1.
1964 Niigata earthquake
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The 1964 Niigata earthquake struck at 13,01 local time on 16 June with a magnitude of 7.5 or 7.6. The epicenter was on the shelf off the northwest coast of Honshu, Japan in Niigata Prefecture. The earthquake caused liquefaction over large parts of the city, the northwestern side of Honshu lies on the southeastern margin of the Sea of Japan, an area of oceanic crust created by back-arc spreading from the late Oligocene to middle Miocene. The extensional tectonics associated with the spreading formed a series of N-S trending extensional faults, currently the area is being deformed by contractional tectonics, causing inversion of these earlier basins, forming anticlinal structures. The earthquake is thought to have occurred due to movement on one of these reactivated faults. There were 3,534 houses destroyed and a further 11,000 were damaged and this level of damage is explained by the influence of poor sub-soil conditions. Most of the part of the city of Niigata is built on recent deltaic deposits from the Shinano and Agano rivers. Shaking during the earthquake caused liquefaction with instantaneous compaction and formation of many sand volcanoes, maps of areas of subsidence and sand volcanoes were found to match closely with old maps of the position of former river channels. Subsidence of up to 140 cm was measured over wide areas associated with the liquefaction, in one area of apartment buildings built on reclaimed land by the Shinona River, most of the blocks became inclined, one of them being completely overturned. This was despite relatively low levels of ground acceleration recorded by strong motion accelerographs placed in one of these buildings, Niigata City, which had just recovered from the Great Niigata Fire of 1955, sustained considerable damage from fire and liquefaction that resulted from the earthquake. Aside from the destroyed by liquefaction on the left bank of the Shinano River there was also extensive damage on the right bank. The runway of the Niigata Airport was near the hypocenter and was flooded due to liquefaction and the tsunami, most devastatingly, the pipes of a gasoline tank owned by Showa Shell Sekiyu, located between the airport and the harbor, were also damaged by the shaking. Gasoline from the tank was brought to the sea surface by the tsunami and underground water released by the liquefaction, the fire spread to nearby tanks and induced explosions that fed the fire, allowing it to continue for 12 days. The fire spread to residential areas leaving 1407 people displaced. This fire is said to be the worst industrial complex fire in the countrys history, at the time the cause of the fire was said to be caused by the liquefaction, but later research into large earthquakes revealed that long period ground motion also played a role. At the time of the fire, the new specially-designed fire truck for fighting chemical fires had not yet been deployed to Niigata City, a request was sent to the Fire and Disaster Management Agency and troops were dispatched from the Tokyo division. There was a danger of the fire spreading to an oxygen tank. The collapse of the Showa bridge in Niigata has been analysed in detail, from eyewitness reports it appears that failure began 70 seconds after the start of the earthquake, suggesting that ground motion was not responsible
2.
2011 Christchurch earthquake
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An earthquake occurred in Christchurch on 22 February 2011 at 12,51 p. m. local time and registered 6.3 on the Richter scale. The earthquake caused damage across Christchurch, killing 185 people in the nations fifth-deadliest natural disaster. Significant liquefaction affected the eastern suburbs, producing around 400,000 tonnes of silt, the earthquake was felt across the South Island and parts of the lower and central North Island. Subsequent population loss saw the Christchurch main urban area fall behind the Wellington equivalent to decrease from second to third most populous area in New Zealand,185 people from more than 20 countries died in the earthquake. Over half of the deaths occurred in the six-storey Canterbury Television Building, an additional 28 people were killed in various places across the city centre, and twelve were killed in suburban Christchurch. Due to the injuries sustained some bodies remained unidentified, between 6,600 and 6,800 people were treated for minor injuries, and Christchurch Hospital alone treated 220 major trauma cases connected to the quake. Rescue efforts continued for over a week, then shifted into recovery mode, the last survivor was pulled from the rubble the day after the quake. The nationalities of the deceased are as follows, road and bridge damage occurred and hampered rescue efforts. Soil liquefaction and surface flooding also occurred, road surfaces were forced up by liquefaction, and water and sand were spewing out of cracks. A number of cars were crushed by falling debris, in the central city, two buses were crushed by falling buildings. Because the earthquake hit during the hour, some people on the footpaths were buried by collapsed buildings. Damage occurred to older buildings, particularly those with unreinforced masonry. Of the 3,000 buildings inspected within the four avenues of the city by 3 March 2011. Many heritage buildings were given red stickers after inspections, as of February 2015, there had been 1240 demolitions within the four avenues since the September 2010 earthquakes. The six-storey Canterbury Television building collapsed in the earthquake, leaving only its lift shaft standing,115 people died in the building, which housed a TV station, a medical clinic and an English language school. On 23 February police decided that the damage was not survivable, fire-fighting and recovery operations resumed that night, later joined by a Japanese search and rescue squad. Twelve Japanese students from the Toyama College of Foreign Languages died in the building collapse, a government report later found that the buildings construction was faulty and should not have been approved. The four-storey Pyne Gould Guinness House on Cambridge Terrace, headquarters of Pyne Gould Corporation, collapsed, on Wednesday morning,22 hours after the quake, a survivor was pulled from the rubble
3.
Soil
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Soil is a mixture of minerals, organic matter, gases, liquids, and countless organisms that together support life on Earth. Soil is called the Skin of the Earth and interfaces with the lithosphere, the hydrosphere, the atmosphere, the term pedolith, used commonly to refer to the soil, literally translates ground stone. Soil consists of a phase of minerals and organic matter, as well as a porous phase that holds gases. Accordingly, soils are often treated as a system of solids, liquids. Soil is a product of the influence of climate, relief, organisms, Soil continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness soil has been considered as an ecosystem by soil ecologists. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the particle density is much higher. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, Soil science has two basic branches of study, edaphology and pedology. Edaphology is concerned with the influence of soils on living things, pedology is focused on the formation, description, and classification of soils in their natural environment. In engineering terms, soil is referred to as regolith, or loose material that lies above the solid geology. Soil is commonly referred to as earth or dirt, technically, as soil resources serve as a basis for food security, the international community advocates its sustainable and responsible use through different types of soil governance. Soil is a component of the Earths ecosystem. The worlds ecosystems are impacted in far-reaching ways by the carried out in the soil, from ozone depletion and global warming, to rainforest destruction. Following the atmosphere, the soil is the next largest carbon reservoir on Earth, as the planet warms, soils will add carbon dioxide to the atmosphere due to its increased biological activity at higher temperatures. Thus, soil carbon losses likely have a positive feedback response to global warming. Since soil has a range of available niches and habitats. A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial, Soil has a mean prokaryotic density of roughly 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater. Since plant roots need oxygen, ventilation is an important characteristic of soil and this ventilation can be accomplished via networks of interconnected soil pores, which also absorb and hold rainwater making it readily available for plant uptake
4.
Shear strength (soil)
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Shear strength is a term used in soil mechanics to describe the magnitude of the shear stress that a soil can sustain. The shear resistance of soil is a result of friction and interlocking of particles, due to interlocking, particulate material may expand or contract in volume as it is subject to shear strains. If soil expands its volume, the density of particles will decrease and the strength will decrease, in this case, the stress-strain relationship levels off when the material stops expanding or contracting, and when interparticle bonds are broken. The theoretical state at which the stress and density remain constant while the shear strain increases may be called the critical state, steady state. The average normal intergranular contact force per unit area is called the effective stress, if water is not allowed to flow in or out of the soil, the stress path is called an undrained stress path. On the other hand, if the fluids are allowed to drain out of the pores, then the pore pressures will remain constant. The soil is free to dilate or contract during shear if the soil is drained, in reality, soil is partially drained, somewhere between the perfectly undrained and drained idealized conditions. The shear strength of soil depends on the stress, the drainage conditions, the density of the particles, the rate of strain. For undrained, constant volume shearing, the Tresca theory may be used to predict the strength, but for drained conditions. Two important theories of soil shear are the state theory. There are key differences between the critical condition and the steady state condition and the resulting theory corresponding to each of these conditions. State, Defined by the void ratio, effective normal stress. Features such as layers, joints, fissures, slickensides, voids, pockets, cementation, loading conditions, Effective stress path, i. e. drained, and undrained, and type of loading, i. e. magnitude, rate, and time history. This term describes a type of strength in soil mechanics as distinct from drained strength. Conceptually, there is no such thing as the strength of a soil. An example of this is rapid loading of sands during an earthquake, or the failure of a clay slope during heavy rain, as an implication of undrained condition, no elastic volumetric strains occur, and thus Poissons ratio is assumed to remain 0.5 throughout shearing. The Tresca soil model also assumes no plastic volumetric strains occur and this is of significance in more advanced analyses such as in finite element analysis.5. The constant c/p relationship can also be derived from theory for both critical-state and steady-state soil mechanics and this fundamental, normalization property of the stress-strain curves is found in many clays, and was refined into the empirical SHANSEP method
5.
Stiffness
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Stiffness is the rigidity of an object — the extent to which it resists deformation in response to an applied force. The complementary concept is flexibility or pliability, the more flexible an object is, the stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. In Imperial units, stiffness is typically measured in pounds per inch, generally speaking, deflections of an infinitesimal element in an elastic body can occur along multiple DOF. For example, a point on a beam can undergo both a vertical displacement and a rotation relative to its undeformed axis. When there are M degrees of freedom a M x M matrix must be used to describe the stiffness at the point, in industry, the term influence coefficient is sometimes used to refer to the coupling stiffness. For a body with multiple DOF, in order to calculate a particular direct-related stiffness, under such a condition, the above equation can be used to obtain the direct-related stiffness for the degree of freedom which is unconstrained. The ratios between the forces and the produced deflection are the coupling stiffnesses. A description including all possible stretch and shear parameters is given by the elasticity tensor, the inverse of stiffness is flexibility or compliance, typically measured in units of metres per newton. In rheology it may be defined as the ratio of strain to stress, in the SAE system, rotational stiffness is typically measured in inch-pounds per degree. For example, for an element in tension or compression, the stiffness is k = A E L where A is the cross-sectional area, E is the elastic modulus. For the special case of unconstrained uniaxial tension or compression, Youngs modulus can be thought of as a measure of the stiffness of a structure. The stiffness of a structure is of importance in many engineering applications. A high modulus of elasticity is sought when deflection is undesirable, while a low modulus of elasticity is required when flexibility is needed, in biology, the stiffness of the extracellular matrix is important for guiding the migration of cells in a phenomenon called durotaxis. Another application of stiffness finds itself in skin biology, the skin maintains its structure due to its intrinsic tension, contributed to by collagen, an extracellular protein which accounts for approximately 75% of its dry weight. The pliability of skin is a parameter of interest that represents its firmness and extensibility, encompassing characteristics such as elasticity, stiffness and these factors are of functional significance to patients. This is of significance to patients with injuries to the skin, whereby the pliability can be reduced due to the formation. This can be evaluated both subjectively, or objectively using a device such as the Cutometer, the Cutometer applies a vacuum to the skin and measures the extent to which it can be vertically distended
6.
