What type of stress causes a normal fault?

A normal fault occurs in response to tensional stresses, which are forces that act to pull materials apart. This type of stress typically occurs in tectonic settings where the lithosphere is being stretched, such as at divergent plate boundaries or continental rift zones.

When tensional stress exceeds the strength of the rocks, they break, allowing one side of the fault to move downward relative to the other. This downward movement is a defining characteristic of normal faults, distinguishing them from other fault types such as reverse faults, which are caused by compressive stress.

In contrast, compressive stresses would lead to the thickening of the crust and the formation of reverse faults, while shear stresses result in lateral movement, producing strike-slip faults. Mechanical stresses are a broader category that encompasses all types of stress but does not specify the particular conditions that would lead to a normal fault. Thus, understanding the relationship between stress types and fault formation is crucial for geology and tectonics.