Tides Flashcards
What are tides?
rise and **fall **of the water around the edge of the land
How are tides generated?
gravatational attraction and centrifugal attraction between Earth, Sun and moon
What waves are tides?
standing waves
How are standing waves created?
progressive wave **directly reflected **back on itself produces a **standing **wave.
Why are standing waves developed?
2 waves (original and reflected) are moving at** same speed** but different directions
What is the relationship between wave height and tidal range?
they are** equal** to each other
What tide does the crest indicate?
high tide
What tide does the trough indicate?
Low tide
Why are tides considered shallow waters?
wavelength is 1/2 the** circumfrence **of earth but the depth is less than 1/20 the wavelength?
What is flow?
When tides come in
What is ebb?
When the tide goes out
What is the relationship between the average distance between the moon and Earth?
their relationship is constant
How does the relationship in distance of moon and Earth stay constant?
Gravity and Inertia
What is gravity?
masses are attracted to one another
What is inertia?
tendency of **objects **to continue moving in a straight line
What parts of gravitational and centrifugal forces are constant?
inertia is constant, but the influence of gravity isn’t
What is the relationship between gravity force and inertia on the moon side?
gravity is more than** inertia**
What is the relationship between gravity force and inertia on the sun side?
Inertia is more than gravity
What are the assumptions of the equilibrium model?
- Earth is covered in H20
- Tide **waves **are progressive
- **Water **is in **equilibrium **with generating forces
How long is Lunar orbit?
about 27 days
What happens when a rotating moon causes a tidal day?
the moon moves while Earth rotates
How long is a full tidal cycle?
24 hours and 50 minutes for full tidal cycle
What is a sun tide?
Sun** produces** its **own tidal **wave
How long does it take for Earth to revolve on its axis with respect to the Sun?
about 24 hours
How do tides in sun tides produced by the Moon continuously?
**eastward **relative **to **the tide wave **produced **by the Sun
What is a spring tide?
**tides **are **higher **than the moon and is aligned with the sun
What are neap tides?
tides are **lower **
moon and sun are perpendicular
What is the tidal range?
the difference height between consecutive high and low waters
What is the tidal wave amplitude?
1/2 of the tidal range?
What is a king tide?
the greatest tidal effect of a year.
How are king tides created?
when the **orbits **and **alignment **of the
Earth, moon, and sun combine
What is declination?
Angle where the moon or sun orbits are offset from the equator due to elliptical orbital paths and** tilt **of the Earth
What determines the number of magnitude of tides?
location of Earth due to declination
What are tidal patterns?
tides behave differently in different places.
What is a diurnal tide?
1 high water and 1 low water each tidal day
What is a semi-dirurnal tide?
**two high waters **and **two
low waters **each tidal day.
How long is a semi dururnal tidal period?
12hours and 25minutes
How long is a diurnal tide period?
24 hours and 50 minutes
What is a mixed semi-diurnal tide?
**tides **reach different heights and low tides drop to different levels
What influences tidal range?
**constructive **and **destructive **wave interference
What does tidal theory doesn’t explain?
Earth turns eastward faster than tide moves freely
westward.
**Friction displaces tide crest **to the east of expected position
under moon
What are standing rotary waves?
tide that **results **in standing wave **moving **around central node of a basin
What does tidal theory not explain (2)?
- **Continents separate the oceans, the tide wave is
discontinuous. - Wave is contained within the ocean basins and
oscillates in the basin as a standing wave. - Reflected from continents.
- Refracted by changes in water depth.
- Diffracted as it passes through gaps/channels.
How do tides and currents turn in the North Hemisphere?
current:clockwise
tide:counterclockwise
How do tides and currents turn in the South Hemisphere?
currents: counterclockwise
tide:clockwise
What happens during the horizontal component of motion?
Because the horizontal time is long (0.5
period) Coriolis becomes important. NH deflected
Right and SH deflected left. Current has clockwise
rotation in NH and counter in SH.
Wat is the angle of declination?
28.5