Shear stress
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A shear stress, often denoted τ, is defined as the component of stress coplanar with a material cross section. Shear stress arises from the vector component parallel to the cross section. Normal stress, on the hand, arises from the force vector component perpendicular to the material cross section on which it acts. The formula to calculate average shear stress is force per unit area, τ = F A, where, τ = the shear stress, F = the force applied, A = the cross-sectional area of material with area parallel to the applied force vector. Pure shear stress is related to shear strain, denoted γ, by the following equation, τ = γ G where G is the shear modulus of the isotropic material. Here E is Youngs modulus and ν is Poissons ratio, beam shear is defined as the internal shear stress of a beam caused by the shear force applied to the beam. The beam shear formula is known as Zhuravskii shear stress formula after Dmitrii Ivanovich Zhuravskii who derived it in 1855. Shear stresses within a structure may be calculated by idealizing the cross-section of the structure into a set of stringers. Dividing the shear flow by the thickness of a portion of the semi-monocoque structure yields the shear stress. Any real fluids moving along solid boundary will incur a shear stress on that boundary, the no-slip condition dictates that the speed of the fluid at the boundary is zero, but at some height from the boundary the flow speed must equal that of the fluid. The region between two points is aptly named the boundary layer. For all Newtonian fluids in laminar flow the shear stress is proportional to the rate in the fluid where the viscosity is the constant of proportionality. However, for non-Newtonian fluids, this is no longer the case as for these fluids the viscosity is not constant, the shear stress is imparted onto the boundary as a result of this loss of velocity. Specifically, the shear stress is defined as, τ w ≡ τ = μ ∂ u ∂ y | y =0. For an isotropic Newtonian flow it is a scalar, while for anisotropic Newtonian flows it can be a second-order tensor too. On the other hand, given a shear stress as function of the flow velocity, the constant one finds in this case is the dynamic viscosity of the flow. On the other hand, a flow in which the viscosity were and this nonnewtonian flow is isotropic, so the viscosity is simply a scalar, μ =1 u. This relationship can be exploited to measure the shear stress
7.
Earthquake
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An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earths lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to people around. The seismicity or seismic activity of an area refers to the frequency, type, Earthquakes are measured using measurements from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe and these two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly imperceptible or weak and magnitude 7 and over potentially cause damage over larger areas. The largest earthquakes in historic times have been of magnitude slightly over 9, intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the damage to structures it causes. At the Earths surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground, when the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity, in its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of faults, but also by other events such as volcanic activity, landslides, mine blasts. An earthquakes point of rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter, tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of stick-slip behavior, once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the portion of the fault. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface and this process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of a total energy is radiated as seismic energy. Most of the energy is used to power the earthquake fracture growth or is converted into heat generated by friction
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.
Allen Hazen
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Allen Hazen was an expert in hydraulics, flood control, water purification and sewage treatment. His career extended from 1888 to 1930 and he is, perhaps, Hazen published some of the seminal works on sedimentation and filtration. He was President of the New England Water Works Association and Vice President of the American Society of Civil Engineers, Allen Hazen was born in 1869 on his family farm located near the Connecticut River close to the small town of Norwich, Vermont. He attended the New Hampshire College of Agriculture and Mechanical Arts, during a year spent at MIT, Hazen studied chemistry and came into contact with Professor William T. Sedgwick, Dr. Thomas M. Drown and fellow students George W. Fuller and George C. As a direct result of his association with Dr. Thomas M. Drown, Hazen was offered his first job at the Lawrence Experiment Station in Lawrence, LES was likely the first institute in the world devoted solely to investigations of water purification and sewage treatment. From 1888 to 1893, Hazen headed the team at this innovative research institute into water purification. Hazen is most widely known for developing in 1902 with Gardner S. Williams the Hazen-Williams equation which described the flow of water in pipelines, in 1905, the two engineers published an influential book, which contained solutions to the Hazen-Williams equation for pipes of widely varying diameters. The equation uses an empirically derived constant for the “roughness” of the walls which became known as the Hazen-Williams coefficient. In 1908, Hazen was appointed by President Theodore Roosevelt to a panel of engineers to inspect the construction progress on the Panama Canal with President-Elect William H. Taft. Hazen specifically reported on the soundness of the Gatun Dam, which he said was constructed of the proper materials, late in his career, Hazen concentrated on ways to statistically describe the recurrence interval of flood flows in rivers. His book on the subject was published the year he died, the Allen Hazen Water Tower was built in 1930-1 in Des Moines, Iowa. Hazen designed the tower shortly before he died, in his honor, the City of Des Moines named the tower after him. Hazen’s early work at the Lawrence Experiment Station established some of the parameters for the design of slow sand filters. One of his greatest contributions to technology was the derivation of two terms for describing the size distribution of filter media, effective size and uniformity coefficient. These two parameters are used today to specify the size of filter materials for water purification applications and his first book, The Filtration of Public Water Supplies, which was published in 1895, is still considered a classic. His first assignment as a practitioner in 1897 was the design of the filtration plant at Albany. The plant was the first continuously operated slow sand plant in the U. S. One of his assignments was as consultant to Pittsburgh, Pennsylvania
10.
Calaveras Dam
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Calaveras Reservoir is located primarily in Santa Clara County, California, with a small portion and its dam in Alameda County, California. The reservoir has a capacity of 100,000 acre·ft, Calaveras Reservoir is fed mainly by Arroyo Hondo and Calaveras Creek. Lying in the Calaveras Valley, the region is an active area with the Calaveras Fault parallel to, and to the west of. Because of the hazard, a replacement dam is scheduled to open in 2018, roads adjacent to the reservoir include Calaveras Road and Marsh Road. The latter drew significant attention from a murder there in the early 1980s, the Calaveras Valley is rich and diverse in wildlife. Since at least 2008 there has also been a regular nesting pair of bald eagles, in the 19th century, the Calaveras Valley which the reservoir now fills was primarily an agricultural region known for its production of hay, strawberries, and tomatoes. The first dam on the site, built in 1913 by the Spring Valley Water Company, rapidly changed the sensitive hydrology and it suffered a partial collapse of the upstream slope in 1918 due to engineering flaws. Its replacement, the current Calaveras Dam, was at its completion in 1925 the largest earth-fill dam in the world and it is 245 feet high, with a length of 1200 feet at its crest. The city and county of San Francisco owns and operates the dam, the reservoir is reported to contain a very large population of largemouth bass, rainbow trout and other species. Today, the San Francisco Public Utilities Commission owns 36,000 acres in the Alameda Creek Watershed, some lands in the watershed are leased to livestock companies for cattle ranching to control vegetation and prevent fires. Most of the land is closed to the public because of concerns over drinking water safety and quality, the San Francisco Public Utilities Commission is constructing a new dam of equal height downstream of the existing dam as part of the $4.3 billion Water System Improvement Program. The 7 year-long environmental impact report was certified by the San Francisco City Planning Commission on January 27,2011. Later that day, the $434 Million Calaveras Dam Replacement Project was given the light by the SFPUC. Excavation began in 2011 with construction on the actual dam expected to begin in 2016, the entire replacement should be complete in 2018. The replacement effort will include measures to aid in the restoration of native fish populations. Steelhead trout have not had access to spawning streams above Calaveras Dam since 1925, in the late 1980s and early 1990s, a drought affected California, and water levels in reservoirs throughout the state became extraordinarily low. By January 1991, the water at the reservoir was down 100 feet, two skeletons were found at the site on January 5,1991. Dental records and the serial number were used to positively identify the remains as Clifford Gillman and his single-engine Ercoupe
11.
Embankment dam
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An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and it has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes such a dam impervious to surface or seepage erosion, such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance, embankment dams come in two types, the earth-filled dam made of compacted earth, and the rock-filled dam. A cross-section of an embankment dam shows a shape like a bank, most have a central section or core composed of an impermeable material to stop water from seeping through the dam. The core can be of clay, concrete, or asphalt concrete and this dam type is a good choice for sites with wide valleys. They can be built on rock or softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock, additionally, the rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam. The building of a dam and the filling of the reservoir behind it places a new weight on the floor, the stress of the water increases linearly with its depth. Thus the stress level of the dam must be calculated in advance of building to ensure that its break level threshold is not exceeded, overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure. The erosion of the material by overtopping runoff will remove masses of material whose weight holds the dam in place. Even a small sustained overtopping flow can remove thousands of tons of soil from the mass of the dam within hours. As the mass of the dam erodes, the force exerted by the reservoir begins to move the entire structure, therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be such that it can contain a five hundred year flood. Recently a number of embankment dam overtopping protection systems have been developed
12.
