What weathering agent would cause rocks to be pushed to the earth's surface where they often crack or break? erosion gravity pressure changes temperature

pressure changes

Weathering is a natural phenomena in which the rocks are broken down into small pieces or sediments. It is caused by weathering agents such as wind, water, chemical, pressure and temperature.

Pressure changes is the weathering agent which would cause rocks to be pushed to the earth's surface where they often crack or break. The pressure could be applied by the superficial rocks or any other denser object.  

the answer to your question is slate

the fossil record provides evidence of a common ancestor to many species.