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Hammer Creek Formation
The Hammer Creek Formation is a mapped bedrock unit consisting primarily of conglomerate, coarse sandstone, and shale. The Hammer Creek Formation was originally mapped as part of the Gettysburg Formation in Adams County, Pennsylvania in 1929. J. D. Glaeser renamed part of the Gettysburg to the Hammer Creek in 1963, to "avoid extending either the Gettysburg Formation from the west or the Brunswick Formation from the east to include rocks typical of neither unit." A major groundwater resources study of the Hammer Creek Formation and other formations of the Newark Supergroup in Pennsylvania was published by Charles R. Wood in 1980.Wood, C. R., 1980, Groundwater resources of the Gettysburg and Hammer Creek Formations, southeastern Pennsylvania: Pennsylvania Geological Survey, 4th ser., Water Resource Report 49, 87 p.web release. Depositional environment The Hammer Creek Formation and other formations of the Newark Supergroup were deposited in the Newark Basin, just one of many T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hammer Creek
Hammer Creek is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed August 8, 2011 tributary of Cocalico Creek in Lebanon and Lancaster Counties, Pennsylvania in the United States. Hammer Creek is dammed to form Speedwell Forge Lake before joining the Cocalico Creek downstream by the confluence of Middle Creek near the village of Rothsville. Variant names According to the Geographic Names Information System, Hammer Creek has also been known historically as Hammar Creek. Bridges * Brunnerville Road Bridge over Hammer Creek * Erb's Covered Bridge Notable people * Bishop Benjamin Eby (1785–1853) See also *List of rivers of Pennsylvania *John Fass John Stroble Fass (August 25, 1890 - July 19, 1973) was an American graphic designer and a printer of fine press books. Fass designed books for the leading American publishers of limited edition books. Collectors of private press books also remem ... and the Hammer Cree ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extensional Tectonics
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter ''β'', known as the ''beta factor'', where : \beta = \frac \,, ''t''0 is the initial crustal thickness and ''t''1 is the final crustal thickness. It is also the equivalent of the strain parameter ''stretch''. Low beta factor In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted fault blocks. High beta factor In areas of high crustal stretching, individual extensional faults may become rotated to too low a dip to remain active and a new set of faults may be generated. Large displacements may juxtapose syntectonic sediments against metamorphic roc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triassic Geology Of Pennsylvania
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brunswick Formation
The Passaic Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It was previously known as the Brunswick Formation since it was first described in the vicinity of New Brunswick, New Jersey. It is now named for the city of Passaic, New Jersey, which is near where its type section was described by paleontologist Paul E. Olsen. Description The Passaic is defined as a reddish-brown shale, siltstone and mudstone with a few green and brown shale interbeds; red and dark-gray interbedded argillites near the base. In New Jersey, there are conglomerate and sandstone beds within the formation. Depositional environment The Passaic is mostly shallow lakes, playa, and alluvial fan deposits resulting from the rifting of Pangea. The red color is often evidence that the sediments were deposited in arid conditions.Faill, R.T., (2004). The Birdsboro Basin. ''Pennsylvania Geology'' V. 34 n. 4. The Passaic Formation overlies the Lockatong Formation deep lake sediment cycles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schuylkill River
The Schuylkill River ( , ) is a river running northwest to southeast in eastern Pennsylvania. The river was improved by navigations into the Schuylkill Canal, and several of its tributaries drain major parts of Pennsylvania's Coal Region. It flows for U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed April 1, 2011 from Pottsville to Philadelphia, where it joins the Delaware River as one of its largest tributaries. In 1682, William Penn chose the left bank of the confluence upon which he founded the planned city of Philadelphia on lands purchased from the native Delaware nation. It is a designated Pennsylvania Scenic River, and its whole length was once part of the Delaware people's southern territories. The river's watershed of about lies entirely within the state of Pennsylvania, the upper portions in the Ridge-and-valley Appalachian Mountains where the folding of the mountain ridges metamorphically modified bit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lebanon County, Pennsylvania
