Geology of Rocks -What is Rock Cycle and Types of Rocks?

What is Geology of Rocks?

Rocks do not appear in a single structure or form of material. They naturally occur in a solid material. They are consisted on in a different combination of minerals. One rock can have multiple structures due to different gems and minerals found in it. They form, breakdown and are reformed like other earth minerals. Rocks have a complete rock cycle system from birth, reformation and final death like other material on the Earth. A scientist defines rocks by its scientific definition they usually have made for rocks. The measure the rocks by their specific definition of rocks. Scientists have presented a rock cycle which defines the particular type of rock.

Rock cycle is a model defined by scientist that describe the life cycle of rocks like creations, formations, breakdowns, and reformations. Which include igneous, sedimentary and metamorphic rocks. A scientist works on how rocks are formed.

The Rock Cycle

As above it has been cleared that rock cycle includes formation/creation, breakdowns, and reformation. Earth has such a beautiful system where everything is recycled and reused. A big example is the water cycle. The first part of the geology of rocks is its rock cycle which starts from a molten material which erupts from the earth. After which the other processes start.

Types of Rocks

This earthly planet is divided into sheets and

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layers due to different chemical reactions and natural philosophy.

There are many types of rocks on the earth. There are three kinds of primary rocks. Each type of rock has a different origin. Let us some review on the types of rocks and its formations.

There are mainly three types of rocks as per given below.

 Igneous Rocks

Igneous rock is one kind of rock formation. They are connected with volcanic activities which slowly and steadily comes out of the Earth's inner core and finally erupts. Igneous rocks are formed when molten material inside the earth, called magma, cools down.  They are formed from the solidification of molten rocks material. They are connected with Volcano forming a boundary plate type in form of magma. As soon as lava comes out of the ground and cools itself.

There are 2 types of igneous rocks

  1. Intrusive Igneous Rocks
  2. Extrusive Igneous rocks

Intrusive Rocks

When magma solidifies under the surface within the crust and cools itself slowly. It becomes a cause of large crystals. It includes diorite, granite, peridotite, gabbro, pegmatite.

Extrusive Rocks

When magma comes out of the surface and cools down than the formation of rock will be called extrusive rocks.

Sedimentary Rocks

It needs a long long period of time to form sedimentary rocks. Igneous rocks are formed by volcanic eruptions. Sedimentary rocks are built by mud, sand, fossils, sea animals. Sedimentary rocks formation comes out of pre-existing rocks or pieces of living organisms. The deposit continuously gathers on earth surface. They normally have layers or bedding.


There following examples of sedimentary rocks:-

  1. Conglomerate
  2. Sandstone
  3. Mudstone
  4. Limestone and Chalk
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Common Sedimentary Rocks:
Examples: sandstone, shale, limestone. They are often formed by carrying rock deposits in rivers and make deposits of rocks/sand, a living organism in lakes or oceans. The continuous process pressurizes the upper side thus enough to form a sedimentary rock.

Clastic Sedimentary Rocks:
They are formed by pre-existing rock pieces. Weather affects the pre-existing rocks and pieces are slipped down.

Biologic Sedimentary Rocks:
As its name is clear. They are formed by deaths of large numbers of living organisms. An example is Chert forming limestone.

Metamorphic Rocks

Metamorphic rocks are formed by re-pressurization. They come out of the process when heat touches the igneous and sedimentary rocks. They are formed by very high heat and pressure. Earth Movements play a major role information. during earth movement, they get buried again and are exposed to heat and pressure. They don't melt but the minerals change the format due to heat and pressure.


Sedimentary rocks are expected to contain fossils as they are formed by pre-existing sedimentary also.  Limestone forms the marble which has tiny interlocking grains. Shale forms the layers in slate and those are arranged in layers. Roof tiles are an example.


These rocks contain any type of minerals and gemstones in them. Most of them come from underground rocks. Because there heat and pressure works deeply over crystallization. These crystals come out of in gemstones and minerals form such as ruby, onyx, sapphire, beryl, corundum, garnets etc.

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Age of Rock Formation

Earth has a continuous system of creation and destruction of rocks. Geology of rocks tells that the rocks may be million years of old. Scientists say about oldest rock in Western Australia. Its name is Jack Hills which is formed by a combination of metamorphic and sedimentary rocks. They are dated 4.4 billion years old. It happened after a few million years of earth forming itself.


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