Quicksand
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Quicksand is a colloid hydrogel consisting of fine granular material, and water. Quicksand forms in saturated loose sand when the sand is suddenly agitated, when water in the sand cannot escape, it creates a liquefied soil that loses strength and cannot support weight. Quicksand can form in standing water or in upwards flowing water, in the case of upwards flowing water, seepage forces oppose the force of gravity and suspend the soil particles. The saturated sediment may appear quite solid until a change in pressure or shock initiates liquefaction. This causes the sand to form a suspension and lose strength, the cushioning of water gives quicksand, and other liquefied sediments, a spongy, fluidlike texture. Objects in liquefied sand sink to the level at which the weight of the object is equal to the weight of the displaced soil/water mix, liquefaction is a special case of quicksand. In this case, sudden earthquake forces immediately increase the pressure of shallow groundwater. The saturated liquefied soil loses strength, causing buildings or other objects on surface to sink or fall. Quicksand is a shear thinning non-Newtonian fluid, when undisturbed, it appears to be solid. Someone stepping on it will start to sink, to move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are large, to remove a foot from quicksand at a speed of 0.01 m/s would require the same amount of force as that needed to lift a medium-sized car. Contrary to popular belief, quicksand itself is harmless, a human or animal is unlikely to sink entirely into quicksand, Quicksand has a density of about 2 grams per milliliter, whereas the density of the human body is only about 1 gram per milliliter. At that level of density, sinking in quicksand is impossible, descending about up to the waist is possible, but not any further. Even objects with a higher density than quicksand will float on it—until they move, aluminum, for example, has a density of about 2.7 grams per milliliter, but a piece of aluminum will float on top of quicksand until motion causes the sand to liquefy. Continued or panicked movement, however, may cause a person in quicksand to sink deeper, leading to belief that quicksand is dangerous. Since it increasingly impairs movement, this, then, can lead to a situation where other such as weather exposure, dehydration, hypothermia. Quicksand may be escaped by slow movement of the legs in order to increase viscosity of the fluid, Quicksand may be found on riverbanks, near lakes, in marshes, or near the coast. People falling into quicksand or a substance is a trope of adventure fiction
13.
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
14.
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
15.
Compressibility
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In thermodynamics and fluid mechanics, compressibility is a measure of the relative volume change of a fluid or solid as a response to a pressure change. β = −1 V ∂ V ∂ p where V is volume, the specification above is incomplete, because for any object or system the magnitude of the compressibility depends strongly on whether the process is adiabatic or isothermal. Accordingly, isothermal compressibility is defined, β T = −1 V T where the subscript T indicates that the differential is to be taken at constant temperature. Isentropic compressibility is defined, β S = −1 V S where S is entropy, for a solid, the distinction between the two is usually negligible. The minus sign makes the compressibility positive in the case that an increase in pressure induces a reduction in volume, the speed of sound is defined in classical mechanics as, c 2 = S where ρ is the density of the material. It follows, by replacing partial derivatives, that the compressibility can be expressed as, β S =1 ρ c 2 The inverse of the compressibility is called the bulk modulus. That page also contains some examples for different materials, the compressibility equation relates the isothermal compressibility to the structure of the liquid. The term compressibility is also used in thermodynamics to describe the deviance in the properties of a real gas from those expected from an ideal gas. The compressibility factor is defined as Z = p V _ R T where p is the pressure of the gas, T is its temperature, and V _ is its molar volume. The deviation from ideal gas behavior tends to become particularly significant near the critical point, in these cases, a generalized compressibility chart or an alternative equation of state better suited to the problem must be utilized to produce accurate results. This pressure dependent transition occurs for atmospheric oxygen in the 2500 K to 4000 K temperature range, in transition regions, where this pressure dependent dissociation is incomplete, both beta and the differential, constant pressure heat capacity greatly increase. For moderate pressures, above 10,000 K the gas further dissociates into free electrons and ions, Z for the resulting plasma can similarly be computed for a mole of initial air, producing values between 2 and 4 for partially or singly ionized gas. Each dissociation absorbs a great deal of energy in a reversible process, ions or free radicals transported to the object surface by diffusion may release this extra energy if the surface catalyzes the slower recombination process. The isothermal compressibility is related to the isentropic compressibility by the relation, more simply stated, β T β S = γ where, γ is the heat capacity ratio. The Earth sciences use compressibility to quantify the ability of a soil or rock to reduce in volume under applied pressure and this concept is important for specific storage, when estimating groundwater reserves in confined aquifers. Geologic materials are made up of two portions, solids and voids, the void space can be full of liquid or gas. Geologic materials reduces in volume only when the spaces are reduced. This can happen over a period of time, resulting in settlement and it is an important concept in geotechnical engineering in the design of certain structural foundations
16.
Force
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In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity, force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity and it is measured in the SI unit of newtons and represented by the symbol F. The original form of Newtons second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. In an extended body, each part usually applies forces on the adjacent parts, such internal mechanical stresses cause no accelation of that body as the forces balance one another. Pressure, the distribution of small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of materials, or flow in fluids. In part this was due to an understanding of the sometimes non-obvious force of friction. A fundamental error was the belief that a force is required to maintain motion, most of the previous misunderstandings about motion and force were eventually corrected by Galileo Galilei and Sir Isaac Newton. With his mathematical insight, Sir Isaac Newton formulated laws of motion that were not improved-on for nearly three hundred years, the Standard Model predicts that exchanged particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known, in order of decreasing strength, they are, strong, electromagnetic, weak, high-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction. Since antiquity the concept of force has been recognized as integral to the functioning of each of the simple machines. The mechanical advantage given by a machine allowed for less force to be used in exchange for that force acting over a greater distance for the same amount of work. Analysis of the characteristics of forces ultimately culminated in the work of Archimedes who was famous for formulating a treatment of buoyant forces inherent in fluids. Aristotle provided a discussion of the concept of a force as an integral part of Aristotelian cosmology. In Aristotles view, the sphere contained four elements that come to rest at different natural places therein. Aristotle believed that objects on Earth, those composed mostly of the elements earth and water, to be in their natural place on the ground. He distinguished between the tendency of objects to find their natural place, which led to natural motion, and unnatural or forced motion
17.
Water table
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The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water, the water table is the surface where the water pressure head is equal to the atmospheric pressure. It may be visualized as the surface of the materials that are saturated with groundwater in a given vicinity. The groundwater may be from precipitation or from groundwater flowing into the aquifer, in areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths water fills in more of the spaces in the soils. Below the water table, in the zone, layers of permeable rock that yield groundwater are called aquifers. In less permeable soils, such as tight bedrock formations and historic lakebed deposits, the water table should not be confused with the water level in a deeper well. The elevation of the water in this well is dependent upon the pressure in the deeper aquifer and is referred to as the potentiometric surface. The water table may vary due to changes such as precipitation and evapotranspiration. Springs, rivers, lakes and oases occur when the table reaches the surface. Springs commonly form on hillsides, where the Earths slanting surface may intersect with the water table, Groundwater entering rivers and lakes accounts for the base-flow water levels in water bodies. Within an aquifer, the table is rarely horizontal, but reflects the surface relief due to the capillary effect in soils, sediments. In the aquifer, groundwater flows from points of pressure to points of lower pressure. The slope of the table is known as the hydraulic gradient, which depends on the rate at which water is added to and removed from the aquifer. This occurs when there is a layer of rock or sediment or relatively impermeable layer above the main water table/aquifer. If a perched aquifers flow intersects the Earths dry surface, at a wall for example. On low-lying oceanic islands with porous soil, freshwater tends to collect in lenticular pools on top of the denser seawater intruding from the sides of the islands, such an islands freshwater lens, and thus the water table, rises and falls with the tides. In some regions, for example, Great Britain or California, winter precipitation is higher than summer precipitation
18.
Sea level
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Mean sea level is an average level of the surface of one or more of Earths oceans from which heights such as elevations may be measured. A common and relatively straightforward mean sea-level standard is the midpoint between a low and mean high tide at a particular location. Sea levels can be affected by factors and are known to have varied greatly over geological time scales. The careful measurement of variations in MSL can offer insights into ongoing climate change, the term above sea level generally refers to above mean sea level. Precise determination of a sea level is a difficult problem because of the many factors that affect sea level. Sea level varies quite a lot on several scales of time and this is because the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity and so forth. The easiest way this may be calculated is by selecting a location and calculating the mean sea level at that point, for example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point. One measures the values of MSL in respect to the land, hence a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates. In the UK, the Ordnance Datum is the sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the datum was MSL at the Victoria Dock, in Hong Kong, mPD is a surveying term meaning metres above Principal Datum and refers to height of 1. 230m below the average sea level. In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and it is used for a part of continental Europe and main part of Africa as official sea level. Elsewhere in Europe vertical elevation references are made to the Amsterdam Peil elevation, satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001, height above mean sea level is the elevation or altitude of an object, relative to the average sea level datum. It is also used in aviation, where some heights are recorded and reported with respect to sea level, and in the atmospheric sciences. An alternative is to base height measurements on an ellipsoid of the entire Earth, in aviation, the ellipsoid known as World Geodetic System 84 is increasingly used to define heights, however, differences up to 100 metres exist between this ellipsoid height and mean tidal height. The alternative is to use a vertical datum such as NAVD88. When referring to geographic features such as mountains on a topographic map, the elevation of a mountain denotes the highest point or summit and is typically illustrated as a small circle on a topographic map with the AMSL height shown in metres, feet or both. In the rare case that a location is below sea level, for one such case, see Amsterdam Airport Schiphol
19.
