Which of the following is the primary cause of change in regional metamorphism? pressure rock composition water content silicon content

The primary cause of change in regional metamorphism is pressure. Usually rocks subjected to high pressures at considerable depth within the earth's crust will exhibit regional metamorphism like the widespread phyllites, schists, gneisses and migmatites of the Canadian Precambrian Shield for example. A phyllite is the next higher metamorphic stage than a slate, a schist is a further stage and gneiss and migmatites are of the highest grade of regional metamorphism. On the other hand, contact metamorphism usually depends more on the effect of heat from an igneous intrusion say converting a limestone to a marble (more coarse grained than limestone usually).

The zhou dynasty (1046-256 bce) was the longest-lasting of china's dynasties. it followed the shang dynasty (c. 1600-1046 bce) and it finished when the army of the state of qin captured the city of chengzhou in 256 bce.