A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain amount of rock strata that have a comparable lithology, facies or other similar properties. Formations are not defined by the thickness of their rock strata; the concept of formally defined layers or strata is central to the geologic discipline of stratigraphy. Groups of strata are divided into formations; the definition and recognition of formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata. Formations were at first described as the essential geologic time markers, based on their relative ages and the law of superposition; the divisions of the geological time scale were described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries. The lithology of a rock is a description of its visible physical characteristics. Modern geology prefers to use lithology, that it an examination of the visible features of the component rocks, to identify discrete formations.
Geologic formations are divided into the broad categories of: sedimentary rock layers. Intrusive igneous rocks are not considered to be formations; the contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region. Formations must be able to be delineated at the scale of geologic mapping practiced in the region. Geologic formations are named after the geographic area in which they were first described. Formations cannot be defined by any criteria other than primary lithology, it is useful to define biostratigraphic units on paleontological criteria, chronostratigraphic units on the age of the rocks, chemostratigraphic units on geochemical criteria. The term "formation" is used informally to refer to a specific grouping of rocks, such as those encountered within a certain depth range in an oil well "Formation" is used informally to describe the odd shapes that rocks acquire through erosional or depositional processes; such a formation is abandoned.
Some well-known cave formations include stalagmites. Geochronology – Science of determining the age of rocks and fossils List of rock formations – Links to Wikipedia articles about notable rock outcrops List of Chinese geological formations List of fossil sites – A table of worldwide localities notable for the presence of fossils
In geology, a pluton is a body of intrusive igneous rock, crystallized from magma cooling below the surface of the Earth. While pluton is a general term to describe an intrusive igneous body, there has been some confusion around the world as to what is the definition of a pluton. Pluton has been used to describe any non-tabular intrusive body, batholith has been used to describe systems of plutons. In other literature and pluton have been used interchangeably. In central Europe, smaller bodies are described as larger bodies as plutons. In practice the term pluton most means a non-tabular igneous intrusive body; the most common rock types in plutons are granite, tonalite and quartz diorite. Light colored, coarse-grained plutons of these compositions are referred to as granitoids. Examples of plutons include Denali in Alaska. Intrusive bodies of igneous rock can be classified from one distinctions. If the body is tabular or not; the bodies can be further classified based on their shape and their concordancy with the surrounding country rocks.
A tabular body is magma that has filled in another plane of weakness. A non-tabular body however, can vary in shape much more than tabular bodies and tend to be much larger. A concordant body is one that does not cross a pre-existing fabric in the country rock, a sill is an example of a concordant tabular intrusive body. A discordant body is one that does cross pre-existing fabrics in the country rock, a dike is an example of a discordant tabular body. A non-tabular intrusive body is further classified by size. Stock is a term, used for a non-tabular body, exposed for less than 100 Km2, batholith is used to describe anything exposed for larger than 100 Km2; this size classification does not take into account the true size of the body, why some ambiguity in the use of pluton came about. A non-tabular body can be classified based on shape, if the bottom of the body is parallel with the underlying country rock it is termed a laccolith. If the bottom of the body is a basin and the top of the body is flat it is a lopolith.
A laccolith is thought to be formed. The horizontal movement of the magma is limited by the viscosity, which leads to the magma pushing the rock above it up creating a dome shape. Lopoliths are believed to have a more mafic, therefore less viscous, source. Lopoliths tend to be larger than laccoliths, are believed to get their lenticular shape from the weight of the intruding magma compressing the underlying country rock, or the shape comes from the evacuation of a magma chamber below the intruding magma, causing the country rock to collapse and creating a basin; some of these terms might be outdated, not describe the shape of a pluton but they are still used. Plutons are believed to be formed from either one single magmatic event, or several incremental events. Recent evidence suggests. While there is little visual evidence of multiple injections in the field, there is geochemical evidence. Zircon zoning is a key part to determining if a single magmatic event or a series of injections were the methods of emplacement.
Another side of the incremental theory is that plutons formed from the amalgamation of small intrusions. The incremental model suggests that there is more time in-between injections to account for the fractional crystallization that allows the newest injection to go in to the least crystallized part of the body. Methods of pluton emplacement Subvolcanic rock Volcanic rock Glazner, A. F. Bartley, J. M. Coleman, D. S. Gray, W. and Taylor, R. Z.. "Are plutons assembled over millions of years by amalgamation from small magma chambers?" GSA Today, 14, pp. 4–11. Young, Davis A.. Mind Over Magma: the Story of Igneous Petrology. Princeton University Press. ISBN 0-691-10279-1. Best, Myron G.. Igneous and Metamorphic Petrology. San Francisco: W. H. Freeman & Company. Pp. 119 ff. ISBN 0-7167-1335-7
Radiometric dating, radioactive dating or radioisotope dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay; the use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of the Earth itself, can be used to date a wide range of natural and man-made materials. Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale. Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating. By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.
