Unit 3: Waves and tides

Part 1 - Lesson 23: Waves

Teauhuapo

Intro to waves and tides Prezi wave comparison https://prezi.com/lumawvrgyp9v/edit/#1_24309637 Wave demonstration

Wave basics Where do ocean waves come from? Anything through which energy flows is called a medium. Ex: metal, string, water, land, air

Wave basics Where do ocean waves come from? A disturbance caused by the transfer of energy through a medium is called a wave. Source of energy for most waves is wind.

Wave Structure Crest – highest part of a wave Trough – lowest part of a wave Wave Height

Wave structure Wave height – vertical distance between a crest and its nearest trough. Amplitude – half of the wave height Wavelength – horizontal distance between two crests or troughs Wave Height

WAVELENGTH= horizontal distance (crest to crest) WAVE HEIGHT = vertical distance (crest to trough)

Wave basics If you look at the ocean in a cross section, surface wave would like a transverse wave. Transverse wave – motion of water is perpendicular to direction of wave

Wave basics It’s actually an orbital wave – water is moving a circular motion

Orbital motion The size of the orbit of the water particles increases with wavelength The orbit size decreases rapidly with depth Only "feel" waves to a depth of 1/2 of their wavelength

Wave basics Longitudinal wave – Motion of the water moves parallel to the flow of energy. Think slinky!

Longitudinal Transverse

𝑝𝑒𝑟𝑖𝑜𝑑= 1 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑂𝑅 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦= 1 𝑝𝑒𝑟𝑖𝑜𝑑 Wave calculations Period = time for wave to move 1 wavelength Frequency = number of waves passing fixed point Inverse relationship: 𝑝𝑒𝑟𝑖𝑜𝑑= 1 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑂𝑅 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦= 1 𝑝𝑒𝑟𝑖𝑜𝑑

Parts of a wave 20 seconds Period = time for wave to move 1 wavelength What is the period for the graph? a. b. 20 seconds

Parts of a wave Frequency = # of waves passing fixed point What is the frequency for the graph? 𝟏 𝟐𝟎 or 0.05 sec In 1 second, 1/20th of wave will pass point or takes 20 seconds for complete wave to pass point (typical wind driven ocean wave is 20 seconds or less)

What affects wave height? a. Wind speed b. Wind duration c. Fetch WAVE HEIGHT = vertical distance (crest to trough)

What affects wave height? 1. Wind speed How hard wind blows changes energy transfer & therefore wave height WAVE HEIGHT = vertical distance (crest to trough)

What affects wave height? 2. Wind duration How long wind blows changes energy transfer & therefore wave height

What affects wave height? c. Fetch Amount of ocean surface area affected by wind blowing in the same direction.

What causes a wave to break?

What affects how a wave breaks? Type of swell Wind direction Slope of sea bed Sea floor features

How does a wave break? Wave train approaches shore "feels" bottom at depth = 1/2 wavelength Bottom of wave slows even more as gets shallower, wave crest moves ahead of base of wave When depth of water is ½ of wave height, it will break.

Deep water vs. shallow water waves Deep Water waves The wave occurs in water deeper than half the wavelength. Not affected by seafloor Shallow Water waves Waves enter water that is equal to or less than 1/20 the wavelength

Types of Waves Spilling breaker: Found at gently sloping bottom. Plunging breaker: Found at moderate sloping bottom. Surging breaker: So steep that wave doesn’t break until right at shoreline. S

Training to survive big waves

More Types of waves Tsunami – caused by plate shift on seafloor causing a major displacement of water Malaysia tsunami Click

Tsunami

tsunami

tsunami

More Types of waves Rogue waves – Waves come together in positive interference

Rogue waves often involve more than two wave crests combining Rogue waves often involve more than two wave crests combining. In some cases, rogue waves seem to be generated when waves interact with strong surface water currents. Researchers model rogue waves as a non-linear process, meaning they do not involve simple wave crest addition, but more complex interactions of wave energy

Lesson 24: Tides

Tides Causes Moon’s gravity Centrifugal force Sun’s gravity

The Sun affects the Earth because it is so large, while the Moon's proximity to Earth is the main reason for its role in the tidal cycle.

High and low tide High Tide: Low Tide: Occurs when the body of water is in line with the moon. Highest point water reaches onto shore. Low Tide: Occurs when the body of water in perpendicular to the moon. Lowest point water reaches onto shore.

Tidal range: Distance between high and low tide. Affected by moon phase.

Organisms must adapt to tidal range. Ex: Sea turtles lay their eggs above the highest high tide.

Largest tidal range in the world – bay of fundy Tidal range = 16m or 52 feet

Tidal range This photo is a double exposure (a photographic technique where a film is exposed twice, thus superimposing one image on top of another) of the NOAA Ship Fairweather docked at a pier in Anchorage, Alaska. The two photos were taken from the same location, capturing the ship at both high tide and low tide. The tidal range was between 9 and 11 meters (~30– 36 feet).

Tidal movement Flood tide: Water moving onshore from low to high tide. “Tide is coming in”

Tidal movement Ebb tide: Water moving offshore from high to low tide. “Tide is going out”

Flood tide Ebb tide

3 basic patterns of tides Semidiurnal tide pattern Most areas on Earth experience this type Two high tides and two low tides per day

3 basic patterns of tides Diurnal tide cycle One high and one low tide per day

3 basic patterns of tides Mixed Tide pattern Two highs and two lows per day but one set of tides is more dramatic than the other.

2 types of tides 1) Spring Tide Sun and moon line up and pull in the same direction Greatest tidal variation between high and low Occurs twice a month New and full moon

tides 2) Neap Tide Sun and Moon are lined up perpendicular (partially cancelling each other out) Least tidal variation