1. Characteristics of the Atmosphere 22.1

2. The Atmosphere has Five Important Layers Troposphere Stratosphere Mesosphere Ionosphere Thermosphere

3. Troposphere The layer closest to the Earth’s crust The layer closest to the Earth’s crust Where the clouds, wind & rain occur Where the clouds, wind & rain occur Gets colder as altitude increases Gets colder as altitude increases Inversions: warm air sits above cold air. Inversions: warm air sits above cold air. Pair share: A tell B why inversions make city smog worse.

4. Stratosphere Layer above the troposphere Cool & low pressure Contains Ozone layer O 3 molecules absorb UV radiation from sun Protects life

5. Ozone “hole” Use of CFC’s have caused a thinning of the ozone layer Results: more cancer-causing rays hit earth Pair share: B tell A where the ozone is thinnest and where it is thickest.

6. Ionosphere Between the Mesosphere & Thermosphere Mesosphere is the coldest layer Thermosphere is the hottest layer Radio waves bounce off ionosphere: reflects them Aurora borealis Pair share: A tell B what therm, meso, & sphere mean.

7. Aurora borealis Auroras circle the earth’s magnetic poles It’s caused by energy from sun exciting ions That release photons of light

8. Changes over time Early Earth’s atmosphere was toxic Anaerobic bacteria were the only organisms on Earth 3.5-2.5 Billion Years ago Gases: only 1% O 2 a lot of: H 2 O, CH 4, H 2, N 2, CO, CO 2 Pair share: B tell A if people could survive an atmosphere like that and why

9. Change of the Earth’s Atmosphere Over time bacteria using CO 2 released O 2 into the air Over time bacteria using CO 2 released O 2 into the air This made it possible for aerobic bacteria & other organisms to thrive on Earth This made it possible for aerobic bacteria & other organisms to thrive on Earth Now the Atmosphere is 21% Oxygen Now the Atmosphere is 21% Oxygen Archaea bacteria: first life forms, oxygen producers Aerobic bacteria: first life forms to use oxygen

10. Notebook Review 1)Which layer of the atmosphere do the clouds reside? 2) What caused the thinning of the ozone layer? 3) What organisms increased the amount of 0 2 in the air?

11. Summary Main idea Main idea Important ideas / topics Important ideas / topics key facts key facts How the facts relate to the main idea How the facts relate to the main idea