Pore water pressure
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Pore water pressure refers to the pressure of groundwater held within a soil or rock, in gaps between particles. Pore water pressures in below the level are measured in piezometers. The vertical pore water pressure distribution in aquifers can generally be assumed to be close to hydrostatic, in the unsaturated zone, the pore pressure is determined by capillarity and is also referred to as tension, suction, or matric pressure. Pore water pressures under unsaturated conditions are measured in with tensiometers, tensiometers operate by allowing the pore water to come into equilibrium with a reference pressure indicator through a permeable ceramic cup placed in contact with the soil. Pore water pressure is vital in calculating the stress state in the soil mechanics. Hydrostatic water pressure, resulting from the weight of material above the point measured, osmotic pressure, inhomogeneous aggregation of ion concentrations, which causes a force in water particles as they attract by the molecular laws of attraction. Adsorption pressure, attraction of surrounding soil particles to one another by adsorbed water films, the buoyancy effects of water have a large impact on certain soil properties, such as the effective stress present at any point in a soil medium. Consider an arbitrary point five meters below the ground surface, in dry soil, particles at this point experience a total overhead stress equal to the depth underground, multiplied by the specific weight of the soil.81 kN/m^3. This parameter is called the stress of the soil, basically equal to the difference in a soils total stress. The pore water pressure is essential in differentiating a soils total stress from its effective stress, a correct representation of stress in soil is necessary for accurate field calculations in a variety of engineering trades. The static pressure of groundwater at a specific depth, piezometers often employ electronic pressure transducers to provide data. The United States Bureau of Reclamation has a standard for monitoring water pressure in a mass with piezometers. It sites ASTM D4750, Standard Test Method for Determining Subsurface Liquid Levels in a Borehole or Monitoring Well, at any point above the water table, in the vadose zone, the effective stress is approximately equal to the total stress, as proven by Terzaghis principle. Realistically, the stress is greater than the total stress. This is primarily due to the tension of pore water in voids throughout the vadose zone causing a suction effect on surrounding particles. This capillary action is the movement of water through the vadose zone. The height of rise is inversely proportional to the diameter of void space in contact with water. Therefore, the smaller the space, the higher water will rise due to tension forces
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Contact mechanics
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Contact mechanics is the study of the deformation of solids that touch each other at one or more points. Central aspects in contact mechanics are the pressures and adhesion acting perpendicular to the bodies surfaces. This page focuses mainly on the direction, i. e. on frictionless contact mechanics. Frictional contact mechanics is discussed separately, current challenges faced in the field may include stress analysis of contact and coupling members and the influence of lubrication and material design on friction and wear. Applications of contact mechanics further extend into the micro- and nanotechnological realm, the original work in contact mechanics dates back to 1882 with the publication of the paper On the contact of elastic solids by Heinrich Hertz. Hertz was attempting to understand how the properties of multiple. Hertzian contact stress refers to the stresses that develop as two curved surfaces come in contact and deform slightly under the imposed loads. This amount of deformation is dependent on the modulus of elasticity of the material in contact and it gives the contact stress as a function of the normal contact force, the radii of curvature of both bodies and the modulus of elasticity of both bodies. Hertzian contact stress forms the foundation for the equations for load bearing capabilities and fatigue life in bearings, gears, classical contact mechanics is most notably associated with Heinrich Hertz. In 1882, Hertz solved the problem of two elastic bodies with curved surfaces. This still-relevant classical solution provides a foundation for modern problems in contact mechanics, for example, in mechanical engineering and tribology, Hertzian contact stress is a description of the stress within mating parts. The Hertzian contact stress refers to the stress close to the area of contact between two spheres of different radii. It was not until one hundred years later that Johnson, Kendall. This theory was rejected by Boris Derjaguin and co-workers who proposed a different theory of adhesion in the 1970s, the Derjaguin model came to be known as the DMT model, and the Johnson et al. model came to be known as the JKR model for adhesive elastic contact. This rejection proved to be instrumental in the development of the Tabor, further advancement in the field of contact mechanics in the mid-twentieth century may be attributed to names such as Bowden and Tabor. Bowden and Tabor were the first to emphasize the importance of surface roughness for bodies in contact, through investigation of the surface roughness, the true contact area between friction partners is found to be less than the apparent contact area. Such understanding also drastically changed the direction of undertakings in tribology, the works of Bowden and Tabor yielded several theories in contact mechanics of rough surfaces. The contributions of Archard must also be mentioned in discussion of pioneering works in this field, Archard concluded that, even for rough elastic surfaces, the contact area is approximately proportional to the normal force
21.
Engineer
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Engineers design materials, structures, and systems while considering the limitations imposed by practicality, regulation, safety, and cost. The word engineer is derived from the Latin words ingeniare and ingenium, the work of engineers forms the link between scientific discoveries and their subsequent applications to human and business needs and quality of life. His/her work is predominantly intellectual and varied and not of a mental or physical character. It requires the exercise of original thought and judgement and the ability to supervise the technical, he/she is thus placed in a position to make contributions to the development of engineering science or its applications. In due time he/she will be able to give authoritative technical advice, much of an engineers time is spent on researching, locating, applying, and transferring information. Indeed, research suggests engineers spend 56% of their time engaged in various information behaviours, Engineers must weigh different design choices on their merits and choose the solution that best matches the requirements. Their crucial and unique task is to identify, understand, Engineers apply techniques of engineering analysis in testing, production, or maintenance. Analytical engineers may supervise production in factories and elsewhere, determine the causes of a process failure and they also estimate the time and cost required to complete projects. Supervisory engineers are responsible for major components or entire projects, Engineering analysis involves the application of scientific analytic principles and processes to reveal the properties and state of the system, device or mechanism under study. Most engineers specialize in one or more engineering disciplines, numerous specialties are recognized by professional societies, and each of the major branches of engineering has numerous subdivisions. Civil engineering, for example, includes structural and transportation engineering and materials engineering include ceramic, metallurgical, mechanical engineering cuts across just about every discipline since its core essence is applied physics. Engineers also may specialize in one industry, such as vehicles, or in one type of technology. Several recent studies have investigated how engineers spend their time, that is, research suggests that there are several key themes present in engineers’ work, technical work, social work, computer-based work, information behaviours. Amongst other more detailed findings, a recent work sampling study found that engineers spend 62. 92% of their time engaged in work,40. 37% in social work. The time engineers spend engaged in activities is also reflected in the competencies required in engineering roles. There are many branches of engineering, each of which specializes in specific technologies, typically engineers will have deep knowledge in one area and basic knowledge in related areas. When developing a product, engineers work in interdisciplinary teams. For example, when building robots an engineering team will typically have at least three types of engineers, a mechanical engineer would design the body and actuators
22.
1964 Alaska earthquake
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The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5,36 P. M. AST on Good Friday, March 27, across south-central Alaska, ground fissures, collapsing structures, and tsunamis resulting from the earthquake caused about 139 deaths. Lasting four minutes and thirty-eight seconds, the magnitude 9.2 megathrust earthquake was the most powerful recorded in North American history, soil liquefaction, fissures, landslides, and other ground failures caused major structural damage in several communities and much damage to property. Anchorage sustained great destruction or damage to many inadequately earthquake engineered houses, buildings, two hundred miles southwest, some areas near Kodiak were permanently raised by 30 feet. Nearby, a 27-foot tsunami destroyed the village of Chenega, killing 23 of the 68 people who lived there, survivors out-ran the wave, climbing to high ground. Post-quake tsunamis severely affected Whittier, Seward, Kodiak, and other Alaskan communities, as well as people and property in British Columbia, Washington, Oregon, tsunamis also caused damage in Hawaii and Japan. Evidence of motion directly related to the earthquake was reported from Florida. Alaska Standard Time, a fault between the Pacific and North American plates ruptured near College Fjord in Prince William Sound, the epicenter of the earthquake was 12.4 mi north of Prince William Sound,78 miles east of Anchorage and 40 miles west of Valdez. The focus occurred at a depth of approximately 15.5 mi, ocean floor shifts created large tsunamis, which resulted in many of the deaths and much of the property damage. Large rockslides were also caused, resulting in property damage. Vertical displacement of up to 38 feet occurred, affecting an area of 100,000 miles² within Alaska, studies of ground motion have led to a peak ground acceleration estimate of 0. 14–0.18 g. The Alaska earthquake was a subduction zone earthquake, caused by an oceanic plate sinking under a continental plate, the fault responsible was the Aleutian Megathrust, a reverse fault caused by a compressional force. This caused much of the ground which is the result of ground shifted to the opposite elevation. Two types of tsunamis were produced by subduction zone earthquake. There was a tectonic tsunami produced in addition to about 20 smaller and these smaller tsunami were produced by submarine and subaerial landslides and were responsible for the majority of the tsunami damage. Tsunami waves were noted in over 20 countries, including, Peru, New Zealand, Papua New Guinea, Japan, the largest tsunami wave was recorded in Shoup Bay, Alaska, with a height of about 220 ft. The quake was a reported XI on the modified Mercalli Intensity scale indicating major structural damage, property damage was estimated at about $311 million. Most damage occurred in Anchorage,75 mi northwest of the epicenter, the neighborhood lost 75 houses in the landslide, and the destroyed area has since been turned into Earthquake Park
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San Francisco
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San Francisco, officially the City and County of San Francisco, is the cultural, commercial, and financial center of Northern California. It is the birthplace of the United Nations, the California Gold Rush of 1849 brought rapid growth, making it the largest city on the West Coast at the time. San Francisco became a consolidated city-county in 1856, after three-quarters of the city was destroyed by the 1906 earthquake and fire, San Francisco was quickly rebuilt, hosting the Panama-Pacific International Exposition nine years later. In World War II, San Francisco was a port of embarkation for service members shipping out to the Pacific Theater. Politically, the city votes strongly along liberal Democratic Party lines, San Francisco is also the headquarters of five major banking institutions and various other companies such as Levi Strauss & Co. Dolby, Airbnb, Weebly, Pacific Gas and Electric Company, Yelp, Pinterest, Twitter, Uber, Lyft, Mozilla, Wikimedia Foundation, as of 2016, San Francisco is ranked high on world liveability rankings. The earliest archaeological evidence of habitation of the territory of the city of San Francisco dates to 3000 BC. Upon independence from Spain in 1821, the became part of Mexico. Under Mexican rule, the system gradually ended, and its lands became privatized. In 1835, Englishman William Richardson erected the first independent homestead, together with Alcalde Francisco de Haro, he laid out a street plan for the expanded settlement, and the town, named Yerba Buena, began to attract American settlers. Commodore John D. Sloat claimed California for the United States on July 7,1846, during the Mexican–American War, montgomery arrived to claim Yerba Buena two days later. Yerba Buena was renamed San Francisco on January 30 of the next year, despite its attractive location as a port and naval base, San Francisco was still a small settlement with inhospitable geography. The California Gold Rush brought a flood of treasure seekers, with their sourdough bread in tow, prospectors accumulated in San Francisco over rival Benicia, raising the population from 1,000 in 1848 to 25,000 by December 1849. The promise of fabulous riches was so strong that crews on arriving vessels deserted and rushed off to the gold fields, leaving behind a forest of masts in San Francisco harbor. Some of these approximately 500 abandoned ships were used at times as storeships, saloons and hotels, many were left to rot, by 1851 the harbor was extended out into the bay by wharves while buildings were erected on piles among the ships. By 1870 Yerba Buena Cove had been filled to create new land, buried ships are occasionally exposed when foundations are dug for new buildings. California was quickly granted statehood in 1850 and the U. S. military built Fort Point at the Golden Gate, silver discoveries, including the Comstock Lode in Nevada in 1859, further drove rapid population growth. With hordes of fortune seekers streaming through the city, lawlessness was common, and the Barbary Coast section of town gained notoriety as a haven for criminals, prostitution, entrepreneurs sought to capitalize on the wealth generated by the Gold Rush
24.
