Answer:
The type of stress that pulls and stretches rock, making it thinner, is called tensional stress.
Tensional stress occurs when forces act in opposite directions, pulling or stretching the rock. This type of stress causes the rock to become thinner or elongated.
Imagine holding a rubber band at both ends and pulling it apart. The rubber band stretches and becomes thinner in the middle. This is a similar effect to what happens with rocks under tensional stress.
Tensional stress commonly occurs in certain geological settings, such as at divergent plate boundaries where tectonic plates move away from each other. As the plates separate, tensional stress develops, causing rocks in the lithosphere to undergo stretching and thinning.
Another example of tensional stress is found in fault zones. Faults are fractures in the Earth's crust where rocks have moved relative to each other. In normal faults, tensional stress causes one side of the fault to move downward relative to the other side. This movement creates a gap between the rock layers and results in the stretching and thinning of the rocks.
In summary, tensional stress is the type of stress that pulls and stretches rock, making it thinner. It occurs at divergent plate boundaries and in fault zones.