1. Objectives Ch. 4 Earth’s Structure and Motion
Explain the Nebular Theory for formation of the solar system.
Describe Earth’s size, shape, and arrangement of its layers.
List three sources for the Earth’s internal heat.
Describe Earth’s magnetic field.
Give evidence for Earth’s rotation on its axis
Relate Earth’s rotation to the day-night cycle and time zones.
Give evidence for Earth’s revolution about the sun.
Describe Earth’s path and rate of revolution.
Explain why seasons occur.

2. Chapter 4: Earth’s Structure and Motion
4.1: Earth’s Formation
4.2: Earth’s Rotation
4.3: Earth’s Revolution

3. 4.1: Earth’s Formation Origin of the Solar System
1. Nebular Hypothesis
Cloud of gas and dust rotating slowly
Rotation speed increased
Material gathered to its center

4. 4.1: Earth’s Formation Draw figure on pp 70-71
d. Interior (core) became very hot = hydrogen fusion = Sun born
e. Excess material went into space = planetesimals = beginning of Solar System
Draw figure on pp 70-71
Origin of the solar system.

5. 4.1: Earth’s Formation Earth's Size and Shape
Planetesimals collected more objects developing into planets/moons
What is a sphere called that bulges at the center?
How do we know that Earth is spherical shaped bulging at the center?
Oblate Spheroid
By measuring the weight of an object at several locations on earth

6. 4.1: Earth’s Formation 4. 149 million sq. km. (29%) is dry land
million sq. km. (71%) is covered by water
6. The total surface of Earth is ...
510 million KM=55 united states

7. 4.1: Earth’s Formation Earth's Interior
Space collisions have changed Earth to look the way it does presently

8. 4.1: Earth’s Formation 2. Layers of the Earth
Inner Core - Solid Iron and Nickel
Outer Core - Liquid Iron and Nickel
Mantle (thickest layer) Iron, Silicon, Magnesium
Asthenosphere - Slush like layer
Lithosphere - More rigid than the asthenosphere

9. 4.1: Earth’s Formation 3. Crust (earth's surface, thinnest layer) Rock
Earth's Heat
How did originally generate heat?
Why is earth loosing heat presently?
Meteorite impact, compression and Radioactive decay
Rocks lose heat to the atmosphere, crustal thickness varies, and radioactivity decreases with time.

10. 4.1: Earth’s Formation
3. Why does the temperature in caves remain constant?
4. After about 70 meters temperatures will begin to increase about 1o C every 40 m of depth
Because the sun’s warmth and winter’s cold cannot penetrate there.

11. 4.1: Earth’s Formation Earth's Magnetic Field
The North Pole attracts a compass needle - the positive end of a bar magnet
The South Pole repels a compass needle - the negative end of a bar magnet

12. 4.1: Earth’s Formation
C. The hypothesis explaining Earth's magnetic north/south is the liquid iron moving across Earth's weak magnetic field = a stronger magnetic field is produced

13. 4.2: Earth’s Rotation Evidence for Rotation
What is significant about Foucault's pendulum and it 11o shifts each hour?
It proves that the earth is rotating

14. 4.2: Earth’s Rotation
2. Evidence of Earth's rotation is seen in the Coriolis Effect - Northern Hemisphere winds are deflected to the right relative to Earth's surface; which way are winds deflected in the Southern Hemisphere?
To the Left

15. 4.2: Earth’s Rotation Axis and Rate of Rotation
Orbital Plane - an imaginary flat surface that Earth orbits the sun in.
Earth's axis lies at a 23.5o tilt to its orbital plane

16. 4.2: Earth’s Rotation
3. Why does the Earth rotate at different speeds at different latitudes?
Because points at the equator have farther to travel than points at the poles in the same amount of time.

17. 4.2: Earth’s Rotation Effects of Rotation
Earth rotates counterclockwise = Sun appears to rise in east

18. 4.2: Earth’s Rotation 2. Measuring time
Sidereal Day = 23 hours 56 minutes; Earth rotates 360o
Solar Day = 24 hours (sunrise to sunrise = 'true day'); Earth rotates ~ 361o
Solar Noon - the sun is at its highest point
Moves westward 1o every 4 minutes or 15o every hour = Time Zones

19. 4.2: Earth’s Rotation Effects of Rotation Standard Time Zones
Divisible by 15o or one hour = time meridian
Prime Meridian is in Greenwich
West of Greenwich time moves back (earlier)
East of Greenwich time moves forward (later)

20. 4.2: Earth’s Rotation 4. International Date Line
Change the date (not the time)
In the Pacific Ocean
Moving west = one day later
Moving East = one day earlier

21. 4.3: Earth’s Revolution Evidence for Revolution Revolution = Orbit
Different constellations are visible at different seasons (pp )
What is parallax and how can you demonstrate it with a pencil?
Apparent shift in position of distant objects. Hold a pencil up and look at it with one eye open. Then close that eye and look at it with your other eye open.

22. 4.3: Earth’s Revolution Path and Rate of Revolution
Earth's revolution is the same as it rotation, what direction is this?
The average distance the Earth is from the sun is 150,000,000 km (1 au)
Perihelion - when Earth is nearest the sun = million km; ~ January 2
Aphelion - when Earth is farthest away from the sun = million km; ~ July 4
Counterclockwise

23. 4.3: Earth’s Revolution
3. Zenith – the sun’s highest point in the sky at noon.
4. Zenith Angle - the angle between a point directly above the observer and the sun at zenith.
5. Altitude - Angular distance between the horizon and sun's position.
Sun is at its zenith = an altitude of ...
Sun at its horizon = an altitude of ...

24. 4.3: Earth’s Revolution C. Effects of Revolution & Tilt
In addition to Earth's revolution it’s tilt plays a large role in temperature, seasons, and days
Hemisphere tilted towards the sun = direct sunlight = warmer temperatures and longer days.

25. 4.3: Earth’s Revolution
B. Hemisphere tilted away from the sun = indirect sunlight = cooler temperatures and shorter days.
C. Summer Solstice - first day of summer, ~ June 21, longest day, Northern max tilt towards sun. North Pole = 24 hrs. of ... South Pole = 24 hrs. of ...

26. 4.3: Earth’s Revolution Effects of Revolution and Tilt
Winter Solstice - first day of winter, ~ December 21, shortest day, Northern max tilt away from sun.
North Pole = 24 hrs. of darkness
South Pole = 24 hrs. of daylight

27. 4.3: Earth’s Revolution
F. Vernal Equinox ~ March 21 / Autmnal Equinox ~ September 22
Both day and night are equal length
Neither hemisphere tilts towards the sun
Sun overhead the equator at noon