Question

Thrusts are characterized by:

• A. transporting younger rocks on top of older ones over a long distance
• B. transporting older rocks on top of younger ones over a short distance
• C. transporting younger rocks on top of older ones over a short distance
• D. transporting older rocks on top of younger ones over a long distance

Hint:

In thrust faults, older strata override younger ones over long horizontal displacements.

Answer 1

The Correct Option is D

To understand the characteristic features of thrust faults, we analyze their structural geology properties.

1. Definition of Thrust Faults:
Thrusts are low-angle reverse faults (dip < 30°) that result from compressional tectonic forces.

2. Key Characteristics:
- Age relationship: Transport older rocks over younger ones (opposite of normal stratigraphy)
- Movement distance: Typically involve large displacements (kilometers to tens of kilometers)
- Fault angle: Have shallow dip angles (usually 10°-30°)

3. Evaluating the Options:
The correct combination is:
Transporting older rocks on top of younger ones over a long distance
This matches all diagnostic thrust characteristics.

4. Why Other Options Are Incorrect:
- Any scenario with younger-over-older violates thrust mechanics
- Short-distance movement describes smaller-scale reverse faults
- The combination of older-over-younger plus long distance is unique to thrusts

5. Geological Significance:
Thrusts are important for:
- Mountain building (e.g., Himalayas, Alps)
- Petroleum trap formation
- Crustal shortening measurements
- Earthquake hazards in compressional regimes

Conclusion:
Thrusts are uniquely characterized by transporting older rocks over younger ones across considerable distances.

Final Answer:
The correct option is: transporting older rocks on top of younger ones over a long distance.