Black Moshannon State Park - Geology and Climate

Geology and Climate

The rocks underlying the Black Moshannon Creek drainage basin are primarily shale, sandstone, and coal. Three major rock formations are present in Black Moshannon State Park, all from the Carboniferous period. These sedimentary rocks formed in or near shallow seas roughly 300 to 350 million years ago. The Mississippian Burgoon Formation is composed of buff-colored sandstone and conglomerate. The late Mississippian Mauch Chunk Formation is formed with grayish-red shale, siltstone, sandstone, and conglomerate. The third is the early Pennsylvanian Pottsville Formation, which is a gray conglomerate that may contain sandstone, siltstone, and shale, as well as anthracite coal.

The park is at an elevation of 1,919 feet (585 m) atop the Allegheny Plateau, just west of the Allegheny Front, a steep escarpment which rises 1,300 feet (400 m) in 4 miles (6.4 km), and marks the transition between the Ridge-and-Valley Appalachians to the east and the Allegheny Plateau to the west. The Allegheny Plateau and Appalachian mountains were all formed in the Alleghenian orogeny some 300 million years ago, when Gondwana (specifically what became Africa) and what became North America collided, forming Pangaea.

The lake within the park is at an elevation of about 1,900 feet (580 m), and the park itself sits in a natural basin. The basin and the underlying sandstone trap water and thus form the lake and surrounding bogs. The higher elevation leads to a cooler climate, and the basin helps trap denser, cooler air, leading to longer winters and milder summers.

The cooler climate also means the park is home to animals and plants typically found much further north. The Allegheny Plateau has a continental climate, with occasional severe low temperatures in winter and average daily temperature ranges of 20 °F (11 °C) in winter and 26 °F (14 °C) in summer. In 1972, long-term average monthly temperatures ranged from a high of 66.8 °F (19.3 °C) in July to a low of 26.2 °F (−3.2 °C) in January. The mean annual precipitation for the Black Moshannon Creek watershed is 40 to 42 inches (1016 to 1067 mm). The soil in the park is mostly derived from sandstone and as such does not have much capacity to neutralize acid rain. The highest recorded temperature at the park was 97 °F (36 °C) in 1988, and the record low was −25 °F (−32 °C) in 1994.