1.
Mass wasting
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Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to years. Mass wasting occurs on both terrestrial and submarine slopes, and has observed on Earth, Mars, Venus. When the gravitational force acting on a slope exceeds its resisting force, the slope materials strength and cohesion and the amount of internal friction between material help maintain the slopes stability and are known collectively as the slopes shear strength. The steepest angle that a slope can maintain without losing its stability is known as its angle of repose. When a slope made of loose material possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it. Mass wasting may occur at a slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may also occur at high speed, such as in rockslides or landslides, with disastrous consequences. Factors that change the potential of mass wasting include, change in angle, weakening of material by weathering, increased water content, changes in vegetation cover. Volcano flanks can become over-steep resulting in instability and mass wasting and this is now a recognised part of the growth of all active volcanoes. The failure of the flank of Mount St Helens in 1980 showed how rapidly volcanic flanks can deform. Water can increase or decrease the stability of a slope depending on the amount present, small amounts of water can strengthen soils because the surface tension of water increases soil cohesion. This allows the soil to resist erosion better than if it were dry, if too much water is present the water may act to increase the pore pressure, reducing friction, and accelerating the erosion process and resulting in different types of mass wasting. A good example of this is to think of a sand castle, water must be mixed with sand in order for the castle to keep its shape. If too much water is added the sand away, if not enough water is added the sand falls. Water also increases the mass of the soil, this is important because an increase in mass means that there will be an increase in velocity if mass wasting is triggered. Types of mass movement are distinguished based on how the soil, soil creep is a long term process. The combination of movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep, the creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing
2.
Debris flow
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Debris flows descending steep channels commonly attain speeds that surpass 10 meters per second, although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide, the largest prehistoric flows have had volumes exceeding 1 billion cubic meters. As a result of their high sediment concentrations and mobility, debris flows can be very destructive, notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999. Debris flows have volumetric sediment concentrations exceeding about 40 to 50%, by definition, “debris” includes sediment grains with diverse shapes and sizes, commonly ranging from microscopic clay particles to great boulders. Media reports often use the term mudflow to describe debris flows, on Earths land surface, mudflows are far less common than debris flows. However, underwater mudflows are prevalent on submarine continental margins, where they may spawn turbidity currents, Debris flows in forested regions can contain large quantities of woody debris such as logs and tree stumps. Sediment-rich water floods with solid concentrations ranging from about 10 to 40% behave somewhat differently from debris flows and are known as hyperconcentrated floods, normal stream flows contain even lower concentrations of sediment. Debris flows can be triggered by rainfall or snowmelt, by dam-break or glacial outburst floods. Debris flows can be more frequent following forest and brush fires, in Japan a large debris flow or landslide is called yamatsunami, literally mountain tsunami. Debris flows are accelerated downhill by gravity and tend to follow steep mountain channels that debouche onto alluvial fans or floodplains, the front, or head of a debris-flow surge often contains an abundance of coarse material such as boulders and logs that impart a great deal of friction. Trailing behind the high-friction flow head is a lower-friction, mostly liquefied flow body that contains a percentage of sand, silt. These fine sediments help retain high pore-fluid pressures that enhance debris-flow mobility, in some cases the flow body is followed by a more watery tail that transitions into a hyperconcentrated stream flow. Debris flows tend to move in a series of pulses, or discrete surges, wherein each pulse or surge has a head, body. Debris-flow deposits are readily recognizable in the field and they make up significant percentages of many alluvial fans and debris cones along steep mountain fronts. Lateral levees can confine the paths of ensuing debris flows, through dating of trees growing on such deposits, the approximate frequency of destructive debris flows can be estimated. This is important information for development in areas where debris flows are common. Ancient debris-flow deposits that are exposed only in outcrops are more difficult to recognize and this poor sorting of sediment grains distinguishes debris-flow deposits from most water-laid sediments. Other geological flows that can be described as debris flows are typically given more specific names, the word lahar is of Indonesian origin, but is now routinely used by geologists worldwide to describe volcanogenic debris flows
3.
Lahar
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A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley, lahars are extremely destructive, they can flow tens of metres per second, be 140 metres deep, and destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the word lahar is the Javanese term for flowing lava. A lahar is a volcanic mudflow or debris flow, lahars have the consistency, viscosity and approximate density of wet concrete, fluid when moving, solid at rest. Lahars can be huge.3 cubic kilometres, a lahar of sufficient size and intensity can erase virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a lahar quickly loses force when it leaves the channel of its flow, even frail huts may remain standing, a lahars viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop. Lahars vary in size and speed, small lahars less than a few metres wide and several centimetres deep may flow a few metres per second. Large lahars hundreds of metres wide and tens of metres deep can flow tens of metres per second. With the potential to flow at speeds up to 100 kilometres per hour, and flow distances of more than 300 kilometres, a lahar can cause catastrophic destruction in its path. Lahars from the 1985 Nevado del Ruiz eruption in Colombia caused the Armero tragedy, which killed an estimated 23,000 people, a lahar caused New Zealands Tangiwai disaster, where 151 people died after a Christmas Eve express train fell into the Whangaehu River in 1953. Lahars have been responsible for 17% of volcano-related deaths between 1783 and 1997, a lahar can cause fatalities years after its precipitating eruption. For example, the Cabalantian tragedy occurred four years subsequent to the 1991 eruption of Mount Pinatubo, the word lahar is of Indonesian origin. Lahars have several causes, Snow and glaciers can be melted by lava or pyroclastic flows during an eruption. Lava flows out of vents and can mix with wet soil and mud on the slope of the volcano making a very viscous. A flood caused by a glacier, lake breakout, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup Water from a crater lake, heavy rainfall on unconsolidated pyroclastic deposits. Snow and glaciers can melt during periods of mild weather Earthquakes underneath or close to the volcano can shake material loose and cause it to collapse triggering a lahar avalanche. Rainfall can cause the still-hanging slabs of solidified mud to come rushing down the slopes at a speed of more than 30 kilometres per hour, causing devastating results. Several towns in the Puyallup River valley in Washington state, including Orting, are built on top of lahar deposits that are only about 500 years old
4.
Pyroclastic rock
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Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, pyroclastic rocks may be a range of clast sizes, from the largest agglomerates, to very fine ashes and tuffs. Pyroclasts of different sizes are classified as bombs, lapilli. Ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock, one of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event. Three modes of transport can be distinguished, pyroclastic flow, pyroclastic surge, during Plinian eruptions, pumice and ash are formed when silicic magma is fragmented in the volcanic conduit, because of decompression and the growth of bubbles. Pyroclasts are then entrained in a buoyant eruption plume which can rise several kilometers into the air, particles falling from the eruption clouds form layers on the ground. Pyroclastic density currents, which are referred to as flows or surges depending on particle concentration, the deposits of pumice-rich pyroclastic flows can be called ignimbrites. A pyroclastic eruption entails spitting or fountaining lava, where the lava will be thrown into the air along with ash, pyroclastic materials, hawaiian eruptions such as those at Kīlauea can eject clots of magma suspended into gas, this is called a fire fountain. The magma clots, if hot enough may coalesce upon landing to form a lava flow, pyroclastic deposits consist of pyroclasts which are not cemented together. Pyroclastic rocks are pyroclastic deposits which have been lithified
5.
Tibes
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Tibes is one of the 31 barrios in the municipality of Ponce, Puerto Rico. Together with Magueyes, Portugues, Montes Llanos, Maragüez, Machuelo Arriba, Sabanetas, Tibes attracted attention recently when, in 1975, what was to become the discovery of the oldest cemetery in the West Indies came about as a result of rains. The name of this barrio is of native Indian origin, Tibes is a mountainous rural barrio located in the central section of the municipality, north of the city of Ponce. Tibes is located on the foothills of the Cordillera Central, Tibes has 7.01 square miles of land area and no water area. In 2000, the population of Tibes was 866 persons, Tibes is the second least populated barrio in Ponce, after San Patricio. Major roads serving Barrio Tibes are PR-10 and PR-503, the highest point in Barrio Tibes is Cerro del Diablo which stands at 2,234 feet. Another notable land feature is Cerro La Mesa which stands at 1,742 feet, the Portugues Dam currently under construction and scheduled for completion in 2013, is also located in Barrio Tibes
6.
