🧭 Introduction 

 Understanding geological structures is fundamental in mining because the occurrence of faults, folds, joints, and fractures directly affects ore localization, strata stability, and safety of operations.
DGMS examinations often test this under the Mine Management & Legislation (MMLGS) and General Safety papers. This article explains folds and faults, their types, characteristics, and significance in mining, as per DGMS syllabus.

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🏔️  Folds – Bending of Rock Layers Definition:
When compressive forces act on rock strata, they bend forming folds instead of breaking. Types of Folds:

1. Anticline – Upward arch (oldest rock at the core).
2. Syncline – Downward trough (youngest rock at the center).
3. Monocline – One limb horizontal, other inclined.
4. Overturned Fold – One limb tilted beyond vertical.
5. Recumbent Fold – Fold turned nearly horizontal.
6. Isoclinal Fold – Both limbs parallel.

Important Terms:

• Axis: Line joining the points of maximum curvature.
• Limb: Sides of a fold.
• Axial Plane: Plane dividing fold into two limbs.

Mining Significance:

• Ore bodies often follow fold axes.
• Fold geometry determines drilling direction & pit slope.
• Underground roadways in folded strata need extra support.

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⚡  Faults – Fracture with Displacement Definition:
When rocks break and move along a plane of fracture, it forms a fault.
Caused by tensional or compressional stresses in the Earth’s crust. Main Parts of a Fault:

• Fault Plane – Surface along which displacement occurs.
• Hanging Wall (HW) – Rock mass above the fault plane.
• Footwall (FW) – Rock mass below the fault plane.
• Throw: Vertical displacement.
• Heave: Horizontal displacement.

Types of Faults:

1. Normal Fault: HW moves downward (tension).
2. Reverse Fault: HW moves upward (compression).
3. Thrust Fault: Low angle reverse fault.
4. Strike-Slip Fault: Movement parallel to strike (horizontal).
5. Oblique Fault: Combined vertical & horizontal movement.

Mining Significance:

• Faults displace ore bodies → production loss.
• May cause water inflow, gas leakage, or roof fall.
• Used as geological markers during mine planning.

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🧩  DGMS Exam Relevance

DGMS often frames descriptive & objective questions such as:

• “Differentiate between anticline and syncline.”
• “Explain fault parts and significance in mining.”
• “Describe how geological structures affect mine layout.”

Understanding structural geology aids in:

• Mine planning
• Stability analysis
• Hazard identification (faulted ground zones)

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⚙️ Quick One-Liners

• Fold = bending; Fault = breaking + displacement.
• Upfold = Anticline; Downfold = Syncline.
• Hanging wall moves down in normal fault, up in reverse fault.
• Faults may act as pathways for water or gases.
• Folds often host ore deposits along hinge zones.

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🖊️ Descriptive Model Answer

Q: Explain folds and faults with examples and their importance in mining.

Answer:
Folds are bends formed in rock strata due to compression, while faults are fractures with displacement.

• Anticlines and synclines indicate structural deformation.
• Normal, reverse, and strike-slip faults show crustal stress directions.
  In mining, folds and faults control ore distribution, ground stability, and water inflow.
  Identifying these structures helps in safe excavation, drilling, and layout design, as mandated in DGMS mining geology syllabus.

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🎯 25 DGMS-Pattern MCQs (with 5 Options & Solutions)

Q1. A fold is caused by:
A. Tension
B. Compression
C. Erosion
D. Deposition
E. Faulting
Answer: B.
Solution: Compression bends rock layers forming folds.

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Q2. An upward fold is known as:
A. Syncline
B. Monocline
C. Anticline
D. Dome
E. Basin
Answer: C.
Solution: Anticline = upward arch.

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Q3. The youngest rocks occur in:
A. Anticline
B. Syncline
C. Overturned fold
D. Dome
E. None
Answer: B.
Solution: In syncline, younger layers at center.

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Q4. The line joining points of maximum curvature is called:
A. Limb
B. Axis
C. Axial plane
D. Core
E. Hinge
Answer: B.
Solution: Axis runs along fold crest/trough.

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Q5. The plane dividing a fold into two limbs is:
A. Hinge plane
B. Axial plane
C. Fault plane
D. Bedding plane
E. Cleavage plane
Answer: B.
Solution: Axial plane bisects the fold.

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Q6. When one limb of a fold becomes nearly horizontal, it is a:
A. Recumbent fold
B. Isoclinal fold
C. Monocline
D. Overturned fold
E. Dome fold
Answer: A.
Solution: Recumbent fold lies almost flat.

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Q7. A fracture in rock with displacement is called:
A. Joint
B. Fault
C. Bedding
D. Cleavage
E. Shear
Answer: B.
Solution: Fault = displacement along fracture.

