Rocks:-
When the different minerals combine occurring
naturally it forms the rock. The rock is formed by the composition of same or
different minerals occurring naturally.
Types of rock:-
The rocks are divided into three main categories
depend upon their composition.
- · Igneous rock
- · Metamorphic rock
- · Sedimentary rock
- These rocks are defined one by one as under:-
1.
Igneous
rock:-
When ever there is some volcanic activity or
volcanic eruption inside or outside the earth they form the rock, this rock is
called as igneous rock. The igneous rocks are formed when the volcanic eruption
or activity takes place.
They
may be classified into two types depending upon their composition. These types
are defined as under:-
·
Intrusive
igneous rock:-
When ever there is volcanic activity or eruption and
when this activity cools inside the earth or its own place the resulting
product forms the rock which is named as intrusive igneous rock. As its name
shows that “intrusive means that inside” so here it means inside the earth. The
intrusive igneous rocks formed when the magma settle and cools inside the earth
or its own place.
·
Extrusive
igneous rock:-
When the volcanic activity takes place in some area
and after some period of time this volcanic activity comes outside the earth
where it cools and settle. This process led to the formation of extrusive
igneous rock. As its name shows that (extrusive means outside) here we means
that outside the earth surface. The extrusive rocks are formed when lava from
the earth comes outside and cools, settle on the earth surface.
2.
Metamorphic
rock:-
When ever the any rock (Sedimentary rock,Igneous
rock) are under the action or influence of “heat” and “pressure” they form the
rock this rock is called as “Metamorphic rock”. The metamorphic rock is formed
by the variation or change in heat and pressure in sedimentary rock or igneous
rock.
Types:-
They are sub divided into three different classes:-
·
Foliated
Metamorphic rock:-
These are those rocks or the type of metamorphic rock
by seeing them through the eye one can easily see the parallel prominent
layers. Foliated metamorphic rocks are those which have layers which are
parallel and prominent.
·
Non-
Foliated Metamorphic rock:-
This is the type of metamorphic rock that one can
easily see that the layers which are not parallel and in some cases not
prominent.Non- foliated metamorphic rock are those which have the layers, and
these layers are not parallel.
·
Cataclastic
Metamorphic rock:-
When ever some small pieces of minerals are combine
or join together they form cataclastic metamorphic rock. Cataclastic
metamorphic rock consists of composed small broken up minerals.
3.
Sedimentary
rock:-
When ever the minerals moves or transported from one
place to another they form the rock this rock is called sedimentary
rock.Sedimentary rock is formed from the transportation of sediments from one
place to another by the action of wind, glacier or river etc.
Agents of transportation:-
There are three main agents of transportation of
sediments from one place to another are as under:-
·
River
·
Wind or air
·
Glacier or ice
Rock Cycle:-
This whole process is represented by this diagram:-
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