Puerto Rico
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Puerto Rico, officially the Commonwealth of Puerto Rico and briefly called Porto Rico, is an unincorporated territory of the United States located in the northeast Caribbean Sea. It is an archipelago that includes the island of Puerto Rico and a number of smaller ones such as Mona, Culebra. The capital and most populous city is San Juan and its official languages are Spanish and English, though Spanish predominates. The islands population is approximately 3.4 million, Puerto Ricos rich history, tropical climate, diverse natural scenery, renowned traditional cuisine, and attractive tax incentives make it a popular destination for travelers from around the world. Four centuries of Spanish colonial government transformed the ethnic, cultural and physical landscapes primarily with waves of African captives, and Canarian. In the Spanish imperial imagination, Puerto Rico played a secondary, in 1898, following the Spanish–American War, the United States appropriated Puerto Rico together with most former Spanish colonies under the terms of the Treaty of Paris. Puerto Ricans are natural-born citizens of the United States, however, Puerto Rico does not have a vote in the United States Congress, which governs the territory with full jurisdiction under the Puerto Rico Federal Relations Act of 1950. As a U. S. territory, American citizens residing on the island are disenfranchised at the level and may not vote for president. However, Congress approved a constitution, allowing U. S. citizens on the territory to elect a governor. A fifth referendum will be held in June 2017, with only Statehood, in early 2017, the Puerto Rican government-debt crisis posed serious problems for the government. The outstanding bond debt that had climbed to $70 billion or $12,000 per capita at a time with 12. 4% unemployment, the debt had been increasing during a decade long recession. Puerto Ricans often call the island Borinquen – a derivation of Borikén, its indigenous Taíno name, the terms boricua and borincano derive from Borikén and Borinquen respectively, and are commonly used to identify someone of Puerto Rican heritage. The island is also known in Spanish as la isla del encanto. Columbus named the island San Juan Bautista, in honor of Saint John the Baptist, eventually traders and other maritime visitors came to refer to the entire island as Puerto Rico, while San Juan became the name used for the main trading/shipping port and the capital city. The islands name was changed to Porto Rico by the United States after the Treaty of Paris of 1898, the anglicized name was used by the US government and private enterprises. The name was changed back to Puerto Rico by a joint resolution in Congress introduced by Félix Córdova Dávila in 1931, the ancient history of the archipelago known today as Puerto Rico is not well known. The scarce archaeological findings and early Spanish scholarly accounts from the colonial era constitute the basis of knowledge about them. The first comprehensive book on the history of Puerto Rico was written by Fray Íñigo Abbad y Lasierra in 1786, the first settlers were the Ortoiroid people, an Archaic Period culture of Amerindian hunters and fishermen who migrated from the South American mainland
7.
Snow
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Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system. The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, often, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
8.
Groundwater
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Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is also withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is also evidence that water may also exist in the subsurface of Jupiters moon Europa. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
9.
Flood
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A flood is an overflow of water that submerges land which is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water, in the sense of flowing water, the word may also be applied to the inflow of the tide. Floods can also occur in rivers when the flow exceeds the capacity of the river channel. Floods often cause damage to homes and businesses if they are in the flood plains of rivers. Some floods develop slowly, while others such as floods, can develop in just a few minutes. Additionally, floods can be local, impacting a neighborhood or community, or very large, the word flood comes from the Old English flod, a word common to Germanic languages. Deluge myths are stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths, surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the worlds largest rivers. When overland flow occurs on tilled fields, it can result in a flood where sediments are picked up by run off. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, the cause may be localized convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the rate increased from about 50 to 1,500 cubic feet per second in just one minute. Two larger floods occurred at the site within a week
10.
Erosion
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In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, then transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are also possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, however, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
11.
Sidoarjo mud flow
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The Sidoarjo mud flow or Lapindo mud is the result of an erupting mud volcano in the subdistrict of Porong, Sidoarjo in East Java, Indonesia that has been in eruption since May 2006. At its peak Lusi spewed up to 180,000 m³ of mud per day, by mid August 2011, mud was being discharged at a rate of 10,000 m³ per day, with 15 bubbles around its gushing point. This was a significant decline from the year, when mud was being discharged at a rate of 100,000 cubic metres per day with 320 bubbles around its gushing point. It is expected that the flow will continue for the next 25 to 30 years, although the Sidoarjo mud flow has been contained by levees since November 2008, resultant floodings regularly disrupt local highways and villages, and further breakouts of mud are still possible. Mud volcano systems are common on Earth, and particularly in the Indonesian province of East Java. Beneath the island of Java is a lying in the east-west direction, filled with over-pressured marine carbonates. It forms an inverted extensional basin which has been active since the Paleogene epoch. The basin started to become overpressured during the Oligo-Miocene period, some of the overpressured mud escapes to the surface to form mud volcanoes, which have been observed at Sangiran Dome near Surakarta in Central Java and near Purwodadi city,200 km west of Lusi. The East Java Basin contains a significant amount of oil and gas reserves, as of 2006, three companies—Santos, MedcoEnergi and PT Lapindo Brantas —had concession rights for this area, PT Lapindo Brantas acted as an operator. On May 28,2006, PT Lapindo Brantas targeted gas in the Kujung Formation carbonates in the Brantas PSC area by drilling a borehole named the Banjar-Panji 1 exploration well. In the first stage of drilling the drill string first went through a thick clay seam, then through sands, shales, volcanic debris, the Banjar Panji-1 borehole was cased down to 1,091 m. Two further eruptions occurred on the second and the third of June about 800–1,000 m northwest of the well, during these eruptions, hydrogen sulphide gas was released and local villagers observed hot mud, thought to be at a temperature of around 60 °C. A magnitude 6.3 earthquake occurred in Yogyakarta at ~06,00 local time 27 May 2006, approximately 250 kilometres Southwest of Sidoarjo. The well suffered a loss of circulation at 12, 50pm local time on the 26th May 2006. This mud loss problem was finally stopped when loss circulation material was pumped into the well, a day later the well suffered a ‘kick’, an influx of formation fluid into the well bore. Early the next day, on 29 May 2006, steam, water and mud began erupting up to 200 meters above the well, a phenomenon that is now known as the Lusi mud volcano. Dense drilling mud and cement were pumped down the Banjar Panji-1 well at times in the 48 hours after the mud flow started. A detailed review of the timing of key events in the drilling of Banjar Panji-1, the birth of Lusi was a major disaster for the population living nearby, with loss of their houses, properties and their livelihood
12.
Viscosity
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The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the concept of thickness, for example. Viscosity is a property of the fluid which opposes the motion between the two surfaces of the fluid in a fluid that are moving at different velocities. For a given velocity pattern, the stress required is proportional to the fluids viscosity, a fluid that has no resistance to shear stress is known as an ideal or inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, all fluids have positive viscosity, and are said to be viscous or viscid. A fluid with a high viscosity, such as pitch. The word viscosity is derived from the Latin viscum, meaning mistletoe, the dynamic viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the situation known as a Couette flow. This fluid has to be homogeneous in the layer and at different shear stresses, if the speed of the top plate is small enough, the fluid particles will move parallel to it, and their speed will vary linearly from zero at the bottom to u at the top. Each layer of fluid will move faster than the one just below it, in particular, the fluid will apply on the top plate a force in the direction opposite to its motion, and an equal but opposite one to the bottom plate. An external force is required in order to keep the top plate moving at constant speed. The magnitude F of this force is found to be proportional to the u and the area A of each plate. The proportionality factor μ in this formula is the viscosity of the fluid, the ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the forces by the differential equation τ = μ ∂ u ∂ y, where τ = F/A. This formula assumes that the flow is moving along parallel lines and this equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe. Use of the Greek letter mu for the dynamic viscosity is common among mechanical and chemical engineers. However, the Greek letter eta is used by chemists, physicists
13.
Avalanche
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An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength. After initiation, avalanches usually accelerate rapidly and grow in mass, if the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches, the load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches, Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may trigger the failure in the snowpack and avalanches. A popular myth is that avalanches can be triggered by loud noise or shouting, Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice, there is no universally accepted classification of avalanches—different classifications are useful for different purposes. Avalanches can be described by their size, their potential, their initiation mechanism, their composition. Most avalanches occur spontaneously during storms under increased load due to snowfall, the second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall, artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Avalanche initiation can start at a point with only an amount of snow moving initially. A snowpack will fail when the load exceeds the strength, the load is straightforward, it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogenous and it varies in detail with properties of the snow grains, size, density, morphology, temperature, water content, and the properties of the bonds between the grains. These properties may all metamorphose in time according to the humidity, water vapour flux, temperature. The top of the snowpack is also influenced by incoming radiation. One of the aims of research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time
14.
Hill
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A hill is a landform that extends above the surrounding terrain. It often has a summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit. The distinction between a hill and a mountain is unclear and largely subjective, but a hill is considered to be less tall. The Great Soviet Encyclopedia defines hill as an upland with a height up to 200 m. Today, a mountain is usually defined in the UK and Ireland as any summit at least 2,000 feet high, some definitions include a topographical prominence requirement, typically 100 feet or 500 feet. In practice, mountains in Scotland are frequently referred to as no matter what their height, as reflected in names such as the Cuillin Hills. In Wales, the distinction is more a term of land use, for a while, the U. S. defined a mountain as being 1,000 feet or more tall. Any similar landform lower than this height was considered a hill, the United States Geological Survey, however, has concluded that these terms do not in fact have technical definitions in the U. S. A hillock is a small hill, other words include knoll and its variant, knowe. Artificial hills may be referred to by a variety of names, including mound. Various names used to describe types of hill, based on appearance and these include, Drumlin – an elongated whale-shaped hill formed by glacial action. Butte – an isolated hill with steep sides and a flat top. Kuppe – a rounded hill or low mountain, typical of central Europe Tor – a rock found on a hilltop, also used to refer to the hill. Puy – used especially in the Auvergne, France, to describe a conical volcanic hill, pingo – a mound of earth-covered ice found in the Arctic and Antarctica. For example, Ancient Rome was built on seven hills, protecting it from invaders, in northern Europe, many ancient monuments are sited in heaps. Some of these are structures, but others appear to have hardly any significance. In Britain, many churches at the tops of hills are thought to have built on the sites of earlier pagan holy places. The National Cathedral in Washington, DC has followed this tradition and was built on the highest hill in that city, Hills provide a major advantage to an army, giving them an elevated firing position and forcing an opposing army to charge uphill to attack them
15.
