1. Global Geography 12 Unit 2 – The Planet Earth

2. The BIG Question… Why is Earth able to sustain life?

3. Four Main Reasons…  Stable temperature range  Abundance of water  Gases to sustain life (oxygen, nitrogen and carbon dioxide)  Atmosphere that protects us from UV radiation

4. So what does this mean?

5. How is Earth able to keep a stable temperature?  Greenhouse effect Greenhouse effect  Energy comes in through the atmosphere and is transformed into heat, mostly by the earth’s surface. The gases (CO2 and water vapour) in the atmosphere keep much of this heat from escaping.  Animation Animation  Plant cover, particularly large forests  Plants have an influence over the amount of water vapour and CO2 in the atmosphere.  Helps the surface absorb radiation and create heat, not reflect it back as light.  Circulation in the atmosphere  Different areas of the world get different amounts of energy but circulation of the atmosphere helps even this out.

7.  BUT, the temperature isn’t the same everywhere on Earth. Can we still have life?  Temperature RANGE  What DOES impact temperature?  Intensity and duration of energy from the sun  Altitude  Proximity to large bodies of water  Prevailing winds  Aspect (which direction you are facing)  Albedo effect Albedo effect  Diagram Diagram

8. Seasons CAN affect temperature

9. What can we tell from this diagram?  Days are longer in the summer and shorter in the winter because of the tilt of the earth.  When days are long in the north, they are short in the south.  This corresponds with the level of intensity… the angle of the sun’s rays is lower in the winter than in the summer.

10. 2 nd Reason Earth Can Sustain Life…  An abundance of water!  Where, on Earth, do we find water?

12. Why is an abundance of water important to life on earth?  Absorbs heat and distributes it through ocean currents  Reservoir for water vapour  Dissolves and distributed nutrients in the soil  Is essential for living things…humans are 70% water and many of our bodily functions require it. Needed for photosynthesis.

13. 3 rd Factor – Gases that sustain life  Text, page 46  What gases make up our atmosphere? (by percent)  How did our atmosphere change over time?  How do the gases in our atmosphere support life?

14. 4 th Factor – Atmosphere that protects  Examine the website below:  http://airs.jpl.nasa.gov/m aps/satellite_feed/atmos phere_layers/  Draw a diagram illustrating the different levels of the Earth’s atmosphere. Include in your diagram the events that are most likely to happen at each level. Be sure to explain the function of each layer in your own words.  This photograph of the colorful layers of Earth's upper atmosphere was taken from the space shuttle, looking sideways across Earth's atmosphere. Image Credit: NASA

15. Ozone Layer  One of the most famous parts of the atmosphere…the ozone layer  Short National Geographic VideoVideo  BUT, more on the Ozone Layer to come…