Engineering Geology Questions and Answers Part-8

1. The minimum number of limbs for a fold are _____________
a) 1
b) 2
c) 3
d) 4

Answer: b
Explanation: An individual fold will have a minimum of two limbs but when the folds occur in groups, as this is common, a middle limb will be common to two adjacent folds.

2. The point where the curvature is maximum is ________
a) Hinge
b) Axial surface
c) Nucleus
d) Fold point

Answer: a
Explanation: In a folded layer, a point can be found where curvature is maximum and one limb ends and the other limb starts from that point. This is the hinge point.

3. When the plunge said to be zero, then the axis of the fold is said to be ____________
a) Vertical
b) Horizontal
c) Inclined at 60° to the horizontal
d) Inclined at 60° to its normal.

Answer: b
Explanation: Axis is a line and plunge is the angle which the line makes with a horizontal. A fold having a horizontal axis will obviously have a zero plunge.

4. The crest and trough may or may not coincide with the axis.
a) True
b) False

Answer: a
Explanation: The line running through the highest points in an uparched fold defines the crest and similarly the line running through the lowest point in a downarched fold makes its trough. The crest and trough may or may not coincide with the axis of the fold.

5. What is the axis of a fold?
a) Line drawn normal to the hinge line
b) Line drawn at 60° to hinge line
c) Line drawn parallel to hinge line
d) Line which doesn’t pass through hinge line.

Answer: c
Explanation: Axis of fold is defined as a line drawn parallel to the hinge line of a fold. In other words, line representing the intersection of the axial plane of a fold with any bed of the fold.

6. How is the plunge of a fold measured?
a) Direction
b) Degree
c) Depth
d) Both direction and degree

Answer: d
Explanation: The plunge is measured like a dip of a bedding plane, both in terms of the direction of plunge and degree of plunge.

7. Which of the following about axial plane is not true.
a) Axial plane is imaginary
b) Axial plane may be vertical, inclined or horizontal
c) Axial plane may be planar or non-planar
d) Axial plane need not pass through all points of maximum curvature in a folded sequence

Answer: d
Explanation: An axial plane is defined as an imaginary plane that passes through all the points of maximum curvature in a folded sequence. It may be vertical, inclined or horizontal. Also, it can be either planar or non-planar.

8. The type of fold in which the limbs dip away from each other at the crest is ______________
a) Anticline
b) Syncline
c) Countercline
d) Doesn’t exist

Answer: a
Explanation: Anticlines are defined as those folds in which the limbs dip away from each other at the crest in the simplest forms.

9. The fold which is convex downwards is ___________
a) Anticline
b) Syncline
c) U-cline
d) Crestcline

Answer: b
Explanation: Synclines are the reverse of anticlines in all details and the strata are downarched, that is, these become convex downwards.

10. Which of the following is not true about Anticline?
a) The strata are uparched
b) Geologically older rocks occupy a position in the interior of the fold
c) The limbs dip away from each other at the crest
d) They are convex downwards

Answer: d
Explanation: Anticlines are said to convex upwards and not downwards. Synclines are convex downwards.