Marina District, San Francisco
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The Marina District is a neighborhood located in San Francisco, California. The neighborhood sits on the site of the 1915 Panama–Pacific International Exposition, aside from the Palace of Fine Arts, all other buildings were demolished to make the current neighborhood. Much of the Marina is built on landfill, and is susceptible to soil liquefaction during strong earthquakes. This phenomenon caused extensive damage to the neighborhood during the 1989 Loma Prieta earthquake. The area in the 19th century prior to the 1906 earthquake consisted of bay shallows, tidal pools, sand dunes, human habitation and development came in the mid to late 19th century in the form of a sandwall and of a road from the nearby Presidio to Fort Mason. Most of the dunes were leveled out and a hodgepodge of wharves. However, all of this was destroyed in the 1906 earthquake, during reconstruction of the city after the 1906 earthquake, the area was chosen as the site of the Panama–Pacific International Exposition. Although rubble from the earthquake was used as part of the reclamation, most of the landfill came from dredging mud. After the end of the exposition in 1915, the land was sold to private developers and this major redevelopment was completed in the 1920s. In the 1930s, with the completion of the nearby Golden Gate Bridge, Lombard Street was widened, the 1989 Loma Prieta earthquake caused severe liquefaction of the fill upon which the neighborhood is built, causing major damage including a small firestorm. Firefighters resorted to pumping water directly from the Bay, to replace water unavailable from broken water mains, physically, the neighborhood appears to have changed very little since its construction in the 1920s. The Palace is the building left standing in its original location within the 1915 Exposition fairgrounds. The grounds around the Palace are a popular attraction for tourists and locals. The neighborhood is noted for its demographics, which since the 1980s have shifted from mostly middle-class families and pensioners. These now make up more than half of the population, although a small, San Franciscos Academy of Art University has a campus housing building at the Southern edge of the neighborhood on Lombard Street. The San Francisco Police Department Northern Station serves the Marina District, a16 Strangers in the night – Bars, cheap sex, and boozy anthropology
25.
1989 Loma Prieta earthquake
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The 1989 Loma Prieta earthquake occurred in Northern California on October 17 at 5,04 p. m. local time. With a moment magnitude of 6.9 and a maximum Mercalli intensity of IX, no surface faulting occurred, though a large number of other ground failures and landslides were present, especially in the Summit area of the Santa Cruz Mountains. Due to the coverage of the 1989 World Series, it became the first major earthquake in the United States that was broadcast live on national television. Andrew Lawson, a geologist from the University of California, Berkeley, had named the fault after the San Andreas Lake and later led an investigation into that event. The San Andreas Fault ruptured for a length of 290 mi during the 1906 shock, several long term forecasts for a large shock along the San Andreas Fault in that area had been made public prior to 1989 but the earthquake that transpired was not what had been anticipated. The 1989 Loma Prieta event originated on an undiscovered oblique-slip reverse fault that is located adjacent to the San Andreas Fault, since many forecasts had been presented for the region near Loma Prieta, seismologists were not taken by surprise by the October 1989 event. Two moderate shocks, referred to as the Lake Elsman earthquakes by the USGS, occurred in the Santa Cruz Mountains region in June 1988, each events aftershock sequence and effect on stress drop was closely examined, and their study indicated that the shocks affected the mainshocks rupture process. The June 27,1988, shock occurred with an intensity of VI. Its effects included broken windows in Los Gatos, and other damage in Holy City. Farther away from the Santa Cruz Mountains, pieces of concrete fell from a structure at the Sunnyvale Town Center. More moderate damage resulted from the August 8,1989, shock when chimneys were toppled in Cupertino, Los Gatos, other damage included cracked walls and foundations and broken underground pipes. At the office of the Los Gatos City Manager, a window that was cracked had also broken in the earlier shock. Also in Los Gatos, one man died when he exited a building through a window, the Loma Prieta earthquake was named for Loma Prieta Peak in the Santa Cruz Mountains, which lies just to the east of the mainshock epicenter. At sites with rocky terrain, the duration was shorter and the shaking was much less intense, the strong motion records also allowed for the causative fault to be determined – the rupture was related to the San Andreas Fault System. While a Mercalli Intensity of VIII covered a large swath of territory relatively close to the further to the north. At more than 44 miles distant, the San Francisco Bay Area recorded peak horizontal accelerations that were as high as 0. 26g, in a general way, the location of aftershocks of the event delineated the extent of the faulting, which extended about 24 miles in length. Because the rupture took place bilaterally, the duration of strong shaking was about half of what it would have been had it ruptured in one direction only, the duration of a typical M6.9 shock with a comparable rupture length would have been about twice as long. Gregory Beroza, a seismologist with Stanford University, made several distinctions regarding the 1906 and 1989 events, near Loma Prieta, the 1906 rupture was more shallow, had more strike-slip, and occurred on a fault that was near vertical
26.
Port of Kobe
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The Port of Kobe is a Japanese maritime port in Kobe, Hyōgo in the greater Osaka area, backgrounded by the Hanshin Industrial Region. In the 10th century, Taira no Kiyomori renovated the then Ōwada no Tomari and moved to Fukuhara, throughout medieval era, the port was known as Hyōgo no Tsu. In 1858 the Treaty of Amity and Commerce opened the Hyōgo Port to foreigners, after the World War II pillars were occupied by the Allied Forces, later by United States Forces Japan. In the 1970s the port boasted it handled the most containers in the world and it was the worlds busiest container port from 1973 to 1978. Most of the losses were uninsured, as only 3% of property in the Kobe area was covered by earthquake insurance, compared to 16% in Tokyo. Kobe was one of the worlds busiest ports prior to the earthquake and it remains Japans fourth busiest container port. Cruise lines that call at port are kinds like Holland America Line, in the summer of 2014 Princess will expand the market in Kobe when their ship Sun Princess sails eight-day roundtrip Asia cruises from the port
27.
Great Hanshin earthquake
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The Great Hanshin earthquake, or Kobe earthquake, occurred on January 17,1995 at 05,46,53 JST in the southern part of Hyōgo Prefecture, Japan, known as Hanshin. It measured 6.9 on the moment magnitude scale and 7 on the JMA Shindo intensity scale, the tremors lasted for approximately 20 seconds. The focus of the earthquake was located 17 km beneath its epicenter, up to 6,434 people lost their lives, about 4,600 of them were from Kobe. Among major cities, Kobe, with its population of 1.5 million, was the closest to the epicenter and this was Japans worst earthquake in the 20th century after the Great Kantō earthquake in 1923, which claimed more than 105,000 lives. Earthquakes of these types are especially frequent in the regions of northeastern Japan. The Great Hanshin earthquake belonged to a type, called an inland shallow earthquake. Earthquakes of this type occur along active faults, even at lower magnitudes, they can be very destructive because they often occur near populated areas and because their hypocenters are located less than 20 km below the surface. The Great Hanshin earthquake began north of the island of Awaji and it spread toward the southwest along the Nojima Fault on Awaji and toward the northeast along the Suma and Suwayama faults, which run through the center of Kobe. Observations of deformations in these faults suggest that the area was subjected to east-west compression, the Mj 7.3 earthquake struck at 05,46 JST on the morning of January 17,1995. During this time the side of the Nojima Fault moved 1.5 meters to the right and 1.2 meters downwards. There were four foreshocks, beginning with the largest at 18,28 on the previous day and it was the first time that an earthquake in Japan was officially measured at a seismic intensity of the highest Level 7 on the scale of Japan Meteorological Agency. After the earthquake, seismic intensity observation in Japan was fully mechanized, tremors were valued at seismic intensity of Levels 4 to 6 at observation points in Kansai, Chūgoku, Shikoku and Chūbu regions, Level 6 in the cities of Sumoto and Kobe. Level 5 in the cities of Toyooka, Hikone and Kyoto, Level 4 in the prefectures of Hyōgo, Shiga, Kyoto, Fukui, Gifu, Mie, Osaka, Nara, Wakayama, Tottori, Okayama, Hiroshima, Tokushima, Kagawa and Kōchi. Damage was extremely widespread and severe, structures irreparably damaged by the quake included nearly 400,000 buildings, numerous elevated road and rail bridges, and 120 of the 150 quays in the port of Kobe. The quake triggered around 300 fires, which raged over large portions of the city, disruptions of water, electricity and gas supplies were extremely common. In addition, residents were afraid to return home because of aftershocks that lasted several days, the majority of deaths, over 4,000, occurred in cities and suburbs in Hyōgo Prefecture. A total of 68 children under the age of 18 were orphaned, one in five of the buildings in the worst-hit areas were completely destroyed. About 22% of the offices in Kobes central business district were rendered unusable, high rise buildings that were built after the modern 1981 building code suffered little, however, those that were not constructed to these standards suffered serious structural damage
28.
