1.
Percentage
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In mathematics, a percentage is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, %, or the abbreviations pct. pct, a percentage is a dimensionless number. For example, 45% is equal to 45⁄100,45,100, percentages are often used to express a proportionate part of a total. If 50% of the number of students in the class are male. If there are 1000 students, then 500 of them are male, an increase of $0.15 on a price of $2.50 is an increase by a fraction of 0. 15/2.50 =0.06. Expressed as a percentage, this is a 6% increase, while many percentage values are between 0 and 100, there is no mathematical restriction and percentages may take on other values. For example, it is common to refer to 111% or −35%, especially for percent changes, in Ancient Rome, long before the existence of the decimal system, computations were often made in fractions which were multiples of 1⁄100. For example, Augustus levied a tax of 1⁄100 on goods sold at auction known as centesima rerum venalium, computation with these fractions was equivalent to computing percentages. Many of these texts applied these methods to profit and loss, interest rates, by the 17th century it was standard to quote interest rates in hundredths. The term per cent is derived from the Latin per centum, the sign for per cent evolved by gradual contraction of the Italian term per cento, meaning for a hundred. The per was often abbreviated as p. and eventually disappeared entirely, the cento was contracted to two circles separated by a horizontal line, from which the modern % symbol is derived. The percent value is computed by multiplying the value of the ratio by 100. For example, to find 50 apples as a percentage of 1250 apples, first compute the ratio 50⁄1250 =0.04, and then multiply by 100 to obtain 4%. The percent value can also be found by multiplying first, so in this example the 50 would be multiplied by 100 to give 5,000, and this result would be divided by 1250 to give 4%. To calculate a percentage of a percentage, convert both percentages to fractions of 100, or to decimals, and multiply them, for example, 50% of 40% is, 50⁄100 × 40⁄100 =0.50 ×0.40 =0.20 = 20⁄100 = 20%. It is not correct to divide by 100 and use the percent sign at the same time, whenever we talk about a percentage, it is important to specify what it is relative to, i. e. what is the total that corresponds to 100%. The following problem illustrates this point, in a certain college 60% of all students are female, and 10% of all students are computer science majors. If 5% of female students are computer science majors, what percentage of computer science majors are female and we are asked to compute the ratio of female computer science majors to all computer science majors
2.
Industrial computed tomography
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Industrial CT scanning has been used in many areas of industry for internal inspection of components. Some of the key uses for CT scanning have been flaw detection, failure analysis, metrology, assembly analysis, just as in medical imaging, industrial imaging includes both nontomographic radiography and computed tomographic radiography. Fan/line beam scanners-translate Line scanners are the first generation of industrial CT Scanners, X-rays are produced and the beam is collimated to create a line. The X-ray line beam is translated across the part and data is collected by the detector. The data is reconstructed to create a 3-D Volume rendering of the part. Cone beam scanners-rotate During the CT scan the part is placed on a rotary table, as the part rotates the cone of X-rays produce about 1300 2D images which are collected by the detector. The 2D images are processed to create a 3D volume rendering of the external and internal geometries of the part. Industrial CT scanning technology was introduced in 1972 with the invention of the CT scanner by G. Hounsfield, the invention earned him a Nobel Prize in medicine, which he shared with Allan Cormack. Many advances in CT scanning have allowed for its use in the field for metrology in addition to the visual inspection primarily used in the medical field. Assembly Inspection, One of the most recognized forms of analysis using CT is for assembly, CT scanning has been largely used as an imaging tool for medical purposes. For industrial CT scanning, the ability to see inside a component is very beneficial, some software programs for industrial CT scanning allow for measurements to be taken from the CT dataset volume rendering. These measurements are useful for determining the clearances between assembled parts or simply a dimension of an individual feature, in today’s market parts can be manufactured around the world, designed in one country, machined in another and assembled in a third. Verification of the part to the original CAD design is critical, industrial computed tomography allows for a comparison of parts to one another or parts to CAD data. The deviations for both external and internal geometries can be shown on the colour map chromatically on the 3D representation or by whisker plots in the 2D windows. Traditionally, determining defects, voids and cracks within an object would require destructive testing, CT scanning can detect internal features and flaws displaying this information in 3D without destroying the part. Industrial CT scanning is used to detect flaws inside a part such as porosity, in some software programs the porosity within a part is categorized by colour based on their respective sizes. Metal casting and moulded plastic components are typically prone to porosity because of cooling processes, void analysis can be used to locate, measure, and analyze voids inside plastic or metal components. A CAD file can be generated from the CT data set, exported CAD file formats are recognized by many software such as CAD, FEA, and CFD
3.
Ceramic engineering
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Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions, Ceramic materials may have a crystalline or partly crystalline structure, with long-range order on atomic scale. Glass ceramics may have an amorphous or glassy structure, with limited or short-range atomic order, the special character of ceramic materials gives rise to many applications in materials engineering, electrical engineering, chemical engineering and mechanical engineering. As ceramics are heat resistant, they can be used for many tasks for which materials like metal, the word ceramic is derived from the Greek word κεραμικός meaning pottery. It is related to the older Indo-European language root to burn, Ceramic may be used as a noun in the singular to refer to a material or the product of ceramic manufacture. The plural ceramics may be used to refer the making of things out of ceramic materials, Ceramic engineering, like many sciences, evolved from a different discipline by todays standards. Materials science engineering is grouped with ceramics engineering to this day, abraham Darby first used coke in 1709 in Shropshire, England, to improve the yield of a smelting process. Coke is now used to produce carbide ceramics. Potter Josiah Wedgwood opened the first modern factory in Stoke-on-Trent, England. Austrian chemist Carl Josef Bayer, working for the industry in Russia. The Bayer process is used to purify alumina for the ceramic. Brothers Pierre and Jacques Curie discovered piezoelectricity in Rochelle salt circa 1880, piezoelectricity is one of the key properties of electroceramics. Acheson heated a mixture of coke and clay in 1893, and invented carborundum, henri Moissan also synthesized SiC and tungsten carbide in his electric arc furnace in Paris about the same time as Acheson. Karl Schröter used liquid-phase sintering to bond or cement Moissans tungsten carbide particles with cobalt in 1923 in Germany, cemented carbide edges greatly increase the durability of hardened steel cutting tools. W. H. Nernst developed cubic-stabilized zirconia in the 1920s in Berlin and this material is used as an oxygen sensor in exhaust systems. The main limitation on the use of ceramics in engineering is brittleness, the military requirements of World War II encouraged developments, which created a need for high-performance materials and helped speed the development of ceramic science and engineering. Throughout the 1960s and 1970s, new types of ceramics were developed in response to advances in energy, electronics, communications. The discovery of ceramic superconductors in 1986 has spurred intense research to develop superconducting ceramic parts for electronic devices, electric motors, and transportation equipment
4.
