Allegheny River Headwaters Watershed Conservation Plan

Allegheny River Headwaters Conservation Plan
Chapter 2. Land Resources
CHAPTER 2. LAND RESOURCES
Geology
Geology is the science that deals with the study of the earth, its history, its natural processes and
products. Geologic investigations of an area yield insight into the land’s history, composition, structure,
and natural resources. The landscape reflects millions of years of natural events. Forces acting on the land
surface have had varying effects, resulting in a vast array of landscapes.
Geology influences various attributes of watersheds. For example, the presence or absence of a
species in a region relies on geology, climate, and soil type. Even the path and flow of waterways have
been determined by geology. Physiographic provinces and ecological sub-regions have related geology
and frequently overlap.
More than 300 million years ago, the entire Allegheny headwaters region was covered with sandy,
silty, clayey, limy sediment and organic material. The elevation of the region was raised, causing extreme
pressure and weight on the sediments. Over a long period of time, the sediments consolidated into layers
of sandstone, siltstone, shale, limestone, and coal. The subsequent years of uplifting, subsiding, erosion,
and stream cutting has changed the surface of this plateau into highly dissected, rolling, hilly terrain.
Approximately 23,000 years ago, a major glacier covered the Oswayo valley and blocked the flow of
the Allegheny River north of the project area, causing many valleys to partially fill with gravel, sand, and
silt that washed from the surrounding hills. Therefore, the bedrock formations were nearly level with
gently sloping synclines and anticlines that trend southwest and northeast (Churchill, 1987).
Physiographic Provinces
Geologists have divided the earth into physiographic provinces, which categorize landscapes and
landforms with similar features. A physiographic province is a region containing similar terrain shaped
by geologic history.
The entire project area is located within the Appalachian Plateau physiographic province. The
Appalachian Plateau Province is subdivided into 10 sections, two of which are located within the
headwaters region of the Allegheny River. The majority of the area is
located within the Deep Valleys Section, while a small portion in the
northwestern corner of Potter County is located within the Glaciated
High Plateau Section.
The Deep Valley Section is characterized by very deep, angular
valleys and some broad to narrow uplands. Drainage is angulated or
rectangular, resulting in tributaries having sharp bends and entering
the mainstem at abrupt angles. Local relief—difference in elevation
between two points—varies from 301 feet to more than 1,000 feet.
Elevations range from 560–2,560 feet (Sevon, 2000).
Angular drainage pattern
The Glaciated High Plateau Section is located in a small portion
of the watershed, in the northwestern corner of Potter County near the
Borough of Shinglehouse. This section contains broad to narrow, rounded to flat, elongated uplands and
shallow valleys. Drainage within this section varies from angulated to dendritic—branching—patterns.
The local relief varies from 101–1,000 feet.
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