WVGES, Geoscience Education in the Mountain State:
CATS Environmental Geochemistry Telecourse, Spring 2002
Quiz #1
Due date is March 25.


Quiz Instructions:

You may submit your quiz answers using one of the following methods. (Regardless of the method you use, don't forget to include your name. Please keep a copy of your answers; this applies to all methods of submission.)

  1. fax to Dr. Bob Behling: 
          fax number:       304-293-6522
  2. regular mail to Dr. Bob Behling postmarked no later than the quiz due date: 
             address:  Department of Geology and Geography
                   West Virginia University
                   P.O. Box 6300
                   Morgantown, WV  26506-6300

  3. electronically:
    Please read and follow the instructions shown below to submit your answers electronically.

QUIZ #1 :

  1. (+6) There are many critical rock-forming minerals that demonstrate significant substitutions of elements in mineral structure. Sometimes, the substitution occurs well after sediments have formed (called a diagenetic change) as in the case of the rock dolostone. Limestone is the calcium carbonate: the mineral is calcite. In dolostone, one-half of the Ca ions in the structure are replaced by Mg. The mineral is dolomite, and we designate it as a (Ca, Mg) carbonate. Are Ca and Mg that close in the periodic table to suggest this exchange possibility? (+3)

    In the Plagioclase Feldspar family, the elements are Ca, Na, Al, Si, and O. Using the periodic table, predict which elements substitute for each other in the structure so that the equations can balance with respect to valence. Hint: there are eight Oxygen atoms in the equation; and the ratio of Si (and any other element that might substitute for Si) and Oxygen is Si:O=4:8 (+3). There is always a cation, Al, Si, and of course, O, in every feldspar.

  2. (+4) There is some exchange of K for Na in the feldspars Orthoclase (the potassium feldspar) and Albite (the pure sodium feldspar). What is so similar about K and Na that substitution seems to be intuitively clear as a possibility? (+2) What is so dissimilar about K and Na that complete substitution ranges between 100% Na and 100% K are intuitively prohibited? Hint: think of a physical limitation! (+2)

  3. (+3) In the mineral family the Olivine Family, Fe and Mg are the key elements that substitute for each other. There is 100% substitution: from pure Fe-Si-O to pure Mg-Si-O mineral composition. (Realize, of course, that these equations have not been balanced.) Does the periodic table clearly show why this should be such a perfect match: Fe + 2 and Mg + 2?

  4. (+3) Consider the family of minerals known as the Chlorides. The sodium chloride is quite common; the other mineral, Sylvite, is a potassium chloride. Predict the chemical equation of Sylvite and suggest the bonding you would expect to be present in Sylvite.

  5. (+6) Examine Figure 5.6 in your text. Explain why ice is less dense than liquid water. (+4) Explain why the pressure of a person on skates or the conditions at the base of a glacier exists such that there is pressure melting! Basalt melts when pressure is released. Water melts when pressure is added.

  6. (+3) Shells of marine invertebrates are brought up from a core drilled off the Florida Keys. The critters at depth (all of this drilling is on the shelf, not in the deepest ocean depths) have calcium carbonate shells. The oxygen isotope analysis shows a definite trend: there is more O-18 isotope in the shells found. What does this suggest about the climate when these critters were alive and making shell material? Explain all your assumptions.

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Page last revised: March 6, 2002