3 Unit 8A – Human Population Trends & Predictions Chapter 8.1 & 8.2 Central Case – Page 227 China’s One-Child PolicyRead the case and do a Decision-Making Model analysis. First, identify the problem, and then propose a solution. Obviously, the problem is that China is overpopulated. The solution is the One-Child Policy.Now analyze this solution according to our template (Pros, Cons, Short Term consequences, Long Term consequences) and then come to your decision related to the solution.Remember to have at least 3 items under each heading…..i.e., 3 Pros, 3 Cons, …..
4 8A - Trends & Predictions (standards) Trace the path of human population growth from the hunter- gatherer of 10,000 years ago to todayExplain how life changed through the development of agriculture and industrializationList and explain the factors that demographers use to describe the human populationList examples as to why the world population continues to grow though growth rate has decreasedCompare population growth rates between different regions & explain how social factors affect growth & resource useUtilize the demographic transition model to explain the drop in birth and death rates
5 Human Population Growth Advances in agriculture & technology helped increase the human population sizeIt took 200,000 years to reach 1 billion in 1800, but our population has skyrocketed since to 6.8 billion in 2010.10,000 years ago humans went from roaming hunter-gatherers to settled farmers. Better nutrition resulted in longer lives, more children living to maturity, and a slow population increase.The Industrial Revolution (mid-1700s) resulted in a shift from rural to urban societies. Use of fossil fuels & mass food production contributed to a population explosion.
6 Industrial Revolution Sanitation – Louis Pasteur – germ theory of disease; living conditions in the cities improved; better medical practices, soap, cotton clothes all decreased diseaseMedical technology – mass production of medical instruments, medicines (antibiotics, vaccines) helped prevent/reduce severity of viral & bacterial infectionsAgriculture – invention of large fossil-fueled machines made it possible to plant & harvest food in mass quantities; pesticides reduced competition from weeds and killed insects; grew more food from same soil.Results: more food, fewer deaths
7 Recent trends in human population growth Although growth rate has slowed, the population still continues to growDecreased infant mortality, increased life expectancy causes a population to grow quicklyGrowth rate – how a population changes in size during a specific period of timeGrowth rate peaked in the 1960s, it has slowed sinceGrowth rate varies by region (Germany & Russia has a negative growth rate)Technology has allowed us to increase our carrying capacity as we can live comfortably just about anywhere, therefore we don’t know the max. population size
8 Real Data Chart Population Growth Rate of Selected Nations and World, 2008 The table on page 230 and worksheet provided shows 2008 estimates of growth rates and population sizes for several nations and the world.Answer the following questions on the back of your worksheet:Which nation is growing the fastest? Explain your answer.What is happening to Hungary’s population size?Which nation will likely add the most people to the world over th ecourse of a year?In 1970, China’s population growth rate was 2.8%. Do you think China’s population control policies have been effective? Why or Why not?Complete the Real Data worksheet given to your group for a grade.
9 Describing the Human Population Demography – the study of human population statisticsDemographers apply the principles of population ecology to humans (size, pop. density, distribution) to help predict changes and environmental impactPopulation size: roughly 6.8 billionPopulation density – how many people live/sq. milePopulation density is highest in temperate & tropical climates (China, Europe, Mexico, India) and lowest in extreme climates (desert/tundra). More people live by seacoasts & rivers; denser in urban v.s. rural
10 Population Distribution Human population is clumped v.s. random or uniformThis uneven distribution means some areas bear more of an environmental impact than others (Yellow River in China, Mississippi River in U.S. are polluted)Environment is harmed when humans live in areas that cannot support them (deserts by development that takes water supplies, grasslands are overfarmed)Population size, density and distribution gives demographers a “picture” of what the human population looks like in a particular moment in time
11 Answer the following questions for a grade: Describe the main factors that led to a boom in the human population size in the last 300 years.Population A contains 450,000 people and has a 3.3% annual growth rate. Population B has 900,000 people and a 1.8 % annual growth rate. Which population would increase by more people in one year? Explain.Describe the relationship between population density and population distribution.As people become more concentrated in cities, some pressure on ecosystems in areas that are now less populated eases. Why do you think this is the case?Use the internet to research population growth rates in Florida over the last 30 years. Summarize this data on recent trends in population growth with an illustration or poster.
