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Aim: What is the reason for the seasons?

Aim: What is the reason for the seasons?. Seasons animation. Seasons diagram in Northern Hemisphere. A: Two Reasons:. 1. The tilt of the Earth’s axis a. When a hemisphere is tilted toward the Sun, the season is summer b. When a hemisphere is tilted away from the Sun, the season is winter.

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Aim: What is the reason for the seasons?

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  1. Aim: What is the reason for the seasons? Seasons animation

  2. Seasons diagram in Northern Hemisphere

  3. A: Two Reasons: • 1. The tilt of the Earth’s axis a. When a hemisphere is tilted toward the Sun, the season is summer b. When a hemisphere is tilted away from the Sun, the season is winter. • 2. The revolution of the Earth around the Sun • The hemisphere that points toward the Sun changes as the Earth revolves around the Sun = causes seasons to change.

  4. B. Earth’s tilt creates uneven heating • The earth is tilted 23.5 o in relation to the sun. • The tilt causes the sun to hit the earth at different angles….causing different temperatures. • This is called the angle of insolation. Higher angles=stronger sunlight

  5. ESRT – periods of revolution Which planet is going:Fastest? Slowest? The farther the planet…the faster the orbital speed!

  6. Questions… • If the Earth’s orbit is a 360o ellipse, and it takes 365.25 Earth days to revolve….Approximately how many degrees per day does the Earth travel in its revolution?A) 1 B) 3 C) 10 D) 30

  7. C. Definitions • 1. Revolution: The movement of a planet in its orbit around the Sun. • 2. Orbit: The path a planet takes around the Sun. • 3. Path is slightly oval shaped called anellipse. An oval shaped orbit is referred to as elliptical. The farther away the planet, the longer the period of revolution. • 4. Season: The change in temperature caused by the earth’s tilt as it revolves around the sun.

  8. D. Seasons have nothing to do with distance…the N.H. is in summer when Earth is farther away from the sun.

  9. E. Animations of the The Earth’s Orbit Earths Orbit seasons animation

  10. Label Seasons diagram….

  11. The Tropics

  12. Summer Solstice in N.H.– June 21 First Day of Summer, longest daylight hours Strongest (direct) rays hit north of equatorat the tropic of cancer (noon sun directly overhead) F. What is a solstice? When the Sun’s direct rays (strongest) reach farthest north or farthest south of the equator. Sunrise: N of ESunset: N of W

  13. Winter Solstice in N.H.– December 22 • First Day of Winter, shortest daylight hours. • Strongest (direct) rays hit south of the equator at the tropic of capricorn (noon sun directly overhead) Sunrise: S of ESunset: S of W

  14. G. What is an Equinox? • 1. The direct rays of the Sun are striking at the equator (noon sun directly overhead) • 2. All places on Earth have equal hours of daylight and night • Autumnal Equinox • First Day of Fall in N.H., September 21 • Vernal Equinox • First Day of Spring in N.H., March 21 Sunrise: due ESunset: due W

  15. Varying daylight hours….

  16. Summer in the Arctic • http://www.youtube.com/watch?v=J9eCK7rWMNE

  17. Seasons animation http://kids.msfc.nasa.gov/earth/seasons/EarthSeasons sun at solstice in north pole

  18. Summary – effects of Earth’s tilt • Seasons (Angle if insolation) • Higher angle = warmer season • Lower angle = cooler season • Little change at the equator = no seasons • Different amounts of daylight hours (duration of insolation) • Longer duration = warmer days • Shorter duration = cooler days

  19. Insolation Chart

  20. Apparent Path of the Sun Aim: Why do we get differing amounts of daylight hours during the year?

  21. A. Why do we get different amounts of daylight hours during the year? • The tilt of the Earth’s axis makes the sun appear to rise to different heights during different seasons. • Summer – sun rises higher, takes longer to set, longer daylight hours, shorter shadows, more intensity and duration of insolation. • Winter – sun rises lower, takes less time to set, shorter daylight hours, longer shadows, less intensity and duration of insolation.

  22. View of Sun in N. H. at noon

  23. At the equator….

  24. Noon sun at different latitudes KNOW THESE DIAGRAMS! EQUATOR N. Hemi N. Pole S. Hemi

  25. Intensity (strength): Atmosphere (clouds) Latitude Seasons Time of Day Duration (length): Latitude Season Factors Affecting Insolation

  26. Surface temperatures…. • The Earth’s surfaces take time to absorb and heat the air…so the warmest time of the day is late afternoon, even though the strongest intensity of insolation is at noon. • Same applies for seasons….strongest intensity is in June when the sun is most direct overhead, but it takes a couple of months to heat the oceans and land…so the warmest month tends to be August.

  27. Climate change in history –Milaknovitch cycles • Earth wobbles like a top – every 26000 yrs. • Earth’s orbit becomes more elliptical – every 100,000 yrs. • Tilt changes from 23.5 to 24.5 every 41000 yrs. • Milankovitch cycles on four different periods: 19,000, 23,000, 41,000 and 100,000 years. • Thought to trigger ice ages

  28. More seasons animations • Brainpop.com

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