subterranean bunker formerly occupied by the United States Air Force Strategic Air Command (SAC). The bunker was created to provide commanders of SAC at the Westover Air Force Base in Chicopee, Massachusetts shelter in the event of a Cold War-era nuclear weapons attack. The three story bunker features 3 foot (1 m) thick walls, a 1.5 foot (.5 m) thick steel blast door, and is located underground. Both the Holyoke Range and the Mount Tom Range were part of a 1966 proposal by the National Park Service for a "Connecticut River National Recreation Area." Although the project was never realized, it has been followed through in spirit by a number of similar local and national conservation efforts, including an increased effort to acquire land on both ranges for state park expansion, the creation by the Commonwealth of Massachusetts of the Connecticut River Greenway State Park,. On March 30, 2009 as part of U.S. Public Law 111-11 (Section 5202) the range's Metacomet-Monadnock Trail section was incorporated in the new National Scenic Trail called the New England Trail. See also the original National Park Service proposal and study. The Tofu Curtain The Holyoke Range has been nicknamed the Tofu Curtain as a divider between Hampshire and Hampden Counties. The nickname refers to a socioeconomic, cultural and sometimes political divide between the wealthier Hampshire County and its affluent Five College Consortium to the north and the working class Hampden County to the south, which comprises the cities of Holyoke and Springfield, as well as their surrounding towns and cities. While this southern part of the Massachusetts' Pioneer Valley is the second largest metropolitan region in the state, areas of it are economically depressed with Holyoke's average 2017 annual household income ranked at $14,000. Meanwhile, the towns of Northampton and Amherst to the north are home to many worker cooperatives and small businesses that often manufacture or sell natural products (such as tofu) to a more affluent population. Geology and environment The ridge of the Holyoke Range was formed 200 million years ago during the late Triassic and early Jurassic periods and is composed of traprock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile"