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Tension
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NOT Tension - you can not actually have tension in the earth other than where there is an overhang! - forces are always compressive, it just depends which force is greater. Normal faults occur when the maximum principal stress is vertical - when GRAVITY is the dominant force.
I'm afraid the first answer is right.
It occurs in continental-plate thinning, stretching and eventual division, as is happening in NE Africa. Although gravity will certainly play a part the displacement that just have a horizontal component.
Gravity alone will not produce a fault unless the rock on one or both sides the fault-plane can move away from the other. There is a fault-form in which the vertical displacement predominates, dropping a block between two faults to produce a graben (such as parts of the North Sea), but it still needs tension resulting in a certain amount of horizontal movement.
What else can I help you with?
What type of force causes a normal fault to form?
Tensional stress from divergent plate boundaries causes a normal fault to form. This stress pulls rocks apart along a fault line, causing the hanging wall to drop relative to the footwall.
Which type of fault is under compression?
Reverse and thrust faults are both under compressive stress.
Which type of fault cause a fault-block mountain to form?
A normal fault causes a fault-block mountain to form. In a normal fault, one block of rock moves downward relative to the other, creating a step-like feature. Over time, repeated movements along the fault can uplift and deform the crust, leading to the formation of fault-block mountains.
What is the type of stress for a reverse fault?
The type of stress for a reverse fault is compressional stress, where the rocks are being pushed together, causing one block to move up and over the other.
What faults are correctly associated with which types of stress?
Normal fault: Associated with tensional stress, where the hanging wall moves down relative to the footwall. Reverse fault: Associated with compressional stress, where the hanging wall moves up relative to the footwall. Strike-slip fault: Associated with shear stress, where the rocks move horizontally past each other.
