Coastal Geography, Tides Flashcards
Tide
Rise and fall of sea surface
What three forces control the Earth’s tides?
The gravitational pull of the Sun and Moon, and the rotation of Earth
Primary bulge
Occurs on the near side facing the moon due to gravity
Secondary bulge
Occurs on the far side not facing the moon due to inertia
Diurnal inequality
Two high or low tides in the same day of unequal size
What causes diurnal inequality?
Priamry bulge is larger than the secondary bulge
Why does high tide occur every 12 hours and 25 minutes?
Not only is the moon rotating, but the moon is also orbiting arund the Earth. The Earth has to ‘catch up’ with the Moon to return to high tide
Spring tide
Occurs when both the Sun and Moon are alligned either during new or full Moon
High tides ↑
Low tides ↓
Neap tide
Occurs when the Sun and Moon are at right angles to each other when the Moon is in its first or third quarter
High tides ↓
Low tides ↑
Perihelion
Earth nearest to Sun
Aphelion
Earth furthest from Sun
Perigee
Moon nearest to Earth
Apogee
Moon furthest from Earth
Tidal range
Difference in height between high and low tide
What classifies a micro, meso, and macrotidal range?
Micro: 0 - 2m
Meso: 2 - 4m
Macro: >4m
What is the general relationship between the lunar and solar tide?
The lunar tide is the ‘actual tide’ which is modified by the solar tide
Conjunction tide
Type of spring tide when the Sun and Moon are on the same side of the Earth
Opposition tide
Type of Spring tide when the Sun and Moon are on opposite sides of the Earth
Quadrature tide
A type of neap tide when the lunar and solar tide counteract each other
Coriolis force
Because of the Earth’s rotation, wind (and therefore currents) are deflected from a straight path.
Northern hemisphere: Deflect to the right
Southern hemisphere: Deflect to the left
How does continetial shelf affect tides?
Wide continential shelves have larger tidal ranges as wave shaoling causes crests to become amplified.
Contrarily, narrow continential shelves have smaller tidal ranges as the continential slope is far steeper, decreasing the period of amplification potential.
