DOCSLIB.ORG

The Story of the Wissahickon Rocks Tienne Moriniere-Myers Introduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Story of the Wissahickon Rocks Tienne Moriniere-Myers Introduction Myers, 1 SCIENCE CONTENT: The Story of the Wissahickon Rocks Tienne Moriniere-Myers Introduction: The purpose of this project is to design resources, for use in a middle school science class, presenting Wissahickon Schist as a way of understanding metamorphism, while gaining an appreciation for geological features in the local region. The first section of the project is to provide information about the amazing rocks that are located in Philadelphia and to understand the recipe that caused them to become became part of our geologic landscape. The second section of this project will provide strategies to teach students about the rock cycle and metamorphism. It will tackle student misconceptions and focus on enduring understandings. When you examine a rock you can learn a great deal about its origins and geological history. Earth formed about 4.5 billion years ago. Unfortunately, there are no rocks remaining on Earth from this part of Earth’s early geological history, but the rocks that do exist on Earth give us clues to interpret what happened in the past. The rocks found in the Wissahickon Valley tell us the amazing geologic story of Philadelphia. Background: Geological Time Since the beginning of the 1700’s, scientists have agreed that some rocks are older than others. A time chart, the geologic time scale, was developed to categorize rocks according to their ages based on methods of relative dating. Since 1949 geologists have been able to date rocks by radioactive elements. The breakdown or decay of atomic nuclei is known as radioactive decay. As radioactive parent atoms decay to their stable daughter atoms (i.e., uranium decaying to lead), there is one more atom of the daughter than was initially present, and one less atom of the parent. The time required for one-half of the original number of parent atoms to decay is the half-life, which is related to the decay constant (Lutgens and Tarbuck, 2006). Knowing the half life, one can determine the absolute age of a rock based on the ratio of the parent to daughter isotopes in the rock. 1 Myers, 2 With these dates, geologists have been able to assign absolute ages on the geological time scale. The following chart shows the divisions of geologic time and their corresponding ages. Figure 1 The Geological Time Scale divides Earth’s geologic history into distinct intervals of time. http://3dparks.wr.usgs.gov/bigbend/images/timescale.jpg&imgrefurl Plate Tectonics An observant meteorologist, Alfred Wegner, noticed how neatly the eastern American coast fits against the western coast of Africa and Europe. His hypothesis, called continental drift, was published in 1915. He postulated that a supercontinent called Pangaea existed and broke apart leading to Earth’s current configuration of continents. 2 Myers, 3 His ideas and concepts were based on some very convincing observations. Wegner noticed, and confirmed his findings with the paleontological literature, that identical fossil organisms were found in both the South American and African continents, including organisms that had no ability to swim across such a mass of water (Erickson, 2001). The classic example of this is the Mesosauris He also noticed the close fit between the coastlines of Africa and South America. However, his jigsaw fit of the continents was very crude, and he did not provide a convincing mechanism for how and why the continents moved (Tarbuck and Lutgens, 2006). After World War II, studies of the seafloor led to the discovery of a global oceanic ridge system winding through all of the major oceans in a manner similar to the seams of a baseball (Lutgens and Tarbuck, 2006). The observation of this topographical feature and its connection to alternating bands—each band magnetized with a polarity opposite the surrounding bands—of seafloor led to the understanding of seafloor spreading (the process by which new oceanic crust is formed at mid-ocean ridges through volcanic activity and then slowly moved away from the ridge). Seafloor spreading helps to explain how the continents drift in the paradigm of plate tectonics (Erickson, 2001) Plate tectonics is the ultimate framework into which observations of North American geologic history fit. The paradigm of Plate Tectonics states that Earth’s crust is composed of a rigid layer known as the lithosphere, which is broken into pieces called plates (Erickson, 2001). There are seven major lithosphere plates: North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic. These plates rest on a region in the mantle known as the asthenosphere. The asthenosphere is composed of rocks that are near their melting temperature. The result is a very weak zone that allows the lithosphere to detach from the layers below. The weak rock within the upper asthenosphere allows the Earth’s rigid outer shell to move. The theory is also based on the fact that mid-ocean ridges and trenches border these plates, and the crust is moving under the power of convection in the mantle below. The theory explains how we can look at rocks today and conclude their past and predict their future (Lutgens and Tarbuck, 2006). 