Examples of Philadelphia Area Gorges

· Brandywine Creek, Crum Creek, Crum Creek-Ridley Creek divide, East Brandywine Creek, gorges, landform inventories, Ridley Creek, Tohickon Creek, Valley Creek, Valley Creek
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  • Eric Clausen Website: http://geomorphology… At present I am a professor emeritus having taught geology at Minot State University (North Dakota, USA) from 1968 until 1997. I was trained in geology at Columbia University and the University of Wyoming where my studies emphasized regional geomorphology. For many years I have pursued a research interest that developed when as result of geologic field work and interpretation of large mosaics of detailed North American topographic maps I discovered significant evidence previous investigators had ignored. Over a period of many years, after studying such anomalous evidence, I was forced to develop a fundamentally different interpretation of North American geomorphic history than that which is generally accepted. Geomorphology is the study of landforms and my interest as a geomorphology researcher is in determining the origin of large drainage systems, such as the Missouri River drainage basin in North America. The Missouri River drainage basin consists of thousands of smaller drainage basins, each of which has a history my essays (website posts) are trying to unravel. What I try to do is reconstruct the landscape the way it looked prior to the present day drainage system. I then try to determine how the present day drainage system evolved. While conducting my Missouri River drainage basin landform origins study I also developed an interest in scientific paradigms, especially in how scientific paradigms develop and how they are replaced. The Missouri River drainage basin landform origins project at geomorphologyresearch.com has been completed and I am currently creating a catalog of Philadelphia, PA area erosional landforms, which can be found at phillylandforms.info For off site questions and discussions about either project I can be contacted at eric2clausen@gmail.com

While not usually described as gorges the Philadelphia area contains numerous narrow stream and river valleys which for all practical purposes should be called gorges. Most Philadelphia area gorges are 350 feet or less in depth and have been eroded into erosion resistant metamorphic and sedimentary rocks. Some Philadelphia area gorges now serve as major transportation routes while others are park areas and can be accessed by various types of hiking, horse, and bicycle trails. While well known and well mapped the geologic literature rarely provides details about how any of the Philadelphia gorges were formed. This lack of detailed information is because Philadelphia area gorges like other Philadelphia area erosional landform and drainage system features are anomalous evidence which the accepted geology and glacial history paradigm is unable to satisfactorily explain (see Clausen, 2024).

Before looking at the examples of Philadelphia area gorges it may be useful to show how how the west-flowing Niagara River (in figure 1 below) appears to be eroding the Niagara River gorge headward in a south-southwest direction. Most geological literature assumes Niagara Falls has been retreating toward Lake Erie since the last ice sheet retreated from the region. The abrupt Niagara River direction change at the Niagara Falls location is rarely mentioned may complicate the commonly held interpretation of how the Niagara Falls are eroding the gorge, but most geologists today would agree with an interpretation that the north-northeast-oriented Niagara River gorge was eroded in a headward direction as Niagara Falls have been retreating in a headward direction toward Lake Erie. The Niagara River gorge example suggests Philadelphia area gorges were also eroded in a headward direction, although the source of the water and the water flow direction required for that headward erosion is not obvious.

Figure 1. Google Earth view of the west-flowing Niagara River flowing over Niagara Falls to enter the 300-foot-deep north-northeast oriented Niagara River gorge, which is assumed to have been eroded headward since the retreat of the last continental ice sheet from the region.

One of the Philadelphia areas best known gorges is the Wissahickon Creek gorge which is carved into an erosion resistant metamorphic and sedimentary rock upland. The gorge is a popular park area located entirely within the City of Philadelphia and extends from the Chester Valley southward for almost seven miles to reach the Schuylkill River. Figure 2a uses a topographic map from the USGS National Map website to illustrate the middle section of the 300-foot deep or deeper Wissahickon Creek gorge while figure 2b uses a Google Earth image to show approximately the same area. Closely spaced contour lines indicate steep slopes found along the gorge walls. While there are differences probably resulting from different bedrock characteristics the Wissahickon gorge and the Niagara River gorge also have similarities. The Wissahickon gorge depth is almost the same as the Niagara River gorge depth and the Wissahickon gorge width could be considered to be similar to the Niagara River gorge width (although at its base the Wissahickon gorge is somewhat narrower). In many respects the Wissahickon Creek gorge illustrates what the Niagara River gorge looks like downstream from Niagara Falls, although Wissahickon Creek water flow is only a small fraction of the Niagara River water flow.

Figure 2a. Topographic map from the USGS National Map website showing the middle section of the Wissahickon Creek gorge, which is located entirely within the City of Philadelphia.

Figure 2b. Google Earth image of the same Wissahickon Creek gorge middle section shown on the figure 2a map. The forested gorge area is a Philadelphia city park.

