Rocks – Types
What are igneous, sedimentary, or metamorphosis rocks? Explain their formation with examples.
Rocks – Types
Rocks are found in the upper part of the lithosphere. These rocks can be classified into various types such as igneous rocks, sedimentary rocks, and Metamorphic rocks. The basis of differentiating the rocks is their origin and their components with which they are formed.
1. Volcanic rocks or igneous rocks –
These types of rocks are formed by the cooling of magma or the hot Lava present inside the surface of the Earth. These are not stratified rocks, which do not occur in strata or layers. Their extreme hardness and resistance, and these types of Rocks are normally crystalline in structure. Based on the acid content, rocks are classified as acid igneous rocks and basic igneous rocks. Those rocks which have a high proportion of silica inside them are acid igneous rocks, for example, granite. These types of rock are less than and lighter in colour as compared to the basic igneous rocks. Basic igneous rocks have a greater proportion of basic oxide, and that is why they are denser and darker in colour.
On the basis of origin, igneous rocks can be classified into plutonic and Volcanic rocks. Plutonic rocks and intrusive rocks are formed at some depth inside the Earth’s crust and are exposed to the surface due to erosion and denudation. Volcanic rocks are extrusive rocks and solidify on the Earth’s surface.
2. The sedimentary rock – there was a time when stratified rocks because they are present in layers. These types of rocks are formed from sediments accumulated over long periods, usually underwater. These types of Rock and non-crystalline and often contain fossil plants and microorganisms. They are the most Varied type of Rock formation, and they are classified according to their age.
On the basis of origin or formation, sedimentary rocks can be classified into mechanically formed rocks, organically formed rocks, and chemically formed rocks.
Examples of sedimentary rocks are conglomerate, limestone, Chalk, sandstone, etc.
3. The metamorphic rocks- all the rocks, whether igneous or sedimentary, become Metamorphic or change rock under great heat and pressure, particularly during intense Earth movements. Due to this, the original character of these rocks may be greatly altered. For example, clay becomes slate, limestone becomes marble, coal becomes graphite, etc.
– Written By Soniya Sanyal
What are rocks?
A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter.*
It is generally made of a chemical composition. Rocks are found on the outer surface of the Earth. Different types of rocks have different types of classifications. Rocks are found almost everywhere. Different types of rocks are there are three types of rocks:
Igneous Rocks –
Igneous rock is formed when magma or lava cools down and solidifies.
Igneous rocks are further divided into two main categories –
– Plutonic or intrusive rocks are formed when magma or lava cools slowly and crystallizes slowly and forming rock. Granites are an example of intrusive rocks.
– Volcanic or extrusive rocks are formed when magma reaches Earth’s surface either as lava or fragmental ejecta and forms minerals like pumice or basalt.
Sedimentary Rocks –
Sedimentary Rocks are deposition and subsequent collection of different types of materials and substances that are present in water, on the upper surface of the Earth. The process through which Sedimentary rocks are formed is called sedimentation. Sedimentary rocks are also formed through the deposition of air. They also contain fossils. There are 3 different types of Sedimentary rocks, and they are: Clastic sedimentary rocks, chemical sedimentary rocks, and Organic sedimentary rocks. Examples of Sedimentary Rocks are limestone, sandstone, etc.
Metamorphic rock –
Metamorphic rock, any of a class of rocks that is formed from the modification of previous rocks because of changing ecological conditions, like variations in temperature, pressure, and mechanical pressure, and the expansion or contraction of compound parts.
The word metamorphism is taken from the Greek for “change of structure”; metamorphic rocks are formed from volcanic or sedimentary rocks that have adjusted their structure (recrystallized) because of changes in their actual climate. Transformation contains changes both in mineralogy and in the texture of the first stone. All in all, these modifications are achieved either by the interruption of hot magma into cooler encompassing rocks (contact transformation) or by enormous-scale structural developments of Earth’s lithospheric plates that change the pressing factor temperature states of the rocks.
– Written By Nehal Rathi
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