East Mountain is a traprock mountain ridge located in the Connecticut River Valley of Massachusetts. It is part of the narrow, linear Metacomet Ridge that extends from Long Island Sound near New Haven, Connecticut, north through the Connecticut River Valley of Massachusetts to the Vermont border. East Mountain is known for its extensive scenic cliffs, unique microclimate ecosystems, and rare plant communities. It is traversed by the Metacomet-Monadnock Trail. Geography East Mountain rises steeply between above the Connecticut River and Westfield River valleys below; it is roughly long and wide at its widest point, although the steepness of the terrain makes the actual square mileage much larger. The mountain includes many crests and tiered ridges, with a high point of above sea level. Various lakes, ponds and reservoirs are located on it, including Snake Pond, a mountaintop kettle pond. East Mountain extends from the Westfield River on the tri-border of Westfield, West Springfield, and Agawam, Massachusetts to the base of Mount Tom in Holyoke; it lies within the towns of Holyoke, Westfield, West Springfield. The Metacomet Ridge continues north as the Mount Tom Range and south across the Westfield River as Provin Mountain. The west and south sides of the mountain drain into the Westfield River, thence to the Connecticut River and Long Island Sound; the north and east sides of the mountain drain into the Connecticut River. Because the mountain is an important regional aquifer, numerous reservoirs have been constructed on it slopes; these facilities provide drinking water and emergency drinking water to surrounding towns and cities. They include Bearhole Reservoir, McLean Reservoir (formerly called High Service Reservoir), and Ashley Reservoir. Geology and ecology East Mountain, like much of the Metacomet Ridge, is composed of basalt, also called traprock, a volcanic rock. The mountain formed near the end of the Triassic Period with the rifting apart of the North American continent from Africa and Eurasia. Lava welled up from the rift and solidified into sheets of strata hundreds of feet thick. Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of East Mountain. Hot, dry upper slopes, cool, moist ravines, and mineral-rich ledges of basalt talus produce a combination of microclimate ecosystems on the mountain that support plant and animal species uncommon in greater Massachusetts. East Mountain is also an important raptor migration path. (See Metacomet Ridge for more information on the geology and ecosystem