# Engineering Geology Questions and Answers – Classification of Folds – 02

This set of Engineering Geology Questions and Answers for Freshers focuses on “Classification of Folds – 02”.

1. Pick the wrong statement about recumbent fold.
a) It has the arch, which is zone of curvature
b) It has the shell, which is the inner zone, made up of mostly igneous rocks
c) It has the shell, which is the outer zone, made up of mostly sedimentary rocks
d) It has the core, which is the innermost zone, maybe made up of igneous rocks and metamorphic rocks

Explanation: The shell part of a recumbent, which is the outer zone, is mostly made up of sedimentary rocks. Hence the second statement is wrong regarding it.

2. The type of fold which is actually a group of folds is ____________
a) Symmetrical folds
b) Asymmetrical folds
c) Isoclinal folds
d) Recumbent folds

Explanation: Isoclinal folds are group of folds in which all the axial planes are essentially parallel, meaning that all the component limbs are at equal amounts.

3. There are three types of folds classified on the basis of relative curvature of the outer and the inner arcs of a fold.
a) True
b) False

Explanation: Ramsay divides all types of folds into three main classes on the basis of relative curvature of the outer and the inner arcs of a fold. They are Class 1, Class 2 and Class 3 folds.

4. In which class of folds, the Isogans converge inwards?
a) Class 1
b) Class 2
c) Class 3
d) Class 4

Explanation: Determination of dips may be made and then lines of equal dips are drawn. These are called Isogans. In Class 1 folds, the Isogans converge inwards.

5. Identify the class to which the fold below belongs to ___________

a) Class 1
b) Class 2
c) Class 3
d) Class 4

Explanation: In class 2 folds, the isogans would run parallel to each other and hence the fold shown in the figure belongs class 2.
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6. Which is the type of fold with a similar degree of folding for indefinite depths?
a) Concentric fold
b) Similar fold
c) Conjugate fold
d) Uniform fold

Explanation: Similar folds are the folds in which the degree of folding is observed to be similar for indefinite depths.

7. A fold can have differences in thickness due to erosional and depositional processes.
a) False
b) True

Explanation: Supratenuous folds show differences in thickness at the crestal and the trough regions, not induced by folding process but essentially due to erosional and depositional processes operating in the folded regions.

8. Gentle folds have fold angle between ___________
a) 10° to 90°
b) 90° to 170°
c) 170° to 180°
d) They don’t belong to this type

Explanation: For the classification of folds on the basis of fold angle, a fold is said to be gentle fold if the fold angle is between 170° to 180°.

9. Which is the class of fold with the degree of curvature greater on the outer arc compared to the inner arc?
a) Class 1
b) Class 2
c) Class 3
d) Class 4

Explanation: Class 3 folds are just the reverse of class 1 folds; in these folds, the degree of curvature as measured on the outer arc is greater than that of the inner arc.

10. The fold which is associated with the formation of mountains is ___________
a) Geanticline
b) Geosyncline
c) Homocline
d) Basin

Explanation: Great importance is attached to the major depressions, the geosynclines, in the process of mountain building.

11. The anticlines signifying larger bending are called ___________
a) Geranticlines
b) Geosynclines
c) Geanticlines
d) Geoantinclines

Explanation: The anticlines which signify larger bending and uplifting of strata on sub-continental scales are expressed by the term Geanticlines.

12. The folds caused due to the drag effect are ___________
a) Monocline
b) Homocline
c) Basins
d) Drag folds

Explanation: Drag folds derive their name from the cause of origin; they develop due to the drag effect suffered by the soft and ductile type material of the incompetent rock.

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