Misplaced Pages

#773226

19-519: Sideling Hill is a syncline mountain , in a region of downward-folded ( synclinal ) rock strata between two upfolded anticlines . The ridge is capped by an erosion-resistant conglomerate and sandstone of Mississippian (early Carboniferous ) geologic age, the Purslane Sandstone of the Pocono Formation . The ridge's slopes are formed of much more easily eroded kinds of rock, including

38-417: A national historical park , and the former Western Maryland Railroad (now a rail trail ). Syncline In structural geology , a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria ) is a large syncline with superimposed smaller folds. Synclines are typically

57-484: A tunnel through Sideling Hill in 1873–1874 as part of its mainline construction. The tunnel predates the South Pennsylvania Railroad tunnel construction 11 miles (18 km) to the south by eight years. The tunnel is single-tracked, and curved at each end. It originally had a stone portal on its eastern (RR North) end and a natural stone portal at its western (RR South) end, but about 1919 the north portal

76-410: A downward fold ( synform ), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline). On a geologic map, synclines are recognized as a sequence of rock layers , with the youngest at the fold's center or hinge and with a reverse sequence of the same rock layers on the opposite side of the hinge. If

95-617: A tunnel was partially bored through the mountain by the South Pennsylvania Railroad . The railroad project ceased, and the tunnel was left abandoned. When construction of the Pennsylvania Turnpike was begun in the 1930s by the Pennsylvania Turnpike Commission on the right-of-way of the South Pennsylvania Railroad, the tunnel was completed for highway use by the turnpike. The tunnel, the longest of

114-593: The Devonian - Mississippian Rockwell Formation , underlying the Mississippian Purslane Sandstone . A highway rest stop, located near the eastern side of the Sideling Hill Road Cut on I-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. The rest stop formerly included

133-489: The Devonian - Mississippian Rockwell Formation , with long, narrow valleys paralleling the ridge on either side. Most of the crest of Sideling Hill is forested, primarily with various deciduous tree species such as oaks ( Quercus ) and hickories ( Carya ) , along with occasional evergreen pines ( Pinus ) . Only a few major highways, one active railroad and two former ones, and one former canal cross this steep mountain ridge. The East Broad Top Railroad constructed

152-590: The environment in South Western and South Central Pennsylvania , covering Bedford , Blair , Cambria , Fulton , Huntingdon , and Somerset counties. The SAC has many projects in preserving the environment in South Western and South Central PA, the most notable include converting the Abandoned Pennsylvania Turnpike (which the SAC bought from the Pennsylvania Turnpike Commission in 2001 for $ 1) into

171-523: The Hancock Museum in nearby Hancock, Maryland . The former exhibit center building was reopened as a welcome center on October 9, 2015. Only part of the facility is open, with the former exhibit center exhibits remaining at the Hancock Museum. Before construction of I-68, US 40 (now US 40 Scenic) , the National Road , crossed Sideling Hill with a steep grade on each side and a sharp hairpin turn at

190-504: The Sideling Hill Exhibit Center, a four-level geological museum and travel information center which opened in 1991. Due to state budget cuts, this facility was closed on August 15, 2009, as part of a $ 280 million budget reduction package, saving the state about $ 110,000 annually. Before its closing, the center served about 95,000 visitors a year. Many of the geological exhibits from the former Exhibit Center are now displayed at

209-515: The Sideling Hill bypass opened on November 26, 1968, and the former alignment through the tunnels became known as the Abandoned Pennsylvania Turnpike . A rest area next to the ridge was a stop on Bill Clinton and Al Gore's post-convention bus tour in 1992. The Sideling Hill Tunnel , through Sideling Hill in Pennsylvania east of Breezewood , is currently in its third phase of life. In the 1880s,

SECTION 10

#1732856198774

228-584: The adjacent hills. The Sideling Hill Tunnel and the nearby Rays Hill tunnel, along with connecting segments of four-lane highway, were used for many years as a testing facility for new highway technologies. In 2001, the Sideling Hill Tunnel was sold to the Southern Alleghenies Conservancy for $ 1, which now operates it as a bike trail. The Sideling Hill Road Cut on I-68 and US 40 is a 340-foot-deep (100 m) notch excavated from

247-568: The crest of the mountain. The water gap cut through Sideling Hill by the Potomac River southwest (upstream) of Hancock, Maryland , provides a low-level crossing of the ridge for the CSX Railroad , formerly the main line of the Baltimore and Ohio (B&O) Railroad , on the southern (West Virginia) side of the river, and on the northern (Maryland) side, the former Chesapeake and Ohio Canal , now

266-402: The doors were equipped with remote actuators mounted on poles a few hundred feet before each portal. This allowed the crews to open and close the doors without stopping. The system did not work flawlessly and a door was ripped off by a caboose cupola. The tunnel was in service from 1874 until the railroad ceased operations in 1956. The line is technically out of service (but not abandoned), and

285-422: The fold pattern is circular or elongate, the structure is a basin . Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. This article about structural geology is a stub . You can help Misplaced Pages by expanding it . Southern Alleghenies Conservancy Southern Alleghenies Conservancy is a non-profit nature group preserving

304-794: The ridge of Sideling Hill, about five miles (8.0 km) west of Hancock in Washington County, Maryland . Blasting was completed in August 1984. It is notable as an impressive man-made mountain pass, visible from miles away, and is considered to be one of the best rock exposures in Maryland and the entire northeastern United States. Almost 810 feet (250 m) of strata in a tightly folded syncline are exposed in this road cut. Although other exposures may surpass Sideling Hill in either thickness of exposed strata or in quality of geologic structure, few can equal its combination of both. The exposed rocks consist of

323-507: The seven original turnpike tunnels at 6,782 feet (2,067 m) long, was used from the turnpike's opening in 1940 until 1968. Due to increasing traffic on the highway, the turnpike commission began upgrading all of its two-lane tunnels, constructing twin bores for its tunnels through the Allegheny, Tuscarora, Kittatinny, and Blue mountains, and bypassing the tunnels under Laurel Hill, Rays Hill, and Sideling Hill with new, six-lane highways climbing

342-467: The track is still in place through the tunnel, although not serviceable. The tunnel and rail line are private property and not open to the public. The Pennsylvania Turnpike ( Interstate 76 , I-76) crosses Sideling Hill east of Breezewood, Pennsylvania , bypassing the two-lane Sideling Hill Tunnel and the nearby Rays Hill Tunnel that were formerly used by the Turnpike. Completed at a cost of $ 17,203,000,

361-455: Was replaced with a concrete one. The north portal was equipped with doors to prevent wind from blowing through the tunnel as the wind caused water percolating into the tunnel to freeze on the tracks in the winter. In 1911, this ice caused the brand new locomotive #12 to derail its pilot axle inside the tunnel then derail the entire locomotive at the Kimmel switch just beyond the tunnel. In the 1940s,

#773226