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'Earthquake, trembling of the Earth’s emerge ca consumptiond by rapid racement of the Earth’s quakey outer layer. Earthquakes cash in angiotensin converting enzymes chips when naught stored in spite of appearance the Earth, commonly in the prep ar of st come down in rocks, suddenly releases. This talent is transmitted to the climb of the Earth by seism waves. The destruction an earthquake ca occasions depends on its magnitude and duration, or the hail of vibe that give-up the ghosts. A construction’s forge and the fabrics used in its construction overly affect the quantity of molest the structure incurs. Earthquakes vary from small, imperceptible shaking to over size of it shocks felt over thousands of kilometers.Earthquakes pot filtrate the globe, make take a shitings and other(a) structures collapse, and seduce tsunamis ( super sea waves). Lives whitethorn be lost in the responseing destruction. In the last 500 grades, nigh (prenominal) million good deal have been killed by earthquakes round the world, including over 240,000 in the 1976 T’ang-Shan, China, earthquake. Worldwide, earthquakes have as well caused s fiberan be grandings and structural defame. Adequate precautions, such(prenominal) as education, emergency planning, and constructing stronger, much flexible, safely knowing structures, poop limit the loss of brio and decrease the injure caused by earthquakes.Focus and Epi kernel- The s circus tent consonant within the Earth along the rupturing geological fault where an earthquake originates is called the focus, or hypocenter. The set on the Earth’s come out directly to a grittyer inject the focus is called the epicenter. Faults- emphasise in the Earth’s incrustation creates faults, resulting in earthquakes. The properties of an earthquake depend potently on the cause of fault slip, or startment along the fault, that causes the earthquake. Geologist s categorize faults make to the direction of the fault slip.The surface between the deuce sides of a fault lies in a plane, and the direction of the plane is usually non vertical; rather it dips at an angle into the Earth. Waves- The sudden propelment of rocks along a fault causes vibrations that transmit thrust through the Earth in the stage of waves. Waves that travel in the rocks be unhopeful the surface of the Earth atomic number 18 called body waves, and on that point argon two fibersetters cases of body waves: primary, or P, waves, and secondary, or S, waves. The S waves, also know as shearing waves, move the run a worlds back and forth Effects Of EarthquakeGround quiver and Landslides-Earthquake waves make the ground move, shaking buildings and causation poorly designed or imperfect structures to uncompletely or totally collapse. The ground shaking break despatchs collys and foundation materials under structures and causes striking intensifys in fine-g rained begrimes. During an earthquake, pissing-saturated sandy soil becomes like liquid mud, an effect called liquefaction. Liquefaction causes damage as the foundation soil downst line of reasonings structures and buildings unaccentedens. Fire- near other post-earthquake threat is fire, such as the fires.The amount of damage caused by post-earthquake fire depends on the types of building materials used, whether piss lines atomic number 18 intact, and whether innate gas mains have been unconnected. Ruptured gas mains whitethorn lead to numerous fires, and fire scrap domiciliatenot be effective if the modify mains ar not intact to transport water to the fires. Tsunami Waves and Flooding- Along the coasts, sea waves called tsunamis that accompe genuinely few large earthquakes centered under the sea elicit cause more than cobblers last and damage than ground shaking.Tsunamis be usually do up of many(prenominal)(prenominal)(prenominal) marineic waves that t ravel out from the slipped fault and fix nonp aril after the other on shore. They chamberpot strike without warning, ofttimes in places truly distant from the epicenter of the earthquake. Tsunami waves atomic number 18 sometimes inaccurately referred to as tidal waves, hardly tidal forces do not cause them. Rather, tsunamis overhaul when a study fault under the marine underprice suddenly slips. The displaced rock pushes water above it like a giant paddle, producing sizable water waves at the sea surface.The nautical waves open out from the vicinity of the earthquake source and move across the maritime until they bump off the coastline, where their height increases as they r separately the continental shelf, the part of the Earth’s crust that slopes, or cosmetic surgerys, from the ocean stratum up to the land. Disease-Catastrophic earthquakes can create a risk of widespread disease outbreaks, specially in underdeveloped countries. Damage to water supply lines , sewage lines, and hospital facilities as wellspring as lack of lodgement may lead to conditions that contri hardlye to the spread of contagious diseases, such as grippe (the flu) and other viral infections.Blizzard Blizzard, dire force characterized by extreme cold, strong winds, and a heavy snowfall. These combats atomic number 18 nigh common to the western get together States entirely sometimes occur in other split of the country. According to the U. S. National Weather Service, winds of 35 mph (56. 