Transcript Tides

Question of the Day
Question: Tell me what you know about tides;
describe tides.
Answer: … … …
Tides
• The Rhythmic rise and fall of the ocean’s water at
a fixed location is a tide.
• Tides are extremely long waves moving through
the ocean
• When the crest of the wave reaches one location,
the tide is high.
• When the trough of the wave reaches that same
location, the tide is low.
Tides at the Bay of Fundy
Why do we have tides?
• To explain tides, think of the earth with no continents and
completely covered by water.
• Gravity from the moon pulls water into a bulge on one side of
the earth.
• Other objects such as the sun and other planets also influence
the tides.
• Coastline shape can also affect size of tides.
http://astro.unl.edu/classaction/animations/lunarcycles/tidesim.html
• However the earth is rotating and therefore there is
also a centrifugal force acting in the opposite
direction.
• This creates the high tides in 2 areas and low tides
in 2 other areas.
• Since the moon is so much closer to us than the
Sun, it has much more of an effect on our tides.
• When the sun and moon are in line, we have
maximum high and low tides.
 Spring Tide
Effects of Moon
• When the sun and moon are at 90 degree
angles to one another, tides are not as
extreme.
 Neap Tide
Effects of Moon
Monthly Tidal Cycle
Monterey Bay
Predicted Tides: Monterey, California Time: 8
7
New Moon
Spring Tide
6
Full Moon
Spring Tide
5
Height (ft)
4
3
2
1
First Quarter
Neap Tide
0
-1
0
5
10
15
October 2002
20
25
30
Tides in the news
• 2012: Hurricane Sandy, New York