1. Topic II: Measuring the Earth
Regents Earth Science
Topic II:
Measuring the Earth

2. Is the Earth Round?
Not exactly………so Columbus wasn’t right!

3. The Earth appears round but when “measured”, it is actually flattened at the poles and bulging at the equator…
….**making the Earth a slightly, slightly, slightly, slightly Oblate Spheroid
This is not how
It looks!!!!

4. How can we tell that the shape of Earth is nearly a sphere?
Photographs from space (#1)

5. Masts of ships appearing to “sink” as they travel past the horizon

6. Gravity Measurements (more gravitational pull at the poles—closer to center of Earth = higher weight)

7. Observations of Polaris (the North Star)

8. Spheres of the Earth:
Atmosphere: shell of gases that surround the Earth.
It is layered into zones. Each zone has a specific temperature, and composition

9. Hydrosphere: all bodies of water on Earth (oceans, lakes, rivers, ground water)—covers 70% of Earth’s surface

10. Lithosphere: solid portion of the Earth (rock and soil layer)

11. ESRT’s Cover

12. How do you locate Positions on Earth?
Coordinate System: a grid of imaginary lines that are used to locate a point on a two-dimensional surface (a map)

13. Latitude-Longitude System: the most commonly used coordinate system used for the Earth. This system is based on observations of the sun and other stars.

14. Lines of Latitude (Parallels):
Measures distance north or south of the equator (0°
90° at Poles
Parallel

15. Lines of Longitude (Meridians):
Measures distances east or west of the Prime Meridian (Prime Meridian is 0--180 is highest)
Lines connect at the north and south poles

18. How do you determine Latitude?
The angle that Polaris makes with the horizon is equal to the person’s latitude (Polaris never moves)
Altitude = Latitude

19. Polaris Facts:
Only seen in the Northern Hemisphere (not south of the Equator)
Points Due (exactly) North
NOT the brightest star in the sky!
Use Pointer Stars to Find
Directly above North Pole
“Big Dipper”—easy to see

20. How do you determine Longitude?
Find the time difference between your local time and Greenwich Mean Time (GMT) and then multiply by 15 (Greenwich is at 0 Longitude)
This works because the Earth rotates 15 every hour and the Time Zones are 15 longitude apart (24 total, 1 hour apart)

22. World Time Zones

23. If your time is EARLIER than the time given for GMT, then you are WEST of the Prime Meridian
If your time is LATER than the time given for GMT, then you are EAST of the Prime Meridian

24. U.S. Time Zones

25. Mapping
Topographic Maps: shows the shape of Earth’s surface by using contour lines (the shape of the lines indicate the shape of the land)

27. What are Contour Lines?
lines of equal elevation (height above sea level)
**there are other lines on other types of maps as well (Isotherms: equal temperature / Isobars: equal pressure)

28. What to look for when looking at Topographic Maps:
Contour Interval: difference in height between two adjacent contour lines
Index Contour: Bold lines
with elevation values
Contour Interval = 20 ft.

29. Scale: distances on a map represent the actual distance on the ground

30. Map Direction: often indicated by some type of arrow pointing north (if there is no arrow, then north is the top of the map)

31. Benchmark: a metal marker placed in the ground that shows the exact elevation.
..on a topo map, BM X (Elevation)

32. Gradient: rate at which a field changes from place to place—also called slope or steepness
Change in Field Value
Gradient = Distance