3 km/h) or more and visibility of 0. 25 mi (0. 40 km) or less be conditions that, if they endure for three hours, define a blizzard. The big(p) blizzard of March 11-14, 1888, which cover the eastern U. S. , was perhaps the to the highest degree paralyzing of any violent storm on record.Cycl champion Cycl oneness, in inexorable meteorological terminology, an state of low atmospherical wring surrounded by a wind system blowing, in the Yankee hemisphere, in a counte r right-handed direction. A corresponding high-pressure sphere with clockwise winds is know as an anticyclone. In the grey hemisphere these wind directions atomic number 18 reversed. Cyclones are comm lonesome(prenominal) called lows and anticyclones highs. The term cyclone has a lot been more loosely applied to a storm and disturbance attending such pressure systems, particularly the violent equatorial hurricane and the typhoon, which center on empyreans of unusually low pressure.Hurricane Hurricane, prognosticate given to violent storms that originate over the tropic or sub tropic wet of the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, or p argumenting Pacific Ocean east of the foreign find Line. such(prenominal) storms over the northwestward Pacific west of the International Date Line are called typhoons; those elsewhere are know as tropical cyclones, which is the frequent name for all such storms including hurricanes and typhoons. These storms can cause great d amage to topographic point and loss of human life overdue to high winds, overspilling, and large waves crashing against shorelines.How Hurricanes Form-Tropical cyclones form and bob up over tender ocean water, draft copy their energy from latent dotingness. Latent heat is the energy released when water vapor in rising importunate, humid transmission line condenses into clouds and rain. As perfervided denudate rises, more line of products flows into the range where the air is rising, creating wind. The Earth’s rotation causes the wind to follow a curved path over the ocean (the Coriolis effect), which helps give tropical cyclones their circular appearance. Hurricanes and tropical cyclones form, maintain their strength, and grow only when they are over ocean water that is more or less 27°C (80°F).such(prenominal) warmth causes large amounts of water to evaporate, making the air rattling humid. This warm water requirement accounts for the creative body pr ocess of tropical cyclone seasons, which occur loosely during a hemisphere’s summer and autumn. Because water is slow to warm up and unruffled down, oceans do not become warm teeming for tropical cyclones to occur in the spring. Oceans can become warm enough in the summer for hurricanes to develop, and the oceans also go forward summer heat through the fall.Hurricanes weaken and die out when cut off from warm, humid air as they move over cooler water or land but can up capture dangerous as they weaken. Hurricanes and other tropical cyclones flummox as disorganized clusters of showers and thunderstorms. When one of these clusters becomes organized with its winds making a bed circle around a center, it is called a tropical depression. When a depression’s sustained winds reach 63 km/h (39 mph) or more, it becomes a tropical storm and is given a name. By definition, a tropical storm becomes a hurricane when winds reach 119 km/h (74 mph) or more.Characteristics of Hur ricane-A hurricane consists of bands of thunderstorms that spiral toward the low-pressure center, or â€Å" center” of the storm. Winds also spiral in toward the center, hasten up as they approach the affection. larger-than-life thunderstorms create an â€Å" inwardness wall” around the center where winds are the strongest. Winds in the eye itself are nigh calm, and the sky is a good deal derive. Air pressures in the eye at the surface head for the hills from around 982 hectopascals (29 inches of mercury) in a weak hurricane to lower than 914 hectopascals (27 inches of mercury) in the strongest storms. Hectopascals are the metric unit of air pressure and are the same as millibars, a term used by many weather forecasters in the joined States. Hectopascals is the preferred term in scientific journals and is being used more ofttimes in public forecasts in nations that use the metric system. )In a large, strong storm, hurricane-force winds may be felt over an area w ith a diam of more than coulomb km (60 m). The diameter of the area alter by gale winds and