we know there are three types of rocks: fiery, metamorphic and sedimentary. Therefore, they are constantly changing their characteristics, changing from one type to another, in a cyclical process called rock cycle (see diagram below).
1st transformation of igneous rocks into sedimentary rocks
As it is a closed cycle, it is not possible to say where its beginning is and where its end is. However, to fully understand the process, let's consider the beginning of the cycle in the transformation of Igneous Rocks.
As the earth moves, many igneous rocks that form many kilometers below the surface end up emerging over millions of years. These rocks end up suffering the action of external agents, such as water, wind, exposure to the sun and rain, among others. With that, the rock changes its characteristics.
This process of soil transformation by external agents is called weathering and your result is the sedimentary rocks. They form when sediments generated by weathering are deposited on the bottom of rivers, lakes and coalesce.
2nd transformation of sedimentary into metamorphic rocks
Over time, the layers of the earth overlap and these sedimentary rocks accumulate to ever greater depths. As a result, they begin to suffer from the pressure of the earth and its extreme internal heat, becoming harder and becoming called metamorphic rocks. The process of heating and hardening the rocks is called metamorphism.
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3rd transformation of metamorphic into igneous rocks
As a continuation of this process, metamorphic rocks can suffer even more from the heat and pressure of the earth, such that they can begin to melt, forming lavas. With the hardening of these lavas, we have the formation of igneous rocks again. The melting process of rocks is called Fusion.
4th direct transformations
It is also possible that an igneous rock suffers from metamorphism again and becomes metamorphic again. Just as it is also possible that metamorphic rocks, instead of heating up even more, appear on the surface, suffering the actions of weathering and transforming into sedimentary rocks.
It is just not possible for sedimentary rocks to turn directly into igneous ones, because even if they heat up a lot, first they become metamorphic and then they turn into fiery.
By Rodolfo Alves Pena
Graduated in Geography
Would you like to reference this text in a school or academic work? Look:
PENA, Rodolfo F. Alves. "Cycle of Rocks"; Brazil School. Available in: https://brasilescola.uol.com.br/geografia/ciclo-das-rochas.htm. Accessed on June 27, 2021.
a) Igneous rocks are formed from the cooling of magma, leading to the formation of rocks such as granite.
b) Weathering transforms igneous rocks into metamorphic ones, as occurred with the formation of limestone in the region of Sete Lagoas (MG).
c) Metamorphic rocks are more resistant to weathering than sedimentary rocks, allowing their use in civil construction.
d) Sedimentary rocks are formed by the compaction process of material from weathering and the transport of igneous or metamorphic rocks.
“[...] It defines the set of processes by which a given rock is transformed, through reactions that process in solid state, in another rock, with characteristics different from those it presented before its acting. These modifications imply changes in the structure, texture, minearological composition or even chemical composition of the rock, which generally occur in combination”.
TEXEIRA, W. et. al. (orgs.) deciphering the earth. Texts Workshop: São Paulo, 2000. p.382.
a) hydromorphism, which transforms hydromorphic rocks into sedimentary ones.
b) laterism, which transforms any type of rock into an oxisol.
c) volcanism, which transforms any type of rock into volcanic.
d) weathering, which transforms igneous rocks into sedimentary ones.
