Chapter Menu

1. Chapter Introduction Lesson 1 Earth’s Atmosphere Lesson 2 Energy Transfer in the Atmosphere Chapter Menu

2. How does Earth’s atmosphere affect life on Earth? Chapter Introduction

3. Earth’s Atmosphere • How did Earth’s atmosphere form? • What is Earth’s atmosphere made of? • What are the layers of the atmosphere? • How do air pressure and temperature change as altitude increases? Lesson 1 Reading Guide - KC

4. Earth’s Atmosphere • atmosphere • water vapor • troposphere • stratosphere • ozone layer • ionosphere Lesson 1 Reading Guide - Vocab

5. Importance of Earth’s Atmosphere • The atmosphere is a thin layer of gases surrounding Earth. • The atmosphere contains the oxygen and water necessary for life on Earth. • The atmosphere provides insulationand helps keep temperatures on Earth within a range in which living organisms can survive. Lesson 1-1

6. Importance of Earth’s Atmosphere(cont.) The atmosphere helps protect living organisms from some of the Sun’s harmful rays and meteorites. atmosphere from Greek atmos, means “vapor”; and Latin sphaera,means “sphere” Lesson 1-1

7. Origins of Earth’s Atmosphere • Erupting volcanoes emitting hot gases from ancient Earth’s interior surrounded the planet to form an atmosphere. • Ancient Earth’s atmosphere was thought to be water vapor with a little carbon dioxide and nitrogen, but not enough oxygen to support life. • Water vapor is water in gaseous form. Lesson 1-2

8. Origins of Earth’s Atmosphere(cont.) • As Earth and its atmosphere cooled, the water vapor condensed into liquid, rain fell, and then evaporated from Earth’s surface for thousands of years. • Eventually water began to accumulate on Earth’s surface, forming oceans. • Carbon dioxide from the atmosphere dissolved in rainwater and fell into the oceans. Lesson 1-2

9. Origins of Earth’s Atmosphere(cont.) • Earth’s first organisms could undergo photosynthesis, and produced the oxygen in today's atmosphere. • The organisms removed CO2 from the atmosphere and released oxygen into it. • Eventually the levels of CO2 and oxygen supported the development of other organisms. Lesson 1-2

10. Composition of the Atmosphere • Today’s atmosphere is mostly made up of invisible gases, including nitrogen, oxygen, and carbon dioxide. • About 78 percent of the atmosphere is nitrogen, and about 21 percent is oxygen. • The amounts of atmospheric gases, which include water vapor, carbon dioxide, and ozone vary. Lesson 1-3

11. Acids in the air are formed when sulfur dioxide and nitrous oxide combine with water vapor. PhotoLink/Getty Images Lesson 1-3

12. Composition of the Atmosphere(cont.) • Many tiny solid particles, such as pollen, dust, and salt, can enter the atmosphere through natural processes. • Solid particles of ash from volcanic eruptions and exhaust soot from cars are also present in the atmosphere. Lesson 1-3

13. One way solid particles enter the atmosphere is from volcanic eruptions. C. Sherburne/PhotoLink/Getty Images Lesson 1-3

14. Composition of the Atmosphere(cont.) • The most common liquid particles in the atmosphere are water droplets. • Though microscopic in size, water particles are visible when they form clouds. • Other atmospheric liquids include acids that result when volcanoes erupt and fossil fuels are burned. Lesson 1-3

15. Layers of the Atmosphere The atmosphere has several different layers, each with its own unique properties. Lesson 1-4

16. Layers of the Atmosphere(cont.) • The atmospheric layer closest to Earth’s surface is called the troposphere. • The troposphere extends from Earth’s surface to altitudes between 8-15 km. • The temperature of the troposphere decreases as you move away from Earth. Lesson 1-4

17. Layers of the Atmosphere(cont.) • Sunlight passes through the atmosphere and warms Earth’s surface, making this the warmest part of the troposphere. • The warmth is radiated to the troposphere, causing weather. • The stratosphere is the atmospheric layer directly above the troposphere. Lesson 1-4

18. Layers of the Atmosphere(cont.) • The stratosphere extends from about 15 km to about 50 km above Earth’s surface. • The area of the stratosphere with a high concentration of ozone is referred to as the ozone layer. • The presence of the ozone layer causes the stratospheric temperatures to increase with altitude. Lesson 1-4

19. Layers of the Atmosphere(cont.) • Ozone has three oxygen atoms and absorbs the Sun’s ultraviolet rays more effectively than oxygen. • Ozone protects Earth from ultraviolet rays that can kill plants, animals, and other organisms and cause skin cancer in humans. Lesson 1-4

20. Layers of the Atmosphere(cont.) • Combined, the mesosphere and thermosphere are much thicker than the troposphere and the stratosphere, yet only 1 percent of the atmosphere’s gas molecules are found in the mesosphere and thermosphere (they have a low density of gases). • Most meteors burn up in the mesosphere and thermosphere instead of striking Earth. Lesson 1-4

21. The ionosphere is a region within the mesosphere and thermosphere containing ions. • The ionosphere’s ions reflect AM radio waves transmitted at ground level. Lesson 1-4

22. Auroras occur in the ionosphere when ions from the Sun strike air molecules, causing them to emit vivid colors of light. Per Breiehagen/Getty Images Lesson 1-4