torrential rain can extend another 200 km (120 m) or more outward from the eye of the storm.The diameter of the eye may be less than 16 km (10 m) in a strong hurricane to more than 48 km (30 m) in a weak storm. The little the diameter of the eye, the stronger the hurricane winds will be. A hurricane’s strength is rated from kinsperson 1, which has winds of at least 119 km/h (74 mph), to Category 5, which has winds of more than 249 km/h (155 mph). These categories, known as the Saffir-Simpson hurricane scale, were developed in the 1970s. cruller Tornado, violently rotating column of air extending from ithin a thundercloud down to ground level. The strongest wisecrackes may sweep houses from their foundations, stamp out brick buildings, toss cars and educate buses through the air, and eventide lift coerce cars from their tracks. Tornadoes vary in diameter from tens of meters to scrawnyly 2 km (1 mi), with an specialty diameter of approximately 50 m (160 ft). al approximately(prenominal) whirles in the northern hemisphere create winds that blow counterclockwise around a center of extremely low atmospheric pressure. In the southern hemisphere the winds loosely blow clockwise.Peak wind speeds can range from near 120 km/h (75 mph) to al close to 500 km/h (300 mph). The forward motion of a wisecrack can range from a near standstill to al intimately 110 km/h (70 mph). A tornado becomes macroscopic when a condensation funnel do of water vapor (a funnel cloud) forms in extreme low pressures, or when the tornado lofts dust, dirt, and debris upward from the ground. A jump on tornado may be columniform or tilted, narrow or all-encompassingâ€sometimes so broad that it appears as if the raise thundercloud itself had descended to ground level. whatsoever tornadoes resemble a swaying elephants trunk.Others, especially very violent ones, may break into several intense suction vorticesâ€intense swirling lower classes of airâ€each of which rotates near the parent tornado. A suction vortex may be only a some meters in diameter, and thus can destroy one house bandage passing a neighboring house relatively unscathed. Formation-Many tornadoes, including the strongest ones, develop from a special type of thunderstorm known as a supercell. A supercell is a long-lived, rotating thunderstorm 10 to 16 km (6 to 10 mi) in diameter that may last several hours, travel hundreds of miles, and offer several tornadoes.Supercell tornadoes are very much produced in succession, so that what appears to be a very long damage path from one tornado may actually be the result of a new tornado that forms in the area where the front tornado died. Sometimes, tornado outbreaks occur, and swarms of supercell storms may occur. Each supercell may spawn a tornado or a sequence of tornadoes. The complete process of tornado arrangement in supercells is still debated among meteorologists. Scientists generally agree that the first exhibit in tornado formation is an interaction between the storm updraft and the winds.An updraft is a modern of warm, moist air that rises upward through the thunderstorm. The updraft interacts with the winds, which moldiness change with height in favorable ship canal for the interaction to occur. This interaction causes the updraft to rotate at the middle levels of the automatic teller machine. The rotating updraft, known as a mesocyclone, stabilizes the thunderstorm and gives it its long-lived supercell characteristics. The next stage is the training of a strong downdraft (a current of cooler air that moves in a downward direction) on the backside of the storm, known as a rear-flank downdraft.It is not clear whether the rear-flank downdraft is induced by rainfall or by pressure forces set up in the storm, although it becomes progressively colder as the rain evaporates into it. This cold air moves downward because it is denser than warm air. The speed of the downdraft increases and the air plunges to the ground, where it fans out at speeds that can exceed 160 km/h (100 mph). The favored location for the development of a tornado is at the area between this rear-flank downdraft and the main storm updraft.However, the lucubrate of why a tornado should form there are still not clear. The same condensation process that creates tornadoes makes obvious the generally weaker sea-going tornadoes, called waterspouts. Waterspouts occur most ofttimes in tropical waters. OccurrenceThe fall in States has the highest average annual number of tornadoes in the world, about 800 per year. Outside the United States, Australia ranks second in tornado frequency. Tornadoes also occur in many other countries, including China, India, Russia, England, and Germany.Bangladesh has been struck several times by devastating orca tornadoes. In the United States, tornadoes occur in all 50 states. Howeve r, the neighborhood with the most tornadoes is â€Å"Tornado road,” a swath of the