1. Topic II
Measuring Earth

2. I. The Shape of Earth
A. Oblate Spheroid: earth is flattened at the poles and bulges at the equator.
*the equatorial diameter is greater than the polar diameter.

3. B. Evidence of Earth’s Shape
1. Photos from space: reveal that Earth is almost a perfect sphere.
2. Ships over the horizon: the gradual appearance or disappearance of a ship over the curved surface of Earth.

4. 3. Lunar Eclipses: the curved shadow of Earth on the moon’s surface during a lunar eclipse.

5. 4. Measurement of Gravity: the pull of gravity is greater at the poles than the equator.
a. The poles are closer to Earth’s center generating a greater pull of gravity.

6. 5. The altitude of Polaris (North Star): the altitude of Polaris above the horizon changes as an observer moves north or south in the Northern Hemisphere.
a. As you travel north the altitude of Polaris increases.
*the altitude of Polaris equals the Northern latitude of the observer.

7. b. Locating Polaris

8. II. Latitude and Longitude
A. Latitude: angular distance measuring from the equator (0 degrees) to the north or south poles (90 degrees)
1. Parallels: lines of latitude that run east to west parallel to the equator.

9. B. Longitude: angular distance measuring east or west of the Prime Meridian.
1. Meridians: lines that run north /south from pole to pole.
a. Prime Meridian: 0 degrees long.
b. International Date Line: 180 degrees long. Maximum long.

10. 1. Earth’s rotational speed: # of degrees in Earth 360 degrees
C. Time Zones: There are 24 time zones on Earth at an approx. width of 15 degrees each.
1. Earth’s rotational speed:
# of degrees in Earth 360 degrees
Time of one rotation 24 hours
Answer: =

11. 2. The four time zones in the United States

12. 3. Crossing the International Date Line:
a. You will gain a day if you cross it heading West and lose a day when heading East.
Ex. If it’s Wed. and you cross the IDL heading west, it would then be Thursday.

13. III. Fields: a region of space/area that has a measurable value of a given property at every point.
A. Isolines: lines on a field map connecting points of equal value.
Ex. Isotherms connect points of equal temp.

14. B. Topographic Maps: show the change in elevation of the land.
1. Contour Line: isolines connecting points of equal elevation.
2. Contour Interval: difference in elevation between two consecutive contour lines.

15. 3. Index Contour Line: a bolded line indicating the elevation of that line.
4. Benchmark: a monument giving the exact elevation above sea level of that spot.

18. 5. Depression Contour: Indicated by hachure marks, shows a decrease in elevation.
* The value of the first depression line is equal to the line before it.

19. What direction is the stream flowing?
6. River Valleys: (the law of V’s) contour lines bend upstream where they cross a river. The V’s point uphill.
What direction is the stream flowing?

20. 7. Topographic Profile: a side view (elevation) of a given area.
Map view
Profile view

21. 8. Gradient: The rate at which elevation changes from place to place
8. Gradient: The rate at which elevation changes from place to place. The closer the lines, the steeper the slope.
a. Gradient: change in field value
distance

22. Calculate the gradient between points A and B
Distance from A to B is 25 km, elevation is in meters.

23. IV. Parts of Earth
A. Atmosphere: the gases that surround earth
B. Hydrosphere: the waters of Earth (oceans, seas, lakes)
C. Lithosphere: the outer shell of Earth composed of rock.

24. Composotion of Earth

25. Earth’s Atmosphere