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Practice Questions for Chapter 20
Geology 1200
Use these questions to test your knowledge of Chapter 20. 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 Precambrian rocks of the Canadian Shield were originally correlated on the basis of:
(a) volcanic ash beds.
(b) sedimentary structures.
(c) fossils.
(d) severity of deformation. (why is this actually a pretty good idea?)
3) Which of the following is NOT true concerning the Eons of the Precambrian?
(a) Their rocks are impossible to correlate by any means.
(b) Their intervals were based upon similarities in tectonic activity and rock composition.
(c) The oldest interval was defined last.
4) The one location where Hadean rocks may still exist is the:
(a) the continental interior.
(b) the ocean floor.
(c) the continental margins.
(d) the subsurface.
5) Information concerning the origin of the Moon has come primarily from:
(a) moon rocks.
(b) astronomical observations.
(c) telescopic observations.
(d) seismological observations.
6) The main difference between the Earth and the Moon is in:
(a) their different overall densities.
(b) their chemical compositions.
(c) the size of their metallic cores.
(d) All of the above.
7) 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.
8) All of the following must be explained by any acceptable hypothesis of the Moon’s origin
EXCEPT:
a) why the Moon’s orbit is inclined relative to the Earth’s orbit around the Sun.
b) why the Earth and the Moon differ chemically.
c) why the Moon lacks an atmosphere..
d) why the Earth has the greatest overall density of any planet.
9) 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.
10) All of the following events contributed to Earth’s molten ocean EXCEPT:
a) decay of radioactive elements in the planet’s interior.
b) heat generated by the initial accretion.
c) the Earth’s close proximity to the Sun..
d) heat generated by impacts.
11) 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.
12) 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.
13) The most common primary rock association of the Archean crust is:
a) komatiite lava.
b) greenstone belts.
c) granulite-gniess..
d) granite-granodiorite.
14) 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.
15) 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..
16) All of the following are mechanisms for growth of Archean continents EXCEPT:
a) collision of large continents..
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.
17) Which feature of Archean rocks of the Canadian Shield was not considered in their
assignment to distinct crustal provinces?
a) Types of folding.
b) Composition.
c) Fossils..
d) Age.
18) Which sedimentary rock type does NOT characterize Archean sedimentation?
a) Graywacke.
b) Limestone..
c) Chert.
d) Shale.
19) 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%.
20) 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..
21) 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.
22) The Coronation Supergroup was deposited:
a) in small, oceanic rift basins.
b) during the rifting stage of a Wilson cycle.
c) during the drifting stage of a Wilson cycle.
d) All of the above..
23) Which Proterozoic tectonic event was NOT responsible for deformation of the Coronation
Supergroup?
(a) Rifting and drifting stages of the Wilson cycle..
(b) Collision stage of the Wilson cycle.
(c) Westward subduction beneath a volcanic island arc.
(d) Eastward thrusting of sediments over the edge of the Slave craton.
24) The site of the collision stage of the Proterozoic Wilson cycle of Canada is called the:
a) Coronation Supergroup.
b) Slave craton.
c) Wopmay Orogen..
d) None of the above.
25) 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
26) The last major Proterozoic collision before assembly of Rodinia is recorded by rocks in the:
a) Grenville Orogen.. (on field trip)
b) Trans-Hudson Orogen.
c) Mazatal Orogen.
d) Wopmay Orogen
27) All of the following features indicate Late Proterozoic rifting of the North American
continent EXCEPT:
(a) formation of normal faults and down-dropped basins.
(b) eruption of flood basalts.
(c) high-grade metamorphism and granite intrusions..
(d) filling of basins with coarse sediment
28) Basalts of the mid-continent rift contain a lot of:
(a) gold.
(b) copper.
(c) silver.
(d) diamonds.
29) Late Proterozoic completion of a Wilson cycle resulted in the formation of:
(a) Pangaea.
(b) Rodinia..
(c) Prepangaea.
(d) Pannotia.
30) The Earth’s first atmosphere was primarily composed of:
(a) water vapor and carbon dioxide.
(b) carbon monoxide and sulfur dioxide.
(c) nitrogen and oxygen.
(d) hydrogen and helium.
31) 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.
32) Earth’s first permanent atmosphere was formed by:
(a) the Earth’s magnetic field.
(b) volcanic outgassing.
(c) the Sun’s radiation pressure.
(d) asteroid collision.
33) The Earth’s oceans were formed by:
(a) comet impacts.
(b) volcano outgassing.
(c) probably both of the above
34) All of the following processes are enhanced by the presence of water EXCEPT:
(a) the weathering of surface rocks.
(b) the accelerated rate of sea-floor spreading..
(c) the formation of continental crust over subduction zones
(d) the salinity of the oceans.
35) The present concentration of oxygen in the atmosphere is:
(a) 78%.
(b) 41%.
(c) 31%.
(d) 21%.
36) The composition of the first permanent atmosphere was much like that of present day:
(a) volcanic gases.
(b) air.
(c) swamp gases.
(d) Mars.
37) All of the following represent evidence of oxygen deficiency in the Earth’s first atmosphere
EXCEPT: (added notes won't be on test)
(a) sedimentary iron. (no oxygen)
(b) banded iron formations. (oxygen in deep water beginning 3.5 until 2 bya)
(c) redbed sediments.. (atmospheric oxygen available to stream and floodplain sediments 2
bya)
38) All of the following evidence can be used to infer Late Proterozoic glaciation EXCEPT:
(a) widespread Late Proterozoic limestones. (on the field trip; removes CO2 from
atmosphere, diminishing the greenhouse effect)
(b) varved sediments.
(c) tillites.
(d) grooved and striated bedrock.
39) All living things are dependant upon:
(a) DNA or RNA.
(b) proteins.
(c) amino acids.
(d) All of the above.
40) All of the following elements are essential building blocks of organic molecules EXCEPT:
(a) copper.
(b) oxygen.
(c) carbon.
(d) nitrogen.
41) The oldest fossils formed laminated structures called:
(a) reefs.
(b) stromatoporoids.
(c) stromatolites.
(d) varves.
42) All of the following pieces of evidence support endosymbiosis as the origin of eukaryotes
EXCEPT:
(a) mitochondria with DNA.
(b) eukaryotes without organelles..
(c) chloroplasts that divide independently of cells.
(d) double membrane surrounding eukaryotes.
43) The significance of the first trace fossils of crawling animals is that they indicate:
(a) large stromatolites.
(b) large, mobile metazoans.
(c) tiny shell builders.
44) All of the following Late Proterozoic fossils indicate increasing levels of atmospheric
oxygen EXCEPT:
(a) Ediacara fauna.
(b) small shell builders.
(c) stromatolites.. (They help make the oxygen)
(d) trace fossils of crawling animals.
45) All of the following groups are present in Ediacara fauna EXCEPT:
(a) brachiopods..
(b) segmented worm.
(c) arthropod.
(d) jellyfish.
E. Short Answer
1. Where is the most likely location for the Earth’s oldest rocks?
2. For what Eon of the Precambrian is there little or no rock record?
3. Explain why are Archean continents were small.