Planetary Geology pdf - NASA

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map, is to derive a general geologic history of the region being mapped. The geologic history synthesizes, in written format, the events that formed the surface seen in the photoÑincluding interpretation of the processes in the formation of rock units and events that have modified the unitsÑand is presented in chronological order from oldest to youngest. Figure 16.1 shows a sample geologic map, including its unit descriptions and stratigraphic column. The relative ages were determined in the following manner: The cratered terrain has more (and larger) craters than the smooth plains unitÑindicating that the cratered terrain unit is older. In addition, fault 1 cuts across the cratered terrain, but does not continue across the smooth plains. Faulting occurred after the formation of the cratered terrain and prior to the formation of the smooth plainsÑindicating that the smooth plains unit is younger than the cratered terrain and fault 1. The crater and its ejecta unit occurs on top of the smooth plains unit, and thus is younger. Finally, fault 2 cuts across all the units, including the crater and its ejecta unit, and is thus the youngest event in the region. The geologic history that could be derived from this map would be similar to the following: ÒThis region was cratered and then faulted by tectonic activity. After the tectonic activity, a plains unit was emplaced. Cratering continued after the emplacement of the smooth plains unit, as seen by the craters superposed on the smooth plains and the large, young crater mapped as its own unit. Finally, there has been a continuation (or reactivation) of tectonic activity, indicated by the major fault which postdates the young crater. Ò The geologic mapping principles listed above have been applied to the Moon as a whole and a generalized geologic time scale has been derived (Figure 16.2). Two important units on the Moon are the Fra Mauro Formation and the Janssen Formation, ejecta deposits from the Imbrium and Nectaris impact basins, respectively. These are Procedure and Questions 200 widespread units that were formed in the hours following the gigantic impacts that excavated the basins, and hence are excellent datum planes. Rock samples returned from several localities on the Moon enable radiometric dates to be placed on the generalized time scale. Geologic mapping of impact crater-related deposits requires some knowledge of the impact process. When one planetary object such as meteoroid, strikes another there is a transfer of energy that causes the crater to form by having material excavated from the ÒtargetÓ surface. Most of the incoming object is destroyed by fragmentation, melting, and vaporization. Figure 16.3 is a diagram showing typical impact crater deposits. Extending about one crater diameter outward from the rim is a zone of continuous ejecta deposits consisting of material thrown out from the crater (called ejecta) and local material churned up by the ejecta. Extending farther outward is a zone of discontinuous ejecta deposits; unlike the zone of continuous ejecta deposits, these are surfaces that have been affected only locally by the impact. Bright, wispy rays extend beyond the zone of discontinuous ejecta deposits. Distinctive secondary craters formed by blocks of ejecta occur in singlets, doublets, triplets, chains and clusters. They often form a ÒherringboneÓ ridge pattern, the apex of which points toward the primary, or parent crater. On the Moon and Mercury, geologic mapping involves distinguishing various deposits related to impact craters. In addition, most of the terrestrial planets have experienced volcanism that produced vast basaltic lava flows. Samples returned by the Apollo astronauts show that the dark, smooth areas of the Moon, named maria, are basalt flows. Some of these basalt flows were generated as enormous ÒfloodsÓ of lava, similar to the Columbia River Plateau of the northwest United States; others were produced as thin sheets that were fed by rivers of lava, visible today as sinuous rilles (Figure 16.4). The area you will be mapping is the Euler (pronounced ÔoilerÕ) crater region on the Moon. Euler is an impact crater, 28 km in diameter, located at 23¡20'N, 29¡10'W, placing it on the rim of the Imbrium basin on the near side of the Moon(see Figure 16.5). It is about 450 km northwest of the 93 km-diameter Copernicus impact crater. The photograph (Figure 16.6) was obtained with a mapping camera on board the Apollo 17 service module from an altitude of about 117 km. The photograph is 180 km on a side; the sun elevation angle at its center is about 6.5¡. Exercise Sixteen: Photogeologic Mapping of the Moon Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ
To establish age relations and interpret the mode of formation of the rock units in the area it is best to examine the area in detail. Enlargements of Figure 16.6 will be used for this purpose. Part A 1. Study Figure 16.7 (an enlargement of the southwest quadrant of Figure 16.6) in detail and list observations and evidence which might establish the relative age of the rugged clusters of hills and the intervening smooth regions. 2. List possible reasons why craters are more readily apparent on the smooth regions (vs. the hills). 3. Indicate your conclusion about the relative age of the two terrains (which is older). 4. List the characteristics of the smooth unit which might bear on its mode of formation; suggest a possible origin(s) for this unit. 5. List the characteristics of the rugged hills and suggest possible origins. Interpretations should be preliminary pending examination of the other quadrant enlargements (see also Figure 16.5). 6. Study Figure 16.8 (an enlargement of the northwest quadrant of Figure 16.6). List any additional characteristics associated with the smooth region which might bear on its mode of origin. 7. Briefly describe the several clusters of craters visible in Figure 16.8. What is their age in relation to the smooth region? 8. Propose a tentative mode of origin for these crater clusters, including any possible directional information. 9. Study Figure 16.9 (an enlargement of the northeast quadrant of Figure 16.6). Briefly describe the various characteristics of the topography surrounding and associated with the crater Euler. 10. Propose an origin for the topography of the material at crater Euler. 11. Study the outer boundary of the unit which includes Euler and its associated crater materials (recall Figure 16.3). Using Figures 16.6, 16.7, 16.8, 16.9, 16.10 measure and record the distance from the rim crest of Euler to the outer boundary of the crater materials in a NW, NE, SE, and SW direction. Exercise Sixteen: Photogeologic Mapping of the Moon 201 EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences
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National Aeronautics and Space Admi
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A ctivities in Planetary Geology fo