Metallurgy
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The production of metals involves the processing of ores to extract the metal they contain, and the mixture of metals, sometimes with other elements, to produce alloys. Metallurgy is distinguished from the craft of metalworking, although metalworking relies on metallurgy, as medicine relies on medical science, Metallurgy is subdivided into ferrous metallurgy and non-ferrous metallurgy or colored metallurgy. Ferrous metallurgy involves processes and alloys based on iron while non-ferrous metallurgy involves processes, the production of ferrous metals accounts for 95 percent of world metal production. The roots of metallurgy derive from Ancient Greek, μεταλλουργός, metallourgós, worker in metal, from μέταλλον, métallon, metal + ἔργον, érgon, in the late 19th century it was extended to the more general scientific study of metals, alloys, and related processes. In English, the pronunciation is the more common one in the UK. The /ˈmetələrdʒi/ pronunciation is the common one in the USA. The earliest recorded metal employed by humans appears to be gold, small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c.40,000 BC. Silver, copper, tin and meteoric iron can also be found in native form, egyptian weapons made from meteoric iron in about 3000 BC were highly prized as daggers from heaven. Certain metals, notably tin, lead and copper, can be recovered from their ores by simply heating the rocks in a fire or blast furnace, a process known as smelting. The first evidence of this extractive metallurgy dates from the 5th and 6th millennia BC and was found in the sites of Majdanpek, Yarmovac and Plocnik. To date, the earliest evidence of copper smelting is found at the Belovode site, other signs of early metals are found from the third millennium BC in places like Palmela, Los Millares, and Stonehenge. However, the ultimate beginnings cannot be ascertained and new discoveries are both continuous and ongoing. These first metals were single ones or as found, about 3500 BC, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze, representing a major technological shift known as the Bronze Age. The extraction of iron from its ore into a metal is much more difficult than for copper or tin. The process appears to have been invented by the Hittites in about 1200 BC, the secret of extracting and working iron was a key factor in the success of the Philistines. Historical developments in ferrous metallurgy can be found in a variety of past cultures. A 16th century book by Georg Agricola called De re metallica describes the highly developed and complex processes of mining metal ores, metal extraction, Agricola has been described as the father of metallurgy. Extractive metallurgy is the practice of removing valuable metals from an ore, in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically
5.
Materials science
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The interdisciplinary field of materials science, also commonly termed materials science and engineering, involves the discovery and design of new materials, with an emphasis on solids. Materials science still incorporates elements of physics, chemistry, and engineering, as such, the field was long considered by academic institutions as a sub-field of these related fields. Materials science is a syncretic discipline hybridizing metallurgy, ceramics, solid-state physics and it is the first example of a new academic discipline emerging by fusion rather than fission. Many of the most pressing scientific problems humans currently face are due to the limits of the materials that are available, thus, breakthroughs in materials science are likely to affect the future of technology significantly. Materials scientists emphasize understanding how the history of a material influences its structure, the understanding of processing-structure-properties relationships is called the § materials paradigm. This paradigm is used to advance understanding in a variety of areas, including nanotechnology, biomaterials. Such investigations are key to understanding, for example, the causes of various accidents and incidents. The material of choice of a given era is often a defining point, phrases such as Stone Age, Bronze Age, Iron Age, and Steel Age are great examples. Originally deriving from the manufacture of ceramics and its putative derivative metallurgy, materials science is one of the oldest forms of engineering, modern materials science evolved directly from metallurgy, which itself evolved from mining and ceramics and the use of fire. Materials science has driven, and been driven by, the development of technologies such as rubbers, plastics, semiconductors. Before the 1960s, many materials science departments were named metallurgy departments, reflecting the 19th, a material is defined as a substance that is intended to be used for certain applications. There are a myriad of materials around us—they can be found in anything from buildings to spacecraft, Materials can generally be divided into two classes, crystalline and non-crystalline. The traditional examples of materials are metals, semiconductors, ceramics, New and advanced materials that are being developed include nanomaterials and biomaterials, etc. The basis of science involves studying the structure of materials. Once a materials scientist knows about this structure-property correlation, they can go on to study the relative performance of a material in a given application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and these characteristics, taken together and related through the laws of thermodynamics and kinetics, govern a materials microstructure, and thus its properties. As mentioned above, structure is one of the most important components of the field of materials science, Materials science examines the structure of materials from the atomic scale, all the way up to the macro scale. Characterization is the way materials scientists examine the structure of a material, structure is studied at various levels, as detailed below
6.
Manufacturing
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Manufacturing is the value added to production of merchandise for use or sale using labour and machines, tools, chemical and biological processing, or formulation. Manufacturing engineering or manufacturing process are the steps through which raw materials are transformed into a final product, the manufacturing process begins with the product design, and materials specification from which the product is made. These materials are modified through manufacturing processes to become the required part. Manufacturing takes turns under all types of economic systems, in a free market economy, manufacturing is usually directed toward the mass production of products for sale to consumers at a profit. In a collectivist economy, manufacturing is more directed by the state to supply a centrally planned economy. In mixed market economies, manufacturing occurs under some degree of government regulation, modern manufacturing includes all intermediate processes required the production and integration of a products components. Some industries, such as semiconductor and steel manufacturers use the term fabrication instead, the manufacturing sector is closely connected with engineering and industrial design. Examples of major manufacturers in North America include General Motors Corporation, General Electric, Procter & Gamble, General Dynamics, Boeing, Pfizer, examples in Europe include Volkswagen Group, Siemens, and Michelin. Examples in Asia include Sony, Huawei, Lenovo, Toyota, Samsung, in its earliest form, manufacturing was usually carried out by a single skilled artisan with assistants. In much of the world, the guild system protected the privileges. Before the Industrial Revolution, most manufacturing occurred in rural areas, entrepreneurs organized a number of manufacturing households into a single enterprise through the putting-out system. Toll manufacturing is an arrangement whereby a first firm with specialized equipment processes raw materials or semi-finished goods for a second firm, manufacturing provides important material support for national infrastructure and for national defense. On the other hand, most manufacturing may involve significant social and environmental costs, the clean-up costs of hazardous waste, for example, may outweigh the benefits of a product that creates it. Hazardous materials may expose workers to health risks and these costs are now well known and there is effort to address them by improving efficiency, reducing waste, using industrial symbiosis, and eliminating harmful chemicals. The negative costs of manufacturing can also be addressed legally, developed countries regulate manufacturing activity with labor laws and environmental laws. Across the globe, manufacturers can be subject to regulations and pollution taxes to offset the costs of manufacturing activities. Labor unions and craft guilds have played a role in the negotiation of worker rights. Environment laws and labor protections that are available in developed nations may not be available in the third world, tort law and product liability impose additional costs on manufacturing
7.
