Mountains are a result of high-impact compression stress. What happens to the rocks as it experiences stress?

When rocks experience high-impact compression stress, such as that which occurs during the formation of mountains, several things can happen:

1. Elastic Deformation: Initially, the rocks may undergo elastic deformation where they change shape under the stress but return to their original shape once the stress is removed.

2. Plastic Deformation: If the stress continues, the rocks may undergo plastic deformation. This is a permanent deformation, and the rocks do not return to their original shape once the stress is removed. This is what often leads to the folding and bending of rock layers in mountainous regions.

3. Fracture: If the stress levels are very high, the rocks may fracture or break. This can lead to the formation of faults and, in some cases, earthquakes.

4. Metamorphism: Over long periods and under extreme pressure and temperature conditions, the rocks may undergo metamorphism. This is a process where the rock's mineral composition and structure are fundamentally changed. This can lead to the formation of new types of rocks, such as marble or quartzite.

5. Melting: In extreme cases, such as at convergent plate boundaries where one tectonic plate is forced under another (subduction), the rock may melt and form magma. This magma can then rise to the surface and cool to form igneous rocks.

So, in summary, as rocks experience high-impact compression stress, they can deform, fracture, metamorphose, or even melt, leading to significant changes in their structure and composition.