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Ithan Creek
Ithan Creek (also known as Ithan Run) is a tributary of Darby Creek in Delaware County, Pennsylvania, in the United States. It is approximately long and flows through Radnor Township and Haverford Township. The creek's watershed has an area of and is highly developed. It has three named tributaries: Browns Run, Kirks Run, and Meadowbrook Run. Ithan Creek is within the Piedmont Uplands physiographic province. The creek was historically the site of several mills and has been subjected to numerous floods over the years. In 1902, a sewage company began dumping raw sewage into the creek, but this practice was stopped in 1905. The creek is in approved trout waters. It is the site of Ithan Valley Park, a small park with hiking and fishing opportunities and the Radnor Valley Country Club. Course Ithan Creek rises in a small valley just south of U.S. Route 30 in the community of Wayne, Pennsylvania. It flows west for several tenths of a mile before receiving its first tributary, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delaware River
The Delaware River is a major river in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. From the meeting of its branches in Hancock (village), New York, Hancock, New York, the river flows for along the borders of New York (state), New York, Pennsylvania, New Jersey, and Delaware, before emptying into Delaware Bay. It is the longest free-flowing river in the Eastern United States. The river has been recognized by the National Wildlife Federation as one of the country's Great Waters. The river's drainage basin, watershed drains an area of and provides drinking water for 17 million people. The river has two branches that rise in the Catskill Mountains of New York: the West Branch Delaware River, West Branch at Mount Jefferson (New York), Mount Jefferson in Jefferson, New York, Jefferson, Schoharie County, New York, Schoharie County, and the East Branch Delaware River, East Branch at Grand Gorge, New York, Grand Gorge, Delaware County, New York, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Darby Road
State Route 2005 is a major 9.3 mile (15 km) long road, running in a southeast–northwest direction in Delaware County, Pennsylvania. The western terminus is at Pennsylvania Route 320 in Haverford Township, Pennsylvania. Its eastern terminus is at a Cobbs Creek bridge in Darby, Pennsylvania. Past this bridge is State Route 3023, which continues into Philadelphia. SR 2005 is known as Darby Road in Haverford Township, Lansdowne Avenue from U.S. Route 1 to Darby, and Main Street in Darby. Route description Darby Road SR 2005 begins at an intersection between two forks of Darby Road and Sproul Road (Pennsylvania Route 320) in Haverford Township, Pennsylvania. Immediately after its western terminus, the two forks join and proceed almost due east into woodland with some residential development. The area is generally referred to as Bryn Mawr, Pennsylvania due to sharing a common ZIP code (19010) with the community; however, Bryn Mawr's census-designated place (CDP) is located whol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granodiorite
Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from granite to diorite, including granodiorite. Composition According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% and 90% of the feldspar is plagioclase. A greater amount of plagioclase would designate the rock as tonalite. Granodiorite is felsic to intermediate in composition. It is the intrusive igneous equivalent of the extrusive igneous dacite. It contains a large amount of sodium (Na) and calcium (Ca) rich plagioclase, potassium feldspar, quartz, and minor amounts of muscovite mica as the lighter colored mineral components. Biotite and amphiboles often in the form of hornblende are more abundant in granodiorite than in granite, giving it a more distinct two-toned or overall darker appearan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabbro
Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt. Much of the Earth's oceanic crust is made of gabbro, formed at mid-ocean ridges. Gabbro is also found as plutons associated with continental volcanism. Due to its variant nature, the term ''gabbro'' may be applied loosely to a wide range of intrusive rocks, many of which are merely "gabbroic". By rough analogy, gabbro is to basalt as granite is to rhyolite. Etymology The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his descri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Society Of Pennsylvania
