Rock (geology)

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==Rock (geology) ==

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Rock formations

Rock is a naturally occurring solid aggregate of one or more minerals or mineraloids. Rocks are categorized by the geological processes that formed them and are classified into three major groups: igneous, sedimentary, and metamorphic.

Types of Rocks

Igneous Rocks

Igneous rocks are formed from the solidification of molten material called magma. They are further classified into two types based on where the solidification occurs:

• Intrusive (or plutonic) rocks form from magma that cools slowly beneath the Earth's surface. Examples include granite and diorite.
• Extrusive (or volcanic) rocks form from lava that cools quickly on the Earth's surface. Examples include basalt and andesite.

Sedimentary Rocks

Sedimentary rocks are formed by the accumulation and consolidation of sediments. These sediments can be fragments of other rocks, minerals, or organic material. Sedimentary rocks are often deposited in layers and may contain fossils. They are classified into three main types:

• Clastic sedimentary rocks are composed of fragments of other rocks. Examples include sandstone and shale.
• Chemical sedimentary rocks form from the precipitation of minerals from water. Examples include limestone and chert.
• Organic sedimentary rocks are composed of organic material, such as plant debris. Examples include coal and oil shale.

Metamorphic Rocks

Metamorphic rocks are formed from the alteration of existing rock types (igneous, sedimentary, or other metamorphic rocks) in a process called metamorphism, which means "change in form". This process is driven by changes in temperature, pressure, and chemically active fluids. Metamorphic rocks are classified based on their texture and mineral composition:

• Foliated metamorphic rocks have a layered or banded appearance. Examples include schist and gneiss.
• Non-foliated metamorphic rocks do not have a layered appearance. Examples include marble and quartzite.

Rock Cycle

The rock cycle is a continuous process by which rocks are created, altered, destroyed, and reformed. It involves the transformation of rocks through various geological processes, including weathering, erosion, deposition, compaction, cementation, melting, and crystallization.

Uses of Rocks

Rocks have been used by humans for millions of years for various purposes, including:

• Construction: Rocks such as granite and limestone are commonly used in building materials.
• Tools: Early humans used rocks to create tools and weapons.
• Art: Rocks have been used in sculpture and other forms of art.
• Industrial: Rocks are used in various industrial processes, such as the production of cement and glass.

See Also

• Mineral
• Geology
• Petrology
• Earth's crust
• Plate tectonics