Earth science
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Earth science or geoscience is a widely embraced term for the fields of science related to the planet Earth. Earth science can be considered to be a branch of planetary science, there are both reductionist and holistic approaches to Earth sciences. The Earth sciences can include the study of geology, the lithosphere, and the structure of the Earths interior, as well as the atmosphere, hydrosphere. Typically, Earth scientists use tools from geography, chronology, physics, chemistry, biology, Geology describes the rocky parts of the Earths crust and its historic development. Major subdisciplines are mineralogy and petrology, geochemistry, geomorphology, paleontology, stratigraphy, structural geology, engineering geology, geophysics and geodesy investigate the shape of the Earth, its reaction to forces and its magnetic and gravity fields. Geophysicists explore the Earths core and mantle as well as the tectonic and seismic activity of the lithosphere, geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration. Soil science covers the outermost layer of the Earths crust that is subject to soil formation processes, major subdisciplines include edaphology and pedology. Ecology covers the interactions between the biota, with their natural environment and this field of study differentiates the study of the Earth, from the study of other planets in the Solar System, the Earth being the only planet teeming with life. Hydrology is a study revolved around the movement, distribution, and quality of the water and involves all the components of the cycle on the earth. Sub-disciplines of hydrology include hydrometeorology, surface hydrology, hydrogeology, watershed science, forest hydrology. Glaciology covers the icy parts of the Earth, atmospheric sciences cover the gaseous parts of the Earth between the surface and the exosphere. Major subdisciplines include meteorology, climatology, atmospheric chemistry, and atmospheric physics, plate tectonics, mountain ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the Earths crust. Beneath the Earths crust lies the mantle which is heated by the decay of heavy elements. The mantle is not quite solid and consists of magma which is in a state of semi-perpetual convection and this convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics, plate tectonics might be thought of as the process by which the Earth is resurfaced. As the result of spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures. Through subduction, oceanic crust and lithosphere returns to the convecting mantle, volcanoes result primarily from the melting of subducted crust material. Crust material that is forced into the asthenosphere melts, and some portion of the material becomes light enough to rise to the surface—giving birth to volcanoes
8.
Soil mechanics
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Soil mechanics is a branch of soil physics and engineering mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a mixture of fluids and particles but soil may also contain organic solids. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems. Principles of soil mechanics are used in related disciplines such as engineering geology, geophysical engineering, coastal engineering, agricultural engineering, hydrology. The shear strength of soils is primarily derived from friction between the particles and interlocking, which are sensitive to the effective stress. The article concludes with examples of applications of the principles of soil mechanics such as slope stability, lateral earth pressure on retaining walls. The primary mechanism of soil creation is the weathering of rock, all rock types may be broken down into small particles to create soil. Weathering mechanisms are physical weathering, chemical weathering, and biological weathering Human activities such as excavation, blasting, physical weathering includes temperature effects, freeze and thaw of water in cracks, rain, wind, impact and other mechanisms. Chemical weathering includes dissolution of matter composing a rock and precipitation in the form of another mineral, clay minerals, for example can be formed by weathering of feldspar, which is the most common mineral present in igneous rock. The most common constituent of silt and sand is quartz, also called silica. The reason that feldspar is most common in rocks but silicon is more prevalent in soils is that feldspar is much more soluble than silica, silt, Sand, and Gravel are basically little pieces of broken rocks. Particles larger than gravel are called cobbles and boulders, Soil deposits are affected by the mechanism of transport and deposition to their location. Soils that are not transported are called residual soils—they exist at the location as the rock from which they were generated. Decomposed granite is an example of a residual soil. The common mechanisms of transport are the actions of gravity, ice, water, wind blown soils include dune sands and loess. Water carries particles of different size depending on the speed of the water, silt and clay may settle out in a lake, and gravel and sand collect at the bottom of a river bed. Wind blown soil deposits also tend to be sorted according to their grain size. Erosion at the base of glaciers is powerful enough to pick up rocks and boulders as well as soil
9.
Engineering
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The term Engineering is derived from the Latin ingenium, meaning cleverness and ingeniare, meaning to contrive, devise. Engineering has existed since ancient times as humans devised fundamental inventions such as the wedge, lever, wheel, each of these inventions is essentially consistent with the modern definition of engineering. The term engineering is derived from the engineer, which itself dates back to 1390 when an engineer originally referred to a constructor of military engines. In this context, now obsolete, a referred to a military machine. Notable examples of the obsolete usage which have survived to the present day are military engineering corps, the word engine itself is of even older origin, ultimately deriving from the Latin ingenium, meaning innate quality, especially mental power, hence a clever invention. The earliest civil engineer known by name is Imhotep, as one of the officials of the Pharaoh, Djosèr, he probably designed and supervised the construction of the Pyramid of Djoser at Saqqara in Egypt around 2630–2611 BC. Ancient Greece developed machines in both civilian and military domains, the Antikythera mechanism, the first known mechanical computer, and the mechanical inventions of Archimedes are examples of early mechanical engineering. In the Middle Ages, the trebuchet was developed, the first steam engine was built in 1698 by Thomas Savery. The development of this gave rise to the Industrial Revolution in the coming decades. With the rise of engineering as a profession in the 18th century, similarly, in addition to military and civil engineering, the fields then known as the mechanic arts became incorporated into engineering. The inventions of Thomas Newcomen and the Scottish engineer James Watt gave rise to mechanical engineering. The development of specialized machines and machine tools during the revolution led to the rapid growth of mechanical engineering both in its birthplace Britain and abroad. John Smeaton was the first self-proclaimed civil engineer and is regarded as the father of civil engineering. He was an English civil engineer responsible for the design of bridges, canals, harbours and he was also a capable mechanical engineer and an eminent physicist. Smeaton designed the third Eddystone Lighthouse where he pioneered the use of hydraulic lime and his lighthouse remained in use until 1877 and was dismantled and partially rebuilt at Plymouth Hoe where it is known as Smeatons Tower. The United States census of 1850 listed the occupation of engineer for the first time with a count of 2,000, there were fewer than 50 engineering graduates in the U. S. before 1865. In 1870 there were a dozen U. S. mechanical engineering graduates, in 1890 there were 6,000 engineers in civil, mining, mechanical and electrical. There was no chair of applied mechanism and applied mechanics established at Cambridge until 1875, the theoretical work of James Maxwell and Heinrich Hertz in the late 19th century gave rise to the field of electronics
10.
