Final answer:
Normal faults are created by tensional stresses that result from the stretching of the Earth's crust, which causes one block of rock to move downward relative to another.
Step-by-step explanation:
Normal faults are created by tensional stresses.
When the Earth's crust is subjected to tension, the result is an extension and thinning of the crust. This external force stretches the crust, causing a breakage where one block of rock moves downward in relation to the other block. The forces involved in creating these faults are akin to pulling apart the two ends of a rubber band until it snaps, with each piece moving away from the other.
These types of stress and their effects on rocks are part of the Earth's dynamic tectonic processes. While compressive stresses lead to folding or reverse faults, and shear stresses create strike-slip faults, it is tensional stress that is responsible for normal faults. Such faults typically occur at divergent plate boundaries or in regions where the crust is being stretched.
An understanding of normal faults is essential for comprehending earthquake mechanics and interpreting various geological formations, as these stress-induced fractures can significantly impact the landscape and the underlying structural integrity of the Earth's crust.