REVIEW QUESTIONS FOR EXAM 2

Note: correct answers to multiple choice questions are underlined

1.  True or false:  a strong (statistically significant) correlation proves that a cause and
     effect relationship exists.

     False: it is possible for two variables to be correlated without one variable
     being the cause of the other.
 

2.  What can be done to counteract land subsidence over oil and natural gas fields?

      a.  Remove buildings from the area affected by subsidence. 
      b.  Construct recharge basins to collect surface water runoff.
      c.  Only pump oil wells during the summer when recharge rates are high.
      d.  Inject water into the reservoir formation as oil is pumped out.
      e.  Nothing can be done.
 

3.  One reason some scientists question the hypothesis that increasing CO₂  levels in the
       atmosphere are causing global warming is that:

        a.  the greenhouse model has not been adequately tested, and there are
             other potential causes of global warming.
        b.  atmospheric CO₂ and air temperature may be coincidentally correlated.
        c.  this hypothesis is based on anecdotal evidence.
        d.  this hypothesis is based on circumstantial evidence.
        e.  atmospheric CO₂ and air temperature are not correlated. 
 

4.  Taku Glacier in Alaska has been advancing ever since observations of its margin were
     made in 1890.  An observer concludes that the earth's climate is cooling.  Is this a valid
     conclusion?  Why or why not?

       No: the behavior of this glacier is not representative of how the majority of
       glaciers worldwide are behaving.  This observation falls into the category of
       anecdotal evidence; and the explanation for why Taku Glacier is advancing
       though most glaciers are retreating involves an understanding of how cause
       and effect relationships sometimes involve multiple factors.   
 

5.  Why does a threshold sometimes obscure cause and effect relationships?

        A threshold means that some minimum value or condition is required for
        the given relationship to be apparent.  Therefore, until that threshold is
        exceeded, it will not be possible to see that the relationship exists.  For
        example, the relationship between slope angle and landslide velocity will
        not be apparent until a minimum slope angle occurs. 


6.  For what type of data distribution is the "average" (or mean) value a good measure of  
     the "norm"?

       a.  A normal distribution.
       b.  A skewed distribution.
       c.  A distribution with high variance.
       d.  A uniform distribution.
       e.  All of the above. 
 

7.   If you rolled a die 1000 times, your "average roll" would be close to 3.5.  Why is this a
      meaningless average?

       a.  You could never actually roll a 3.5.
       b.  The numbers rolled with a die are not normally distributed.
       c.  It does not represent the population of values very well.
       d.  All of the above are true.
       e.  None of the above are true.
 

8.  What is the chance of rolling a six with one die? 

      a.  one in six, which is a 16.7% chance.
      b.  one in six divided by six, which is a 2.8% chance.
      c.  one minus (1 - 0.166)⁶, which is a 66.5% chance.
      d.  one in six multiplied by six, which is a 99.6% chance.
      e.  less than one in six.
 

9.  You have just rolled two sixes in a row.  What is the chance of rolling a six with
     your third roll? 

      a.  one in six, which is a 16.7% chance.
      b.  one in six divided by three, which is a 5.6% chance.
      c.  one minus (1 - 0.166)³, which is a 57.8% chance.
      d.  one in six multiplied by three, which is a 50.0% chance.
      e.  less than one in six.
 

10.  What is the chance of rolling at least one six with six die rolled at the same time? 

      a.  one in six, which is a 16.7% chance.
      b.  one in six divided by six, which is a 2.8% chance.
      c.  one minus (1 - 0.166)⁶, which is a 66.5% chance.
      d.  on in six multiplied by six, which is a 99.6% chance.
      e.  less than one in six.
 

11.  What makes a process or an event random? 
  
       The occurrence of a random process or event cannot be predicted.  We can
       only make probability forecasts based on the recurrence interval.

12.  Which geologic process(es) is (are) closest to being truly random?

       Floods.

13.  When the recurrence interval of a given event is said to be 100 years:

       a.  the event occurs, on the average, every 100 years.
       b.  the event could occur two or even three years in a row.
       c.  the time interval between events might never actually be 100 years.
       d.  the time intervals between events might cluster around 100 years or
            range from 1 to 500 years.
       e.  all of the above.
 

14.  The location of initial movement along a fault during an earthquake is called: 

        a.  the focus.
        b.  the epicenter.
        c.  ground zero.
        d.  the shock center.
        e.  the seismogram.
 

15.  The dilatancy that sometimes precedes earthquakes and causes land surface elevations
       to rise along an fault zone:

       a.  has now been shown to not occur prior to earthquakes in California.
       b.  explains why earthquakes often precede volcanic eruptions.
       c.  does not occur when rocks within the fault zone deform as predicted by the
            elastic rebound theory .
       d.  might explain why some animals sense that a large earthquake is imminent.
       e.  none of the above.
 

16.  True or false: earthquake lights are caused by stress release during an earthquake.

       False - earthquake lights precede earthquakes.
 

17.  True or false: a seismic gap is place along an active fault zone where earthquakes
       do not occur.

       False - seismic gaps are places where large earthquakes are likely to occur. 
 

18.  True or false: foreshocks and aftershocks are caused by the same process.

        True - both are the result of strain release along a fault.
 

19.  True or false: fault creep is the gradual build up of strain that leads to a
       large earthquake. 

       False - fault creep is the continual release of strain, resulting in small earthquakes
       and gradual displacement.
 

20.  True or false:  most earthquakes occur along lithospheric plate boundaries.

       True.

21.  True or false:  large earthquakes only occur along plate boundaries. 

        False.

22.  True or false:  when an earthquake occurs along the San Andreas Fault, only one,
       relatively small segment of the fault actually moves.

       True.

23.  Why is it easier to forecast earthquakes along the San Andreas Fault in California
       than along the New Madrid Fault in Missouri?

       Because we don't know the recurrence interval of earthquakes along the New Madrid
       Fault, nor do we know the rate at which strain is building up.