Christchurch
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Christchurch is the largest city in the South Island of New Zealand and the seat of the Canterbury Region. The Christchurch urban area lies on the South Islands east coast, just north of Banks Peninsula and it is home to 389,700 residents, making it New Zealands third most-populous urban area behind Auckland and Wellington. The city was named by the Canterbury Association, which settled the province of Canterbury. The name of Christchurch was agreed on at the first meeting of the association on 27 March 1848 and it was suggested by John Robert Godley, who had attended Christ Church, Oxford. Some early writers called the town Christ Church, but it was recorded as Christchurch in the minutes of the management committee of the association, Christchurch became a city by Royal Charter on 31 July 1856, making it officially the oldest established city in New Zealand. The Avon River flows through the centre of the city, with a park located along its banks. At the request of the Deans brothers, the river was named after the River Avon in Scotland, the usual Māori name for Christchurch is Ōtautahi. This was originally the name of a site by the Avon River near present-day Kilmore Street. The site was a dwelling of Ngāi Tahu chief Te Potiki Tautahi. The Ōtautahi name was adopted in the 1930s, prior to that the Ngāi Tahu generally referred to the Christchurch area as Karaitiana, a transliteration of the English word Christian. The citys name is abbreviated by New Zealanders to Chch. In New Zealand Sign Language, the name is the fingerspelled letter C signed twice, with the second to the right of the first. Archaeological evidence found in a cave at Redcliffs in 1876 has indicated that the Christchurch area was first settled by moa-hunting tribes about 1250 CE. These first inhabitants were thought to have followed by the Waitaha tribe. Following tribal warfare, the Waitaha were dispossessed by the Ngati Mamoe tribe and they were in turn subjugated by the Ngāi Tahu tribe, who remained in control until the arrival of European settlers. Their abandoned holdings were taken over by the Deans brothers in 1843 who stayed, the First Four Ships were chartered by the Canterbury Association and brought the first 792 of the Canterbury Pilgrims to Lyttelton Harbour. These sailing vessels were the Randolph, Charlotte Jane, Sir George Seymour, the Charlotte Jane was the first to arrive on 16 December 1850. The Canterbury Pilgrims had aspirations of building a city around a cathedral and college, the name Christ Church was decided prior to the ships arrival, at the Associations first meeting, on 27 March 1848
29.
2010 Canterbury earthquake
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Some damaging aftershocks followed the main event, the strongest of which was a magnitude 6.3 shock known as the Christchurch earthquake that occurred nearly six months later on 22 February 2011. Because this aftershock was centred very close to Christchurch, it was more destructive. The main shock on 4 September caused widespread damage and several power outages, particularly in the city of Christchurch, two residents were seriously injured, one by a collapsing chimney and a second by flying glass. One person died of a heart attack suffered during the quake, the earthquakes epicentre was 40 kilometres west of Christchurch, near the town of Darfield. The hypocentre was at a depth of 10 km. A foreshock of roughly magnitude 5.8 hit five seconds before the main quake, the initial quake lasted about 40 seconds, and was felt widely across the South Island, and in the North Island as far north as New Plymouth. As the epicentre was on away from the coast, no tsunami occurred. Initially, a curfew was established for parts of Christchurch Central City from 7,00 pm to 7,00 am in response to the earthquake, the New Zealand Army was deployed to the worst affected areas in Canterbury. The latest estimated total damage bill may be as high as $40 billion NZD, in the first eighty years of European settlement in Christchurch, four earthquakes caused significant damage, the last of them centred at Motunau on the North Canterbury coast in 1922. Modelling conducted for the New Zealand Earthquake Commission in 1991 found that earthquakes with a Mercalli intensity of VIII could recur on average in the Christchurch area every 55 years. The study also highlighted the dangers of soil liquefaction of the sediments underlying the city. About 100 faults and fault segments have been recognised around the region, the closest faults to Christchurch capable of producing powerful earthquakes are found in the Rangiora-Cust area, near Hororata, and near Darfield. The earthquake epicentre is located about 80–90 km to the south, the peak ground acceleration measured near Darfield was 1. 26g, recorded near Darfield. This was considered by GNS scientists as an extremely rare recording made near a fault rupture. However, the February 2011 Christchurch earthquake experienced PGA of 2.2 g, as of 7 August 2012,11, 000+ aftershocks of magnitude 2 or more have been recorded, including 26 over 5.0 magnitude, and 2 over 6.0 magnitude. Many have caused damage to buildings in the central business district. Notable aftershocks in order include, On 8 September 2010, there was a large 5.1 magnitude aftershock with an epicentre just 7 km from the city centre. On 19 October 2010 a magnitude 5.0 aftershock with a depth of just 9 km which caused surface shaking reported at the time to be the worst since the original earthquake
30.
June 2011 Christchurch earthquake
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The June 2011 Christchurch earthquake was a shallow magnitude 6.3 ML earthquake that occurred on 13 June 2011 at 14,20 NZST. It was centred at a depth of 6 km, about 10 km from Christchurch, the June quake was preceded by a magnitude 5.9 ML tremor that struck the region at a slightly deeper 8.9 km. The United States Geological Survey reported a magnitude of 6.0 Mw at a depth of about 9 km, the damaged tower of the historic Lyttelton Timeball Station collapsed before dismantling work could be completed. The earthquake downed phone lines and triggered widespread outages, which left around 54,000 households without power, rebuilding costs in Christchurch increased by NZ$6 billion owing to the additional damage from the quake. Forty-six people suffered injuries, and one man died after being knocked unconscious. New Zealand in its entirety, particularly the North Island, is located along the seismically volatile Pacific Ring of Fire, and has a long history of earthquakes. Since the European settlement, the largest on record was a magnitude 8.2 ML major earthquake occurred on 23 January 1855 near the Wairarapa plains of the North Island. In comparison, the South Island has experienced fewer large earthquakes, the magnitude 7.1 Mw event of 4 September 2010 produced by far the strongest ground motions ever recorded in the Canterbury region, triggering a large number of aftershocks. The event has led to the discovery of previously dormant geological faults across central-eastern South Island, in particular beneath regional plains and the adjacent seabed. The magnitude 6.3 ML earthquake occurred inland on 13 June 2011 at 14,20 NZST, at a depth of 6.0 km, about 10 km to the east-southeast of Christchurch. Owing to the interaction of the major Pacific and Australia Plates, the June earthquake was preceded by a magnitude 5.9 ML tremor with a similar focal mechanism that struck 1 hour and 20 minutes earlier. Experts believe the quakes were triggered by a previously undiscovered fault in the region, located several kilometres south of the Port Hills Fault. The United States Geological Survey reported a magnitude of 6.0 Mw, seismologists reported that the earthquakes were part of a prolonged aftershock sequence associated with the major magnitude 7.1 earthquake of September 2010, which includes the February 2011 event. They were succeeded by multiple lighter aftershocks, the strongest, a moderate magnitude 5.1 ML struck a minute after the event. Another tremor 5.0 ML struck the two days later. 0–6.9 ML earthquake occurring in the Canterbury aftershock zone within the 12 months following the event. Weeks later, a magnitude 5.4 ML tremor jolted Christchurch overnight on 22 June, causing additional damage, focused only several kilometres below the surface, the earthquake resulted in significant shaking over a large portion of central-eastern South Island. Maximum ground motions registered at VIII on the Mercalli intensity scale in Christchurch, while strong shaking was felt in adjacent populated areas such as Rolleston, the landforms of Sumner recorded intensified shaking due to the effects of its topographic setting. Widespread lighter motions were observed throughout much of the remaining region, the earthquake was felt as far away as New Plymouth and Invercargill
31.
Effective stress
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Effective stress is a force that keeps a collection of particles rigid. Usually this applies to sand, soil, or gravel, if you pinch a stack of coins between your fingers, the stack stays together. If you then loosen the pressure between your fingers, the coin stack falls apart, similarly, a pile of sand keeps from spreading out like a liquid because the weight of the sand keeps the grains stuck together in their current arrangement, mostly out of static friction. This weight and pressure is the effective stress, effective stress is easy to disrupt by the application of additional forces, every footstep on a sand pile demonstrates this. It is an important factor in the study of stability and soil liquefaction. Karl von Terzaghi first proposed the relationship for effective stress in 1925, for him, the term effective meant the calculated stress that was effective in moving soil, or causing displacements. It represents the average stress carried by the soil skeleton, with these models, it is important to know the total weight of the soil above, and the pore water pressure within the slip plane, assuming it is acting as a confined layer. Consider a grouping of round quartz sand grains, piled loosely, as can be seen, there is a contact stress where the spheres actually touch. Pile on more spheres and the contact stresses increase, to the point of causing frictional instability, the independent parameter affecting the contacts is the force of the spheres above. This can be calculated by using the average density of the spheres. If we then have these spheres in a beaker and add some water, with natural soil materials, the effect can be significant, as anyone who has lifted a large rock out of a lake can attest. The contact stress on the spheres decreases as the beaker is filled to the top of the spheres, although the water pressure between the spheres is increasing, the effective stress remains the same, because the concept of total stress includes the weight of all the water above. This is where the equation can become confusing, and the stress can be calculated using the buoyant density of the spheres. The concept of effective stress truly becomes interesting when dealing with non-hydrostatic pore water pressure, under the conditions of a pore pressure gradient, the ground water flows, according to the permeability equation. Using our spheres as a model, this is the same as injecting water between the spheres, if water is being injected, the seepage force acts to separate the spheres and reduces the effective stress. Thus, the mass becomes weaker. If water is being withdrawn, the spheres are forced together, as well, effective stress plays an important role in slope stability, and other geotechnical engineering and engineering geology problems, such as groundwater-related subsidence
32.
