Classification of the sediments (that form the sedimentary rocks) is made on the basis of the sources of the sediments. Some of the rocks are formed from the sediments obtained from pre-existing rocks, while some are formed from the sediments sourced from the minerals precipitated from water. On the basis of the above mentioned two
Sedimentary Rocks The upper 16 km thick earth’s crust contains only 5% of the sedimentary rocks, while the percentage of the sedimentary rock in the exposed rocks is about 75%. These rocks are found chiefly as an extensive cover over the continental crust. In the subject of rock formation, sedimentary rocks and their formation is
There are two basic types of igneous rocks i.e. Intrusive Igneous rocks and Extrusive igneous rocks. Intrusive igneous rocks are those, which crystallize below the earth’s surface, and remain buried until the earth’s surface is eroded, while extruded igneous rocks are those, which erupt onto the surface, where they cool quickly to form small crystals.
We can find the mineral composition of igneous rocks by means of studying the chemical composition of the magma from which the rock has been crystallized. Because there is a large variety of igneous rocks, thus it was originally thought an equally large variety of magma also existed. But the later research found out that
Differentiation of Magma while cooling and solidification: Magmatic differentiation means the split of magma into various parts due to the presence of different types of chemicals in it. These parts of magma on cooling and solidification produce rocks of different types. As the chemical composition of magma differs in its different parts and layers, the
Formation of Igneous Rocks: The igneous rocks are formed from the cooling and solidification of the Magma/Lava. The minerals and the chemical makeup of igneous rocks are important in order to understand their formation. Experimental studies of the crystallization sequence of minerals from a melt have helped greatly in understanding the origin of igneous rocks.
Source of Magma: Magma is originated from the upper mantle, which lies just under the crust, and is nearly molten. A slight drop in pressure caused by dee faulting etc, completes the melting process. The basaltic magma originates in this manner, while the “granitic magma” can be produced in two ways: (a) from melting of
The igneous material is of two types; one is extrusive, and the other is intrusive. The extrusive igneous bodies are formed from the magma poured out at the surface of the earth. The lava flows are examples of extrusive igneous material. While the igneous bodies are formed by the consolidation of magma at some depth
Once the molten magma extrudes out, it is affected by several factors. These factors provide varied structures to the rocks on cooling. Some important factors are as under; (1). Flow Structures: Sometimes an igneous rock shows parallel or subparallel bands or streaks which are caused by the flow of magma or lava during cooling and