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Rock Cycle

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  • Last Updated : 19 Jan, 2023
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There are mainly three types of rocks; notably sedimentary, igneous, and metamorphic. The rocks are formed out of physical processes and changes- such as melting, cooling, eroding, compacting, or deforming- all of which are part of the rock cycle.

For example, Basalt an igneous rock will melt if it is subducted under a container or it may evaporate if it is exposed to air. Rocks do not stay in equilibrium, they modify or change themselves according to the environment they are subjected to. There are many factors that affect the rock cycle like the tectonic plates, the water cycle, etc. 

Rock Cycle Diagram

The Rock Cycle


The diagram above shows how the rocks are altered or destroyed when it is forced out of their conditions of equilibrium. This cycle of rock formation and wearing out process constantly recycle the minerals of the earth. The Rock cycle is a process by which rocks of one type with certain features change into rocks of another type.

Rock Cycle: Transition to Igneous Rock

When rocks are pushed below the Earth’s surface they are subjected to high pressure and temperatures; which leads to the formation of Magma. There are some specific requirements or conditions for magma to exist once the conditions are not present this magma is converted to Igneous rock. 

This can be seen in Granite, it is formed due to the extremely slow cooling of magma inside the earth’s surface, the grained texture is also a result of this. When there is any volcanic activity the magma is directly exposed to the earth’s atmosphere and cools rapidly, due to the rapid cooling there are no crystals formed, they cause the rocks formed to be fine-grained. Natural glass like obsidian is an example of rocks formed like this. Igneous, sedimentary, and metamorphic rocks can all melt and form magma and then cool to form igneous rocks.

Rock Cycle: Transition to Metamorphic Rock

When rocks are exposed to high pressure and temperature they can change chemically and physically to form a different type of rock. Regional metamorphism describes the changes that take place to huge rock masses over a vast region and is frequently connected to mountain-building activities in orogenic belts. Foliation, often known as discrete bands of different mineralogy and hues, is a frequent feature of these rocks.

When an igneous intrusion makes contact with a body of rock, it warms up the surrounding country rock and results in another major kind of metamorphism. Because of the intense heat of the magma and/or the influx of fluids from the magma that add chemicals to the surrounding rock, this contact metamorphism causes a rock to change and re-crystallize. The processes of metamorphism can change any form of pre-existing rock.

Rock Cycle: Transition to Sedimentary Rock

Rocks that are exposed to the atmosphere can be unstable in many ways and are vulnerable to weathering and erosion. The original rock is reduced to smaller pieces by weathering and erosion, which also removes dissolved minerals. This broken-down stuff builds up and becomes buried under more stuff. Sand grains remain to belong to the type of rock from which they were created, but when they are fused together, they form sedimentary rocks. 

The lithification of these submerged smaller fragments (clastic sedimentary rock), the accumulation and lithification of material produced by living organisms (biogenic sedimentary rock – fossils), or the chemical precipitation of material from a mineral-bearing solution as a result of evaporation are all possible ways that sedimentary rocks can be created. Clastic rocks can be created from fragments of bigger rocks of any sort that have been broken apart by natural processes like erosion or from organic material like plant remnants. Minerals from chemicals dissolved from all other rock types are deposited as biogenic and precipitate rocks.

Factors that drive the Rock Cycle

Plate Tectonics

J. Tuzo Wilson wrote on the recurring opening and closure of ocean basins in a Nature article from 1967, paying special attention to the current Atlantic Ocean region. The Wilson cycle is the name given to this idea, which is a product of the plate tectonics revolution. As plate tectonics came to be understood as the primary cause of the rock cycle, the Wilson cycle had a significant impact on how the rock cycle is currently understood.

Subduction Zones

Moving away from the spreading ridge, the newly formed basaltic oceanic crust finally encounters a subduction zone. The rock undergoes metamorphism as it is dragged back into the mantle, which changes it to produce eclogite. As pressure and temperature rise, the mineralogy of the rock is reorganized. Water and other more volatile components are forced off and ascend into the overlying wedge of rock above the subduction zone, which is at a lower pressure, while the slab of basaltic crust and some associated sediments are pulled deeper. 

To create island arc or continental margin volcanism, the lower pressure, higher temperature, and now volatile-rich material in this wedge melt. The resultant buoyant magma then rises through the underlying rock. The farther away from the island arc or continental margin, the more silicic lavas are seen in this volcanism, indicating a deeper source and a more varied magma. The continental edge may occasionally be forced up or obducted by portions of the metamorphosed downgoing slab. As ophiolite complexes, these blocks of mantle peridotite and the metamorphic eclogites are revealed.

Accelerated Erosion

The forces of erosion are immediately applied to the tall mountain ranges created by continental collisions. Mountains are eroded by erosion, and huge sand accumulations form on nearby ocean edges, shallow seas, and continental deposits. These sedimentary piles lithify into sedimentary rock when they are buried further. The metamorphic, igneous, and sedimentary rocks of the mountains gradually turn into the sedimentary rock as they accumulate in the nearby basins.

Rock Cycle: Evolving Process

The rock cycle of plate tectonics is an evolutionary process. Magma formation promotes the eruption of the more silicic and volatile-rich portion of the crustal or upper mantle material, both in the spreading ridge environment and inside the wedge above a subduction zone. This less dense material is more likely to remain in the crust than to be re-subducted into the mantle. The magmatic features of plate tectonics tend to gradually separate the mantle from the crust or the other way around. 

The early melt of magma is made up of the more silicic phases, which have a lower melting point. This causes the lithosphere to further separate and partially melt. Furthermore, because the silicic continental crust is very buoyant, it is not often re-subducted into the mantle. As a result, the continental masses continue to grow bigger and bigger.

FAQs on Rock Cycle

Question 1: What are the three main types of rocks?


The three main types of rocks- Igneous rocks, sedimentary rocks, and metamorphic rocks.

Question 2: What is the Rock cycle?


The rock cycle illustrates how the three different types of rocks are connected to one another and how processes shift throughout time from one type to another. 

Question 3: What are the stages of the Rock cycle?


Weathering. Erosion and Transport. Deposition of Sediment. Burial and Compaction. Crystallization of Magma. Melting, Uplift. Deformation and Metamorphism are the various stages of rock cycle.

Question 4: Discuss the importance of the Rock cycle.


Because it permits rocks to transform into different types of rocks based on their location and conditions, the rock cycle is a crucial component of our dynamic Earth. In other words, when the Earth’s surface changes as a result of plate tectonics, it aids in the recycling of materials so that new structures may be constructed.

Question 5: How are rocks formed?


As more and more material is dumped on top of the buried sediments, they get compressed. The sediments eventually accumulate to high density turning them into rock. Lithification is the term for this procedure. Igneous rocks are made of melt or lava that has crystallized.

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