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2 hrly gs ch 06 natural disasters

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  • 1. Natural Disasters
  • 2. What is a Natural Disaster? • Definition: – The effect of a natural hazard, which leads to financial, environmental or human losses – Natural events that kill people or damage property or the environment
  • 3. List of Natural Disasters • Following are the different weather phenomena we are going to discuss: – – – – – Avalanche Blizzard Earthquake Hailstorm Hurricanes – – – – – – Lightning Tornado Tsunami Typhoon Volcano Wildfire
  • 4. Avalanche
  • 5. What is an Avalanche? • Definition: – When massive slabs of snow break loose from a mountainside and shatter like broken glass as they race downhill • These moving masses can reach speeds of 80 miles (130 kilometers) per hour within about five seconds.
  • 6. • What causes Avalanche? – A vibration or movement like the voice of a person or a train – Certain weather conditions like wind and rain – A rock or a piece of ice can shake the snow to slide down the mountain
  • 7. • Avalanches kill more than 150 people worldwide each year • Victims caught in these events seldom escape • Once the avalanche stops, it settles like concrete. Bodily movement is nearly impossible
  • 8. Blizzard
  • 9. What is a Blizzard? • Definition: – A severe snowstorm that usually has very cold temperatures and high winds. These two conditions create blowing snow – A long-lasting snowstorm with very strong winds and intense snowfall
  • 10. • Blizzard Warning: – Heavy snow and strong winds will produce a blinding snow, near zero visibility, deep drifts and life-threatening wind chill • The blowing winds and low temperature can cause frostbite and/or hypothermia
  • 11. Earthquake
  • 12. What is an Earthquake? • Definition: – An earthquake is what happens when two blocks of the earth suddenly slip past one another • Fault plane  The surface where the slip occurs • Hypocenter  The location below the earth’s surface where the earthquake starts • Epicenter  The location directly above it on the surface of the earth
  • 13. • The Plate Tectonic Theory – The earth's crust and upper mantle is composed of several large, thin, relatively rigid plates that move relative to one another – The plates are all moving in different directions and at different speeds. – Sometimes the plates crash together or pull apart. When this happens, it commonly results in earthquakes
  • 14. • Earthquakes can be felt over large areas although they usually last less than one minute • How are earthquakes recorded? – By instruments called seismographs – The recording they make is called a seismogram
  • 15. – When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not – Instead the spring or string that it is hanging from absorbs all the movement – The difference in position between the shaking part of the seismograph and the motionless part is what is recorded
  • 16. Volcano
  • 17. What is a Volcano? • Definition: – An opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface • Volcanoes are generally found where – tectonic plates are diverging or converging – there is stretching and thinning of the Earth's crust in the interiors of plates
  • 18. • Volcanoes are found in three states – An extinct volcano will never erupt again – A dormant volcano has not erupted in 2000 years – An active volcano has erupted recently and is likely to erupt again
  • 19. • Advantages of Volcano – Many people rely on volcanoes for their everyday survival. – Geothermal energy can be harnessed by using the steam from underground which has been heated by the Earth's magma. • Used to drive turbines in geothermal power stations to produce electricity for domestic and industrial use. Used in Iceland and New Zealand
  • 20. • Tourist attraction: Millions of visitors every year visit the volcano, hot springs and geysers. – Tourism creates many jobs for people like in hotels, restaurants, gift shops and locals can act as tour guides • Lava contains minerals which can be mined once it has cooled. These include gold, silver, diamonds, copper and zinc
  • 21. • Volcanic areas often contain some of the most mineral rich soils in the world. This is ideal for farming. – These areas can be cultivated to produce healthy crops and rich harvests
  • 22. Tsunami
  • 23. What is a Tsunami? • Definition: – A series of large ocean wave usually caused by an underwater earthquake or a volcanic explosion • The waves may travel in the open sea as fast as 450 miles per hour • Tsunamis can reach the heights of over 100 feet (30.5 meters) • They are NOT tidal waves
  • 24. • Tidal waves are caused by the forces of the moon, and planets upon the tides, as well as the wind as it moves over the water. • Whereas a tsunami flows straight. This is why they cause so much damage
  • 25. Tornado
  • 26. What is a Tornado? • Definition: – A violent rotating column of air extending from a thunderstorm to the ground – Vertical funnels of rapidly spinning air • Also known as Twister • Wind speed: up to 300 mph • Funnels width: up to 660 feet (200 meters)
  • 27. • Tornadoes are formed when moist warm air and cool dry air collide to create unstable atmosphere • This collision creates a shift in the wind direction and speed • However, tornadoes are still a mystery. Scientists still are not very sure what causes and finishes them
  • 28. • Tornadoes can occur anywhere and any time as long as the proper conditions are there • But the United States is a major hotspot with about a thousand tornadoes every year. – "Tornado Alley," a region that includes eastern South Dakota, Nebraska, Kansas, Oklahoma, northern Texas, and eastern Colorado, is home to the most powerful and destructive of these storms.
