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09 lecture outline
This document summarizes a chapter about planetary geology. It discusses: - The interiors of terrestrial planets and how seismic waves reveal Earth's layered structure. - Geological processes that shape planetary surfaces, like impact cratering, volcanism, tectonics, and erosion. - How the amount of impact craters on a surface reveals its geological age. - The unique geology of specific planets, including the Moon's maria, Mercury's shrinkage, and evidence that water flowed on ancient Mars. - How plate tectonics continually shapes Earth's surface through seafloor spreading, subduction, and mountain building.
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09 lecture outline
- 1. Chapter 9 Lecture ©2014 Pearson Education, Inc. The Cosmic Perspective Seventh Edition Planetary Geology: Earth and the Other Terrestrial Worlds
- 2. Planetary Geology: Earthand the Other Terrestrial Worlds
- 3. 9.1 Connecting PlanetaryInteriors and Surfaces • Our goals for learning: – What are terrestrial planets like on the inside? – What causes geological activity? – Why do some planetary interiors create magnetic fields?
- 4. What are terrestrialplanets like on the inside?
- 5. Seismic Waves • Vibrations thattravel through Earth's interior tell us what Earth is like on the inside.
- 6. Earth's Interior • Core:highest density; nickel and iron • Mantle: moderate density; silicon, oxygen, etc. • Crust: lowest density; granite, basalt, etc.
- 7. • Applying whatwe have learned about Earth's interior to other planets tells us what their interiors are probably like. Terrestrial Planet Interiors
- 8. Differentiation • Gravity pulls high-density materialto center. • Lower-density material rises to surface. • Material ends up separated by density.
- 9. Lithosphere • A planet'souter layer of cool, rigid rock is called the lithosphere. • It "floats" on the warmer, softer rock that lies beneath.
- 10. Strength of Rock •Rock stretches when pulled slowly but breaks when pulled rapidly. • The gravity of a large world pulls slowly on its rocky content, shaping the world into a sphere.
- 11. Special Topic: How dowe know what's inside Earth? • P waves push matter back and forth. • S waves shake matter side to side
- 12. Special Topic: How dowe know what's inside Earth? • P waves go through Earth's core, but S waves do not. • We conclude that Earth's core must have a liquid outer layer.
- 13. Thought Question What isnecessary for differentiation to occur in a planet? a) It must have metal and rock in it. b) It must be a mix of materials of different density. c) Material inside must be able to flow. d) All of the above e) b and c
- 14. Thought Question What isnecessary for differentiation to occur in a planet? a) It must have metal and rock in it. b) It must be a mix of materials of different density. c) Material inside must be able to flow. d) All of the above e) b and c
- 15. What causes geologicalactivity?
- 16. Heating of PlanetaryInteriors • Accretion and differentiation when planets were young • Radioactive decay is most important heat source today.
- 17. Cooling of PlanetaryInteriors • Convection transports heat as hot material rises and cool material falls. • Conduction transfers heat from hot material to cool material. • Radiation sends energy into space.
- 18. • Smaller worldscool off faster and harden earlier. • The Moon and Mercury are now geologically "dead." Role of Size
- 19. • Heat contentdepends on volume. • Loss of heat through radiation depends on surface area. • Time to cool depends on surface area divided by volume: • Larger objects have a smaller ratio and cool more slowly. 3 Surface area–to–volume ratio = 4πr 2 4πr 3 = 3 r Surface Area–to–Volume Ratio
- 20. Why do someplanetary interiors create magnetic fields?
- 21. Sources of MagneticFields • Motions of charged particles are what create magnetic fields.
- 22. Sources of MagneticFields • A world can have a magnetic field if charged particles are moving inside. • Three requirements: – Molten, electrically conducting interior – Convection – Moderately rapid rotation
- 23. What have welearned? • What are terrestrial planets like on the inside? – All terrestrial worlds have a core, mantle, and crust. – Denser material is found deeper inside. • What causes geological activity? – Interior heat drives geological activity. – Radioactive decay is currently main heat source. • Why do some planetary interiors create magnetic fields? – Requires motion of charged particles inside a planet
- 24. 9.2 Shaping PlanetarySurfaces • Our goals for learning: – What processes shape planetary surfaces? – How do impact craters reveal a surface's geological age? – Why do the terrestrial planets have different geological histories?
- 25. What processes shapeplanetary surfaces?
- 26. Processes That ShapeSurfaces • Impact cratering – Impacts by asteroids or comets • Volcanism – Eruption of molten rock onto surface • Tectonics – Disruption of a planet's surface by internal stresses • Erosion – Surface changes made by wind, water, or ice
- 27. Impact Cratering • Mostcratering happened soon after the solar system formed. • Craters are about 10 times wider than object that made them. • Small craters greatly outnumber large ones.
