7/29/2019 Geo 12 Chapter III - The Earth in Motion

1/4

Chapter III: The Earth in Motion

Spinning

- The galaxy, sun, earth are spinning

- The earth is moving around the sun, while spinning around itself

- March 20-21 Vernal Equinox

- June 20-22 Summer Solstice

- From the previous slide it can be seen that as the earth revolves around

the sun it does not do so in a perfect circle.

- The earths orbit is elliptical

- The density of the earth combined with the spinning of the earth on its

axis causes it to go in this shape.

- The gravity of the sun causes the earth to try and adjust its orbit.

- The earth is at its greatest distance from the sun on July 4th

- This is the aphelion

- The earth is at closet distance from the sun on January 3rd.

- This is its perihelion

- As was mentioned before, this situation changes

- The cycle is approximately 21000 - 22000 years

- This shift is called the precession of the equinoxes

- These variation sun distance account for the differing temperatures on the

earth

- The eccentricity of the earth is the elliptical nature of the orbit

- As was mentioned before, the spinning of the earth, the differences in

axis and other factors mean that the earths orbit is not circular

- Since the earth is constantly trying to correct its orbit, it goes from

elliptical to near circular and then back to elliptical

- This is the eccentricity

- It goes through this cycle every 100,000 years or so.

- Add on to all this movement, the tilting of the earth on its axis.

7/29/2019 Geo 12 Chapter III - The Earth in Motion

2/4

- The tilt of the axis causes the seasons

- Each of the seasons, the tilt causes one or the other hemisphere to be

more inclined towards the sun

- This increases the amount of solar radiation the the hemisphere receives

- The solstice is when the sun is at its maximum position over the tropic

- That is the most northerly or southerly position of the sun

- The length of day also influences the amount of solar radiation that a

hemisphere receives.

- This also influences the temperature

- Another factor is the amount of land mass.

- As the earth tilts, the tilt actually varies

- The tilt varies between 21.5 degrees and 24.5 degrees

- The change occurs every 40,000 years or so and is called the wobble.- What is the correlation between the tilt, orbit and axis to the earth's ice

ages?

- According to Milankovich.The Coriolis effect

- The spinning of the earth also has an effect at the surface level.

- If the earth were a featureless surface, the friction caused by the surface

of the earth would have minimal influence

- The fact that the earth has mountains, land, surging water and other

features means that the spinning of the earth influences winds that blow

across the surface.

7/29/2019 Geo 12 Chapter III - The Earth in Motion

3/4

- Where do you think is the most observable place for this phenomenon? -

Toilets

- In the northern hemisphere, things end up to the right where of they

were aimed

- Southern hemisphere to the left- The Coriolis force or effect causes the distortion of the winds and energy

as it flows towards the equator.

- What industry must take this into account? - The airline industry

Time Zones

- The final topic is the time zones that divide the earth.

7/29/2019 Geo 12 Chapter III - The Earth in Motion

4/4

- Who originated the idea of time zones

- Sandford Fleming