section 2 and 3 ocean waves and tides chapter 11 the oceans
TRANSCRIPT
Section 2 and 3Section 2 and 3Ocean Waves and TidesOcean Waves and Tides
Chapter 11Chapter 11
The OceansThe Oceans
WavesWaves
•A A WaveWave is the movement of is the movement of energyenergy through a body of water through a body of water
• In oceans, waves move through In oceans, waves move through seawater.seawater.
•Most waves form when winds Most waves form when winds blowing across the water’s blowing across the water’s surface transmit their energy to surface transmit their energy to the water.the water.
WavesWaves
Caused byCaused by::
•WindWind
•EarthquakesEarthquakes
•Gravitational force of the Gravitational force of the Moon and Sun.Moon and Sun.
Waves Caused by WindWaves Caused by Wind
•When wind blows across a body of When wind blows across a body of water, water, frictionfriction causes the water to causes the water to move along with the wind.move along with the wind.
•Wave Height depends on – Wave Height depends on – – Strength of the windStrength of the wind– Length of time the wind blowsLength of time the wind blows– Distance over which the wind blowsDistance over which the wind blows
Parts of a WaveParts of a Wave
• CrestCrest – highest point of a wave – highest point of a wave• Trough Trough – lowest point of a wave– lowest point of a wave• Wave HeightWave Height – vertical distance – vertical distance
between the crest and the troughbetween the crest and the trough• WavelengthWavelength – horizontal distance – horizontal distance
between two crests or two troughsbetween two crests or two troughs• FrequencyFrequency – the number of waves that – the number of waves that
pass a point in a certain amount of pass a point in a certain amount of timetime
Wavelength
Wave Height
Crest
Trough
Still Water
Wave Parts
Wave MovementWave Movement
•When a wave breaks against When a wave breaks against the shore, the shore, the crest outruns the the crest outruns the trough and the crest collapses.trough and the crest collapses.
•Called aCalled a breaker. breaker.
•In this case, water does move In this case, water does move forward and backward.forward and backward.
Wave MovementWave Movement
• Waves slow down when they get Waves slow down when they get close to shore because friction close to shore because friction between the ocean floor and the between the ocean floor and the water causes them to slow down.water causes them to slow down.
• When the bottom of the wave slows When the bottom of the wave slows down, the tops keep moving forward down, the tops keep moving forward until the waves topple over.until the waves topple over.
Wave MovementWave Movement
•When a wave passes through When a wave passes through the ocean, the ocean, individual water individual water molecules move up and down molecules move up and down but they do not move forward but they do not move forward or backward.or backward.
TidesTides
• The rise and fall in sea level is called The rise and fall in sea level is called a a tidetide..
• Caused by the Caused by the interaction of interaction of the Earth, the moon, and the Earth, the moon, and the sunthe sun..
• One low-tide/high-tide cycle takes One low-tide/high-tide cycle takes about 12 hrs and 25 min.about 12 hrs and 25 min.
• Tidal rangeTidal range is the is the difference in ocean difference in ocean levellevel between high-tide and low-tide between high-tide and low-tide
What is the Tidal Range?What is the Tidal Range?
•HT = 30 ft, LT = 20 ftHT = 30 ft, LT = 20 ft
•HT = 20 ft, LT = 12 ftHT = 20 ft, LT = 12 ft
•HT = 50 ft, LT = 20 ftHT = 50 ft, LT = 20 ft
Gravitational Effect of the Gravitational Effect of the MoonMoon
•Two big bulges of water form Two big bulges of water form on the Earth: (tidal bulge)on the Earth: (tidal bulge)– one directly under the moon one directly under the moon – another on the exact opposite another on the exact opposite
sideside
•As the Earth spins, the bulges As the Earth spins, the bulges follow the moon.follow the moon.
Gravitational Effect of the Gravitational Effect of the SunSun
•Spring TidesSpring Tides– Earth, Moon, and Sun are lined Earth, Moon, and Sun are lined
upup– High Tides are higher and Low High Tides are higher and Low
Tides are lower than normalTides are lower than normal– Occurs during a new moon or Occurs during a new moon or
full moonfull moon
Gravitational Effect of the Gravitational Effect of the SunSun
•Neap TidesNeap Tides– Earth, Moon, and Sun form Earth, Moon, and Sun form
right anglesright angles– High Tides are lower and Low High Tides are lower and Low
Tides are higher than normalTides are higher than normal– Occurs during 1Occurs during 1stst qtr. Moon or qtr. Moon or
33rdrd qtr. moon qtr. moon
Tides Q & ATides Q & A• What are tides caused by?What are tides caused by?• Which exerts stronger gravitational pull on Which exerts stronger gravitational pull on
earth, the sun or the moon?earth, the sun or the moon?• What happens when the moon faces one What happens when the moon faces one
side of the earth?side of the earth?• What is a spring tide?What is a spring tide?• What position do the sun and moon have What position do the sun and moon have
to be into create a spring tide?to be into create a spring tide?• Explain a neap tide.Explain a neap tide.• In most places on earth, how often do high In most places on earth, how often do high
and low tides occurand low tides occur• How long does it take the moon to How long does it take the moon to
completely rotate around the earthcompletely rotate around the earth
Complete the “Types of Complete the “Types of Tides” worksheetTides” worksheet
The EndThe End