Tides and the Moon
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n August, Tyler went to visit his cousins who lived near the ocean in Tidal
Town. After lunch on his second day there, his cousin Morgan took him
to Sandy Beach. “Today is a great day for the beach,” said Morgan. “The
tide will be really low early this afternoon, so there will be a lot of room on
the beach for us to play ball and run around.”
At the beach, they spread out a blanket, played catch, and splashed around
in the water. But in the late afternoon the tide began to come in, with the
ocean covering up more and more of the beach. “Time to move our blanket
way back,” said Morgan. “High tide will be really high today.”
“Do you know why the tides are extremely high and low today?” Tyler asked.
“I know it has something to do with the Moon,” Morgan answered. “Right
next to the tide information in the Tidal Town News are pictures of the
Moon.” That night they searched the Internet and found data on the Moon
and tides for Sandy Beach. Then they started to look for a relationship
between the tides and the Moon.
CHALLENGE
What is the relationship between the phase of the Moon and
extreme tides?
Compare the water level at low and high tide in this bay in New Brunswick, Canada.
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Tides and the Moon • Activity 82
MATERIALS
For each student:
1
Student Sheets 82.1a, b, and c, “Moon and Tide
Calendar”
PROCEDURE
1. Table 1 below shows the data about the Moon and tides that Tyler
and Morgan found for the day when they went to Sandy Beach and
for another day about a week earlier.
2. Record in your science notebook:
a. How many high tides occur each day?
b. How many low tides occur each day?
c. Which day shows more extreme tides (higher high tides and
lower low tides)?
Table 1: High and Low Tides for Two Days in August
Day
High Tide or
Low Tide?
Tide Time
Height
(feet)
high
12:10 a.m.
2.6
low
6:16 a.m.
0.5
high
12:18 p.m.
2.2
low
6:36 p.m.
0.2
low
12:26 a.m.
–0.2
high
7:02 a.m.
3.5
low
1:37 p.m.
–0.2
high
7:19 p.m.
2.3
August 7
quarter
August 14
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Moon Phase
full
Tides and the Moon • Activity 82
Tyler and Morgan realized that they had to look at the tide height and Moon
phase for several months. They decided to look for the days with extreme
tides and days with full Moons to see if they could find a connection. Their
results are shown in Table 2 below.
Table 2: Moon and Tide Data for Five Months
Sets of Extreme Tides (EXT)
Full Moons (F)
May 2–5
May 18
May 18–21
June 16
June 1–2
July 15
June 14–16
August 14
July 1–2
September 13
July 13–17
July 28–30
August 13–15
August 28–30
September 12–15
3. Transfer the information in Table 2 to your Student Sheet:
• Mark full Moon days with an “F.”
• Mark when you think there will be new Moon days with an “N.”
• Mark extreme tide days with an “EXT.”
4. Record in your science notebook any patterns you see in the relationship between the tides and the Moon each month.
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Tides and the Moon • Activity 82
ANALYSIS
1. Use the information on your Student Sheet:
a. to count the number of days between the full Moons and list
them. Hint: You should list 4 numbers.
b. to calculate the average number of days between full Moons.
c. to use your average to predict the date of the next full Moon
after the one on September 13.
2. Based on the data on your Student Sheet, how often do sets of
extreme tides (both high and low) occur?
3. What is the connection between extreme tides and the phases of
the Moon? Use the evidence from your calendar to support your
answer.
EXTENSION
Visit the Issues and Earth Science page of the SEPUP website to view an
animation of the tides.
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