Los Angeles
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Los Angeles, officially the City of Los Angeles and often known by its initials L. A. is the cultural, financial, and commercial center of Southern California. With a census-estimated 2015 population of 3,971,883, it is the second-most populous city in the United States, Los Angeles is also the seat of Los Angeles County, the most populated county in the United States. The citys inhabitants are referred to as Angelenos, historically home to the Chumash and Tongva, Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542 along with the rest of what would become Alta California. The city was founded on September 4,1781, by Spanish governor Felipe de Neve. It became a part of Mexico in 1821 following the Mexican War of Independence, in 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, thereby becoming part of the United States. Los Angeles was incorporated as a municipality on April 4,1850, the discovery of oil in the 1890s brought rapid growth to the city. The completion of the Los Angeles Aqueduct in 1913, delivering water from Eastern California, nicknamed the City of Angels, Los Angeles is known for its Mediterranean climate, ethnic diversity, and sprawling metropolis. Los Angeles also has an economy in culture, media, fashion, science, sports, technology, education, medicine. A global city, it has been ranked 6th in the Global Cities Index, the city is home to renowned institutions covering a broad range of professional and cultural fields, and is one of the most substantial economic engines within the United States. The Los Angeles combined statistical area has a gross metropolitan product of $831 billion, making it the third-largest in the world, after the Greater Tokyo and New York metropolitan areas. The city has hosted the Summer Olympic Games in 1932 and 1984 and is bidding to host the 2024 Summer Olympics and thus become the second city after London to have hosted the Games three times. The Los Angeles area also hosted the 1994 FIFA mens World Cup final match as well as the 1999 FIFA womens World Cup final match, the mens event was watched on television by over 700 million people worldwide. The Los Angeles coastal area was first settled by the Tongva, a Gabrielino settlement in the area was called iyáangẚ, meaning poison oak place. Gaspar de Portolà and Franciscan missionary Juan Crespí, reached the present site of Los Angeles on August 2,1769, in 1771, Franciscan friar Junípero Serra directed the building of the Mission San Gabriel Arcángel, the first mission in the area. The Queen of the Angels is an honorific of the Virgin Mary, two-thirds of the settlers were mestizo or mulatto with a mixture of African, indigenous and European ancestry. The settlement remained a small town for decades, but by 1820. Today, the pueblo is commemorated in the district of Los Angeles Pueblo Plaza and Olvera Street. New Spain achieved its independence from the Spanish Empire in 1821, during Mexican rule, Governor Pío Pico made Los Angeles Alta Californias regional capital
16.
Grain
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Grains are small, hard, dry seeds, with or without attached hulls or fruit layers, harvested for human or animal consumption. Agronomists also call the plants producing such seeds grain crops, the two main types of commercial grain crops are cereals such as wheat and rye, and legumes such as beans and soybeans. Because of the ubiquity of grain as a source, the term grain is often used to describe something small. After being harvested, dry grains are more durable than other foods, such as starchy fruits. Thus, major global commodity markets exist for canola, maize, rice, soybeans, wheat, in botany, grains and cereals are synonymous with caryopses, the fruits of the grass family. In agronomy and commerce, seeds or fruits from other plant families are called if they resemble caryopses. For example, amaranth is sold as grain amaranth, and amaranth products may be described as whole grains, the pre-Hispanic civilizations of the Andes had grain-based food systems but, at the higher elevations, none of the grains was a cereal. All three grains native to the Andes are broad-leafed plants rather than such as corn, rice. All cereal crops are members of the grass family, cereal grains contain a substantial amount of starch, a carbohydrate that provides dietary energy. As is the case all other whole plant foods, pulses also contain carbohydrate. Vegetable oils provide dietary energy and some essential fatty acids and they are also used as fuel or lubricants. Those who handle grain at grain facilities may encounter numerous occupational hazards, risks include grain entrapment, where workers are submerged in the grain and unable to remove themselves, explosions caused by fine particles of grain dust, and falls
17.
Friction
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Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction, Dry friction resists relative lateral motion of two surfaces in contact. Dry friction is subdivided into static friction between non-moving surfaces, and kinetic friction between moving surfaces, fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces, skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. Internal friction is the force resisting motion between the making up a solid material while it undergoes deformation. When surfaces in contact move relative to other, the friction between the two surfaces converts kinetic energy into thermal energy. This property can have consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Kinetic energy is converted to thermal energy whenever motion with friction occurs, another important consequence of many types of friction can be wear, which may lead to performance degradation and/or damage to components. Friction is a component of the science of tribology, Friction is not itself a fundamental force. Dry friction arises from a combination of adhesion, surface roughness, surface deformation. The complexity of interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis. Friction is a non-conservative force - work done against friction is path dependent, in the presence of friction, some energy is always lost in the form of heat. Thus mechanical energy is not conserved, the Greeks, including Aristotle, Vitruvius, and Pliny the Elder, were interested in the cause and mitigation of friction. They were aware of differences between static and kinetic friction with Themistius stating in 350 A. D. that it is easier to further the motion of a moving body than to move a body at rest. The classic laws of sliding friction were discovered by Leonardo da Vinci in 1493, a pioneer in tribology and these laws were rediscovered by Guillaume Amontons in 1699. Amontons presented the nature of friction in terms of surface irregularities, the understanding of friction was further developed by Charles-Augustin de Coulomb. Coulomb further considered the influence of sliding velocity, temperature and humidity, the distinction between static and dynamic friction is made in Coulombs friction law, although this distinction was already drawn by Johann Andreas von Segner in 1758. Leslie was equally skeptical about the role of adhesion proposed by Desaguliers, in Leslies view, friction should be seen as a time-dependent process of flattening, pressing down asperities, which creates new obstacles in what were cavities before
18.
Sediment
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For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
19.
Debris
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Depending on context, debris can refer to a number of different things. The first apparent use of the French word in English is in a 1701 description of the army of Prince Rupert upon its retreat from a battle with the army of Oliver Cromwell, in disaster scenarios, tornados leave behind large pieces of houses and mass destruction overall. This debris also flies around the tornado itself when it is in progress, the tornados winds capture debris it kicks up in its wind orbit, and spins it inside its vortex. The tornados wind radius is larger than the funnel itself, tsunamis and hurricanes also bring large amounts of debris, such as Hurricane Katrina in 2005 and Hurricane Sandy in 2012. Earthquakes rock cities to rubble debris, Geological debris sometimes moves in a stream called a debris flow. In mining, debris called attle usually consists of fragments which contain little or no ore. Marine debris is also called litter or flotsam and jetsam, objects that can constitute marine debris include used automobile tires, detergent bottles, medical wastes, discarded fishing line and nets, soda cans, and bilge waste solids. In addition to being unsightly, it can pose a threat to marine life, boats, swimmers, divers. For example, each year millions of seabirds, sea turtles, fish, as many as 30,000 northern fur seals per year get caught in abandoned fishing nets and either drown or suffocate. Whales mistake plastic bags for squid, and birds may mistake plastic pellets for fish eggs, at other times, animals accidentally eat the plastic while feeding on natural food. The largest concentration of debris is the Great Pacific Garbage Patch. Marine debris most commonly originates from land-based sources, various international agencies are currently working to reduce marine debris levels around the world. In meteorology, debris usually applies to the remains of human habitation and this debris is also commonly referred to as storm debris. Storm debris commonly consists of roofing material, downed tree limbs, downed signs, downed lines and poles. Storm debris can become a problem immediately after a storm, in that it often blocks access to individuals. This material frequently exists in large quantities that disposing of it becomes a serious issue for a community. In addition, storm debris is often hazardous by its nature, since, for example. Space usually refers to the remains of spacecraft that have fallen to Earth or are still orbiting Earth
20.
Vargas (state)
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Vargas State is one of the 23 states of Venezuela. It is home to both the countrys largest seaport and airport, the state capital is La Guaira. The Litoral Varguense conurbation its the principal urban agglomeration in the state, thousands died, and many more fled the area to other states. This region of Venezuela has undergone important changes over the years, and while the borders have remained. The area was one of the departments of the Venezuelas Federal District. The area later evolved into a municipality, but was dependent on the governor of the Federal District. In the 1990s there were increased calls for Vargas to become a separate entity, in 1998 the government of Rafael Caldera decreed Vargas as an independent municipality, separate from the Federal District, with the statute of Federal Territory. Shortly after it became the 23rd state of Venezuela, official estimates some 50,000 dead or missing, but the real figure may be much higher. In the following weeks nearly the entire population was displaced. Locals refer to the Dec.1999 disaster as La Tragedia de Vargas, such climatic phenomenon appears to be periodical, having a cycle of about 70 years, and probably has occurred hundreds, perhaps thousands of times since a distant past. Vargas State covers a surface area of 1,497 km²
21.
