1. Ch 18 Trefil & Hazen The Sciences
Cycles of the Earth
Ch 18 Trefil & Hazen
The Sciences

2. All Matter above and beneath the Earth’s surface moves in cycles.

3. What drives the earth cycles?
Sun radiates heat down on the ocean of air and water
Earth’s hot core or geothermal energy spreads upward

4. Demo and describe the water cycle

5. Oceans contain 97% of Earth’s water
Water cycle constantly transfers the world’s water between three basic storage reservoirs.
Oceans contain 97% of Earth’s water
Of the 3% of the Earth’s freshwater:
2.15% is locked away in glaciers and ice sheets
0.62% is groundwater, stored as soil moisture
0.009% is in rivers and lakes
0.001% is in the atmosphere

6. Amazingly, the whole shebang of water in lakes & rivers, water in rain & snow, water in our bathtub, shower, and drink bottles, amounts to only about 1% of the water in the world.

8. The Water (Hydrologic) Cycle
p. 442
Ocean to Atmosphere
84% vapor from oceans; 16% from continents
Atmosphere to Surface
Vapor cools, condenses & precipitates out in a week, or few hours or few centuries; depends.
77% precipitation falls on the oceans
Surface to Ocean
23% of precipitation in water cycle meets our needs via “surface water” and “ground water.”

9. Major steps in the water cycle:
Ocean to Atmosphere
Atmosphere to Surface
Surface to Ocean

10. How do the different types of precipitation form?
Rain--Vapor condenses around aerosols and falls from sky.

11. How do the different types of precipitation form?
Snow—ice crystals that assemble themselves as they fall through a cloud

12. How do the different types of precipitation form?
Hail--large frozen rain formed in a giant cloud of an intense thunderstorm.

13. How do the different types of precipitation form?
Sleet--falling snow may partially melt and then refreeze into a frozen raindrop.

14. Motion of the Ocean

15. Discuss the cause/effect dynamics of global ocean currents. link

16. Here’s a new perspective:

17. Explaining ocean motion: p. 441
Great currents move the ocean, distributing heat and regulating climate across Earth.
General scheme
Warm equatorial water swirls pole-ward and circulates in vast ocean areas.
Cool water moves around the poles and flows toward equator as continents allow passage.

20. Atmospheric Convection on the Rotating Earth p. 452
Trade Winds: easterlies at equator
In the tropics, winds prevail from E to W.
Air warmed new equator travels pole-ward but gradually cools and sinks. Earth’s rotation deflects surface winds

21. Atmospheric Convection on the Rotating Earth p. 452
Polar Easterlies:
In the polar regions, cold dense air sinks and moves away from poles.
Earth’s rotation deflects surface wind from East to West.

22. Atmospheric Convection on the Rotating Earth p. 452
Westerlies
Near 30o N & S latitude, Earth’s rotation moves air from West to East, as warm air moves to poles.

23. Many ongoing processes constantly change Earth.

24. How do “rocks” “cycle” ?

25. Rock Cycle

26. Rocks
Igneous = formed by the cooling and crystallization of magma (melted rock)
Sedimentary = formed from accumulation of weathered material (sediments)
Metamorphic = formed from preexisting rocks that have been transformed (changed)

27. Igneous, Sedimentary, Metamorphic
ü    Each type of rock records a different complex past.
ü    Each type of rock can be changed from one form to another and back again.
 geologists call these transformations the “rock cycle”

28. Ch 18 pp
Try Discussion Questions 1-7,
And visit links on pacing guide:
Hydrologic cycle
Atmospheric cycle
Rock cycle