Natural Hazards

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  1. Classification of major disaster
    Events that overwhelm regions, international assistance is needed, require major reconstruction
  2. Qualifying disasters
    Human loss- impacts of death toll, types of disaster, location, population density, structural loss, economic damage, displacement.

    Insurance claims- delayed real cost, higher GDP (gross domestic product) may result in safer buildings
  3. Government impacts on disasters
    • democratic index
    • -thousands died in Hurricans (most deaths), typhones, EQ, and terrorist attcks

    • Gross domestic impact
    • -millions of dollars lost in natural disaster
  4. Perceptions:
    • Social environment
    • -socio economic characteristics
    • - knowledge of an environment or type of event
    • - ability to cope
    • - geting help

    • Political environment
    • Economic environment
  5. Risk VS vulnerability
    Risk: likelihood something will happen, and consequences if it does happen

    Vulnerability: susceptibility to harm of those at risk, depend on characteristics of a person or group
  6. Mitigation
    • actions taken by humans to minimize the possible effects of a natural hazard
    • - action plans prior to and after an event
  7. Human population: population growth
  8. doubling time
    • number of years required to double the population given an annual percentage
    • - growth about 1.2%
  9. reasons for growth
    • high birth rates- grows 80,000,000 ppl every year
    • better housing/technology
    • advances in the medical world
  10. future world population
    • demographic transition theory
    • mortality and fertility rates decline
    • population referenc bureau estimates world population growth rates are dropping (1.8% in 1990 to 1.2% in 2008)

    • growth slws but population explosion continues
    • avg. 1.6 children/woman: 3.6 bilion
  11. demographics
    • low birth rate- long life expectancy
    • high birth rate- shorter life expectancy
  12. urbanization
    • migration to urban areas
    • mega-cities
  13. carrying capacity
    • an ever changing #
    • food?
    • resources?
  14. Easter Island
    • poor soil
    • 30 native plant species
    • no mamals
    • 25-50original olynesian settlers brought chickens, rats, and various plants

    • Carrying capacity for Easter Island
    • reached by dutch ship in 1722
    • easter sunday
  15. Continental drift: layers of the earth
    • Core: iron and nikel
    • mantle: composed of mostly solid rock
    • crust: floats on top of mantle
  16. Oceanic crust:
    • part of earths lithosphere that surfaces in the ocean basin
    • about 5-10km thick
    • basalt
  17. continental crust:
    Layers of igneous sediment & metamorphic rocks which froms the continents and the areas of shallow seabed close to shores (continental shelves)
  18. Isostacy:
    Less dense materials float on top of more dense materials (iceberg floating in ocean)

    • Stresses:
    • brittle- faulting
    • elastic-folding
  19. Continental drift:
    suggest that the earths crust is composed of several tectonic plates that have the ability to move around
  20. Super continents:
    landmass comprising more than one continental core, or craton
  21. Pangea:
    • supercontinent
    • used to unite all the continents
    • continents seem to fit together
    • plant & animal fossil record across continents
    • geologic deposits similar on different continents
  22. Plate techtonics: Lithosphere
    • rigid outermost shell of a rocky planet
    • broken into plates separated by divergent zones, transform faults, and convergence zones
  23. Tectonic cycle:
    the grand recycling of the upper few hundred kilometers of earth
  24. Divergent plate boundaries:
    • tensional stress
    • non-explosive (found on hot spot)
    • linear deature that exists between two tectonic plates that are moving away from each other
    • produce rifts which produc rift valleys
    • most active occur between oceanic plates (exist as mid-oceanic ridges)
  25. Convergent plate boundaries:
    • compression stress
    • Largest earthquakes- 2 or more collide causing EQ and volcanoes
    • Oceanic plate vs oceanic plate
    • Oceanic plate vs continental plate
    • Continental plate vs continental plate
    • Subduction zones: Large earthquakes, at shallow depths Compressive movement Pull-a-part where the plate is shifting downward At deeper point- Less severe earthquakes
    • Seismic gap: Look for breaks in earthquake centerso Not a science one location could see two earthquakes before a gap may see one
  26. Transform plate boundaries:
    • Sheer stress
    • relative motion is horizontal
  27. Earthquakes
    • releases stress along a fault line
    • EQ commonly caused by volcanic activity
    • magma moving
    • undersea landslides
  28. epicenter:
    point on the surface directly above a fault movement
  29. focus: hypocenter
    initial portion of a fault that moved to generate the ground- below the surface
  30. Measuring earthquakes: seismology
    the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies.
  31. Seismometer
    must have a part that remains stationary and a part on the ground that will vibrate
  32. Waves:
    • Amplitude
    • Wavelength
    • Period
    • Frequency
    • Hertz
  33. Body waves:
    Can occur through the entire depth- surface to core