Venezuela
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Venezuela, officially the Bolivarian Republic of Venezuela, is a federal republic located on the northern coast of South America. It is bordered by Colombia on the west, Brazil on the south, Guyana on the east, Venezuela covers 916,445 km2 and has an estimated population of 31775371. The territory now known as Venezuela was colonized by Spain in 1522 amid resistance from indigenous peoples and it gained full independence as a separate country in 1830. During the 19th century, Venezuela suffered political turmoil and autocracy, since 1958, the country has had a series of democratic governments. This new constitution changed the name of the country to República Bolivariana de Venezuela. Venezuela is a presidential republic consisting of 23 states, the Capital District. Venezuela also claims all Guyanese territory west of the Essequibo River, oil was discovered in the early 20th century, and Venezuela has the worlds largest known oil reserves and has been one of the worlds leading exporters of oil. Previously an underdeveloped exporter of commodities such as coffee and cocoa, oil quickly came to dominate exports. The recovery of oil prices in the early 2000s gave Venezuela oil funds not seen since the 1980s, the Venezuelan government then established populist policies that initially boosted the Venezuelan economy and increased social spending, significantly reducing economic inequality and poverty. However, such policies later became controversial since they destabilized the economy, resulting in hyperinflation, an economic depression. According to the most popular and accepted version, in 1499, the stilt houses in the area of Lake Maracaibo reminded the navigator, Amerigo Vespucci, of the city of Venice, so he named the region Veneziola Piccola Venezia. The name acquired its current spelling as a result of Spanish influence, where the suffix -uela is used as a term, thus. The German language 16th century-term for the area, Klein-Venedig, also means little Venice, however, Martín Fernández de Enciso, a member of the Vespucci and Ojeda crew, gave a different account. In his work Summa de geografía, he states that they found people who called themselves the Veneciuela. Thus, the name Venezuela may have evolved from the native word and it is not known how many people lived in Venezuela before the Spanish conquest, it has been estimated at around one million. In addition to indigenous peoples known today, the population included historic groups such as the Kalina, Auaké, Caquetio, Mariche, the Timoto-Cuica culture was the most complex society in Pre-Columbian Venezuela, with pre-planned permanent villages, surrounded by irrigated, terraced fields. They also stored water in tanks and their houses were made primarily of stone and wood with thatched roofs. They were peaceful, for the most part, and depended on growing crops, regional crops included potatoes and ullucos
22.
Vargas tragedy
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According to relief workers, the neighborhood of Los Corales was buried under 3 metres of mud and a high percentage of homes were simply swept away to the ocean. Whole towns like Cerro Grande and Carmen de Uria completely disappeared, as much as 10% of the population of Vargas perished during this event. The coastal area of Vargas has long been subject to mudslides and flooding, the most recent major flood was in 1951, however that event did not cause as much damage. The unusually strong storm in December 1999 dumped 911 millimetres of rain over just a few days, triggering soil instability, the state had experienced high population growth and development since the previous major disaster in 1951, thus increasing the toll of casualties. Since the 17th century, at least two large-magnitude debris flow, landslide, or flood events, on average, have occurred each century within the boundaries of Vargas State. Recorded events occurred in February 1798, August 1912, January 1914, November 1938, May 1944, November 1944, August 1948, the deposits preserved on the alluvial fan deltas here show that these events occurred back through prehistoric times. In the February 1798 event, flash floods and debris flows severely damaged 219 homes, spanish soldiers barricaded an upstream-facing entrance to a fort with cannons in order to prevent debris from filling it. Based on aerial photos and records of measurements, geologists were able to compare the 1951 event to the 1999 event. The 1951 event involved less rainfall than the 1999 event, fewer landslides were triggered, as such, many of them have been extensively developed and urbanized. This high population density increases the risk to life and property from flash flood, as of 1999, several hundred thousand people lived in this narrow coastal strip in Vargas state. Many of these people lived atop alluvial fans formed by debris flows sourced out of the 2, December 1999 was unusually wet along the north-central Venezuelan coast. The first, and less powerful, storm that December occurred on the 2nd and 3rd, and dropped 200 mm of rain on the coast. In a 52-hour span during 14,15 and 16 December 1999,91.1 centimeters of rain was measured on the north-central coast of Venezuela at Simón Bolívar International Airport in Maiquetia, Venezuela. These heavy rains included 7.2 centimeters of accumulation in just one hour, even so, the coast received much less rain than some regions upstream. This sudden and intense storm was unusual because it occurred in December. These out-of-season rains formed when a cold front interacted with a moist southwesterly flow in the Pacific Ocean and this interaction produced moderate to heavy rainfall starting in the first week of December and culminating in the 14–16 December event that caused the deadly floods and debris flows. The heaviest rains were centered around the part of the San Julián basin. Heavy rains persisted within 8 kilometers of the coast, and subsided on the Caracas side of the Cerro El Ávila, rainfall rates also decreased westward toward Maiquetia
23.
Emergency evacuation
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Emergency evacuation is the urgent immediate egress or escape of people away from an area that contains an imminent threat, an on-going threat or a hazard to lives or property. Examples range from the small scale evacuation of a due to a storm or fire to the large scale evacuation of a city because of a flood. In situations involving hazardous materials or possible contamination, evacuees may be decontaminated prior to being transported out of the contaminated area, a benchmark evacuation time for different hazards and conditions is established. These benchmarks can be established through using best practices, regulations, or using simulations, such as modeling the flow of people in a building, proper planning will use multiple exits, contra-flow lanes, and special technologies to ensure full, fast and complete evacuation. Regulations such as building codes can be used to reduce the possibility of panic by allowing individuals to process the need to self-evacuate without causing alarm, proper planning will implement an all-hazards approach so that plans can be reused for multiple hazards that could exist. The particular phases are different for different objects, e. g. for ships a distinction between assembly and embarkation is made and these are separate from each other. The decision whether to enter the boats or rafts is thus usually made after assembly is completed, the strategy of individuals in evacuating buildings was investigated by John Abrahams in 1994. The independent variables were the complexity of the building and the movement ability of the individuals, with increasing complexity and decreasing motion ability, the strategy changes from fast egress, through slow egress and move to safe place inside building, to stay in place and wait for help. The last strategy is the notion of using a designated Safe Haven on the floor and this is a section of the building that is reinforced to protect against specific hazards, such as fire, smoke or structural collapse. Some hazards may have Safe Havens on each floor, while a hazard such as a tornado, typically persons with limited mobility are requested to report to a Safe Haven for rescue by first responders. In most buildings, the Safe Haven will be in the stairwell, the most common equipment in buildings to facilitate emergency evacuations are fire alarms, exit signs, and emergency lights. Some structures need special emergency exits or fire escapes to ensure the availability of alternative escape paths, commercial passenger vehicles such as buses, boats, and aircraft also often have evacuation lighting and signage, and in some cases windows or extra doors that function as emergency exits. Commercial emergency aircraft evacuation is also facilitated by evacuation slides and pre-flight safety briefings, military aircraft are often equipped with ejection seats or parachutes. Water vessels and commercial aircraft fly over water are equipped with personal flotation devices. The evacuation of districts is part of disaster management, many of the largest evacuations have been in the face of war-time military attacks. Modern large scale evacuations are usually the result of natural disasters, the largest peace-time evacuations in the United States to date occurred during Hurricane Gustav and the category-5 Hurricane Rita in a scare one month after the flood-deaths of Hurricane Katrina. Despite mandatory evacuation orders, many people did not leave New Orleans, United States, even after the city was flooded and uninhabitable, some people still refused to leave their homes. The longer a person has lived in an area, the less likely they are to evacuate
24.
Landslide
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A landslide, also known as a landslip, is a form of mass wasting that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. Landslides can occur underwater, called a submarine landslide, coastal, although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the prone to failure. Landslides occur when the changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, slope material that becomes saturated with water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses and cars, debris flow is often mistaken for flash flood, but they are entirely different processes. Muddy-debris flows in alpine areas cause severe damage to structures and infrastructure, muddy-debris flows can start as a result of slope-related factors and shallow landslides can dam stream beds, resulting in temporary water blockage. As the impoundments fail, an effect may be created, with a remarkable growth in the volume of the flowing mass. The solid–liquid mixture can reach densities of up to 2,000 kg/m3, for a small basin in the Italian Alps affected by a debris flow, estimated a peak discharge of 750 m3/s for a section located in the middle stretch of the main channel. At the same section, the maximum foreseeable water discharge, was 19 m3/s. Earthflows are downslope, viscous flows of saturated, fine-grained materials, typically, they can move at speeds from 0.17 to 20 km/h. Though these are a lot like mudflows, overall they are slow moving and are covered with solid material carried along by flow from within. They are different from fluid flows which are more rapid, clay, fine sand and silt, and fine-grained, pyroclastic material are all susceptible to earthflows. The velocity of the earthflow is all dependent on how much content is in the flow itself, if there is more water content in the flow. This thereby creates a bulging lobe which advances with a slow, as these lobes spread out, drainage of the mass increases and the margins dry out, thereby lowering the overall velocity of the flow. This process causes the flow to thicken, the bulbous variety of earthflows are not that spectacular, but they are much more common than their rapid counterparts. They develop a sag at their heads and are derived from the slumping at the source. Earthflows occur much more during periods of precipitation, which saturates the ground
25.