Figure 3a is a topographic map showing how both Wissahickon Creek and the Schuylkill River flow from the Chester Valley to enter gorges carved across a metamorphic and sedimentary rock upland area which is located between the Chester Valley and the Delaware River valley. The Schuylkill River gorge is somewhat wider than the Wissahickon Creek gorge, but is just as deep as the Wissahickon Creek gorge and has many similarities with the Niagara River gorge downstream from Niagara Falls. The Wissahickon Creek and Schuylkill River gorges must have been eroded headward by huge amounts of water (as the Niagara River gorge is being eroded headward today), but unlike with the Niagara River gorge the water source and water flow direction are not obvious. Figure 3b is a Google Earth image illustrating the southeast-oriented Schuylkill River gorge, which today is a major transportation route used by an abandoned canal, a hiking and bicycle trail, a major highway, and two different railroads.

Figure 3a. Topographic map from the USGS National Map website showing how the Schuylkill River and Wissahickon Creek both flow from the Chester Valley to enter deep gorges cut into a metamorphic and sedimentary rock upland area before reaching the Delaware River valley.

Figure 3b. Google Earth image showing the northwestern section of southeast-oriented Schuylkill River gorge just upstream from its confluence with Wissahickon Creek and the City of Philadelphia.

Crum and Ridley Creeks as seen in figure 4 have carved two gorges almost adjacent to each other. The two creeks today originate in relatively small drainage areas to the north of the figure 4 map area and flow independently to join the Delaware River to the south of the figure area. The two gorges are not as deep as the Niagara River gorge but are carved in erosion resistant metamorphic and sedimentary bedrock. Interesting features seen in both gorges are entrenched meanders. The two gorges must have been eroded by much larger volumes of water than the upstream drainage areas of the two creeks can probably provide, but the water source and the water flow direction are not obvious.

Figure 4. Topographic map from the USGS National Map website showing the adjacent Crum and Ridley Creek gorges which are located in the western Philadelphia suburbs. These narrow gorges are not as deep as the Wissahickon Creek and Schuylkill River gorges, but otherwise are similar.

Interesting gorges almost as deep as the Niagara River gorge are found where the south-oriented East Branch of Brandywine Creek enters and then leaves the west-southwest trending Chester Valley and where Valley Creek (West) which is an East Branch Brandywine Creek tributary leaves the Chester Valley as seen in figure 5a. The East Branch of Brandywine Creek is just one of at least seven south-oriented drainage routes which originate to the north of the west-southwest trending Chester Valley and which then cross the deep Chester Valley without significantly changing their flow directions as they continue their southward flow. The Chester Valley floor is more easily eroded than its more erosion resistant north and south walls, but the Chester Valley like the 300-foot-deep East Branch Brandywine Creek and Valley Creek (West) gorges seen in figure 5a is also an erosional feature. Figuring out how running water was able to erode the East Branch Brandywine Creek gorges on either side of the Chester Valley (or vice versus) is an interesting puzzle that geologists rarely discuss or attempt to solve.

Figure 5a. Topographic map from the USGS National Map website showing East Branch Brandywine Creek gorges to the north and south of the Chester Valley and the Valley Creek (West) gorge to the south of the Chester Valley. How running water carved these gorges is an interesting puzzle.

Figure 5b. Google Earth image showing the south-oriented East Branch Brandywine Creek gorge as it enters the Chester Valley at Downingtown, PA.

Further from Philadelphia but still in the region, the Delaware River gorge upstream from Trenton, New Jersey as it flows along the present-day Bucks County (PA)-New Jersey border is just as deep if not deeper than the Niagara River gorge. Figure 6a uses a topographic map to illustrate the 300-foot deep or deeper narrow Delaware River valley just downstream from Point Pleasant, Pennsylvania (which is located where Tohickon Creek joins the Delaware River). Figure 6b uses a Google Earth image to illustrate the same Delaware River gorge area. This Delaware River gorge section like other Philadelphia area gorges (including those not illustrated here) appears to have been eroded headward in a manner similar to how the Niagara River gorge is being eroded headward today, although the water source and the water flow direction are not obvious from the information provided here.

Figure 6a. Topographic map from the USGS National Map website illustrating a section of the 350-foot deep Delaware River gorge located along the Pennsylvania-New Jersey border near Point Pleasant, Pennsylvania and about 40 miles to the northeast of Philadelphia.

Figure 6b. Google Earth image of the Delaware River gorge area illustrated in figure 6a.

Reference citation

Clausen, E., 2024, The Topographic Mystery: Geology’s Unrecognized Paradigm Problem: Revised Edition.Author’s Tranquility Press,159 pages.

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