This set of Engineering Geology Multiple Choice Questions & Answers (MCQs) focuses on “Geological Work of Atmosphere-01”.
1. Which of the following about weathering is not true?
a) It is a natural process
b) Mechanical disintegration is involved
c) Chemical decomposition is involved
d) It is a rapid process
Explanation: Weathering is defined as, a natural process of in-situ mechanical disintegration and or chemical decomposition of the rocks of the crust of the Earth by certain physical and chemical agencies of the atmosphere. It is a very slow process.
2. The process that is not considered under mechanical weathering is _______
b) Temperature variation
Explanation: Carbonation is a chemical weathering process whereas the rest viz., temperature variation, unloading, insolation are processes of mechanical weathering.
3. What is the change in volume when water freezes?
a) 10% decrease
b) 20% increase
c) 20% decrease
d) 10% increase
Explanation: It is said that, water on freezing undergoes an increase in its volume by about ten per cent. This is expansion is accompanied by exertion of pressure.
4. The form of rock not found by freezing-thawing cycle is ________
b) Sub angular
Explanation: The frost formed fragments are angular, sub angular, irregular in outline and remain spread over the parent rock having flat surface or flat slopes. Spherical form or outline of rock doesn’t come into picture here.
5. The processes by which Scree deposits are formed are
a) Chemical attack
b) Exposure to sunlight
c) Water movement
d) Heaving and rolling
Explanation: If the original surface forms a significant slope, as is commonly the case in the hilly and mountainous regions, the frost fragments get heaved up from the crevices and cavities and then roll down the slope under the influence of gravity. Finally, the fragments accumulate at the base as heaps commonly called as Scree deposits.
6. What are the slopes covered by Scree called?
a) Scree slope
b) Frost slope
c) Talus slope
d) Trist slope
Explanation: The slopes covered by frost formed scree are often referred to as Talus slopes.
7. Where can one find the process of exudation occur?
Explanation: Exudation is a process similar to frost action but in this case disintegration takes place due to the formation of sodium chloride etc., within the cavities of rocks thereby causing disintegration. This process is seen in good measure in porous rocks near seashore.
8. The stress developed in the top layers of the rocks which disintegrate due to repeated variations in temperatures is________
a) Tensile stress
b) Compressive stress
c) Shear stress
d) Bending stress
Explanation: Repeated variations in temperature experienced by a body of rock gradually break it into smaller pieces, especially in the top layers, by development of tensile stresses developing from alternate expansion and contraction.
9. Which of the following facts about Exfoliation is false?
a) It is the phenomenon of peeling off of curved shells from rocks
b) The change is accompanied by chemical weathering
c) Internal structure of the rock is affected
d) It occurs in thick or layered rocks.
Explanation: The internal structure of the rock is not affected due to the process of exfoliation. The phenomenon of peeling off occurs only in the layered or thick rocks and is accompanied by chemical weathering, mostly near the margins and develop curved surfaces. So basically surface is affected and not the internal structure.
10. The large-scale development of fracturing in confined rock masses occurs under which process?
a) Frost action
11. The formation of sheets and subsequently joints occurs in which of the following processes?
a) Frost action
c) Flow of water
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.
12. Scree deposits can occur in hilly regions only. State true or false.
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.
Explanation: The part labelled is the parent rock and is yet to undergo weathering. It is the solid rock mass and the other parts above and beside the parent rock are called the weathered rocks.
14. 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
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.
Sanfoundry Global Education & Learning Series – Engineering Geology.
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