12 Predicting Population Growth Scientists predict the world human population, with moderate growth, to be 9 billion by 2050.Births add, Deaths remove; immigration & emigra- tion affect population size of particular regionsFertility rate – average # of children a female member of a population has during her lifetimeFactors: childhood survivorship, help with farmwork, parents need children to support them as they ageRecently total fertility rates have started to dropReplacement fertility – total fertility rate for a nation that would keep its population size stable; in many nations the replacement fertility is about 2.1
13 Age Structure and Sex Ratios These define a population’s potential for growthAge structure – the relative #s of organisms of each age within a population, use age structure diagramShows the proportion of individuals currently of reproductive age and those who could reproduce in the futureHelps demographers predict size change over timeSex ratios - # of males compared to femalesAt birth, naturally occurring sex ratio of humans has slightly more males (100 females, 106 males born) because males are slightly more likely to die in any given year of life. Human activity can skew this (males emigrating for work, cultural favoritisms)
14 Quick Lab page 237Your group will be given a copy of this lab. Using the data in the Population Size chart, your group will make age structure diagrams for the two subgroups in the U.S. (White male/females and Hispanic male/females). Refer to page 236.After you have made the age structure diagrams, follow the directions to predict, interpret the diagrams, and calculate the % of the White and Hispanic populations that are younger than 20 years old. Remember, the % is the # of males or females divided by the total # x 100 for each subgroup.You will need your data sheet, blank paper, ruler, pencil, colored pencils, and a calculator.
15 Demographic Transition A model that explains the change from high birthrates & death rates to a condition of low birth rates and death rates.Demographic transitions are the result of economic growth that leads to social changes.Good sanitation, effective healthcare, & reliable food supplies result in people living longer. Worldwide, average life expectancy has gone from 46 to 68 yrs. and infant mortality rates have fallen in many areas.Reason: the shift from rural to urban life and industrialization have generated greater personal wealth
16 4 Stages of Demographic Transition Pre-Industrial Stage – death & birth rates are high. Widespread disease, poor medical care, unreliable food & water sources, larger families wanted.Transitional Stage – death rates decline as food & medical care improves. Birthrates remain high. Population increases because birth rates exceed death.Industrial Stage – job opportunities increase, esp. for women. Birth rates decline, closing gap with death rates. Rate of population growth falls.Post-Industrial Stage – birthrates & death rates fall to low & stable levels. Society enjoys the benefits of industrialization without runaway population growth.
17 Social Factors that Affect Pop. Growth Wealth & education affect growth and resource useDeveloping nations tend to have higher fertility rates, infant mortality rates & death rates. Crowded conditions, poor sanitation, poor nutrition, & increased disease. High population growth presents challenges. Many have developed national policies to slow the growth rate. Better educational opportunities for women is tied to declining fertility rates. Over 2/3rds of the world’s people cannot read and 60% of those living in poverty are women.Developed nations are high-income nations. Wealth & rate of resource consumption is unevenly distributed around the globe. Ex. 1 American has as much environmental impact as 5 Chinese or 13 Pakistanis.
