Transcript North Pacific Storm and Current Moon Phase (Full) = High tides level

North Pacific Storm and Current
Moon Phase (Full) = High tides
plus strong waves = higher sea
level
Tides
Tide You Tube videos

http://www.youtube.com/watch?v=qvzc9yF3g6c

http://www.youtube.com/watch?v=5W2sM1Ma7YA&
feature=related
http://www.youtube.com/watch?v=YiHP8EG_Wq4&
feature=related


http://www.youtube.com/watch?v=4DlqVuNMydk&f
eature=fvw



Tidal Waves
Large waves (bores)
occur in mouth of
rivers—Amazon,
Ganges, Seine
Most less than 1m
Max is 8 mQiantang
River,China

Moves 40 km/hr
Qiantang River,China, Peter Wang
Tides


Shallow water wave with
longest wavelength
Tides defined:
 Periodic, short-term
changes in ocean water
level due to combination
of gravitational force of
moon, sun, and motion
of earth
 Are forced waves
 Pull of two bodies
proportional to masses
of bodies but inversely
proportional to square
of distance
 Tides caused by
gravitational attraction
between ocean, sun,
moon, buy
 Tidal generating force
varies inversely with
cube of distance,
therefore distance more
important than mass
Earth-Moon System




Gravity pulls earth moon toward
each other
But inertia (tendency for moving
object to continue in a straight line)
keeps them apart
Gravity attracts ocean surface
toward moon
Earth motion around center of
mass produces bulge on other side
on the earth, there is an imbalance between the centripetal
(inward) and centrifugal (outward) accelerations. The
centrifugal acceleration is the same everywhere on the earth,
but the gravitational force due to the moon varies over the
surface of the earth.
earth-moon system tidal bulges

More realistic
representation of
tides and earth/moon
orientation

Note the path that
tides will take around
the earth
Note the unequal
high tides at the same
latitude

Why do Tides Rise and Fall



Earth rotates beneath
the bulges
Bulges appear to move
 Bulges want to stay
under moon
Wavelength of tides up
to 12,500 miles
Tidal Day


Earth rotates in 24 hr
A tidal day is 24hr 50min
 Earth is spinning but moon is also rotating around the earth
 When earth makes one rotation, the moon has moved 12 degrees
 Takes an extra 50 minutes for earth to get back to original position
under moon.
 Therefore high tide arrive 50 minutes later each day
Changing
Position of Moon



Moon not always over
equator
 Moves from 281/2
degree N&S
 Will have higher
high tide, lower high
tide, low tide
More realistic
representation of tides
and earth/moon
orientation
Note the path that tides
will take around the
earth
Solar Tides


Sun also influences tides
27 millions times as
massive as moon
 But 387 times
further
 Therefore sun’s
influence on tides is
46% that of the
moon
 These are slower
moving tides
because takes earth 1
year to move around
the sun
Spring & Neap Tides


When earth, moon,
sun aligned get higher
high tides and lower
low tides
 Highest tides
called spring tides
 Lowest called
neap tides
When earth, moon,
sun at right angles get
lowest high tides and
highest low tides
Spring Tides
The gravitational affects of the moon and sun combine to
influence the flow of the oceans on Earth.
Moon
Moon
Moon
Earth
Phaseofofthe
the moon?
moon?
Phase
New Moon
Moon
New
Higher high tides and lower low tides
Phase of the moon?
Full Moon
Neap Tides
The gravitational affects of
the moon and sun fight
each other with their
influence on the flow of
the oceans on Earth.
Third Quarter
Phase of the moon?
Moon
Earth
Phase of the moon?
First Quarter
Moon
Lowest high ties and highest low tides
Combined lunar and solar tide
Tidal Patterns

Vary with position of continents, shape of the
basins


Continent beneath moon interferes with tides
These influence cause
Semidiurnal tides (2high & 2 low)
 Diurnal (1high, 1 low)
 Semidiurnal mixed (2 unequal high & low)

09_15tr
P
09_15cr
P
09_15br
P
09_16
P
Min.
Max.
Min.
Max.
Los Angeles Tides


Ampidromic point is
where don’t have a
tide
Wave rotates around
the node or
ampidromic point



Tide in ocean stays to
right
Rotates
counterclockwise
around ampidromic
point
Height of tide increase
with distance from AP
point.
S
Amphidromic Points
The Tides of the Bay of Fundy

Size of the Tides
• Origin of the
Tides
09_17
S
Resources


The following web site is a good resource to look for definitions
of tidal terms you are unfamiliar with: http://coops.nos.noaa.gov/publications/glossary2.pdf (pdf)
The following web site will let you review and test your
knowledge of tides, as well as introduce some material about
tides which we didn't cover here.
http://www.es.flinders.edu.au/~mattom/IntExerc/basic5/inde
x.html
STOP HERE
The point “Z”
stays fixed, and
the earth-moon
system rotates
about it