CHAPTER 24: THE OCEANS, ATMOSPHERE, AND CLIMATIC EFFECTS

1. . CHAPTER 24: THE OCEANS, ATMOSPHERE, AND CLIMATIC EFFECTS

2. Final Exam • Sect. S, TUESDAY DEC, 4 • 7:15 - 9:15 P.M. • I.C Room 421

3. This lecture will help you understand: • Earth’s Atmosphere and Oceans • Components of Earth’s Oceans • Ocean Waves, Tides, and Shorelines • Components of Earth’s Atmosphere • Solar Energy • Driving Forces of Air Motion • Global Circulation Patterns

4. Earth’s Atmosphere and Oceans Earth is 71% covered by water. Water’s high specific heat capacity accounts for moderate temperatures in coastal lands.

5. Earth’s Atmosphere and Oceans Earth’s early atmosphere appeared before the Sun was fully formed. • Hydrogen • Helium Sun’s formation swept away Earth’s original atmosphere and a new atmosphere formed.

6. Earth’s Atmosphere and Oceans Earth’s atmosphere developed in stages: • Hot gases escaped through volcanoes and fissures. • Free oxygen occurred as a result of photosynthesis by cyanobacteria. • Ozone began to accumulate in the upper atmosphere. • Water vapor condensed to form oceans.

7. Components of Earth’s Oceans Ocean floor encompasses continental margins and deep ocean basins. Continental margins are between shorelines and deep ocean basins. • Continental shelf—shallow, underwater extension of the continent. • Continental slope—marks boundary between continental and oceanic crust. • Continental rise—wedge of accumulated sediment at base of continental slope.

8. Components of Earth’s Oceans The ocean bottom is etched with deep canyons, trenches, and crevasses. Underwater mountains rise upward from the seafloor. The deep-ocean basin: • Basalt from seafloor spreading plus thick accumulations of sediment • Abyssal plains, ocean trenches, and seamounts

9. Components of Earth’s Oceans The deep-ocean basin: • Abyssal plains—flattest part of the ocean floor due to accumulated sediment • Ocean trenches—long, deep, steep troughs at subduction zones • Seamounts—elevated seafloor from volcanism Mid-ocean ridges: • Sites of seafloor spreading (volcanic and tectonic activity) • A global mid-ocean ridge system winds all around the Earth

10. Components of Earth’s Oceans The deepest parts of the ocean are at the ocean trenches near some of the continents. The shallowest waters are in the middle of the oceans around underwater mountains (mid-ocean ridge system).

11. Components of Earth’s Oceans CHECK YOUR NEIGHBOR Ocean trenches are the deepest parts of the ocean floor because • that is where oceanic crust meets continental crust. • that is where subduction occurs. • no sediment accumulates in trenches. • all accumulated sediment settles in the abyssal plain.

12. Components of Earth’s Oceans CHECK YOUR ANSWER Ocean trenches are the deepest parts of the ocean floor because • that is where oceanic crust meets continental crust. • that is where subduction occurs. • no sediment accumulates in trenches. • all accumulated sediment settles in the abyssal plain.

13. Ocean Waves, Tides, and Shorelines Characteristics of waves—waves get their energy from the wind. • The crest is the peak of the wave. • The trough is the low area between waves. • Wave height is the distance between a trough and a crest. • Wavelength is the horizontal distance between crests. • Wave period is the time interval between the passage of two successive crests.

14. Ocean Waves, Tides, and Shorelines Height, length, and period of a wave depend on: • Wind speed • Length of time wind has blown • Fetch—the distance that the wind has traveled across open water

15. Ocean Waves, Tides, and Shorelines Waves on the ocean surface are orbital waves. Wave energy moves forward: the disturbance moves, not the water. Occurs in the open sea in deep water.

