Layers of the Atmosphere Chapter 12, Section 3

Ch12 S3: Essential Questions What are the four main layers of the atmosphere? What are the characteristics of each layer?

Earth’s atmosphere is divided into four main layers based upon changes in temperature.

Layers of the atmosphere

Troposphere Lowest layer of the atmosphere (closest to Earth) You live here Tropo means turning or changing (there is more change in this layer than any other) Weather occurs here Shallowest layer (thinnest) Contains almost all the mass of the atmosphere It is 16 km thick at equator and less than 9 km thick at poles As altitude increases, temperature decreases At the top, temp is about -60 ̊C. Water here forms clouds of ice

Stratosphere Second layer of the atmosphere Reaches from troposphere to about 50 km above surface of Earth Strato means layer or spread out Ozone layer is here (remember it protects living things from ultraviolet radiation from Sun) Jets often fly here because it is calm As altitude increases, temperature increases (because ozone layer absorbs heat)

Compare how much UV-B is blocked by the ozone layer Compare how much UV-B is blocked by the ozone layer. Notice no UV-A is blocked by it.

Mesosphere Third layer Meso means middle Reaches from 50 km to 80 km above Earth’s surface Protects Earth’s surface from being hit by meteoroids (chunks of stone and metal from space – but some still get through) A shooting star is a trail of hot, glowing gases a meteoroid leaves behind in the mesosphere Coldest layer - Temperatures reach – 90 ̊C at the top of the mesosphere As altitude increases, temperature decreases

Asteroid grazing Earth’s atmosphere

Thermosphere Outermost layer of our atmosphere Reaches from 80 km above Earth’s surface into outer space. There is no definite upper limit Thermo means heat Thickest layer Hottest layer, temperatures reach up to 1,800 ̊C, but you would not feel warm here (Find out Why?) As altitude increases, temperature increases Has two other layers

Ionosphere Lower layer of the Thermosphere Reaches from about 80 km to 400 km above Earth’s surface Energy from the sun causes gas molecules here to become electrically charged particles Radio waves bounce off ions back to Earth (makes signals travel much farther at night) Auroras happen near the poles because of the ionosphere – these are brilliant streaks of light in night skies

Exosphere Exo means outer Is the outer portion of the thermosphere Reaches from about 400 km outward for thousands of kilometers Space shuttles and satellites orbit Earth here

Remember: Earth’s atmosphere is divided into four main layers based upon changes in temperature.

- Layers of the Atmosphere

Can you pick out what might be the layers?

Review Quiz List the four main layers of the atmosphere in order from the surface of Earth. What is the hottest layer of the atmosphere? a. Troposphere b. Stratosphere c. Mesosphere d. Thermosphere

Quiz (continued) What layer do you live in? Troposphere b. Stratosphere Mesosphere d. Thermosphere What layer contains the ozone layer?

Ch12 S3: Essential Questions Answered What are the four main layers of the atmosphere? Troposphere, stratosphere, mesosphere, thermosphere

What are the characteristics of each layer? Troposphere: weather happens here, we live here, thinnest layer, lowest layer. Stratosphere: ozone layer and jet stream are here. Mesosphere: coldest layer, shooting stars happen here. Thermosphere: thickest, hottest layer.

Stop Here

Temperature The average amount of energy of motion of each molecule of a substance In the thermosphere the molecules are spaced far apart in the thin air, so there are not enough of them to collide with a thermometer and warm it very much In the thermosphere, an ordinary thermometer would show a temperature well below 0 ̊C Back