What is a Rock?
Rocks are mineral aggregates that combine the traits of every trace mineral. Rock types can be distinguished by any particular arrangement of their chemical composition, mineralogy, grain size, texture, or other distinctive features. For each significant form of rock, various classification schemes exist as well. In nature, there are numerous varieties of rocks. Natural rocks hardly ever display such basic traits, and they typically display some variation in the set of features when the measuring scale shifts.
Types of Rocks
There are three Types of Rocks:
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks
One of the three basic varieties of rock is igneous rock. When lava or magma cools and solidifies, igneous rock is created. Whether it forms as extrusive (volcanic) rocks on the surface or as intrusive (plutonic) rocks below the surface, igneous rock can form with or without crystallisation.
This magma can be produced by the partial melting of pre-existing materials in the mantle or crust of a planet. Usually, one or more of the following three processes—an increase in temperature, a drop in pressure, or a change in composition—lead to the melting.
Basalt, Diorite, Granite, Mica and quartz are examples of Igneous Rocks.
Types of Igneous Rock
Following are the two types of igneous rock:
Intrusive Igneous Rock: As the earth gently cools, these rocks progressively cool and crystallise into huge crystals. Intrusive igneous rocks include pegmatite, granite, and diorite, for instance.
Extrusive Igneous Rock: These rocks erupt onto the surface and soon cool, forming tiny crystals. A few rocks cool so quickly that they turn into an amorphous glass. Extrusive igneous rock includes substances like basalt, tuff, and pumice.
The deposition and subsequent cementation of that material at the earth’s surface and in bodies of water results in the formation of sedimentary rocks. Sedimentation is the process that causes different organic compounds and minerals to gather in one location.
Sediment refers to the particles that accumulate to form sedimentary rocks. The term “agents of denudation” refers to the processes of weathering and erosion that created the sediment before it was delivered to the location of deposition by water, wind, ice, mass movement, or glaciers. Sedimentation can also happen when shells of aquatic animals settle out of suspension or when minerals precipitate from a water solution.
Examples of Sedimentary Rock are Halite, Limestone, Sandstone, Siltstone
Types of Sedimentary Rock
The three categories of sedimentary rock are as follows:
- Rocks called clastic sedimentary rocks are created from the remains of mechanical weathering. A couple of examples of clastic sedimentary rocks are sandstone and siltstone.
- Chemical sedimentary rocks are made up of dissolved substances that precipitate out of solutions. Chemical sedimentary rocks include, for example, iron ore and limestone.
- Organic sedimentary rocks: Plant and animal material accumulates to generate these types of rocks. Examples of biological sedimentary rocks include coal and various types of dolomites.
The Earth’s crust is largely made up of metamorphic rocks, which are categorised according to their structure, chemical composition, and mineral assemblage. They might simply form by being far below the Earth’s surface, being exposed to extreme temperatures, and experiencing the intense pressure of the rock strata above it.
Metamorphism, which literally translates as “change in form,” is the process through which preexisting rock types undergo modification to produce metamorphic rocks. The original rock is heated to temperatures between 150 and 200 °C under pressures of around 1500 bar, which results in significant chemical and/or physical change.
Examples of Marble, Quartzite, Slate, Phyllite
Types of Metamorphic Rock
Following are the two types of metamorphic rock:
- Rocks that have undergone metamorphic foliation as a result of heat and pressure exposure appear to be layered. Some examples of foliated metamorphic rocks are phyllite and gneiss.
- Rocks that underwent metamorphic transformation without developing leaves: Some examples of non-foliated metamorphic rocks are marble and quartzite.
Types of Rocks in India
Following are the classification of rocks in India:
- Archaean System: The oldest and primary rocks are known as the rocks of the Archaean system because they were produced from hot, molten earth. Karnataka, Andhra Pradesh, Tamil Nadu, Madhya Pradesh, Orissa, and some areas of Jharkhand and Rajasthan are home to gneiss, as an example.
- Dharwar System: The earliest sedimentary rocks are those of the Dharwar system, which were created by the erosion and sedimentation of the Archaean system. Karnataka is the main location for them.
- Cuddapah System: The Dharwar system’s sedimentation and erosion produced the rocks of the Cuddapah system. Examples include sandstone, limestone, and marble asbestos, which are primarily found in Rajasthan.
- Vindhyan System: The sediment from river valleys and shallow oceans produced the rocks of the Vindhyan system. For instance, Madhya Pradesh is home to a lot of red sandstone.
- Rocks from the Gondwana System: These were created by basin depressions. One example is coal, which is mostly present in Madhya Pradesh.
- Deccan Trap Rocks were created by volcanic eruptions. Examples include dolerite and basalt, which are primarily found in Maharashtra as well as smatterings of Gujarat, Tamil Nadu, and Madhya Pradesh.
- Tertiary System Rocks: The Himalayan regions are the principal locations for these rocks.
- Quaternary System: The Indus and Ganga plains are home to rocks that belong to the Quaternary system.
Types of Rocks FAQs
Q. What is a rock?
Ans. Rocks are mineral aggregates that combine the traits of every trace mineral. Rock types can be distinguished by any particular arrangement of their chemical composition, mineralogy, grain size, texture, or other distinctive features.
Q. Which is the most common type of igneous rock?
Ans. The most typical igneous rock is basalt. Basalt makes up the majority of the ocean floor.
Q. Give some examples of Metamorphic Rock
Ans. Examples of Marble, Quartzite, Slate, and Phyllite.
Q. Give some examples of Igneous Rocks
Ans. Basalt, Diorite, Granite, Mica and quartz are examples of Igneous Rocks.
Q. Give some examples of Sedimentary Rock
Ans. Examples of Sedimentary Rock Halite, Limestone, Sandstone, and Siltstone.
Other Indian Geography Topics
Other Fundamental Geography Topics