- 28. Meteor Crater (Arizona)MeteorCrater (Arizona) Tycho Crater (Moon)Tycho Crater (Moon) Impact Craters
- 29. "Standard" crater"Standard" craterImpact into icyImpact into icy groundground Eroded craterEroded crater Impact Craters on Mars
- 30. Volcanism • Volcanism happens whenmolten rock (magma) finds a path through lithosphere to the surface. • Molten rock is called lava after it reaches the surface.
- 31. Runny lava makesRunnylava makes flat lava plains.flat lava plains. Slightly thickerSlightly thicker lava makeslava makes broadbroad shieldshield volcanoesvolcanoes.. Thickest lava makesThickest lava makes steepsteep stratovolcanoesstratovolcanoes.. Lava and Volcanoes
- 32. • Volcanism alsoreleases gases from Earth's interior into the atmosphere. Outgassing
- 33. • Convection ofthe mantle creates stresses in the crust called tectonic forces. • Compression of crust creates mountain ranges. • Valley can form where crust is pulled apart. Tectonics
- 34. Plate Tectonics onEarth • Earth's continents slide around on separate plates of crust.
- 35. Erosion • Erosion isa blanket term for weather-driven processes that break down or transport rock. • Processes that cause erosion include: – glaciers – rivers – wind
- 36. Erosion by Water •The Colorado River continues to carve Grand Canyon.
- 37. Erosion by Ice •Glaciers carved the Yosemite Valley.
- 38. Erosion by Wind •Wind wears away rock and builds up sand dunes.
- 39. Erosional Debris • Erosioncan create new features such as deltas by depositing debris.
- 40. How do impactcraters reveal a surface's geological age?
- 41. History of Cratering •Most cratering happened in the first billion years. • A surface with many craters has not changed much in 3 billion years.
- 42. Cratering of Moon •Some areas of Moon are more heavily cratered than others. • Younger regions were flooded by lava after most cratering.
- 43. Cratering map ofthe MoonCratering map of the Moon's entire surface's entire surface Cratering of Moon
- 44. Why do theterrestrial planets have different geological histories?
- 45. • Smaller worldscool off faster and harden earlier. • Larger worlds remain warm inside, promoting volcanism and tectonics. • Larger worlds also have more erosion because their gravity retains an atmosphere. Role of Planetary Size
- 46. • Planets closeto the Sun are too hot for rain, snow, ice and so have less erosion. • Hot planets have more difficulty retaining an atmosphere. • Planets far from the Sun are too cold for rain, limiting erosion. • Planets with liquid water have the most erosion. Role of Distance from Sun
- 47. • Planets withslower rotation have less weather, less erosion, and a weak magnetic field. • Planets with faster rotation have more weather, more erosion, and a stronger magnetic field. Role of Rotation
- 48. Thought Question How doesthe cooling of planets and potatoes vary with size? a) Larger size makes it harder for heat from inside to escape. b) Larger size means a bigger ratio of volume to surface area. c) Larger size takes longer to cool. d) all of the above
- 49. Thought Question How doesthe cooling of planets and potatoes vary with size? a) Larger size makes it harder for heat from inside to escape. b) Larger size means a bigger ratio of volume to surface area. c) Larger size takes longer to cool. d) all of the above
- 50. What have welearned? • What processes shape planetary surfaces? – Cratering, volcanism, tectonics, erosion • How do impact craters reveal a surface's geological age? – The amount of cratering tells us how long ago a surface formed. • Why do the terrestrial planets have different geological histories? – Differences arise because of planetary size, distance from Sun, and rotation rate.
- 51. 9.3 Geology ofthe Moon and Mercury • Our goals for learning: – What geological processes shaped our Moon? – What geological processes shaped Mercury?
- 52. What geological processesshaped our Moon?
- 53. Lunar Maria • Smooth,dark lunar maria are less heavily cratered than lunar highlands. • Maria were made by floods of runny lava.
- 54. LargeLarge impactimpact cratercrater weakensweakens crust.crust. Heat build-Heat build- upallowsup allows lava to welllava to well up toup to surface.surface. EarlyEarly surface issurface is coveredcovered with craters.with craters. Cooled lava isCooled lava is smoother andsmoother and darker thandarker than surroundings.surroundings. Formation of Lunar Maria
- 55. Tectonic Features • Wrinklesarise from cooling and the contraction of a lava flood.
- 56. Geologically Dead • Moonis considered geologically "dead" because geological processes have virtually stopped.
- 57. What geological processesshaped Mercury?
- 58. Cratering of Mercury •Mercury has a mixture of heavily cratered and smooth regions like the Moon. • Smooth regions are likely ancient lava flows.
- 59. The Rembrandt BasinisThe Rembrandt Basin is a large impact crater ona large impact crater on Mercury.Mercury. Hollows in a crater floorHollows in a crater floor created by escaping gases.created by escaping gases. Cratering of Mercury
- 60. • Long cliffsindicate that Mercury shrank early in its history. Tectonics on Mercury
- 61. What have welearned? • What geological processes shaped our Moon? – Early cratering is still present. – Maria resulted from volcanism. • What geological processes shaped Mercury? – Had cratering and volcanism similar to Moon – Tectonic features indicate early shrinkage.
