GEOLOGY

Detailed explanation-1: -The correct answer is (4) heat and pressure during metamorphism. The narrow bands in a metamorphic rock are formed when the minerals are realigned due to the presence of high temperature and pressure. The minerals align in such a way that the axes are directed to where the pressure was applied.

Detailed explanation-2: -Gneiss Gneissic banding is a metamorphic foliation in which visible silicate minerals separate into dark and light bands or lineations. These grains tend to be coarse and often folded. A rock with this texture is called gneiss.

Detailed explanation-3: -Normally, the presence of light and dark band of gneiss is due to the seggregation of felsic and mafic mineralization. The alternating darker and lighter bands in Gneiss are because of mafic and felsic minerals therein.

Detailed explanation-4: -Answer and Explanation: Hornfels is a rock formed exclusively from contact metamorphism. This rock comes from a rock that has a large amount of clay coming into contact with hot magma. The heat changes the structure of the rock.

Detailed explanation-5: -Gneiss is a metamorphic rock formed by changing schist, granite, or volcanic rocks through intense heat and pressure. Gneiss is foliated, which means that it has layers of lighter and darker minerals. These layers are of different densities and come about as a result of the intense pressure used to form gneiss.