Waves
How Does Ocean Water Move?
Science 6
Hill
Oceans
Question:
• How does ocean water move?
– Waves, currents, tides, water cycle
Waves
• A wave is a rhythmic movement
that carries energy through matter
or space.
• All waves have the same main
parts.
Waves
• The highest part of a wave is the crest.
• The lowest part of a wave is the trough.
Parts of Ocean Waves
Wavelength
• The distance from the crest of one wave to the
crest of the wave next to it is called wavelength.
Wave Height
• Wave height is the vertical distance from the
trough to the crest.
Questions
• What is the highest part of the wave
called?
• What is the lowest part of the wave called?
• How is wave length measured?
• How is wave height measured?
Waves
• Most ocean waves are caused by wind
that blows across the surface of the water.
• Friction between the wind and water
transfers energy from the wind to the
water.
Waves
Waves
• The longer and harder the wind blows and
the greater the distance over which it
blows, the higher the waves become…..
nd harder the wind blows and the greater the distance over which it blows, the higher the w
Wave Movement
• The ENERGY of the
wave travels
forward….
• But the water
particles do not!
• The water particles
move in a circular
pattern as they are
temporarily displaced
by the energy of the
wave.
Ocean Waves
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Transfer of Energy
• A wave is really a
transfer of energy
from one water
molecule to the next.
• If all the water itself
moved forward all the
oceans would empty
onto the shore!!!!!
Why Do Waves Break?
• Waves break when they approach shallow water. The sea floor rises
and slows the bottom of the water, but the top keeps going. The top
falls over as gravity pulls it.
Breakers
• The bottom of the wave is slowed down by
friction with the ocean floor.
• The top of the wave is still moving forward,
traveling faster than the bottom.
• The momentum of the wave causes the top
to move past the bottom part of the wave.
• When this happens the wave topples over on
itself, forming a breaker.
Wind Waves Approaching Shore
What happens when wind waves break against the shore?
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Breaking Waves
• In general waves
break when the depth
of the water is a little
greater than the
height of the wave.
• A wave 30 cm high
will break in 40 cm
water.
Questions
• What causes most waves?
• What is a wave?
• How do the water molecules move in a
wave?
• What causes a breaker?