Study Guide For EESA05, Chapter 1

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Environmental Science
Ingrid L.Stefanovic

Chapter 1: Introduction to Natural Hazards Tsunami in Indian Ocean on Dec 26, 2004 claimed more than 200 000 lives in 11 countries Subduction zone is a long, relatively narrow strip of Earths lithosphere where one of the large tectonic plates that constitute Earths thin outer shell subducts or moves beneath another. The zone of collision between the two plates is a huge fault that extends for hundreds of km along the ocean floor, parallel to the edge of a continent or an island, such as Sumatra Giant earthquakes occur at these sites, releasing energy that has slowly built up along the fault over centuries Warning systems require a communications infrastructure that permits info to rapidly reach emergency officials in areas at risk; those officials should have plans to rapidly evacuate people from low-lying coastal areas 1.1: Why studying Natural Hazards is Important Processes: Internal and External process: ways in which events, such as volcanic eruptions, earthquakes, landslides and floods, affect Earths surface volcanic eruptions and earthquakes are a result of internal forces explained by theory of plate tectonics (large blocks of the Earths crust) o occur at boundaries between tectonic plates external forces operate at or near the Earths surface wind and ocean circulation, and water evaporation determine Earths climate and drive the hydrologic cyclethese forces in turn are directly related to hazardous processes such as violent storms, floods and coastal erosion mass wasting is driven by both internal and external forces o landslides result from gravity acting on hillslopes that have been formed by tectonic processes and erosion. Gravity is the force that attracts one body to anotherin this case the attraction of surface materials toward the center of the earth. Because of gravitational attraction, rocks and soils on mountainsides and the water that falls as precipitation all move down slope processes we consider are hazards are natural and derive from internal heating of earth and external energy from the sun events become hazardous only when they threaten human beings Hazard, Risk, Disaster and Catastrophe hazard is any natural process that threatens human life or property; process itself is not a hazard, it becomes a hazard only when threatening human interests risk: expressed as the probable severity that a destructive event will occur multiplied by the events likely impact on people and property; risk integrates hazard and social vulnerability disaster and catastrophe refer to events that cause serious injury, loss of life and property damage over a limited time and within a specific geographic area disasters may be regional or even national in scope, whereas catastrophe commonly have consequences far beyond the area that is directly affected and require huge expenditures of time and money for recovery mitigation is used by scientists, planners and policy makers when describing efforts to prepare for disasters and to minimize their harmful effects Death and Damage Caused by Natural Hazards in NA, natural hazards that cause the greatest loss of life are not the same as those that cause most property damage tornadoes and windstorms cause the largest number of deaths each year, lightening, floods and hurricanes also take a heavy poll in most developing countries more lives are lost north American disaster take a large toll on the economy (loss of economic activity and employment) natural hazards differ greatly in their potential to create a catastrophe 1 www.notesolution.como floods, hurricanes, earthquakes and volcanic eruptions and large wildfires are most likely to create catastrophe o landslides, snow avalanches and tornado generally affect small area and thus are rarely catastrophic o coastal erosion, lightening, and expansive soils do not create catastrophes but can still cause much damage risks associated with natural hazards change with time because of the changes in land-use patterns o removal of natural vegetation by agriculture, forestry, urbanization and mining can increase erosion and sedimentation damage from most hazardous natural processes in Canada is increasing, but the number of deaths from many hazards is decreasing because of better planning, forecasting, warning and engineering 1.2: Role of Time in Understanding Hazards hazard forecasts and warning are more accurate if we combine info about the past behavior of the process with an understanding of present conditions 1.3 Geologic Cycle geology, topography and climate govern the type, location and intensity of natural processes geological cycle: 4 associated sequences of earth processes: tectonic cycle, rock cycle, hydrologic cycle and biogeochemical cycles The Tectonic Cycle tectonic refers to the large-scale geologic processes that deform the earths crust and produce such features as ocean basins, continents and mountains tectonic process are driven by forces deep within earth tectonic plates are large blocks that form the outer shell of earth tectonic cycle involves the creation, movement and destruction of tectonic plates, and one cycle can last more than 200 MY Earths Lithosphere and Crust outermost or surface layer is called the lithosphere and is stronger and more rigid than deeper material o average thickness is about 100 km; it ranges from a
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