    • Primary waves: Fastest of the waves, Marked by compression and expansion, Travel through earth, water, and gas
    • push pull movement

    • Secondary waves: Slower, Transverse in motion, Travel only through solids
    • Movement similar to a jump rope
  34. Surface waves:
    • Only occur on the surface
    • Love waves: Similarly to S waves, but side to side
    • Do not move through water
    • Rayleigh waves: Backwards elliptical motion- rolling waves
    • Slowest
    • More energy released when the focus is close to the surface
  35. More on waves:
    • Waves can move through the earth (towards the core)
    • Do not move in straight lines
    • Waves speed up until reaching the asthenosphere
    • Slow initially in the mantle but then speed up
  36. Locating EQ
    • Based on the time difference between the arrival of primary and secondary waves
    • P-s then down to the distance
    • Not directional though
  37. Measuring EQ
    • Magnitude
    • Righter scale: measure it on
    • Richter does not work well for distant or large earthquakes
    • Can both under and overestimate the magnitude
    • Commonly used
    • In use since 1935
    • Best for epicenters less than 300 mi from the seismometers
    • Based on the idea the bigger the quake the greater the shaking

    • Moment magnitude scale: Seismic moment- moving on the whole line
    • Uses seismic moment: Mw = 2/3 log10 (Mo) – 6

    • Mercalli: Describes the intensity felt by people
    • Used to help define magnitudes of historical events Mercalli variables:
    • Magnitude
    • Distance from epicenter
    • Foundation materials
    • Building style
    • Duration of the shaking
  38. Building and retrofitting:
    • Eliminate resonance
    • Change height of building
    • Move weight to lower floors
    • Change shape of building
    • Change building materials
    • Change attachment of building to foundation
    • Hard foundation (high-frequency vibrations)
    • build tall, flexible building
    • Soft foundation (low-frequency vibrations)
    • build short, stiff building
    • sheer walls- Brased frames
    • retrofitting: Base isolation
  39. Foreshock, mainshock, aftershock
    • Foreshocks: smaller quakes that happen prior to the main shock
    • Mainshock: much larger, can get reclassified if the aftershock is larger than the main shock
    • Aftershock: smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock.
  40. Transform faults:
    • Major quakes
    • Turkey
    • California
  41. Tsunamis: Causes
    • Giant, long-period sea waves caused by oceanic disturbances·
    • Japanese word (no plural)·
    • Not giant cresting wave·
    • Characteristics: Most commonly occur after earthquake, Water is not compressible, Water retreat, Many waves
  42. How they travel:
    • Leading edge of an elevated mass of water
    • High velocitiy
    • Reaching the shore: When they reach the shore the front slows and the water behind builds up increasing amplitude·
    • Destruction: Not because of the height of the wave but the momentum and multiple waves or how many there areo Can stay on shore about 30 min then pull back
    • Long wave lengths help the waves bend around islands and hit all sides of the island
  43. Requirments for EQ:
    • Must have vertical plate movement
    • Magnitude of at least 7.5
    • Examples: Alaska- 2 large subduction EQ’s, Chile- strongest EQ at 9.5
  44. Volcanoe caused:
    • Usually from explosions and collapses
    • Example: Krakatau, Indonesia 1883
  45. Landslide caused:
    • Gravity pulling rock and sediment masses into the ocean
    • Subocean
    • Example: Canary islands, Volcanic collapse, 3 mega collapses, Lake and bay tsunami @ 8.0 magnitude
  46. Warning system:
    • Network of earthquake detecting stations
    • Thirty two pressure sensors that weigh the water passing over them

