Sideling Hill

Sideling Hill

SIDELING HILL also known as SIDE LONG HILL is a long, steep, narrow mountain ridge in the RIDGE-&-VALLEY (or ALLEGHENY Mountains) physiographic province of the Appalachian Mountains located in Washington County in western Maryland and adjacent West Virginia and Pennsylvania, USA.  The highest point on the ridge is Fisher Point, at 2,310ft in Fulton County, Pennsylvania.

It is a SYNCLINE Mountain, in a region of “downward folded” ( a fold in which the strata on either side dip inward towards the axis) rock strata between two “upward folded” ANTICLINES.  The ridge is capped by an erosion-resistant conglomerate and sandstone of early CARBONIFEROUS geologic age, the PURSLANE sandstone of the POCON formation.  The ridge’s slopes are formed much more easily eroded kinds of rock, including the DEVONIAN-MISSISSIPPIAN Rockwell Formation, with long, narrow valleys paralleling the ridge on either side.  This topographic inversion, in which the “structural low” becomes a “topographic high”, is also seen at Town Hall, the next major ridge to the west and a structural twin to SIDELING HILL.

Sideling hill tunnel

The Rockwell Formations were deposited during the early MISSISSIPIAN, about 330 – 345 million years ago.  At the road-cut, approximately 450ft of the Rockwell Formation are exposed and consist of inter-bedded tan and grey-green, clay-rich sandstones, grey-green to dark-grey shales and grey to dark-grey sandy siltstones.  In places, thin shaly coals are inter-bedded with shales and siltstones.  An even rarer and indeed unusual lithology —— termed DIAMICTITE——– is present approximately 70ft above the base.  A DIAMICTITE is a very poorly sorted to under-sorted rock composed of clay, silt, sand, pebbles or cobbles.

Sideling Hill natural folds

Most of the crest of SIDELING HILL is forested primarily with various deciduous-leafed species such as oaks and hickories, along with occasional evergreen pines.  A highway rest-stop, located near the astern side of  Sideling Hill road-cut on Interstate 68 west of Hancock, includes a pedestrian-bridge crossing I -68, connecting the eastbound and westbound rest areas and offering views of the cut, in which stopping is prohibited.

Sideling Hill tunnel new

The rest stop formerly included the Sideling Hill Exhibit Centre, a 4-level geological museum and travel information centre which opened in 1991.  Due to state budget cuts, this facility was closed on August 15, 2009, saving the state about $110,000 annually.  Before its closing, the centre served about 95,000 visitors a year, at a cost of about $1.16 per visitor.


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