ASBOG Practice Exam

Normal faults typically occur within what angle range?

1. 0 to 30 degrees

2. 30 degrees to 60 degrees

3. 45 degrees to 90 degrees

4. 90 degrees to 120 degrees

The correct answer is: 45 degrees to 90 degrees

Normal faults occur in environments where tectonic forces are pulling apart the Earth's crust. This type of fault is characterized by the hanging wall block moving down relative to the footwall block due to these extensional forces. The angle of the fault plane is a crucial factor in understanding the mechanics of normal faulting. Normal faults typically form at angles ranging from 30 degrees to 60 degrees relative to the horizontal. This angle range is optimal for facilitating the movement associated with the tension in the crust, allowing the hanging wall to slide downwards effectively. As the angle increases beyond 60 degrees, the fault behavior may start showing different characteristics, leading into other fault types or indicating different stress regimes in the geological setting. Understanding the specifics of this angle range is critical for geologists when assessing stress conditions and predicting geological behaviors in various terrains. Hence, recognizing that normal faults most commonly fall within this angle range is key to correctly identifying geological fault types and their implications in fieldwork and geophysical studies.