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Planet Earth How old is the Earth? 1. 2. 3. 4. 5. :10 140 million years 500 million years 1 billion years 4.6 billion years 13 billion years 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0% 73 74 0% 75 76 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 101 102 103 104 105 106 107 108 109 110 111 1112 0 of 116 113 2114 115 3116 77 0% 78 790%80 97 99 98 4 100 5 The Early History of the Earth Earth formed 4.6 billion years ago from the inner solar nebula. Four main stages of evolution: 1. 2. The mixing of substances. Lighter substances sinking to the bottom, while heavier substances rise to the top. Heavier substances sinking to the bottom, while lighter substances rise to the top. The chemical change of substances near the surface of a planet due to chemical reactions with the atmosphere. The chemical change of substances near the core of a planet induced by great heat. 3. 4. 5. What is “differentiation”? :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 0% 74 0%75 76 78 0% 79 80 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 1113 0 of 116 114 2 115 0% 77 116 3 97 4 5 The Early History of the Earth Earth formed 4.6 billion years ago from the inner solar nebula. Four main stages of evolution: Two sources of heat in Earth’s interior: • Potential energy of infalling material • Decay of radioactive material Most traces of bombardment (impact craters) now destroyed by later geological activity 1. Global climate change caused by variations in the sun’s energy output. Global climate change caused by a massive meteorite/comet impact. A reptile dysfunction. A nearby stellar explosion (supernova / gamma-ray burst). Nothing. They still exist (see, e.g., Jurassic Park)! 2. 3. 4. 5. What killed the dinosaurs (according to the most widely accepted theory)? :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 0% 93 0% 98 99 0% 100 101 102 103 104 105 106 107 108 109 110 111 112 0 of 116 113 1 940%95 0% 97 96 114 116 115 2 3 4 5 Meteorite Impacts on Earth Over 150 impact craters found on Earth. Most famous example: Barringer Crater near Flagstaff, AZ: Impact Craters on Earth Barringer Crater: ~ 1.2 km diameter; 200 m deep Formed ~ 50,000 years ago by a meteorite of ~ 80 – 100 m diameter Much larger impact features exist on Earth: Impact of a large body (comet nucleus?) formed a crater ~ 180 – 300 km in diameter in the Yucatán peninsula, ~ 65 million years ago: The Chicxulub Crater This impact may have caused major climate change, leading to the extinction of many species, including dinosaurs. Earth’s Interior Direct exploration of Earth’s interior (e.g. drilling) is impossible. Earth quakes produce seismic waves. Earth’s interior can be explored through seismology: Seismic waves are bent or bounce off transitions between different materials or different densities or temperatures. If you are standing next to railroad tracks and you don’t see or hear a train, you can tell if there’s a train approaching by putting your ear on the tracks. This works because … 1. your visual abilities improves when you block one of your ears. sound waves travel more rapidly along the tracks than through the air. Sound waves get less absorbed when traveling along the tracks than through the air. All of the above. 2. and 3. 2. 3. 4. 5. :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 81 82 83 84 85 86 87 88 89 90 91 92 0% 93 101 102 103 104 105 106 107 108 109 110 111 112 113 0 of 116 1 94 114 0% 95 115 2 0%97 96 116 3 0% 98 4 99 80 0% 100 5 Earth’s Interior (II) Basic structure: Solid crust (light [Si-based] materials) Solid mantle (light elements, iron-poor) Liquid core (iron-rich) Solid inner core (iron-rich) Earth’s interior gets hotter towards the center. Earth’s core is as hot as the sun’s surface; metals are liquid near the core. Earth’s Magnetic Field Earth’s core consists mostly of iron + nickel (materials that magnets are made out of) Convective motions and rotation of the core generate a dipole magnetic field The Role of Earth’s Magnetic Field Earth’s magnetic field protects Earth from high-energy particles coming from the sun (solar wind). Surface of first interaction of solar wind with Earth’s magnetic field = Bow shock Region where Earth’s magnetic field dominates = magnetosphere Some high-energy particles leak through the magnetic field and produce a belt of high-energy particles around Earth: The Van Allen belts Which phenomenon is caused by the interaction of energetic particles from the sun with Earth’s magnetosphere? 