Final answer:
Mountains and valleys develop from normal faults through fault-block mountain formation, where tension causes rocks on one side of the fault to move downward, creating a depression or valley, while rocks on the other side move upward, forming a raised block or mountain.
Step-by-step explanation:
Mountains and valleys can develop from a series of normal faults in a process known as fault-block mountain formation. Normal faults occur when the Earth's crust is under tension and is being pulled apart. As the rocks on one side of the fault move downward, they create a depression, which eventually becomes a valley. On the other side of the fault, the rocks move upward, forming a raised block or mountain.
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