Ocean Motions
Tides: The Power
of Gravity!
Ocean Motions
What are Tides?
The rise and fall of ocean currents!
The water rises for six hours and then falls for six hours in a
regular cycle!
Ocean Motions
What causes tides?
Tides are caused mainly by the difference in how much the sun’s
gravity and moon’s gravity pull on different parts of the Earth!
There are 2 High Tides and 2 Low Tides every day.
There are 2 Spring Tides and 2 Neap Tides each month!
Ocean Motions - Tides
What Causes Tides?
Tides are caused by the interaction of Earth, the moon, and
the sun.
Ocean Motions
Animation of High and Low Tides
http://www.wissen.swr.de/warum/gezeiten/themenseiten/t2/
s1.html
Ocean Motions
- Phases, Eclipses, and Tides
Spring and Neap Tides
When Earth, the sun, and the moon are in a straight line, a
spring tide occurs. When the moon is at a right angle to the
sun, a neap tide occurs.
Ocean Motions
Animation of Spring and Neap Tides
http://www.sfgate.com/getoutside/1996/jun/tides.html
Ocean Motions
Another Spring & Neap tides animation!
http://youtu.be/l37ofe9haMU
Ocean Motions - Tides
What Causes Tides?
Spring tides and neap tides are
caused by the positions of Earth,
the sun, and the moon.
Ocean Motions - Tides
Plotting Tides
This table lists the highest high
tides and the lowest low tides for
one week at the mouth of the
Savannah River, where it meets
the Atlantic Ocean in Georgia.
Ocean Motions - Tides
Plotting Tides
Graphing:
Use the data in the table to make
a graph. On the horizontal axis,
mark the days. On the vertical
axis, mark tide heights ranging
from 3.0 to –1.0 meters. (Hint:
Mark the negative numbers below
the horizontal axis.)
Ocean Motions - Tides
Plotting Tides
Graphing:
Plot the tide heights for each
day on the graph. Connect the
high-tide points with one line
and the low-tide points with
another line.
Tide Height by Day
Tide Height
3
2
High
1
Low
0
-1
1
2
3
4
Days
5
6
7
Ocean Motions - Tides
Plotting Tides
Interpreting Data:
How do the high and low tides
change during the week?
During the first six days, the
high-tide value increases
steadily while the low-tide
value decreases. On day 7,
the trends reverse.
Ocean Motions - Tides
Plotting Tides
Inferring:
What type of tide might be
occurring on day 6? Explain.
Spring tide might be occurring
on day 6, when there is the
greatest difference between
high and low tides.
Ocean Motions - Tides
Previewing Visuals
Spring and Neap Tides
Q. When do spring tides occur?
A. During the full and new moon phases
Q. What is a neap tide?
A. A smaller tide that happens at the first- and third-quarter moons