- 62. 9.4 Geology ofMars • Our goals for learning: – What geological processes have shaped Mars? – What geological evidence tells us that water once flowed on Mars?
- 63. • Percival Lowellmisinterpreted surface features seen in telescopic images of Mars. "Canals" on Mars
- 64. What geological processeshave shaped Mars?
- 65. • The amountof cratering differs greatly across Mars's surface. • Many early craters have been erased. Cratering on Mars
- 66. Volcanism on Mars •Mars has many large shield volcanoes. • Olympus Mons is largest volcano in solar system.
- 67. • The systemof valleys known as Valles Marineris is thought to originate from tectonics. Tectonics on Mars
- 68. What geological evidencetells us that water once flowed on Mars?
- 69. • Close-up photosof Mars show what appear to be dried-up riverbeds. Dry Riverbeds?
- 70. Insert TCP7e Figure 9.29 InsertTCP7e Figure 9.29 Erosion of Craters • Details of some craters suggest they were once filled with water.
- 71. Martian Rocks • Marsrovers have found rocks that appear to have formed in water.
- 72. Martian Rocks • Marsrovers have found rocks that appear to have formed in water.
- 73. Image Credit: NASA/JPL HydrogenContent • Map of hydrogen content (blue) shows that low- lying areas contain more water ice.
- 74. Crater Walls • Gullieson crater walls suggest occasional liquid water flows have happened less than a million years ago.
- 75. What have welearned? • What are the major geological features of Mars? – Differences in cratering across surface – Giant shield volcanoes – Evidence of tectonic activity
- 76. What have welearned? • What geological evidence tells us that water once flowed on Mars? – Some surface features look like dry riverbeds. – Some craters appear to be eroded. – Rovers have found rocks that appear to have formed in water. – Gullies in crater walls may indicate recent water flows.
- 77. 9.5 Geology ofVenus • Our goals for learning: – What geological processes have shaped Venus? – Does Venus have plate tectonics?
- 78. What geological processeshave shaped Venus?
- 79. Insert TCP7e figure 9.35 InsertTCP7e figure 9.35 Radar Mapping • Its thick atmosphere forces us to explore Venus's surface through radar mapping.
- 80. Cratering on Venus •Venus has impact craters, but fewer than the Moon, Mercury, or Mars.
- 81. Volcanoes on Venus •It has many volcanoes, including both shield volcanoes and stratovolcanoes.
- 82. Tectonics on Venus •The planet's fractured and contorted surface indicates tectonic stresses.
- 83. Erosion on Venus •Photos of rocks taken by landers show little erosion.
- 84. Does Venus haveplate tectonics? • Venus does not appear to have plate tectonics, but entire surface seems to have been "repaved" 750 million years ago. • Weaker convection? • Thicker or more rigid lithosphere?
- 85. What have welearned? • What geological processes have shaped Venus? – Venus has cratering, volcanism, and tectonics but not much erosion. • Does Venus have plate tectonics? – The lack of plate tectonics on Venus is a mystery.
- 86. 9.6 The UniqueGeology of Earth • Our goals for learning: – How is Earth's surface shaped by plate tectonics? – Was Earth's geology destined from birth?
- 87. How is Earth'ssurface shaped by plate tectonics?
- 88. Continental Motion • Motionof the continents can be measured with GPS.
- 89. Continental Motion • Theidea of continental drift was inspired by the puzzle-like fit of the continents. • Mantle material erupts where the seafloor spreads.
- 90. Seafloor Crust • Thinseafloor crust differs from thick continental crust. • Dating of the seafloor shows that it is usually quite young.
- 91. Seafloor Recycling • Seaflooris recycled through a process known as subduction.
- 92. Surface Features • Majorgeological features of North America record the history of plate tectonics.
- 93. Surface Features • TheHimalayas formed from a collision between plates.
- 94. Surface Features • TheRed Sea is formed where plates are pulling apart.
- 95. Rifts, Faults, Earthquakes •The San Andreas fault in California is a plate boundary. • Motion of plates can cause earthquakes.
- 96. Plate Motions • Measurementsof plate motions tell us past and future layout of the continents.
- 97. Hot Spots • TheHawaiian islands have formed where a plate is moving over a volcanic hot spot.
- 98. Was Earth's geologydestined from birth?
- 99. Earth's Destiny • Manyof Earth's features are determined by its size, rotation, and distance from Sun. • The reason for plate tectonics is not yet clear.
- 100. What have welearned? • How is Earth's surface shaped by plate tectonics? – Measurements of plate motions confirm the idea of continental drift. – Plate tectonics is responsible for subduction, seafloor spreading, mountains, rifts, and earthquakes.
- 101. What have welearned? • Was Earth's geology destined from birth? – Many of Earth's features are determined by its size, distance from Sun, and rotation rate. – The reason for plate tectonics is still a mystery.