Module 3-Natural Events and Hazards. Section 1-Natural events, hazards and disastersHow natural are natural hazards?      ...
Module 3-Natural Events and Hazards. Section 1-Natural events, hazards and disastersFigure 3 - POTENTIALLY HAZARDOUS NATUR...
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GEOGRAPHY UNIT 1 Module 3 natural events and hazards. section 1-natural events, hazards and disasters

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GEOGRAPHY UNIT 1 Module 3 natural events and hazards. section 1-natural events, hazards and disasters

  1. 1. Module 3-Natural Events and Hazards. Section 1-Natural events, hazards and disastersHow natural are natural hazards? Notwithstanding the term "natural," a natural hazard has an element of human involvement. Aphysical event, such as a volcanic eruption, that does not affect human beings is a natural phenomenonbut not a natural hazard. A natural phenomenon that occurs in a populated area is a hazardous event. Ahazardous event that causes unacceptably large numbers of fatalities and/or overwhelming propertydamage is a natural disaster. In areas where there are no human interests, natural phenomena do notconstitute hazards nor do they result in disasters. This definition is thus at odds with the perception ofnatural hazards as unavoidable havoc wreaked by the unrestrained forces of nature. It shifts the burden ofcause from purely natural processes to the concurrent presence of human activities and natural events. Although humans can do little or nothing to change the incidence or intensity of most naturalphenomena, they have an important role to play in ensuring that natural events are not converted intodisasters by their own actions. It is important to understand that human intervention can increase thefrequency and severity of natural hazards. For example, when the toe of a landslide is removed tomake room for a settlement, the earth can move again and bury the settlement. Human intervention mayalso cause natural hazards where none existed before. Volcanoes erupt periodically, but it is not untilthe rich soils formed on their ejecta are occupied by farms and human settlements that they are consideredhazardous. Finally, human intervention reduces the mitigating effect of natural ecosystems.Destruction of coral reefs, which removes the shores first line of defense against ocean currents andstorm surges, is a clear example of an intervention that diminishes the ability of an ecosystem to protectitself. An extreme case of destructive human intervention into an ecosystem is desertification, which, byits very definition, is a human-induced "natural" hazard. 1 Page
  2. 2. Module 3-Natural Events and Hazards. Section 1-Natural events, hazards and disastersFigure 3 - POTENTIALLY HAZARDOUS NATURAL PHENOMENATypes of Hazards ExamplesAtmospheric Hailstorms Hurricanes Lightning Tornadoes Tropical stormsSeismic Fault ruptures Ground shaking Lateral spreading Liquefaction Tsunamis SeichesOther geological/hydrologic Debris avalanches Expansive soils Landslides Rock falls Submarine slides SubsidenceHydrologic Coastal flooding Desertification Salinization Drought Erosion and sedimentation River flooding Storm surgesVolcanic Tephra (ash, cinders, lapilli) Gases Lava flows Mudflows Projectiles and lateral blasts Pyroclastic flowsWildfire Brush Forest Grass Savannah 2 Page

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