1. :10 Northern lights (aurora borealis). Sun spots. Prominences. Hurricanes. Earthquakes. 2. 3. 4. 5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0% 73 74 0% 75 76 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 101 102 103 104 105 106 107 108 109 110 111 1112 0 of 116 113 2114 115 3116 77 0% 78 790%80 97 99 98 4 100 5 The Aurora (Polar Light) As high-energy particles leak into the lower magnetosphere, they excite molecules near the Earth’s magnetic poles, causing the Aurora Tectonic Plates Earth’s crust is composed of several distinct tectonic plates, which are in constant motion with respect to each other → Plate tectonics Tectonic Plates (II) Evidence for plate tectonics can be found on the ocean floor … and in geologically active regions all around the Pacific Geological activity around the Pacific Earthquakes: Kobe (Japan) Volcanism: Pinatubo (Philippines) Volcanism: Mt. St. Helen Earthquakes: San Francisco The major Tsunami of 2004 in the Indian Ocean was caused by tectonic activity at the boundary between … 1) :10 the African and the IndianAustralian Plates. the Indian-Australian and Eurasian Plates. the African and the Arabian Plates. the Arabian and the IndianAustralian Plates. the African and Antarctic Plates. 2) 3) 4) 5) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 0 of 116 0% 112 1) 113 0% 114 2) 115 0% 116 3) 0% 4) 0% 5) Plate Tectonics Tectonic plates move with respect to each other. Where plates move toward each other, plates can be pushed upward and downward → formation of mountain ranges, some with volcanic activity, earthquakes Where plates move away from each other, molten lava can rise up from below → volcanic activity Active Zones Resulting from Plate Tectonics The interaction between the Pacific and the North American Plates is responsible for the formation of 1) 2) 3) 4) 5) :10 the Hawaiian Islands. the Alps. the Rocky Mountains. the Andes. the Appalachian Mountains. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 0 of 116 0% 1) 0% 2) 0% 3) 0% 4) 0% 5) Volcanism on Earth (I) Subduction Zones Volcanism on Earth is commonly found along subduction zones (e.g., Rocky Mountains). Example: Stromboli (Sicily, Italy, 1998) This type of volcanism is not found on Venus or Mars. Hawaii is also very volcanically active. Is this also because Hawaii is located at a plate boundary? 1) 2) 3) 4) 5) Yes, it is located at the boundary of the Pacific plate. Yes, it is located at the boundary of the North American plate. Yes, it is located at the boundary of the Eurasian plate. No. This must be a different kind of volcanic activity. No. Hawaii is not volcanically active. :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 81 82 83 84 85 86 87 88 89 90 91 92 0% 93 101 102 103 104 105 106 107 108 109 110 111 112 113 115 116 0 of 116 1) 94 114 0% 95 2) 0%97 96 3) 0% 99 98 4) 80 0% 100 5) Volcanism on Earth (II) Shield Volcanoes Found above hot spots: Fluid magma chamber, from which lava erupts repeatedly through surface layers above. All volcanoes on Venus and Mars are shield volcanoes Shield Volcanoes (II) Tectonic plates moving over hot spots producing shield volcanoes → Chains of volcanoes Example: The Hawaiian Islands Earth’s Tectonic History Earth’s Tectonic History (II) History of Geological Activity Surface formations visible today have emerged only very recently compared to the age of Earth. Guess: How thick is the Earth’s breathable atmosphere (beyond which you would need oxygen masks to breathe), compared to the Earth’s radius? 1) 2) 3) 4) 5) 1/24,000 Earth radius. 1/800 Earth radius. 1/15 Earth radius. 1 Earth radius. :10 10 Earth radii. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0% 73 74 0% 75 76 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 101 102 103 104 105 106 107 108 109 110 111 1)112 0 of 116 113 2)114 115 3)116 77 0% 78 790%80 97 99 98 4) 100 5) Earth’s Atmosphere Only about 1/800 of the Earth’s radius! Which is the most common gas in Earth’s atmosphere? 