DSST Physical Geology Practice Questions Answer Key
1. B: It is true that rocks are classified by their formation and the minerals they contain, while minerals are classified by their chemical composition and physical properties. Answer A is incorrect because rocks may contain traces of organic compounds. Answers C and D are incorrect because only minerals can be polymorphs and only rocks contain mineraloids.
2. C: On Mohs scale of mineral hardness, talc has the lowest possible score (a one). Diamond is a ten, which is the highest possible score, and gypsum and fluorite have a score of two and four, respectively. Minerals can always scratch minerals that have a Mohs score lower than their own.
4. C: Minerals that form on the sea floor from discarded shells are most likely part of the carbonate class. Minerals that form in karst regions and evaporitic settings may also be carbonates. Examples of minerals in the carbonate class include aragonite, dolomite, calcite, and siderite.
5. C: When salt water penetrates fractures in rocks and leaves behind salt crystals that cause the rock to fracture, it is considered physical rather than chemical weathering. Chemical weathering involves changes in the molecules that comprise the rocks, while physical weathering occurs when external factors act on the rock without changing its chemical composition in any way.
6. C: Leaching in the “A” soil horizon results from contact with acid solutions generated in the “O” horizon, which is the uppermost organic layer of soil. Cations that are leached in the A” soil horizon accumulate in the “B” soil horizon below.
7. A: When metamorphic rock is stressed unevenly during recrystallization, it can result in foliation. Foliation is characterized by banded rock, and it occurs when certain types of minerals are reoriented during recrystallization due to uneven shortening or compression of the rock.
8. D: Regional metamorphism occurs when a large area of rock is subjected to intense heat and pressure, while contact metamorphism occurs when magma is injected into surrounding rock, also known as country rock. When contact metamorphism occurs, the rocks closest to the hot magma undergo the greatest changes.
9. A: When two tectonic plates are moving laterally in opposing directions, this is called a transform boundary. When there is friction at transform boundaries and pressure builds up, it can result in shallow earthquakes (usually at a depth of less than 25 meters). California’s San Andreas Fault is an example of a transform boundary.
10. A: An earthquake with a Richter magnitude of 1.5 will probably not be felt, and will not cause any damage. Earthquakes with magnitudes of less than 2.0 are usually not felt, and those with magnitudes of less than 5.0 typically do not seriously damage well-constructed buildings. Earthquakes with magnitudes of 6.0 or greater can cause damage to even well-constructed buildings.