Waves and things

Homework Due Tuesday Read Pages Answer in complete sentences What causes the Coriolis effect? How does the Coriolis effect wind in the northern hemisphere? How is that different than its affect in the southern hemisphere? How does the Ekman Spirial relate wind speed to water depth? What do Gyers do? What does the book mean when it says “(Gyers) act like a giant thermostat”? What happens when waves “pile up” ? What do you call it when they fall forward and break? Where is the wave’s energy transferred to when the wave breaks?

The oceans are in constant motion. The most obvious examples of this along the shoreline are waves. In this lecture we will learn about: The oceans are in constant motion. The most obvious examples of this along the shoreline are waves. In this lecture we will learn about: –The properties of ocean waves –Wind generation of waves –Wave motion –The life history of ocean waves –Beach and shoreline processes –Waves behave like………waves

Properties of Ocean Waves

An ocean wave is an undulation of the sea surface. Important wave terms to know: An ocean wave is an undulation of the sea surface. Important wave terms to know: –Wave crest – The top of the wave –Wave trough- The bottom of the wave –Wave height-measure between crest and trough –Wavelength – measure between crests –Wave period – time it takes for a wave to move past a given point Progressive waves move across the sea surface. Progressive waves move across the sea surface. Standing waves oscillate about a fixed point. Standing waves oscillate about a fixed point.

Parts of a Wave

The “top” of the wave is the 1. Wavelength 2. Crest 3. Trough 4. Period

The “bottom” of the wave is the 1. Trough 2. Crest 3. Wavelength 4. Period

The distance between the crests is the 1. Period 2. Crest 3. Amplitude 4. Wavelength

Fastest Responders (in seconds) 12.71Brett Nelson 13.95John Drenga 14.4Alejandro Rivera 16.7Brian Stam

Waves are caused by different factors. Waves are caused by different factors. –Wind –Submarine disturbances such as earthquakes or landslides (tsunamis) –Gravitational attraction of sun and moon (tides)

Wind Generation of Waves The size and character of wind-generated ocean surface waves is determined by: The size and character of wind-generated ocean surface waves is determined by: Wind velocity – Wind Speed Wind velocity – Wind Speed –Wind duration – How long does it last –Fetch - distance the wind blows over the water Simply put, wave size increases as the strength (speed) and duration of the wind, and distance over which it blows increases. Simply put, wave size increases as the strength (speed) and duration of the wind, and distance over which it blows increases.

The relationship between wind speed and wave height

Largest recorded storm wave height: 112 feet/34.2 m height: 112 feet/34.2 m period: 14.8 s period: 14.8 s speed: 90 ft/s/27 m/sec = 61 mph speed: 90 ft/s/27 m/sec = 61 mph wavelength = 1100 ft/329 m wavelength = 1100 ft/329 m

The distance wind blows over water is called the 1. Crest 2. Duration 3. Fetch 4. Incline

Waves height is determined by wind speed, fetch and 1. Direction 2. Temperature 3. Dewpoint 4. Duration

A landslide could cause a ______ wave 1. Tide 2. Progressive 3. Tsunami

Fastest Responders (in seconds) 2.95Brett Nelson 7.55Brian Stam

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Wave Motion

Wind-generated waves are progressive waves progressive waves because they travel across the sea surface. There are two basic motions associated with an ocean wave: – –the forward movement of the wave form – –the orbital motion of water particles beneath the wave It is the wave energy not water molecules themselves that moves across the sea surface.

Wave Motion The motion of water particles beneath waves. Forward Movement Orbital movement

Wave Motion In deep water most waves do not interact with the sea bottom and are called deep-water waves. The orbits of the water molecules are circular.

Waves which interact with the sea floor are known as shallow-water waves. The orbits of the water molecules become elliptical – friction, slow. (Shallow-water waves can occur in the deep ocean if the wavelength is long enough.)

WAVE DEPTH WAVE DEPTH Wave depth is one half of the wavelength. Wave depth is one half of the wavelength. If the wavelength is 20 meters the depth is 10m If the wavelength is 20 meters the depth is 10m

Life History of Ocean Waves getting closer to the shore….. transforms the wave’s properties. In shallow water the sea bottom transforms the wave’s properties. Bottom friction alters both – –Wave form – – Speed (Celerity)

The two types of motion found in waves are 1. Forward and Backward 2. Orbital and Downward 3. Forward and Downward 4. Forward and Orbital

Waves that interact with the ocean floor are called 1. Shallow water waves 2. Deep water waves 3. Orbital waves 4. Fetch

Waves that do not interact with the ocean floor are called 1. Deep water waves 2. Shallow water waves 3. Orbital waves 4. Fetch

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As waves enter shallow water As waves enter shallow water –Wavelength shortens –Height increases –Speed decreases PERIOD REMAINS THE SAME What is the one factor that determines the wave speed of shallow water waves? DEPTH

Notice how waves bunch together as they approach shore. This is because the waves in shallower water travel slower than the waves behind in deeper water. FRICTION Height increases Speed Decreases Wavelength Decreases

Deep/Shallow Waves Depth = 1/20 th wavelength Ocean bottom does not affect the wave The wave comes into contact with the bottom and slows down the wave. Wave height increases Top of wave moves faster than the bottom of the wave and the wave breaks

As a wave moves to shore 1. Speed increases 2. Speed decreases 3. Speed remains the same

As a wave moves to shore 1. Height increases 2. Height decreases 3. Height remains the same

As a wave moves to shore 1. Period increases 2. Period decreases 3. Period remains the same

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Waves ultimately break when the top of the wave gets ahead of the bottom of the wave due to more friction at the bottom. The depth is usually 1.3 times the wave height = 1/7 th of the wavelength

Spilling breaker – wide, flat Plunging breaker – narrow, steep Surging breaker – V. narrow, V. steep The type of breaker formed is determined by the steepness of the surf zone.

Mr. Salmore

Waves may not break, but instead can be reflected off near vertical surfaces producing outgoing waves.

Wave refraction Wave refraction refers to the bending of the wave crest as waves enter shallow water. It is due to differences in speed produced by differences in water depth. Shallower area

Effects of wave refraction

Wave Refraction

Wave Diffraction

Summary Waves are disturbances that move along or beneath the sea surface. Waves are disturbances that move along or beneath the sea surface. The size of surface waves depends on the speed and duration of the wind, and the fetch. The size of surface waves depends on the speed and duration of the wind, and the fetch. Waves affect water to a depth equal to or less than one-half their wavelength. Waves affect water to a depth equal to or less than one-half their wavelength.

Summary As waves enter shallow water their wavelength shortens and their height increases. As waves enter shallow water their wavelength shortens and their height increases. The most damaging effect of storms is not necessarily the waves, but the storm surge (elevated sea level) created by the winds which pile water up along the shore. The most damaging effect of storms is not necessarily the waves, but the storm surge (elevated sea level) created by the winds which pile water up along the shore.