Landslide classification
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There have been known various classifications of landslides and other types of mass wasting. These systems are based on specific characteristics like shape of organs or nature of reproduction, for this reason, landslide classifications are based on different discriminating factors, sometimes very subjective. The second one is formed by those factors that have been utilised in some classifications and this is the most important criterion, even if uncertainties and difficulties can arise in the identification of movements, being the mechanisms of some landslides often particularly complex. The main movements are falls, slides and flows, but usually topples, lateral spreading, Rock, earth and debris are the terms generally used to distinguish the materials involved in the landslide process. For example, the distinction between earth and debris is made by comparing the percentage of coarse grain size fractions. If the weight of the particles with a greater than 2 mm is less than 20%. The classification of a landslide based on its activity is particularly relevant in the evaluation of future events, the recommendations of the WP/WLI define the concept of activity with reference to the spatial and temporal conditions, defining the state, the distribution and the style. This factor has an importance in the hazard evaluation. A velocity range is connected to the different type of landslides, Landslide dating is an interesting topic in the evaluation of hazard. The knowledge of the Landslide frequency is an element for any kind of probabilistic evaluation. Furthermore, the evaluation of the age of the permits to correlate the trigger to specific conditions. It is possible that phenomena could be occurred in past geological times, for example, in some Alpine areas, landslides of the Pleistocene age are connected with particular tectonic, geomorphological and climatic conditions. This represent a factor of the morphological evolution of a slope. Bedding attitude and the presence of discontinuities or faults control the slope morphogenesis, as the landslide is a geological volume with a hidden side, morphological characteristics are extremely important in the reconstruction of the technical model. This criterion describes, in a way, the location of landsides in the physiographic context of the area. As a consequence, specific morphological contexts are referred characterised by slope evolution processes, with these criteria, landslides can be identified with a system similar to that of the denomination of formations. Consequently, it is possible to describe a landslide using the name of a site, in particular, the name will be that of the locality where the landslide happened with a specific characteristic type. As a consequence, in the description of a landslide, it can be interesting to understand in what type of climate the event occurred, in the evaluation of landslide susceptibility, causes of the triggers is an important step
26.
1980 eruption of Mount St. Helens
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On May 18,1980, a major volcanic eruption occurred at Mount St. Helens, a volcano located in Skamania County, in the state of Washington, United States. The eruption was the significant volcanic eruption to occur in the contiguous 48 U. S. states since the 1915 eruption of Lassen Peak in California. However, it has often declared as the most disastrous volcanic eruption in United States history. An earthquake at 8,32,17 a. m. PDT on Sunday, May 18,1980, caused the entire weakened north face to slide away, creating the largest landslide ever recorded. An eruption column rose 80,000 feet into the atmosphere, at the same time, snow, ice and several entire glaciers on the volcano melted, forming a series of large lahars that reached as far as the Columbia River, nearly 50 miles to the southwest. Less severe outbursts continued into the day, only to be followed by other large. Approximately fifty-seven people were killed directly, including innkeeper Harry R. Truman, photographer Reid Blackburn and geologist David A. Johnston. Hundreds of square miles were reduced to wasteland, causing over a billion U. S. dollars in damage, thousands of animals were killed. At the time of the eruption, the summit of the volcano was owned by the Burlington Northern Railroad, the area was later preserved, as it was, in the Mount St. Helens National Volcanic Monument. Mount St. Helens remained dormant from its last period of activity in the 1840s and 1850s until March 1980, several small earthquakes, apparently beginning on March 15, indicated that magma may have begun moving below the volcano. Then on March 20, at 3,45 p. m. Pacific Standard Time, a total of 174 shocks of magnitude 2.6 or greater were recorded during those two days. Initially there was no sign of eruption, but small earthquake-induced avalanches of snow. At 12,36 p. m. on March 27, phreatic eruptions ejected and smashed rock from within the old crater, excavating a new crater 250 feet wide. By this date a 16, 000-foot long eastward-trending fracture system had developed across the summit area. This was followed by more earthquake swarms and a series of explosions that sent ash 10,000 to 11,000 feet above their vent. Most of this ash fell between 3 and 12 miles from its vent, but some was carried 150 miles south to Bend, Oregon, or 285 miles east to Spokane, a second, new crater and a blue flame were observed on March 29. The flame was visibly emitted from both craters and was created by burning gases. Static electricity generated from ash clouds rolling down the volcano sent out lightning bolts that were up to 2 miles long
27.
Mount St. Helens
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Mount St. Helens or Louwala-Clough is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 96 miles south of Seattle, Washington, and 50 miles northeast of Portland, Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc and this volcano is well known for its ash explosions and pyroclastic flows. Mount St. Helens is most notorious for its major 1980 eruption, fifty-seven people were killed,250 homes,47 bridges,15 miles of railways, and 185 miles of highway were destroyed. The debris avalanche was up to 0.7 cubic miles in volume, the Mount St. Helens National Volcanic Monument was created to preserve the volcano and allow for its aftermath to be scientifically studied. As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, the mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the domes formed the previous summit. Both were destroyed in the 1980 eruption, Mount St. Helens is 34 miles west of Mount Adams, in the western part of the Cascade Range. These sister and brother volcanic mountains are approximately 50 miles from Mount Rainier, Mount Hood, the nearest major volcanic peak in Oregon, is 60 miles southeast of Mount St. Helens. Mount St. Helens is geologically young compared with the other major Cascade volcanoes and it formed only within the past 40,000 years, and the pre-1980 summit cone began rising about 2,200 years ago. The volcano is considered the most active in the Cascades within the Holocene epoch, prior to the 1980 eruption, Mount St. Helens was the fifth-highest peak in Washington. It stood out prominently from surrounding hills because of the symmetry and extensive snow and ice cover of the summit cone. The peak rose more than 5,000 feet above its base, the mountain is 6 miles across at its base, which is at an elevation of 4,400 feet on the northeastern side and 4,000 feet elsewhere. At the pre-eruption tree line, the width of the cone was 4 miles. Streams that originate on the volcano enter three main systems, the Toutle River on the north and northwest, the Kalama River on the west. The streams are fed by abundant rain and snow, the average annual rainfall is 140 inches, and the snow pack on the mountains upper slopes can reach 16 feet. The Lewis River is impounded by three dams for power generation. The southern and eastern sides of the drain into an upstream impoundment, the Swift Reservoir
28.
Washington (state)
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It was admitted to the Union as the 42nd state in 1889. Washington is sometimes referred to as Washington State or the State of Washington to distinguish it from Washington, Washington is the 18th largest state with an area of 71,362 square miles, and the 13th most populous state with over 7 million people. Washington is the second most populous state on the West Coast and in the Western United States, Mount Rainier, an active stratovolcano, is the states highest elevation at almost 14,411 feet and is the most topographically prominent mountain in the contiguous United States. Washington is a leading lumber producer and its rugged surface is rich in stands of Douglas fir, hemlock, ponderosa pine, white pine, spruce, larch, and cedar. Manufacturing industries in Washington include aircraft and missiles, shipbuilding and other equipment, lumber, food processing, metals and metal products, chemicals. Washington has over 1,000 dams, including the Grand Coulee Dam, built for a variety of purposes including irrigation, power, flood control, the Washington Territory was named after George Washington, the first President of the United States. The area was part of a region called the Columbia District after the Columbia River. The area was renamed Washington in order to avoid confusion with the District of Columbia, Washington is the only U. S. state named after a president. To distinguish it from the U. S. capital, which is named for George Washington, Washington is sometimes referred to as Washington State, or, in more formal contexts. Washingtonians and other residents of the Pacific Northwest refer to the state simply as Washington, calling the nations capital Washington, D. C. or, often, Washington is the northwestern-most state of the contiguous United States. Washington is bordered by Oregon to the south, with the Columbia River forming the western part, to the west of Washington lies the Pacific Ocean. The high mountains of the Cascade Range run north-south, bisecting the state, from the Cascade Mountains westward, Western Washington has a mostly marine west coast climate, with mild temperatures and wet winters, autumns and springs, and relatively dry summers. The Cascade Range contains several volcanoes, which reach altitudes significantly higher than the rest of the mountains, from the north to the south, these major volcanoes are Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams. Mount Rainier, the tallest mountain in the state, is 50 miles south of the city of Seattle and it is also covered with more glacial ice than any other peak in the contiguous 48 states. Western Washington also is home of the Olympic Mountains, far west on the Olympic Peninsula and these deep forests, such as the Hoh Rainforest, are among the only temperate rainforests in the continental United States. Eastern Washington – the part of the state east of the Cascades – has a dry climate. It includes large areas of steppe and a few truly arid deserts lying in the rain shadow of the Cascades. Farther east, the climate becomes less arid, with annual rainfall increasing as one goes east to 21.2 inches in Pullman, the Okanogan Highlands and the rugged Kettle River Range and Selkirk Mountains cover much of the northeastern quadrant of the state
29.
