Engineering Geology Multiple Choice Questions on “Causes of Folding – 01”.
1. Pick the option which is not the cause of folding.
a) Folding due to tangential tension
b) Folding due to tangential compression
c) Folding due to intrusions
d) Folding due to differential compression
Answer: a
Clarification: The various causes of folding that are studied are, folding due to- tangential compression, intrusions and differential compression. Hence first option is not correct.
2. Bending or warping is studied under ___________
a) Tectonic folding
b) Non-tectonic folding
c) Volcanic folding
d) Intrusional folding
Answer: b
Clarification: Folding may be either due to tectonic causes or due to non-tectonic causes. The tectonic folding of the rocks is bending or warping of rocks due very conspicuously to superficial processes.
3. The cause of folding which does not occur due to the tangential stresses is ___________
a) Flexural folding
b) Flexural creeping
c) Flowage folding
d) Shear folding
Answer: b
Clarification: Under the influence of tangential stresses, folding may develop in either of the three ways: flexural folding, flowage folding and shear folding.
4. How does the thickness of the layer affect flexural folding?
a) Thinner the layers, greater is the slip
b) Thicker the layers, lesser is the slip
c) Thicker the layers, greater is the slip
d) Has no effect
Answer: c
Clarification: Thickness of the layers and nature of the contact are important factors on which the amount of slip depends. Thicker the layer, greater is the slip.
5. Which are the rocks more prone to flexural slip?
a) Shale
b) Basalt
c) Soft clay
d) Limestone
Answer: d
Clarification: Types of the rocks involved: siltstones, sandstones and limestones are more prone to flexure slip folding compared to soft clays and shales.
6. In which cause of folding, the thickness of fold does not remain uniform?
a) Flexural folding
b) Shear folding
c) Flowage folding
d) Flexural tension
Answer: c
Clarification: During the compression due to flowage folding, the material of the involved layers behaves almost as a viscous or plastic mass and gets buckled up and deformed at varying rates suffering unequal distortion. In such cases the thickness of the resulting fold does not remain uniform.
7. Flowage folding occurs in which type of rocks?
a) Competent rocks
b) Incompetent rocks
c) Any rock
d) Sedimentary rock
Answer: b
Clarification: Flowage folding is the principal process of folding in incompetent or weaker, plastic type of rocks such as clays, shales, gypsum and rock salt etc.
8. How does the distance from hinge point affect displacement due to folding?
a) Greater the distance, larger is the displacement
b) Lesser the distance, larger is the displacement
c) Doesn’t depend on the distance from hinge point
d) Greater the distance, smaller is the displacement
Answer: a
Clarification: Distance from hinge point is also an important factor on which displacement of folding depends. Greater the distance from the hinge points, larger is the displacement.
9. Flexural folding is also called as “flexural-slip-folding”.
a) False
b) True
Answer: b
Clarification: Flexural folding is also distinguished as flexural-slip-folding in which the slip or movement of the strata involved takes place parallel to the bedding planes of the layers.
10. The process of folding which causes fracture in rocks initially is ___________
a) Flexural folding
b) Flowage folding
c) Shear folding
d) Intrusion folding
Answer: c
Clarification: In many cases, folding is attributed to shearing stresses rather than simple compression. It is assumed that in such a process, numerous closely spaced fractures develop in the rock at the first stage of the process.
11. Pick the wrong statement. The converging plates maybe ___________
a) Two continental plates
b) A continental plate and an oceanic plate
c) A continental plate and an island plate
d) Two oceanic plates
Answer: d
Clarification: The converging plates may be two continental plates, a continental plate and an oceanic plate or a continental plate and an island plate but not two oceanic plate.
12. The displacement at the hinge point is maximum.
a) True
b) False
Answer: b
Clarification: Greater the distance from the hinge points, larger is the displacement, so much that it may be negligible at the hinge point. Hence the statement above is not true.