western United States extending from the Texas Gulf Coastal gauze-like due north through eastern South Dakota. Another area of high concentration is â€Å" due south Alley,” which extends across the Gulf Coastal Plain from south Texas eastward to Florida. Tornadoes are most frequent in the Midwest, where conditions are most favorable for the development of the severe thunderstorms that produce tornadoes.The Gulf of Mexico ensures a supply of moist, warm air that enables the storms to survive. Weather conditions that trigger severe thunderstorms are frequently in place here: convergence (flowing together) of air along boundaries between wry and moist air masses, convergence of air along the boundaries between warm and cold air masses, and low pressure systems in the upper atmosphere traveling eastward across the plains. In winter, tornado activity is usually engrossed to the Gulf Co astal Plain. In spring, the most nimble tornado season, tornadoes typically occur in central Tornado Alley and astward into the Ohio Valley. In summer, most tornadoes occur in a northern band reaching from the Dakotas eastward into Pennsylvania and southern bran-new York State. The worst tornado disasters in the United States have claimed hundreds of lives. The Tri-State Outbreak of March 18, 1925, had the highest remainder toll: 740 people died in 7 tornadoes that struck Illinois, Missouri, and Indiana. The Super Outbreak of April 3-4, 1974, spawned 148 tornadoes (the most in any known outbreak) and killed 315 people from Alabama north to Ohio.Floods When it rains or snows, some of the water is retained by the soil, some is shine uped by vegetation, some evaporates, and the remainder, which reaches rain buckets channels, is called runoff. Floods occur when soil and vegetation cannot absorb all the water; water indeed runs off the land in quantities that cannot be carried in stream channels or retained in natural ponds and constructed reservoirs. around 30 percent of all temerity is runoff, and this amount may be change magnitude by melting snow masses.Periodic floods occur naturally on many rivers, forming an area known as the flood plain. These river floods often result from heavy rain, sometimes have with melting snow, which causes the rivers to overflow their banks; a flood that rises and falls rapidly with little or no advance warning is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area. Coastal areas are occasionally flooded by unusually high tides induced by severe winds over ocean surfaces, or by tsunamis caused by undersea earthquakes.Effects of Floods-Floods not only damage prop and endanger the lives of human and animals, but have other effects as well. Rapid runoff causes soil erosion as well as sediment deposition problems downstream. Spawning grounds for angle and other wildlife ha bitat are often destroyed. amply-velocity currents increase flood damage; prolonged high floods delay job and interfere with drainage and economic use of lands. Bridge abutments, bank lines, sewer outfalls, and other structures within floodways are damaged, and navigation and hydroelectric power are often impaired.Financial losses due to floods are commonly millions of dollars each year. Drought Drought, condition of abnormally run dry weather within a geographical region where some rain aptitude usually be expected. A drouth is thus quite distinct from a dry climate, which designates a region that is normally, or at least seasonally, dry. The term drouth is applied to a period in which an unusual scarcity of rain causes a serious hydrological imbalance: Water-supply reservoirs empty, wells dry up, and crop damage ensues.The severity of the drouth is gauged by the degree of moisture deficiency, its duration, and the size of the area affected. If the drought is brief, it is known as a dry spell, or partial drought. A partial drought is usually defined as more than 14 days without appreciable precipitation, whereas a drought may last for years. Droughts tend to be more severe in some areas than in others. Catastrophic droughts generally occur at latitudes of about 15°-20°, in areas bordering the permanently arid regions of the world.Permanent aridity is a characteristic of those areas where warm, tropical air masses, in descending to earth, become hotter and drier. When a poleward slant in the prevailing westerlies occurs , the high-pressure, anticyclonic conditions of the permanently arid regions impinge on areas that are normally subject to seasonally wet low-pressure weather and a drought ensues. A southward shift in the westerlies caused the most severe drought of the twentieth century, the one that afflicted the African region called the Sahel for a dozen years, beginning in 1968.In North America, archaeological studies of Native Americans a nd statistics derived from semipermanent agricultural records show that six or seven centuries ago whole areas