3 Myers, 4 The Plate Tectonic History of the Wissahickon Valley: The Paleozoic Orogenies of the Central East Coast of North America. Three important Paleozoic orogenies that helped to shape the region we now call Eastern North America occurred between 500 and 250 million years ago. During this time, rocks show evidence of continental plates combining to form the supercontinent Pangaea. After these events, a divergent plate boundary developed and opened the ocean we today call the Atlantic. Precambrian rocks show that continental rifting and collisions of this kind have been occurring for over two billion years and likely Earth’s entire 4.5 billion year history (Roberts, 2006). The Rocks of the Wissahickon Through Geological Eras Since the Precambrian, margins of what was to become the east coast of North America have been very active geologically. Geologists hypothesize that during the Precambrian Eon the region we now refer to as the Wissahickon Valley was in its nascent stage, forming as shale and sandstone deposits on the floor of the Iapetus Ocean. At some stage in the late Ordovian era, materials from the Ocean floor were thrusted onto the eastern coast of the proto-North American plate. This was called the Taconic orogeny, and this event caused the development of mountains in Pennsylvania. At the end of the Devonian Period another collision took place. A crash of the eastern North American coastline and Europe caused the Acadian orogeny, another large mountain building event. Once these mountains were formed, deposits of black and gray shale must have covered the eastern part of Pennsylvania as once again it was inundated with water. Ultimately, the Acadian mountains eroded causing more sediment to be created. There was no more marine water in this area after this time period. The Permian Period saw another major collision of North America. This collision is known as the Appalachian orogeny. This was the collision of North America and Africa. The supercontinent of Pangaea was formed (Roberts, 2006). During each of these collisions larger and larger mountains were formed and the shale and sandstone deposits originally deposited during Precambrian time in the ancient 4 Myers, 5 Iapetus Ocean were further buried and metamorphosed. A very large mountain range, similar in scale to the Himalyas today must have existed along the East Coast of North America, with the schist and quartzite (products of metamorphosing the shale and sandstone) buried deep within. These mountains were eventually eroded over the last 200 million years, since Pangaea has split apart, and the sediments eroded from this mountain range now lie in the Atlantic Ocean. A vast amount of material eroded in these 200 million years. The time and the amount of material eroded seems massive beyond our imagination, but this is just a small percentage of geological time; 200 million years is less than 5% of Earth’s history! With the mountains now eroded, the Piedmont Province of Pennsylvania where the Wissahickon Valley is located is now exposed at the surface, and with it the beauty of its sparkling schist, sturdy quartzite and myriad pegmatite intrusions (West, 1998). The Rocks of the Wissahickon Valley: The Rock cycle Rocks are classified in three main categories: Igneous, Sedimentary and Metamorphic. They are classified according to how they are formed. Igneous rocks or “fire rocks” form when magma or molten rock cools and solidifies. This process is called crystallization. This may happen above the Earth’s surface after the eruption of a volcano or beneath the Earth’s crust. Igneous rocks are found at the surface and endure weathering. Then, they slowly disintegrate. The particles that are created are affected by gravity and slowly move downhill. These sediments can be transported by water, glaciers, or wind. Eventually these particles, called sediments, are deposited. Most sediments end up in the ocean. Other sites of deposition are desert basins, river flood plains, sand dunes and swamps. These sediments convert into rock through the process of lithification. This takes place when sediments are compacted by the weight of overlaying layers or cemented as percolating ground water fills the pours with mineral matter. The result is sedimentary rock. Sometimes the resulting sedimentary rock becomes buried deep inside the Earth. This rock can be part of a mountain building or intruded by a mass of magma. It will then be confronted by great pressure, intense heat, chemically active fluids, or a combination of all three. The sedimentary rocks will 5 Myers, 6 react to this new environment and turn into metamorphic rock. Rocks are constantly undergoing changes, which take a great deal of time.
