1. Earth’s Seasons

2. Earth's Rotation
Earth turns on its axis of rotation as it orbits the Sun. The axis of rotation is an imaginary line running through the center of Earth.

3. What Causes Day and Night?
Sunlight shines on half of Earth at any given time, producing daytime due to the Earth’s rotation.

4. What is a Season?
A season is a pattern of temperature changes and other weather trends over the course of a year.

5. What Causes Earth's Seasons?
The tilt of the Earth’s axis causes the seasons due to changes in the amount of sunlight which results in changes in temperature.
Click the Earth!

6. Seasonal Vocabulary
Equinox – sunlight shines equally on the northern and southern hemispheres.
Solstice – the area of sunlight is at a maximum in one hemisphere and a minimum in the other hemisphere.

7. Autumnal Equinox Half of the sunlight is in each hemisphere.
The strongest sunlight is on the equator.
Marks the beginning of fall in the Northern Hemisphere and spring in the Southern Hemisphere.

8. Winter Solstice
Less than half of the Northern Hemisphere is in sunlight.
The strongest sunlight is south of the equator, so the Southern Hemisphere grows warmer.
Marks the beginning of winter in the Northern Hemisphere and summer in the Southern Hemisphere.

9. Vernal Equinox Half of the sunlight is in each hemisphere.
The strongest sunlight is on the equator.
Marks the beginning of spring in the Northern Hemisphere and fall in the Southern Hemisphere.

10. Summer Solstice
Less than half of the Southern Hemisphere is in sunlight.
The strongest sunlight is north of the equator, so the Northern Hemisphere grows warmer.
Marks the beginning of summer in the Northern Hemisphere and winter in the Southern Hemisphere.

11. The Earth's Seasons

12. What Affects Temperature?
The angle of sunlight affects temperature.
Winter : Sun appears low in the sky (long shadows).
Spring and Fall: Sun appears higher in the sky (medium shadows).
Summer: Sun appears high in the sky (short shadows).

13. Angle of Sunlight

14. What Affects Temperature?
Day length affects temperature.
The longer the days = higher the temperature.
The shorter the days = lower the temperature.

15. The Moon: Earth's
Natural Satellite

16. Basic Facts
The Moon is about 1/4 Earth's diameter
The Moon is one percent Earth's mass.
The Moon is about 380,000 km (240,000 miles) from Earth (it would take a plane 20 days to cover the distance)

17. The Moon's Rotation and Orbit
The Moon orbits the Earth once every 27.3 days.
The Moon rotates around its axis once every 27.3 days.
Since the orbit and rotation of the Moon are equal, we can only see one side of the Moon from Earth.
The surface we see is called the near side of the Moon and the surface we can’t see is the far side of the Moon.

18. The Moon's Physical Features
The Moon has three different types of main physical features.
1. Craters
2. Highlands
3. Maria

19. The Moon's Craters
The Moon's craters show its history.

20. The Moon's Highlands
The highlands are light-colored regions of broken rock.
Scientists know the highlands are very old because they are covered with impact craters.
The highlands are at greater altitudes than the maria.

21. The Moon's Maria
The maria are large, rounded, dark areas on the Moon.
There are more large maria on the Moon's near side than on the far side.

22. The Moon's Maria continued
The maria formed as lava filled the low-altitude areas inside large impact craters. The lava then solidified into flat plains.
The maria do have some impact craters, but not as many as the highlands, because the surface is younger.

23. The Moon's Rocks
Moon rocks show the age of the area from where they come from.
Rocks from the highlands are about 4.5 billion years old, while rocks from the maria are 3.1 to 3.8 billion years old.
The lava that made the maria formed a type of igneous rock called basalt.

24. The Moon's Soil
The Moon has a form of lifeless soil of broken rocks.
The soil formed as frequent impacts broke up rocks into small and smaller pieces.
The impacts also compacted soil into new rocks or melted it into glassy rocks.

25. The Moon's Structure
The Moon has 3 layers.
1. Crust (C)
2. Mantle (B)
3. Core (A)

26. The Moon's Crust
The Moon's crust is a thin shell of less-dense rock around the mantle.

27. The Moon's Mantle
The Moon's mantle consists of dense rock that includes iron and magnesium and makes up most of the Moon's volume.

28. The Moon's Core
The Moon's core seems to be similar to Earth's core, consisting of iron and other metals. The core takes up only a small fraction of the Moon's interior.

29. The Moon's Formation
Most likely a giant impact probably formed the Earth-Moon system.
An early version of Earth was hit by a smaller object.
Much of the material from both objects combined to form a new version of Earth.
The Moon forms from material that is left orbiting the new Earth.

31. The Moon's Phases

32. The Moon's Phases
The Moon takes just under 28 days to go from a New Moon to a Full Moon and back to a New Moon again.
Waxing moons occur during the first two weeks of the Moon cycle.
As more and more of the Moon's near side becomes sunlit, the Moon appears to grow from new to crescent to first quarter to gibbous.

33. The Moon's Phases continued
Waning moons occur during the last two weeks.
As less and less of the near side is in sunlight, the Moon appears to shrink from full to gibbous to third quarter to crescent and back to new.

34. Eclipses

35. What is an Eclipse?
An eclipse happens when the moon blocks the Sun or the Earth's shadow falls on the moon.

36. Eclipse Vocabulary
Umbra: like an umbrella, makes a dark shadow; means shadow.
Penumbra: a partial or lighter shadow.
umbra
penumbra

37. Lunar Eclipse Occurs when the Earth's shadow falls on the moon.
Lunar eclipses occur, on average, about every six months.
Lunar Eclipse

38. Lunar Eclipse Continued

39. Solar Eclipse
Occurs when the moon blocks our view of the sun. This happens when the Moon is exactly between the Sun and the Earth.

40. Solar Eclipse Continued

41. The Earth’s Tides

42. What is a tide?
Tides are the vertical movement of water, the rise (flood) and fall (ebb) of water in large water bodies.
Tides are most noticeable along continental shorelines.

43. What causes tides?
Tides occur because the Moon’s gravity changes the shape of Earth’s oceans.
Moon
low tide
High tide
rotation of Earth

44. The attraction causes the oceans to bulge out in the direction of the moon.
Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side).
What causes tides…

45. Since the earth is rotating while this is happening, two tides occur each day.
What causes tides…

46. Low tide

47. Bay of Fundy, Nova Scotia

48. Spring Tides Spring tide:
A tide of large range occurring during new and full moons.
Happens when the Earth, Moon, and Sun are all lined up.
Results in extreme high tides and low tides.
Spring Tides

49. Neap tide:
A tide of small range occurring during the 1st & 3rd quarter moons.
Happens when the Earth, Moon, and Sun are not lined up.
Results in less extreme high tides and low tides.
Neap Tides