Ardsley Wind Gap

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The SEPTA Ardsley station is located on the Ardsley Wind Gap floor and Jenkintown Road also crosses the Edge Hill Ridge at the Ardsley Wind Gap. The Ardsley Wind Gap is the deepest of three noticeable wind gaps or notches cut into the Wissahickon Creek-Tacony Creek drainage divide along the northeast oriented Edge Hill Ridge with the other two wind gaps being the Edge Hill and Seminary Wind Gaps, both located to the southwest of the Ardsley Wind Gap. The Ardsley Wind Gap floor elevation is 326 feet while the other two wind gaps had floor elevations of approximately 350 feet before being altered by railroad and highway construction. Edge Hill Ridge crest elevations vary but exceed 400 feet at numerous points. The region north of the Ardsley Wind Gap is drained today by west oriented Sandy Run, which joins south oriented Wissahickon Creek near Fort Washington. Wissahickon Creek is a Schuylkill River tributary. South of the Ardsley Wind Gap water today drains to south oriented Tacony Creek, which flows to the Delaware River and the Ardsley Wind Gap is located on the Schuylkill River-Delaware River drainage divide. While not as spectacular as wind gaps elsewhere in Pennsylvania the Ardsley Wind Gap provides important scientific information related to the origins of the Delaware River and Schuylkill River drainage basins.

Figure 1. Ardsley Wind Gap.

Figure 1. The Ardsley Wind Gap is located at the SEPTA Ardsley station (on the Warminster line) where Jenkintown Road crosses the southwest to northeast oriented Edge Hill Ridge (location number 1). The Edge Hill Ridge extends in a southwest direction from location 1 to locations 2 and 5. Location 2 is the Edge Hill Wind Gap where Limekiln Pike and the SEPTA Lansdale line cross Edge Hill Ridge and location 5 is the Seminary Wind Gap where route 309 and an abandoned railroad line cross Edge Hill Ridge. Tacony Creek flows in an east direction from its headwaters at location 3 to the Jenkintown Elbow of Capture at location 4 and then turns to flow in a south-southeast direction and eventually reach the southwest oriented Delaware River. Location 6 shows headwaters of a west oriented Wissahickon Creek tributary with water eventually reaching the Schuylkill River. United States Geological Survey map digitally presented using National Geographic TOPO software. 

The Ardsley Wind Gap is oriented in a northeast to southwest direction suggesting it was eroded by southwest oriented flow moving across the upper reaches of the present day Sandy Run drainage basin to reach what at that time was the deeper Tacony Creek drainage basin. Water would have flowed through the wind gap and then in a southwest direction along the route used by the SEPTA Warminster line between Ardsley and Glenside to enter a southeast oriented valley, now used by the SEPTA Lansdale Regional Rail line to reach the Edge Hill Wind Gap, and would have joined Tacony Creek near the Jenkintown Elbow of Capture. This route suggests the deep south-oriented Tacony Creek valley eroded headward from what was probably a newly eroded southwest oriented Delaware River valley to capture southwest oriented flow located just south northeast oriented Edge Hill Ridge. Headward erosion of the south oriented Tacony Creek valley was probably across multiple southwest-oriented flow channels such as might be found in a southwest oriented anastomosing channel complex.

At the time the south oriented Tacony Creek valley eroded headward into the Glenside-Ardsley-Edge Hill Ridge region the area north of the Edge Hill Ridge was higher in elevation than the present day Edge Hill Ridge crest elevation and southwest oriented flow was moving across that high-level surface. The Edge Hill Ridge is composed of erosion resistant rock and limited the ability of the deep south-oriented Tacony Creek valley to erode headward into the less erosion resistant bedrock located north and west of the ridge. Once the deep south oriented Wissahickon Creek valley had eroded its deep gorge across northwest Philadelphia southwest oriented flow to the newly eroded Wissahickon Creek valley was able to quickly erode the less erosion resistant rocks north and west of the Edge Hill Ridge and to behead south oriented channels leading to the newly eroded Tacony Creek valley. The greater Ardsley Wind Gap depth is probably due to the fact that southwest oriented flow moved through the Ardsley Wind Gap for a longer period of time than through the other two wind gaps (being the farthest from the Wissahickon Creek valley it took longer for the actively eroding Wissahickon Creek valley to capture southwest oriented flow reaching the Ardsley Wind Gap).

 

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