Two-phase flow
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In fluid mechanics, two-phase flow is a flow of gas and liquid usually in a pipe. Two-phase flow is an example of multiphase flow. Two-phase flow can occur in various forms, the widely-accepted method to categorize two-phase flows is to consider the velocity of each phase as if there is not other phases available. The parameter is a concept called Superficial velocity. Historically, probably the most commonly studied cases of two-phase flow are in power systems. Coal and gas-fired power stations used very large boilers to produce steam for use in turbines, in such cases, pressurised water is passed through heated pipes and it changes to steam as it moves through the pipe. The design of boilers requires an understanding of two-phase flow heat-transfer and pressure drop behaviour. Even more critically, nuclear reactors use water to heat from the reactor core using two-phase flow. A great deal of study has been performed on the nature of flow in such cases, so that engineers can design against possible failures in pipework, loss of pressure. Another case where two-phase flow can occur is in pump cavitation, here a pump is operating close to the vapor pressure of the fluid being pumped. If pressure drops further, which can happen locally near the vanes for the pump, for example, then a change can occur. Similar effects can occur on marine propellors, wherever it occurs. When the vapor bubble collapses, it can produce very large pressure spikes, the above two-phase flow cases are for a single fluid occurring by itself as two different phases, such as steam and water. The term two-phase flow is applied to mixtures of different fluids having different phases, such as air and water, or oil. Sometimes even three-phase flow is considered, such as in oil, other interesting areas where two-phase flow is studied includes in climate systems such as clouds, and in groundwater flow, in which the movement of water and air through the soil is studied. Other examples of two-phase flow include bubbles, rain, waves on the sea, foam, fountains, mousse, cryogenics, several features make two-phase flow an interesting and challenging branch of fluid mechanics, Surface tension makes all dynamical problems nonlinear. In the case of air and water at temperature and pressure. Similar differences are typical of water liquid/water vapor densities, the sound speed changes dramatically for materials undergoing phase change, and can be orders of magnitude different
11.
Volumetric flow rate
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In physics and engineering, in particular fluid dynamics and hydrometry, the volumetric flow rate, is the volume of fluid which passes per unit time, usually represented by the symbol Q. In US customary units and imperial units, volumetric flow rate is expressed as ft3/s or gallons per minute. Volumetric flow rate should not be confused with volumetric flux, as defined by Darcys law and represented by the symbol q, with units of m3/, the integration of a flux over an area gives the volumetric flow rate. Since this is only the derivative of volume, a scalar quantity. Volumetric flow rate can also be defined by, Q = v ⋅ A where, v = flow velocity A = cross-sectional vector area/surface The above equation is true for flat. In general, including curved surfaces, the equation becomes a surface integral, the area required to calculate the volumetric flow rate is real or imaginary, flat or curved, either as a cross-sectional area or a surface. The vector area is a combination of the magnitude of the area through which the volume passes through, A, the reason for the dot product is as follows. The only volume flowing through the cross-section is the amount normal to the area and this amount is, Q = v A cos θ where θ is the angle between the unit normal n̂ and the velocity vector v of the substance elements. The amount passing through the cross-section is reduced by the factor cos θ, as θ increases less volume passes through. Substance which passes tangential to the area, that is perpendicular to the unit normal, when the mass flow rate is known, and the density can be assumed constant, this is an easy way to get Q. Q = m ˙ ρ Where, ṁ = mass flow rate, in internal combustion engines, the time area integral is considered over the range of valve opening. This has to be factored by the width of the valve throat, the answer is usually related to the cylinders swept volume. Air to cloth ratio Discharge Flow measurement Flowmeter Orifice plate Poiseuilles law Stokes flow Units of flow
12.
Geology
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Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer generally to the study of the features of any terrestrial planet. Geology gives insight into the history of the Earth by providing the evidence for plate tectonics, the evolutionary history of life. Geology also plays a role in engineering and is a major academic discipline. The majority of data comes from research on solid Earth materials. These typically fall into one of two categories, rock and unconsolidated material, the majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three types of rock, igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between three types of rock, and magma. When a rock crystallizes from melt, it is an igneous rock, the sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism, all three types of rocks may be re-melted, when this happens, a new magma is formed, from which an igneous rock may once again crystallize. Geologists also study unlithified material which typically comes from more recent deposits and these materials are superficial deposits which lie above the bedrock. Because of this, the study of material is often known as Quaternary geology. This includes the study of sediment and soils, including studies in geomorphology, sedimentology and this theory is supported by several types of observations, including seafloor spreading, and the global distribution of mountain terrain and seismicity. This coupling between rigid plates moving on the surface of the Earth and the mantle is called plate tectonics. The development of plate tectonics provided a basis for many observations of the solid Earth. Long linear regions of geologic features could be explained as plate boundaries, mid-ocean ridges, high regions on the seafloor where hydrothermal vents and volcanoes exist, were explained as divergent boundaries, where two plates move apart. Arcs of volcanoes and earthquakes were explained as convergent boundaries, where one plate subducts under another, transform boundaries, such as the San Andreas Fault system, resulted in widespread powerful earthquakes. Plate tectonics also provided a mechanism for Alfred Wegeners theory of continental drift and they also provided a driving force for crustal deformation, and a new setting for the observations of structural geology
13.
Hydrogeology
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Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earths crust. The term geohydrology is often used interchangeably, some make the minor distinction between a hydrologist or engineer applying themselves to geology, and a geologist applying themselves to hydrology. Hydrogeology is a subject, it can be difficult to account fully for the chemical, physical, biological. The study of the interaction between groundwater movement and geology can be quite complex, Groundwater does not always follow the surface topography, groundwater follows pressure gradients, often through fractures and conduits in circuitous paths. Taking into account the interplay of the different facets of a multi-component system often requires knowledge in diverse fields at both the experimental and theoretical levels. The following is a more traditional introduction to the methods and nomenclature of saturated subsurface hydrology, hydrogeology, as stated above, is a branch of the earth sciences dealing with the flow of water through aquifers and other shallow porous media. The very shallow flow of water in the subsurface is pertinent to the fields of science, agriculture and civil engineering. The general flow of fluids in deeper formations is also a concern of geologists, geophysicists, Groundwater is a slow-moving, viscous fluid, many of the empirically derived laws of groundwater flow can be alternately derived in fluid mechanics from the special case of Stokes flow. The mathematical relationships used to describe the flow of water through porous media are the diffusion and Laplace equations, steady groundwater flow has been simulated using electrical, elastic and heat conduction analogies. Transient groundwater flow is analogous to the diffusion of heat in a solid, traditionally, the movement of groundwater has been studied separately from surface water, climatology, and even the chemical and microbiological aspects of hydrogeology. As the field of hydrogeology matures, the interactions between groundwater, surface water, water chemistry, soil moisture and even climate are becoming more clear. For example, aquifer drawdown or overdrafting and the pumping of water may be a contributing factor to sea-level rise. One of the tasks a hydrogeologist typically performs is the prediction of future behavior of an aquifer system, based on analysis of past. Some hypothetical, but characteristic questions asked would be, Can the aquifer support another subdivision, will the river dry up if the farmer doubles his irrigation. Did the chemicals from the dry cleaning facility travel through the aquifer to my well, will the plume of effluent leaving my neighbors septic system flow to my drinking water well. Most of these questions can be addressed through simulation of the hydrologic system, accurate simulation of the aquifer system requires knowledge of the aquifer properties and boundary conditions. Therefore, a task of the hydrogeologist is determining aquifer properties using aquifer tests. In order to further characterize aquifers and aquitards some primary and derived physical properties are introduced below, aquifers are broadly classified as being either confined or unconfined, and either saturated or unsaturated, the type of aquifer affects what properties control the flow of water in that medium
14.