Aberfan disaster
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The Aberfan disaster was the catastrophic collapse of a colliery spoil tip in the Welsh village of Aberfan, near Merthyr Tydfil, that killed 116 children and 28 adults on 21 October 1966. The collapse was caused by the build-up of water in the rock and shale tip. More than 1.4 million cubic feet of debris covered a section of the village in minutes, the classrooms at Pantglas Junior School were immediately inundated, young children and teachers died from impact or suffocation. The official inquiry blamed the National Coal Board for extreme negligence, Parliament passed new legislation regarding public safety in relation to mines and quarries. In 1966 the Aberfan Disaster Memorial Fund received 90,000 contributions, the remaining tips were only made safe after a lengthy fight by Aberfan residents who were resisted by the NCB and Labour Government of Harold Wilson. Clearing was paid for by a government grant and forced contribution of £150,000 taken from the charity fund. In 1997 Tony Blairs New Labour Government paid back the £150,000 to the ADMF and in 2007 the Welsh Assembly donated £1.5 million to ADMF as recompense for the money wrongly taken. For 50 years up to 1966, millions of tonnes of excavated mining debris from the Merthyr Vale Colliery were deposited on the side of Mynydd Merthyr, a ridge directly above the village of Aberfan. Spoil heaps or tips of loose rock and mining waste had been built up above a layer of sandstone containing several underground springs. Since 1947, the mine had operated by the National Coal Board. Local worries about the tip were generally dismissed, in 1964 local councillor Gwyneth Williams warned that if the tip were to move it could threaten the school. In 1965 a petition against the tip from mothers of children at Pantglas school was presented by headmistress Ann Jennings to Merthyr County Borough Council, ms Jennings and many of the petitioners children died in the disaster. Aberfan resident Dai Tudor said I’ve warned and campaigned for years about that tip, nobody in authority took any notice. This is not just the greatest tragedy in Wales, One point of complaint did receive a reply. Because tailings tended to set hard when dry they were generally rewetted before tipping, exacerbating existing problems of flooding in the Pantglas area. His superior raised the issue with local officials, they did not immediately identify an alternative disposal method for tailings. A tip slide had occurred in the autumn of 1963, this was regarded as a run by the NCB. Early on the morning of Friday,21 October 1966, after days of heavy rain
33.
Drainage
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Drainage is the natural or artificial removal of surface and sub-surface water from an area. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging, all houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered drains, which lined the major streets, the invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753. New drainage systems incorporate geotextile filters that retain and prevent fine grains of soil from passing into, geotextiles are synthetic textile fabrics specially manufactured for civil and environmental engineering applications. Geotextiles are designed to retain fine soil particles while allowing water to pass through, in a typical drainage system they would be laid along a trench which would then be filled with coarse granular material, gravel, sea shells, stone or rock. The geotextile is then folded over the top of the stone, groundwater seeps through the geotextile and flow within the stone to an outfell. In high groundwater conditions a perforated pipe is laid along the base of the drain to increases the volume of water transported in the drain. Alternatively, the prefabricated plastic drainage system made of HDPE called SmartDitch, often incorporating geotextile, over the past 30 years geotextile and PVC filters have become the most commonly used soil filter media. They are cheap to produce and easy to lay, with factory controlled properties that ensure long term filtration performance even in fine silty soil conditions, seattles Public Utilities created a pilot program called Street Edge Alternatives Project. The project focuses on designing a system to provide drainage that more closely mimics the natural landscape prior to development than traditional piped systems, the streets are characterized by ditches along the side of the roadway, with plantings designed throughout the area. An emphasis on non curbed sidewalks allows water to more freely into the areas of permeable surface on the side of the streets. Because of the plantings the run off water from the area does not all directly go into the ground. Sustainable Urban Drainage Systems are designed to encourage contractors to install drainage system that closely mimic the natural flow of water in nature. Since 2010 local and neighbourhood planning in the UK is required by law to factor SUDS into any development projects that they are responsible for, slot drainage has proved the most breakthrough product of the last twenty years as a drainage option. Both stainless steel and concrete channel slot drainage have become industry standards on construction projects, the civil engineer is responsible for drainage in construction projects. They set out from the all the roads, street gutters, drainage, culverts. During the construction process he/she will set out all the levels for each of the previously mentioned factors. Civil engineers and construction managers work alongside architects and supervisors, planners, quantity surveyors, typically, most jurisdictions have some body of drainage law to govern to what degree a landowner can alter the drainage from his parcel
34.
Gravel
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Gravel /ˈɡrævəl/ is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel is categorized by the Udden-Wentworth scale into granular gravel and pebble gravel, one cubic metre of gravel typically weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications, many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac, both sand and small gravel are also important for the manufacture of concrete. Large gravel deposits are a geological feature, being formed as a result of the weathering. The action of rivers and waves tends to pile up gravel in large accumulations and this can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the deposition of gravel in the region during the Ice Ages. As of 2006, the United States is the leading producer and consumer of gravel. The word gravel comes from the Breton language, adding the -el suffix in Breton denotes the component parts of something larger. Thus gravel means the stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravele or gravelle, Gravel often has the meaning a mixture of different size pieces of stone mixed with sand and possibly some clay. American English also allows small stones without sand mixed in also known as crushed stone, types of gravel include, Bank gravel, naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as Bank run or River run, bench gravel, a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. Creek rock, this is rounded, semi-polished stones, potentially of a wide range of types. It is also used as concrete aggregate and less often as a paving surface. Crushed stone, rock crushed and graded by screens and then mixed to a blend of stones and fines and it is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, also known as crusher run, DGA QP, and shoulder stone
35.
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
36.
Volume
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Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance or shape occupies or contains. Volume is often quantified numerically using the SI derived unit, the cubic metre, three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straight-edged, Volumes of a complicated shape can be calculated by integral calculus if a formula exists for the shapes boundary. Where a variance in shape and volume occurs, such as those that exist between different human beings, these can be calculated using techniques such as the Body Volume Index. One-dimensional figures and two-dimensional shapes are assigned zero volume in the three-dimensional space, the volume of a solid can be determined by fluid displacement. Displacement of liquid can also be used to determine the volume of a gas, the combined volume of two substances is usually greater than the volume of one of the substances. However, sometimes one substance dissolves in the other and the volume is not additive. In differential geometry, volume is expressed by means of the volume form, in thermodynamics, volume is a fundamental parameter, and is a conjugate variable to pressure. Any unit of length gives a unit of volume, the volume of a cube whose sides have the given length. For example, a cubic centimetre is the volume of a cube whose sides are one centimetre in length, in the International System of Units, the standard unit of volume is the cubic metre. The metric system also includes the litre as a unit of volume, thus 1 litre =3 =1000 cubic centimetres =0.001 cubic metres, so 1 cubic metre =1000 litres. Small amounts of liquid are often measured in millilitres, where 1 millilitre =0.001 litres =1 cubic centimetre. Capacity is defined by the Oxford English Dictionary as the applied to the content of a vessel, and to liquids, grain, or the like. Capacity is not identical in meaning to volume, though closely related, Units of capacity are the SI litre and its derived units, and Imperial units such as gill, pint, gallon, and others. Units of volume are the cubes of units of length, in SI the units of volume and capacity are closely related, one litre is exactly 1 cubic decimetre, the capacity of a cube with a 10 cm side. In other systems the conversion is not trivial, the capacity of a fuel tank is rarely stated in cubic feet, for example. The density of an object is defined as the ratio of the mass to the volume, the inverse of density is specific volume which is defined as volume divided by mass. Specific volume is an important in thermodynamics where the volume of a working fluid is often an important parameter of a system being studied
37.
Holocene
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The Holocene is the geological epoch that began after the Pleistocene at approximately 11,700 years before present. The term Recent has often used as an exact synonym of Holocene. The Holocene is part of the Quaternary period and its name comes from the Ancient Greek words ὅλος and καινός, meaning entirely recent. It has been identified with the current warm period, known as MIS1, given these, a new term, Anthropocene, is specifically proposed and used informally only for the very latest part of modern history involving significant human impact. It is accepted by the International Commission on Stratigraphy that the Holocene started approximately 11,700 years ago, the epoch follows the Pleistocene and the last glacial period. The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations, Preboreal, Boreal, Atlantic, Subboreal and they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the changes were claimed to occur more widely. The periods of the include a few of the final pre-Holocene oscillations of the last glacial period. Paleontologists have not defined any faunal stages for the Holocene, if subdivision is necessary, periods of human technological development, such as the Mesolithic, Neolithic, and Bronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world, climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods, the boundary coincides with the start of the Bronze Age in Europe. According to some scholars, a division, the Anthropocene, has now begun. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years, however, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea, Holocene marine fossils are known, for example, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with depression, Holocene fossils are found primarily in lakebed, floodplain. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely tectonic uplift of non-glacial origin, post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe, the equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. It appears that this was influenced by the glacial ice remaining in the Northern Hemisphere until the later date
38.
Silt
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Silt is granular material of a size between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil or as sediment mixed in suspension with water in a body of such as a river. It may also exist as soil deposited at the bottom of a water body, Silt has a moderate specific area with a typically non-sticky, plastic feel. Silt usually has a floury feel when dry, and a slippery feel when wet, Silt can be visually observed with a hand lens. Silt is created by a variety of physical processes capable of splitting the generally sand-sized quartz crystals of primary rocks by exploiting deficiencies in their lattice and these involve chemical weathering of rock and regolith, and a number of physical weathering processes such as frost shattering and haloclasty. The main process is abrasion through transport, including fluvial comminution, aeolian attrition and it is in semi-arid environments that substantial quantities of silt are produced. Silt is sometimes known as rock flour or stone dust, especially produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar, sedimentary rock composed mainly of silt is known as siltstone. Liquefaction created by an earthquake is silt suspended in water that is hydrodynamically forced up from below ground level. In the Udden–Wentworth scale, silt particles range between 0.0039 and 0.0625 mm, larger than clay but smaller than sand particles, ISO14688 grades silts between 0.002 mm and 0.063 mm. In actuality, silt is chemically distinct from clay, and unlike clay, grains of silt are approximately the size in all dimensions, furthermore. Clays are formed from thin plate-shaped particles held together by electrostatic forces, according to the U. S. Department of Agriculture Soil Texture Classification system, the sand-silt distinction is made at the 0.05 mm particle size. The USDA system has been adopted by the Food and Agriculture Organization, in the Unified Soil Classification System and the AASHTO Soil Classification system, the sand-silt distinction is made at the 0.075 mm particle size. Silts and clays are distinguished mechanically by their plasticity, Silt is easily transported in water or other liquid and is fine enough to be carried long distances by air in the form of dust. Thick deposits of silty material resulting from deposition by aeolian processes are called loess. Silt and clay contribute to turbidity in water, Silt is transported by streams or by water currents in the ocean. When silt appears as a pollutant in water the phenomenon is known as siltation, Silt, deposited by annual floods along the Nile River, created the rich, fertile soil that sustained the Ancient Egyptian civilization. In south east Bangladesh, in the Noakhali district, cross dams were built in the 1960s whereby silt gradually started forming new land called chars, the district of Noakhali has gained more than 28 square miles of land in the past 50 years
39.