18 8.2 packet Individually complete this packet. The due date is _____________________
19 8B – People Paradox (Chp. 8.3) standards Describe why affluent societies tend to have the most impact on the environmentDiscuss how governments can be overwhelmed by population growth in poor societiesList examples of how land overuse and excessive land clearing are spin-offs of meeting a poor society’s survival needsExplain how the gap in the wealth gap both in the world and within societies causes an unequal distribution of the world’s resourcesDescribe how the development of nations affects ecosystems and the human quality of lifeDescribe the pros & cons of technology as related to both our environmental impact and its reduction.List examples of technologies & their specific impacts in Florida
20 Impacts of PopulationThe industrial revolution changed how people live, but it also caused increasing resource consumption & pollutionEcological footprint – amount of land needed to provide a person with the resources they consume and to handle their wasteAffluent societies – with more $, humans consume more food & produce more waste and use more energy; lower pop. growth rate but larger ecological footprintPoor societies – higher pop. growth rate but smaller ecological footprint; overwhelmed governments, land overuse, deforestation, flooding, emerging diseases
21 The Wealth GapThe stark contrast between affluent & poor societies is the cause of social and environmental stressWealth gap – difference in assets and income between individuals in a society, or between nationsAbout 1.4 billion people in developing nations live below the international defined poverty lineThe richest 1/5th of the world’s people use 86% of the world’s resources, many imported from developing nations, leaving only 14% of the global resources (energy, food, water) for 4/5th of the world’s peopleChina’s economic growth resulted in poorer farmland eroding, rivers drying up, air pollution, congestion
22 Impacts of TechnologyTechnology can have both positive & negative impactsTechnology allowed exponential growth of human population, helped to fight diseases, increased life expectancy, provided more comfortable lives, ….Negative impacts: exploitation of resources (soil, minerals, fossil fuels, forests, oceans), pollution, loss of biodiversity, mining, climate change.Positive impacts: development of less harmful technologies (recycle, repurpose), cheaper & cleaner renewable energyMore recent technologies focus on lessening our impact on the environment
23 8.3 reviewExplain the relationship between wealth and poverty, and its impact on the environment.How has technology had both a negative and positive impact on the environment?As developed nations implement ways that reduce their effect on the environment, do you think this will affect quality of life throughout the world? Explain.
24 8C – Land Use & Urbanization Chp. 10 (standards) Describe the different types of land cover and explain how it can affect how the land is used.Compare & contrast rural & urban living. Why did people move to the cities?Explain why transportation is essential to the development & growth of the urban environment.Identify patterns of sprawl & describe how they impact metropolitan areas and the environment around them.Describe the environmental impacts of urbanization, both positive and negative.Explain how sprawl affects transportation, pollution, public health & the economics of an area. Use examples from Florida.
25 Central Case – Growing Pains in Portland, Oregon Chp. 10, page 291, plus worksheetRead the case and complete a Decision- Making Model on this caseWhat is the problem? What is you proposed solution?At least 3 Pros, 3 Cons, 3 Short-term Consequences, 3 Long-term ConsequencesThen, what is your conclusion regarding your proposed solution after analyzing it?
26 Land Cover & Land UseLand cover – vegetation & manufactured structures that cover land (trees, grass, crops, wetlands, water, buildings, pavement).Land use – human activities that occur on land & are directly related to the land (farming, grazing, logging, mining, development, recreation).
27 Land CoverLand cover of an area changes as people settle there and begin to use the landVast grassland of N. America have been replaced by rangeland and croplandDeciduous forests of the NE are mostly replaced by cities and industrial areasScientists cover the economic impact of land cover change & its effects on waterUrban area – mostly developed land covered mainly with buildings & roads that has a human population of 2500 or more.
28 UrbanizationUrbanization occurs when people move out of rural areas toward areas with more/better jobs.Tokyo, Japan’s urban area is over 36 millionMost people live in smaller urban areas/citiesSince 1950, the world’s urban population has more than quadrupled, and the United Nations predicts it will double again by 2050.Urbanization – the shift of people from rural to urban areasThe industrial revolution resulted in farms producing surplus food, allowing many to stop farming as well as creating jobs in citiesU.S. urban population is about 80%, with 50% of the population living in suburbs.
29 Transportation & Urbanization Location is essential to the growth of an urban areaModerate climate, central geography, and ease of transportation all help a city growMost major cities grew near a large body of water, railroad or highway on which goods & people could travel to and from it.Chicago’s location on waterways & transport routes and its location between the West’s natural resources and the East’s industrial centers were all factors in it becoming a large, prosperous city.Florida’s first major cities were all on the coast, and Orlando grew by I4 and Fl. Turnpike.
