1. ENVIRONMENTAL SCIENCE Chapter 3 The Dynamic Earth 3.2 The Atmosphere

2. 3.2 The Atmosphere Objectives Describe the composition of Earth’s atmosphere. Describe the composition of Earth’s atmosphere. Describe the layers of the Earth’s atmosphere. Describe the layers of the Earth’s atmosphere. Explain three mechanisms of heat transfer in Earth’s atmosphere. Explain three mechanisms of heat transfer in Earth’s atmosphere. Explain the greenhouse effect. Explain the greenhouse effect.

3. Introduction The atmosphere is a mixture of gases that surrounds the Earth. The atmosphere is a mixture of gases that surrounds the Earth. Earth’s atmosphere changes constantly as gases are added and removed. Earth’s atmosphere changes constantly as gases are added and removed. Cellular respiration, photosynthesis, volcanic eruptions, burning of fossil fuels, and evaporation of water are all processes that act on the atmosphere. Cellular respiration, photosynthesis, volcanic eruptions, burning of fossil fuels, and evaporation of water are all processes that act on the atmosphere. The atmosphere also insulates the Earth’s surface preventing rapid heat loss. The atmosphere also insulates the Earth’s surface preventing rapid heat loss.

4. Composition of Earth’s Atmosphere Composition of Earth’s atmosphere. Composition of Earth’s atmosphere. –Nitrogen – 78% –Oxygen – 21% –Other gases – 1% Volcanic eruptions and the decay of dead plants and animals are the primary source of atmospheric nitrogen. Volcanic eruptions and the decay of dead plants and animals are the primary source of atmospheric nitrogen. Atmospheric oxygen is primarily produced as a byproduct of photosynthesis of marine algae and green plants. Atmospheric oxygen is primarily produced as a byproduct of photosynthesis of marine algae and green plants. The remaining gases include argon, carbon dioxide, water vapor, and a few other minor constituents. The remaining gases include argon, carbon dioxide, water vapor, and a few other minor constituents.

6. Composition of Earth’s Atmosphere The atmosphere also contains small solid particles and atmospheric dust which may include soil, salt, volcanic ash, ash from fires, skin, hair, pollen, microbes, and aerosols. The atmosphere also contains small solid particles and atmospheric dust which may include soil, salt, volcanic ash, ash from fires, skin, hair, pollen, microbes, and aerosols. The pull of gravity keeps the majority of the atmosphere close to the Earth’s surface. The pull of gravity keeps the majority of the atmosphere close to the Earth’s surface. Air becomes less dense as elevation increases. Air becomes less dense as elevation increases. The vast majority of particles making up the atmosphere are below 30 km. The vast majority of particles making up the atmosphere are below 30 km.

7. Layers of the Atmosphere The atmosphere is divided into four layers based on temperature changes. The atmosphere is divided into four layers based on temperature changes. –Troposphere –Stratosphere –Mesosphere –Thermosphere See www.scilinks.org and select the topic “Layers of the Atmosphere” and enter SciLinks Code “HE4061”. See www.scilinks.org and select the topic “Layers of the Atmosphere” and enter SciLinks Code “HE4061”.www.scilinks.org

10. Layers of the Atmosphere The troposphere is the lowest layer of the atmosphere. The troposphere is the lowest layer of the atmosphere. It extends up to about 18 km above sea level. It extends up to about 18 km above sea level. Almost all of the weather occurs in the troposphere, Earth’s densest layer. Almost all of the weather occurs in the troposphere, Earth’s densest layer. Temperature decreases as altitude increases in the troposphere. Temperature decreases as altitude increases in the troposphere.

11. Layers of the Atmosphere The stratosphere, which lies just above the troposphere, extends from 18 km to about 50 km in altitude. The stratosphere, which lies just above the troposphere, extends from 18 km to about 50 km in altitude. Temperatures rise as altitude increases in the stratosphere because ozone absorbs UV (ultraviolet) energy and it warms the air. Temperatures rise as altitude increases in the stratosphere because ozone absorbs UV (ultraviolet) energy and it warms the air. The ozone, prevents much of the ultraviolet energy from reaching the Earth. The ozone, prevents much of the ultraviolet energy from reaching the Earth. UV energy is damaging to the cells of Earth’s organisms. UV energy is damaging to the cells of Earth’s organisms. The mesosphere extends from about 50 km to about 80 km. The mesosphere extends from about 50 km to about 80 km.

