Earth’s Changing Atmosphere

Main Topics• Definition and Characteristics of the Atmosphere• Changes to the Atmosphere composition• Layers of the Atmosphere Characteristics• How the Earth gets its energy / heat• 3 Types of Heat Transfer

– Radiation, Conduction, Convection

• Forms of Radiation• Ozone Layer• Greenhouse Effect

The Atmosphere makes life on Earth possible

• Atmosphere –The whole layer of air that surrounds

Earth–A mixture of gasses–Keeps Earth warm–Protects life

The atmosphere protects life by:• Absorbing harmful radiation• Maintaining Earth’s temperature• Providing elements essential for life

Characteristics of the Atmosphere

• Altitude - the distance above sea level

• Density - the amount of mass in a given volume

– The density of the atmosphere decreases with altitude

– Most of the mass of the atmosphere is close to Earth’s surface

Materials in the Atmosphere

GasGas PercentPercent

Nitrogen (NNitrogen (N22)) 78.0878.08

Oxygen (OOxygen (O22)) 20.9420.94

Argon (Ar)Argon (Ar) 0.980.98

Carbon Dioxide (COCarbon Dioxide (CO22)) 0.040.04

Other ElementsOther Elements 0.010.01

Water Vapor (HWater Vapor (H22O)O) 0-10-1

Gases of Earth's Atmosphere

Natural Processes modify the atmosphere

• The exact amounts of some gases in the air (atmosphere) change depending on: –Location–Time of day –Season–Other factors

Sudden Changes

• Dramatic events may cause a change in the atmosphere

• It may take a long time for the atmosphere to restore balance

• Examples– Volcanic Eruptions – Forest Fires– Dust Storms

The atmosphere has temperature layers

• Density changes with altitude• Temperature changes with altitude• Pattern of temperature changes defines

different layers

Layers of the atmosphere

• Troposphere • Stratosphere• Mesosphere• Thermosphere• Exosphere

The Layers

Troposphere• Lowest layer• Decreases in Temperature• Includes weather, birds, clouds

Stratosphere• 2nd Layer• The lower end of it is extremely cold

– Temperature increases

• Ozone, weather balloon, and planes are found here

Mesosphere

• 3rd layer• Temperature decreases• Very strong winds• Very little information

about layer• Contains meteors

Notice the temperatures

Thermosphere• 4th Layer• Temperature increases• Very thin• Contains the Aurora Borealis, space

crafts

Exosphere

• Last Layer–Not always considered a layer…still

debated

• Gradually fades into the vacuum that is space………

• Contains satellites

How does the Earth get heated?

• Energy transfer from the sun

Energy

• The ability to do work or cause change• Temperature

– The average amount of energy of motion of each molecule (the measure of how hot or cold something is)

• Gas– Moving particles, the hotter they get the

faster they move

The atmosphere moves energy

• Energy moves by heat transfer• There are 3 types of heat transfer

– Radiation– Conduction– Convection

Radiation• The transfer of the Sun’s energy to the Earth’s

surface• Solar radiation heats both the surface and the air

– Includes visible light• Earth’s surface gives off a type of invisible radiation

called Infrared radiation

Earth’s absorption of Radiation• 30% of incoming solar energy is reflected by clouds• 70% is absorbed and becomes different forms of

energy– Absorbed by oceans, landforms, and living things

(photosynthesis and respiration)

• This absorbed energy heats the Earth’s surface

Conduction

• The transfer of heat energy from one substance to another through DIRECT contact

• The Earth’s surface heats the air (gas) molecules directing above it

• Molecules of air gain energy when they collide with the molecules in grains of hot sand.

Convection

• Transfer of energy from place to place by the motion of gas or liquid (fluids)

• Up and down movement of molecules not the side to side movement

Density and Convection

• The atmosphere gets less dense at higher altitudes

• Warm air is less dense than cold air– Warm air has more energy, so

molecules move faster than cold ones– This makes them collide more, then

they spread out– More space between molecules = less

dense

Transfer of Energy

Gases Absorb and Give Off Radiation

The Atmosphere affects light in 4 ways.1. Absorbs Light2. Reflects Light3. Lets Light Pass Through4. Emits (Gives Off) Light

On sunny days more visible light gets to the earths surface.

On cloudy days clouds reflect and absorb most of the sunlight

Forms of Radiation We Cant See

• Ultraviolet Radiation– More energy than the light

you can see– Can cause sunburns and

other damage

• Infrared Radiation– Less energy than the light

you can see– Warms the materials that

absorb it

Ozone Layer Protects Life• Ozone - O3

– Ozone in stratosphere is called the ozone layer

– Protects life on Earth– Absorbs harmful ultraviolet

radiation from sun• Too much can cause

sunburn, skin cancer, and can harm crops, plastic or paint

– Lets other types of radiation like visible light through

Greenhouse Effect• Keeps Earth Warm• Slow the movement of energy away from the Earth’s

surface• Greenhouse gases

– Includes carbon dioxide, methane, water vapor, and nitrous oxide

– Gases mix with gases in the air like nitrogen and oxygen. Not its own layer

– Found in the troposphere– Absorbs and emits infrared radiation

Animation