This document discusses the causes of Earth's seasons. It explains that the seasons are caused by the tilt of the Earth's axis of rotation relative to its orbit around the Sun, not by changes in the Earth's distance from the Sun. Throughout the year, as the Earth revolves around the Sun, different parts of the Earth receive more or less direct sunlight depending on the tilt, resulting in temperature variations that cause the seasons. The document also discusses how changes in the tilt would affect seasonal changes and temperatures in different latitudes.

1. Physical Geography
Class 5: Earth Movements and
Seasons

2. What are the changes that happen
seasonally?
• Think about local changes
• Changes elsewhere
• List, with your group, as many seasonal
differences as you can think of

3. What do you notice about the Sun’s
angle throughout the year?
• Is the sun at the same height each morning
when you wake up?
• Is the sun in the same direction every morning
when you drive to school?
• Does the sun reach the same height in the sky
at its highest throughout the year?
• Think about changes – in your home, along
your commute, at school, etc.

4. Why is it warmer in Summer?
14%
7%
79%
1 2 3
1. We’re closer to the
Sun in our annual
orbit
2. We receive more
direct sunlight
3. Our hemisphere is
tilted toward the
sun, making us
closer to the sun
than the other
hemisphere

5. What causes Earth’s seasons?
• Is it the distance to the Sun?

7. How does distance to Sun change
throughout year?
• Perihelion – orbital point closest to sun
• Aphelion – orbital point furthest from sun

8. So what does cause seasons?
• Angle of sun’s rays changes
• This changes the “subsolar point” = point on
Earth that receives Sun’s direct (90 degree)
rays

9. Why is it hotter in summer?

11. What caused the angle of the Sun’s
rays to change?
• From day to night…..
• From season to season……
• And from place to place?

12. 1. Rotation

13. 2. Axial Parallellism
• North Pole stays
pointed toward Polaris
• All day long….
• All year long

14. 3. Revolution

15. 4. Tilt of Earth

16. This shows axial parallelism, revolution
and tilt

17. 5. Sphericity
• Also shows rotation and tilt

18. Changing Day Lengths

19. Where are seasonal changes the most
pronounced?
7%
57%7%
29%
1 2 3 4
1. Sub Polar
2. Mid Latitudes
3. Sub Tropical
4. Equatorial

21. What if Earth were NOT tilted?
1 2 3 4 5 6 7
7%
13% 13%
0%
60%
0%
7%
1. No change
2. Day lengths would stay same all
year long for every latitude
3. All latitudes would experience
the same temp; earth would
have one consistent climate
4. There would be no seasonal
change in weather conditions
anywhere
5. There would be no diurnal (day
to night) changes in temp
6. Both 2 and 4 would be correct
7. Both 2 and 5 would be correct

22. What if Earth were more tilted?
1 2 3 4
0% 0%0%0%
1. Conditions would stay the same
2. Summers would be warmer and
winter would be colder, but
average temps would be same
3. More direct rays at higher
latitudes in summer would lead
to warmer overall annual temps
4. Less direct rays at higher
latitudes in winter would lead to
colder temps, more snowfall,
more reflection and less
absorption of sun, leading to
overall cooling

23. Special Latitudes

28. Time lapse “Sunset” at Barrow