Warm Up 2/25/08Warm Up 2/25/081)1) What is true about an ocean current that is moving What is true about an ocean current that is moving

toward the equator?toward the equator?a. It is cold.a. It is cold. c. It is warm.c. It is warm.b. It is slow.b. It is slow. d. It is fast.d. It is fast.

2)2) The energy that drives surface ocean currents comes The energy that drives surface ocean currents comes from ____.from ____.a. salinity variationsa. salinity variations c. temperature differencesc. temperature differencesb. wave actionb. wave action d. windd. wind

3)3) Because of the Coriolis effect, ocean currents in the Because of the Coriolis effect, ocean currents in the Northern Hemisphere are deflected to the ____.Northern Hemisphere are deflected to the ____.a. lefta. left c. southc. southb. rightb. right d. northd. north

Answers: 1) a. 2) c. 3) b.Answers: 1) a. 2) c. 3) b.

Waves and TidesWaves and Tides

Chapter 16, Section 2Chapter 16, Section 2

WavesWaves

• Ocean waves are energy traveling Ocean waves are energy traveling along the boundary between ocean along the boundary between ocean and atmosphereand atmosphere

• Waves transfer energy through the Waves transfer energy through the ocean, that’s why even on a calm ocean, that’s why even on a calm day in the middle of the ocean there day in the middle of the ocean there may still be waves from a far off may still be waves from a far off stormstorm

WavesWaves

Wave CharacteristicsWave Characteristics• Most ocean waves obtain their energy and motion Most ocean waves obtain their energy and motion

from the windfrom the wind• Crests – the tops of the wavesCrests – the tops of the waves• Troughs – the bottoms of the wavesTroughs – the bottoms of the waves• Wave Height –Wave Height – the vertical displacement the vertical displacement

between crest and troughbetween crest and trough• Wavelength –Wavelength – the horizontal distance between the horizontal distance between

two successive crests or two successive troughstwo successive crests or two successive troughs• Wave Period –Wave Period – the time it takes one the time it takes one wavelengthwavelength

to pass a fixed positionto pass a fixed position• The height, length, and period that are eventually The height, length, and period that are eventually

achieved by a wave depend on three factors: (1) achieved by a wave depend on three factors: (1) wind speed; (2) length of time the wind has wind speed; (2) length of time the wind has blown; and (3) fetchblown; and (3) fetch

• Fetch –Fetch – distance that the wind has traveled distance that the wind has traveled across open wateracross open water

Concept CheckConcept Check

• From where do ocean waves obtain From where do ocean waves obtain their energy?their energy?

• WindWind

Wave MotionWave Motion

• Waves can travel great distances across Waves can travel great distances across ocean basinsocean basins

• As a wave travels, the water particles pass As a wave travels, the water particles pass the energy along by moving in a circle; so the energy along by moving in a circle; so the water doesn’t move, only the energythe water doesn’t move, only the energy

• Circular orbital motion allows energy to Circular orbital motion allows energy to move forward through the water while the move forward through the water while the individual water particles that transmit the individual water particles that transmit the wave move around in a circlewave move around in a circle

• The wind energy is not only transmitted The wind energy is not only transmitted along the surface, but also downwardalong the surface, but also downward

Anatomy of a WaveAnatomy of a Wave

Concept CheckConcept Check

• How does energy move by means of How does energy move by means of a wave?a wave?

• Circular orbital motion allows energy Circular orbital motion allows energy to move forward through a wave, to move forward through a wave, while the individual water particles while the individual water particles that transmit the wave move around that transmit the wave move around in a circle.in a circle.

Breaking WavesBreaking Waves

• As long as a wave is in deep water, it is As long as a wave is in deep water, it is unaffected by water depthunaffected by water depth

• When a wave approaches shore, the water When a wave approaches shore, the water becomes shallower and influences wave becomes shallower and influences wave behaviorbehavior

• As a wave advances on the shore, the As a wave advances on the shore, the slightly faster waves further out will catch-slightly faster waves further out will catch-up and decrease the wavelength, making up and decrease the wavelength, making the wave grow steadily higherthe wave grow steadily higher

• When a critical point is reached, the wave When a critical point is reached, the wave is too steep to support itself and the wave is too steep to support itself and the wave front collapses, or breaks, and the water front collapses, or breaks, and the water advances up the shoreadvances up the shore

Breaking WavesBreaking Waves

TidesTides• Tides are regular changes in the elevation Tides are regular changes in the elevation

of the ocean surfaceof the ocean surface• Other than waves, they are the easiest Other than waves, they are the easiest

ocean movements to observeocean movements to observe• Newton showed that there is a mutually Newton showed that there is a mutually

attractive force between any two bodies, attractive force between any two bodies, Earth and the moonEarth and the moon