Load more

Recommended publications
  • The Chemistry of Rocks in the Wissahickon Valley
    The Chemistry of Rocks in the Wissahickon Valley Cristobal Carambo Philadelphia High School for Girls Problem Statement Rationale Proposed Unit of Study Objectives Background Standards Used in the Unit Lesson Plans Appendix Bibliography Problem Statement The majority of my students are sophomores who have had little to no science during their middle school years. This lack of a comprehensive science program in their formative years explains much of their difficulty connecting science to their daily life. This is most evident when I introduce the periodic table of elements and attempt to explain how elements combine to form the many compounds that are necessary in our lives. Although I use many common household chemicals to illustrate the importance of elements and compounds, students still fail to fully appreciate the role that chemistry plays in our understanding of the physical world. I have often attempted to use the chemistry of the rock cycle to connect our class to the real world but many students are unaware of the rock cycle, or have had a cursory general survey of rocks. Understanding the role that elements play in the formation of minerals and how those minerals combine to form the many rock types and materials in our world would create a vibrant connection between the static elements on the periodic table and the world in which we live. In our conversations of the world around us, I have noticed that many of my students have had little or no experiences in natural settings where they could explore and make connections between the concepts learned in the classroom and their environment.
    [Show full text]
  • State of the Schuylkill River Watershed
    A Report on the S TATE OF THE SCHUYLKILL RIVER W ATERSHED 2002 Prepared by The Conservation Fund for the Schuylkill River Watershed Initiative T ABLE OF CONTENTS L IST OF FIGURES Forward ............................................................. 1 4. Public Awareness and Education 1 ...... Regional Location 2 ...... Physiographic Regions Introduction ....................................................... 2 Overview ........................................................... 27 3 ...... Percentage of Stream Miles by Stream 4 ...... Dams in the Schuylkill Watershed Enhancing Public Awareness ............................... 28 5 ...... Land Cover 1. The Watershed Today Educating the Next Generation .......................... 29 6 ...... 1990-2000 Population Change, by Municipality 7 ...... Land Development Trends, Montgomery County Overview ........................................................... 3 Environmental Education Centers ...................... 30 8 ...... 1970-95 Trends in Population and Land Consumption, Environmental Setting ........................................ 4 Special Recognition of the Schuylkill ................. 31 Montgomery County 9 ...... Water Supply Intakes Historical Influences ........................................... 5 10 .... Seasonal Relationships Between Water Withdrawals and River Flow 11 .... Water Withdrawals in the Schuylkill Watershed Land Use and Population Change....................... 6 5. Looking Out for the Watershed - Who is Involved 12 .... Monitoring Locations and Tributaries Surveyed
    [Show full text]
  • Wissahickon Creek Conservation Landscape
    CHAPTER 10 Wissahickon Creek Conservation Landscape The Green Ribbon Preserve, and its included trail system, established by the Wissahickon Valley Watershed Association is the central feature of the Wissahickon Creek Conservation Landscape. The fl oodplain forests along the Wissahickon Creek and Fort Washington State Park are particu- larly important habitat for birds because of the highly developed nature of the surrounding area. Description Location The Wissahickon Creek Conservation Landscape comprises 6,517 acres extending along the Wissahickon Creek from just south of Lansdale to the Montgomery County border with Phila- delphia. It includes portions of Springfi eld, Whitemarsh, Upper Dublin, Whitpain, Lower Gwynedd, and Upper Gwynedd Townships (Figure 10.1). The landscape is anchored by the Green Ribbon Preserve, a project of the Wissahickon Valley Watershed Association. It also includes Fort Washington State Park. It is not contiguous with any of the other conservation landscapes described in this report. Hydrology The landscape lies completely within the Wissahickon Creek watershed. It includes portions of several tributaries including Sandy Run, Prophecy Creek, and Haines Run. The Wissahickon and its tributaries are classifi ed as TSF (trout stocked fi shery) by the Pennsylvania Department of Environmental Protection. The hydrology of the Wissahickon Creek has been severely affected by impervious surface coverage throughout the basin. Ground water recharge is reduced due to the channeling of storm water directly into the streams. Less ground water means less base fl ow. During the summer many of the smaller tributaries go dry and approximately 80 percent of the fl ow in the Wissahickon basin is effl uent from the 12 sewage treatment plants located between the headwaters and the Montgomery Coun- Wissahickon Creek above Swedesford Road ty line.
