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
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
• 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.
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. 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:
• 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