Key Terms for Second Test
The tide generating force of a body is proportional to the inverse of the distance between the body and the Earth to this power.
3
How often does a spring tide occur
every two weeks
What is the period of a lunar diurnal tide?
24 hours and 50 minutes
Range
differences in height between consecutive high and low waters
High Tide/ High Water?
Maximum Height reached by a rising tide
Low Tide/ Low Water
Lowest elevation reached by a falling tide
Tidal Datum
Mean low water. This is the reference level from which ocean depths and tide heights are measured; the zero tide level. The use of mean low water assures sailors that the water is generally higher than what is marked on the chart
Apogee
When the moon is furthest away from earth
Perigee
when the moon is closest to earth
Ebb Tide
Falling tide; the period of tide between high water and the next low tide
Flood Tide
the period of the tide between low tide and the next high tide. When the water is rising.
Amphidromic Point
the point from which the cotidal lines radiate on the chart; the nodal, or low amplitude point for rotary tide
Cotidal lines
Lines drawn on a chart to mark the location of a tidal crest a set intervals of time
corange lines
in a rotary tide, lines of equal tidal range about the amphidromic point
Slack Water
state of a tidal current when its velocity is near zero; occurs when the tidal current changes direction. This is when the tidal currents slow and then reverse. This can be the only time when vessels can safely navigate a narrow channel with swift tidal currents.
Syzygy
Straight line configuration of three celestial bodies (Sun, Moon Earth)
Spring Tide
Tides occurring during the times of the full and new moon, when the range of the tides is greatest. Spring tides occur approximately every two weeks.
Neap Tide
Tides occurring during the first and last quarters of the moon, when the range of the tides is least. This is when the lunar and solar tides are out of phase with one another and are interacting destructively.
Equilibrium Theory of Tides
Tides are studied as a mathematical ideal in which wave forms behave uniformly in response to the laws of physics. This is a non-rotating, water covered earth.
Dynamic Theory of Tides
Studies the tides as they actually occur on a rotating earth modified by landmasses and the geography of the ocean basins
Diurnal Tides
One high water and one low water each day.
Difference between the time period of lunar and solar tides.
Lunar tides have an extra 50 minutes tacked on because the moon moves and the sun does not.
lunar Semi-diurnal tide has a period of….
12 hours and 25 minutes
Semi-diurnal tide
Tide with two high waters and two low waters each day
mixed semi-diurnal tide
type of tide with large inequalities between the two high waters and two low waters which occur each day. (higher high tide and lower low tide)
Moon’s Declination
The angle between the moon’s orbit and the earth’s equator
Lunar Day/ Lunar Month
Time required for the moon to pass from one new moon to another new moon (29 days)
Solar Day
time period determined by one rotation of Earth relative to the Sun; the mean solar day is ?twenty-four hours
Tidal Day
?24 hours and 50 minutes long. This is because the moon is also moving and therefore the ?starting point will not be under to moon until the earth turns another 12° (50 minutes)?
Centripetal Acceleration ?
centripetal force – inward-directed force necessary to keep an object moving in a curved path ?or rotating about an axis.?
Mesotidal Coast
The mesotidal coast has a tidal range of between 2 and 4 meters. This is in between the other ?two classifications of tidal coasts
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