ANSWERS TO “TEST YOUR KNOWLEDGE” ON PAGE 36 Answers:
1. The answer is choice “a” or “arkose”. The vast abundance of feldspars is indicative of arkose sandstone (see diagram to the right, based on Folk’s classification). Note that arenites are dominated by quartz grains and litharenites have a mixture of rock fragments (lithics) and quartz with little feldspar, in comparison.
2. The answer is choice “a” or “illite.” Smectite is also a 2:1 structure but the bonding is much weaker,
as oxygen atoms of each sheet are opposite to one another and only secondary bonds exist. Thus, in smectite, water and cations can move between the units and force them apart. Diagnostic x-ray peaks occur at about 14-15 and 9.5 angstroms for air-dried samples. X-ray peaks for samples saturated with ethylene glycol occur at about 17.5 and 9.9 angstroms.
In kaolinite, we have a 1:1 structure consisting of one silicon
tetrahedron and one aluminum octahedron where the units are held by hydrogen bonding and where diagnostic x-ray peaks occur at about 7.2, 3.57 and 2.33 angstroms.
3. The answer is choice “c” or “work hardening.”
In ductile behavior, rocks experience large amounts of plastic deformation before rupture. In brittle behavior, elastic deformation is followed by rupture.
4. The answer is choice “b” or “toarcian” which belongs to the Jurassic Period.
5. The answer is choice “c” or “67,000 mph.” The proof follows:
traveled by the Earth around the Sun in one year is: D1yr In hours, equation (1) becomes: D1yr = 939,966,720/[(365)(24)] = 107,302 km/hr
(2)
Since 1 km = 0.625 miles, equation (2) may be written as: D1yr = (107,302)(0.625) = 67,064 mph
(3)
Equation (3) is the answer that we seek. The Earth then travels around the Sun at a speed of about 1,000 times greater than an average highway speed of 67 mph! Hold on to your hats and hang on!
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