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences, including hydrology, and so is treated as one major aspect of integrated Earth system science and planetary science. Geology describes the structure of the Earth on and beneath its surface, and the processes that have shaped that structure. It also provides tools to determine the relative and absolute ages of rocks found in a given location, and also to describe the histories of those rocks. By combining these tools, geologists are able to chronicle the geological history of the Earth as a whole, and also to demonstrate the age of the Earth. Geology provides the primary evidence for plate tectonics, the evolutionary history of life, and the Earth's past climates. Geologists broadly study the properties and processes of Earth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mica Schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as micas, talc, chlorite, or graphite. These are often interleaved with more granular minerals, such as feldspar or quartz. Schist typically forms during regional metamorphism accompanying the process of mountain building (orogeny) and usually reflects a medium grade of metamorphism. Schist can form from many different kinds of rocks, including sedimentary rocks such as mudstones and igneous rocks such as tuffs. Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a ''mica schist''). Where the type of the original rock (the protolith) is discernible, the schist is usually given a name reflecting its protolith, such as ''schistose met ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serpentinite
Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''serpentine rock'', particularly in older geological texts and in wider cultural settings.California Government Code § 425.2; ''see'' Formation and mineralogy Serpentinite is formed by near to complete serpentinization of mafic to ultramafic rocks. Serpentinite can be formed wherever ultramafic rock is infiltrated by water poor in carbon dioxide. This occurs at mid-ocean ridges and in the forearc mantle of subduction zones. The final mineral composition of serpentinite is usually dominated by lizardite, chrysotile, and magnetite. Brucite and antigorite are less commonly present. Lizardite, chrysotile, and antigorite all have approximately the formula or , but differ in minor components and in form. Accessory minerals, present in smal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Paleozoic
{{Disambiguation ...
Lower may refer to: * Lower (surname) * Lower Township, New Jersey *Lower Receiver (firearms) * Lower Wick Gloucestershire, England See also *Nizhny Nizhny (russian: Ни́жний; masculine), Nizhnyaya (; feminine), or Nizhneye (russian: Ни́жнее; neuter), literally meaning "lower", is the name of several Russian localities. It may refer to: * Nizhny Novgorod, a Russian city colloquial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Appalachian Mountains
The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion. The Appalachian chain is a barrier to east–west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west. Definitions vary on the precise boundaries of the Appalachians. The United States Geological Survey (USGS) defines the ''Appalachian Highlands'' physiographic division as consisting of 13 provinces: the Atlantic Coast Uplands, Eastern Newfoundland Atlantic, Maritime Acadian Highlands, Maritime Plain, Notre Dame and Mégantic Mountains, Western Newfoundland Mountains, Piedmont, Blue Ridge, Valley and Ridge, St. Lawrence Valley, Appalac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Source
The headwaters of a river or stream is the farthest place in that river or stream from its estuary or downstream confluence with another river, as measured along the course of the river. It is also known as a river's source. Definition The United States Geological Survey (USGS) states that a river's "length may be considered to be the distance from the mouth to the most distant headwater source (irrespective of stream name), or from the mouth to the headwaters of the stream commonly known as the source stream". As an example of the second definition above, the USGS at times considers the Missouri River as a tributary of the Mississippi River. But it also follows the first definition above (along with virtually all other geographic authorities and publications) in using the combined Missouri—lower Mississippi length figure in lists of lengths of rivers around the world. Most rivers have numerous tributaries and change names often; it is customary to regard the longest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geographic Names Information System
The Geographic Names Information System (GNIS) is a database of name and locative information about more than two million physical and cultural features throughout the United States and its territories, Antarctica, and the associated states of the Marshall Islands, Federated States of Micronesia, and Palau. It is a type of gazetteer. It was developed by the United States Geological Survey (USGS) in cooperation with the United States Board on Geographic Names (BGN) to promote the standardization of feature names. Data were collected in two phases. Although a third phase was considered, which would have handled name changes where local usages differed from maps, it was never begun. The database is part of a system that includes topographic map names and bibliographic references. The names of books and historic maps that confirm the feature or place name are cited. Variant names, alternatives to official federal names for a feature, are also recorded. Each feature receives a per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