Radiometric dating is used to date archaeological materials, including ancient artifacts. Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied. All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide; some nuclides are inherently unstable. That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide; this transformation may be accomplished in a number of different ways, including alpha decay and beta decay. Another possibility is spontaneous fission into two or more nuclides. While the moment in time at which a particular nucleus decays is unpredictable, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life given in units of years when discussing dating techniques.
After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a "daughter" nuclide or decay product. In many cases, the daughter nuclide itself is radioactive, resulting in a decay chain ending with the formation of a stable daughter nuclide. In these cases the half-life of interest in radiometric dating is the longest one in the chain, the rate-limiting factor in the ultimate transformation of the radioactive nuclide into its stable daughter. Isotopic systems that have been exploited for radiometric dating have half-lives ranging from only about 10 years to over 100 billion years. For most radioactive nuclides, the half-life depends on nuclear properties and is a constant, it is not affected by external factors such as temperature, chemical environment, or presence of a magnetic or electric field. The only exceptions are nuclides that decay by the process of electron capture, such as beryllium-7, strontium-85, zirconium-89, whose decay rate may be affected by local electron density.
For all other nuclides, the proportion of the original nuclide to its decay products changes in a predictable way as the original nuclide decays over time. This predictability allows the relative abundances of related nuclides to be used as a clock to measure the time from the incorporation of the original nuclides into a material to the present; the basic equation of radiometric dating requires that neither the parent nuclide nor the daughter product can enter or leave the material after its formation. The possible confounding effects of contamination of parent and daughter isotopes have to be considered, as do the effects of any loss or gain of such isotopes since the sample was created, it is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration. Precision is enhanced if measurements are taken on multiple samples from different locations of the rock body. Alternatively, if several different minerals can be dated from the same sample and are assumed to be formed by the same event and were in equilibrium with the reservoir when they formed, they should form an isochron.
This can reduce the problem of contamination. In uranium–lead dating, the concordia diagram is used which decreases the problem of nuclide loss. Correlation between different isotopic dating methods may be required to confirm the age of a sample. For example, the age of the Amitsoq gneisses from western Greenland was determined to be 3.6 ± 0.05 million years ago using uranium–lead dating and 3.56 ± 0.10 Ma using lead–lead dating, results that are consistent with each other. Accurate radiometric dating requires that the parent has a long enough half-life that it will be present in significant amounts at the time of measurement, the half-life of the parent is known, enough of the daughter product is produced to be measured and distinguished from the initial amount of the daughter present in the material; the procedures used to isolate and analyze the parent and daughter nuclides must be precise and accurate. This involves isotope-ratio mass spectrometry; the precision of
Thomas Wilson Dibblee, Jr. was an American geologist best known for his geological mapping. He is known, together with co-author Mason Hill, for the assertion in 1953 that hundreds of miles of lateral movement had taken place along the San Andreas Fault in California, an idea, radical at the time, but, vindicated by work and the modern theory of plate tectonics. Dibblee was one of the most prolific field geologists in American history, over a 60-year career of field mapping, including 25 years with the US Geological Survey, left a legacy of 40,000 square miles of geologic maps, covering one fourth of the state of California. Dibblee was born in the eldest son of Thomas Dibblee Sr. and Anita Oreña Dibblee. His earliest California ancestor was Captain José de la Guerra y Noriega, the Comandante of the Presidio of Santa Barbara. Dibblee grew up on one of the Dibblee - de la Guerra family ranches, he became interested in geology as a boy, when he assisted a geologist who surveyed the family ranch for oil-bearing structures.
After graduating from Stanford University in 1936, Dibblee worked for the California Division of Mines went to work for Union Oil Company and Richfield Oil as a field exploration petroleum geologist. His field mapping led to the discovery of the Russell Ranch Oil Field, the first oil field to be found in the Cuyama Valley, in 1948, to the nearby larger South Cuyama Oil Field in 1949. Dibblee was known for "roughing it" during his field mapping trips, for which he dropped out of sight for a week or two at a time; when he submitted one expense account totaling $14.92 for one such mapping project, his Richfield Oil supervisor objected that he couldn't have fed himself for that amount, to which Dibblee replied: "Oh, I find lots of things I like to eat up in the hills." He joined the US Geological Survey in 1952, was assigned to geologic mapping in the Mojave Desert. In 1953 he and co-worker Mason Hill published a paper proposing 350 miles of lateral movement along the San Andreas Fault. At that time, prior to plate tectonics theory, there was no known mechanism that could cause such large-scale movements.
