Harpur Pond Wetland complex
The extensive wetland system of about 30 acres that includes Harpur Pond is underlain by a layer of clay sediment several feet thick. The wetland was formed by poor drainage, caused by clay preventing water loss. The process of forming the clay took thousands of years during the last ice age which ended about 10,000 years ago. The Harpur Pond valley and was first formed when a glacier blocked outward drainage. Later, thick deposits of till left by the glacier continued the dam effect. Eventually the outlet eroded downward through the till, the lake disappeared, and the wetland resulted.
In 1962, the construction of a natural gas pipeline across the wetland created Harpur Pond, and the arrival of the beavers in the mid-1980s eventually ponded up water to almost the extent, if not the depth, of the former glacial lake. When the beavers leave, this will revert to a forested wetland.
Evidence of the geological history can be seen at the end of Lehigh Avenue where a footbridge to Stair Park crosses Fuller Hollow Creek. Where the creek cuts down to the bedrock, deep layers of glacial till can be seen.
Fuller Hollow Creek
Before 1960, Fuller Hollow Creek, which the Nature Preserve drains into, flowed with natural twists and turns down to the Susquehanna River, approximately a mile downstream. Then the development of the Stair Park subdivision altered the natural course of the stream by straightening it to create more house lots adjacent to the stream. At the same time the creation of extensive non-absorbing surfaces from roofs, roads, and driveways meant that more water ran more quickly into the stream. The stream thus rose higher and more quickly in heavy rains. Since the stream had been straightened, it could no longer dissipate energy in meandering. Two things happened. The stream cut deeper and it also cut into its banks to reestablish its meanders. The latter is unacceptable as it means property loss from undercut and collapsing banks but the laws of physics are irrevocable and the stream bank cutting slowly advances in spite of the efforts of home owners to stop it. The deep cuts just below the bridge over Washington St. by the back entrance to campus show the many layers of till laid down during the last ice age.
Newing Woods and the CIW knoll
There are some interesting and important differences on campus in subsurface geology. The flat forested land along Fuller Hollow creek east of Newing College consists of flood plain sediments laid down on top of glacial till that is mostly gravel, which has created a fairly well drained soil. This flatter land has usually been developed in this area, as evidenced by the campus playing fields and athletic facilities which have been built atop similar soils. Such well drained and fertile soils used to be mostly farmed but now their fertility has been largely lost to development, which is much easier here than on hilly upland sites.
Behind CIW and extending east and south is a gentle knoll that extends to the wetland on the south. This knoll is basically a mound of glacial till. Much of the rock here was transported from many miles to the north, as it is very different than our shale bedrock.
Hilly Slopes
The hilly land on the southern half of the University lands is also underlain by till but this is mostly local shale that was only moved a relatively short distance. In some places (Bunn Hill Creek ravine) there are conspicuous outcroppings where this rock is exposed at the surface.
Bunn Hill Creek Ravine
On the west side of Bunn Hill Road and north of Dodd Road is a spectacularly picturesque ravine through which Bunn Hill Creek flows. The stream has not been altered and in its upper reaches it flows over shale bedrock in a series of waterfalls that have created small plunge pools. Because most of the watershed is still forested and undeveloped, water quality is very high and the stream flow is much more even than the heavily urbanized Fuller Hollow Creek. A visit to both streams in a heavy rainstorm will provide abundant evidence of the value of forested watersheds in preventing flooding.
Information courtesy of John Rayburn of the 黑料视频 Geology department, An Integrated Hydrogeologic and Geophysical Study of the 黑料视频 Nature Preserve, a masters thesis by Daniel Patrick Michaud, and the late Richard Andrus