|
|
A Brief Geological History
Harpur Pond Wetland complex
The extensive wetland system of about 30 acres that includes Harpur
Pond is underlain by an even layer of mostly clay sediment several feet
thick. The clay prevents water loss through the bottom and has created
the poor drainage that has formed the wetland. For such a clay layer to
have formed it had to have settled out in of a body of standing water
into the which particles slowly eroded from the surrounding shale
bedrock. The process took thousands of years during the last ice age
which ended about 10,000 years ago. A glacial lake occupied the Harpur
Pond valley and was first formed when the glacier itself blocked the
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.
About 1962 the construction of a natural gas pipeline across the
wetland at about the same location as the current boardwalk created
Harpur Pond (before this there was a forested wetland where the pond
is) and the arrival of the beavers in the mid 1980's eventually ponded
up water to almost the extent, if not the depth, of the former glacial
lake. When the beavers leave, this will again 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 in order 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. The till consists mostly of
varying layers of clay and gravel.
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 many feet deep. 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 Ck. ravine) there
are conspicuous outcroppings where this rock is exposed at the surface.
Bunn Hill Creek Ravine
On the west side of Bunn Hill Rd. and north of Dodd Rd. 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 Ck. 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 Binghamton University Geology department, An
Integrated Hydrogeologic and Geophysical Study of the Binghamton
University Nature Preserve, a masters thesis by Daniel
Patrick Michaud, and Dr.
Richard Andrus
|
|
|
|