16. Ocean Waves, Tides, and Shorelines Waves at the shoreline: • Shallow water; depth about one-half wavelength—wave begins to “feel bottom” • Wave grows higher as it slows and wavelength shortens • Steep wave front collapses, wave breaks • Turbulent water goes up the shore and forms surf

17. Ocean Waves, Tides, and Shorelines CHECK YOUR NEIGHBOR When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular motion, • decreasing its speed, and increasing distance between waves and wave height. • increasing its speed and distance between waves, and decreasing wave period. • decreasing its speed and distance between waves, causing wave height to increase. • increasing its speed and distance between waves, causing wave height to increase.

18. Ocean Waves, Tides, and Shorelines CHECK YOUR ANSWER When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular motion, • decreasing its speed, and increasing distance between waves and wave height. • increasing its speed and distance between waves, and decreasing wave period. • decreasing its speed and distance between waves, causing wave height to increase. • increasing its speed and distance between waves, causing wave height to increase.

19. Ocean Waves, Tides, and Shorelines Surf forms erosional features: • Beach • Spit • Barrier islands • Lagoons

20. Ocean Waves, Tides, and Shorelines Coral reefs are composed of actively growing coral organisms. Organisms secrete calcium carbonate as they grow—that is what we see. Many reefs survive on photosynthetic algae. Coral bleaching is an indicator of global warming.

21. Ocean Waves, Tides, and Shorelines Tides occur because of the differences in the gravitational pull exerted by the Moon on opposite sides of Earth.

22. Ocean Waves, Tides, and Shorelines Because Earth spins on its axis once a day, it should have two distinct tides 12 hours apart. But because the Moon moves around Earth, the times of the tides vary each day.

23. Ocean Waves, Tides, and Shorelines Alignment of the Sun, Earth, and Moon causes spring tides—more dramatic highs and lows.

24. Ocean Waves, Tides, and Shorelines When the pull of the Sun and Moon are perpendicular to each other, we get neap tides—lower highs and higher lows.

25. Components of Atmosphere

26. Components of Earth’s Atmosphere Earth’s atmosphere is divided into layers, each with different characteristics: • Troposphere • Stratosphere • Mesosphere • Thermosphere • Ionosphere • Exosphere

27. Components of Earth’s Atmosphere Troposphere: • Lowest and thinnest layer • 16 km at equator, 8 km at poles • 90% of the atmosphere’s mass • Where weather occurs • water vapor and clouds • Temperature decreases with altitude • 6°C per kilometer • Top of troposphere averages –50°C

28. Components of Earth’s Atmosphere Stratosphere: • Top of troposphere to 50 km above surface • Ozone layer • Absorbs harmful UV radiation • Temperature increases because of ozone absorption of UV radiation. • Ranges from –50°C at base to 0°C at top

29. Components of Earth’s Atmosphere Mesosphere: • Extends from stratosphere to altitude of 80 km • Temperature decreases with altitude • Gases in this layer absorb very little UV radiation. • 0°C at bottom to –90°C at top

30. Components of Earth’s Atmosphere Thermosphere: • Temperature increases with altitude • Temperature is related to average speed of gas molecules—very high speed gives high temperatures • Temperatures up to 1500°C • Very low density of gas molecules means very little heat absorption—it would feel cold.

31. Components of Earth’s Atmosphere Ionosphere: • Electrified region within the thermosphere and upper mesosphere • Auroras—fiery displays of light near Earth’s magnetic poles Exosphere: • The interface between Earth and space • Beyond 500 km, atoms and molecules can escape to space

32. Components of Earth’s Atmosphere The average temperature of Earth’s atmosphere varies in a zig-zag pattern with altitude.

33. Solar Energy Solar radiation is electromagnetic energy emitted by the Sun. • Visible, short-wavelength radiation Terrestrial radiation is reemitted solar radiation from Earth’s surface. • Infrared, longer-wavelength radiation

34. Solar Energy The Sun warms Earth’s ground, and the ground, in turn, warms Earth’s atmosphere. • Earth’s temperature varies according to the degree of solar intensity—the amount of solar radiation per area. • Where solar intensity is higher, temperatures are higher.

