptor migration corridor. Thirty-seven species of fern can be found on the range, making it one of the richest ecosystems of fern diversity in the Commonwealth of Massachusetts. The range also supports extensive populations of whorled pegonia, a plant on the Massachusetts Environmental Protection Agency's watch list.
The Massachusetts Audubon Society considers the Rocky Mountain section of Pocumtuck Ridge "exceptionally rich in its diversity of species, especially during migration. . .an important area for breeding birds, and wintering individuals."
Read more about this topic: Pocumtuck Range