Science Olympiad Dynamic Planet Practice Test

What are the characteristics of a normal fault?

1. Horizontal movement with no vertical component

2. Vertical movement where the rock mass above the fault drops down

3. Movement that always inclines to the left

4. Curved fault planes with horizontal movement

The correct answer is: Vertical movement where the rock mass above the fault drops down

A normal fault is characterized by vertical movement, specifically where the rock mass above the fault, known as the hanging wall, drops down relative to the rock mass below the fault, called the footwall. This type of faulting occurs due to extensional stress in the Earth's crust, which causes the crust to stretch and break. In a normal fault, the mechanics involve gravity pulling the hanging wall downward, enabling it to slide down the inclined fault plane. This vertical displacement is a defining feature that distinguishes normal faults from other types of faults, like reverse or thrust faults, where the movement is upward. The other types of movements presented do not fit the definition of a normal fault. Horizontal movement with no vertical component is more indicative of strike-slip faults. Movement that always inclines to the left lacks the association with vertical displacement characteristic of normal faults. Curved fault planes with horizontal movement could describe various fault types but do not specifically represent the vertical movement typical of normal faults.