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Practice Test
  1.What two factors control the explosiveness of an eruption?  
  a.   the pressure within Earth and plate movement  
  b.   the amount of gases and pressure within Earth's crust  
  c.   the amount of water vapor and silica in the magma  
  d.   the time of year and current weather conditions  
  2.A volcanic neck is the remains of a(n) ___________.  
  a.   magma flow  
  b.   active volcano  
  c.   intrusive igneous rock  
  d.   eroded volcano  
  3.What is the difference between a dike and a sill?  
  a.   Dikes are formed across vertical cracks, and sills are formed across horizontal ones.  
  b.   They form in the same direction, but are of different sizes.  
  c.   They form in the same direction, but they are created differently.  
  d.   Dikes are formed across horizontal cracks, and sills are formed across vertical ones.  
  4.Of the three types of volcanoes, which is the least explosive?  
  a.   They all have the same level of explosiveness.  
  b.   cinder volcanoes  
  c.   composite volcanoes  
  d.   shield volcanoes  
  5.The difference between basaltic and granitic magma is __________.  
  a.   the color  
  b.   the amount of water vapor  
  c.   the way it cools  
  d.   the amount of silica  
  6.Intrusive igneous rocks are those which __________.  
  a.   cool on Earth's surface  
  b.   changed over time from one type of rock to another  
  c.   are composed of sediments found in flood beds  
  d.   cool beneath Earth's surface  
  7.High levels of silica causes magma to become __________.  
  a.   more fluid  
  b.   less dense  
  c.   thinner  
  d.   thicker  
  8.Convergent plate boundaries __________.  
  a.   create volcanoes that are not as violent as others  
  b.   spread apart Earth's surface  
  c.   don't produce volcanoes  
  d.   force one plate beneath Earth's surface  
  9.What is the difference between lava and magma?  
  a.   They are made of different types of rock.  
  b.   They originate from different places.  
  c.   They are different colors.  
  d.   After magma reaches the surface it's called lava.  
  10.What are batholiths?  
  a.   magma bodies that cool quickly before they reach Earth's surface  
  b.   hot magma flows that cool quickly before they reach Earth's surface  
  c.   hot magma flows that cool slowly before they reach Earth's surface  
  d.   magma bodies that cool slowly before they reach Earth's surface  
  11.Volcanoes often are found in areas on Earth where __________.  
  a.   plates fit together perfectly  
  b.   mountains are found  
  c.   plates collide  
  d.   rivers are found  
  12.What is a vent?  
  a.   the opening in a volcano  
  b.   the remains of an eroded volcano  
  c.   the steep depression around a volcano's opening  
  d.   a small fissure on the side of a volcano  
  13.Sulfurous gases emitted by volcanoes __________.  
  a.   are good for the environment  
  b.   help plants grow  
  c.   are contained totally within lava flows  
  d.   can mix with water vapor and form acid rain  
  14.Granitic magma eruptions are  
  a.   slow  
  b.   fluid  
  c.   explosive  
  d.   quiet  
  15.Shield volcanoes are the result of __________.  
  a.   basaltic lava flows  
  b.   granitic lava flows  
  c.   andesitic lava flows  
  d.   basaltic and andesitic lava flows  
  16.Islands like Iceland are often formed due to __________.  
  a.   all answers are correct  
  b.   rifts in the Earth's surface  
  c.   plate movement  
  d.   cooling lava flows  
  17.Calderas form __________.  
  a.   continually  
  b.   after an eruption  
  c.   before an eruption  
  d.   during an eruption  
  18.Cinder cone volcanic eruptions are ___________.  
  a.   gradual and pour lava over the edges, which collects in pools  
  b.   gradual and pour tephra over the edges  
  c.   slow and occur over long periods of time  
  d.   explosive and throw lava high into the air  
  19.What causes magma to rise to the surface?  
  a.   The rock forces the magma upward.  
  b.   A force pulls the magma upward.  
  c.   Magma is more dense than rock.  
  d.   Magma is less dense than rock.  
  20.Magma originates in which layer of Earth?  
  a.   mantle  
  b.   crust  
  c.   inner core  
  d.   core  

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