compare the igneous and metamorphic rocks?
Answers
Minerals make up rocks. Rocks are formed in many environments upon and within the Earth's crust. There are three types of rock, each formed in a different way. Igneous rock , formed by the cooling of magma (molten rock) inside the Earth or on the surface. Sedimentary rocks, formed from the products of weathering by cementation or precipitation on the Earth’s surface. Metamorphic rocks, formed by temperature and pressure changes inside the Earth. All three types of rock make up the Earth’s lithosphere, the outermost layer. The lithosphere averages about 100 kilometers in thickness.
All igneous rocks began as magma (molten rock) which cooled and crystallized into minerals. Geologists classify igneous rocks based on both their crystal size and composition. Igneous rocks may look different because they may have cooled at different rates and the "mother" magma (original melted rock) was of a different composition. Variations in these two factors have created many different types of igneous rocks. When the magma cools at different rates, it creates different sized minerals. Quick cooling magmas have small minerals (with the exception of obsidian, which is actually composed of silica, but has no crystalline structure). Basalt, for example, has small minerals, most of which can only be seen under a microscope. Quick cooling lavas are called volcanic rocks. Magma that cools slowly creates rocks like granite, which have large minerals that can be seen with the naked eye. These igneous rocks cool inside the lithosphere, and are called plutonic rocks.
Sedimentary rocks form at the Earth’s surface in two main ways. Clastic material (pieces of other rocks or fragments of skeletons) may become cemented together and chemical precipitation and evaporation can form sedimentary rocks. Sedimentary rocks are usually associated with liquid water (which facilitates erosion, transportation, deposition, and cementation). However, sedimentary rocks may also form in dry, desert environments or in association with glaciers.
Metamorphic rocks are igneous, sedimentary, or preexisting metamorphic rocks that have been changed by great pressures and temperatures within the crust and upper mantle of the Earth. The temperatures were not enough to melt the rock, otherwise, an igneous rock would have formed. The pressures were much greater than those required to simply break the rocks into pieces. They were high enough to change the chemical make up of the rock by forcing the elements in it to "exchange partners." Different grades of temperature and pressure will cause the same original rock to form very different metamorphic rocks. Slate, which forms from the sedimentary rock shale, is very dense, smooth and does not contain visible minerals. However, if more pressure and temperature are applied to a slate, it could turn into schist, which has visible layers of minerals. If yet higher temperature and pressure are applied, the schist could turn into gneiss, which shows visible bands of minerals.
Answer:
Minerals make up rocks. ... Igneous rock , formed by the cooling of magma (molten rock) inside the Earth or on the surface. Sedimentary rocks, formed from the products of weathering by cementation or precipitation on the Earth's surface. Metamorphic rocks, formed by temperature and pressure changes inside the Earth.