Spirit Lake (Washington)
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Spirit Lake is a lake north of Mount St. Helens in Washington State. The lake was a popular tourist destination for years until the 1980 eruption of Mount St. Helens. Prior to 1980, there were six camps on the shore of Spirit Lake, a Boy Scout camp, a Girl Scout camp, two YMCA camps, Harmony Fall Lodge, and another for the general public. There were also a number of catering to visitors, including Spirit Lake Lodge and Mt. St. Helens Lodge, the latter was inhabited by Harry R. Truman. Prior to 1980, Spirit Lake consisted of two arms that occupied what had been the valleys of the North Fork Toutle River and a tributary. About 4,000 years ago, these valleys were blocked by lahars, the longest branch of Spirit Lake was about 2.1 miles long. A stable outlet channel flowed from the lake to the North Fork Toutle River across a dam composed of volcanic material. Recent climate data for the area is not available to confirm whether the site still has this rare climate type. During the 1980 eruption of Mount St. Helens, Spirit Lake received the full impact of the lateral blast from it. The debris avalanche deposited about 350,000 acre-feet of pyrolized trees, other plant material, volcanic ash, the deposition of this volcanic material decreased the lake volume by approximately 46,000 acre-feet. The surface area of the lake was increased from 1,300 acres to about 2,200 acres, the eruption tore thousands of trees from the surrounding hillsides and swept them into Spirit Lake. These thousands of shattered trees formed a log raft on the lake surface that covered about 40% of the lake’s surface after the eruption. After the eruption, Spirit Lake contained highly toxic water with volcanic gases seeping up from the lake bed, a month after the eruption, the bacteria-carrying water was devoid of oxygen. Scientists predicted that the lake would not recover quickly, but the reemergence of phytoplankton starting in 1983 began to restore oxygen levels, amphibians such as frogs and salamanders recolonized the lake, and fish thrived. The water level of Spirit Lake is maintained at about 3,406 ft by draining water through a tunnel completed in 1985. The 8,465 ft -long tunnel was cut through Harrys Ridge to South Coldwater Creek, anonymous, CVO Photo Archives, Hydrology and Hydrologic Monitoring Images. Cascades Volcano Observatory, United State Geological Survey, Vancouver, Washington, glicken, HX, W Meyer, and MA Sabol, Geology and ground-water hydrology of Spirit Lake blockage, Mount St. Helens, Washington, with implications for lake retention. Evarts, RC, and RP Ashley Geologic map of the Spirit Lake East quadrangle, Skamania County,1679, U. S. Geological Survey, Reston, Virginia
30.
Iran
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Iran, also known as Persia, officially the Islamic Republic of Iran, is a sovereign state in Western Asia. Comprising a land area of 1,648,195 km2, it is the second-largest country in the Middle East, with 82.8 million inhabitants, Iran is the worlds 17th-most-populous country. It is the country with both a Caspian Sea and an Indian Ocean coastline. The countrys central location in Eurasia and Western Asia, and its proximity to the Strait of Hormuz, Tehran is the countrys capital and largest city, as well as its leading economic and cultural center. Iran is the site of to one of the worlds oldest civilizations, the area was first unified by the Iranian Medes in 625 BC, who became the dominant cultural and political power in the region. The empire collapsed in 330 BC following the conquests of Alexander the Great, under the Sassanid Dynasty, Iran again became one of the leading powers in the world for the next four centuries. Beginning in 633 AD, Arabs conquered Iran and largely displaced the indigenous faiths of Manichaeism and Zoroastrianism by Islam, Iran became a major contributor to the Islamic Golden Age that followed, producing many influential scientists, scholars, artists, and thinkers. During the 18th century, Iran reached its greatest territorial extent since the Sassanid Empire, through the late 18th and 19th centuries, a series of conflicts with Russia led to significant territorial losses and the erosion of sovereignty. Popular unrest culminated in the Persian Constitutional Revolution of 1906, which established a monarchy and the countrys first legislative body. Following a coup instigated by the U. K. Growing dissent against foreign influence and political repression led to the 1979 Revolution, Irans rich cultural legacy is reflected in part by its 21 UNESCO World Heritage Sites, the third-largest number in Asia and 11th-largest in the world. Iran is a member of the UN, ECO, NAM, OIC. Its political system is based on the 1979 Constitution which combines elements of a democracy with a theocracy governed by Islamic jurists under the concept of a Supreme Leadership. A multicultural country comprising numerous ethnic and linguistic groups, most inhabitants are Shia Muslims, the largest ethnic groups in Iran are the Persians, Azeris, Kurds and Lurs. Historically, Iran has been referred to as Persia by the West, due mainly to the writings of Greek historians who called Iran Persis, meaning land of the Persians. As the most extensive interactions the Ancient Greeks had with any outsider was with the Persians, however, Persis was originally referred to a region settled by Persians in the west shore of Lake Urmia, in the 9th century BC. The settlement was then shifted to the end of the Zagros Mountains. In 1935, Reza Shah requested the international community to refer to the country by its native name, opposition to the name change led to the reversal of the decision, and Professor Ehsan Yarshater, editor of Encyclopædia Iranica, propagated a move to use Persia and Iran interchangeably
31.
Kabir Kuh
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Kabir Kuh is one of the long ranges of the Zagros Mountains near the border of Lurestan and Ilam Provinces in Ilam province, Iran. Covering an area of 9,500 km2, Kabir Kuh stretches 175 km in length and it begins about 20 km south of Ilam and stretches down to the vicinity of Andimeshk in Khuzestan. Its highest peak is Kan Seifi with 3,050 m elevation,50 km south of Ilam, Kabir Kuh runs along the Seymareh river, which becomes Karkheh when joins the Kashkan river before reaching the border of Ilam province and Khuzestan province. Kabir Kuh divides the region in western Iran into two regions generally referred as Piškuh and Poštkuh, the latter virtually coinciding with Ilam. The eastern side is dominated by steep slopes where water and wooded valleys abound, the western side is, however, quite dry but rich in oil reservoirs and underground resources
32.
Anticline
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In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core. A typical anticline is convex up in which the hinge or crest is the location where the curvature is greatest, anticlines can be recognized and differentiated from antiforms by a sequence of rock layers that become progressively older toward the center of the fold. Therefore, if age relationships between various rock strata are unknown, the term antiform should be used, the progressing age of the rock strata towards the core and uplifted center, are the trademark indications for evidence of anticlines on a geologic map. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations, the uplifted core of the fold causes compression of strata that preferentially erodes to a deeper stratigraphic level relative to the topographically lower flanks. Motion along the fault including both shortening and extension of tectonic plates, usually also deforms strata near the fault and this can result in an asymmetrical or overturned fold. An antiform can be used to describe any fold that is convex up and it is the relative ages of the rock strata that separate anticlines from antiforms. The hinge of an anticline refers to the location where the curvature is greatest, the hinge is also the highest point on a stratum along the top of the fold. The culmination also refers to the highest point along any geologic structure, the limbs are the sides of the fold that display less curvature. The inflection point is the area on the limbs where the curvature changes direction, the axial surface is an imaginary plane connecting the hinge of each layer of rock stratum through the cross section of an anticline. If the axial surface is vertical and the angles on each side of the fold are equivalent, if the axial plane is tilted or offset then the anticline is asymmetrical. An anticline that is cylindrical has a well-defined axial surface, whereas non-cylindrical anticlines are too complex to have an axial plane. If the angle between the limbs is large, then the fold is a fold, but if the angle between the limbs is small, then the fold is a tight fold. If an anticline plunges, it will form Vs on a map view that point in the direction of plunge. A plunging anticline has a hinge that is not parallel to the earths surface, all anticlines and synclines have some degree of plunge. Periclinal folds are a type of anticlines that have a well-defined, folds in which the limbs dip toward the hinge and display a more U-like shape are called synclines. They usually flank the sides of anticlines and display opposite characteristics, a synclines oldest rock strata are in its outer limbs, the rocks become progressively younger toward its hinge. A monocline is a bend in the resulting in a local steepening in only one direction of dip. Monoclines have the shape of a carpet draped over a stairstep, an anticline that has been more deeply eroded in the center is called a breached or scalped anticline
33.
Submarine landslide
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Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. Submarine landslides take place in a variety of different settings including planes as low as 1°, recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology. Submarine Landslides have different causes which relate to both the attributes of the landslide material and transient environmental factors affecting the submarine environment. The presence of weak geological layers is a factor which contributes to submarine landslides at all scales and this has been confirmed by seafloor imaging such as swath bathymetric mapping and 3D seismic reflection data. An example of a slide which was caused by weak geological layers is the Storegga slide, overpressure due to rapid deposition of sediment is closely related to weak geological layers. An example of landslides caused by due to rapid deposition occurred in 1969 on the Mississippi delta after Hurricane Camile struck the region. Earthquakes are a key factor which trigger most major submarine landslides, earthquakes provide significant environmental stresses and can promote elevated pore water pressure which leads to failure. Earthquakes triggered the Grand Banks landslide of 1929, where a 20 km3 submarine landslide was initiated after an earthquake, a number of studies have indicated that gas hydrates lie beneath many submarine slopes and can contribute to the triggering of a landslide. Gas hydrates are ice like substances consisting of water and natural gas, when the temperature rises or the pressure drops the gas hydrate becomes unstable allowing some of the hydrate to dissociate and discharge bubble phase natural gas. If pore water flow is impeded then this gas charging leads to excess water pressure. Gas hydrate dissociation is thought to have contributed to slides at water depths of 1000 to 1300 m off the east coast of the United States, groundwater seepage and elevated pore water pressure can cause submarine landslides. An example where glacial loading lead to submarine landsliding is the Nyk slide of northern Norway, slope failures due to volcanic island growth are among the largest on earth, involving volumes of several cubic kilometres. The failure occurs as large bodies of lava form above weak marine sediments which are prone to failure, failure is particularly common on edifices which are over 2500 m but rare on edifices which are less than 2500 m. Volcanic island submarine landslides occur in such as the Hawaiian Islands. Oversteepening is caused by scouring due to currents and can result in the triggering of submarine landslides. In some cases the relationship between the cause and the landslide can be quite clear while in other cases the relationships may not be so obvious. In most cases more than one factor may contribute towards the initiation of a landslide event and this is clearly seen on the Norwegian continental slope where the location of landslides such as Storegga and Traenadjupet is related to weak geological layers. Even when considering all the listed factors, in the end it was calculated that the landslide needed an earthquake for it to ultimately be initiated
34.
