7.5 Composition and Structure of the Atmosphere What is the composition of Earth’s Atmosphere? SC.6.E.7.9, LA.6.2.2.3

Total of just these 2 gases = 99 % Less than 1% Carbon Dioxide, (CO2) Composition of Earth’s Atmosphere The atmosphere is the protective covering of Earth. It keeps Earth warm and protects it from harmful sun rays.   The composition of the mixture of gases that we call the atmosphere is:   Nitrogen (N) 78% Oxygen (O2) 21% Total of just these 2 gases = 99 % Less than 1% Carbon Dioxide, (CO2) Argon, (Ar)&other trace gases BTW – what is the most abundant element in our earth’s soil? OXYGEN!!!!!!

Which circle graph shows the correct Composition of the atmosphere—page 261 Main Gases in Air

Composition Continued Water Vapor: water in the form of a gas can be found in the air. The amount of water vapor in the air is different from place to place and time to time. Particles: Tiny solid particles of dust, smoke, salt, and chemicals found in the air. BTW – where does most of the dust in your house come from?

Draw arrows showing which direction air density decreases / temperature increases.

How did you draw your arrows? As you rise into atmosphere, the Density of air DECREASES And as you sink the Temperature of the air INCREASES

* Thermosphere * Mesosphere * Stratosphere * Troposphere 4 Main Layers These layers are classified according to changes in temperature. * Thermosphere * Mesosphere * Stratosphere * Troposphere Atmosphere Video Clip

The Troposphere! Lowest layer We live here Weather occurs About 12 km thick (WBMS-Navarre Post Office) (10 K = 6.2 miles – a typical race distance) So 12 km = about 7.5 miles thick varies from 9 km (at the north and south poles) To about 16 km (at the equator) Shallowest, but MOST dense As altitude ↑ The Temperature ↓

The Stratosphere Ozone layer is here. What is Ozone? 2nd layer: Extends from top of Troposphere to ~50 km (WBMS to Destin Commons) Ozone layer is here. What is Ozone? Ozone has 3 atoms of Oxygen, not just 2 Lower Stratosphere is cold, about ⁻60˚C Upper Stratosphere is warmer than lower Why? Middle of Stratosphere is where Ozone layer is it absorbs energy and warms the air. The Ozone layer also protects us from UV radiation from the sun.

The Mesosphere Middle Layer 50-80 km above Earth (WBMS to Florabama) Temperatures approach ⁻90˚C (-130 F) Protects us from meteoroids – where meteors first encounter friction from gases in atmosphere.

The Thermosphere Outermost layer of the atmosphere Above 80 km Temperatures up to 1800˚C (3,272 F) because sunlight strikes it first Doesn’t feel warm though, because the molecules are far apart Auroras happen here Ionosphere—is the lower layer of the Thermosphere Exosphere—is the outer layer from 400 km to thousands of kilometers