Metre
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The metre or meter, is the base unit of length in the International System of Units. The metre is defined as the length of the path travelled by light in a vacuum in 1/299792458 seconds, the metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a metre bar. In 1960, the metre was redefined in terms of a number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted, the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Measuring devices are spelled -meter in all variants of English, the suffix -meter has the same Greek origin as the unit of length. This range of uses is found in Latin, French, English. Thus calls for measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. In 1668, Wilkins proposed using Christopher Wrens suggestion of defining the metre using a pendulum with a length which produced a half-period of one second, christiaan Huygens had observed that length to be 38 Rijnland inches or 39.26 English inches. This is the equivalent of what is now known to be 997 mm, no official action was taken regarding this suggestion. In the 18th century, there were two approaches to the definition of the unit of length. One favoured Wilkins approach, to define the metre in terms of the length of a pendulum which produced a half-period of one second. The other approach was to define the metre as one ten-millionth of the length of a quadrant along the Earths meridian, that is, the distance from the Equator to the North Pole. This means that the quadrant would have defined as exactly 10000000 metres at that time. To establish a universally accepted foundation for the definition of the metre, more measurements of this meridian were needed. This portion of the meridian, assumed to be the length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator
40.
Stream bed
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A stream bed is the channel bottom of a stream, river or creek, the physical confine of the normal water flow. The lateral confines or channel margins are known as the banks or river banks, during all. Under certain conditions a river can branch from one bed to multiple stream beds. A flood occurs when a stream overflows its banks and flows onto its flood plain, as a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation, the nature of any stream bed is always a function of the flow dynamics and the local geologic materials, influenced by that flow. With small streams in mesophytic regions, the nature of the bed is strongly responsive to conditions of precipitation runoff. Where natural conditions of either grassland or forest ameliorate peak flows, stream beds are stable, possibly rich, with organic matter and these streams support a rich biota. Where conditions produce unnatural levels of runoff, such as occurs below roads and this process greatly increases watershed erosion and results in thinner soils, upslope from the stream bed, as the channel adjusts to the increase in flow. The stream bed is very complex in terms of erosion, sediment is transported, eroded and deposited on the stream bed. With global warming there is a fear that the size and shape of riverbeds will change due to increased flood magnitude and this shows that the stream bed is left mostly unchanged in size and shape. Dry stream beds are also subject to becoming underground water pockets and flooding by heavy rains and water rising from the ground and may sometimes be part of the rejuvenation of the stream
41.
Beach
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A beach is a landform along a body of water. It usually consists of particles, which are often composed of rock, such as sand, gravel, shingle, pebbles. The particles comprising a beach are occasionally biological in origin, such as shells or coralline algae. Some beaches have man-made infrastructure, such as posts, changing rooms. They may also have hospitality venues nearby, wild beaches, also known as undeveloped or undiscovered beaches, are not developed in this manner. Wild beaches can be valued for their beauty and preserved nature. Beaches typically occur in areas along the coast where wave or current action deposits, although the seashore is most commonly associated with the word beach, beaches are also found by lakes and alongside large rivers. Beach may refer to, small systems where rock material moves onshore, offshore, or alongshore by the forces of waves and currents, the former are described in detail below, the larger geological units are discussed elsewhere under bars. There are several parts to a beach that relate to the processes that form. The part mostly above water, and more or less influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline, the berm has a crest and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, at some point the influence of the waves on the material comprising the beach stops, and if the particles are small enough, winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune and these geomorphic features compose what is called the beach profile. The beach profile changes seasonally due to the change in energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the profile is higher in summer. The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited, onshore winds carry it further inland forming and enhancing dunes. Conversely, the profile is lower in the storm season due to the increased wave energy. The removal of sediment from the berm and dune thus decreases the beach profile
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Dune
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In physical geography, a dune is a hill of loose sand built by wind or the flow of water. Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water, most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter slip face in the lee of the wind. The valley or trough between dunes is called a slack, a dune field is an area covered by extensive sand dunes. Dunes occur, for example, in deserts and along some coasts. Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach, in most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated with coastal regions, Dunes can form under the action of water flow, and on sand or gravel beds of rivers, estuaries and the sea-bed. The modern word dune came into English from French c,1790, which in turn came from Middle Dutch dūne. Crescent-shaped mounds are generally wider than they are long, the slipfaces are on the concave sides of the dunes. These dunes form under winds that blow consistently from one direction, some types of crescentic dunes move more quickly over desert surfaces than any other type of dune. A group of dunes moved more than 100 metres per year between 1954 and 1959 in Chinas Ningxia Province, and similar speeds have been recorded in the Western Desert of Egypt. The largest crescentic dunes on Earth, with mean crest-to-crest widths of more than three kilometres, are in Chinas Taklamakan Desert. They may be composed of clay, silt, sand, or gypsum, eroded from the floor or shore, transported up the concave side of the dune. Examples in Australia are up to 6.5 km long,1 km wide and they also occur in southern and West Africa, and in parts of the western United States, especially Texas. Straight or slightly sinuous sand ridges typically much longer than they are wide are known as linear dunes and they may be more than 160 kilometres long. Some linear dunes merge to form Y-shaped compound dunes, many form in bidirectional wind regimes. The long axes of these dunes extend in the resultant direction of sand movement, linear loess hills known as pahas are superficially similar. These hills appear to have formed during the last ice age under permafrost conditions dominated by sparse tundra vegetation. Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the center of the mound
43.
Loess
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Loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. It covers about 10% of the Earths surface and it is usually homogeneous and highly porous and is traversed by vertical capillaries that permit the sediment to fracture and form vertical bluffs. It was first applied to Rhine River valley loess about 1821, Loess is homogeneous, porous, friable, pale yellow or buff, slightly coherent, typically non-stratified and often calcareous. Loess grains are angular with little polishing or rounding and composed of crystals of quartz, feldspar, mica, Loess can be described as a rich, dust-like soil. Loess deposits may become thick, more than a hundred meters in areas of China. It generally occurs as a deposit that covers areas of hundreds of square kilometers. Loess often stands in either steep or vertical faces, because the grains are angular, loess will often stand in banks for many years without slumping. This soil has a characteristic called vertical cleavage which makes it easily excavated to form cave dwellings, in several areas of the world, loess ridges have formed that are aligned with the prevailing winds during the last glacial maximum. These are called paha ridges in America and greda ridges in Europe, the form of these loess dunes has been explained by a combination of wind and tundra conditions. Loess comes from the German Löss or Löß, and ultimately from Alemannic lösch meaning loose as named by peasants, the term Löß was first described in Central Europe by Karl Cäsar von Leonhard who reported yellowish brown, silty deposits along the Rhine valley near Heidelberg. Charles Lyell brought this term into usage by observing similarities between loess and loess derivatives along the loess bluffs in the Rhine and Mississippi. At that time it was thought that the yellowish brown silt-rich sediment was of fluvial origin being deposited by the large rivers. It wasnt until the end of the 19th century that the origin of loess was recognized. A tremendous number of papers have been published since then, focusing on the formation of loess and on loess/palaeosol sequences as archives of climate and these water conservation works were carried out extensively in China and the research of Loess in China has been continued since 1954. Much effort was put into the setting up of regional and local loess stratigraphies, and Frechen, Horváth & Gábris for the Austrian and Hungarian loess stratigraphy, respectively. During the autumn and winter, when melting of the icesheets and icecaps ceased, as a consequence, large parts of the formerly submerged and unvegetated floodplains of these braided rivers dried out and were exposed to the wind. Because these floodplains consist of sediment containing a high content of glacially ground flour-like silt and clay, they were susceptible to winnowing of their silts. Once entrained by the wind, particles were then deposited downwind, the loess deposits found along both sides of the Mississippi River Alluvial Valley are a classic example of periglacial loess
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Turbidity current
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A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope. Turbidity currents can occur in other fluids besides water. In the most typical case of oceanic turbidity currents, sediment laden waters situated over sloping ground will flow down-hill because they have a higher density than the adjacent waters. The driving force behind a turbidity current is gravity acting on the density of the sediments temporarily suspended within a fluid. These semi-suspended solids make the density of the sediment bearing water greater than that of the surrounding. As such currents flow, they often have a snow-balling-effect, as they stir up the ground over which they flow and their passage leaves the ground over which they flow scoured and eroded. Once an oceanic turbidity current reaches the waters of the flatter area of the abyssal plain. The sedimentary deposit of a turbidity current is called a turbidite, examples of turbidity currents involving other fluid mediums besides liquid water include, avalanches, lahars, pyroclastic flows, and lava flows. Seafloor turbidity currents are often the result of sediment-laden river outflows and they are characterized by a well-defined advance-front, also known as the currents head, and are followed by the currents main body. In terms of the often observed and more familiar above sea-level phenomenon. With an increasing continental shelf slope, current velocity increases, as the velocity of the flow increases, turbulence increases, the increase in sediment also adds to the density of the current, and thus its velocity even further. Turbidity currents are traditionally defined as those sediment gravity flows in which sediment is suspended by fluid turbulence, however, the term turbidity current was adopted to describe a natural phenomenon whose exact nature is often unclear. Definitions are further complicated by an understanding of the turbulence structure within turbidity currents. A turbidity current is a current in which the interstitial fluid is a liquid. The average concentration of suspended sediment for most river water enters the ocean is much lower than the sediment concentration needed for entry as a hyperpycnal plume. Although some rivers can often have high sediment load that can create a continuous hyperpycnal plume, such as the Haile River. The sediment concentration needed to produce a plume in marine water is 35 to 45 kg/m³. Most rivers produce hyperpycnal flows only during events, such as storms, floods, glacier outbursts, dam breaks
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