Chapter 18Chapter 18Human Impact Human Impact on the Earthon the Earth

Human Impact on the EarthHuman Impact on the Earth

WaterWaterAirAirSoilSoil

Our Water ResourcesOur Water Resources The The water cyclewater cycle is the is the

continuous movement of water continuous movement of water above, on, and below the Earth’s above, on, and below the Earth’s surface. It includes:surface. It includes:

PrecipitationPrecipitation•RunoffRunoff•EvaporationEvaporation•CondensationCondensation

Our Water ResourcesOur Water Resources PollutionPollution is the introduction of is the introduction of

harmful substances into the harmful substances into the environment.environment.

Point-source pollutionPoint-source pollution is is pollution that comes from a pollution that comes from a single or easily tracedsingle or easily traced point (such point (such as a pipe).as a pipe).

Our Water ResourcesOur Water Resources Nonpoint-source pollutionNonpoint-source pollution is is

pollution that comes from many pollution that comes from many places rather than a single point.places rather than a single point.

It comes from places like yards, It comes from places like yards, parks, farms, streets, and storm parks, farms, streets, and storm sewers and reaches bodies of water sewers and reaches bodies of water via runoff.via runoff.

Our Water ResourcesOur Water Resources 65% of the Earth is water – but only 65% of the Earth is water – but only

3% of that water is drinkable.3% of that water is drinkable.

Freshwater pollution comes from:Freshwater pollution comes from:• Fertilizer runoffFertilizer runoff• Bacteria from wasteBacteria from waste• Waste from factoriesWaste from factories• PesticidesPesticides

Our Water ResourcesOur Water Resources The The Clean Water ActClean Water Act had a goal to had a goal to

make all surface water in the US safe make all surface water in the US safe enough for swimming and fishing by enough for swimming and fishing by 1983.1983.

We have made progress – but that We have made progress – but that goal has still not been met.goal has still not been met.

Our Water ResourcesOur Water Resources Our oceans are also polluted, the Our oceans are also polluted, the

most common sources being:most common sources being:• TrashTrash• Sludge dumpingSludge dumping• Oil spillsOil spills

The US spends more than $130 The US spends more than $130 million a year to protect the ocean million a year to protect the ocean and beaches.and beaches.

The Air We BreatheThe Air We Breathe Primary pollutantsPrimary pollutants are pollutants are pollutants

that are put directly into the air by that are put directly into the air by human or natural activity.human or natural activity.•Exhaust, volcanic ash, smoke sootExhaust, volcanic ash, smoke soot

Secondary pollutants Secondary pollutants form from form from chemical reactions.chemical reactions.•SmogSmog

The Air We BreatheThe Air We Breathe Acid rainAcid rain is rain, sleet, or snow is rain, sleet, or snow

that is highly acidic because of that is highly acidic because of the burning of fossil fuels.the burning of fossil fuels.

The The ozone holeozone hole formed when formed when some chemicals added to the air some chemicals added to the air reacted with the ozone layer.reacted with the ozone layer.

The Air We BreatheThe Air We Breathe

The The Clean Air ActClean Air Act allows the allows the Environmental Protection Agency Environmental Protection Agency (EPA) to control the amount of (EPA) to control the amount of pollutants that can be released pollutants that can be released from any source.from any source.

Saving Our SoilSaving Our Soil ErosionErosion is the process by which is the process by which

wind and water move soil from wind and water move soil from one place to another.one place to another.

There are three types:There are three types:•Sheet erosionSheet erosion•Rill erosionRill erosion•Gully erosionGully erosion

Saving Our SoilSaving Our Soil Human causes of erosion:Human causes of erosion:

DeforestationDeforestation or the process of or the process of clearing forests.clearing forests.

OvergrazingOvergrazing removes large areas of removes large areas of grassland.grassland.

FarmingFarming breaks up the soil. breaks up the soil.

Saving Our SoilSaving Our Soil DesertificationDesertification is a process is a process

by which human activity by which human activity makes the soil infertile in makes the soil infertile in areas where plants could once areas where plants could once grow.grow.

Saving Our SoilSaving Our Soil Soil conservationSoil conservation is the is the

methods by which humans take methods by which humans take care of the soil.care of the soil.

Some examples are:Some examples are:•Contour farmingContour farming•Strip farmingStrip farming•WindbreaksWindbreaks