2 hrly gs ch 06 natural disasters


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2 hrly gs ch 06 natural disasters

  1. 1. Natural Disasters
  2. 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. 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. 4. Avalanche
  5. 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. 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. 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. 8. Blizzard
  9. 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. 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. 11. Earthquake
  12. 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. 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. 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. 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. 16. Volcano
  17. 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. 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. 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. 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. 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. 22. Tsunami
  23. 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. 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. 25. Tornado
  26. 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. 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. 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. 29. Tropical Cyclones
  30. 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. 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. 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. 33. • Tropical cyclone a generic term – Depending on its location, is referred to by names: • Hurricane • Typhoon • Cyclone
  34. 34. What is a Hurricane? • Definition: – Only tropical cyclones that form over the Atlantic Ocean or eastern Pacific Ocean are called hurricanes
  35. 35. What is a Typhoon? • Definition: – Only tropical cyclones that form over the western Pacific Ocean are called typhoons
  36. 36. What is a Cyclone? • Definition: – Only tropical cyclones that form over the Indian Ocean areas are called cyclones
  37. 37. Wildfire
  38. 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. 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. 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. 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. 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. 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. 44. Hail Storm
  45. 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. 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. 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. 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. 49. Lightning
  50. 50. What is a Lightning? • Definition: – A bright flash of electricity produced by a thunderstorm • All thunderstorms produce lightning and are very dangerous
  51. 51. • Lightning kills and injures more people each year than hurricanes or tornadoes; between 75 to 100 people
  52. 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. 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. 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!