1) 2) 3) 4) 5) :10 Oxygen Nitrogen Carbon dioxide Methane Water vapor 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0% 73 74 0% 75 76 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 101 102 103 104 105 106 107 108 109 110 111 1)112 0 of 116 113 2)114 115 3)116 77 0% 78 790%80 97 99 98 4) 100 5) The Atmosphere Earth had a primeval atmosphere from remaining gasses captured during formation of Earth Do you think that the Earth’s atmosphere is still very similar to what it was about 4 billion years ago? 1) Yes 2) No :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 0%54 55 56 57 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 1) 113 114 115 116 0 of 116 58 0% 2) The Atmosphere Earth had a primeval atmosphere from remaining gasses captured during formation of Earth Atmospheric composition severely altered (→ secondary atmosphere) through a combination of several processes: Sources of Atmospheric Gas • Outgassing: Release of gasses bound in compounds in the Earth’s interior through volcanic activity • Later bombardment with icy meteoroids and comets Loss of Atmospheric Gas • Chemical reactions in the oceans • Energetic radiation from space (in particular, UV) :10 Which of these processes might be the main reason that Mercury has almost no atmosphere? 1. 2. Thermal Escape Stripping by energetic radiation from space Condensation Chemical reactions Ejection by impacts 3. 4. 5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 0 of 116 0% 1 0% 2 0% 0% 0% 116 3 4 5 Which of these forms of radiation from space can reach the Earth unabsorbed? 1) 2) 3) 4) 5) :10 Radio waves. Infrared light. Ultraviolet light. X-rays. Gamma-rays. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0% 73 74 0% 75 76 0% 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 101 102 103 104 105 106 107 108 109 110 111 1)112 0 of 116 113 2)114 115 3)116 77 0% 78 790%80 97 99 98 4) 100 5) The Electromagnetic Spectrum Wavelength Frequency Need satellites to observe High flying air planes or satellites The Interactions between Light and Molecules X-rays 1) Splitting up molecules into atoms: 2) Ionizing (kicking electrons out of) atoms or molecules Nitrogen (N2) / Oxygen (O2) The Interactions between Light and Molecules Ultraviolet Splitting up molecules, in particular, Ozone: Ozone (O3) Oxygen (O2) Why is the totally eclipsed moon visible at all (in a faint red glow)? Because it is still glowing from the 1) intense light it received during full moon before the eclipse. Because it is illuminated by sunlight reflected off other terrestrial planets. Because it is illuminated by sunlight scattered within the Earth’s atmosphere. Because it is very shy during the eclipse and turns red when you are looking at it. None of the above: The totally eclipsed moon is completely black. 2) 3) 4) 5) :10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 1130%114 115 0% 116 0% 0% 3) 4) 0 of 116 1) 2) 0% 5) The Interactions between Light and Molecules Visible Light Penetrates through the atmosphere mostly unabsorbed, but can get scattered: This is why the sun appears red at sunrise and sunset; and why the sky is blue (if it’s not cloudy) The Interactions between Light and Molecules Infrared Causes asymmetric molecules to rotate This is the essential step of the Greenhouse Effect! Carbon dioxide (CO2) / Water vapor (H2O) / any other asymmetric molecules (greenhouse gases) We know that UV and X-ray radiation from space is heating the atmosphere. Thus, do you expect that the atmosphere becomes hotter or colder with height, very high above the ground? 1) 2) 3) :10 Hotter with increasing height. No temperature change. Colder with increasing height. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 0%74 73 81 82 83 84 85 86 87 88 89 90 91 92 93 101 102 103 104 105 106 107 108 109 110 111 112 113 1) 75 0% 76 94 95 96 114 115 116 2) 77 0%79 78 97 98 99 3) 80 100 The Temperature Structure of Earth’s Atmosphere Exosphere: Heated by UV and X-rays from space Thermosphere: Heated by X-rays from space Altitude Top of Ozone Layer Ozone Layer Stratosphere: Heated by UV radiation from space Troposphere: Heated by greenhouse effect Temperature Atmosphere gets colder at larger distance from heat sources.