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Q8. In a normal fault, the hanging wall moves:
A. Upward
B. Downward
C. Horizontally
D. Laterally
E. None
Answer: B.
Solution: Downward due to tension.

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Q9. Which fault is caused by compressional stress?
A. Normal
B. Reverse
C. Strike-slip
D. Oblique
E. Transform
Answer: B.
Solution: Reverse faults form under compression.

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Q10. Fault plane is the:
A. Plane of bedding
B. Plane of folding
C. Plane of displacement
D. Vertical joint
E. None
Answer: C.
Solution: Fault plane is where movement occurs.

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Q11. The block above fault plane is known as:
A. Hanging wall
B. Footwall
C. Ore block
D. Strike block
E. Downthrow block
Answer: A.
Solution: HW = rock above fault plane.

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Q12. The vertical movement in faulting is called:
A. Heave
B. Throw
C. Slip
D. Dip
E. Strike
Answer: B.
Solution: Throw measures vertical displacement.

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Q13. In strike-slip fault, movement is:
A. Vertical
B. Horizontal
C. Inclined
D. Random
E. Diagonal
Answer: B.
Solution: Parallel to strike = horizontal.

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Q14. The fault with both horizontal and vertical movement is:
A. Normal
B. Reverse
C. Oblique
D. Strike-slip
E. Overthrust
Answer: C.
Solution: Oblique fault has combined displacement.

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Q15. Dome and basin structures are:
A. Faults
B. Folds
C. Intrusions
D. Erosional forms
E. None
Answer: B.
Solution: Both are special types of folds.

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Q16. The term ‘throw’ in faults refers to:
A. Depth
B. Vertical displacement
C. Lateral shift
D. Angle
E. Thickness
Answer: B.
Solution: Throw = vertical movement amount.

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Q17. Overturned folds have:
A. Both limbs parallel
B. One limb overturned
C. No axis
D. Vertical limbs
E. None
Answer: B.
Solution: One limb tilted beyond vertical.

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Q18. Faults can serve as:
A. Barriers
B. Water channels
C. Both A & B
D. None
E. Erosional planes
Answer: C.
Solution: Faults may trap or transmit water.

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Q19. The rocks above the fault plane are called:
A. Hanging wall
B. Footwall
C. Roof rock
D. Floor rock
E. Cap rock
Answer: A.
Solution: Hanging wall lies above plane.

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Q20. DGMS relevance of fault identification:
A. Avoids hazard zones
B. Helps mine design
C. Prevents inflow
D. All the above
E. None
Answer: D.
Solution: Fault recognition essential for safe design.

Q21. In a thrust fault, the hanging wall moves:
A. Downward relative to the footwall
B. Upward relative to the footwall
C. Horizontally
D. At 90° to bedding planes
E. Away from the fault plane
Answer: B.
Solution: In thrust faults, compressional stress causes the hanging wall to move upward over the footwall — common in folded, mountainous mining regions.

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Q22. The main stress responsible for forming reverse faults in mine strata is:
A. Tensional stress
B. Compressional stress
C. Shear stress
D. Torsional stress
E. Gravitational pull
Answer: B.
Solution: Reverse and thrust faults develop due to compressional forces, squeezing rock layers together — a crucial stability factor in underground mining.

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Q23. In an anticline, the youngest rocks are found:
A. At the center
B. On the flanks
C. Below the core
D. Uniformly distributed
E. At the contact between folds
Answer: B.
Solution: In an anticline, the oldest rocks are at the core, while younger rocks appear outward — key for planning exploration drilling.

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Q24. Which type of fault plane is most likely to create water seepage hazards in underground mining?
A. Normal fault
B. Strike-slip fault
C. Reverse fault
D. Thrust fault
E. Joint with clay filling
Answer: A.
Solution: Normal faults often create open fractures through which groundwater can percolate — increasing inundation risk in DGMS mine inspections.

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Q25. During DGMS inspections, mapping of folds and faults is critical because:
A. It helps estimate fuel consumption
B. It affects ventilation design and strata control
C. It only identifies fossil zones
D. It reduces equipment breakdowns
E. It is required for blasting records
Answer: B.
Solution: Structural mapping of folds/faults helps in strata control, support design, and hazard prevention — directly linked with Reg. 123 of CMR 2017 on ground control plans.

 

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                    🏁 Conclusion 

 Folds and faults form the backbone of geological structure study.
In mining, recognizing them ensures proper drilling, support, and hazard prevention.
DGMS repeatedly asks conceptual and numerical questions from this topic — mastering it improves both Paper 1 (Management) and Paper 2 (Legislation) performance.

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