Dauphin County Comprehensive Plan: Basic Studies & Trends CHAPTER 3 NATURAL RESOURCES percent, respectively. The mean annual sunshine To assist in providing orderly, intelligent, Average Annual Temperature 50° F per year for the County is about 2,500 hours. and efficient growth for Dauphin County, it is Mean Freeze-free Period 175 days Summer Mean Temperature 76° F Although the climate will not have a major essential that features of the natural environment Winter Mean Temperature 32° F effect on land uses, it should be considered in the be delineated, and that this information be layout of buildings for purposes of energy integrated with all other planning tools and Winds are important hydrologic factors consumption. Tree lines and high ground should be procedures. because of their evaporative effects and their on the northwest side of buildings to take association with major storm systems. The advantage of the microclimates of a tract of land. To that end, this chapter provides a prevailing wind directions in the area are from the By breaking the velocity of the northwest winds, compilation of available environmental data as an northwest in winter and from the west in spring. energy conservation can be realized by reducing the aid to planning in the County. The average wind speed is 10 mph, with an temperature slightly. To take advantage of the sun extreme wind speed of 68 mph from the west- for passive or active solar systems, buildings should CLIMATE northwest reported in the Lower Susquehanna area have south facing walls. during severe storm activity in March of 1955. Weather elements or activities of the GEOLOGY atmosphere, such as precipitation, temperature, Hurricanes, or tropical disturbances, as they Map 3-1 graphically illustrates the geology wind direction and speed, relative humidity, and move northward, follow a northeasterly path in the of Dauphin County. sunshine are measurable quantities that affect middle latitudes and produce heavy rainfalls and Dauphin County. strong surface winds in the County. Frequently Dauphin County is located in two affecting water supplies and causing floods, these physiographic provinces – the Ridge and Valley Precipitation data includes: tropical storms are observed during the hurricane Province and the Piedmont. The Ridge and Valley season, June through November. Average Annual Precipitation 46” province is categorized with large ridges and a 2.6” (Feb) to valley that extended from New York to Alabama. The evaporation process is controlled by Normal Monthly Precipitation 4.3” (Aug) The Piedmont Province is characterized by flat areas Snowfall (light-moderate) 30” average temperature, wind, sunshine, and humidity. The located in Lower Dauphin County, specifically in the Mean Annual Days with Snow rate of evaporation during the warmer months has municipalities of Conewago and Lower Paxton. Cover 1” + 50 days an important impact on water storage in reservoirs and on irrigation. The mean May to October The Ridge and Valley Province is composed Air temperatures are important to the evaporation accounts for about 72 percent of the of mostly sandstones and shales. This province management of water resources and water quality. total annual evaporation. constitutes most of Dauphin County. The Piedmont Province is located in Southern Dauphin County and Relative humidity and sunshine also affect is composed of silty mudstone and diabase. Sub the evaporation process. The mean monthly physiographic regions also exist to further break relative humidity for typical seasonal months of down the geology of the region. Dauphin County is January, April, July, and October are about 68 located in six sub physiographic sections. The Natural Resources 3-1 Dauphin County Comprehensive Plan: Basic Studies & Trends sections located in Dauphin County include The Mesozic Era: the expense of a mine. The continued Gettysburg-Newark Lowland, Great Valley, Blue sedimentation and the continued filling of the Mountain, Anthracite Upland, and Susquehanna Triassic Period, 245 million years ago Appalachian basin affected Dauphin County. Jurassic Period, 208 million years ago Lowland. The beginning of the Permian Period started Geology can affect the factors involved with In the Late Cambrian and Early Ordovician with two continents colliding into each other and on-lot sewage disposal, drainage, and construction time period volcanic activity took place. During the causing faulting and folding to occur in the area of costs. The rock types found in Dauphin County Late Ordovician two continents collided into each the Appalachian basin. Folding during the Permian generally do not present specific inherent other causing high mountains, now known as the Period caused the Ridges that are characteristics of