• Ocean tides result from differences in the Ocean tides result from differences in the gravitational attraction exerted upon gravitational attraction exerted upon different parts of Earth’s surface by the different parts of Earth’s surface by the moon and, to a lesser extent, by the sunmoon and, to a lesser extent, by the sun

The Cause of TidesThe Cause of Tides

• The primary body that influences the tides The primary body that influences the tides is the moonis the moon

• The gravitational pull is greatest on the The gravitational pull is greatest on the side of Earth closest to the moon, causing side of Earth closest to the moon, causing Earth to be stretched slightlyEarth to be stretched slightly

• On the side of Earth closest to the moon, On the side of Earth closest to the moon, the pull of the moon’s gravity on the the pull of the moon’s gravity on the oceans is greater than it is on solid Earthoceans is greater than it is on solid Earth

• Water will flow towards this tidal “bulge”, Water will flow towards this tidal “bulge”, creating a high tidecreating a high tide

• As Earth rotates, it will go “through” the As Earth rotates, it will go “through” the tidal bulges, resulting in alternating high tidal bulges, resulting in alternating high and low tidesand low tides

Cause of TidesCause of Tides

Concept CheckConcept Check

• What force produces tides?What force produces tides?

• GravityGravity

Tidal CycleTidal Cycle• The sun also produces tidal bulges, slightly The sun also produces tidal bulges, slightly

smaller than those produced by the moonsmaller than those produced by the moon• The influence is most noticeable during The influence is most noticeable during

new and full moon phases (Earth-moon-sun new and full moon phases (Earth-moon-sun are aligned), causing larger tidal bulgesare aligned), causing larger tidal bulges

• Tidal Range –Tidal Range – the difference in height the difference in height between successive high and low tidesbetween successive high and low tides

• Spring Tides –Spring Tides – have the greatest tidal have the greatest tidal range due to the alignment of the Earth-range due to the alignment of the Earth-moon-sun system (new and full moons)moon-sun system (new and full moons)

• Neap Tides –Neap Tides – daily tidal range is less due daily tidal range is less due to the sun and moon acting against each to the sun and moon acting against each otherother

Spring TidesSpring Tides

Neap TidesNeap Tides

Tidal PatternsTidal Patterns• Tides at various locations respond differently Tides at various locations respond differently

to the tide-producing forcesto the tide-producing forces

• Three main tidal patterns exist worldwide: Three main tidal patterns exist worldwide: diurnal tides, semidiurnal tides, and mixed diurnal tides, semidiurnal tides, and mixed tidestides

• Diurnal Tidal Pattern –Diurnal Tidal Pattern – characterized by a characterized by a single high tide and a single low tide each tidal single high tide and a single low tide each tidal dayday

• Semidiurnal Tidal Pattern –Semidiurnal Tidal Pattern – characterized by characterized by two high tides and two low tides each tidal daytwo high tides and two low tides each tidal day

• Mixed Tidal Pattern –Mixed Tidal Pattern – characterized by a large characterized by a large inequality in high water heights, low water inequality in high water heights, low water heights, or bothheights, or both

Tidal PatternsTidal Patterns

Concept CheckConcept Check

• What are the three types of tidal What are the three types of tidal patterns?patterns?

• Diurnal, semidiurnal, and mixedDiurnal, semidiurnal, and mixed

Assignment (Due 2/28/08)Assignment (Due 2/28/08)

• Read Chapter 16 (pg. 448-467)Read Chapter 16 (pg. 448-467)

• Do Chapter 16 Assessment #1-30 (pg. Do Chapter 16 Assessment #1-30 (pg. 471-472)471-472)

• Print out “Investigation 16 – Shoreline Print out “Investigation 16 – Shoreline Features” for WednesdayFeatures” for Wednesday

Cool DownCool Down1)1) What celestial bodies influence Earth’s tides?What celestial bodies influence Earth’s tides?

• The moon and the sunThe moon and the sun

2)2) Explain how the forces of gravity and inertia Explain how the forces of gravity and inertia lead to tides in Earth’s oceans.lead to tides in Earth’s oceans.

• On the side of Earth closest to the moon, the On the side of Earth closest to the moon, the force of gravity is larger than that of inertia, force of gravity is larger than that of inertia, which creates a tidal bulge. On the side of which creates a tidal bulge. On the side of Earth opposite the moon, the force of inertia Earth opposite the moon, the force of inertia is greater than that of gravity, creating a is greater than that of gravity, creating a similar tidal bulge.similar tidal bulge.

3)3) What is one new thing you learned today? What is one new thing you learned today? Explain.Explain.