Dibblee retired from the USGS in 1977, the following year began mapping the geology of the Los Padres National Forest as a volunteer. Although "retired," he mapped the geology of more than 3,000 square miles in the national forest. In 1949 Dibblee married Loretta Escabosa, they had a long marriage, with no children. Loretta died in 2001. Dibblee died at age 93, in Santa Barbara. US Geological Survey - Distinguished Service Award, 1967 American Association of Petroleum Geologists - Human Needs Award, 1981 Presidential Volunteer Action Award, 1983 The Dibblee Geological Foundation was established to publish Dibblee's many unpublished geological maps. In 2002 the foundation was adopted by the Santa Barbara Museum of Natural History; the foundation continues to publish maps based on Dibblee's work. “San Andreas and Big Pine faults, California,” Geological Society of America Bulletin, April 1953, p. 443-458. This is considered a classic publication in the history of plate tectonics theory
Dime (United States coin)
The dime, in United States usage, is a ten-cent coin, one tenth of a United States dollar, labeled formally as "one dime". The denomination was first authorized by the Coinage Act of 1792; the dime is the smallest in diameter and is the thinnest of all U. S. coins minted for circulation, being.705 inch in diameter and.053 inch in thickness. The obverse of the coin depicts the profile of President Franklin D. Roosevelt and the reverse boasts an olive branch, a torch, an oak branch, from left to right respectively; as of 2011, the dime coin cost 5.65 cents to produce. The word dime comes from the French word dîme, meaning "tithe" or "tenth part", from the Latin decima. In the past prices have been quoted on signage and other materials in terms of dimes, abbreviated as "d" or a lowercase "d" with a slash through it as with the cent and mill signs; the Coinage Act of 1792 established the dime and mill. As subdivisions of the dollar equal to 1⁄10, 1⁄100 and 1⁄1000 dollar respectively; the first known proposal for a decimal-based coinage system in the United States was made in 1783 by Thomas Jefferson, Benjamin Franklin, Alexander Hamilton, David Rittenhouse.
Hamilton, the nation's first Secretary of the Treasury, recommended the issuance of six such coins in 1791, in a report to Congress. Among the six was a silver coin, "which shall be, in weight and value, one tenth part of a silver unit or dollar". From 1796 to 1837, dimes were composed of 89.24% silver and 10.76% copper, the value of which required the coins to be physically small to prevent their intrinsic value being worth more than face value. Thus dimes are made thin; the silver percentage was increased to 90.0% with the introduction of the Seated Liberty dime. With the passage of the Coinage Act of 1965, the dime's silver content was removed. Dimes from 1965 to the present are composed of outer layers of 75% copper and 25% nickel, bonded to a pure copper core. Starting in 1992, the U. S. Mint began issuing Silver Proof Sets annually, which contain dimes composed of the pre-1965 standard of 90% silver and 10% copper; these sets are intended for collectors, are not meant for general circulation.
Since its introduction in 1796, the dime has been issued in six different major types, excluding the 1792 "disme". The name for each type indicates the design on the coin's obverse. Draped Bust 1796–1807 Capped Bust 1809–1837 Seated Liberty 1837–1891 Barber 1892–1916 Winged Liberty Head 1916–1945 Roosevelt 1946–present The Coinage Act of 1792, passed on April 2, 1792, authorized the mintage of a "disme", one-tenth the silver weight and value of a dollar; the composition of the disme was set at 10.76 % copper. In 1792, a limited number of dismes were never circulated; some of these were struck in copper. The first dimes minted for circulation did not appear until 1796, due to a lack of demand for the coin and production problems at the United States Mint; the first dime to be circulated was the Draped Bust dime, in 1796. It featured the same obverse and reverse as all other circulating coins of the time, the so-called Draped Bust/Small Eagle design; this design was the work of then-Chief Engraver Robert Scot.
The portrait of Liberty on the obverse was based on a Gilbert Stuart drawing of prominent Philadelphia socialite Ann Willing Bingham, wife of noted American statesman William Bingham. The reverse design is of a small bald eagle surrounded by palm and olive branches, perched on a cloud. Since the Coinage Act of 1792 required only that the cent and half cent display their denomination, Draped Bust dimes were minted with no indication of their value. All 1796 dimes have 15 stars on the obverse, representing the number of U. S. states in the Union. The first 1797 dimes were minted with 16 stars. Realizing that the practice of adding one star per state could clutter the coin's design, U. S. Mint Director Elias Boudinot ordered a design alteration. Therefore, 1797 dimes can be found with either 16 stars. Designed by Robert Scot, the Heraldic Eagle reverse design made its debut in 1798; the obverse continued from the previous series, but the eagle on the reverse was changed from the criticized "scrawny" hatchling to a scaled-down version of the Great Seal of the United States.
