1. What Causes Seasons?

2. We know that the reason we have day and night is because the Earth
rotates.
Rotate means
to turn.
The Earth rotating on its
______
gives us day and night.
axis
Earth’s axis is
the imaginary line that goes through the center of the Earth.

3. But guess what! Rotating isn’t the only way the Earth moves in space!
The Earth also revolves.
Revolve – When one object moves around another object

4. How long does one revolution take?
It takes the Earth one year, or 365 ¼ days to orbit the sun.
What does “Orbit” Mean?
Orbit -
The path that an object follows as it revolves around another object.

5. Most of the world experiences the four seasons.

6. Winter…

7. Spring…

8. Summer…

9. and fall.

10. That tilt gives us seasons!
But why do we have four seasons?
It’s because the Earth’s axis is tilted.
Take a good look at this globe. It‘s not tilted like that because it looks nice. That’s the way the Earth is tilted in space!
That tilt gives us seasons!

11. Look at this diagram. Notice how the Earth is always tilted in the same direction. As the Earth __________ the part of Earth tilted toward the sun changes.
revolves

12. During part of the year the North Pole tilts towards the sun
During part of the year the North Pole tilts towards the sun. This season is ________.
summer

13. During another part of the year, the North Pole points away from the sun. This season is ______.
winter

14. When the North Pole is tilted toward the Sun, the Sun travels higher overhead in the sky. The Sun’s rays shine straighter down on that part of the Earth. It is summer in that part of the Earth.
It’s like pointing a flashlight at a piece of paper. When you hold the flashlight straight above the paper, the rays from the flashlight shine down straighter.

15. When the North Pole is tilted away from the Sun, the Sun stays lower in the sky. It is then winter in that part of the Earth.
If you point your flashlight at a piece of paper at an angle, the rays from the flashlight spread out.

16. Seasons In Ho Chi Minh City
Wait a minute
Saigon doesn’t have four seasons
Why not?

17. Seasons In HCMC HCMC is close to the equator
So even though sometimes the sun’s rays are a little more concentrated then others, they’re always fairly strong. That’s why it never gets really cold

18. Wet and Dry Seasons
But the air temperature does change a little bit. And when it cools down, the cooler air can’t hold as much moisture as the warmer air. So it rains more

19. Seasons
So instead of having 4 seasons like most of the planet, tropical places like Vietnam have two basic seasons; wet and dry.

20. Assignment Read pages 320-324 (first half of 324) in your textbook
Answer questions 2-11 on page 328