ANSWERS TO QUESTIONS ON PAGE 29
Answers: 1. The answer is choice “b” or “KAlSi3O8” or “potassium feldspar.” Potassium feldspar (orthoclase/microcline) is an expected and common component of felsic or acidic igneous rocks that typically forms during “late stages of magmatic crystallization.”
Choices (a) and (c) represent “calcium plagioclase” (anorthite) and “olivine” (forsterite/fayalite), respectively. Both of these minerals are likely to be present in mafic volcanic and plutonic igneous rocks and to appear during the “early stages of magmatic crystallization.”
2. The answer is choice “a” or “regolith.”
As stated, “regolith” is the layer of broken rock, soil, dust and other material that covers solid rock. “Soil” is, thus, part of the “regolith.” The term “soil;” however, may be reserved to describe the portion of the “regolith” that supports plant life. In soil mechanics and for engineering purposes, “soil” is usually defined as an aggregate of mineral particles that covers consolidated or solid bedrock.
“Coccoliths” are minute plates or rings, composed of calcium carbonate, which make up the external covering of some marine phytoplankton. In particular, “coccoliths” involve “haptophyte phytoplankton,” or a division of algae. In a fossilized state, “coccoliths” may form “chalk” and other calcareous lithologies.
“Xenoliths” are rock fragments which are trapped or enveloped within another rock. “Xenoliths” describe lithologic inclu- sions in igneous rocks that are incorporated during magmatic emplacement and during volcanic eruptions.
3. The answer is choice “c” or “diastem.”
“Diatremes” are volcanic pipes or vents that cut across enclosing strata and which are propelled by the explosive energy associated with gas-charged magmas.
“Diapirs” are piercement structures or a type of intrusion in which a more ductile and mobile type of strata (like salt) is injected into the more brittle overlying layers.
4. The answer is choice “c” or “$36,924.80.” The proof follows: We are given:
g-3
3
3-4 ft3
) x (V) Substituting (1), (5), (2) and (6) into (7), we obtain:
-3-4) ft3] (8) Thus, from (3) and (9) we calculate:
g$
Equation (10) provides us with the answer we seek. Really, it would have been much easier to weigh the nugget on an accurate balance scale, right? But wow, what a find! Let’s go party!
5. The answer is choice “b” or “54.” The proof follows:
Recall that the “scalar triple product” of three vectors equals the volume of a parallelepiped where the vectors comprise the adjacent edges. Thus:
The volume is, thus, “54” corresponding to our choice “b” in the question. The minus sign in equation (2) simply indicates that, in this case, the vectors form a left-handed triple. Simple enough, eh?
(1) (2)
To solve this problem, we must ensure that all units are compatible. We also know that:
(6) (7)
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