Tides and Current Flashcards
Tide is
the vertical movement of water on the Earth’s surface
Who and when determined gravity caused tides
Sir Issac Newton in 1687
Flood current
The incoming tide along the coast and into the bays and estuaries
When is the sun at its minimum declination? and what does that mean?
The sun is at it’s minimum declination during the vernal (March 21) and autumnal (September 23) equinoxes when it is directly over the equator.
Aphelion
Earth is furthest from the sun, around July 2, the tidal ranges are below normal.
Tides are very long period
waves that move through the oceans due to the forces exerted by the moon and sun
Tides in narrow inlets and shallow water are
Disappated
Spring tides occur _____.
When the Sun, Moon, and Earth are nearly in line
What causes high tides?
The moon pulls the water most strongly below it on the earth, which is high tide. One the opposite side of the Earth, there is another bulge where the moon has the weakest gravity. These are the places where high tides occur. The weather spins through this, which causes tides in different areas https://scijinks.gov/tides/tides6.png.
When the sun and moon are at right angles to each other, which type of tides occur?
Neap
What causes low tides?
The moon pulls the Earth’s oceans towards it, creating a football shaped phenomena with bulges nearest to and furthest from the moon. The flat sides of the football are the areas of low tide, and the Earth spinning causes this to happen in different places.
Where are the water bulges caused by extraterrestrial gravity on the Earth
One forms when the sun and moon are closest and the other where they are furthest apart. They stay alleged with the moon as the Earth rotates. The opposite to the moon bulge is due to inertia
Spring tides
Sun and moon are in alignment, whether on the same side of opposite side. The high tides are the highest and the low tides are the lowest.
Diurnal tide
Only one high tide and one low tide daily. In th eU.S., this is most common on the Gulf Coast.
How many high waters usually occur each day on the East Coast of the United States?
Two
Frequency of tides in the lunar day
most coastal areas in the U.S. have two high tides and two low tide every lunar day.
Apogee
The moon is furthest from the Earth (about two weeks after Perigee) and tidal ranges are below average
Ebb Current
the outgoing tide
Mixed semidiurnal tide
the high tides and low tides differ in height. Most common on the West Coast
Slack water
the period of time, usually brief, when there is no current flow near the time of high and low tide, prior to the change in direction
The reference datum used in determining the heights of land features on most charts is _____.
mean high water
Neap tides occur _____.
When the Sun and Moon are at right angles to each other
Perihelion
The Earth is closet to the sun (jan 2) the tidal ranges are greater.
A lunar day is how long?
A lunar day is 24 hours and 50 minutes because the moon revolves around the Earth in the same direction that the Earth rotates around it’s axis so it takes the Earth and extra 50 minutes to “catch up” to the moon.
Funnel-shaped bays, like the Bay of Funny in Nova Scotia
can alter tides in this case increasing it to the highest tides in the world, over 15 meters.
The strongest flood and ebb currents generally occur around
half-tide or halfway between high and low tide
Neap Tides
Sun and moon are at right angles. The high tides are lower and the low tides are higher
What should you apply to a fathometer reading to determine the depth of water?
Add the draft of the vessel
When the sun and moon are in alignment, what type of tides will occur?
Spring
The strongest flood and ebb currents generally occur _____.
around half tide
Spring tides are tides that _____.
Have lower lows and higher highs than normal
Tides can also be affects by
local wind and weather patterns…winds can blow water around. Low pressure fronts can depress sea levels and low pressure fronts can cause tides to be much higher than predicted.
On the east coast of North America, charted depths are taken from _____.
mean lower low water
Tidal Range
The difference in height between the high tide and the low tide
The type of tide that occurs twice daily is called _____.
semi-diurnal
The Moon’s declination is
The change in it’s angle in relation to the equator. The two tidal bulges track the changes in lunar delineation, although increasing or decreasing their angles to the equator
The major force that causes tides is
gravity
The Sun’s declination affects
the seasons and the tides
The term tide refers to _____.
Vertical movement of the water
When is the sun at its maximum declination
The summer (June 21) and winter (December 22) solstices, which is it at it’s larges angle to the equator.
he period at high or low tide during which there is no movement of the water is called _____.
Slack water
Due to the relatively close distance, which outweighs the effects of mass, the ______ is the dominant force affecting the Earth’s tides
Moon. Although the sun is 27 million times more massive than the moon, it is 390 times further away. This reduced the sun’s force by 3903 (59 million times) so that is the half of the moon’s.
The difference between the heights of low and high tide is the _____.
range
Semidiurnal tides
When the two high tides and the two low tides are about the same heights. In the U.S. the is more common on the East Coast
Why are there three tidal patters around the world?
Large continents block the westward passed of the tidal bulges as the Earth rotates making complex patterns within each ocean basin. Most areas still have two high and two low tides each day.
In Estuaries with strong river flow
the current of the river may
When navigating a vessel, you _____.
Should never rely on a floating aid to maintain its exact position
Current
The horizontal movement of water which accompanies the rising and falling of the tide.
Perigee
The moon is closest to the Earth and as such tidal ranges are above average.
The lunar or tidal day is _____.
About 50 minutes longer than the solar day
