The Precambrian Earth

Practice Test
      
  1.What is the name of the Precambrian shield in North America?  
  a.   the Northern Shield  
  b.   the Proterozoic Shield  
  c.   the Archean Shield  
  d.   the Canadian Shield  
      
  2.What substance in Earth's atmosphere protects organisms from UV radiation?  
  a.   methane  
  b.   ammonia  
  c.   ozone  
  d.   water vapor  
      
  3.The oldest rocks on Earth are __________.  
  a.   3.96 to 3.8 billion years old  
  b.   1.6 to 1.8 million years old  
  c.   3.5 billion years old  
  d.   1 to 2 billion years old  
      
  4.What process is primarily responsible for the formation of Earth's oceans?  
  a.   outgassing  
  b.   sea-floor spreading  
  c.   evolution  
  d.   plate tectonics  
      
  5.Why is the age of a zircon grain older than the age of the sandstone that it was found in?  
  a.   because of the principle of superposition  
  b.   It is much more stable than the sandstone.  
  c.   It is much less stable than the sandstone.  
  d.   because of the principle of included fragments  
      
  6.What supercontinent is shown in the figure?



  
  a.   Laurentia  
  b.   Gondwana  
  c.   Rodinia  
  d.   Pangaea  
      
  7.Minerals with low densities crystallize from a magma at __________ denser minerals do.  
  a.   the same temperature as  
  b.   hotter temperatures than  
  c.   cooler temperatures than  
  d.   always 10 degrees less than  
      
  8.The energy and nutrients necessary for the origin of life can be found near __________.  
  a.   magma chambers  
  b.   trenches  
  c.   hydrothermal vents  
  d.   transform faults  
      
  9.__________ are the building blocks of proteins.  
  a.   Formaldehyde molecules  
  b.   Amino acids  
  c.   DNA and RNA  
  d.   Cyanide molecules  
      
  10.What evidence supports the hypothesis that Earth is 4.6 billion years?  
  a.   the age of meteorites  
  b.   the age of rocks from the Moon  
  c.   the age of zircon grains in granitic crustal rocks  
  d.   all of the above answers are correct  
      
  11.According to the dates given in the table, when would oxygen start appearing in Earth's atmosphere?

Event Or First Evidence In Fossil Record Approximate Geological Time
Bacteria 3 b.y.b.p
Green algae 1 b.y.b.p
Jellyfish 600 m.y.b.p
Ediacara organisms 550 m.y.b.p
Eurypterids* 510 m.y.b.p
Horn corals* 500 m.y.b.p
First vertebrates 480 m.y.b.p
Spiders 400 m.y.b.p
Sharks

 400 m.y.b.p
First jawed fish* 380 m.y.b.p
Ferns 350 m.y.b.p
Earthworms 300 m.y.b.p
Great Permian Extinction Event

250 m.y.b.p
Drastic geographic and climatic changes 248 m.y.b.p
First dinosaurs* 220 m.y.b.p
First mammals 210 m.y.b.p
Ginkgo biloba 200 m.y.b.p
Abundant ammonites* 180 m.y.b.p
Archaeopteryx* 140 m.y.b.p
First flowering plants 120 m.y.b.p
Ants 100 m.y.b.p
Cretaceous-Paleogene Extinction Event 66 m.y.b.p
Camel 35 m.y.b.p
Grass 20 m.y.b.p
Australopithecus afarensis (“Lucy”) 4 m.y.b.p


 
  a.   550 million years go  
  b.   600 million years ago  
  c.   1 billion years ago  
  d.   3 billion years ago  
      
  12.What were the type of life-forms that existed before the Proterozoic?  
  a.   eukaryotes  
  b.   prokaryotes  
  c.   fungi  
  d.   algae  
      
  13.Why don't Archean and Proterozoic rocks have iron oxides?  
  a.   there weren't any stromatolites at that time  
  b.   there wasn't any free oxygen in the atmosphere  
  c.   there wasn't any iron in rocks of that age  
  d.   there was too much iron to be oxidized  
      
  14.What did organisms of Earth's first 4 billion years have in common?  
  a.   They were single-celled organisms.  
  b.   They were multi-celled organisms.  
  c.   They breathed oxygen.  
  d.   They were photosynthetic.  
      
  15.What was the original composition of Earth's atmosphere?  
  a.   hydrogen and helium  
  b.   water vapor and methane  
  c.   nitrogen and carbon dioxide  
  d.   ammonia and hydrogen  
      
  16.How were asteroids and meteorites a heat source for Precambrian Earth?  
  a.   Their gravitational contraction generated energy.  
  b.   Their radioactive decay of isotopes generated energy.  
  c.   Their bombardment of Earth caused them to sink to the core.  
  d.   Their impact on Earth generated energy.  
      
  17.What continent existed around 1.8 billion years ago that now forms the core of modern North America?  
  a.   Rodinia  
  b.   Laurentia  
  c.   Pangaea  
  d.   North America  
      
  18.What event caused the extinction of acritarchs near the end of the Proterozoic?  
  a.   global warming  
  b.   the Varagnian glaciation  
  c.   formation of ozone  
  d.   outgassing  

 
   
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