Natural disaster
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An adverse event will not rise to the level of a disaster if it occurs in an area without vulnerable population. In a vulnerable area, however, such as Nepal during the 2015 earthquake, a landslide is described as an outward and downward slope movement of an abundance of slope-forming materials including rock, soil, artificial, or even a combination of these things. During World War I, an estimated 40,000 to 80,000 soldiers died as a result of avalanches during the campaign in the Alps at the Austrian-Italian front. Many of the avalanches were caused by artillery fire, an earthquake is the result of a sudden release of energy in the Earths crust that creates seismic waves. At the Earths surface earthquakes manifest themselves by vibration, shaking, earthquakes are caused by slippage within geological faults. The underground point of origin of the earthquake is called the seismic focus, the point directly above the focus on the surface is called the epicenter. Earthquakes by themselves rarely kill people or wildlife and it is usually the secondary events that they trigger such as building collapse, fires, tsunamis and volcanoes. Many of these could possibly be avoided by better construction, safety systems, when natural erosion or human mining makes the ground too weak to support the structures built on it, the ground can collapse and produce a sinkhole. Volcanoes can cause destruction and consequent disaster in several ways. The effects include the eruption itself that may cause harm following the explosion of the volcano or falling rocks. Second, lava may be produced during the eruption of a volcano, third, volcanic ash generally meaning the cooled ash – may form a cloud, and settle thickly in nearby locations. When mixed with water forms a concrete-like material. In sufficient quantity ash may cause roofs to collapse under its weight, since the ash has the consistency of ground glass it causes abrasion damage to moving parts such as engines. It is believed that Pompeii was destroyed by a pyroclastic flow, a lahar is a volcanic mudflow or landslide. The 1953 Tangiwai disaster was caused by a lahar, as was the 1985 Armero tragedy in which the town of Armero was buried, a specific type of volcano is the supervolcano. It also killed three-quarters of all plant life in the northern hemisphere, the main danger from a supervolcano is the immense cloud of ash, which has a disastrous global effect on climate and temperature for many years. It is a violent, sudden and destructive change either in quality of water or in distribution or movement of water on land below the surface or in atmosphere. A flood is an overflow of water that submerges land, the EU Floods Directive defines a flood as a temporary covering by water of land which is usually not covered by water
35.
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
36.
Ice calving
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Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption and is caused by the glacier expanding. It is the release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf. The ice that breaks away can be classified as an iceberg, calving of glaciers is often accompanied by a loud cracking or booming sound before blocks of ice up to 60 metres high break loose and crash into the water. The entry of the ice into the water causes large, the waves formed in locations like Johns Hopkins Glacier can be so large that boats cannot approach closer than 3 kilometres. These events have become major tourist attractions in such as Alaska. Many glaciers terminate at oceans or freshwater lakes which results naturally with the calving of large numbers of icebergs, calving of Greenlands glaciers produce 12,000 to 15,000 icebergs each year alone. Calving of ice shelves is usually preceded by a rift and these events are not often observed. Etymologically, calving is cognatic with calving as in bearing a calf and it is useful to classify causes of calving into first, second, and third order processes. First order processes are responsible for the rate of calving at the glacier scale. The first order cause of calving is longitudinal stretching, which controls the formation of crevasses, when crevasses penetrate the full thickness of the ice, calving will occur. Longitudinal stretching is controlled by friction at the base and edges of the glacier, glacier geometry and these factors, therefore, exert the primary control on calving rate. Second and third order calving processes can be considered to be superimposed on the first order process above, melting at the waterline is an important second order calving process as it undercuts the subaerial ice, leading to collapse. Other second order processes include tidal and seismic events, buoyant forces, when calving occurs due to waterline melting, only the subaerial part of the glacier will calve, leaving a submerged foot. Thus, a third order process is defined, whereby upward buoyant forces cause this ice foot to break off and this process is extremely dangerous, as it has been known to occur, without warning, up to 300m from the glacier terminus. Though many factors contribute to calving have been identified, a reliable predictive mathematical formula is still under development. Data is currently being assembled from ice shelves in Antarctica and Greenland to help establish a calving law, there are currently several concepts upon which to base a predictive law. Another theory, based on research, shows that the calving rate increases as a power of the spreading rate near the calving front
37.
Volcano
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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, therefore, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
38.
Sinkhole
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A sinkhole, also known as a cenote, sink, sink-hole, shakehole, swallet, swallow hole, or doline, is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes—for example, the dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms, sinkholes may form gradually or suddenly, and are found worldwide. Sinkholes may capture surface drainage from running or standing water, but may form in high. Sinkholes that capture drainage can hold it in limestone caves. These caves may drain into tributaries of larger rivers, the formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion, for example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void. Occasionally a sinkhole may exhibit a visible opening into a cave below, sinkholes also occur in sandstone and quartzite terrains. As the rock dissolves, spaces and caverns develop underground and these sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a collapse of the land surface can occur. Sinkholes also form from human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places like Louisiana, Mississippi, more commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater, sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Sinkholes tend to occur in karst landscapes, karst landscapes can have up to thousands of sinkholes within a small area, giving the landscape a pock-marked appearance. These sinkholes drain all the water, so there are only subterranean rivers in these areas, examples of karst landscapes with a plethora of massive sinkholes include Khammouan Mountains and Mamo Plateau. The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in Venezuela, some sinkholes form in thick layers of homogenous limestone. On the contact of limestone and insoluble rock below it, powerful underground rivers may form, in such conditions, the largest known sinkholes of the world have formed, like the 662-metre deep Xiaozhai Tiankeng, giant sótanos in Querétaro and San Luis Potosí states in Mexico and others. The state of Florida in the United States is known for having frequent sinkhole collapses, the Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain, an analysis of a case of sinkhole formation under a retention pond due to a large amount of rain can be seen in a sinkhole collapse study
39.
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
40.
Coastal flood
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Coastal flooding occurs when normally dry, low-lying land is flooded by seawater. The extent of flooding is a function of the elevation inland flood waters penetrate which is controlled by the topography of the coastal land exposed to flooding. The height of the waves exceeds the height of the barrier and water flows over the top of the barrier to flood the land behind it, overtopping can result in high velocity flows that can erode significant amounts of the land surface which can undermine defense structures. Breaching of a barrier — again the barrier may be natural or human engineered, breaching is where the barrier is broken down by waves allowing the seawater to extend inland. Coastal flooding is largely a natural event, however human influence on the environment can exacerbate coastal flooding. Extraction of water from reservoirs in the coastal zone can enhance subsidence of the land increasing the risk of flooding. Coastal flooding can result from a variety of different causes including storm surges created by storms like hurricanes and tropical cyclones, rising sea levels due to climate change and by tsunamis. Storms can cause flooding through storm surges which are significantly larger than normal. This is known as set up. Low atmospheric pressure is associated with systems and this tends to increase the surface sea level. Finally increased wave break height results in a water level in the surf zone which is wave set up. Theses three processes interact to create waves that can overtop natural and engineered coastal protection structures thus penetrating seawater further inland than normal, the Intergovernmental Panel on Climate Change estimate global mean sea-level rise from 1990 to 2100 to be between nine and eighty eight centimetres. It is also predicted that climate change there will be an increase in the intensity. This suggests that coastal flooding from storm surges will become more frequent with sea level rise, a rise in sea level alone threatens increased levels of flooding and permanent inundation of low-lying land as sea level simply may exceed the land elevation. There is also evidence to suggest that significant tsunami have been caused in the past by meteor impact into the ocean and it has been said that one way to prevent significant flooding of coastal areas now and into the future is by reducing global sea level rise. This could be minimised by reducing greenhouse gas emissions. However, even if significant emission decreases are achieved there is already a substantial commitment to sea level rise into the future, international climate change policies such as the Kyoto Protocol are seeking to mitigate the future effects of climate change, including sea level rise. In addition to this, more immediate measures of engineered and natural defences are put in place to prevent coastal flooding, there are a variety of ways in which humans are trying to prevent the flooding of coastal environments
41.
