The Atmosphere

B1: Layers of the Atmosphere

The Atmosphere• Atmosphere – Blanket of gases that surround

the Earth

– Layers:and ThermosphereTroposphere,Stratosphere,Mesosphere,

• Troposphere – lowest layer of Earths atmosphere

– Layer in which most living organisms exists– Layer in which Earth’s weather occurs–Weather – the condition of Earth’s

atmosphere at a particular time and place

– Scientists have divided the atmosphere into four main layers classified according to changes in temperature

Layers of the Atmosphere

– Contains most of the gas and water vapor

– Temperature decreases as the altitude increases

TroposphereLive

WeatherMass

–Depth ranges from about 5 to 10 miles thick

– It is the smallest layer, yet it contains almost all of the atmosphere’s mass

Layers of the Atmosphere• Stratosphere – Second layer of the

atmosphere and contains the ozone layer– It is about 21 miles thick

–Ozone Layer – found in the lower portion of the stratosphere–Ozone is a form of oxygen gas containing

3 oxygen atoms per molecule

– Important because it filters out most of the ultra-violet (UV) radiation from the sun

– Air is too thin for anything but bacteria to survive

Layers of the Atmosphere

TroposphereLive

WeatherMass

– Sometimes planes will fly in the lowest portion–Optimizes fuel burning and

the thinner air means less air drag (resistance)

It also allows them to fly above bad weather

Stratosphere

Ozone

Thin Air

Layers of the Atmosphere• Mesosphere – Third layer of the atmosphere

– It is about 30 miles thick–Meteors – layer of the atmosphere that

protects us from small meteors– About 40 tons of meteor collide with the

Earth each day–Most are small and burn up when they

impact the particles in the mesosphere

– It is the coldest layer of the atmosphere,

about -90o C (-130o F)

–On Earth they appear as “shooting stars”

Layers of the Atmosphere

TroposphereLive

WeatherMass

– At the north and south poles, noctilucent clouds form in this layer

– Are made of ice crystals and not associated with weather

Stratosphere

Ozone

MesosphereColdest

Thin Air

Stops Meteors

X

Layers of the Atmosphere• Thermosphere – Outer most layer of the

atmosphere and contains the ionosphere– It is over 100 miles thick and extends into space

– Ionosphere – layer where gas particles are ionized by solar radiation– Radiation causes gas particles to loose

electrons and become ions

–When free electrons reunite with molecules, they give off light

– It is the hottest layer of the atmosphere

– Air is extremely thin and gradually fades out

with a temperature about 2,000o C (3,600o F)

Layers of the Atmosphere

TroposphereLive

WeatherMass

– Process occurs most often at the north and south poles

– In the northern hemisphere the brilliant light display is called the Aurora Borealis, or ‘Northern Lights’

Stratosphere

Ozone

MesosphereColdest

Thin Air

Stops Meteors

ThermosphereHottest

Ionosphere Aurora Lights

X

Composition of the Atmosphere

• Composition – Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases as well as particles of liquids and solids–Nitrogen – About 78% of the air

surrounding us is made of nitrogen

– Essential to life because it is a key element in the formation of amino acids

–However, atmospheric nitrogen must first be convert before it can be used (nitrogen cycle)

Composition of the Atmosphere

– Plants and animals require oxygen to release energy from their food

–Oxygen – About 21% of the air surrounding us is made of oxygen

– Also required for other processesfor example:

–Ozone is a form of oxygen with 3 oxygen atoms

– Breathing ozone is harmful to humans

– Can cause chest pain, coughing, throat irritation, asthma, emphysema, and permanently scar lung tissue

burning fuel, wood, and even candles

Composition of the Atmosphere

–Argon – 1% of the air surrounding us is made of argon– An inert gas (does not react chemically to other

elements, gases, metals, or even acids)

–Used in incandescent and florescent light bulbs

and in welding

Composition of the Atmosphere

–Carbon Dioxide – Less than 1% of air carbon dioxide

– Essential to life since plants require it to produce food

– It is produced when plants and animals break down food

–When burning fuel, CO2 is also produced

–However, increases in CO2 levels has impacted global warming

– CO2 is a heat-trapping greenhouse gas

Composition of the Atmosphere

–Other Gases – Called trace gases since only a very small amount of them are present

– Plays an important role in Earth’s weather– The amount of water vapor in the air is

called humidity

–Water Vapor – An invisible gas made of 2 hydrogen and 1 oxygen atom (steam is NOT water vapor)

–When water vapor cools and condenses, it forms tiny droplets or crystals which create clouds

If they become large or heavy enough, it will rain or snow

Composition of the Atmosphere

–Particles – In addition to gases, air also contains particles

– The particles can be solid or liquid

– Types of particles include: dust, smoke, chemicals, and more.

In Closing–Why is the atmosphere essential for life to

exist on Earth?