Look at all the rocks around you. They are a very important part of your existence, they form soils, are used in construction, for manufacturing substances, making medicines, cosmetics and soo much more. So you kinda get an idea, right?
Come, let us all today see the various kinds of rocks surrounding us and how they are formed.
There are 3 kinds of rocks-
- Igneous rocks- These are the most primary form of rocks and are formed when the molten lava cools and solidifies. They can be formed both inside the earth as well as the earth’s surface. When formed inside the surface of earth, they are known as intrusive igneous rocks (having a course structure with large mineral gains indicating they spent a large amount of time inside the earth’s crust) . Examples are granite and diorite. And when igneous rocks are formed on the earths crust they are known as extrusive igneous rocks. They have relatively small grains and very fine structure. Examples are rocks like basalt and obsidian.
- Sedimentary rocks- These rocks are formed from pieces of existing igneous or metamorphic rocks or biological material that undergo weathering and erosion and get deposited in the form of strata or layers. These are further sub-divided into three types- clastic, organic, and chemical . Clastic(eg.- sandstone) and organic rocks(eg.- coal) are formed due to weathering of rock into small fragments which are later transported to new places, or the biological materials like plants, shells, and bones that are compressed into rock. Chemical sedimentary rocks(eg- limestone) are the result of chemical precipitation. A chemical precipitate forms when the solution (usually water) evaporates and leaves the compound behind.
- Metamorphic rocks- When either the igneous or the sedimentary rocks are subjected to immense heat or pressure, metamorphic rocks are formed. They are of two types- foliated and non-foliated. When the minerals line up in layers, they form foliated rock. (eg.- gneiss- made from granite). Non- foliated rocks follow the same procedure but they do not have the layered appearance of foliated rocks. Sedimentary rocks ( bituminous coal, for example) when provided enough heat and pressure, can turn into non-foliated metamorphic rocks (anthracite coal).
All the three types of rocks are inter-changeable into one another.
- The igneous rock can be subjected to intense heat and pressure and form metamorphic rock or be weathered and eroded to give rise to sedimentary rocks or it can even be subducted and melt to give way to magma and again form igneous rock .
- The sedimentary rocks can either be subjected to extreme conditions of temperature or pressure to form metamorphic rocks or subduct to form magma or even weather and erode to again from sedimentary rock.
- The metamorphic rocks can either erode to give rise to sedimentary rocks or subduct to form magma that can later form igneous rocks.
This is how the rock cycle in our surroundings work. Rocks are continuously weathered and eroded and subducted and exposed to high heat and pressure. Some of the forces that drive the rock cycle are-
- Plate tectonic
- Spreading ridges
- Subduction zone
- Continental collision
- Accelerated erosion
This is all in the article about rock process.