Soil science
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Sometimes terms which refer to branches of soil science, such as pedology and edaphology, are used as if synonymous with soil science. The diversity of names associated with this discipline is related to the various associations concerned, Soil occupies the pedosphere, one of Earths spheres that the geosciences use to organize the Earth conceptually. This is the perspective of pedology and edaphology, the two main branches of soil science. Pedology is the study of soil in its natural setting, edaphology is the study of soil in relation to soil-dependent uses. Both branches apply a combination of physics, soil chemistry. Due to the interactions between the biosphere, atmosphere and hydrosphere that are hosted within the pedosphere, more integrated. Many concepts essential to understanding soil come from individuals not identifiable strictly as soil scientists and this highlights the interdisciplinary nature of soil concepts. Dependence on and curiosity about soil, exploring the diversity and dynamics of this continues to yield fresh discoveries. New avenues of research are compelled by a need to understand soil in the context of climate change, greenhouse gases. Interest in maintaining the biodiversity and in exploring past cultures has also stimulated renewed interest in achieving a more refined understanding of soil. Most empirical knowledge of soil in nature comes from soil survey efforts, Soil survey, or soil mapping, is the process of determining the soil types or other properties of the soil cover over a landscape, and mapping them for others to understand and use. It relies heavily on distinguishing the individual influences of the five classic soil forming factors and this effort draws upon geomorphology, physical geography, and analysis of vegetation and land-use patterns. Primary data for the survey are acquired by field sampling. As of 2006, the World Reference Base for Soil Resources and it replaces the previous FAO soil classification. The WRB borrows from modern soil classification concepts, including USDA soil taxonomy, the classification is based mainly on soil morphology as an expression pedogenesis. A major difference with USDA soil taxonomy is that climate is not part of the system. Many other classification schemes exist, including vernacular systems, the structure in vernacular systems are either nominal, giving unique names to soils or landscapes, or descriptive, naming soils by their characteristics such as red, hot, fat, or sandy. Soils are distinguished by obvious characteristics, such as appearance, performance
15.
Building science
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Building science is the collection of scientific knowledge and experience that focuses on the analysis and control of the physical phenomena affecting buildings and architecture. In Europe, building physics and applied physics are used for the knowledge domain that overlaps with building science. g. Freeze/thaw cycles, dew point/frost point, snow load & drift prediction, under the constraints of characteristics of materials. Energy consumption, environmental control-ability, building maintenance considerations, longevity/sustainability, the building science of a project refers to strategies implemented in the general and specific arrangement of building materials and component-assemblies. The scope can be, and is, much wider than this on most projects, after all, engineering is applied science mixed with experience, even the interior designer will inevitably generate a few building science issues. All kinds of structures are projected according to two conditions, static and dynamic. The parameters which characterize structure dynamics are tied to the geometry of the building and to the physical, the second parameter takes into account all the dissipation phenomena tied to the viscosity of materials and to friction phenomena. The mode shape describes the way of deformation which the structure is subjected to during the seismic event, dissipation systems, there exist various types of dissipation systems, but they all have in common the effect of increasing the previously seen viscous dissipation coefficient of the structure. The better known base isolation technique consists of inserting some special equipment in the proximity of foundations. This equipment offers a high stiffness for vertical loads so that the structure is not subject to sinking, while offering a low stiffness for horizontal ones, which are peculiar of seismic events. This way all seismic effects are absorbed by the equipment, whereas the structure is subject to low oscillations, indoor environmental quality refers to the quality of a building’s environment in relation to the health and wellbeing of those who occupy space within it. IEQ is determined by many factors, including lighting, air quality, workers are often concerned that they have symptoms or health conditions from exposures to contaminants in the buildings where they work. One reason for concern is that their symptoms often get better when they are not in the building. Other factors such as temperatures, relative humidity, and ventilation levels can also affect how individuals respond to the indoor environment. Understanding the sources of environmental contaminants and controlling them can often help prevent or resolve building-related worker symptoms. Practical guidance for improving and maintaining the environment is available. Building indoor environment covers the aspects in the design, analysis, and operation of energy-efficient, healthy. Fields of specialization include architecture, HVAC design, thermal comfort, indoor air quality, lighting, acoustics, the building enclosure is the part of the building that separates the indoors from the outdoors
16.
Porous medium
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A porous medium or a porous material is a material containing pores. The skeletal portion of the material is called the matrix or frame. The pores are filled with a fluid. The skeletal material is usually a solid, but structures like foams are often also usefully analyzed using concept of porous media, a porous medium is most often characterised by its porosity. Other properties of the medium can sometimes be derived from the properties of its constituents and the media porosity and pores structure. Even the concept of porosity is only straightforward for a poroelastic medium, often both the solid matrix and the pore network are continuous, so as to form two interpenetrating continua such as in a sponge. However, there is also a concept of closed porosity and effective porosity, many natural substances such as rocks and soil, zeolites, biological tissues, and man made materials such as cements and ceramics can be considered as porous media. Many of their important properties can only be rationalized by considering them to be porous media, the concept of porous media is used in many areas of applied science and engineering, filtration, mechanics, engineering, geosciences, biology and biophysics, material science, etc. Fluid flow through porous media is a subject of common interest and has emerged a separate field of study, the study of more general behaviour of porous media involving deformation of the solid frame is called poromechanics. There are many idealized models of pore structures and they can be broadly divided into three categories, networks of capillaries, arrays of solid particles, trimodal Nanoporous materials NMR in porous media Percolation theory Reticulated foam
17.
Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
18.
Sediment
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For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
19.
