How Do Rocks Change From One Form To Another

Figure 1. The dissimilar colors and textures seen in this rock are caused by the presence of unlike minerals.

Introduction

There are three types of rocks: igneous, sedimentary and metamorphic. Each of these types is part of the rock wheel. Through changes in conditions ane rock type can get another rock type. Or it tin can become a unlike rock of the same type.

What Are Rocks?

A rock is a naturally formed, non-living earth material. Rocks are made of collections of mineral grains that are held together in a business firm, solid mass (effigy 1).

How is a stone different from a mineral? Rocks are fabricated of minerals. The mineral grains in a rock may be and so tiny that yous can only see them with a microscope, or they may be equally big as your fingernail or even your finger (figure one).

Figure 2. A pegmatite from South Dakota with crystals of lepidolite, tourmaline, and quartz (1 cm scale on the upper left).

Figure 2. A pegmatite from Due south Dakota with crystals of lepidolite, tourmaline, and quartz (ane cm scale on the upper left).

Rocks are identified primarily by the minerals they comprise and by their texture. Each type of rock has a distinctive fix of minerals. A rock may exist fabricated of grains of all one mineral type, such as quartzite. Much more than commonly, rocks are made of a mixture of different minerals. Texture is a description of the size, shape, and arrangement of mineral grains. Are the two samples in effigy 2 the same stone type? Practice they accept the aforementioned minerals? The same texture?

Figure 3. Rock samples.

Sample	Minerals	Texture	Formation	Rock type
Sample one	plagioclase, quartz, hornblende, pyroxene	Crystals, visible to naked middle	Magma cooled slowly	Diorite
Sample two	plagioclase, hornblende, pyroxene	Crystals are tiny or microscopic	Magma erupted and cooled quickly	Andesite

Every bit seen in tabular array 1, these two rocks take the same chemical composition and contain more often than not the same minerals, but they practise not have the same texture. Sample 1 has visible mineral grains, simply Sample two has very tiny or invisible grains. The two different textures signal unlike histories. Sample ane is a diorite, a rock that cooled slowly from magma (molten rock) underground. Sample 2 is an andesite, a rock that cooled rapidly from a very similar magma that erupted onto Earth's surface.

Iii Principal Categories of Rocks

Rocks are classified into iii major groups according to how they form. Rocks can be studied in hand samples that tin be moved from their original location. Rocks tin also be studied in outcrop, exposed rock formations that are fastened to the ground, at the location where they are plant.

Igneous Rocks

Igneous rocks form from cooling magma. Magma that erupts onto Earth's surface is lava, as seen in figure four. The chemic composition of the magma and the rate at which information technology cools determine what stone forms as the minerals absurd and crystallize.

Figure 4. This flowing lava is molten rock that will harden into an igneous rock.

Sedimentary Rocks

Sedimentary rocks form past the compaction and cementing together of sediments, broken pieces of stone-like gravel, sand, silt, or clay (effigy 5). Those sediments can be formed from the weathering and erosion of preexisting rocks. Sedimentary rocks also include chemical precipitates, the solid materials left backside subsequently a liquid evaporates.

Figure 5. This sedimentary rock is made of sand that is cemented together to form a sandstone.

Effigy 5. This sedimentary stone is made of sand that is cemented together to form a sandstone.

Metamorphic Rocks

Metamorphic rocks course when the minerals in an existing stone are inverse past heat or pressure level within the Earth. See effigy 6 for an example of a metamorphic rock.

Figure 6. Quartzite is a metamorphic rock formed when quartz sandstone is exposed to heat and pressure within the Earth.

Figure six. Quartzite is a metamorphic rock formed when quartz sandstone is exposed to heat and pressure within the Earth.

A simple caption of the three rock types and how to identify them can be seen in this video:

This video discusses how to place igneous rocks:

This video discusses how to place a metamorphic rocks:

This Scientific discipline Fabricated Fun video discusses the conditions nether which the three master stone types form:

The Stone Cycle

Figure 7. James Hutton is considered the Father of Geology.

Figure seven. James Hutton is considered the Father of Geology.

Rocks change as a outcome of natural processes that are taking place all the time. Near changes happen very slowly; many take identify below the Earth's surface, then we may not even notice the changes. Although we may not see the changes, the physical and chemical backdrop of rocks are constantly changing in a natural, never-ending cycle called the stone cycle.

The concept of the rock cycle was first adult past James Hutton, an eighteenth century scientist ofttimes called the "Father of Geology" (shown in figure 7). Hutton recognized that geologic processes have "no [sign] of a starting time, and no prospect of an end." The processes involved in the rock cycle often take place over millions of years. So on the scale of a human lifetime, rocks appear to be "rock solid" and unchanging, but in the longer term, alter is always taking place.

In the rock cycle, illustrated in figure 8, the three main rock types—igneous, sedimentary, and metamorphic—are shown. Arrows connecting the three rock types show the processes that modify one rock type into another. The cycle has no showtime and no finish. Rocks deep within the Earth are right at present condign other types of rocks. Rocks at the surface are lying in identify earlier they are next exposed to a process that will change them.

Figure 8. The Rock Cycle.

Effigy viii. The Rock Cycle.

Processes of the Rock Cycle

Several processes can plow one blazon of rock into another type of stone. The central processes of the rock bicycle are crystallization, erosion and sedimentation, and metamorphism.

Crystallization

Magma cools either underground or on the surface and hardens into an igneous rock. As the magma cools, different crystals grade at different temperatures, undergoing crystallization. For example, the mineral olivine crystallizes out of magma at much higher temperatures than quartz. The charge per unit of cooling determines how much time the crystals will take to form. Dull cooling produces larger crystals.

Erosion and Sedimentation

Weathering wears rocks at the World'due south surface downwardly into smaller pieces. The modest fragments are called sediments. Running water, water ice, and gravity all transport these sediments from one place to another past erosion. During sedimentation, the sediments are laid downwardly or deposited. In order to grade a sedimentary rock, the accumulated sediment must become compacted and cemented together.

Metamorphism

When a rock is exposed to extreme heat and pressure within the Earth but does not cook, the rock becomes metamorphosed. Metamorphism may change the mineral composition and the texture of the rock. For that reason, a metamorphic rock may take a new mineral composition and/or texture.

Lesson Summary

Rocks are collections of minerals of various sizes and types.
The three principal rock types are igneous, sedimentary, and metamorphic.
Crystallization, erosion and sedimentation, and metamorphism transform one rock type into another or alter sediments into rock.
The stone bicycle describes the transformations of 1 type of stone to another.

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