30 Urban Environmental Impacts Cities have both negative & positive impactsThe type of impact depends on how we use resources, produce goods, transport materials, and deal with wastes.Urban areas export wastes passively through pollution, or actively through trade (pay another to take their garbage).Not all waste and pollution leave the citySmog & acid precipitationNoise pollutionLight pollutionPollution & its health threats are not shared equally among urban residents, with the poor typically living in more polluted areas as they cannot afford to live in a cleaner area
31 1. Heat IslandsInfrastructure – all the facilities, , services & installations needed for the functioning of a community (transportation, communication, water, power, schools, businesses, etc.)Heat island – an area where the temperature is several degrees higher than that of the surrounding areaWhen infrastructure replaces moist, permeable surfaces with dry & impermeable surfaces (pavement), a heat island effect occursThis “island” of hot air hovers over a city and affects local weather
32 2. Imported ResourcesCities have to import nearly all resources from areas outside the cityUrban areas rely on rural areas to supply resources such as food, water, building materials, fuels, etc. as well as land to provide ecosystem resources such as purification of water & air, matter cycling and waste treatmentLong-distance transport of resources to and from urban areas requires lots of fossil fuel.A world without cities would probably require more fossil fuels to allow people the same access to resources over scattered locations.
33 3. EfficiencyOnce resources arrive in a city, the city should be able to minimize per person resource consumption.People live closer, so less fuel and other resources to deliver resources and goods.High population density of cities allows for efficient distribution of any services (well, healthcare, education, power, sewer, waste disposal, public transportation,…)
34 4. Ecological Footprints Because cities get most of their resources from far away, their ecological footprints are greater than their actual land areas/size.Wealth & resource consumption are related, so urban & suburban residents tend to be wealthier resulting in a larger ecological footprint for themPositive: usually have universities & research centers, diverse residents (urban culture) is stimulating & innovative & possibly lead to ideas of how to reduce the negative impacts, and wealthy & educated urban residents buy more organic foods & goods which result in less negative impactsDensely populated cities leave more land outside cities left undeveloped (natural ecosystems)
35 SprawlSprawl – the spread of low-density urban or suburban development outward from an urban areaAs people move from cities to suburbs, population growth & increased land consumption per capita contribute to sprawlNatural areas and farms have disappeared as they have been cleared for housing developments & roadsIn some cases, expanding rings of suburbs surrounding cities have grown larger than the citiesMegalopolis – several large cities that sprawl together (Tampa/St. Petersburg, Boston/New York City
36 Contributions to Sprawl Two primary factors contribute to sprawl:Population growthIncreased per capita land consumptionThe degree of sprawl is a function of the increase in population of an area multiplied by the amount of land the average person lives onLos Angeles is the nation’s most densely populated urban area v.s. Detroit where sprawl was caused solely by land consumptionMost people prefer more space and privacy and dislike congestion, plus highways & technology have freed businesses from centralized infrastructure a city provides.
37 Patterns of SprawlUncentered Commercial strip Development – businesses are arranged in a long strip along a roadway with no central communityLow-density single-use residential development – homes are located on large lots in residential areas far from businessesScattered Development – residential developments are built far from a city center and are not integrated with one anotherSparse Street Network – roads are far enough apart that areas remain undeveloped but not far enough apart for these areas to function as natural areas
38 Impacts of SprawlPoliticians assume all growth is good as it attracts business, industry & residents leading to economic well-being, political power & cultural influence.Transportation – limited options, lack of mass transit on outskirts leads to driving cars, traffic accidents and greater use of fossil fuelsPollution – CO2 emissions from vehicles contribute to air pollution & global climate change, motor oil & salts pollute waterwaysPublic health – air pollution, physical inactivity, obesity, high BP, increased suicidesLand Use – more buildings & roads, less forests, fields, farmlands, wildlife habitats, recreation. Sprawl degrades/destroys these areas resulting in increased taxes to build facilities to replace these lost services
