CH. 15-1CH. 15-1

EARTH’SEARTH’S

ATMOSPHEREATMOSPHERE

ImportanceImportanceAtmosphere – a thin layer Atmosphere – a thin layer

of air that forms a of air that forms a protective covering around protective covering around Earth.Earth.

It keeps Earth’s It keeps Earth’s temperature in a range that temperature in a range that can support life.can support life.

ImportanceImportance It also protects life-forms It also protects life-forms

from some of the Sun’s from some of the Sun’s harmful rays.harmful rays.

Makeup of Atmos.Makeup of Atmos. It is a mixture of solids, It is a mixture of solids,

liquids, & gases that liquids, & gases that surround the planet.surround the planet.

Gases in the Atmos.Gases in the Atmos.Nitrogen = 78%Nitrogen = 78%Oxygen = 21%Oxygen = 21%COCO22 = 0.03%, but could be = 0.03%, but could be

increasing due to burning increasing due to burning fossil fuels for energy.fossil fuels for energy.

Layers of the Atmos.Layers of the Atmos.5 layers make up Earth’s 5 layers make up Earth’s

atmosphere:atmosphere:Troposphere & Troposphere &

StratosphereStratosphereMesosphere, Mesosphere,

thermosphere, & thermosphere, & exosphereexosphere

Lower LayersLower LayersTroposphere - the lowest Troposphere - the lowest

layer of Earth’s layer of Earth’s atmosphere.atmosphere.

Extends up about 11 mi or Extends up about 11 mi or 10 km10 km

Contains clouds, rain, & Contains clouds, rain, & snow.snow.

Lower LayersLower LayersStratosphere is directly Stratosphere is directly

above troposphereabove troposphereExtends from 10 km – 50 Extends from 10 km – 50

km abut Earth’s surfacekm abut Earth’s surfaceContains a gas called Contains a gas called

ozone (Oozone (O33))

Upper LayersUpper LayersMesosphere – extends Mesosphere – extends

from top of stratosphere to from top of stratosphere to about 85 km above Earth about 85 km above Earth

Shooting stars (meteors) Shooting stars (meteors) occur hereoccur here

Upper LayersUpper LayersThermosphere – the Thermosphere – the

thickest layer of the thickest layer of the atmosphere (between 85 atmosphere (between 85 km & 500 km) above Earth. km & 500 km) above Earth.

Very hot! Temps. can reach Very hot! Temps. can reach 2000 degrees!2000 degrees!

Upper LayersUpper Layers IonosphereIonosphere is a layer of is a layer of

electrically charged electrically charged particles found within the particles found within the thermosphere.thermosphere.

Absorbs AM radio waves Absorbs AM radio waves during day, reflects them at during day, reflects them at night.night.

Upper LayersUpper LayersExosphereExosphere – last (highest) – last (highest)

layer of the atmospherelayer of the atmosphereExtends more than 500 km Extends more than 500 km

above Earth (very cold)above Earth (very cold)Marks the transition from Marks the transition from

Earth’s atmosphere to Earth’s atmosphere to outer space.outer space.

Atmospheric PressureAtmospheric PressureEarth’s gravity pulls Earth’s gravity pulls

atmospheric gases toward atmospheric gases toward its surface, & the weight of its surface, & the weight of the gases presses down on the gases presses down on the air below.the air below.

Air pressure decreases Air pressure decreases with height.with height.

Ozone LayerOzone LayerLies within the Lies within the

stratosphere.stratosphere.Blocks Sun’s harmful Blocks Sun’s harmful

energy (UV radiation) energy (UV radiation) which is very important to which is very important to us.us.

UV = Ultraviolet UV = Ultraviolet

CFCsCFCs CFCs - chlorofluorocarbonsCFCs - chlorofluorocarbons They destroy ozone by the They destroy ozone by the

chlorine combining with one chlorine combining with one of the oxygen atoms in ozone.of the oxygen atoms in ozone.

Allows more UV light to reach Allows more UV light to reach the Earth. the Earth.

CFCsCFCs CFCs are found in Freon CFCs are found in Freon

(used to cool refrigerators, air (used to cool refrigerators, air conditioners) & aerosol spray conditioners) & aerosol spray cans (hair spray & spray cans (hair spray & spray paints) paints)

One atom of chlorine can One atom of chlorine can destroy 100,000 ozone destroy 100,000 ozone molecules!!molecules!!