waht causes rocks to change ?

Answer 1

There are several forces that act on rocks that forces change in their physical and chemical makeup.

1. Heat: Heat can cause a rock to melt, forcing real changes in its chemical and physical makeup; forcing some elemental components to chemically react with other, both internal and external, chemical components to form entirely new minerals.

2. Erosion: Erosion can be caused by water and wind, and some physical affects such as earth quakes and landslides and rockfalls; water can and almost always erodes away certain portions of rocks, or carries them along at the bottom of a stream, causing them to chip pieces off their extremities, making them rounder and smoother as they are transported. Landslides and rockfalls cause similar flow rounding but the affects are more instantaneous and abrupt and not as pronounced. Then there is wind, wind can pick up small grains of silica sand in an environment and blast away on rocks also causing them to be smoothed and rounded and worn away. Finally, water in its other form, can act like a hydraulic wedge/jack to split large rocks apart with successive freezing and thawings.

3. Then there is geothermal deposition tha takes mineral rock components in solution and deposits them in layers, forming entirely new rocks.

If you want a real surprise some time, try getting a small rock tumbler and just pic up some common looking rocks up out of a stream bed. Get them in all colors...let them tumble for a week or two, then take them out and look at them....you will see dramatic changes...

The tumbler acts like a mini continuous landslide or even like a continuous sand storm...

Check it out

Answer 2

Pressure and heat

Answer 3

heat, time, pressure and erosion

Answer 4

heat or pressure or both.