39 Impacts of Sprawl, continued 5. Zoning – the practice of classifying areas for different types of development and land use; gives control to planners for what can be built where, can restrict to single-use only or mixed use, can vitalize urban neighborhoods; involves gov’t restriction on use of private land, limits personal property rights 6. Urban Growth Boundaries – line that planners draw on a map to separate urban areas from areas the city would prefer to remain rural; goal is to concentrate development, prevent sprawl, and preserve orchards, ranches, forest & working farms; require less investment in infrastructure than sprawl, increases density of new housing, building “up not out” encourages development of urban centers v.s. sprawl 7. Smart Growth – philosophy of urban growth that focuses on economic & environmental approaches that lead to sustainable growth & avoidance of sprawl, focuses on revitalizing existing urban areas, waterfronts, and former industrial sites. “New urbanism” is happening at Celebration, FL and Seaside, FL (right)
40 Transportation Options Public transportation is a key factor in the quality of urban lifeMass transit use encouraged by: raising fuel taxes, tax fuel-inefficient modes of transportation, reward carpoolers, and encourage bicycle use & bus ridingSuccessful mass transit systems: Washington D.C., NY City, Boston, and San FranciscoParks and Open Space are key elements of livable cities; aesthetic as well as ecological functions (regulate climate, produce O2, filter air & water), community gardensEcological restoration – practice of restoring native communities, helps parks become sustainableGreenways – strips of vegetated open space that connect parks or neighborhoods, provide buffers
41 Unit 8C ReviewReal Data activity, page 302. Answer the 3 questions based on the Population Density v.s. Carbon Emissions data chartAnswer the following:Briefly describe how city planners use zoning, UGBs, smart growth, and new urbanism.How is a successful mass transit system important to improving the quality of life in a city?Give two reasons why open space is important to people who live in cities.Give two reasons why the progress toward sustainability in New York City and Curitiba, Brazil is important to the rest of the world (see page 313).
42 8D – Health & Hazards Chp. 9 (standards) Compare & contrast epidemiology & toxicology. Explain how they help us understand about how environmental hazards might affect our health.Know that individuals respond differently to all types of exposure due to their unique differences in age, sex, weight, health issues and genetic makeup.List 4 ways that infectious diseases are spread, methods used to reduce risk of exposure and monitor the outbreak.Describe some of the chemical hazards that are in our outside air, water & land. Explain their sources, how might be exposed, and the effects on our health.Describe the threat of bioaccumulation in organisms & give examples.Describe how natural disasters can affect our environment & our health.
43 Central Case: The Rise and Fall and Rise of DDT Page 255 and handoutAs a small group, do the Decision Making Model analysis of this case study.Define the problem, propose a solution, list 3 Pros, 3 Cons, 3 Short term consequences, 3 long term consequences, and then analyze your proposed solution.
44 Types of Environmental Hazards Biological – viruses, bacteria and other organisms that harm human health; pathogens (disease-causing agents) infect humans and make us sick (flu, strep throat, pet dander).Social – hazards that result from where we live, our jobs, or lifestyle choices; examples: smoking cigarettes, living next to a polluting factoryChemical – chemicals in the environment that harm human health; examples: synthetic chemicals, hazardous chemicals produced by organismsPhysical – natural disasters (tornados, droughts, earthquakes), natural phenomena (UV radiation)
45 Epidemiology and Toxicology Epidemiology - the study of disease in human populationsEpidemiologists – scientists who study how & where diseases occur and how to control them; look at large #s of cancer cases in a town, how a disease spreadToxicology - the study of how poisonous substances affect organisms’ healthToxicity looks at what the substance is and how much of it is needed to cause harmDose-response relationship – different doses and the responses they generate
46 The Role of the Individual Individuals respond differently to environmental hazards due to individual differences such as age, sex, weight, health issues, and genetic makeupSensitivity – people with health issues are often more sensitive to biological & chemical hazards; fetuses, infants, & young children tend to be more sensitiveGenetics – many diseases have both genetic & environmental factors; ex. – genetic mutations, exposure to ionizing radiation can increase cancer risksRisk assessment – the process of measuring risk to help make decisions about which hazards are harmful
47 Chp. 9.1 Review List the 4 types of environmental health hazards. How are epidemiology and toxicology similar? How are they different?Suppose two people smoke 5 cigarettes a day for 20 years. One develops lung cancer. Will the other person definitely develop lung cancer as well? Explain.What is risk management?Both a father and his child drink water that has flowed through lead pipes. There is also lead-based paint on the walls of their home. Over time, the child shows the effects of lead poisoning. The father does not. Explain how this could be possible.