  • 29. Tropical Cyclones
  • 30. What is a Tropical Cyclone? • Definition: – A storm system characterized by a large lowpressure center and numerous thunderstorms that produce strong winds and heavy rain • It is formed over oceans
  • 31. • Tropical cyclones gather heat and energy through contact with warm ocean waters – They form only over warm ocean waters near the equator • The warm, moist air over the ocean surface rises upward
  • 32. • Because this air moves up and away from the surface, there is less air left near the surface • In other words, the warm air rises, causing an area of lower air pressure below
  • 33. • Tropical cyclone a generic term – Depending on its location, is referred to by names: • Hurricane • Typhoon • Cyclone
  • 34. What is a Hurricane? • Definition: – Only tropical cyclones that form over the Atlantic Ocean or eastern Pacific Ocean are called hurricanes
  • 35. What is a Typhoon? • Definition: – Only tropical cyclones that form over the western Pacific Ocean are called typhoons
  • 36. What is a Cyclone? • Definition: – Only tropical cyclones that form over the Indian Ocean areas are called cyclones
  • 37. Wildfire
  • 38. What is a Wildfire? • Definition: – Any uncontrolled fire often occurring in wildland areas • Also known as a wildland fire, forest fire, vegetation fire, grass fire, or bush fire • Speed: up to 23 kilometers an hour
  • 39. • Consume everything—trees, brush, homes, even humans—in its path • Three conditions are needed for a wildfire to burn, which firefighters refer to as the fire triangle: – Fuel  any flammable material surrounding a fire like trees, grass, houses etc – Oxygen  air supplies it – Heat source  help spark the wildfire and bring fuel to temperatures hot enough to ignite. Lightning, burning campfires or cigarettes, hot winds, and the sun
  • 40. • Wildfires can occur anywhere, but are common in the forested, vegetated, and grasslands areas • Fires are particularly prevalent in the summer and fall, and during droughts when fallen branches, leaves, and other material can dry out and become highly flammable
  • 41. How do firefighters put out the wildfires? • Use a tool known as a pulaski, a combination of an ax and hoe used to dig a fireline. – A fireline is a strip of land from which all brush and debris have been cleared to rob a wildfire of its fuel.
  • 42. • Use hotshots and smoke jumpers to clear a large path in a big circle around the fire so the blaze is contained in a ring of dirt. – When the fire reaches this area, it runs out of fuel and starves to death.
  • 43. • If the fire is too large, however, planes and helicopters fly overhead, dropping water and special chemicals that smother the flames. This pink, fireretardant chemical is called sky jell-o
  • 44. Hail Storm
  • 45. What is a Hailstorm? • Definition: Hail – A form of solid precipitation in the form of irregular lumps of clear ice and compact snow • Any thunderstorm which produces hail that reaches the ground is known as a hailstorm
  • 46. • Conditions necessary for Hail formation: – – – – Strong thunderstorms clouds Strong motion of air Large water droplets A good portion of the cloud layer is below freezing 0 °C • Spherical in shape with a diameter up to 0.5 inch – In rare cases, hailstones having diameters up to 6 inches have been observed
  • 47. • Hail causes much damage to: – Farmers’ crops • Wheat, corn, soybeans, and tobacco are the most sensitive crops to hail damage – Livestock – Humans • Massive hails can cause concussions or fatal head trauma – Man-made structures • Especially glass structures – Airplanes and automobiles
  • 48. • Methods of detecting hail-producing thunderstorms – Weather satellites – Weather radar imagery • Severe weather warnings are issued for hail when the stones reach a damaging size
  • 49. Lightning
  • 50. What is a Lightning? • Definition: – A bright flash of electricity produced by a thunderstorm • All thunderstorms produce lightning and are very dangerous
  • 51. • Lightning kills and injures more people each year than hurricanes or tornadoes; between 75 to 100 people
  • 52. • What causes Lightning? – Lightning is an electric current. – Within a thundercloud way up in the sky, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. – All of those collisions create an electric charge. After a while, the whole cloud fills up with electrical charges. – The positive charges or protons form at the top of the cloud and the negative charges or electrons form at the bottom of the cloud.
  • 53. – Since opposites attract, that causes a positive charge to build up on the ground beneath the cloud. – The grounds electrical charge concentrates around anything that sticks up, such as mountains, people, or single trees. – The charge coming up from these points eventually connects with a charge reaching down from the clouds and - zap - lightning strikes!
  • 54. • Types of lightning – Cloud-to-Ground – Intra-cloud – Inter-cloud • How hot is lightning? – Lightning is approximately 54,000o Fahrenheit. That is six times hotter than the surface of the sun!