Homework for Precambrian Geology KEY Structural Geology Use these questions to test your knowledge of the Precambrian Geology Use these questions to test your knowledge of Precambrian Geology. Note the fourth quarter format. 1) The oldest rocks on the Earth are: a) rocks of the continental margin. b) rocks of the oceanic crust. c) rocks of the continental interior. d) meteorites from space. 2) The most widely accepted hypothesis for the origin of the Moon is: (a) planetary capture. (b) the impactor hypothesis. (c) the dual formation hypothesis. (d) the nebular hypothesis. 3) What happened to the core of the impactor? a) It was blown into space. b) It was accreted to form the Moon. c) It was unaffected by the impact. d) It sank into the Earth and combined with its core. 4) The Earth’s hotter Archean surface temperatures are indicated by the presence of: a) komatiite rocks. b) basalt rocks. c) andesite rocks. d) granite rocks. 5) Archean rocks are commonly exposed: a) on the continental margins. b) in the shield areas of the continental interiors. c) on the ocean floor. d) in orogenic belts. 6) The most common primary rock association of the Archean crust is: a) komatiite lava. b) greenstone belts. c) granulite-gniess. (Greenstone belts cover less surface) d) granite-granodiorite. 7) Which of the following statements concerning the deformation of greenstone belts is NOT true? a) Greenstone belts are cut by great normal faults.. b) Greenstone belts have been metamorphosed. c) Greenstone belts have been intruded by granite. d) Greenstone belts have been folded by compression. 8) Which of the following processes was responsible for the growth of Archean continents? a) Intrusion at the edges of small plates. b) Island arcs accreted to the continental margins at subduction zones. c) Sediment wedges welded to the continental edge by converging plates. d) All of the above.. 9) All of the following are mechanisms for growth of Archean continents EXCEPT: a) collision of large continents.. Archean plates small due fast convection => rifting b) accretion of terranes to the continental margins. c) intermediate and felsic magmas intruded the edges of miniature plates. d) oceanic sediments welded to the continental margin by converging plates. 10) Which sedimentary rock type does NOT characterize Archean sedimentation? a) Graywacke. b) Limestone.. Carbonates are rare in the Archean c) Chert. d) Shale. 11) The Proterozoic Eon encompasses what proportion of total Earth history? (Hint 2 b.y. / 4.6 b.y.) a) 22%. b) 43%. c) 62%. d) 87%. 12) Which statement about Proterozoic tectonics is NOT true? a) Continental rifting slowed, allowing continents to grow larger. b) Shallow marine sediments were deposited along the continental margins. c) Mantle convection slowed, allowing larger continents to form. d) Mantle convection was even greater than in the previous Archean.. 13) Which type of tectonic activity was NOT present in the Early Proterozoic of North America? (Hint: too cool for komatiites to form) a) Formation of greenstone belts.. b) Continental collisions. c) Continental rifting. d) Continental drifting. 14) The largest belt of folded rocks indicating Proterozoic continental collisions is called the: a) Grenville Orogen. b) Trans-Hudson Orogen.. c) Mazatal Orogen. d) Wopmay Orogen 15) The last major Proterozoic collision before assembly of Rodinia is recorded by rocks in the: a) Grenville Orogen.. (on field trip 1) b) Trans-Hudson Orogen. c) Mazatal Orogen. d) Wopmay Orogen 16) Late Proterozoic rifting of the North American continent included: (a) formation of normal faults and down-dropped basins. (b) eruption of flood basalts. (c) filling of basins with coarse sediment (d) all of the above. 17) Basalts of the mid-continent rift contain a lot of: (a) gold. (b) copper. (c) silver. (d) diamonds. 18) Late Proterozoic completion of a Wilson cycle resulted in the formation of: (a) Pangaea. (b) Rodinia.. (c) Lauria (d) Pannotia. 19) The Earth’s first atmosphere was primarily composed of: (a) water vapor and carbon dioxide. (b) carbon monoxide and sulfur dioxide. (c) neon and oxygen. (d) hydrogen and helium. 20) Prior to differentiation, the Earth’s first atmosphere was removed by the: (a) volcanic activity at the surface. (b) Earth’s magnetic field. (c) the Sun’s radiation pressure, i.e. the solar wind. (d) action of plate tectonics. 21) Earth’s first permanent atmosphere was mostly formed by: (a) the Earth’s magnetic field. (b) volcanic outgassing. (c) the Sun’s radiation pressure. (d) asteroid collision. 22) The Earth’s oceans were formed by: (a) comet impacts. (b) volcano outgassing. (c) probably both of the above 23) All of the following processes are enhanced by the presence of water EXCEPT: (a) the weathering of surface rocks. YES (b) the accelerated rate of sea-floor spreading. ? (c) the formation of continental crust over subduction zones YES Erosion moves sediment (d) the salinity of the oceans. SURE 24) The present concentration of oxygen in the atmosphere is: (a) 78%. (b) 41%. (c) 31%. (d) 21%. 25) The composition of the first permanent atmosphere was much like that of present day: (a) volcanic gases. (b) air. (c) swamp gases. (d) Mars. 26) The oldest fossils formed laminated structures called: (a) reefs. (b) crinoids (c) stromatolites. (d) varves.