23. Layers of the Atmosphere(cont.) • The exosphere is the atmospheric layer farthest from Earth’s surface where pressure and density are so low that individual gas molecules rarely strike one another. • The molecules move at incredibly fast speeds after absorbing the Sun’s radiation and can escape the pull of gravity and travel into space. Lesson 1-4

24. Air Pressure and Altitude • Gravity pulls the atmosphere toward Earth, creating air pressure. • At lower altitudes (closer to earth surface), the air is denser and air pressure is greatest. • At higher altitudes, the air is less dense and air pressure is lower. Lesson 1-5

25. Temperature and Altitude • Temperature changes in different ways as altitude increases in the different layers of the atmosphere. • In the troposphere, temperature decreases as altitude increases. • In the stratosphere, temperature increases as altitude increases because of the high concentration of ozone. Lesson 1-6

26. Temperature and Altitude(cont.) • In the mesosphere, as altitude increases, temperature again decreases. • In the thermosphere and exosphere the opposite happens: temperatures increase as altitude increases. Lesson 1-6

27. Lesson 1-6

28. Energy Transfer in the Atmosphere • How does energy transfer from the Sun to Earth and the atmosphere? • How are air circulation patterns within the atmosphere created? Lesson 2 Reading Guide - KC

29. Energy Transfer in the Atmosphere • radiation • conduction • convection • stability • temperature inversion Lesson 2 Reading Guide - Vocab

30. Energy from the Sun • Radiation is the transfer of energy by electromagnetic waves. • Ninety-nine percent of the radiation from the Sun consists of visible light, ultraviolet light, and infrared radiation. • The majority of sunlight is visible light that passes through the atmosphere to Earth’s surface, where it is converted to heat. Lesson 2-1

31. Energy from the Sun(cont.) • The wavelengths of ultraviolet (UV) light and infrared radiation (IR) are just beyond the range of visibility to human eyes. • UV light is harmful to human skin and IR can be sensed as thermal energy or warmth. • As energy from the Sun is absorbed by Earth, it is radiated back as IR. Lesson 2-1

32. Energy on Earth(cont.) • Gases and particles in the atmosphere absorb about 20 percent of incoming solar radiation. • Oxygen, ozone, and water vapor all absorb incoming ultraviolet light. • Water and carbon dioxide in the troposphere absorb some infrared radiation from the Sun. Lesson 2-2

33. Energy on Earth(cont.) • Earth's atmosphere and the surface of Earth reflect about 30 percent of the sun's radiation that comes toward Earth. • Bright surfaces, especially clouds, reflect incoming radiation, and some is reflected at Earth’s surface. • Earth’s surface only receives and absorbs about 50 percent of incoming solar radiation. Lesson 2-2

34. Radiation Balance • The amount of radiation Earth receives from the Sun is the same as the amount Earth radiates into the atmosphere. • This radiation balance maintains an overall temperature on Earth. • Land, trees, and the ocean absorb and emit infrared radiation. Lesson 2-3

35. The Greenhouse Effect • Some of the gases in the atmosphere, called greenhouse gases, act like the glass of a greenhouse, allowing sunlight to pass through but preventing some of Earth’s infrared radiationenergy from escaping. • When gases in Earth’s atmosphere direct radiation back toward Earth’s surface, this warms Earth’s atmosphere more than normal, creating a heat surplus. Lesson 2-4

36. The Greenhouse Effect (cont.) The gases that trap IR best are water vapor, carbon dioxide, and methane. Lesson 2-4

37. Thermal Energy Transfer • Conduction occurs when the atmosphere touches Earth. • Thermal energy always moves from objects with high temperature to objects with lower temperature. • Conduction is the transfer of thermal energy by collisions between particles of matter. Lesson 2-5

38. Energy is transferred through conduction, convection, and radiation. Lesson 2-5

39. Thermal Energy Transfer (cont.) • As molecules of air close to Earth’s surface are heated by conduction, they spread apart, becoming less dense. • The transfer of thermal energy by the movement of matter from one place to another is called convection. • Less dense air rises, transferring thermal energy to higher altitudes. Lesson 2-5

40. Thermal Energy Transfer (cont.) • Latent heat is exchanged when water changes from one phase to another. • Water is the only substance that can exist as a solid, a liquid, and a gas at the temperature ranges on Earth. • Latent heat energy is transferred from Earth’s surface to the atmosphere. Lesson 2-5

41. Water releases or absorbs heat energy during phase changes. Lesson 2-5

42. Circulating Air • Air is constantly moving and circulating. • On a hot day, air that is heated becomes less dense, creating a pressure difference. • Warm air is pushed upward and cool air sinks to fill in the empty space left by the warm air. • Circulating air affects weather and climate around the world. Lesson 2-6

43. Circulating Air(cont.) • Stability describes whether circulating air motions will be strong or weak. • When air is unstable, circulating motions are strong, and during stable conditions, circulating motions are weak. • During unstable conditions, ground-level air is much warmer than higher-altitude air. Lesson 2-6

44. Circulating Air(cont.) • As warm air rises rapidly in the atmosphere, it cools to form large, tall clouds. • Latent heat, released as water vapor, changes from a gas to a liquid, adds to the instability, and produces a thunderstorm. • A temperature inversion occurs in the troposphere when temperature increases as altitude increases. Lesson 2-6

45. Circulating Air(cont.) • During a temperature inversion, a layer of cooler air is trapped by a layer of warmer air above it. • This can prevent air from mixing an can trap pollution close to Earth's surface. Lesson 2-6