ANSWERS TO “TEST YOUR KNOWLEDGE” ON PAGE 38 Answers:
1. The answer is choice“c” or “A knife-edged ridge connect- ing two or more peaks and separating adjoining cirques.” Choice “a”best refers to a drumlin and choice “b”defines an esker.
2. The answer is choice “c” or “brachiopods.” In pelecypods, the shells are located on the left and right sides of the mol- lusk. Theropods are not bivalves, but an order of dinosaurs characterized by hollow bones and three-toed limbs.
3. The answer is choice “c” or “porosity.” Void ratio is the volume of the voids divided by the volume of the solids. Water saturation is the volume of the water divided by the volume of the voids.
4. The answer is choice “b” or “false.” Silica content is directly proportional to viscosity.
5. The answer is choice “b” or (2C/γ) * NØ1/2; the proof now follows. From the information given, we may write: Pv = γZ
Pv = Ph NØ + 2C NØ1/2 γZ = Ph NØ + 2C NØ1/2 Ph NØ = γZ - 2C NØ1/2 Ph = (γZ/ NØ) - 2C NØ-1/2
At the surface, Z = 0 and (5) becomes: Ph = - 2C NØ-1/2
(1) (2) (3) (4) (5)
(6)
Note that Ph in (6) represents a tensile stress. To find the depth Zo where Ph = 0, we rewrite (5) as follows and solve for depth: 0 = (γZ/ NØ) - 2C NØ-1/2 (γZ/ NØ) = 2C NØ-1/2 Z = Zo = (2C/γ) * NØ1/2
(7) (8) (9)
Equation (9) is the answer to our question. At depths greater than Zo, the value of Ph represents a compressive stress.
Geologic Ethics & Professional Practices is now available on CD
This CD is a collection of articles, columns, letters to the editor, and other material addressing professional ethics and general issues of professional geologic practice that were printed in The Professional Geologist. It includes an electronic version of the now out-of-print Geologic Ethics and Professional Practices 1987-1997, AIPG Reprint Series #1. The intent of this CD is collection of this material in a single place so that the issues and questions raised by the material may be more conveniently studied. The intended ‘students’ of this CD include everyone interested in the topic, from the new student of geology to professors emeritus, working geologists, retired geologists, and those inter- ested in the geologic profession.
AIPG members will be able to update their copy of this CD by regularly downloading
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www.aipg.org under “Ethics” and by downloading the electronic version of The Professional Geologist from the members only area of the AIPG website. The cost of the CD is $25 for members, $35 for non-members, $15 for student members and $18 for non-member students, plus shipping and handling. To order go to
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40 TPG •
Apr.May.Jun 2019
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