35. Solar Energy Solar intensity is highest where the Sun’s rays strike Earth’s surface straight on. • Flashlight beam at 90° angle to the surface • Equatorial regions Solar intensity is weaker where the Sun’s rays strike Earth’s surface at an angle. • Flashlight beam at an angle • Higher latitudes

36. Solar Energy Variation in solar intensity with latitude and the tilt of the Earth’s axis helps to explain the different seasons.

37. Solar Energy When the Sun’s rays are closest to perpendicular at any spot on the Earth, that region’s season is summer. Six months later, as the rays fall upon the same region more obliquely, the season is winter. In between are the seasons fall and spring.

38. Solar Energy: Global Warming Human activities pump greenhouse gases into the atmosphere: carbon dioxide, methane, nitrous oxide, ozone, CFCs. The result is a warming Earth.

39. Driving Forces of Air Motion Atmospheric pressure = force the atmosphere exerts on an area of surface. • Force = weight of air molecules above that surface. • At any level in the atmosphere, force = total weight of air above that level. • At higher elevations, fewer air molecules above—atmospheric pressure is less.

40. Driving Forces of Air Motion CHECK YOUR NEIGHBOR Atmospheric pressure is greatest near the Earth’s surface because of the weight of all the air above. 90% of Earth’s atmosphere is in the troposphere. of warmer temperatures. of water vapor.

41. Driving Forces of Air Motion CHECK YOUR ANSWER Atmospheric pressure is greatest near the Earth’s surface because of the weight of all the air above. 90% of Earth’s atmosphere is in the troposphere. of warmer temperatures. of water vapor.

42. Driving Forces of Air Motion CHECK YOUR NEIGHBOR What drives air from areas of high pressure to areas of low pressure? Convection currents. Wind. The pressure-gradient force. Water vapor.

43. Driving Forces of Air Motion CHECK YOUR ANSWER What drives air from areas of high pressure to areas of low pressure? Convection currents. Wind. The pressure-gradient force. Water vapor.

44. Driving Forces of Air Motion Wind is air that flows horizontally from higher pressure to lower pressure. The greater the pressure gradient, the stronger the wind.

45. Driving Forces of Air Motion Pressure differences are caused by uneven heating of the Earth’s surface. • Local differences in heating contribute to small-scale local winds. • Planet-scale differences occur because of solar intensity variations—equatorial regions have greater solar intensity than polar regions. • Differences contribute to global wind patterns—prevailing winds.

46. Driving Forces of Air Motion Warm air characteristics: • Warm air expands • Warm air has lower density and lower pressure Cool air characteristics: • Cool air contracts • Cool air has higher density and higher pressure

47. Driving Forces of Air Motion Local winds: • Not all surfaces are heated equally. • Example: Land heats and cools more rapidly than water. • Unequal heating results in pressure differences. And pressure differences result in wind. Remember: Wind is air that flows horizontally from higher pressure to lower pressure.

48. Driving Forces of Air Motion CHECK YOUR NEIGHBOR More energy is required to raise the temperature of water than that of land. Once heated, water will retain the heat longer than land. This concept is related to expansion of warm air. pressure differences of land and water. water’s high specific heat capacity. expansion of seawater.

49. Driving Forces of Air Motion CHECK YOUR ANSWER More energy is required to raise the temperature of water than that of land. Once heated, water will retain the heat longer than land. This concept is related to expansion of warm air. pressure differences of land and water. water’s high specific heat capacity. expansion of seawater.

50. Driving Forces of Air Motion CHECK YOUR NEIGHBOR At a hypothetical school yard there is a blacktop area and a grassy area. On a particularly warm day, a small breeze develops. Air moves from the grassy area to the blacktop. the blacktop to the grassy area. low pressure to high pressure. Not enough information.