Lebanon County ( Pennsylvania Dutch: Lebanon Kaundi) is a county in the Commonwealth of Pennsylvania. As of the 2010 census, the population was 133,568. Its county seat is the city of Lebanon. The county was formed from portions of Dauphin and Lancaster counties in 1813, with minor boundary revisions in 1814 and 1821. Lebanon County comprises the Lebanon, Pennsylvania, metropolitan statistical, which is part of the Harrisburg–York–Lebanon combined statistical area. Lebanon is 72 miles northwest of Philadelphia, which is the nearest major city. Geography According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.2%) is water. Most of it is drained by the Swatara Creek into the Susquehanna River while some eastern portions are drained by the Tulpehocken Creek (which originates in the county near Myerstown) eastward into the Schuylkill River. It consists in large part of a valley. Climate The county has a hot-summer humid contine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dauphin County, Pennsylvania
Dauphin County (; Pennsylvania Dutch: Daffin Kaundi) is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 286,401. The county seat and the largest city is Harrisburg, Pennsylvania's state capital and ninth largest city. The county was created ("erected") on March 4, 1785, from part of Lancaster County and was named after Louis Joseph, Dauphin of France, the first son of King Louis XVI. Dauphin County is included in the Harrisburg–Carlisle Metropolitan Statistical Area. Located within the county is Three Mile Island Nuclear Generating Station, site of the 1979 nuclear core meltdown. The nuclear power plant closed in 2019. Geography According to the U.S. Census Bureau, the county has a total area of , of which is land and (5.9%) is water. The county is bound to its western border by the Susquehanna River (with the exception of a small peninsula next to Duncannon). The area code is 717 with an overlay of 223. Adjacent counties * N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unconformity
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the sedimentary geologic record. The significance of angular unconformity (see below) was shown by James Hutton, who found examples of Hutton's Unconformity at Jedburgh in 1787 and at Siccar Point in 1788. The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region or were subsequently eroded before the next deposition. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continent
A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven regions are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. "Most people recognize seven continents—Asia, Africa, North America, South America, Antarctica, Europe, and Australia, from largest to smallest—although sometimes Asia and Europe are considered a single continent, Eurasia." Variations with fewer continents may merge some of these, for example America, Eurasia, or Afro-Eurasia are sometimes treated as single continents, which can bring the total number as low as four. Zealandia, a largely submerged mass of continental crust, has also been described as a continent. Oceanic islands are frequently grouped with a nearby continent to divide all the world's land into geographical regions. Under t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic and beginning of the Jurassic. In contrast to the present Earth and its distribution of continental mass, Pangaea was centred on the equator and surrounded by the superocean Panthalassa and the Paleo-Tethys Ocean, Paleo-Tethys and subsequent Tethys Ocean, Tethys Oceans. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists. Origin of the concept The name "Pangaea" is derived from Ancient Greek ''pan'' (, "all, entire, whole") and ''Gaia (mythology), Gaia'' or Gaea (, "Mother goddess, Mother Earth, land"). The concept that the continents once formed a contiguous land mass was hypothesised, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rift
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to the poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newark Supergroup
The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary rocks which outcrop intermittently along the United States East Coast. They were deposited in a series of Triassic basins approximately 190 million years ago as North America separated from Africa. The exposures extend from Nova Scotia to North Carolina. Related basins are also found underwater in the Bay of Fundy. The group is named for the city of Newark, New Jersey. Characteristics The Newark Supergroup consists largely of poorly sorted nonmarine sediments; typical rocks are breccia, conglomerate, arkose sandstone, siltstone, and shale. Most of the strata are red beds that feature ripple marks, mud cracks, and even rain drop prints; dinosaur footprints are common, though actual body fossils are very rare. Some of the strata are detailed to the level of varves, with indications of Milankovitch cycles. In preserved lake sediments, ''Semionotus'' fossils are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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