48 Infectious DiseaseDiseases caused by a pathogen and spread three ways: by direct human contact, through contaminated food and water, and by animals.Humans – by touching, biting, sexual intercourse (STDs), contact with bodily fluids (HIV), inhaling expelled droplets (TB)Water or Food – cholera in water, salmonellaOther Organisms – passed on via vectors (disease- carrying organisms) such as ticks, mosquitoes when they bite humans
49 Emerging DiseasesDiseases that have appeared in the human population for the first time, or is increasing rapidly or spreading around the worldPandemic – outbreak that becomes widespread and affects a whole region, continent, or worldEx’s: west nile virus, MRSA, swine flu, EbolaEmerging diseases spread because of: increasing mobility, antibiotic resistance, changing environmentsWorld Health Organization helps respond to emerging diseases internationally; US Centers for Disease Control responds nationally
50 9.2 ReviewDescribe one way pathogens can spread through the environment.Why is it important to have an international organization such as WHO coordinating responses to emerging diseases?Describe 3 social hazards that are a result of choices you make every day.Do you think that modern medicine will ever eliminate biological hazards from Earth? Why or why not?
51 Toxic Substances in the Environment All chemicals can be hazardous in large enough quantities.A substance’s toxicity depends not just on what it is, but on how much of it a person is exposed to.Pollution – matter or energy that is released into the environment causing negative effects that impact people, wildlife, and other aspects of the environment.Oil from poison ivy can cause rashes on human skin (chemical hazard) but it is not a pollutant because it does not harm the environment.
52 Types of Chemical Hazards Carcinogens – chemicals that cause cancer; cells grow uncontrollably; cancer often has a genetic component, but there are a wide variety of environmental carcinogens; cigarette smokeChemical mutagens – chemicals that cause genetic changes or mutations; birth defects if sperm/egg cellsTeratogens – chemicals that harm embryos & fetuses; can cause birth defects; 1960s thalidomide babiesNeurotoxins – chemicals that affect the nervous system; include heavy metals, pesticides, chemical warfareAllergens – substances that overactivate the immune system; animal proteins, tobacco smoke, antibiotics; asthma is an inflammation of the respiratory systemEndocrine disruptors – chemicals that interfere with the endocrine system; hormones regulate growth, develop-ment, & sexual maturity; fetuses, infants & small children are at greatest risk
53 Indoor Chemical Hazards Indoor Air Pollution – air inside homes & buildings can contain chemical hazards; asbestos, radon, VOCsAsbestos – mineral that forms long, thin microscopic fibers used as an insulator; when disturbed, small fibers are released in the air and go into the lungsRadon – colorless, odorless, highly toxic radioactive gas; released naturally when uranium in rock, soil & water decays; can seep up from ground; lung cancerVOCs – volatile organic compounds; released from plastics, perfumes, pesticides, formaldehydeCarbon Monoxide – colorless, odorless gas; leaky stoves, car exhaust, tobacco smokeLead – exposed through the air, drinking water (lead pipes, solder), soil, lead-based paint, dust
55 Outdoor Chemical Hazards Chemical Hazards in Air – come from both natural & human activity; winds carry chemicals far away from their original source (“pesticide drift”); contribute to millions of premature deaths each year; tough lawsChemical Hazards on Land – chemicals get into the soil in many ways: pesticides, improper disposals; soil toxicants can be absorbed, inhaled, ingested or picked up by water that runs off the landChemical Hazards in Water – many chemicals are soluble in water & enter tissues through drinking or absorption; aquatic animals are effective indicators of pollution; water can pick up toxic chemicals when it runs off land - oil leaks, storm drains
57 BiomagnificationToxic chemicals accumulate in organisms as they feed on one another, moving up the food chain concentratedHow long a chemical lasts or persists in the environment can be a major concernOrganisms absorb, breathe & ingest toxic substances from their environment, some end up stored internallyDDT accumulates in fatty tissues, methylmercury can be stored in muscle tissuePredators consume prey, including all of their stored toxic chemicals, and store the chemicals themselves in a concentrated form; ex – DDT in 1940s-60s moved up the food chain, eventually affecting eagles & ospreys
58 9.3 Review Explain the phrase “The dose makes the poison.” List 2 types of chemical hazards that affect human health.Name one indoor chemical hazard and describe how it can affect human health.A pollutant released on one continent is found concentrated in the tissues of organisms on another continent. Is this likely an air, land, or water pollutant? Explain.Describe the process of biomagnification.A farmer decides to use a new pesticide on her fields to combat some new pests. She continues to apply it for several years. Over time, a neighbor notices that there are fewer & fewer big fish in a nearby pond. She can’t think of any explanation, so she notifies scientists at a local university. The scientists look into the issue and find that high levels of the pesticide have accumulated in the fishes’ tissues. Describe how this might have occurred.