    [Show full text]
  • Wissahickon Watershed Stream Monitoring and Assessment Program
    Wissahickon Watershed Stream Monitoring and Assessment Program A summary of data collected by the Wissahickon Valley Watershed Association from 2004-2016 May 2017 This page was intentionally left blank. LIST OF FIGURES Figure 2- 1. Impacts of the urban stream syndrome 12 Figure 2- 2. A map of wastewater treatment plants in the Wissahickon Watershed 14 Figure 3- 1. A map of sampling locations from 2004 to 2016 18 Figure 4- 1. The median macroinvertebrate index of biotic intgrity of all sites from 2011 to 2015 23 Figure 4- 2. Macroinvertebrate functional feeding groups 2011 to 2013 25 Figure 4- 3. The Wissahickon Watershed and macroinvertebrate survey sites from 2011- 2015 27 Figure 5- 1. Median habitat assessments site scores for all sites from 2011 to 2016 30 Figure 5- 2. Annual site habitat scores for all sites 31 Figure 5- 3. A map of the Wissahickon Watershed and habitat assessment sites from 2011- 2016 36 Figure 6- 1. Average seasonal specific conductivity from 2015 to 2016 41 Figure 6- 2. Median orthophosphate concentrations from 2004 to 2010 44 Figure 6- 3. Median orthophosphate concentration from 2011 to 2016 45 Figure 6- 4. Seasonal average orthophosphate concentrations from 2014 to 2016 46 Figure 6- 5. Annual average orthophosphate concentrations at all sites from 2008 to 2016 47 Figure 6- 6. Median total phosphorus concentrations from 2004 to 2010 48 Figure 6- 7. Median total phosphorus concentrations from 2011 to 2016 49 Figure 6- 8. Seasonal average total phosphorus concentrations from 2014 to 2016 50 Figure 6- 9. Annual average total phosphorus concentrations at all sites from 2008 to 2016 51 Figure 6- 10.
    [Show full text]
  • WISSAHICKON CREEK TOTAL MAXIMUM DAILY LOAD (TMDL) STRATEGY Cheltenham Township, Montgomery County, Pennsylvania March 2016
    CHELTENHAM TOWNSHIP - WISSAHICKON CREEK TOTAL MAXIMUM DAILY LOAD (TMDL) STRATEGY Cheltenham Township, Montgomery County, Pennsylvania March 2016 Prepared by: An Employee Owned Company Table of Contents Introduction Wissahickon Watershed Information Waste Load Allocation (WLA) WLA Reduction / Parsing Reduction in Pollutant Loadings Pollutant Loading Reduction Implementation Public Participation References Appendix I – Figures Appendix II – Tables Appendix III - BMP Listing and Sediment Removal Rates Appendix IV – Public Participation & Involvement S:\2013\1382005\TMDL Plan\Cheltenham Township TMDL Plan.docx Introduction Section 303(d) of the Clean Water Act and the U.S. Environmental Protection Agency's (EPA's) Water Quality Planning and Management Regulations (40 CFR Part 130) require states to develop Total Maximum Daily Loads (TMDLs) for waterbodies that are not meeting their designated uses even though pollutant sources have implemented technology-based controls. A TMDL establishes the allowable load of a pollutant or other quantifiable parameter based on the relationship between pollutant sources and in-stream water quality. A TMDL provides the scientific basis for a state to establish water quality- based controls to reduce pollution from both point and nonpoint sources and restore and maintain the quality of the state's water resources (USEPA, 1991). 1 The EPA established a Total Maximum Daily Load (TMDL) for the Wissahickon Creek watershed in 2003 to address those segments impaired as a result of excess siltation. The TMDL identified overland flow from urban stormwater runoff and streambank erosion as primary contributors. Cheltenham Township as a regulated MS4 is required to implement a TMDL plan through the National Pollutant Discharge Elimination System (NPDES) program.
