Engineering Geology Questions and Answers Part-3

1. The large-scale development of fracturing in confined rock masses occurs under which process?
a) Frost action
b) Unloading
c) Unfolding
d) Insolation

Answer: b
Explanation: The process of mechanical weathering where large-scale development of fracturing in confined rock masses is attributed to removal of the overlying rock cover due to prolonged erosional work of other agencies is called unloading.

2. The formation of sheets and subsequently joints occurs in which of the following processes?
a) Frost action
b) Insolation
c) Flow of water
d) Unloading

Answer: d
Explanation: The rock masses under the effect of unloading remain confined from sides but due to relief of pressure from above, they expand upwards; consequently joints develop in them parallel to the uncovered surface dividing them into sheets.

3. Scree deposits can occur in hilly regions only.
a) True
b) False

Answer: a
Explanation: The above statement is true because, for scree deposits to be formed, the rock fragments have to heave up and also roll down the slope under the influence of gravity.

4. In Kara Qum desert, the rocks are exposed to what temperatures in summer and winter respectively?
a) 70-80° C and -10° C
b) 20-30° C and -1° C
c) 40-50° C and 0° C
d) 25-35° C and -3° C

Answer: a
Explanation: Studies have shown that in desert like Kara Qum, rocks are exposed to as high temperatures as 70-80° C in summer and are then cooled down to -10° C in winter. Such repeated variations in temperature experienced by a body of rock gradually break it into smaller pieces.

5. The main processes which does not come under chemical weathering are ____________
a) Solution
b) Hydration and hydrolysis
c) Insolation
d) Carbonation

Answer: c
Explanation: The processes, solution, hydration and hydrolysis, carbonation are all chemical processes and involve chemical reaction, whereas, insolation is a process of mechanical weathering.

6. The rock-mineral insoluble in water is ____________
a) Rock salt
b) Gypsum
c) Calcite
d) Pyrite

Answer: d
Explanation: Pyrite is insoluble in water, whereas, rock salt, gypsum and calcite are examples of minerals that are soluble in water to some extent.

7. Limestone is not easily soluble in pure water but carbonated water dissolves the rock effectively.
a) False
b) True

Answer: b
Explanation: Pure water is not a good solvent of minerals in most cases, but when the water is carbonated, its solvent action for many common minerals is enhanced. Thus, limestone is not easily soluble in pure water but carbonated water dissolves the rock effectively.

8. Minerals like Orthoclase and Felspar undergo which method of chemical decomposition?
a) Hydration
b) Hydrolysis
c) Oxidation
d) Reduction

Answer: b
Explanation: Ions may be exchanged whereby some ions from water may enter into the crystal lattice of the mineral. This process of exchange of ions is called hydrolysis. It is a very common process of weathering of silicate minerals and is best explained with reference to weathering of mineral Orthoclase, Felspar.

9. Which of the following is reduction?
a) Removal of hydrogen
b) Removal of electron
c) Removal of oxygen
d) Addition of oxygen

Answer: c
Explanation: Oxidation means of either removal of electron or hydrogen or addition of oxygen but, reduction may involve removal of oxygen or addition of hydrogen or electron.

10. 2KaISi3O8 + 2H2O + CO2 → Al2Si2O5(OH)4 + K2CO3 + 4SiO2
Orthoclase + Carbonic acid → ___________ + Pot. Carbonate + Silica
Identify the mineral in the blank space of the equation.
a) Illite
b) Kaolinite
c) Montmorillonite
d) Halloysite

Answer: b
Explanation: The reaction of orthoclase with carbonic acid yields kaolinite {Al2Si2O5(OH)4 } and Pot. Carbonate and silica.