Ratio
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In mathematics, a ratio is a relationship between two numbers indicating how many times the first number contains the second. For example, if a bowl of fruit contains eight oranges and six lemons, thus, a ratio can be a fraction as opposed to a whole number. Also, in example the ratio of lemons to oranges is 6,8. The numbers compared in a ratio can be any quantities of a kind, such as objects, persons, lengths. A ratio is written a to b or a, b, when the two quantities have the same units, as is often the case, their ratio is a dimensionless number. A rate is a quotient of variables having different units, but in many applications, the word ratio is often used instead for this more general notion as well. The numbers A and B are sometimes called terms with A being the antecedent, the proportion expressing the equality of the ratios A, B and C, D is written A, B = C, D or A, B, C, D. This latter form, when spoken or written in the English language, is expressed as A is to B as C is to D. A, B, C and D are called the terms of the proportion. A and D are called the extremes, and B and C are called the means, the equality of three or more proportions is called a continued proportion. Ratios are sometimes used three or more terms. The ratio of the dimensions of a two by four that is ten inches long is 2,4,10, a good concrete mix is sometimes quoted as 1,2,4 for the ratio of cement to sand to gravel. It is impossible to trace the origin of the concept of ratio because the ideas from which it developed would have been familiar to preliterate cultures. For example, the idea of one village being twice as large as another is so basic that it would have been understood in prehistoric society, however, it is possible to trace the origin of the word ratio to the Ancient Greek λόγος. Early translators rendered this into Latin as ratio, a more modern interpretation of Euclids meaning is more akin to computation or reckoning. Medieval writers used the word to indicate ratio and proportionalitas for the equality of ratios, Euclid collected the results appearing in the Elements from earlier sources. The Pythagoreans developed a theory of ratio and proportion as applied to numbers, the discovery of a theory of ratios that does not assume commensurability is probably due to Eudoxus of Cnidus. The exposition of the theory of proportions that appears in Book VII of The Elements reflects the earlier theory of ratios of commensurables, the existence of multiple theories seems unnecessarily complex to modern sensibility since ratios are, to a large extent, identified with quotients. This is a recent development however, as can be seen from the fact that modern geometry textbooks still use distinct terminology and notation for ratios
20.
Granite
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Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be white, pink, or gray in color. The word granite comes from the Latin granum, a grain, in reference to the structure of such a holocrystalline rock. By definition, granite is a rock with at least 20% quartz. The term granitic means granite-like and is applied to granite and a group of igneous rocks with similar textures and slight variations in composition. Occasionally some individual crystals are larger than the groundmass, in case the texture is known as porphyritic. A granitic rock with a texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks, petrographic examination is required for identification of specific types of granitoids. The extrusive igneous rock equivalent of granite is rhyolite, Granite is nearly always massive, hard and tough, and therefore it has gained widespread use throughout human history, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 •1019 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C, it is reduced in the presence of water. Granite has poor primary permeability, but strong secondary permeability, true granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite, when a granitoid contains less than 10% orthoclase, it is called tonalite, pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-mica granite, two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. A worldwide average of the composition of granite, by weight percent, based on 2485 analyses. Much of it was intruded during the Precambrian age, it is the most abundant basement rock that underlies the relatively thin veneer of the continents. Outcrops of granite tend to form tors and rounded massifs, granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite often occurs as small, less than 100 km² stock masses
21.
Peat
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Peat, also called turf, is an accumulation of partially decayed vegetation or organic matter that is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem is the most efficient carbon sink on the planet because peatland plants capture the CO2 which is released from the peat. Sphagnum moss is one of the most common components in peat, soils that contain mostly peat are known as histosols. Peat forms in wetland conditions, where flooding obstructs flows of oxygen from the atmosphere, Peatlands, particularly bogs, are the most important source of peat. That said, other less common types, including fens, pocosins. Landscapes covered in peat are home to specific kinds of plants including Sphagnum moss, ericaceous shrubs, because organic matter accumulates over thousands of years, peat deposits also provide records of past vegetation and climates stored in plant remains like pollen. This allows humans to reconstruct past environments and study changes in land use. Peat is harvested as an important source of fuel in certain parts of the world, by volume, there are about 4 trillion cubic metres of peat in the world, covering a total of around 2% of the global land area, containing about 8 billion terajoules of energy. Over time, the formation of peat is often the first step in the formation of other fossil fuels such as coal. This is also the commonly used in the peat industry. At 106 g CO2/MJ, the carbon dioxide emission intensity of peat is higher than that of coal and natural gas, lastly, peat fires have been responsible for large public health disasters including the 1997 Southeast Asian haze. Peat forms when plant material does not fully decay in acidic and anaerobic conditions and it is composed mainly of wetland vegetation, principally bog plants including mosses, sedges, and shrubs. As it accumulates, the peat holds water and this slowly creates wetter conditions that allow the area of wetland to expand. Peatland features can include ponds, ridges, and raised bogs, most modern peat bogs formed 12,000 years ago in high latitudes after the glaciers retreated at the end of the last ice age. Peat usually accumulates slowly at the rate of about a millimetre per year, using Carbon-dating, scientists found that Peat in peatlands started forming 360 million years ago based on it currently containing 550 Gt of carbon. Peat material is either fibric, hemic, or sapric, fibric peats are the least decomposed and consist of intact fiber. Hemic peats are partially decomposed and sapric are the most decomposed, Phragmites peat is one composed of reed grass, Phragmites australis, and other grasses. It is denser than other types of peat
22.
Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
23.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
24.
Hydrocarbon
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In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon, and thus are group 14 hydrides. Hydrocarbons from which one atom has been removed are functional groups. Aromatic hydrocarbons, alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons, the classifications for hydrocarbons, defined by IUPAC nomenclature of organic chemistry are as follows, Saturated hydrocarbons are the simplest of the hydrocarbon species. They are composed entirely of single bonds and are saturated with hydrogen, the formula for acyclic saturated hydrocarbons is CnH2n+2. The most general form of saturated hydrocarbons is CnH2n+2, where r is the number of rings and those with exactly one ring are the cycloalkanes. Saturated hydrocarbons are the basis of petroleum fuels and are found as linear or branched species. Substitution reaction is their characteristics property, hydrocarbons with the same molecular formula but different structural formulae are called structural isomers. As given in the example of 3-methylhexane and its higher homologues, chiral saturated hydrocarbons constitute the side chains of biomolecules such as chlorophyll and tocopherol. Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms and those with double bond are called alkenes. Those with one double bond have the formula CnH2n and those containing triple bonds are called alkyne. Those with one triple bond have the formula CnH2n−2, aromatic hydrocarbons, also known as arenes, are hydrocarbons that have at least one aromatic ring. Hydrocarbons can be gases, liquids, waxes or low melting solids or polymers, in terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons, and thus has 4 electrons available for covalent or dative bonding. Some hydrocarbons also are abundant in the solar system, lakes of liquid methane and ethane have been found on Titan, Saturns largest moon, confirmed by the Cassini-Huygens Mission. Hydrocarbons are also abundant in nebulae forming polycyclic aromatic hydrocarbon compounds, hydrocarbons are a primary energy source for current civilizations. The predominant use of hydrocarbons is as a fuel source. In their solid form, hydrocarbons take the form of asphalt, mixtures of volatile hydrocarbons are now used in preference to the chlorofluorocarbons as a propellant for aerosol sprays, due to chlorofluorocarbons impact on the ozone layer. Methane and ethane are gaseous at ambient temperatures and cannot be liquefied by pressure alone. Propane is however easily liquefied, and exists in propane bottles mostly as a liquid, butane is so easily liquefied that it provides a safe, volatile fuel for small pocket lighters
25.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
26.