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Preface Introduction Special Note t
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We are living in a time of revoluti
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Exercise One Suggested Correlation
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Part One 1. (Answers will vary.) Vo
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5. Based on the number of pictures
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_____ 08/19/92 earthquake, central
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165° W 75°W 0° 75°E180°E 75°N
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1. a. The volcano has a circular ba
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Exercise Two Volcanism Purpose By s
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7. List some factors that might aff
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. How is it similar? Examine the vi
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N 200 m Figure 2.1. Mount Capulin,
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N Figure 2.3. Oblique aerial view o
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Figures 2.7.a., 2.7.b. Meteor Crate
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N Figure 2.9. Mosaic of Landsat fra
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1. a. Sketch should show steep side
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Exercise Three Purpose By using ste
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Gradation 2. Figure 3.4 shows a por
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. Examine the broad, steep face tha
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e. Determine the sequence of events
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Exercise Three: Geologic Landforms
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Exercise Three: Geologic Landforms
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N Figure 3.8. Sierra Caballos Mount
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Exercise Four Impact Cratering Inst
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Objective To determine the initial
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Name Exercise Four Impact Cratering
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Sketch area In the fourth section o
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Part C Shot 1 (smallest) Shot 2 (ne
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10 km Exercise Four: Impact Crateri
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Science Standards ■ Earth and Spa
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Figure 5.1. Comparison of the forma
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Exercise Five Purpose To illustrate
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Part B: Volcanic Explosive Craterin
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N 100 km Figure 5.5. Olympus Mons,
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Exercise Six Suggested Correlation
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Figure 6.1. Different sand surfaces
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Exercise Six Purpose To learn how p
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*c. What geologic process(es) forme
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Figure 6.4. Photograph of lunar mar
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Exercise Seven Coriolis Effect Inst
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Purpose By tracing an object as it
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N 100 km Figure 7.1. Centered at 20
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elow this is the solid core of the
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for turbulent, inclement weather on
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7. Examine the atmosphere of Venus
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Figure 8.5. Viking Orbiter image 78
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N 102 Figure 8.7. Jupiter as seen b
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emove the flaps). Three windows are
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Purpose In this experiment you will
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10. Based on your three sketches of
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The wind is at work on other planet
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Unit Four The three decades from th
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1. The highlands are bright, rugged
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6. Based on the number of craters,
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Mercury Venus Earth Moon Mars Mean
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Figure 10.2. Mariner 10 mosaic of M
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C Figure 10.4. Magellan radar mosai
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Exercise Eleven Suggested Correlati
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Exercise Eleven Purpose To learn to
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. If windstreaks are dust deposits
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Figure 11.2. Ius Chasma, part of th
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Exercise Eleven: Geologic Features
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Exercise Twelve Suggested Correlati
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Exercise Twelve Purpose To learn ab
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So far all the figures have shown f
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Page 141 and 142: Exercise Thirteen Suggested Correla
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Page 155 and 156: A Figure 13.3. The surface of Rhea,
Page 157 and 158: Exercise Fourteen Planets in Stereo
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Page 173 and 174: Exercise Fifteen Purpose The object
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Page 179 and 180: Figure 15.3. Apollo 15 photograph o
Page 181 and 182: Part A 1. Contacts are sharp; trans
Page 183 and 184: Geologic History Youngest Youngest
Page 185: Exercise Sixteen Purpose Through ob
Page 191 and 192: Figure 16.3. Diagram of typical imp
Page 193 and 194: Exercise Sixteen: Photogeologic Map
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Page 201 and 202: Answer Key Map after 1) Scott et al
Page 203 and 204: Exercise Seventeen Purpose Through
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Page 211 and 212: Terrain: A region of a surface shar
Page 213 and 214: Cattermole, P. (1994). Venus: The G
Page 215 and 216: Object Moon Moon Moon Moon Moon Moo
Page 217 and 218: Object Jupiter Jupiter Jupiter Jupi
Page 219 and 220: 1.6 Regional Planetary Image Facili
Page 221 and 222: 2. Map Link 25 Eat Mason Santa Barb
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