of the southwestward were abandoned by the indigenous agriculturists because of recurrent droughts and were never reoccupied. The statistics indicate that roughly every(prenominal) 22 yearsâ€with a clearcutness of three to four yearsâ€a major drought occurs in the United States, most seriously affecting the Prairie and midwestern states.The disastrous drought of the 1930s, during which large areas of the owing(p) Plains became known as the Dust Bowl, is one example. The effect of the drought was aggravated by overcropping, overpopulation, and lack of timely relief measures. In Africa, the Sahel drought was also aggravated by nonclimatic determinants such as overcropping, as well as by problems between nations and peoples inimical with one another. Although drought cannot be reliably predicted, certain precautions can be taken in drought-risk areas.These embro il construction of reservoirs to hold emergency water supplies, education to forefend overcropping and overgrazing, and programs to limit settlement in drought-prone areas. release vent, mountain or hill form by the accumulation of materials erupted through one or more openings (called volcanic vents) in the earths surface. The term blowhole can also refer to the vents themselves. Most blowholees have horrid sides, but some can be piano sloping mountains or even flat tablelands, tablelands, or plains.The volcanoes above sea level are the best known, but the vast majority of the worlds volcanoes lie on a lower floor the sea, form along the global pelagic ridge systems that crisscross the deep ocean floor . According to the Smithsonian Institution, 1,511 above-sea volcanoes have been spry during the past 10,000 years, 539 of them erupting one or more times during written history. On average, 50 to 60 above-sea volcanoes worldwide are active in any given year; about half of the se are continuations of eruptions from previous years, and the rest are new.Volcano Formation-All volcanoes are form by the accumulation of magma (molten rock that forms below the earths surface). Magma can erupt through one or more volcanic vents, which can be a single opening, a cluster of openings, or a long crack, called a fissure vent. It forms deep within the earth, generally within the upper part of the mantle (one of the layers of the earth’s crust), or less commonly, within the base of the earths crust. High temperatures and pressures are needed to form magma.The lusty mantle or crustal rock must be melted under conditions typically reached at depths of 80 to 100 km (50 to 60 mi) below the earth’s surface. Once tiny droplets of magma are formed, they begin to rise because the magma is less dense than the upstanding rock surrounding it. The processes that cause the magma to rise are poorly understood, but it generally moves upward toward lower pressure regio ns, crush into spaces between minerals within the solid rock. As the individual magma droplets rise, they join to form ever-larger blobs and move toward the surface.The larger the rising blob of magma, the easier it moves. uphill magma does not reach the surface in a steady manner but tends to accumulate in one or more underground storage regions, called magma reservoirs, beforehand it erupts onto the surface. With each eruption, whether fickle or non fickle, the material erupted adds another layer to the growing volcano. afterward many eruptions, the volcanic materials pile up around the vent or vents. These loads form a topographic feature, such as a hill, mountain, plateau, or crater, that we own as a volcano.Most of the earths volcanoes are formed beneath the oceans, and their locations have been documented in recent decades by mapping of the ocean floor. Volcanic Materials- 1-Lava-Lava is magma that breaks the surface and erupts from a volcano. If the magma is very blan d, it flows rapidly down the volcano’s slopes. Lava that is more sticky and less fluid moves slower. Lava flows that have a continuous, even-tempered, ropy, or surging surface are called pahoehoe (pronounced pah HOH ee hoh ee) flows, while aa (pronounced ah ah) flows have a jagged surface composed of loose, irregularly shaped lava chunks.Once cooled, pahoehoe forms smooth rocks, while aa forms jagged rocks. The words pahoehoe and aa are Hawaiian terms that describe the grain of the lava. Lava may also be set forth in terms of its composition and the type of rock it forms. Basalt, andesite, , and rhyolite are all different kinds of rock that form from lava. Each type of rock, and the lava from which it forms, contains a different amount of the deepen silicon dioxide. Basaltic lava has the least amount of silicon dioxide, andesitic and dacitic lava have medium levels of silicon dioxide, while rhyolitic lava has the most. -Tephra-Tephra, or pyroclastic material, is do of ro ck fragments formed by fickle shattering of sticky magma (see Pyroclastic Flow). The term pyroclastic is of Hellenic origin and means ‘fire-broken (pyro, â€Å"fire”; klastos, â€Å"broken”). Tephra refers to any airborne pyroclastic material unheeding of size or shape. The best-known tephra materials include pumice, clinker bricks, and volcanic ash. These fragments are exploded when gases build up inside a volcano and produce an explosion. The pieces of magma are shot into the air during the explosion.Ash refers to fragments smaller than 2 mm (0. 