How can extensional faults form in a thrust-and-fold belt?
What will be an ideal response?
Answer: They can form where contraction thickens the nappe stack or wedge so that it collapses under its own weight. It does so by extending laterally through the formation of normal faults. Such overthickening can occur where a nappe is ripped off the basement and incorporated into the wedge as shown in Figure 16.13 and 16.25b. Lowering the basal friction could also create normal faulting in the overlying orogenic wedge.
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Storms can compound problems related to hypoxia by
A) driving saltwater into freshwater ecosystems, killing the fish and causing them to decompose. B) leaving behind debris that inhibits photosynthesis of the remaining living plants and phytoplankton. C) increasing the production of hydrogen sulfide and tannic acid as a by-product of the decomposition process. D) All of these cause hypoxia in the aftermath of a storm.
Which of these mineral assemblages is characteristic of a greenschist facies?
A) Potassium feldspar, biotite, and quartz B) Chlorite, epidote, and serpentine C) Hornblende D) Quartz and muscovite
Carbonic acid forms when carbon dioxide reacts with rainwater.
Answer the following statement true (T) or false (F)
Judge the following sentence according to the criteria given below:
The dramatic and rapid climate change that is occurring on our planet cannot be explained by variations in the eccentricity of Earth's orbit BECAUSE this variation has a cycle of about 100,000 years. A) The assertion and the reason are both correct, and the reason is valid. B) The assertion and the reason are both correct, but the reason is invalid. C) The assertion is correct, but the reason is incorrect. D) The assertion is incorrect, but the reason is correct. E) Both the assertion and the reason are incorrect.