ATMOSPHERE THE LAYERS OF GASES THAT SURROUND THE EARTH

COMPOSITION:78% Nitrogen21% Oxygen1% Other

GasesLower atmosphere is a

mixture of many gases called air

Remains the same until about 80km altitude

Above 80km air is extremely thin, almost a vacuum

99% of the atmosphere’s weight is within 32km of the surface

CHANGES IN THE EARTH’S ATMOSPHERE

When earth was formed volcanic eruptions released gases such as CO2

called outgassing produced a poisonous atmosphere

About 2.5 bya cells began photosynthesis Photosynthesis produces oxygen as a waste product

Over millions of years the atmosphere filled to it’s current levels of oxygen

WHAT ELSE IS IN THE ATMOSPHERE: WATER VAPOR, OZONE AND DUST

Water vapor enters the air through evaporation and transpirationOzone - a molecule of oxygen that has 3 oxygen atoms (O3) Forms when ultra violet (UV) rays act on oxygen in the upper atmosphere Ozone absorbs 99% of harmful UV raysDust includes tiny grains of rock, dirt, pollen, soot, chemicals and

bacteria

ATMOSPHERIC PRESSURE:• The pressure exerted on a

surface by the atmosphere• Decreases as altitude increases• Measured using a barometer

Units of measure:AtmospheresMm or inches of mercury Millibars

1 atmosphere = 760 mm Hg = 1000 mb

LAYERS OF THE ATMOSPHERE:

a) Troposphereb) Stratospherec) Mesosphered) Thermosphere

http://www.youtube.com/watch?v=FHtvDA0W34I

STRUCTURE OF THE ATMOSPHERE Divided into five layers based on temperature changes

Troposphere – 0 – 18 km Closest to the earth Weather occurs here Boundary of the troposphere is the tropopause

Stratosphere – 18 - 50 km Clear and dry Contains the ozone layer Very little water vapor

TROPOSPHERE:• Temperature decreases as

altitude increases because its heated by Earth’s surface

STRATOSPHERE:• As altitude increases temperature

increases because UV rays absorbed by ozone

STRUCTURE OF THE ATMOSPHEREMesosphere – 50-80 kmGets colder with increasing altitude Coldest temp in atmosphere in this layer (-80°C)

Thermosphere — 80-480 kmVery hot (980°C)*The Ionosphere – in the lower thermosphere and upper mesosphere

where electrically charged ions are formed These ions reflect radio signals back to earth

AURORA BOREALIS

http://www.youtube.com/watch?v=MfPXLfkmQss

MESOSPHERE:

• Temperature decreases as altitude increases

THERMOSPHERE:• As altitude increases temperature

increases because oxygen and nitrogen atoms absorb solar radiation

EXOSPHERE – ABOVE 500KM

Outermost layer of atmosphere

Very few gas particlesNo clear boundary between exosphere and space

Very low temperature