1. Tensional Stress: The Earth's tectonic plates move and interact with each other. When plates move apart (divergent plate boundaries), they exert tensional stress on the crust. This stress stretches and weakens the rock.
2. Fault Formation: The tensional stress eventually causes the rock to fracture, creating faults. These are breaks in the Earth's crust where rocks have moved relative to each other.
3. Block Uplift: The fault blocks, the sections of rock separated by the fault, can move in different directions. In some cases, the block on one side of the fault will be uplifted, creating a block mountain. This uplift happens because the fault acts as a hinge, and the rock mass is forced upwards.
4. Fault Scarps: The uplifted block will often have a steep, cliff-like face called a fault scarp. This scarp marks the boundary between the uplifted and the relatively lower block.
5. Mountain Range Formation: Over millions of years, continued tension and uplift along multiple faults can lead to the formation of large mountain ranges. These ranges are characterized by their distinctive, blocky structure and steep slopes.
Examples of Fault-Block Mountains:
* Sierra Nevada Mountains (California, USA)
* Wasatch Mountains (Utah, USA)
* Harz Mountains (Germany)
* Basin and Range Province (Western North America)
In summary:
Faults are fractures in the Earth's crust where blocks of rock move relative to each other. When tensional forces cause one block to move upward, it creates a fault-block mountain. Over time, repeated movement along faults can lead to the formation of large mountain ranges.
