This document discusses the causes of Earth's seasons. It explains that the seasons are caused by changes in the angle of the Sun's rays due to the tilt of Earth's axis of rotation as it revolves around the Sun. Because of this tilt, different parts of Earth receive more or less direct sunlight throughout the year, causing seasonal temperature variations. The document asks questions to help understand how Earth's rotation, axial tilt, and revolution around the Sun contribute to creating the seasons.

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? We’re closer to the Sun in our annual orbit We receive more direct sunlight 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? Sub Polar Mid Latitudes Sub Tropical Equatorial

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

22. What if Earth were more tilted? Conditions would stay the same Summers would be warmer and winter would be colder, but average temps would be same More direct rays at higher latitudes in summer would lead to warmer overall annual temps 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