Unit 1 Notes: Tides and Seasons
I.
Key Vocabulary
a. High tides: when ocean water reaches a high level before beginning to fall again
b. Low tides: when ocean water reaches a low level before beginning to rise again
c. Spring tide: when the range of high and low tides is greater than usual because the sun,
Earth, and moon form a straight line
d. Neap tide: when the range of high and low tides is smaller than usual because the
positions of the sun, Earth, and the moon form a right angle
e. Gravity: force of attraction between any two objects; depends on the mass and distance
between the objects
II.
Tides
a. The water level at the beach constantly changes because of the tides
b. Tides rise & fall because of the gravitational attraction of the moon and the sun along
with the rotation of Earth
c. Tides are different from waves (caused by wind over the ocean)
d. Tides are caused by gravitational attraction
III.
Gravity
a. Gravity depends upon mass & distance between objects
b. Because the sun is farther away than the moon is to the Earth, the moon’s attractive
forces on Earth is about two times the sun’s attractive force
c. Because the moon orbits Earth, it’s attractive forces affect only the oceans on the side of
Earth facing the moon
d. Ocean water facing the side of the moon bulges toward the moon—called a high tide
e. The 2nd high tide takes place on the other side of the Earth at the same time—happens b/c
the Earth & moon are spinning together (occurs about every 12.5 hours)
f. This 2nd tide faces away from the moon
g. Sea level is higher in both places where high tides occur
h. At the same tide as high tides are drawn toward the moon, other ocean areas experience
low tides
IV.
Types of Seasonal Tides
a. Spring tides occur during full or new moon when sun, Earth, & moon are in a straight
line—gravitational attraction of sun works with gravitational attraction of the moon
b. High tides will be higher than normal & low tides lower than normal
c. Neap tides occur during 1st or 3rd quarter moon when sun, Earth, & moon form right
angle—gravitation attraction of sun works against gravitational attraction of moon
d. High tides are lower than normal & low tides are higher than normal
a. Most are in “asteroid belt” between Mars & Jupiter
EE: SRA 66B
JWoods
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