    [Show full text]
  • Residential Land Use Change in the Wissahickon Creek Watershed: Profitability and Sustainability?
    sustainability Article Residential Land Use Change in the Wissahickon Creek Watershed: Profitability and Sustainability? John Sorrentino 1,* , Mahbubur Meenar 2 and Donald Wargo 1 1 Department of Economics, College of Liberal Arts, Temple University, Philadelphia, PA 19122, USA; [email protected] 2 Department of Geography, Planning, and Sustainability, School of Earth and Environment, Rowan University, Glassboro, NJ 08028, USA; [email protected] * Correspondence: [email protected] Received: 19 September 2019; Accepted: 22 October 2019; Published: 25 October 2019 Abstract: The Wissahickon Creek Watershed is one of five major watersheds in the Philadelphia metro region. The main objective of the work in this paper was to determine and compare the energy and environmental impacts of placing housing in the Watershed according to profitability and environmental sustainability criteria, respectively, in the context of increasing urbanization. Future population and employment for the Watershed have been projected by the Delaware Valley Regional Planning Commission. Housing requirements for the projected populations in each municipality were computed, and their location was influenced by the local zoning ordinances. Suitability analysis using ArcGIS 10.6 generated areas for development based alternatively on profitability and local sustainability. CommunityViz 5.2 Scenario 360 software was used to place buildings within the appropriately-zoned areas. Using Argonne National Laboratory’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET1 2018) software and water quality monitoring information from the Philadelphia Water Department, impacts were directly estimated. The impacts were related to effects on ecosystem functioning, ecosystem goods and services, and broad value estimated for the latter. The effects were used to indicate what might be appropriate policies to reduce the negative environmental consequences of residential development in the watershed.
    [Show full text]
  • Chestnut Hill College Ninety-Fourth Annual Commencement May 8Th Two Thousand Twenty-One
    CHESTNUT HILL COLLEGE NINETY-FOURTH ANNUAL COMMENCEMENT MAY 8TH TWO THOUSAND TWENTY-ONE HISTORY OF CHESTNUT HILL COLLEGE Located at the northwestern edge of Philadelphia on 75 acres overlooking the Wissahickon Creek, Chestnut Hill College opened in 1924 as a Catholic, four-year, liberal arts college for women. Founded as Mount Saint Joseph College by the Sisters of Saint Joseph, the College was renamed in 1938 as Chestnut Hill College. Since its inception, the College has offered a rigorous liberal arts education that provides students with a broad background in the humanities, social sciences, and natural sciences. The goal of Chestnut Hill College has been to prepare students for life’s challenges by helping them to grow intellectually, spiritually, emotionally, and socially. In keeping with the spirit of the Sisters of Saint Joseph, the curriculum has been modified over time to meet the ever- changing needs of higher education and society. The College originally awarded only the Bachelor of Arts and Bachelor of Science degrees to young women of traditional college age. In 1972, a Continuing Education department extended opportunities for undergraduate study to mature women and men. With the addition of a coeducational graduate program in 1980, the College began to offer master’s degrees and, in 1997, added its first doctoral program. Today, students may earn master’s degrees in six disciplines and a doctorate in clinical psychology. Academic changes also included expansion beyond the physical limits of the campus. As a member of SEPCHE (Southeastern Pennsylvania Consortium for Higher Education), Chestnut Hill pursues a collaborative approach to higher education with seven other local institutions.
    [Show full text]
  • Calcium Zoning in Almandine Garnet, Wissahickon
    Canadian Mineralogist Vol. 15, w. M3-249 (1971) CALCIUMZONING IN ALMANDINEGARNET, WISSAHICKONFORMATION, PHIIADEIPHIA, PENNSYTVANIA MARIA LUISA CRAWFORD Bryn Mawr College,Bryn Mawr, Pa. 19010 USA ABsrRAcr INTRoDUcTIoN Garnets with clearly developed Ca zoning gen- As our knowledge of the details of garnet erally are associated with zoned plagioclase in chemistry in rnetamorphic rocks continues to samples of interlayered pelites and calcareous sand- grow it is apparent that the calcium content of stones in the Wissahickon Formation northwest of almandine garnets may be used as a geothermo- Philadelphia, Pa. Systematic Ca zoning is absent in meter or a geobarometerin certain metamorphic metamorphio assemblages with hieh variance, al- (Ghent et al. 1975). though the garnet may be zoned in other elements. assemblages 1976; Hensen Apparently calcium zoning in metamorphic alman- In addition, the calcium zoning patterns in gar- dine-rich garnets develops (1) during metamorphic nets usually differ, often markedly, from the reactions involving plagioclase-garnet equilibria; (2) zoning trends shown by Fe, Mg and Mn (Craw- as a rsult of reactions between otler minerals in ford 1974; de B6thune et al. 1968; Linthout & low-vaxiance assemblages; and (3) in volumes of Westra 1968). Most of the detailed studies of rock subject to changes in calcium content due to garnet equilibria have focused on the Fe, Mg and diffusion during metamorlfiic recrystallization. Mn zoning and the chemical interactions be- producing Where several of these mechanisms for tween garnet and otler ferromagnesian phases. Ca zoning operate simultaneously, the zoning pro- 'Where described,but little attention files are complex. the zoning is relatively Ca zoning has been parageneses simple, the trends of the calcium zoniDg itr alman- has been paid to the mineral and dine, when considered in conjunction with the zon.
