Abstract This guidebook provides detailed itineraries of three of the geological field trips related to the 2017 joint meeting of the GSA Northeastern and North-Central Sections in Pittsburgh. The first chapter outlines a walking trip of downtown Pittsburgh and the escarpment to its south, consisting of seven “Pitt stops” investigating geological, archaeological, and historical aspects of the Gateway to the West. Venturing further afield, the second chapter describes a trip that explores periglacial features as far as the Upper Youghiogheny River basin in Maryland and the Laurel Highlands of Pennsylvania. The third chapter investigates hydrologic aspects of the 1889 Johnstown, Pennsylvania, flood, largely following the progress of the flood from its point of origin to the city of Johnstown.

Abstract This guidebook chapter outlines a walking tour that provides an introduction to the geological, archaeological, and historical setting of Pittsburgh, with an emphasis on the use of local and imported geologic materials and resources in the eighteenth and nineteenth centuries. The focus is on downtown Pittsburgh, the low-lying triangle of land where the Monongahela and Allegheny Rivers join to form the Ohio River, and Coal Hill (Mount Washington), the escarpment along the Monongahela River to its south. Topics include the importance of—and concomitant effect of—historic coal use; use of local and imported geologic materials, including dimension stone used for buildings and gravestones, and chert used for gunflints and millstones; the frontier forts built at the site; and the ubiquitous landslides along Coal Hill.

Abstract During the Pleistocene, the Laurentian Ice Sheet extended southward into western Pennsylvania. This field trip identifies a number of periglacial features from the Pittsburgh Low Plateau section to the Allegheny Mountain section of the Appalachian Plateaus Province that formed near the Pleistocene ice sheet front. Evidence of Pleistocene periglacial climate in this area includes glacial lake deposits in the Monongahela River valley near Morgantown, West Virginia, and Sphagnum peat bogs, rock cities, and patterned ground in plateau areas surrounding the Upper Youghiogheny River basin in Garrett County, Maryland, and the Laurel Highlands of Somerset County, Pennsylvania. In the high lying basins of the Allegheny Mountains, Pleistocene peat bogs still harbor species characteristic of more northerly latitudes due to local frost pocket conditions.

Abstract Johnstown, Pennsylvania, has long been associated with flooding due to major floods in 1889, 1936, and 1977. The most famous of these floods, the Johnstown Flood of 1889, led to more than 2200 deaths and was the result of the catastrophic collapse of the South Fork Dam. This privately owned dam was located on the South Fork of the Little Conemaugh River, ~14 mi (23 km) upstream of Johnstown. The dam changed ownership multiple times since its initial construction and had been improperly rebuilt and maintained after partial breaches. It was the final failure after a wet spring and heavy rainfall that resulted in death and devastation along the Little Conemaugh River valley from South Fork to Johnstown. This field guide presents the history of the South Fork Dam and incorporates recent studies that examined the timing of the flood and failure of the dam itself. The field trip begins at the origin of the flood at the South Fork Dam and largely follows the path of the flood down the valley to Johnstown with stops at sites impacted by the flood wave, as well as sites that demonstrate a response to the flood.

Abstract Western Pennsylvania is rich in oil history, and many of the fledgling petroleum industry’s “firsts” happened right here between the late nineteenth and early twentieth centuries. First and foremost, it is home to the Drake Well, the first-ever economic well intentionally drilled to produce oil. In addition, western Pennsylvania has bragging rights to various industry advancements, from the way geologic samples were collected and interpreted, to how wells were drilled and stimulated for production, to early oil refining techniques, marketing, and production. In this field guide, we discuss the petroleum geology and history of western Pennsylvania in general and three important oil-producing sites in particular: (1) the McClintock #1 Well, Rouseville; (2) the Drake Well, Titusville; and (3) Muddy Creek oil field, Prospect. Each of these sites produced oil from Upper Devonian reservoirs and spurred additional petroleum exploration and development in the central Appalachian basin. This field trip generally follows the GSA guide published from the 2011 Joint Meeting of the GSA Northeastern and North-Central Sections in Pittsburgh (available at http://fieldguides.gsapubs.org/ ): Carter, K.M., and Flaherty, K.J., 2011, The old, the crude, and the muddy: Oil history in western Pennsylvania, in Ruffolo, R.M., and Ciampaglio, C.N., eds., From the Shield to the Sea: Geological Field Trips from the 2011 Joint Meeting of the GSA Northeastern and North-Central Sections: Geological Society of America Field Guide 20, p. 169–185, doi:10.1130/2011.0020(08).