Global Geography 12Unit 2 – The Planet Earth

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

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

So what does this mean?

How is Earth able to keep a stable temperature?

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 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.

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

Diagram

Seasons CAN affect temperature

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.

2nd Reason Earth Can Sustain Life…

An abundance of water!

Where, on Earth, do we find water?

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.

3rd 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?

4th Factor – Atmosphere that protects

Examine the website below: http://airs.jpl.nasa.gov/

maps/satellite_feed/atmosphere_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

Ozone Layer

One of the most famous parts of the atmosphere…the ozone layer

Short National Geographic Video

BUT, more on the Ozone Layer to come…