    [Show full text]
  • Section 1: Watershed Location and Setting
    Section 1: Watershed Location and Setting The Wissahickon Creek Watershed is located in southeastern Pennsylvania. It covers 64 square miles and includes a population of approximately 221,000 people (2010 Census). The watershed includes the 1,400 acre Wissahickon Valley Park, part of the Fairmont Park system within the City of Philadelphia; Fort Washington State Park in Montgomery County; 1,200 acres of protected land and 21 miles of trails in Montgomery County protected under stewardship of the Wissahickon Valley Watershed Association; as well as many smaller municipal parks and preserves. The watershed lies within the lower Delaware River Basin and discharges to the Schuylkill River in the City of Philadelphia. Most of the watershed is located in Montgomery County, with approximately 16 percent located in Philadelphia County (Figure 1.A). A total of 16 municipalities lie either all or partially within the watershed. The population of those municipalities is provided in Table 1.A, along with the percentage of the watershed draining each municipality. Table 1.A Population by Municipality 2010 Population by Municipality Municipality % 2010 Population Municipality 2010 Census in Watershed in Watershed Abington Township 55,310 22.94% 12,687 Ambler Borough 6,417 100.00% 6,417 Cheltenham Township 36,793 1.39% 514 Horsham Township 26,147 0.56% 147 Lansdale Borough 16,269 23.65% 3,848 Lower Gwynedd Township 11,405 88.29% 10,069 Montgomery Township 24,790 14.01% 3,473 North Wales Borough 3,229 100.00% 3,229 Philadelphia County 1,526,006 7.34% 112,075 Springfield Township 19,418 94.57% 18,364 Upper Dublin Township 25,569 90.30% 23,090 Upper Gwynedd Township 15,552 61.86% 9,622 Upper Moreland Township 24,015 0.29% 70 Whitemarsh Township 17,349 56.38% 9,782 Whitpain Township 18,875 41.68% 7,868 Worcester Township 9,750 0.64% 63 1-1 The Wissahickon Creek watershed contains approximately 115 miles of defined streams and tributaries.1 Figure 1.B shows the main stem and major tributaries within the watershed.
    [Show full text]
  • HENRY AVENUE BRIDGE HAER No. PA-464 (Wissahickon Memorial Bridge) Pennsylvania Historic Bridges Recording Project Spanning Wissahickon Creek at Henry Ave
    HENRY AVENUE BRIDGE HAER No. PA-464 (Wissahickon Memorial Bridge) Pennsylvania Historic Bridges Recording Project Spanning Wissahickon Creek at Henry Ave. (State Rt. 4001) Philadelphia QAAJL. (j-',^yA &V■■ Philadelphia County Pennsylvania PHOTOGRAPHS WRITTEN HISTORICAL AND DESCRIPTIVE DATA HISTORIC AMERICAN ENGINEERING RECORD National Park Service 1849 C Street, NW Washington, DC 20240 HISTORIC AMERICAN ENGINEERING RECORD HENRY AVENUE BRIDGE (Wissahickon Memorial Bridge) HAERNo.PA-464 Location: Spanning Wissahickon Creek and Lincoln Dr. at Henry Ave. (State Rt. 4001), Philadelphia, Philadelphia County, Pennsylvania. USGS Quadrangle: Germantown, Pennsylvania (7.5-minute series, 1983). UTM Coordinates: 18/483250/4430240 Dates of Construction: 1930-32. Designer: Ralph Modjeski and Clement E. Chase, engineers; George S. Webster, consulting engineer; Paul P. Cret, consulting architect. Contractor: Francis A. Canuso and Son. Present Owner: Pennsylvania Department of Transportation. Present Use: Vehicular bridge. Significance: This single-span, two-ribbed reinforced concrete arch bridge soars high over the Wissahickon Creek in Philadelphia's Fairmount Park. It is a late example of a masonry-clad reinforced concrete arch bridge — a common design for concrete bridges in parks and cities in the early twentieth century. The visually dramatic bridge features a 288'-0" main span with open-spandrel arches, rusticated piers, and unusual architectural details. Plans provided yet-unused space for a transit line running through the bridge. The bridge's design was supervised by prolific engineer Ralph Modjeski, whose firm retained well-known Philadelphia architect Paul Cret as an architectural consultant. The Henry Avenue Bridge was listed in the National Register of Historic Places in 1988. Historian: J. Philip Gruen, August 1997.