08 in) in diameter. The finest ash is called volcanic dust and is made up of particles that are less than 0. 06 mm (0. 002 in) in diameter. Volcanic blocks, or bombs, are the largest fragments of tephra, more than 64 mm (2. 5 in) in diameter (baseball size or larger). Some bombs can be the size of a small car. 3-Gases-Gases, primarily in the form of steam, are released from volcanoes during eruptions. All eruptions, fickle or nonexplosive, are accompanied by the release of volcanic gas.The sudden lam of high-pressure volcanic gas from magma is the driving force force for eruptions. Gases come from the magma itself or from the hot magma coming into contact with water in the ground. Volcanic plumes can appear swarthy during an eruption because the gases are mixed with dark-colored materials such as tephra. Most volcanic gases predominantly consist of water vapor (steam), with degree Celsius dioxide (CO2) and sulfur dioxide (SO2) being the next two most common compounds along with smaller amounts of chlorine and fluorine gases.Types of Volcano 1-Cinder Cones and composite plant Volcanoes-Cinder cones and composite volcanoes have the familiar cone-shaped shape that people most often associate with volcanoes. Some of these form beautifully symmetrical volcanic hills or mountains such as Paricutin Volcano in Mexico and raise Fuji in Japan. Although both cinder cones and composite volcanoes are mostly the results of explosive eruptions, cinder cones consist exclusively of fragmental lava. This fragmental lava is erupted explosively and made up of cinders. -Shield Volcanoes-Shield volcanoes (also called volcanic shields) get their name from their distinctive, gently sloping mound-like shapes that resemble the fighting shields that antediluvian patriarch warriors carried into battle.Their shapes reflect the fact that they are constructed primarily of countless fluid basaltic lava flows that erupted nonexplosively. Such flows can easily spread great distances from the feeding volcanic vents, similar to the spreadhead out of hot syrup poured onto a plate. Volcanic shields may be each small or large, and the largest shield volcanoes are many times larger than the largest composite volcanoes. -Caldera-A caldera is a round or oval-shaped low area that forms when the ground collapses because of explosive eruptions. An explosive eruption can explode the top off of the moun tain or exculpate all of the magma that is inside the volcano. Either of these actions may cause the volcano to collapse. Calderas can be bigger than the largest shield volcanoes in diameter. Such volcanic features, if geologically young, are often outlined by an irregular, steep-walled boundary (a caldera rim), which reflects the victor ringlike zone, or fault, along which the ground collapse occurred.Some calderas have hills and mountains rising within them, called resurgent domes, that reflect volcanic activity after the initial collapse. 4-Volcanic Plateaus-Some of the largest volcanic features on earth do not actually look like volcanoes. Instead, they form extensive, approximately flat-topped accumulations of erupted materials. These materials form volcanic plateaus or plains covering many thousands of square kilometers. The volcanic materials can be either very fluid basaltic lava flows or far-traveled pyroclastic flows.The basaltic lava flows are called flood or plateau b asalts and are erupted from many fissure vents. Volcano Hazards-Eruptions pose direct and indirect volcano hazards to people and property, both on the ground and in the air. Direct hazards are pyroclastic flows, lava flows, falling ash, and debris flows. Pyroclastic flows are mixtures of hot ash, rock fragments, and gas. They are especially deadly because of their high temperatures of 850° C (1600° F) or higher and immobile speeds of 250 km/h (160 mph) or greater.Lava flows, which move much more slowly than pyroclastic flows, are rarely life threatening but can produce massive property damage and economic loss. Heavy accumulations of volcanic ash, especially if they become wet from rainfall, can collapse roofs and damage crops. Debris flows called lahars are composed of wet concretelike mixtures of volcanic debris and water from melted snow or ice or heavy rainfall. Lahars can travel quickly through valleys, destroying everything in their paths. Pyroclastic and volcanic debr is flows have caused the most eruption-related deaths in the 20th century.\r\n'