Rocks

In geology, rock is any naturally occurring solid mass or aggregate of minerals or mineraloid
matter. It is categorized by the minerals included, its chemical composition, and the way in
which it is formed. Any unique chemical composition, grain size, texture, or other
distinguishing characteristics can describe rock type. Rock can consist of a single mineral or of
several minerals that are either tightly compacted or held together by cement like mineral
matrix.

The mineral composition and texture of igneous rocks can vary widely. The main minerals found
in these rocks include quartz, feldspar, mica, amphibole, and pyroxene. The texture of igneous
rocks can range from fine-grained to coarse-grained, depending on the cooling rate. Igneous
rocks play a crucial role in the rock cycle, as they can be weathered and eroded to form
sediments, which, under the right conditions, may become sedimentary rocks. Igneous rocks
can undergo metamorphism to become metamorphic rocks under high-pressure and high-
temperature conditions.

Types of rocks
The three main types of rocks which are following:

1. Igneous rocks
2. Sedimentary rocks
3. Metamorphic rocks

Igneous rocks
Igneous rocks are one of the three main types of rocks, alongside sedimentary and
metamorphic rocks. They are formed from the solidification and cooling of molten magma or
lava. In this rocks the crystals are formed which known as crystallization. This type of rocks can
make with or without the crystallization.

Types of igneous rocks

There are two primary or main types

1. Intrusive or plutonic rocks

These rocks form from magma that cools and solidifies beneath the Earth's surface. The slow
cooling allows larger crystals to form. Granite, diorite, and pegmatite are common intrusive
igneous rock, characterized by large mineral crystals.

2. Extrusive or volcanic rocks

These rocks form from lava that cools and solidifies on the Earth's surface. The rapid cooling
results in smaller crystals. Basalt, tuff, and pumice are common extrusive igneous rock. It is
often dark in color and is found in volcanic areas.

Sedimentary rocks
Sedimentary rocks are one of the three main types of rocks, alongside igneous and
metamorphic rocks. They are formed through the accumulation, compaction, and cementation
of mineral and organic particles derived from the weathering and erosion of pre-existing rocks.
The process of sedimentation involves the settling of these particles in layers over time.

These rocks are composed of fragments (clasts) of other rocks and minerals. The clasts are
transported by water, wind, or ice and then deposited and lithified. Sandstone (composed of
sand-sized particles), shale (composed of clay-sized particles), and conglomerate (composed of
rounded gravel-sized particles) are common clastic sedimentary rocks.

These rocks form from the precipitation of minerals from a solution. When water evaporates
or when the concentration of minerals in water exceeds its saturation point, minerals crystallize
and accumulate. Limestone, composed mainly of the mineral calcite, is a common chemical
sedimentary rock. Other examples include rock salt (halite) and gypsum.

These rocks are derived from the accumulation and lithification of organic materials, such as
plant debris or the remains of marine organisms. Coal is a significant organic sedimentary rock,
formed from the remains of plants in swampy environments. Limestone can also contain
organic components, such as fossilized shells or coral.

Catastrophism is a geological concept that suggests that Earth's geological features and rock
formations are primarily the result of sudden, short-lived, and often violent events, such as
floods, earthquakes, volcanic eruptions, and other natural disasters. This perspective contrasts
with uniformitarianism, which posits that geological processes act slowly and steadily over long
periods of time. In the context of rock formation, catastrophism implies that significant
geological changes can occur rapidly due to sudden catastrophic events.

Mass wasting, also known as mass movement is a general term for the movement of rock or
soil down slopes under the force of gravity. It differs from other processes of erosion in that the
debris transported by mass wasting is not entrained in a moving medium, such as water, wind,
or ice.

Denudation is a geological process that involves the wearing away, stripping, or reduction of
the Earth's surface by various agents such as weathering, erosion, and mass wasting. It is a
broad term that encompasses the overall effect of these processes in shaping and modifying
landscapes over time. Denudation removes material from elevated areas, exposing and shaping
the underlying geological features.

Type of sedimentary rocks

There are following three types:

1. Clastic (Detrital) Sedimentary Rocks:

Clastic sedimentary rocks are composed of fragments of pre-existing rocks that have been
transported, deposited, and lithified. The process involves weathering, erosion, transportation,
and deposition of mineral and rock fragments. For example sandstone, silt stone, shale, and
conglomerate.

2. Chemical Sedimentary Rocks:

Chemical sedimentary rocks form from the precipitation of minerals dissolved in water. When
the concentration of minerals in a solution exceeds its saturation point, minerals crystallize and
accumulate. For example limestone, evaporites, and iron ore etc.

3. Organic Sedimentary Rocks:

Organic sedimentary rocks are derived from the accumulation and lithification of organic
materials, such as plant debris or the remains of marine organisms. For example Coal, some of
dolomite, and Limestone with Fossils etc.

Metamorphic rocks
Metamorphic rocks are one of the three main types of rocks, alongside igneous and
sedimentary rocks. They form from pre-existing rocks (igneous, sedimentary, or other
metamorphic rocks) that undergo changes in mineralogy, texture, and sometimes chemical
composition due to high temperatures, pressures, or chemically active fluids. The term
"metamorphism" implies a "change in form," and metamorphic rocks reflect the transformative
processes they have undergone. They form a large part of earth crust.
Metamorphic rocks form through the process of metamorphism, which involves changes in
temperature (1500C-2000C), pressure (1500 bars), or the presence of chemically active fluids.
These changes occur without melting the rock entirely.

The original rock from which a metamorphic rock forms is called a protolith. Protoliths can be
igneous, sedimentary, or other metamorphic rocks. The mineralogy, texture, and structure of
the resulting metamorphic rock depend on the composition of the protolith and the conditions
of metamorphism.

Types of metamorphic rocks

1. Foliated: Characterized by the alignment of mineral grains in parallel layers or bands

due to high temperature and pressure. Due to heat the physical change occurs and due
to this new rocks are formed. Examples include slate, schist, phyllite, and gneiss.
2. Non-foliated: Lack a preferred orientation of mineral grains. In this type no layers are
formed. Examples include marble (from limestone) and quartzite (from sandstone).