Folds and Folding topics include: Folds parts and classifications, folding causes and miscellaneous types. Folding is a geological process that causes rock surfaces to curve during deformation. Folds are permanent deformation structures that occur when rocks or parts of the Earth's crust are folded under compressional stress. The type of fold that forms depends on the nature of the rock and the intensity of the compressional force.  Folds are wave-like undulations in the Earth's crust. They are made up of several strata (rock layers). The plane that marks the center of the fold is called... Show more

Folds and Folding topics include: Folds parts and classifications, folding causes and miscellaneous types.

Folding is a geological process that causes rock surfaces to curve during deformation. Folds are permanent deformation structures that occur when rocks or parts of the Earth's crust are folded under compressional stress. The type of fold that forms depends on the nature of the rock and the intensity of the compressional force. 

Folds are wave-like undulations in the Earth's crust. They are made up of several strata (rock layers). The plane that marks the center of the fold is called the axial plane. The line where the axial plane intersects the surface of the Earth is called the hinge line. 

Different types of folds have been recognized based on structure, appearance, and geometry. 

Some types of folds include:
Anticline: An upfold that arches up as both sides of the rock are pushed inward. The arch looks like an "A".
Syncline: A downfold that sinks down as both sides of the rock are pushed inward.
Recumbent fold: A fold that lies down, resulting from the continuation of pressure. The axial plane and both limbs of a fold lie roughly and horizontally.
Isoclinal fold: A fold that shows differences in thickness at the crestal and the trough regions.
Asymmetrical fold: A fold where the axial plane is inclined and vertical. The limbs of the fold are parallel to each other.
Plunge fold: A folded structure that has a “dip” along the hinge line. 

Folding has resulted in the Himalayan Mountains and the Alps.

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Engineering Geology Practice Test: Folds and Folding

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25 Questions

1. All synclines and anticlines can be considered to be homoclines.

FalseDon't KnowMaybeTrue

2. Which are the rocks more prone to flexural slip?

LimestoneSoft clayShaleBasalt

3. Which rock is lifted up during the folding due to intrusions?

Overlying igneous rocksOverlying sedimentary rocksOverlying metamorphic rocksOverlying petroleum rocks

4. The crest and trough may or may not coincide with the axis.

FalseMaybeDon't KnowTrue

5. What is the cause of downward bending?

Flowage foldingDifferential compressionIntrusionsDifferential shearing

6. Which fold is depicted by the figure below?

Drag foldDomeHomoclineMonocline

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

Class 4Class 1Class 3Class 2

8. Pick the incorrect statement about basins.

Involved layers dip towards a common central point from all sidesBasins are the reverse of the domesGroup of strata that are centrally upliftedThey are a group of strata that are centrally depressed

9. Pick the wrong statement about recumbent fold.

It has the arch, which is zone of curvatureIt has the shell, which is the inner zone, made up of mostly igneous rocksIt has the shell, which is the outer zone, made up of mostly sedimentary rocksIt has the core, which is the innermost zone, maybe made up of igneous rocks and metamorphic rocks

10. In which cause of folding, the thickness of fold does not remain uniform?

Flowage foldingFlexural foldingFlexural tensionShear folding

11. The folds caused due to the drag effect are ___________

MonoclineDrag foldsBasinsHomocline

12. How is the plunge of a fold measured?

DegreeDepthBoth direction and degreeDirection

13. A group of strata centrally centrally uplifted is ___________

CleavageBasinDomeValley

14. The anticlines signifying larger bending are called ___________

GeanticlinesGeosynclinesGeoantinclinesGeranticlines

15. The hinge joints in cuspate folds are not very sharp.

TrueMaybeDon't KnowFalse

16. The fold associated with magmatic activity is ___________

Box foldAnticlinoriumDiapiric foldSynclinorium

17. Pick the non-planar fold from the following.

Box foldCheveron foldConjugate foldCuspate fold

18. When the plunge said to be zero, then the axis of the fold is said to be ____________

VerticalInclined at 60° to the horizontalHorizontalInclined at 60° to its normal.

19. Fold with flattened top is ___________

Box foldConjugate foldSquare foldPlateau fold

20. Which of the following is not true about Anticline?

Geologically older rocks occupy a position in the interior of the foldThe limbs dip away from each other at the crestThe strata are uparchedThey are convex downwards

21. What is the axis of a fold?

Line drawn parallel to hinge lineLine drawn at 60° to hinge lineLine drawn normal to the hinge lineLine which doesn’t pass through hinge line.

22. Where is the Liddar Valley Anticline situated?

Uttarakhand HimalayasSikkim HimalayasHimachal Pradesh HimalayasKashmir Himalayas

23. How does the thickness of the layer affect flexural folding?

Thicker the layers, lesser is the slipThinner the layers, greater is the slipThicker the layers, greater is the slipHas no effect

24. What is the other name for upright fold?

Asymmetrical foldSymmetrical foldOverturned foldIsoclinal fold

25. Which is the class of fold with the degree of curvature greater on the outer arc compared to the inner arc?

Class 3Class 4Class 1Class 2