limitations. However, in some cases, on-site Appalachian Mountains. On the other side of these the Ridge and Valley Province to occur. Weathering evaluation of geologic factors may be necessary to mountains a long basin was formed, called the and faulting made the Valleys of the same province. determine the feasibility and impacts of a proposed Appalachian basin and filled with ocean water. project. The engineering aspects of the bedrock Limestone’s formed in the basin during the Late The Jurassic and Triassic Periods started geology are also important. These characteristics Ordovician; Limestone is composed of dead sea with volcanic activity once again. During the early give an indication of such things as ease of organisms with high amounts of calcium. Due to Jurassic period heated magma intruded into rocks, excavation, slope stability, and foundation stability. the high concentration of calcium limestone due to weathering this cooled magma can be seen Generally, the rock formations in the County weathers fairly quickly and easily causing problems in the form of diabase. provide strength and support for heavy structures with sinkholes. such as dams, highways, bridges, and large The oldest rocks in the county formed during the buildings. Those few areas that are underlain by In the Silurian period the high Appalachian Cambrian time period. Their formation began at the limestone and dolomites can create problems for Mountains that were formed during the Ordovician end of the Cambrian period and is the same type of certain structures. Cavernous areas and areas period started to weather. Volcanic rocks as with all limestone and dolomite that was created in the known to be susceptible to sinkholes should be rocks weather or breakdown over time, this Ordovician time period. A small amount of the investigated thoroughly before construction of any produces sediment and silt, that accumulated in the Buffalo Springs formation is located in the county structures. Most of these problems would be site Appalachian basin. Some of the sandstone seen in and can be seen in Derry Township. specific and require an on-site evaluation to Dauphin County formed during this time and is very determine the appropriateness of a project. resistant to weathering. Ordovician Period. The majority of these rocks are limestone. The following is a more detailed The geologic era and the period the rocks in description of the existing Ordovician aged rocks in the County. During the Devonian period two continents • Hamburg Sequence: The three types of rocks in this sequence are the Dauphin County were formed influence the type of collided into each other forming the Acadian most common Ordovician rocks in Dauphin County. They are gray, rock and the engineering qualities of these rocks. greenish, or maroon shale’s, dark gray sandstones, and light gray mountains that are north of Pennsylvania. Sediment crystalline and shaly limestones. These rocks produce small fragments The geology of Dauphin County was formed in when weathered, water is available for wells in this area, but would be from these mountains was carried into the easily transferred from place to place so preventing pollution would be several stages occurring in geologic time. Appalachian basin. Over time and through key. The Paleozoic Era: The following are types of the Hamburg Sequence and locations. compaction it formed shales. o Limestone of Hamburg Sequence located in the Townships of Susquehanna, Lower Paxton, East Hanover, West Hanover and Cambrian Period, 570 million years ago South Hanover. o Graywake of Hamburg Sequence located in the Townships of Ordovician Period 505 million years ago The Mississippian and Pennsylvanian periods East Hanover, West Hanover, Susquehanna, Lower Paxton, the Silurian Period, 438 million years ago had some impact on Dauphin County. Much of the Boroughs of Pennbrook, Paxtang, and the City of Harrisburg Devonian Period, 408 million years ago o Hamburg Seq. – (small strips) Located in the Townships of coal in Pennsylvania formed during the South Hanover, West Hanover, East Hanover, Lower Paxton, Mississippian Period, 360 million years ago Susquehanna, Derry, Swatara, Lower Swatara, the Boroughs Pennsylvanian Period, 320 million years ago Mississippian and Pennsylvanian periods. Dauphin of Steelton, Hummelstown, Pennbrook, Paxtang, and the City County does not have enough coal in one area for of Harrisburg. Natural Resources 3-2 Dauphin County Comprehensive Plan: Basic Studies & Trends • Rockdale Run Formation: This formation consists of mostly limestone and coarse grained conglomerate sandstones with thin interbeds of dark some dolomite. Sinkholes may occur in this area, investigations should be gray shaly claystone. Moderately weathered, they provide