    [Show full text]
  • Description of the Coatesville and West Chester Quadrangles
    DESCRIPTION OF THE COATESVILLE AND WEST CHESTER QUADRANGLES By F. Bascom and Greorge W. Stose INTRODUCTION which are grown in greenhouses and shipped chiefly to Phila­ PIEDMONT PROVINCE delphia. West Grove is said to have the largest rose-growing LOCATION AND AREA Geography. The Piedmont province, which owes its name establishments in America. to its location at the foot of the Blue Ridge, merges on the The Coatesville and West Chester quadrangles are 14 miles Good dirt roads, hard-surfaced main highways, trolley lines, northeast with the New England province. On the southwest west of Philadelphia, between parallels 39° 45' and 40° and and excellent railway facilities are cultural features of the dis­ it is terminated in Alabama and Georgia by the Gulf Coastal meridians 75° 30' and 76°. They include one-eighth of a trict. The Lincoln Highway traverses Chester Valley. The Plain, and on the east it is bounded by the Coastal Plain. "square degree" and cover an area of about 458 square miles. four tracks of the main line of the Pennsylvania Railroad fol­ The province has a mean width of 60 miles and a maximum This area embraces portions of Delaware, Chester, and Lancas­ low Chester Valley with a branch line to West Chester and width in its central portion of 120 miles. ter Counties, Pa., and New Castle County, Del., but is chiefly another from Pomeroy through Avondale; the Philadelphia, The boundary between the Piedmont province and the in Chester County. It sustains a population of nearly 130,000, Baltimore & Washington line (Maryland division) passes Coastal Plain is defined in most places by a well-marked of whom about one-half live in the principal towns Wilming- through Wilmington, and another line of the Pennsylvania change in topography and geology.
    [Show full text]
  • State Water Plan Subbasin 03F Lower Schuylkill River Watershed (Wissahickon Creek) Montgomery, Philadelphia, Chester, and Delaware Counties
    Updated 12/2003 Watershed Restoration Action Strategy (WRAS) State Water Plan Subbasin 03F Lower Schuylkill River Watershed (Wissahickon Creek) Montgomery, Philadelphia, Chester, and Delaware Counties Introduction Subbasin 03F consists of the lower Schuylkill River and its tributaries from Valley Forge to the confluence with the Delaware River in southwest Philadelphia. The subbasin encompasses 228 square miles and contains a total of 309 miles flowing in 185 streams. The subbasin is included in HUC Area 2040203, Schuylkill River, a Category I, FY99/2000 Priority watershed. The largest tributary in the basin is the Wissahickon Creek, which drains 64 square miles of lower Montgomery County and northwestern Philadelphia. Wissahickon Creek flows for twenty-three miles through the boroughs of Lansdale, North Wales, and Ambler in Montgomery County then into the city of Philadelphia through the scenic gorge in Wissahickon Park, part of the city owned Fairmount Park system. The Wissahickon Creek ends near the Queen Lane Reservoir drinking water intake on the bank of the Schuylkill River. More than 90% of the riparian zone of the Wissahickon Creek has been preserved in a natural state. The creek and adjoining parks receive extensive recreational use. The Wissahickon Creek also serves as one of the water supplies for Philadelphia. Geology/ Soils The majority of the basin is within the Northern Piedmont Ecoregion, Piedmont Uplands section (64c), comprised of mainly schist of the Wissahickon Formation, with some areas of serpentine and gneiss. This area is hilly with steeply sloped ravines along the major streams. The soils of the uplands have moderate rates of infiltration; slopes range from 15 to 20 percent.
    [Show full text]