Petrology
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Petrology is the branch of geology that studies the origin, composition, distribution and structure of rocks. In the petroleum industry, lithology, or more specifically mud logging, is the representation of geological formations being drilled through. As the cuttings are circulated out of the borehole they are sampled, examined and tested chemically when needed, Petrology utilizes the fields of mineralogy, petrography, optical mineralogy, and chemical analysis to describe the composition and texture of rocks. Igneous rocks include volcanic and plutonic rocks, sedimentary petrology focuses on the composition and texture of sedimentary rocks. Experiments are particularly useful for investigating rocks of the lower crust and they are also one of the prime sources of information about completely inaccessible rocks such as those in the Earths lower mantle and in the mantles of the other terrestrial planets and the Moon. The work of experimental petrologists has laid a foundation on which modern understanding of igneous, important publications in petrology Ore Soil Best, Myron G. Igneous and Metamorphic Petrology. ISBN 1-4051-0588-7 Blatt, Harvey, Tracy, Robert J. Owens, Brent, Petrology, igneous, sedimentary, ISBN 978-0-7167-3743-8 Dietrich, Richard Vincent, Skinner, Brian J. Gems, Granites, and Gravels, knowing and using rocks and minerals. ISBN 978-0-521-10722-8 Fei, Yingwei, Bertka, Constance M. Mysen, mantle Petrology, field observations and high-pressure experimentation. ISBN 0-941809-05-6 Philpotts, Anthony, Ague, Jay, Principles of Igneous and Metamorphic Petrology
27.
Hydraulic conductivity
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Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soils and rocks, that describes the ease with which a fluid can move through pore spaces or fractures. It depends on the permeability of the material, the degree of saturation. Saturated hydraulic conductivity, Ksat, describes water movement through saturated media, by definition, hydraulic conductivity is the ratio of velocity to hydraulic gradient indicating permeability of porous media.0 and 1.5, with an average value of 1.0. A. F. Salarashayeri & M. Siosemarde give C as usually taken between 1.0 and 1.5, with D in mm and K in cm/s. There are relatively simple and inexpensive laboratory tests that may be run to determine the conductivity of a soil, constant-head method. The constant-head method is used on granular soil. This procedure allows water to move through the soil under a steady state head condition while the quantity of flowing through the soil specimen is measured over a period of time. The water is allowed to flow through the soil without adding any water. The advantage to the method is that it can be used for both fine-grained and coarse-grained soils. When the water table is shallow, the method, a slug test. The method was developed by Hooghoudt in The Netherlands and introduced in the US by Van Bavel en Kirkham, the picture shows a large variation of K -values measured with the augerhole method in an area of 100 ha. The ratio between the highest and lowest values is 25, the cumulative frequency distribution is lognormal and was made with the CumFreq program. The transmissivity is a measure of how water can be transmitted horizontally. Transmissivity should not be confused with the similar word transmittance used in optics, an aquifer may consist of n soil layers. Expressing K i in m/day and d i in m, the transmissivity T i is found in units m2/day. The total transmissivity T t of the aquifer is, T t = ∑ T i where ∑ signifies the summation over all layers i =1,2,3, ⋯, n, the transmissivity of an aquifer can be determined from pumping tests. Influence of the water table When a soil layer is above the table, it is not saturated. When the soil layer is entirely below the table, its saturated thickness corresponds to the thickness of the soil layer itself
28.
Sand
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Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt, Sand can also refer to a textural class of soil or soil type, i. e. a soil containing more than 85% sand-sized particles by mass. The second most common type of sand is calcium carbonate, for example aragonite, for example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non renewable resource over human timescales, and sand suitable for making concrete is in high demand, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this size is termed a sand grain. Sand grains are between gravel and silt, a 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers. ISO14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size, very fine sand, fine sand, medium sand, coarse sand, and very coarse sand. These sizes are based on the Krumbein phi scale, where size in Φ = -log2D, on this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers. The composition of sand is highly variable, depending on the local rock sources. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite or gypsum, Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are typically green in color, as are sands derived from basaltic with a high olivine content, many sands, especially those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, the study of individual grains can reveal much historical information as to the origin and kind of transport of the grain. Quartz sand that is weathered from granite or gneiss quartz crystals will be angular. It is called grus in geology or sharp sand in the trade where it is preferred for concrete. Sand that is transported long distances by water or wind will be rounded, people who collect sand as a hobby are known as arenophiles
29.