Flash flood
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A flash flood is a rapid flooding of geomorphic low-lying areas, washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a thunderstorm, hurricane, tropical storm. Flash floods may occur after the collapse of an ice or debris dam, or a human structure such as a man-made dam. Flash floods are distinguished from regular floods by a timescale of less than six hours, the water that is temporarily available is often used by foliage with rapid germination and short growth cycles, and by specially adapted animal life. Flash floods can occur under several types of conditions, Flash flooding occurs when it rains rapidly on saturated soil or dry soil that has poor absorption ability. The runoff collects in gullies and streams and, as they join to form larger volumes, often forms a fast flowing front of water, in areas on or near volcanoes, flash floods have also occurred after eruptions, when glaciers have been melted by the intense heat. Flash floods are known to occur in the highest mountain ranges of the United States and are common in the arid plains of the Southwestern United States. Flash flooding can also be caused by extensive rainfall released by hurricanes and other tropical storms, human activities can also cause flash floods to occur. When dams fail, a quantity of water can be released. Many people tend to underestimate the dangers of flash floods, what makes flash floods most dangerous is their sudden nature and fast-moving water. A vehicle provides little to no protection against being swept away, it may make people overconfident, more than half of the fatalities attributed to flash floods are people swept away in vehicles when trying to cross flooded intersections. As little as 2 feet of water is enough to carry away most SUV-sized vehicles. The U. S. National Weather Service reported in 2005 that, using a national 30-year average, more people die yearly in floods,127 on average, than by lightning, tornadoes, in deserts, flash floods can be particularly deadly for several reasons. First, storms in arid regions are infrequent, but they can deliver an enormous amount of water in a short time. Second, these rains often fall on poorly absorbent and often clay-like soil, in fact, in some areas, desert roads frequently cross dry river and creek beds without bridges. From the drivers perspective, there may be clear weather, when a river unexpectedly forms ahead of or around the vehicle in a matter of seconds. Finally, the lack of rain to clear water channels may cause flash floods in deserts to be headed by large amounts of debris, such as rocks, branches. 1889, Johnstown Flood, Pennsylvania, U. S. more than 2,200 people dead 1903, Heppner Flood of 1903, Oregon, United States,247 dead, 25% of the city 1938, Los Angeles Flood of 1938, California, U. S. S
42.
Storm surge
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Most casualties during tropical cyclones occur as the result of storm surges. The deadliest storm surge on record was the 1970 Bhola cyclone, the low-lying coast of the Bay of Bengal is particularly vulnerable to surges caused by tropical cyclones. The deadliest storm surge in the twenty-first century was caused by the Cyclone Nargis, the next deadliest in this century was caused by the Typhoon Haiyan, which killed more than 6,000 people in the central Philippines in 2013 and resulted in economic losses estimated at $14 billion. Louis, Diamondhead and Pass Christian in Mississippi, a high storm surge occurred in New York City from Hurricane Sandy in October 2012, with a high tide of 14 ft. The pressure effects of a tropical cyclone will cause the level in the open ocean to rise in regions of low atmospheric pressure. The rising water level will counteract the low pressure such that the total pressure at some plane beneath the water surface remains constant. This effect is estimated at a 10 mm increase in sea level for every millibar drop in atmospheric pressure, strong surface winds cause surface currents at a 45° angle to the wind direction, by an effect known as the Ekman Spiral. Wind stresses cause a phenomenon referred to as wind set-up, which is the tendency for water levels to increase at the downwind shore, intuitively, this is caused by the storm simply blowing the water towards one side of the basin in the direction of its winds. Because the Ekman Spiral effects spread vertically through the water, the effect is proportional to depth. The pressure effect and the wind set-up on an open coast will be driven into bays in the way as the astronomical tide. The Earths rotation causes the Coriolis effect, which bends currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. When this bend brings the currents into more contact with the shore it can amplify the surge. The effect of waves, while powered by the wind, is distinct from a storms wind-powered currents. Powerful wind whips up large, strong waves in the direction of its movement, although these surface waves are responsible for very little water transport in open water, they may be responsible for significant transport near the shore. When waves are breaking on a more or less parallel to the beach. The rainfall effect is experienced predominantly in estuaries, Hurricanes may dump as much as 12 in of rainfall in 24 hours over large areas, and higher rainfall densities in localized areas. As a result, watersheds can quickly surge water into the rivers that drain them and this can increase the water level near the head of tidal estuaries as storm-driven waters surging in from the ocean meet rainfall flowing from the estuary. This situation well exemplified by the southeast coast of Florida
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Limnic eruption
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Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon, Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes. To date, this phenomenon has been observed only twice, the first was in Cameroon at Lake Monoun in 1984, causing the asphyxiation and death of 38 people living nearby. Due to the nature of the event, it is hard to determine if limnic eruptions have happened elsewhere, a third lake, Lake Kivu, exists on the border between the Democratic Republic of the Congo and Rwanda, and contains massive amounts of dissolved CO2. Limnic eruptions can be measured on a scale using the concentration of CO2 in the surrounding area, the Messel pit fossil deposits of Messel, Germany, show evidence of a limnic eruption there in the early Eocene. Among the victims are perfectly preserved insects, frogs, turtles, crocodiles, birds, anteaters, insectivores, for a limnic eruption to occur, the lake must be nearly saturated with gas. In the two cases, the major component was CO2, however, in Lake Kivu, scientists are concerned about the concentrations of methane gas as well. This CO2 may come from volcanic gas emitted from under the lake or from decomposition of organic material, before a lake is saturated, it behaves like an unopened carbonated beverage, the CO2 is dissolved in the water. In both the lake and the drink, CO2 dissolves much more readily at higher pressure. This is why bubbles in a can of soda form only after the can is opened, the pressure is released, in the case of lakes, the bottom is at a much higher pressure, the deeper it is, the higher the pressure at the bottom. This means that huge amounts of CO2 can be dissolved in large, also, CO2 dissolves more readily in cooler water, such as that at the bottom of a lake. A small rise in temperature can lead to the release of a large amount of CO2. Once the lake is saturated with CO2, it is very unstable, a trigger is all that is needed to set off an eruption. In the case of the 1986 eruption at Lake Nyos, landslides were the triggers, but an actual volcanic eruption. Another possible cause of an eruption is the gradual development of saturation at certain depths which can trigger the spontaneous development of gas. In any case, the trigger pushes some of the water higher in the lake. Bubbles start forming and the water is lifted even higher in the lake and this process forms a column of gas. At this point the water at the bottom of this column is pulled up by suction and this eruption pours CO2 into the air and can also displace water to form a tsunami
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Tsunami
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A tsunami or tidal wave, also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Unlike normal ocean waves which are generated by wind, or tides which are generated by the pull of the Moon and Sun. Tsunami waves do not resemble normal undersea currents or sea waves, Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called internal wave train. Wave heights of tens of metres can be generated by large events, numerous terms are used in the English language to describe waves created in a body of water by the displacement of water, however, none of the terms in frequent use are entirely accurate. The term tsunami, meaning harbour wave in literal translation, comes from the Japanese 津波, while not entirely accurate, as tsunami are not restricted to harbours, tsunami is currently the term most widely accepted by geologists and oceanographers. Tsunami are sometimes referred to as tidal waves and this once-popular term derives from the most common appearance of tsunami, which is that of an extraordinarily high tidal bore. Although the meanings of tidal include resembling or having the form or character of the tides, use of the tidal wave is discouraged by geologists. The term seismic sea wave also is used to refer to the phenomenon, prior to the rise of the use of the term tsunami in English-speaking countries, scientists generally encouraged the use of the term seismic sea wave rather than tidal wave. The Sumatran region is not unused to tsunamis either, with earthquakes of varying magnitudes regularly occurring off the coast of the island, Tsunamis are an often underestimated hazard in the Mediterranean Sea and parts of Europe. The tsunami claimed more than 123,000 lives in Sicily, the Storegga Slide in the Norwegian sea and some examples of tsunamis affecting the British Isles refer to landslide and meteotsunamis predominantly and less to earthquake-induced waves. The cause, in my opinion, of this phenomenon must be sought in the earthquake, at the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen, the principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is attributed to either earthquakes, landslides, volcanic eruptions, glacier calvings or more rarely by meteorites. The waves formed in this way are then sustained by gravity, tides do not play any part in the generation of tsunamis. Tsunami can be generated when the sea floor abruptly deforms and vertically displaces the overlying water and they grow in height when they reach shallower water, in a wave shoaling process described below. A tsunami can occur in any state and even at low tide can still inundate coastal areas. On April 1,1946, the 8.6 Mw Aleutian Islands earthquake occurred with a maximum Mercalli intensity of VI and it generated a tsunami which inundated Hilo on the island of Hawaii with a 14-metre high surge. Between 165 and 173 were killed, the area where the earthquake occurred is where the Pacific Ocean floor is subducting under Alaska
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Meteotsunami
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A meteotsunami or meteorological tsunami is a tsunami-like wave of meteorological origin. Meteotsunamis are generated when rapid changes in barometric pressure cause the displacement of a body of water, in contrast to ordinary impulse-type tsunami sources, a traveling atmospheric disturbance normally interacts with the ocean over a limited period of time. Meteotsunamis are restricted to local effects because they lack the energy available to significant seismic tsunami, however, when they are amplified by resonance they can be hazardous. A meteotsunami that struck Nagasaki Bay on 31 March 1979 achieved a wave height of 5 meters. A three-meter wave that hit the Chicago waterfront in 1954 swept people off of piers, in some parts of the world, they are common enough to have local names, rissaga, ressaca, milghuba, marrobbio, abiki, šćiga. Examples of particularly susceptible areas include Nagasaki Bay, the eastern Adriatic Sea, historic tsunami Tsunami warning system Deep-ocean Assessment and Reporting of Tsunamis Undular bore Presentation on meteotsunamis by the Croatian Institute for Oceanography. Photos of the Rissaga in Spain 06-15-2006