59 Natural DisastersForces of Earth, wind, and water can quickly and completely disrupt our livesNatural disasters are physical hazards that occur naturally in the environment and pose health hazardsEarthquakes, volcanic eruptions, violent stormsSome common practices by man increase our vulnerability to certain physical hazards, such as deforesting slopes makes landslides more likely and damming rivers makes flooding more likely in some areas. We can reduce risk from such hazards by improving our forestry and flood control practices, and choosing not to build in areas prone to hazards.
60 EarthquakesThe shaking that occurs during an earthquake can destroy natural landforms as well as human-made structures.As tectonic plates scrape against each other, sometimes they get stuck & stress builds up & energy is released when they finally move.Surface effects – ground sinks & soil liquefies, setting off landslides; earthquakes at the bottom of the ocean can set off a tsunamiStructural damage and human life is very costlyIn the U.S., Alaska and California have the most earthquakes. Precautions must be taken in high risk areas.
61 VolcanoesThe molten rock, gas, ash & cinders released during a volcanic eruption can cause significant damage & loss of life in nearby cities & towns.Molten rock/lava that surfaces can cover large areas of land, destroying what was once there.Clouds from extreme volcanic eruptions can block the sun’s rays & cause global temperatures to drop.Eruptions can also trigger landslides & mudflows.Scientists monitoring tectonic activity can try to predict when a volcano will erupt, giving advance warning that saved 70,000 people in the Philippines in 1991 when Mount Pinatubo erupted.
62 StormsTornadoes, hurricanes, and thunderstorms are powerful weather events that can damage property & threaten human lives.Tornadoes – a type of windstorm in which a funnel of rotating air drops down from a storm cloud & touches Earth’s surface; funnel wind speeds can reach over 250 mph; deadly; take shelterHurricanes – powerful storms that form over the ocean in the tropics; produce winds of at least 74 mph; high winds, heavy rain, and a storm surge (dome of water that crashes along the coast where the hurricane hits); destroy buildings, wash away beaches, blow away trees, and cause severe flooding.Thunderstorms – storms that produce both lightning & thunder, heavy rain, & sometimes hail; cause flooding, take down power lines & trees, and hail damage to crops; lightning can start fires and kill people & animals
63 AvalanchesAn avalanche is a mass of sliding snow down a slope that can bury people and places in its pathCertain conditions create the potential for avalanches: slopes greater than 30º, unstable snowpacks (a layer of hard, strong snow sits on top of soft, weak snow), weather (heavy snows and warm temperatures and periods of melting and refreezing).Damage includes burying both people and places, block roads and railroad tracks, and damage lines & bridgesIf you do get caught, try to stay near the surface or swim up through the sliding snow as best you can, stay calm and try to conserve any air you have.
64 9.4 Review What is a landslide? Name some ways a volcanic eruption can damage property.How are hurricanes and tornadoes similar? How are they different?Why do you think it is important to stay calm if you are caught in an avalanche?Suppose you are in a car driving through a new town. The national weather service issues a tornado warning for this area. At the same time, you notice the weather looks threatening. What might you do?