Hyner View, Clinton County
Location: Clinton County, Glen Union and Renova East quadrangles; approximately 39º 52' latitude and 77º 37' longitude.
Size: Hyner View State Park is six acres in size.
Geology: The landscape seen when looking from Hyner View State Park in Clinton County, Pennsylvania is typical of the Deep Valleys Section of the Appalachian Plateaus Physiographic Province. The Section is composed of deep, narrow, steep-sloped valleys that are sometimes separated by narrow uplands. These upland surfaces have an accordance of elevation that is more illusive than real. For example, in Scene 1 the uplands, which are underlain by 350+ million year old sandstones, have upper surface elevations of 1,900-2,000 feet close to Hyner View and decrease in elevation slowly to the south so that the most distant uplands are 600-700 feet lower in elevation. In Scene 4 the uplands decrease in elevation slowly to the west and then increase so that the most distant uplands are 100-200 feet higher than those at Hyner View.
The valley below (Scenes 1, 2, and 4) is occupied by the West Branch Susquehanna River, flowing in Scene 1 at an elevation of 600 feet and in Scene 4 at 620 feet. In Scene 1 the visible meander bends are part of the natural forces working to lower the elevation of the landscape. Where the upstream end and the middle part of each meander bend impinges against a hillside, the river erodes the base of the hillside and the hillside gradually becomes very steep. The slopes of the meander-bend hillsides here are about 60 percent (vertical distance/horizontal distance) and are susceptible to landslides. The furrows that run from the hilltop to the river are places where landslides have occurred and rock debris has been carried rapidly down the hillside to the river. The slope opposite the steep slope is quite gentle. This is because river erosion has been less vigorous there and the gentle slope is created as the river cuts down and laterally into the opposite hillside. In a sense the river is sliding down one slope into the other.
Scenes 2 and 3 show different aspects of geology and erosion in the area. Although it is difficult to detect in these photographs, there is a difference in the slopes of the hillsides. The upper slopes approach 60 percent while the middle and lower slopes are about 45 percent. These differences occur because of differences in the hardness and resistance to erosion of the underlying nearly flat-lying rocks: the harder the rock, the steeper the slope. In Scene 2 note the narrow ridge in the center of the Scene. It appears to consist of a series of steps. Each higher step is underlain by a slightly harder sandstone and this difference is emphasized by the erosion.
Scene 3 centers on the valley of Big McCloskey Run with Schoolhouse Hollow on the left and Little McCloskey Run on the right. Elevations of the skyline are 2,100-2,200 feet. The lowest elevations of Big McCloskey Run visible here are about 800 feet. Note the sharp, very narrow ridge crests that occur on both sides of Big McCloskey Run (similar ridge crests occur in Scene 2). The sharp ridge crests are underlain by resistant sandstone. As the ridge crest gets closer to the viewer, they lose their sharpness, become rounded, and their hillside slopes flatten. This is because the resistant sandstone has been eroded away and erosion is now working on softer rock that does not support the steeper slopes. Erosion of these ridges is by hillslope processes of landslide, surface flow of rainwater and snowmelt, and slow, gravity-driven creep. As long as these processes remain uniform on both sides of the ridge, the ridges will be gradually reduced in height while the crests retain their positions. The form of the ridges will change as the crests round and the slopes flatten. The process is called downwasting.
In Scene 4 Hyner, in the right foreground, and the very straight railroad and highway (PA Route 120) leading to the west are on an alluvial plain formed by debris being brought into the river by Hyner Run and Dry Run. Sediment accumulations at water level in the river identify the mouths of these streams (Hyner Run passes under where the railroad and highway come together to run parallel and Dry Run is just west of the large open field west of Hyner Run). The accumulated debris from these tributaries has forced the river to bend south and it is cutting into the base of the hillside on the south side of the river. A similar situation occurs just east of North Bend where debris from Caldwell Run on the south has accumulated in an alluvial fan and has forced the river to the north bank. Here, in order to accommodate both railroad and highway, a large roadcut has been made in red rocks of the Upper Devonian Catskill Formation. This roadcut is the site of a now famous collecting locality for fish fossils.
In contrast are the slopes below the skyline. Here thick, resistant sandstone underlies a relatively flat upland that is 500-1,000 feet wide. The same hillslope processes of erosion are working here, but their effect is entirely on the hillside while little or no erosion occurs on the upland. The result is that the upland surface remains the same in form and elevation while the hillside is eroded into the margin of the upland, that is, in a direction away from the viewer, and the width of the upland is gradually narrowed. This process is called slope retreat.
Photos are by PaGS staff geologist, Tom McElroy.
Heritage value: Site is scenic and educational.
Heritage status: Site is secure as part of the state park.
How to get there: Visit the Hyner View State Park web page of DCNR.
Facilities: Visit the Hyner View State Park web page of DCNR.
For information regarding geologic features and PNHP, contact Jim Shaulis of the Pennsylvania Geological Survey at 717–702–2037.