The Moon orbits Earth and reflects sunlight, which causes its phases to appear to change over the course of a lunar month as the illuminated portion changes from new to full and back to new. The Moon's gravitational pull, combined with the Sun's, causes two high and two low ocean tides each day. The greatest difference between high and low tides occurs during full Moons and new Moons, when their combined gravitational pulls reinforce each other.

1. MOON PHASES
POWERPOINT

2. 2
• The Moon orbits the Earth
• The Moon doesn’t shine on its own; it
reflects sunlight
Important Key Points

3. The revolution of the moon around
the Earth causes the moon to appear
to have phases.
NSF North Mississippi GK-8
Why does the moon have phases?

4. The lunar month is the 29.5 days it takes to go from
one new moon to the next. During the lunar month,
the Moon goes through all its phases.

5. FULL
QUARTER
CRESCENT
GIBBOUS
FOUR MAIN SHAPES

6. Waxing or Waning?
Waxing means the moon is
“growing”. If the moon is
getting bright from the right it
is waxing.
Waning means the moon is
“shrinking”. If the moon is
dark on the right it is
waning.

7. Lunar Cycle: TEKS 8.7B
Moon Phases

8. Lunar Cycle: TEKS 8.7B
How can I determine which phase the moon is in?
• Step 1: Look at which side is illuminated.
– If the right side is illuminated then it is waxing.
– If the left side is illuminated then it is waning.
– Or if all is illuminated then it is a full moon
– If there is no illumination then it is a new moon.
• Step 2: Look at the shape and decide if it is full, quarter
(half moon), crescent (less than half) or gibbous (more
than half).
**Note, a waxing quarter is called 1st Quarter. A waning
quarter is called 3rd Quarter.

9. Lunar Cycle: TEKS 8.7B
Let’s practice!
• Step 1: Look at which side is illuminated.
– If the right side is illuminated then it is
waxing.
– If the left side is illuminated then it is waning.
– Or if all is illuminated then it is a full moon
– If there is no illumination then it is a new
moon.
• Step 2: Look at the shape and decide if it is
full, quarter (half moon), crescent (less than
half) or gibbous (more than half).
Step 1—The left side is light, so it is waning.
Step 2—The shape is less than half, so it is crescent
The moon phase is a WANING CRESCENT

10. Lunar Cycle: TEKS 8.7B
Let’s practice!
• Step 1: Look at which side is illuminated.
– If the right side is illuminated then it is
waxing.
– If the left side is illuminated then it is waning.
– Or if all is illuminated then it is a full moon
– If there is no illumination then it is a new
moon.
• Step 2: Look at the shape and decide if it is full,
quarter (half moon), crescent (less than half) or
gibbous (more than half).
Step 1—The left side is light, so it is waning.
Step 2—The shape is half, so it is quarter.
The moon phase is a 3rd QUARTER.

11. Lunar Cycle: TEKS 8.7B
• Which phase is shown here?
On Your Own Example 1

12. Lunar Cycle: TEKS 8.7B
• Which phase is shown here?
On Your Own Example 2

13. Lunar Cycle: TEKS 8.7B
• Which phase is shown here?
On Your Own Example 3

14. Lunar Cycle: TEKS 8.7B
What causes TIDES?

15. •There are two high tides and two low tides each
day.
• Tides are caused by the pull of both the moon’s
gravity and the sun’s gravity on the Earth. The
moon has a 70% effect on the tides and the sun
has a 30% effect on the tides.
•Changes in the positions of the Earth, sun, and
moon affect the height of the tides throughout the
month.
Important Key Points

16. During full or new moons, the
Earth, sun, and moon are nearly in
a straight line. This occurs twice
each month.
The gravitational pull of the sun is
"added" to the gravitational pull of
the moon on Earth, causing the
oceans to bulge a bit more than
usual.
This means that high tides are a
little higher and low tides are a little
lower than average.
Spring Tides

17. The top picture is
low tide and the
bottom is high
tide.
Notice that there
is a BIG difference
between the two.
Spring Tides

18. Seven days after a spring tide, the sun and
moon are at right angles to each other and
produce neap tides. These occur twice each
month.
Neap tides occur during the first and third
quarter moon, when the moon appears "half
full.“
When this happens, the bulge of the ocean
caused by the sun partially cancels out the
bulge of the ocean caused by the moon.
This produces moderate tides meaning that
high tides are a little lower and low tides are a
little higher than average.
Neap Tides

19. Lunar Cycle: TEKS 8.7B
The top picture is
low tide and the
bottom is high
tide.
Notice that there
is only a small
difference
between the two.
Neap Tides