1. Tensional Stress:
* The Earth's crust is constantly shifting due to the movement of tectonic plates.
* When these plates pull away from each other (divergent plate boundaries), it creates a force called *tensional stress*. This stress stretches the Earth's crust.
2. Fault Formation:
* Under this tension, the crust eventually cracks, forming *faults*, which are fractures in the rock.
* These faults are often found in a series, forming a system of parallel cracks.
3. Uplift and Downwarp:
* One side of the fault will move upwards, while the other side will move downwards. This creates a kind of "stair-step" effect in the landscape.
* The uplifted blocks form fault-block mountains, while the downwarped blocks create valleys or basins.
4. Erosion and Shaping:
* Over millions of years, weathering and erosion sculpt the mountains, shaping them into their final form.
Key Characteristics of Fault-Block Mountains:
* Steep, straight slopes: These are formed by the fault surfaces.
* Flat, elevated surfaces: The tops of the mountains are often relatively flat because they were once part of a continuous plateau.
* Parallel valleys: Valleys often run alongside the fault-block mountains, created by the downward movement of the crust.
Famous Examples:
* Sierra Nevada Mountains (California): These are a classic example of a fault-block mountain range.
* Wasatch Mountains (Utah): They rise abruptly from the Great Salt Lake Basin.
* Teton Range (Wyoming): This is a relatively young mountain range formed by a system of parallel faults.
In summary: Fault-block mountains are a testament to the powerful forces at work within the Earth. They are formed by tension in the Earth's crust that creates faults, leading to blocks of rock being uplifted and downwarped, shaping the dramatic landscapes we see today.
