1. Earths Structure and Motion Chapter 4

2. Chapter 4.1 – Earth’s Formation

3. Geology
The study of the planet Earth, its structure and composition and how it has changed over time

4. Origin of the Solar System

5. Nebular Hypothesis Image (a)
4.6 Billion years ago a cloud of dust and gas was rotating slowly
Cloud was at least 10 billion kilometers in diameter

6. Image (b)
The cloud shrank under the pull of its own gravity
As it shrank the rotation increased
Material in the rotating cloud gathered around its center

7. Image (c)
The compression of material made its interior VERY HOT
Caused hydrogen fusion to occur
A star was born
 the SUN

8. Image (d)
A platelike disc formed around the sun
It began to condense, forming solid particles of ice and rock
Eventually combined into larger bodies call planetesimals.

9. Image (e)
Planetesimals continued to compress and spin, while colliding with other objects
Eventually became planets and moons

10. Summarize in your own words the Nebular Hypothesis

11. Earth’s Location
The third closest planetesimal to the sun became Earth

12. Earth’s Size and Shape Earth is not a perfect sphere
It bulges in the center = oblate spheroid

13. Earth’s Size Total surface area = 510 million square kilometers
29% = Dry Land
71% = Covered by water

14. Earth’s Interior Multiple impacts caused early Earth to heat up
Heavy elements such as Iron & Nickel melted
Separated into layers – denser materials located in the center

15. Inner Core – Solid iron and nickel

16. Inner Core – Solid iron and nickel
Outer Core – Liquid iron and nickel

17. Inner Core – Solid iron and nickel
Outer Core – Liquid iron and nickel
Mantle – Thickest layer, solid & some liquid, iron, silicon, and magnesium.

18. Inner Core – Solid iron and nickel
Outer Core – Liquid iron and nickel
Mantle – Thickest layer, solid & some liquid, iron, silicon, and magnesium.
Crust – rigid layer of rocks – Earths surface

19. Lithosphere: the crust and uppermost portion of the mantle
Asthenosphere: thin slushlike layer of the mantle
Lithosphere floats on top of the
Asthenosphere

20. EARTH’S HEAT Generated from meteorite impacts and compression
Decay of radioactive isotopes
Elements that release heat as they disintegrate into more stable forms

21. Earth’s Heat
Since its original heating, Earth has been slowly losing heat
Amount of heat loss varies from place to place
Some rocks lose heat more quickly than others
The thickness of the crustal rock varies from place to place
The percentage of radioactive materials in rocks varies

22. Underground caves maintain constant temperature all year
Below 70 meters ground temperatures begin to heat up
~ 1oC for every 40 meters in depth

23. Describe three sources of Earth’s internal heat
Describe three sources of Earth’s internal heat. Which internal process is still producing heat?

24. Earth’s Magnetic Field
Magnetic north is different from geographic north
Magnetic north is 11o away from the poles.

25. Earth’s Magnetic Field
Scientist hypothesize that the magnetic field is the result of the movement of fluid in the outer core
An electric current is generated when liquid iron moves across an already existing magnetic field.
These two fields create Earth’s strong magnetic field

26. 4.2 Earth’s Rotation

27. Earth’s Rotation Rotation: the spinning of Earth around it axis
Earth completes one full rotation every 24 hours

28. Evidence for Rotation Foucault Pendulum Built pendulum 20 stories high
Once a pendulum is in motion, its direction of swing will not change

29. Foucault's Pendulum Shifted 11o each hour in a clockwise direction
After 8 hours it was swinging at a right angle to its starting direction

30. Foucault's Pendulum Shifted 11o each hour in a clockwise direction
After 8 hours it was swinging at a right angle to its starting direction
The pendulum could not have changed its direction of swing, therefore the Earth was turning beneath it

31. More Evidence of Earth’s Rotation
If Earth did not rotate, winds would blow along straight paths from areas of high pressure to areas of low pressure.

32. Wind:
Northern Hemisphere – deflected to the right
Southern Hemisphere – deflected to the left

33. Axis and Rate of Rotation
Earth rotates as it travels around the sun
Earth’s axis of rotation is an imaginary straight line from the North to South pole

34. Axis and Rate of Rotation
Earth’s axis is not perpendicular to its orbital plane
It is tilted 23.5o

35. The axis points towards Polaris, the North Star

36. Earth rotates 360o every 24 hours
Speed of rotation varies from point to point
Equator = 1690 kilometers/hour
Northern USA = ~ 1300 kilometers/hour
Poles = almost 0 kilometers/hour

37. Effects of Rotation
Only half of Earth receives sunlight at any given time
If Earth did not rotate, the half facing the Sun would have constant light, while the other half would be dark

38. Measuring Time
For centuries, people figured the time of day by the Sun’s position in the sky

39. Measuring Time
For centuries, people figured the time of day by the Sun’s position in the sky
Sun rises on the eastern horizon, moves across the sky, and sets below the western horizon

40. Measuring Time
For centuries, people figured the time of day by the Sun’s position in the sky
Sun rises on the eastern horizon, moves across the sky, and sets below the western horizon
Solar noon occurs when the sun is at the highest point on this arc

41. Measuring Time Solar noon does not occur at the same time everywhere.
Moves westward at a rate of 15o each hour or 1o every four minutes.
Led to the creation of Time Zones

42. Standard Time Zones
There are 24 worldwide time zones, each 15o of longitude wide
Division lines are called time meridians

43. International Date Line
The 180o longitude - where the date changes

44. 4.3 Earth’s Revolution

45. Earth’s Revolution
Revolution: the movement of earth in its orbit around the sun

46. Evidence of Revolution
Constellations (groups of stars) are visible on every clear night
Their position in the sky appears to change as Earth rotates and revolves

47. Evidence for Revolution
Parallax: As Earth moves in its orbit nearby stars appear to shift in position.

48. Evidence for Revolution
The stars are not actually moving
Instead Earth is actually changing positions

49. Path and Rate of Revolution
The direction of Earth’s Revolution and Rotation are the same = Counterclockwise

50. Earth’s orbit is an ellipse Perihelion – near the sun
occurs around January 2
Aphelion – away from the sun
occurs around July 4

51. Effects of Revolution and Tilt
Creates the seasons & variations in the length of days and nights
Hemisphere tilted towards the sun receives more direct sunlight = summer
Hemisphere tilted away from the sun receives less direct sunlight = winter

52. Summer Solstice
Northern Hemisphere is at its maximum tilt towards the sun
Longest day of the year
First day of summer, ~ June 21

53. Tropic of Cancer 23.5o N = direct sunlight
Arctic Circle 66.5o N= 24 hours of daylight
Antarctic Circle 66.5o S= 24 hours of darkness

54. Winter Solstice
Northern Hemisphere is at its maximum tilt away from the sun
Shortest day of the year
First day of winter, ~ December 21

55. Equinox Midway between the two solstices
Neither hemisphere tilts towards the sun
Daytime and nighttime are equal all over the world

56. Vernal Equinox = ~ March 21
Autumnal Equinox = ~ September 22