Rock Cycle

Rock cycle refers to the web of processes that outlines how the three main types of rocks- igneous, metamorphic, and sedimentary rocks, form and break down based on various applications of processes of heat and pressure over due course of time. For example, sedimentary rock becomes slate when both heat and pressure are added to it. The more heat and pressure added, the process of rock metamorphoses is furthered until it changes to gneiss and the rock melts down completely and reforms as igneous rock.

What is the Rock Cycle?

Rocks are made of minerals each of which has a specific crystal structure as well as chemical composition. Rocks are made of pieces of other rocks and can be glassy or contain material made by living organisms. Different types of rocks form in the earth’s different environments or below the surface of the earth.

For example, igneous rocks form when molten rock from the mantle or from within the crust cools done and hardens slowly underground or hardens quickly it it erupts from a volcano. Rocks experience sufficient heat and pressure within the earth, without melting, transforming into metamorphic rocks.

Rocks that are exposed to mountain building or even modest forms of weathering and erosion and result in sediments can form sedimentary rocks and the formation as well as the transformation of various forms of rocks can take various paths through the rock cycle which depends on environmental conditions.

Rock Cycle Diagram

Rocks are continually recycled and go through a variety of processes that cause them to undergo both chemical and physical transformations. There are three primary sorts of rocks, which are:

• Sedimentary
• Metamorphic
• Igneous

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 the wearing-out process constantly recycles 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 Steps

1. Igneous rocks form when magma cools to a temperature below its solidification point.
2. Igneous rocks transform into sediments when exposed to severe weather and erosion that characterize the weathering and erosion process.
3. Sedimentary rocks are formed when sediments are pressed together and eventually cement.
4. Metamorphism occurs when sedimentary rocks are subjected to high temperatures and pressure for an extended length of time.
5. Magma is formed when metamorphic rock is heated to very high temperatures for an extended length of time.
6. When exposed to heat and pressure, igneous rock will change and recrystallize into metamorphic rocks.
7. Sediments are formed when metamorphic rock is subjected to weathering and erosion.
8. Furthermore, igneous rocks become magma when they are subjected to temperatures at which they can no longer maintain their solid state.

Factors Affecting Rock Cycle

The factors which affects the rock cycle, both human and environmental phenomena includes the following:

1. The internal heat and pressure of the earth, which causes rocks to melt down completely or to transform it into metamorphic rock.
2. Uplift of land by the processes of tectonic process, which tends to expose rock that were underground by weathering and erosion.
3. The rate of weathering, which are affected by climatic conditions like precipitation and temperature.
4. Plant growth, especially of the roots can physically break up rocks and also change environmental chemistry and kind of rock which is weathered, determines soil quality, nutrient levels and other local biodiversity.
5. Rates of erosion are affected by water, wind, ice, or gravity, which are mostly driven by water cycle, atmospheric and also ocean circulation.
6. The size and depth of bodies of water, where sediments are deposited.
7. Extraction of rocks and fossil fuels, may increase erosion and decrease water quality.
8. Process of urbanisation, which revolves around paving land with concrete, which lead to increase in water runoff.
9. Human land and water uses, which includes deforestation and agricultural activities.
10. Extreme weather conditions increases rates of erosion due to flood or wave actions.

Rock Cycle- Transition and Formation

Rock Cycle Diagram

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, and 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.

Rock Cycle: Evolving Process

The rock cycle of plate tectonics is an evolutionary process. Magma formation promotes the eruption of the crustal or upper mantle material’s a more silicic and volatile-rich portion, 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 comprises the more silicic phases with 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 rarely re-subducted into the mantle. As a result, the continental masses continue to grow bigger and bigger.

Related Links

1. Rocks and Minerals
2. Three Types of Rock

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