The document summarizes what causes seasons on Earth. It explains that seasons result from the tilt of Earth's axis relative to its orbit around the sun. This causes variations in the intensity of sunlight and day length throughout the year. Specifically, summer occurs in the Northern Hemisphere when it is tilted toward the sun, and winter occurs when it is tilted away. Spring and fall seasons experience nearly equal amounts of daylight and nighttime.

1. What Causes Seasons on
Earth?
By Nick Southern

2. Michigan Standards
• E.ES.M.6 Seasons- Seasons result
from annual variations in the
intensity of sunlight and length of
day due to the tilt of the axis of the
Earth relative to the plane of its
yearly orbit around the sun.

3. Key Vocabulary
• Rotation
• Revolution
• Axis

4. Axis
• Axis – an
imaginary
line which
the earth
turns
around
• The earth is
tilted at
about 23.5
degrees.
http://upload.wikimedia.org/wikipedia/commons/6/61/AxialTiltObliquity.png

5. Rotation
• Rotation – turning
around on an axis
• It takes the earth
about 24 hours to
complete one rotation
around it’s axis. This
is also known as a
day.
http://upload.wikimedia.org/wikipedia/commons/3/30/Globespin.gif

6. Revolution
• Revolution – one object
traveling around another
in a circular or elliptical
pattern
• It takes approximately
365 days for the earth to
make one revolution
around the sun. This is
also known as a year.

7. What is a season?
• A season is a subdivision of a year.
• We have four seasons on earth: winter,
spring, summer, and fall
• During seasons, hours of daylight and
weather may vary greatly depending on
your location on Earth.

8. So What Causes Seasons?
• There are two major causes for seasons
on Earth.
– 1 – the tilt of the earth on it’s axis
– 2 – position of the earth in relation to the sun
(revolution)

9. Winter
• We are going to focus on the
seasons in the Northern
Hemisphere (that’s where we
live).
• During winter, the earth is
titled away from the Sun.
• This results in the Northern
Hemisphere not getting strong,
direct rays from the Sun. This
is what causes winter.
• A cool fact is we are actually
closer to the Sun in the winter
than in the summer.
• The amount of night hours
exceeds daylight.

10. Summer
• During summer in the
Northern Hemisphere, the
earth is tilted towards the
Sun.
• This results in the
Northern Hemisphere
getting direct rays from
the Sun.
• The amount of daylight
exceeds the amount of
night hours.

11. Spring and Fall
• In the spring and fall
seasons,
temperatures are
generally mild
• Daylight and
nighttime hours are
almost equal

12. Southern Hemisphere
• We have already explored seasons in the
Northern Hemisphere.
• In the Southern Hemisphere, the seasons
are opposite.

13. Exceptions
• In tropical regions –those located around the
equator do not received the four seasons.
• Their “seasons” are wet and dry.
• In polar regions, during their winter, they may
only receive a few hours of daylight each day
and in the summer, only a few hours of
darkness.
• This is because they are either tilted towards the
Sun the most or they are tilted away from the
Sun the farthest.

14. Seasons
http://en.wikipedia.org/wiki/File:Seasons1.svg

15. Video Clips
• Seasons Aren’t Dictated By Closeness to the Su
S
• How Earth’s Tilt Causes Seasons

16. Quiz
• What are the two factors which cause the
seasons on Earth?
• Are we closer to the Sun in the winter or
summer?

17. Sources
• http://www.dictionary.com
• http://upload.wikimedia.org/wikipedia/commons/3/30/Globespin.gif - Animated Earth
spinning on axis.
• http://upload.wikimedia.org/wikipedia/commons/6/61/AxialTiltObliquity.png - Image
of Earth on axis
• http://en.wikipedia.org/wiki/File:Seasons1.svg – Image of Earth in Relation to the sun
• http://www.khanacademy.org/science/cosmology-and-astronomy/v/seasons-aren-t-dictated-
- Video Clip
• http://www.khanacademy.org/science/cosmology-and-astronomy/v/how-earth-s-tilt-causes-s
- How Earth’s Tilt Causes Seasons