    • what should we do:
    • Get to higher ground
    • Move inland
    • Upper floor of a strong building
    • Tree
    • Anything that floats
  47. Recent tsunamis:
    • Japan: March 11, 2011
    • 9.0 magnitude quake
    • 500 km rupture off the northeast coast of Honshu
    • Wave reached the mainland within minutes
    • Inland as far as 6 miles with waves as high as 38m
    • Death toll at 27,500
    • Damage cost of 326,000,000,000
  48. Volcanoes: occurance
    • 90% of volcanoes are associated with plate boundaries
    • 80% occur at oceanic spreading zones
    • 7-13% occur at subduction zones
    • 10% occur at hot spots
  49. Magma vs lava:
    Magma: mixture of molten or semi molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets.

    Lava: Pahoehoe and aa , refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling
  50. Terminology:
    • Active: Erupt regularly, Within the Holocene (12,000 years ago to present) ,1,500 worldwide, 50 in the United States
    • Dormant: No written record, Most super volcanoes/calderas
    • Many dormant volcanoes are misclassified
    • General rule: if well shaped it should be considered active
    • Extinct: Highly unlikely to erupt due to lack of lava source
  51. Viscosity:
    • measure of the fluidity of a liquid
    • Water vs. honey
    • Temperature
    • Silicon and oxygen
    • Mineral and crystals
  52. Chemical composition of magma:
    • Eight elements make up 98% of continental crust
    • Oxygen and Silicon: differences in silicon dioxide percentages impact the type of eruptive behavior
  53. Volatiles:
    Dissolved gases: water
  54. Eruption styles: Non explosive
    • Hawaiian Commonly preceded by a swarm of earthquakes
    • Fractures release gas out of the caldera allowing then for floods of basaltic lava to flow down the slopes
    • Icelandic :Fissure eruptions
    • Build volcanic plateaus that are flatter than a shield volcano
    • Most peaceful eruptions
  55. Eruption styles: Somewhat explosive:
    • Strombolian-type eruptions: Typical eruption for a scoria cone
    • Large amounts of pyroclasts into the air
  56. Eruption styles:Explosive
    • Vulcanian: Named for the Roman god of fire and blacksmith
    • Alternated between thick, highly viscous lavas and pyroclastic material blown out of the top
    • Plinian: Named for the 17-year-old Pliny the Younger in honor of his detailed written observations of the 79 CE eruption of Vesuvius
    • Gas powered vertical eruptions that carry pyroclastic material up to 50 km into the air
  57. Pyroclastic material: volcanic material
    • Volcanic ash
    • Tephra
    • Rocks
  58. Vesuvius:
    • Submarine volcano in the Bay of Naples
    • First eruption in 79 CE
    • About 4,000 people died in Pompeii
    • Volcano weather"
    • Lahars
  59. Lava domes:
    High-viscosity magma with a low volatile content cools quickly forming a plug over the top of the volcano vent
  60. Calderas:
    Large volcanic depressions formed by the collapse of the emptied magma reservoir

    • Three in the United States:
    • Valles
    • Long Valley
    • Yellowstone
  61. Craters:
    • Circular depression in the ground caused by volcanic activity.
    • It is typically a basin, circular in form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta
  62. Yellow stone:
    • Hotspot
    • Three previous eruptions
    • Caldera (in yellow stone) is 75km long and 45km wide Two resurgent domes,where we see proof of rising magma
  63. Other info:
    • Shield volcanoes: Low viscosity, low volatiles and large volume ›Many thin volcanic rock layers
    • Mauna Loa in Hawaii

    • Stratovolcanoes (composite): Steep-sided, symmetrical peaks
    • Marked differences in magma composition from eruption to eruption

    • Scoria cones :Small conical hills
    • Usually single eruptive
    • Crater is usually less than 2 km in diameter

    • Flod basalts: Largest volcanic events on Earth
    • Measure about 1,200 mi by 1,200 mi and tens of meters thick
Card Set
Natural Hazards
Natural Hazards
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