1. Shape of Earth

2. 1. Models are used to represent objects.
Physical – show us visually (globes)
Mechanical – show how it works (stream table, car engine)
Mathematical – equations show relationships ( density formula)
Graphic – show a ‘picture’ of relationships when no simple equation exists

3. 2. EVIDENCE EARTH IS ROUND
Sinking ships

4. Ships appear to ‘sink’ in the horizon

5. You line of sight cannot follow the curve of Earth

7. Changing position of Sun and stars as we move across earth’s surface

8. Polaris – North star. Part of an asterism – Little Dipper Find Polaris using the Big Dipper and the pointer stars Can only be seen in the Northern Hemisphere

9. The Big Dipper moves around Polaris
The Big Dipper moves around Polaris. One complete circle around Polaris every 24 hours.

10. Are these observers at the same location??

11. The Altitude of Polaris = the Latitude of the Observer
Equator
To Polaris
To Polaris
Zenith of the Observer LO
LO = Latitude of the Observer AP
AP = Altitude of Polaris X O
AP = 90 - X
= LO
Observer’s Horizon
The Altitude of Polaris = the Latitude of the Observer
00 at Equator, in Buffalo, at North Pole

13. Astrolabe

14. Lunar eclipses show Earth’s curved shadow crossing the moon.

15. Gravity – depends on masses and distance
Gravity – depends on masses and distance. Gravity is pretty much the same all over earth

16. Trees – tops are the last part to go dark

18. Photos from space

19. Earth is NOT perfectly round
Oblate spheroid – bulges at the equator because it is a rotating sphere.
Polaris – altitude does NOT correlate Exactly with the change in latitude – but is very, very close.
Gravity depends on the masses
and the distance between them.

20. Gravity – depends on masses and distance
Gravity – depends on masses and distance. Gravity is pretty much the same all over earth – but not exactly the same.

21. Gravity does NOT pull evenly everywhere on Earth

22. Look in ESRT for earth’ diameter

23. A globe is an ACCURATE model of Earth’s shape
Earth is very, very round and very, very, smooth.
Even Mt. Everest is not big enough to earn a ‘bump’ on a globe!

24. Evidence for a round earth:
1. 'sinking ships‘-only appear to sink
2. Altitude of Polaris (and other stars) change as your latitude changes.
3. lunar eclipses
4. gravity is nearly the same everywhere on earth
5. pictures from space
Evidence for an oblate spheroid:
1. Altitude of Polaris does not change EXACTLY with your change in latitude
2. Gravity is SLIGHTLY greater at the Poles than at the equator.

25. Layers of earth

26. Interior layers of Earth
Deepest ‘hole’ is only a few km in depth.
Much of what we ‘know’ are inferences – based on fact
Layers are ‘ordered’ because of density differences
Data has been gathered through EQ and Volcanic activity and meteor samples

28. Lithosphere:

29. LITHOSPHERE – rock layer
– the solid, brittle rock that forms a continuous shell around earth (yes, even under the ocean) and covers a more ‘plastic’ interior.
Often covered with a layer of soil or loose rock material (WHY?)
Thickest under the mts (100 km), Thinnest under oceans (`15 km)
Continental crust less dense, Basaltic crust more dense
Upper portion of lithosphere is called the CRUST and contain rocks that are less dense.
Bottom portion is the rigid mantle and creates an interface with the fluid like asthenosphere
May see OUTCROPS of crust/ lithosphere ( NF gorge)
Composition : see ESRT
Oxygen – 46% by mass
Silicon 28% others: Al, Fe, Ca, Na, Mg, K,

30. Find the chart in your ESRT

31. Asthenosphere
Upper portion of mantle (but not top most part – that’s the rigid mantle & is part of the lithosphere)
“fluid like” or ‘plastic like’ layer
Heat and pressure cause the rocks to be very soft. ( think play dough or warm chocolate)
Convection currents flow here

32. Convection currents in the mantle

33. Outer core –believed to be liquid – under high temps and pressure the rocks melt.

34. Inner core – solid - very high temps and pressure.
Both cores believed to have high amounts of Ni and Fe, based on meteor evidence

36. Be careful when reading this chart!!

37. Hydrosphere: water layer - VERY THINNNNNNNN!!
ABOUT 3-5 KM THICK IN THE OCEANS
Includes all water on earth – lakes, glaciers, oceans, underground and atmosphere
About 71% of earth’s surface is covered with water
Consists of H (66%0 and O (33%) and others
Play roles in many processes – transport, erosion, weathering, chem.,.rxn, maintaining heat balance, weather,….

40. Cryosphere – ice or frozen layer – glaciers, ice caps
Biosphere – living layer

41. ATMOSPHERE - Thin shell of gases bound to earth by gravity
Extends several 100’s km into space

42. Most of the mass is within 5 km of earth’s surface
Most of the mass is within 5 km of earth’s surface. Gas molecules are held close to the surface by gravity.

43. Composition: 78% N2 21% O2. others (CO2, Ar, CH4, O3,)
Composition: 78% N2 21% O2 others (CO2, Ar, CH4, O3,) (where can you find this info?? Also dust, ash, pollen, ice, water vapor…

44. Divided into layers based on temperature changes

45. Troposphere – first 11 km
contains most of the mass – greatest air pressure
Most of the water is in this layer
Most of weather takes place here
Temp. decreases as altitude increases

46. Stratosphere – temperature increases as altitude increases
Ozone absorbs ultra violet energy

47. Most of the sun’s energy that reaches earth’s surface is in the form of UV, visible light or infrared radiation.

48. Energies able to reach earth’s surface – and those that do not.

49. Mesosphere – middle layer
Thermosphere – gases and charged particles found here (not many atoms)
Ionosphere is in this layer
Temps get very high
‘Pauses’ – interface between layers