Coalition
Members

Apolacon Twp..
Bridgewater Twp.
Choconut Twp.
Forest Lake Twp.
Franklin Twp.
Jessup Twp.
Liberty Twp.
Middletown Twp.
Rush Twp.
Silver Lake Twp
Friendsville
Little Meadows
Montrose

II. THE PHYSIO-ECOLOGICAL LANDSCAPES

GEOLOGY

Geologic process and structure gave form to the landscape of the Northern Tier Coalition . They are also an important consideration in land use planning. For instance, rock characteristics such as depth to bedrock, estimates of volumes and direction of ground-water movement, location and depth to water table, strength of the rocks, degree of weathering, and composition of the rock are critical aspects to be considered in a foundation site evaluation. The direction and width of transportation systems, dams, industry, and buildings are influenced significantly by the bed rock conditions present in the area (Geyer and McGlade 1985). As a result, an understanding of geology can also be useful in guiding planning different types of development and long term management of extractive resources in a region.

The Coalition area is a part of the Glaciated Lower Plateau physical province of Pennsylvania (Figure 2.2 Pennsylvania Physical Provinces). The rocks that underlie the townships of the Northern Tier Coalition were formed about 375 million years ago during the Late Devonian-age and are primarily of the Catskill Formation (Inners et al.). The Catskill formation contains interbedded gray and red sandstone, siltstone, shale and mudstone in fining upward cycles. Lenticular calcitic “breccia” beds up to 2 ft thick, as well as cross beds, mudcracks, plant fossils, and fish bones can be found within the bedrock. Gray (and, locally, red) sandstones marketed as flagstone and dimension stone are the primary economic product derived from this formation. The rock is over 1,500 ft. thick in most areas and was deposited by meandering rivers (channels, floodplains and levees), and as beaches and shallow coastal bars.

More recently, the entirety of Susquehanna County was once covered by both the Illinoian and Wisconsin glaciers. The red line in Figure 2.2. is the northern most extent of the glacier’s advance in Pennsylvania. Deposits of glacial drift of variable thickness cover the whole county except where they have been removed by erosion. About 14 thousand years ago the last glacier passed through the region, deepening the stream valleys, carving out depression, and scraping away soils and existing vegetation, and leaving deposits of assorted rocks and gravels - especially in the valleys. These processes created the landforms found today in the Northern Coalition, such as the soft hills and u-shaped valleys that tend to run north and south. Many of the wetlands and beautiful lakes in the area also owe their origin to the glacial processes, especially kettle formation. Such headwater areas and alluvial valley bottoms are critical to surface water and aquifer recharge. Since the last ice age the soils and vegetation have been restored – but are still relatively young compared to those in southern PA, where the land did not experience glaciation (Barnes and Sevon, 1996; Susquehanna County Planning Commission, 1992).

TOPOGRAPHY

One direct product of the geologic processes is topography of the Coalition Area, which has the feeling as a closely knit series of hills and valleys. Figure 2.3 Hillshade Map of the NTC gives a sense of the texture of the topography. Elevation in the Northern Tier Coalition area ranges from approximately 650 feet to nearly 2000 feet in elevation (Figure 2.4). Figure 2.5 is a map of the aspect in the Northern Tier Coalition landscape. Aspect and Elevation are especially important in determining the length of growing season. Under 1000 feet (yellow green in Figure 2.4) is the ideal elevation, between 1000 and 1500 feet (middle green) is workable depending upon aspect and slope, and above 1500 feet (dark green) it is difficult to grow most crops because of the limited number of growing days. This cut off point is will fluctuate depending on exposure: northerly exposures (dark green in Figure 2.4) tend to be colder and southerly exposures (yellow green) warmer, increasing the growing season. Figure 2.6 is a map of slopes in the Northern Tier geography segmented into 0- 2% (blue green), 2-12% (yellow green), 12-18% (middle green) and above 18% (dark green). Slope is a limiting factor for both agriculture and development. Here are some suggested guidelines: industrial sites and parking lots should be on sites no steeper than 4%, septic systems require special designs above 10% and should not be used above 15%, driveways should not be built at a steeper pitch than 15%, cropland is limited to 18% by concerns about tractor safety and erosion. Because of these concerns, local governments may choose to limit development on steep slopes.

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