1 of 8

Slide Notes

TIDAL DAY
The moon does not stay put, but rotates around the earth at a rate of about 12° a day, or one rotation a month.
The rotation is in the same direction as the earth’s spin, so by the time the earth has done one rotation, the moon has shifted 12° further, and it takes an extra 50 minutes for the moon to be in the same position relative to a point on the earth.
Therefore, the tidal cycle is not 24 hours long, but 24 hours and 50 minutes. Because of this, high and low tides are about 50 minutes later every day.

SEMI DIURNAL
As the earth turns upon its own axis in about 24 hours, a point on the earth moves through areas with these different forces acting on it.
nIn one rotation (one day), a point on earth travels from an area of high tide (where there is a force pulling water outward), through an area of low tide, through an area of high tide again (the opposite pull), and through another area of low tide, before it returns to the point of origin at high tide.
nThis results in two high tides and two low tides in a day (called semidiurnal tides).
DownloadGo Live

How do we get tides

Published on Nov 21, 2015

No Description

View Outline

MORE DECKS TO EXPLORE

PRESENTATION OUTLINE

1.

HOW DO WE GET TIDES?

TIDAL DAY
The moon does not stay put, but rotates around the earth at a rate of about 12° a day, or one rotation a month.
The rotation is in the same direction as the earth’s spin, so by the time the earth has done one rotation, the moon has shifted 12° further, and it takes an extra 50 minutes for the moon to be in the same position relative to a point on the earth.
Therefore, the tidal cycle is not 24 hours long, but 24 hours and 50 minutes. Because of this, high and low tides are about 50 minutes later every day.

SEMI DIURNAL
As the earth turns upon its own axis in about 24 hours, a point on the earth moves through areas with these different forces acting on it.
nIn one rotation (one day), a point on earth travels from an area of high tide (where there is a force pulling water outward), through an area of low tide, through an area of high tide again (the opposite pull), and through another area of low tide, before it returns to the point of origin at high tide.
nThis results in two high tides and two low tides in a day (called semidiurnal tides).
Photo by Clinton Steeds
2.

WHAT ARE TIDES?

The periodic rise and fall of the sea level under the gravitational pull of the moon.

•The Moon’s gravity exerts a strong pull on Earth.
•The water bulges outward as Earth and the Moon revolve around a common center of mass.
The moon’s gravity pulls on the earth, and pulls the water towards it. The water moves up into a slight bulge on the side of the earth that faces the moon.
3.

Untitled Slide

The sun’s pull can heighten the moon’s effects or counteract them, depending on where the moon is in relation to the sun.

The tides are periodic oscillations in the level of the sea which come about as a result of the attraction of the Sun and the Moon on the liquid particles of oceans. The effects of the celestial bodies superimpose and the result constitutes the generating force of the tides.

Photo by Luz Adriana Villa A.
4.

NEAP TIDES

Neap tides are especially weak tides.
Moon & Sun are perpendicular to each other.
Moon & the Sun’s gravity cancel each other out.
They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons.
5.

SPRING TIDES

Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon.

The Moon & the Sun’s gravitational force combine to create a particularly strong tide.
6.

SIR ISAAC NEWTON

Sir Isaac Newton (1642 -1727) was the first person to explain tides scientifically. His explanation of the tides (and many other phenomena) was published in 1686.
7.

Untitled Slide

8.

Untitled Slide

#1 - The sun, moon and earth are in a direct line=Spring tide.

#2 - Neap= sun and moon are perpendicular to each other, thus less gravitational pull.

#3 - Spring

#4 - Neap

NCVPS STEM