Transcript Ch. 12 Part 2

Waves, Tides and
Currents
I. The Ocean’s Motions
A. The ocean never rests.
B. Currents, waves, and
tides all move and mix
the ocean waters.
II. Surface Circulation
A. Currents and
waves are
driven by wind.
B. Wind is driven
by heat from
the sun.
III. Coriolis Effect
A. A force resulting from the
rotation of the earth.
B. It mainly affects freely
moving objects, making it
impossible to move in a
straight line.
C. Organisms do not notice the
coriolis effect because it is
too slight.
D. Winds and currents are
strongly influenced
by the Coriolis
Effect.
E. Earth’s rotation causes motion of
objects to be deflected to the
right or left.
1. Northern Hemispheremovement deflected
to the right.
2. In Southern
Hemisphere –
movement deflected
to the left.
IV. Winds
A. Most solar energy is absorbed
at the equator.
B. As warm air rises, cooler air
moves in replacing the warm
air thus creating wind.
C. Wind moves in bent lines
due to the coriolis effect.
D. Trade Winds
1. Easterly surface winds found in
the tropics near the equator.
2. Northern Hemisphere they
blow northeast.
3. Southern Hemisphere - they
blow southeast.
4. Approach the equator at 45⁰.
The Trade Winds
V. Currents
A. Areas of water
flowing
naturally in the ocean driven by
the wind, salinity and the surface
temperatures.
B. The currents move off at a 45°
angle due to the Coriolis Effect.
C. Surface currents are caused by the
wind blowing across the water
surface.
D. When pushed by the winds, the
currents do not
move the same
direction as the
wind.
VI. Gyres
A. Definition – huge rotating
currents of water in the ocean.
B. Gyres develop due to the
influence of the coriolis effect.
C. There are 5 major gyres.
North Equatorial Current –
California Current
South Equatorial CurrentWest Australian Current
South Equatorial Current
– Peru Current
North Equatorial Current –
Canary Current
South Equatorial Current –
Benguela Current
Smaller Gyres
D. Pollution-gyres collect ocean trash,
solutions are needed.
Show Video Clip –
Safari Montage (Ocean Currents)
VII. Waves
A. Most familiar ocean
phenomena.
B. Wave Anatomy
1. Crest-high point
2. Trough-low point
3. Wavelength-distance from one
crest to another
4. Amplitude– rise and fall
C. Wave Anatomy
D. Water Movement
1. Water under the crests move
up and forward.
2. Water under the troughs move
down and backwards.
3. Water is actually just rolling
in place or circling around and
not really going anywhere.
VIII. Tides
A. Definition - The rhythmic rise
and fall of sea levels.
B. Caused by the gravitational
pull of the moon and the sun,
along with the rotations of the
earth, moon, and sun.
C. Centrifugal Force in Tides
1. Definition – outward force from
the center of a rotation on a
body rotating around another
body.
2. The moon does not rotate around
the earth rather both rotate
around the center of their
combined mass.
3. On the side where the moon
pulls strongly on earth, it pulls
on the oceans’ surface water too.
4. On the opposite side
centrifugal force pushes
water away from the earth.
Low Tide verses High Tide
High Tide verses Low Tide
D. The Sun’s Impact
1. The sun is much larger and
is 400 times farther away
from the earth than the moon.
2. Gravitational pull of the sun is
half that of the moon.
E. Moon Phases Moon phases determine ocean tides.
F. Types of Tides
1. Spring Tides - When the sun and
moon are in line with each other.
a. Sun and moon’s combined
pull affects the tide
b. Occurs at new and full moons.
c. There is a large difference
between high and low tide.
d. Spring Tide Alignment
2. Neap Tide - When the sun and
moon are at right angles with
each other
a. Effects of sun and moon are
both diminished
b. Occurs at first and third
quarter.
c. There is a small difference
between high and low tide.
d. Neap Tide Alignment
G. Effects of Tides
1. Tides influence life of near shore
organisms.
2. Effects of Tides:
a. Alternately expose
and submerge organisms
b. Determines circulations of bays
c. Triggers spawning.