1. Warm Up 2/25/08
What is true about an ocean current that is moving toward the equator?
a. It is cold. c. It is warm.
b. It is slow. d. It is fast.
The energy that drives surface ocean currents comes from ____.
a. salinity variations c. temperature differences
b. wave action d. wind
Because of the Coriolis effect, ocean currents in the Northern Hemisphere are deflected to the ____.
a. left c. south
b. right d. north
Answers: 1) a. 2) c. 3) b.

2. Waves and Tides
Chapter 16, Section 2

3. Waves
Ocean waves are energy traveling along the boundary between ocean and atmosphere
Waves transfer energy through the ocean, that’s why even on a calm day in the middle of the ocean there may still be waves from a far off storm

4. Waves

5. Wave Characteristics
Most ocean waves obtain their energy and motion from the wind
Crests – the tops of the waves
Troughs – the bottoms of the waves
Wave Height – the vertical displacement between crest and trough
Wavelength – the horizontal distance between two successive crests or two successive troughs
Wave Period – the time it takes one wavelength to pass a fixed position
The height, length, and period that are eventually achieved by a wave depend on three factors: (1) wind speed; (2) length of time the wind has blown; and (3) fetch
Fetch – distance that the wind has traveled across open water

6. Concept Check
From where do ocean waves obtain their energy?
Wind

7. Wave Motion Waves can travel great distances across ocean basins
As a wave travels, the water particles pass the energy along by moving in a circle; so the water doesn’t move, only the energy
Circular orbital motion allows energy to move forward through the water while the individual water particles that transmit the wave move around in a circle
The wind energy is not only transmitted along the surface, but also downward

8. Anatomy of a Wave

9. Concept Check How does energy move by means of a wave?
Circular orbital motion allows energy to move forward through a wave, while the individual water particles that transmit the wave move around in a circle.

10. Breaking Waves
As long as a wave is in deep water, it is unaffected by water depth
When a wave approaches shore, the water becomes shallower and influences wave behavior
As a wave advances on the shore, the slightly faster waves further out will catch-up and decrease the wavelength, making the wave grow steadily higher
When a critical point is reached, the wave is too steep to support itself and the wave front collapses, or breaks, and the water advances up the shore

11. Breaking Waves

12. Tides Tides are regular changes in the elevation of the ocean surface
Other than waves, they are the easiest ocean movements to observe
Newton showed that there is a mutually attractive force between any two bodies, Earth and the moon
Ocean tides result from differences in the gravitational attraction exerted upon different parts of Earth’s surface by the moon and, to a lesser extent, by the sun

13. The Cause of Tides
The primary body that influences the tides is the moon
The gravitational pull is greatest on the side of Earth closest to the moon, causing Earth to be stretched slightly
On the side of Earth closest to the moon, the pull of the moon’s gravity on the oceans is greater than it is on solid Earth
Water will flow towards this tidal “bulge”, creating a high tide
As Earth rotates, it will go “through” the tidal bulges, resulting in alternating high and low tides

14. Cause of Tides

15. Concept Check
What force produces tides?
Gravity

16. Tidal Cycle
The sun also produces tidal bulges, slightly smaller than those produced by the moon
The influence is most noticeable during new and full moon phases (Earth-moon-sun are aligned), causing larger tidal bulges
Tidal Range – the difference in height between successive high and low tides
Spring Tides – have the greatest tidal range due to the alignment of the Earth-moon-sun system (new and full moons)
Neap Tides – daily tidal range is less due to the sun and moon acting against each other

17. Spring Tides

18. Neap Tides

19. Tidal Patterns
Tides at various locations respond differently to the tide-producing forces
Three main tidal patterns exist worldwide: diurnal tides, semidiurnal tides, and mixed tides
Diurnal Tidal Pattern – characterized by a single high tide and a single low tide each tidal day
Semidiurnal Tidal Pattern – characterized by two high tides and two low tides each tidal day
Mixed Tidal Pattern – characterized by a large inequality in high water heights, low water heights, or both

20. Tidal Patterns

21. Concept Check What are the three types of tidal patterns?
Diurnal, semidiurnal, and mixed

22. Assignment (Due 2/28/08) Read Chapter 16 (pg. 448-467)
Do Chapter 16 Assessment #1-30 (pg )
Print out “Investigation 16 – Shoreline Features” for Wednesday

23. Cool Down What celestial bodies influence Earth’s tides?
The moon and the sun
Explain how the forces of gravity and inertia lead to tides in Earth’s oceans.
On the side of Earth closest to the moon, the force of gravity is larger than that of inertia, which creates a tidal bulge. On the side of Earth opposite the moon, the force of inertia is greater than that of gravity, creating a similar tidal bulge.
What is one new thing you learned today? Explain.