Clay minerals
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Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minerals form in the presence of water and have been important to life and they are important constituents of soils, and have been useful to humans since ancient times in agriculture and manufacturing. Clays form flat hexagonal sheets similar to the micas, Clay minerals are common weathering products and low-temperature hydrothermal alteration products. Clay minerals are common in soils, in fine-grained sedimentary rocks such as shale, mudstone. Clay minerals are usually ultrafine-grained and so may require special techniques for their identification. These methods can be augmented by polarized light microscopy, a traditional technique establishing fundamental occurrences or petrologic relationships. Given the requirement of water, clay minerals are rare in the Solar System, though they occur extensively on Earth where water has interacted with other minerals. Clay minerals have been detected at several locations on Mars including Echus Chasma and Mawrth Vallis and the Memnonia quadrangle, spectrography has confirmed their presence on asteroids including the dwarf planet Ceres and Tempel 1 as well as Jupiters moon Europa. A1,1 clay would consist of one sheet and one octahedral sheet. A2,1 clay consists of an octahedral sheet sandwiched between two sheets, and examples are talc, vermiculite and montmorillonite. Smectite group which includes dioctahedral smectites such as montmorillonite, nontronite and beidellite, in 2013, analytical tests by the Curiosity rover found results consistent with the presence of smectite clay minerals on the planet Mars. Illite group which includes the clay-micas, illite is the only common mineral. Chlorite group includes a variety of similar minerals with considerable chemical variation. Other 2,1 clay types exist such as sepiolite or attapulgite, mixed layer clay variations exist for most of the above groups. Ordering is described as random or regular ordering, and is described by the term reichweite. Literature articles will refer to a R1 ordered illite-smectite, for example and this type would be ordered in an ISISIS fashion. R0 on the other hand describes random ordering, and other advanced ordering types are also found, mixed layer clay minerals which are perfect R1 types often get their own names. R1 ordered chlorite-smectite is known as corrensite, R1 illite-smectite is rectorite, knowledge of the nature of clay became better understood in the 1930s with advancements in x-ray diffraction technology necessary to analyze the molecular nature of clay particles
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Alluvium
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Alluvium is loose, unconsolidated soil or sediments, which has been eroded, reshaped by water in some form, and redeposited in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand, when this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it is called an alluvial deposit. The term alluvium is not typically used in situations where the formation of the sediment can clearly be attributed to another process that is well described. This includes, lake sediments, river sediments, or glacially-derived sediments, sediments that are formed or deposited in a perennial stream or river are typically not referred to as alluvial. Most alluvium is very young, and is often referred to as cover because these sediments obscure the underlying bedrock. Most sedimentary material that fills a basin that is not lithified is typically lumped together as alluvial, alluvium of Pliocene age occurs, for example, in parts of Idaho. Alluvium of late Miocene age occurs, for example, in the valley of the San Joaquin River, alluvium can contain valuable ores such as gold and platinum and a wide variety of gemstones. Such a concentration of ores is termed a placer deposit
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Sandstone
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Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
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Shale
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Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable, shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. Mudstones, on the hand, are similar in composition. Before the mid 19th century, the slate, shale. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. Non-fissile rocks of similar composition but made of smaller than 0.06 mm are described as mudstones or claystone. Rocks with similar sizes but with less clay and therefore grittier are siltstones. Shale is the most common sedimentary rock, shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock, black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal, red, brown and green colors are indicative of ferric oxide, iron hydroxide, or micaceous minerals. Clays are the constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite, clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and these released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor minerals found in shales and other mudrocks. Shales and mudrocks contain roughly 95 percent of the matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale, black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron and sulfur. Pyrite and amorphous iron sulfide along with carbon produce the black coloration, the process in the rock cycle which forms shale is called compaction. The fine particles that compose shale can remain suspended in long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are found in lakes and lagoonal deposits, in river deltas, on floodplains
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Limestone
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Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
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Diagenesis
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It does not include changes from weathering. It is any chemical, physical, or biological change undergone by a sediment after its initial deposition and this process excludes surface alteration and metamorphism. These changes happen at low temperatures and pressures and result in changes to the rocks original mineralogy. There is no boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures than the former. Hydrothermal solutions, meteoric groundwater, porosity, permeability, solubility, after deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis, porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization. The study of diagenesis in rocks is used to understand the history they have undergone. From a commercial standpoint, such aid in assessing the likelihood of finding various economically viable mineral. The process of diagenesis is also important in the decomposition of bone tissue, the term diagenesis, literally meaning across generation, is extensively used in geology. However, this term has filtered into the field of anthropology, archaeology and paleontology to describe the changes, the composite nature of bone, comprising one-third organic and two thirds mineral renders its diagenesis more complex. Three general pathways of the diagenesis of bone have been identified, chemical deterioration of the mineral phase. They are as follows, The dissolution of collagen depends on time, temperature, at high temperatures, the rate of collagen loss will be accelerated and extreme pH can cause collagen swelling and accelerated hydrolysis. The hydrolytic activity plays a key role in the phase transformations that exposes the collagen to accelerated chemical-. Once an individual has been interred, microbial attack, the most common mechanism of bone deterioration, during this phase, most bone collagen is lost and porosity is increased. The dissolution of the mineral phase caused by low pH permits access to the collagen by extracellular microbial enzymes thus microbial attack, when animal or plant matter is buried during sedimentation, the constituent organic molecules break down due to the increase in temperature and pressure. This transformation occurs in the first few hundred meters of burial and it is generally accepted that hydrocarbons are formed by the thermal alteration of these kerogens. In this way, given certain conditions kerogens will break down to form hydrocarbons through a process known as cracking. These models have been studied and applied in real geological applications
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Gulf Coast of the United States
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The Gulf Coast of the United States is the coastline along which the Southern United States meets the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Texas, Louisiana, Mississippi, Alabama, and Florida, the economy of the Gulf Coast area is dominated by industries related to energy, petrochemicals, fishing, aerospace, agriculture, and tourism. The Gulf Coast is made of many inlets, bays, the coast is also intersected by numerous rivers, the largest of which is the Mississippi River. Much of the land along the Gulf Coast is, or was and these landforms protect numerous bays and inlets providing as a barrier to oncoming waves. The central part of the Gulf Coast, from eastern Texas through Louisiana, the eastern part of the Gulf Coast, predominantly Florida, is dotted with many bays and inlets. The Gulf Coast climate is humid subtropical for the most part, although the tip of Florida. Much of the year is warm to hot along the Gulf Coast, while the 3 winters months bring periods of cool, the area is vulnerable to hurricanes as well as floods and severe thunderstorms. Tornadoes are infrequent at the coast but do occur, however the frequency at which they occur in inland portions of Gulf Coast states is much greater. Earthquakes are extremely rare to the area, but a surprising 6.0 earthquake in the Gulf of Mexico on September 10,2006, the Gulf Coast is a major center of economic activity. The marshlands along the Louisiana and Texas coasts provide breeding grounds, the Port of South Louisiana and the Port of Houston are two of the ten busiest ports in the world by cargo volume. As of 2004, seven of the top ten busiest ports in the U. S. are on the Gulf Coast. The discovery of oil and gas deposits along the coast and offshore, the coast contains nearly 4,000 oil platforms. S. Before Europeans arrived in the region, the region was home to several kingdoms that had extensive trade networks with empires such as the Aztecs. Shark and alligator teeth and shells from the Gulf have been found as far north as Ohio, the first Europeans to settle the Gulf Coast were primarily the French and the Spanish. The Louisiana Purchase and the Texas Revolution made the Gulf Coast a part of the United States during the first half of the 19th century. As the U. S. population continued to expand its frontiers westward, the development of sugar and cotton production allowed the South to prosper. Two major events were turning points in the history of the Gulf Coast region. The first was the American Civil War, which caused damage to some economic sectors in the South
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Cambrian
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The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents
