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Chapter 8: The Terrestrial Planets and Earth’s Moon

Chapter 8: The Terrestrial Planets and Earth’s Moon. Each of the terrestrial worlds has its’ own unique character. Comparative Planetology. There are four main processes that shape planetary surfaces. Impact Cratering is the fastest way to change a surface.

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Chapter 8: The Terrestrial Planets and Earth’s Moon

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  1. Chapter 8:The Terrestrial Planets and Earth’s Moon

  2. Each of the terrestrial worlds has its’ own unique character

  3. Comparative Planetology

  4. There are four main processes that shape planetary surfaces

  5. Impact Cratering is the fastest way to change a surface

  6. Cratering occurs when an object hits a surface at high speed

  7. A typical crater has a rim wall, a central peak and an ejecta blanket

  8. The Wells Creek Crater is the closest large crater The Cumberland City steam plant is on the northern edge of the crater. The crater is thought to be around 100 million years old

  9. Craters can sometimes tell us about the subsurface Mud splash craters on Mars

  10. Craters can be used to give relative dates of surfaces

  11. By counting craters we can tell the relative age of a surface

  12. We have fairly accurate ages for lunar surfaces by radioactive dating moon rocks

  13. The rate of cratering has not always been the same

  14. How can we learn about the interior of a planet?

  15. Seismometers & Seismograms The seismometer measures vibrations in the Earth’s crust

  16. Looking inside a planet with seismograms The two different types of waves travel differently through the various layers of Earth’s interior. S-waves don’t travel through liquids but P-waves do. The speed of the waves changes with depth causing them to curve

  17. Seismographs of a planet work on the same principal as sonograms Sonograms send ultrasonic sound waves into a body and form an image of the reflected waves. Seismograms use the “sound” waves from earthquakes to form images of the interior of a planet.

  18. The interiors of the terrestrial planets are all very similar The interiors have all undergone differentiation

  19. Differentiation means the heavy stuff sinks to the center and the light stuff floats to the surface

  20. Origin of the MoonThe Giant Impact Theory Before the collision, both objects had already differentiated. Most of the core of the impactor merged with the new Earth

  21. Because of how we got the Moon, Earth has a larger core than expected and the Moon has a smaller core

  22. Magnetic fields tell us something about the interior of a planet

  23. Compared to the other terrestrial planets, the Earth’s field is huge

  24. The source of Earth’s magnetic field is currents in the molten outer core The inner core rotates faster than outer core: the inner core “laps” the outer core every 400 to 500 years. Every half million years or so the field reverses, we aren’t sure why. We may be starting a reversal now.

  25. The geologic record tells us how the Earth’s magnetic field has changed

  26. Tectonism folds and wrinkles a surface to create mountains

  27. The Appalachians are an example of tectonism When viewed from orbit the folds and winkles are easily visible

  28. Plate Tectonics is driven by convection deep in the mantle of Earth

  29. Plate tectonics involves new land being created and old land being recycled

  30. Earth’s crustal plates are outlined by geologic activity

  31. The other terrestrial planets have different types of tectonics

  32. Mars appears to be a one plate world but it still has tectonics The giant rift valley known as Valles Marineris is the result of tectonic stresses opening up a crack in the surface that just kept growing since there was no plate movement

  33. Venus doesn’t show evidence of plates either We aren’t sure what kind of tectonics Venus has but it doesn’t appear to be plate tectonics like Earth. What’s going on inside Venus is still a hotly debated topic.

  34. Tectonics on Venus may be catastrophic The random distribution of craters around the surface of Venus and their pristine appearance leads some to believe Venus has unique tectonics The whole surface may melt and sink every half billion years in a globally catastrophic episode

  35. Mercury’s surface is ancient. Its tectonic activity ended long ago.

  36. The Moon, like Mercury, ended its tectonic activity long ago

  37. Volcanoes are, or were, important on all the terrestrial planets

  38. Volcanoes come in three types: Composite, shield and hot spot

  39. Composite volcanoes can erupt explosively Watch Mount St. Helens Eruption video

  40. Shield volcanoes tend to have very gentle slopes The Belknap volcano in Oregon along with the Martian and Venusian volcanoes are all shield volcanoes

  41. Olympus Mons is the largest volcano in the solar system

  42. Hot Spot volcanoes form chains of islands

  43. Erosion wears surfaces down Gradation is strongest on Earth but we also see it on Mars. We aren’t sure about Venus but it doesn’t seem prominent there

  44. The most significant erosion is done by liquid water

  45. Wind can also cause significant erosion Wind erosion can only occur if there is an atmosphere so we only see it on Earth, Mars and Venus

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