The Rock of the earth - their composition and classification
" Rock are natural mineral assemblages crystallized by rock forming processes. Rocks from the earth crust and mantle " ( Huckenholz,1982 ) We distinguish rock according to the origin ( genesis ) and composition between 1. Igneous rock magmatites, magmatic rock, eruptive rocks, eruptiva ) are mineral assemblages, originating from a melt ( magma ) by cristallization. Three types are distinguished by their natural occurrence: a. volcanic rock ( reaching the surface) b. plutonic rock (crystallization ar greater depth ) and c. dike rock ( small dikes and sills separating large rock masses 2. Sedimentary rock Sedimentary rock ( sediment ) are resulth of weathering and sedimentation processes : igneous, metamorphic and also previously depositd sediment rocks are broken down physically and chemically. two main type opf sedimentary rock a. the elastic or fragmental sediment ( sandstones, shales) and b. the chemical and biochemical sediments ( carbonates, evaporates ) 3.Metamorphic rock metamorpithes, metamorpihica, schists are resulth of methamorphism. Metamorphic transformations are caused by change in temprature and pressure. temprature and pressure can changes withiun the earth's crust are caused by different type of processes, such as : a. regional metamorphism b. contact or thermal metamorphism c. dislocation or clastlatic metamorphism.