The Draped Bust/Heraldic Eagles series continued through 1807. Both Draped Bust designs were composed of 10.76 % copper. In all, there are 31 varieties of Draped Bust dimes; the Draped Bust design was succeeded by the Capped Bust, designed by Mint Assistant Engraver John Reich. Both the obverse and reverse were changed extensively; the new reverse featured a bald eagle grasping an olive branch. Covering the eagle's breast is a U. S. shield with 13 vertical stripes. On the reverse is the lettering "10C," making it the only dime minted with the value given in cents; the lack of numeric value markings on subsequent dime coins causes some confusion amongst foreign visitors, who may be unaware of the value of the coin. The Capped Bust dime was the first dime to have its value written on the coin. Previous designs of the dime had no indication of its value, the way people determined its value was by its sizeCappe
1999 İzmit earthquake
The 1999 İzmit earthquake occurred on 17 August at 03:01:40 local time in northwestern Turkey. The shock had a moment magnitude of 7.6 and a maximum Mercalli intensity of IX. The event lasted for 37 seconds, killing around 17,000 people and left half a million people homeless; the nearby city of İzmit was damaged. The earthquake occurred along the western portion of the North Anatolian Fault Zone; the Anatolian Plate, which consists of Turkey, is being pushed west about 2–2.5 cm a year, as it is squeezed between the Eurasian Plate to the north and the Arabian Plate to the south. Major earthquakes in Turkey result from slip along the NAFZ or the East Anatolian Fault; the Izmit earthquake had a rupture length of 150 kilometers extending from the city of Düzce all the way into the Sea of Marmara along the Gulf of İzmit. Offsets along the rupture were as large as 5.7 meters. From the timing of P-wave and S-wave arrivals at seismometers there is strong evidence that the rupture propagated eastwards from the epicentre at speeds in excess of the S-wave velocity, making this a supershear earthquake.
Destruction in Istanbul was concentrated in the Avcılar district to the west of the city. Avcılar was built on weak ground composed of poorly consolidated Cenozoic sedimentary rocks, which makes this district vulnerable to any earthquake; the earthquake was felt in this industrialized and densely populated urban area of the country, including oil refineries, several automotive plants, the Turkish navy headquarters and arsenal in Gölcük, increasing the severity of the loss of life and property. The earthquake caused considerable damage in Istanbul, about 70 kilometres away from the earthquake's epicenter. An official Turkish estimate of October 19, 1999, placed the toll at 17,127 killed and 43,959 injured, but many sources suggest the actual figure may have been closer to 45,000 dead and a similar number injured. Reports from September 1999 show that 120,000 poorly engineered houses were damaged beyond repair, 30,000 houses were damaged, 2,000 other buildings collapsed and 4,000 other buildings were damaged.
300,000 people were left homeless after the earthquake. There was extensive damage to several bridges and other structures on the Trans-European Motorway, including 20 viaducts, 5 tunnels, some overpasses. Damage ranged from spalling concrete to total deck collapse; the earthquake sparked a disastrous fire at the Tüpraş petroleum refinery. The fire began at a state-owned tank farm and was initiated by naphtha that had sloshed out of a holding tank. Breakage in water pipelines, results of the quake, nullified attempts at extinguishing the fire. Aircraft were called in to douse the flames with foam; the fire spread over the next few days, warranting the evacuation of the area within three miles of the refinery. The fire was declared under control five days after claiming at least seventeen tanks and untold amounts of complex piping; the earthquake caused a tsunami in the Sea of Marmara, about 2.5 meters high. The tsunami caused the deaths of 155 people. A massive international response was mounted to assist in digging for survivors and assisting the wounded and homeless.
Rescue teams were dispatched within 24–48 hours of the disaster, the assistance to the survivors was channeled through NGOs and the Red Crescent and local search and rescue organizations. The following table shows the breakdown of rescue teams by country in the affected locations: Search and Rescue Effort as of August 19, 1999. Source: USAIDIn total, rescue teams from twelve countries assisted in the rescue effort. Oil Spill Response Limited were activated by BP to deploy from the United Kingdom to the Tupras Refinery where their responders contained the uncontrolled discharge of oil from the site into the sea; the U. K announced an immediate grant of £50,000 to help the Turkish Red Crescent, while the International Red Cross and Red Crescent pledged £4.5 million to help victims. Blankets, medical supplies and food were flown from Stansted airport. Engineers from Thames Water went to help restore water supplies. India assisted by providing 32,000 tents and 2 million rupees to help in the reconstruction process.
US President Bill Clinton and Pakistani Prime Minister Nawaz Sharif visited Istanbul and İzmit to examine the level of destruction and meet with the survivors. List of earthquakes in 1999 List of earthquakes in Turkey Yalova Earthquake Monument M7.6 - western Turkey – United States Geological Survey 17 August 1999 Kocaeli Earthquake – The European Association for Earthquake Engineering Initial Geotechnical Observations of the August 17, 1999, Izmit Earthquake – National Information Service for Earthquake Engineering The International Seismological Centre has a bibliography and/or authoritative data for this event. ReliefWeb's main page for this event