Tide Exercise
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School
Diablo Valley College *
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Course
MISC
Subject
Geography
Date
Dec 6, 2023
Type
Pages
3
Uploaded by EarlWildcatMaster702
This document was created using the NOAA- Ocean Explorer Predicting Tides activity with modifications by Elizabeth
Keddy.
Predicting the Tides
Knowing when and how much the tides will rise and fall each day is important to beachcombers,
mariners, fishermen, and the people who operate seaside industrial and commercial facilities.
Miscalculating the arrival and size of the tides can have expensive, even deadly, consequences.
Predicting the tides is complicated because the tides are affected by many factors. In this activity, you’ll
have a chance to consider some of the most important and universal influences, those due to the
movements of the sun, the moon, and the earth. In reality, a number of local and transient factors, such
as the shape of the coastline, the flow of currents, and the weather, must also be taken into account.
Lunar Time
Over the course of what is called a lunar day, a spot on earth that is directly beneath the moon rotates
once until the moon is again exactly overhead. Because the earth spins in the same direction that the
moon orbits the planet, the cycle is slightly longer than a regular day -- it takes 24 hours and 50 minutes.
1.
Assuming a semidiurnal tidal pattern, how much time passes between one high tide and the next
high tide (in solar hours)?
2.
How much time passes between a low tide and the next high tide (still assuming a semidiurnal tidal
pattern, report your answer in solar hours)?
Positions of the Sun and Moon
The height of the tides varies over the course of a month. The greatest tidal range (highest highs and
lowest lows), called spring tides, occur when the moon and the sun are aligned. The smallest tidal range
(lowest highs and highest lows), called neap tides, happen when the sun and the moon are at a 90°
angle to one another.
3.
Explain how spring and neap tides are created.
4.
How many spring and neap tides occur each month?
Explain why.
This document was created using the NOAA- Ocean Explorer Predicting Tides activity with modifications by Elizabeth
Keddy.
Orbital Shape
5.
Why does the distance between the earth and the sun or moon affect tides?
6. Which has a bigger effect on the tides- the sun or the moon?
Explain why.
7.
When will lunar tides be higher, at perigee or apogee?
How often does each occur?
8. When will solar tides be higher, at perihelion or aphelion?
How often does each occur?
Applying what you’ve learned:
For #’s 9
-11:
You are the captain of a ship carrying large construction cranes, each worth over $1
million.
The tops of the cranes are over 60m above the water’s surface. In order to deliver the cranes,
you must go under a bridge that is 58m above the surface of the water at a normal low tide.
You must
time your trip correctly to avoid a disaster and keep your job.
9.
Circle or underline the conditions that will produce the lowest low tide:
Time of year:
June
or
January
Phase of the moon:
Full
or
Quarter
Lunar Orbital Phase:
Apogee
or
Perigee
This document was created using the NOAA- Ocean Explorer Predicting Tides activity with modifications by Elizabeth
Keddy.
10.
Explain why the conditions you selected above will allow for safe passage.
11.
Your sister ship will have to wait to make the same attempt until you unload your cargo and clear
the dock. If you leave on a high tide that crests at noon, when should your fellow captain make his
move?
12.
You’d like to explore the organisms that live near the ocean’s edge this weekend.
According to the
following tide table,
what time should you go tide pooling
? Tide pooling is best when the greatest
amount of beach is exposed
, and it’
s light enough to see without a flashlight.
2023-03-18 Sat
12:37 AM PDT
5.6 feet
High Tide
2023-03-18 Sat
6:25 AM PDT
Sunrise
2023-03-18 Sat
7:04 AM PDT
0.7 feet
Low Tide
2023-03-18 Sat
1:21 PM PDT
4.3 feet
High Tide
2023-03-18 Sat
6:14 PM PDT
Sunset
2023-03-18 Sat
6:45 PM PDT
1.9 feet
Low Tide
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