Tensional stress causes strain that stretches and thins rock.
Understanding Tensional Stress
Tensional stress is one of three types of stress that affect rock formations, with the other two being compressional and shear stress [1]. Unlike compressional stress, which pushes rocks together, tensional stress involves forces pulling in opposite directions. This pulling action has a distinct effect on the rock material.
Effects of Tensional Stress
- Stretching: The primary effect of tensional stress is to stretch the rock. This is similar to pulling on taffy or rubber band.
- Thinning: As the rock stretches, it simultaneously thins. This is a direct consequence of the applied pulling forces, as the material must give way to the tension.
Practical Examples
While we might not see these effects in everyday life on the surface, tensional stress plays a significant role in various geological processes. For example:
- Faulting: Tensional stress is a driving force behind normal faulting. When tension is applied to a rock structure, the rock may fracture, and one side may slide down relative to the other.
- Rifting: Rifting, a process where the Earth's crust stretches and thins leading to the formation of new ocean basins, is another clear example of tensional forces at work.
Key Takeaways
| Stress Type | Direction of Force | Effect on Rock |
|---|---|---|
| Tensional Stress | Pulling in opposite directions | Stretches and thins the rock |
| Compressional Stress | Pushing together | Folds and thickens the rock |
| Shear Stress | Forces in parallel but opposite direction | Shearing, twisting, and sliding rocks past each other |
In summary, tensional stress results in the stretching and thinning of rock formations. This process is important for understanding various geological phenomena.
