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This figure shows six different metamorphic rocks; these include eclogite, gneiss, slate, schist, phyllite, and marble.

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Metamorphic rocks are one of the three types of the previously mentioned rocks. They form when they are exposed to high temperatures and pressures, and are characterized by the fact that they do not turn into magma beforehand.

Metamorphic rocks are usually named "changed rocks" due to the fact that they change their chemical and physical structure from previous igneous or sedimentary rocks.

Some examples of metamorphic rocks include:

Gneiss, which is commonly used for interior and exterior spaces in walls and landscaping.

Slate, which is used for roofing, gravestones, flooring, and garden decorations.

Marble, which is used for interior design (like countertops) and for the construction of statues.

Formation of Metamorphic Rocks

The formation of a metamorphic rock begins from the parent rock, which can either be igneous, sedimentary, or another metamorphic rock; the parent rock is also called the "protolith."

When the protolith (parent rock) is exposed to extremely high temperatures and pressures, metamorphic rocks are formed.

Naturally occurring metamorphic rocks can be found near volcanic sites and mountain ranges like the Himalayas.

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Based on the rock cycle diagram, it can be seen that metamorphic rocks are formed via high heat and pressure applied to sedimentary or igneous rocks.

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This figure shows six different sedimentary rocks; these include shale, siltstone, conglomerate, sandstone, ironstone, and limestone.

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The next type of rock that will be discussed are sedimentary rocks.

Sedimentary rocks are formed by the compaction and cementation of sediments (small materials formed by the weathering and erosion of any of the three rocks mentioned).

These rocks are crucial for comprehending Earth's past since they are frequently discovered in the Earth's layers (primarily in the crust) and may include fossils.

Some examples of sedimentary rocks include:

Limestone: Limestone is used in architectural applications for walls and decorative trims.

Ironstone: Ironstone is usually used a substitution for building when other rocks aren't present; they provide use for being a rubble wall fill.

Shale: Shale is commonly used for pottery, construction of bricks, and tiling.

Formation of Sedimentary Rocks

One of the primary ways or methods that sedimentary rocks are able to form is through the process of weathering.

Weathering is the physical degradation and breakdown of rocks when in contact with water or other atmospheric gases.

There are three types of weathering: physical, chemical and biological weathering.

Physical Weathering: This includes the breakdown and change of physical composition of the rock by forces like wind, water, and ice. This does not alter the chemical structure of the rock.

Chemical Weathering: This includes the change of chemical structure of a rock and occurs when the rocks engage in different chemical reactions.

Biological Weathering: Involves the breakdown of rocks by living things, such as plants and animals, which adds organic content to sedimentary rocks like shale or coal.

Sedimentary rocks are naturally found in places like deserts, caves, and lakes.

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As can be seen in the diagram above, sediments that are formed from the erosion and weathering of metamorphic, sedimentary, and igneous rocks can create sedimentary rocks via gradual compaction and cementation.

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As can be seen from the diagram above, igneous rock is formed from when metamorphic rock melts to magma that is later cooled.

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This figure shows a diagram of the rock cycle.

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The rock cycle is the process that refers to the gradual change of rocks from one type to another via several geological processes.

Rocks can change types based on conditions of heat, pressure, and surface processes like erosion and weathering (whether physical, chemical, or biological).

Rocks are generally classified into three types:

Metamorphic rocks

Sedimentary rocks

Igneous rocks

These rocks can be seen everyday in our lives, from granite in countertops, to limestone in cement production.

A few observations can be made from the diagram:

Sediments are formed from the erosion and weathering of any type of rock, and sedimentary rock can form via the compaction and cementation of sediments.

Heat and pressure applied to either igneous or sedimentary rocks to create metamorphic rocks.

The melting of metamorphic rocks creates magma, and the cooling of magma creates igneous rocks.

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This figure shows six different igneous rocks; these include obsidian, granite, pumice, basalt, and rhyolite.

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The last type out of the three classifications of rocks that will be discussed are igneous rocks. They form when magma formed by the melting of metamorphic rocks are significantly cooled down.

Igneous rocks make up the majority of the Earth's crust, and are primarily divided into two categories: intrusive (plutonic) and extrusive (volcanic).

Intrusive Rocks: Magma gently and slowly cools beneath the Earth's surface to form these rocks. Crystals have more time to form and become visible to the unaided eye due to the slower cooling process. Granite and diorite are notable examples.

Extrusive Rocks: When magma erupts as lava and cools rapidly on the Earth's surface, these rocks are created. These rocks are usually fine-grained or even glassy because of the quick cooling, which prevents crystals from growing huge. Pumice, basalt, and obsidian are a few examples.

Some examples of igneous rocks and their uses include:

Granite is widely used for building bridges, paving, monuments, and many other exterior projects.

Historically, obsidian has been used to create weapons, tools, ornaments, and more.

Basalt is commonly found in railroads and is used for concrete aggregates.

Formation of Igneous Rocks

Molten rock beneath the Earth's surface, known as magma, cools and solidifies to produce igneous rocks.

Large, visible crystals, like granite, are formed by intrusive igneous rocks when the magma cools gradually beneath the surface.

If the magma erupts onto the surface as lava and cools quickly, it forms extrusive igneous rocks, which are typically fine-grained or glassy, like basalt or obsidian.

The final rock's texture and appearance are determined by the magma's mineral makeup and rate of cooling.

Basalt and pumice are examples of extrusive igneous rocks that are frequently found in regions with active volcanoes or past volcanic landscapes. When lava erupts from a volcano and rapidly cools, these rocks are created.