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Natural Disasters Notes.docx

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McMaster University
Earth Sciences
Sergei Basik

Natural Disasters 1/22/2013 11:28:00 AM Chapter 1: Natural Hazards and Disasters Natural Hazard: hazards in nature that endanger our property and physical well-being Natural Disaster: A natural event that causes significant damage to life or property Catastrophe: when a natural event kills or injures large numbers of people or causes extensive property damage In the US  Heat and drought account for the largest numbers of deaths o There were more deaths from heat waves between 1997 to 2008 than from any other type of natural hazard  Flooding is the second most deadly hazard The number of deaths from a given hazard can vary significantly from year to year due to rare major events The rate of fatalities can also change over time as a result of safety measures or trends in leisure activities The type of damage sustained as a result of a natural disaster also depends on the economic development of the area where it occurs  In developing countries there are increasing numbers of deaths from natural disasters  In developed countries there are typically greater economic losses o Developed countries show lower population growth, forewarning is more immediate and people can easily move The average annual cost of natural hazards has increased dramatically over the past several decades due to :  The increase in world population overall  Human migration to more hazardous areas Relationships Among Events Precursor Events: smaller events that precedes a major natural event which may warn of the impending disaster Mitigating Hazards Mitigation: efforts to prepare for a disaster and reduce its damage  Engineering projects  Government policies  Public education Land-Use Planning  Reduce losses from natural disasters is to find out where disasters are likely to occur and restrict development there Insurance  Help with recovery once a disaster occurs  Lessens the financial impact of disasters after the fact The Role of Government  USGS- US Geological Survey  GSC- Geological Survey of Canada o Involved in earthquake and volcano research  FEMA- Federal Emergency Management Agency- brings order to chaos of relief efforts that seemed invariably to emerge after natural disasters The Role of Public Education Natural Disasters 1/22/2013 11:28:00 AM Chapter 2: Plate Tectonics and Physical Hazards Earth Structure Distinction between the mantle and the crust is based on rock composition Distinction between two zones of the earth is based on rock rigidity or strength Lithosphere: stiff, rigid outer rind of the Earth  Made up of large blocks called tectonic plates o Continental Lithosphere: silica-rich crust, lowest density, 30 to 50 km thick underlain by the upper part of the mantle o Oceanic Lithosphere: about 60 km thick- its top 7 km are a low-silica basalt-composition crust  Denser than continental because it contains more iron and magnesium rich minerals Asthenosphere: inner, hotter, more easily deformed part  Part of the earths mantle below the lithosphere that behaves in a plastic manner  The rigid and brittle lithosphere moves over it Mantle: the thick layer of material below the thin crust and above the earths core. Most peridotite in composition in its upper part. Its density approximates 3.2 or 3.3 g/cm in the upper part and 4.5 g/cm in lower part Isostacy: lower-density crust floats in earths higher density mantle Moho- the boundary between Earths crust and mantle has been identified as a major difference in density called Moho and it marks the base of the continental crust Plate Movement Divergent Boundaries: plates move away from eachother Convergent Boundaries: plates move towards each other Subduction Zone: cases where one or both of the plates are oceanic lithosphere, the denser plate will slide down or be subducted into the asthenosphere Transform Boundary: two plates slide past eachother Divergent Boundaries Oceanic Ridges -where plates pull apart by the sinking of heavy lithosphere at oceanic trenches, make a system of more or less connected oceanic ridges that wind
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