Tides Flashcards
What are the tidal periods?
12h25m, 24h50m
What is a diurnal tide?
1 high water and 1 low water
What is a semi-diurnal tide?
2 high waters and 2 low waters
What is a mixed tide?
unequal tides
How often is the tidal cycle?
fortnightly
What is the origin of the tides?
gravitational attractive forces between the earth and the moon (centripetal force) keeps them in mutual orbit.
What is the equilibrium tidal theory?
Earth is spherical and covered in a uniform ocean, action of gravitational force of moon on fluid elements surrounding the earth.
The net force is the tide generated force.
How do you work out the tide generated force?
mass of tide raising body / distance to tide raising body
When do spring tides occur?
When the earth, moon and sun form a straight line (syzygy)
tidal bulges act together
higher HW and lower LW
When do neap tides occur?
When the earth, moon and sun create an L shape (quadrature)
tidal bulges in opposition
What is the dynamic tidal theory?
constraining influence of land masses, frictional influence of rotating earth, deflection of tidal flow by the coriolis effect
What are rotary tidal systems?
assume enclosed basin in the northern hemisphere, high water travels anticlockwise - rotary wave (kelvin wave)
Amphidromic systems?
Join locations of equal tidal phase, cotidal lines
Join locations of equal tidal range, corange lines
Who invented the first tide calculating machine?
Lord Kelvin (1872)