12. Layers of the Atmosphere The mesosphere is the coldest layer of the atmosphere – temperatures reaching as low as -93°C! The mesosphere is the coldest layer of the atmosphere – temperatures reaching as low as -93°C! The thermosphere, about 80 km to 550 km above Earth’s surface, experiences temperatures that measure above 2,000°C. The thermosphere, about 80 km to 550 km above Earth’s surface, experiences temperatures that measure above 2,000°C. Though extremely high in temperature, the thermosphere would not feel hot to us because heat is transferred as particles collide and there are very few particles in the thermosphere to collide with. Though extremely high in temperature, the thermosphere would not feel hot to us because heat is transferred as particles collide and there are very few particles in the thermosphere to collide with. Nitrogen and oxygen atoms in the lower thermosphere absorb X-rays and gamma rays giving the atoms an electrical charge. Nitrogen and oxygen atoms in the lower thermosphere absorb X-rays and gamma rays giving the atoms an electrical charge. This process creates ions, hence the name ionosphere for the lower thermosphere. This process creates ions, hence the name ionosphere for the lower thermosphere.

13. Layers of the Atmosphere Ions can sometimes radiate energy as light. Ions can sometimes radiate energy as light. Near Earth’s north (borealis) and south (australis) poles, spectacular light shows can be seen as a result of the ions. Near Earth’s north (borealis) and south (australis) poles, spectacular light shows can be seen as a result of the ions.

14. Energy in the Atmosphere There are three methods of transfer of energy from the sun. There are three methods of transfer of energy from the sun. –Conduction – the flow of heat from a warmer object to a cooler object when the objects are placed in direct physical contact –Radiation – the transfer of energy across space and the atmosphere –Convection – the flow of fluids due to a temperature difference in which the heated fluid becomes less dense and moves up as the cooler, more dense fluid sinks to fill the vacated area.

15. Energy in the Atmosphere Solar energy reaches the Earth as electromagnetic radiation. Solar energy reaches the Earth as electromagnetic radiation. The light energy from the sun includes visible light, infrared radiation, and ultraviolet radiation. The light energy from the sun includes visible light, infrared radiation, and ultraviolet radiation. Earth receives only about 2 billionths of the energy released by the sun. Earth receives only about 2 billionths of the energy released by the sun. Only about half the solar energy entering Earth’s atmosphere reaches the surface of the planet, the rest is absorbed by particles or water vapor in the sky or reflected. Only about half the solar energy entering Earth’s atmosphere reaches the surface of the planet, the rest is absorbed by particles or water vapor in the sky or reflected.

16. Energy in the Atmosphere Earth does not perpetually get hotter because the oceans and land continually radiate heat that they have absorbed back into the atmosphere. Earth does not perpetually get hotter because the oceans and land continually radiate heat that they have absorbed back into the atmosphere. Dark-colored objects become much hotter in the sun than light-colored objects because they absorb more solar energy. Dark-colored objects become much hotter in the sun than light-colored objects because they absorb more solar energy. This difference in the amount of energy absorbed gives dark objects more energy to release as heat. This difference in the amount of energy absorbed gives dark objects more energy to release as heat.

17. The Greenhouse Effect The greenhouse effect is a process in which the gases close to the Earth trap heat energy. The greenhouse effect is a process in which the gases close to the Earth trap heat energy. As light energy penetrates the Earth’s atmosphere, it strikes the surface of the Earth and begins to warm the Earth. As light energy penetrates the Earth’s atmosphere, it strikes the surface of the Earth and begins to warm the Earth. The Earth then radiates heat back into the atmosphere where some is released back into space. The Earth then radiates heat back into the atmosphere where some is released back into space. Some heat is absorbed by certain gases, called greenhouse gases, and not lost out into space. Some heat is absorbed by certain gases, called greenhouse gases, and not lost out into space. Carbon dioxide, water vapor, and methane are examples. Carbon dioxide, water vapor, and methane are examples.

19. References Composition of Earth’s Atmosphere - http://nsm1.nsm.iup.edu/hovan/classes/geos103_outline.html Composition of Earth’s Atmosphere - http://nsm1.nsm.iup.edu/hovan/classes/geos103_outline.html http://nsm1.nsm.iup.edu/hovan/classes/geos103_outline.html http://nsm1.nsm.iup.edu/hovan/classes/geos103_outline.html Layers of Earth’s Atmosphere - http://ferl.becta.org.uk/content_files/ferl/pages/fpp_02/f pp_03/implmentation_support_advice/module_a/atmoph.htm Layers of Earth’s Atmosphere - http://ferl.becta.org.uk/content_files/ferl/pages/fpp_02/f pp_03/implmentation_support_advice/module_a/atmoph.htm http://ferl.becta.org.uk/content_files/ferl/pages/fpp_02/f pp_03/implmentation_support_advice/module_a/atmoph.htm http://ferl.becta.org.uk/content_files/ferl/pages/fpp_02/f pp_03/implmentation_support_advice/module_a/atmoph.htm Aurora Borealis - http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm Aurora Borealis - http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm Greenhouse Effect - http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm Greenhouse Effect - http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm http://student.nu.ac.th/u43360619/e_g_auroraborealis.h tm