Rock is a solid mineral matter which has become rock after detaching from earth’s crust or we can say from cliff or mountain. Basically, there are three types of rocks that are igneous rock, metamorphic rock, sedimentary rock. This is one of the basic terminologies that we have studied in 6th standard in geology. Lets us study these rocks in detail:
Molten magma circulates inside the earth. When it cools down it came in a solid form that is called igneous rock. Moreover, it is the primary rock they often have large crystals that you can see from the naked eye.
Magma is the heart of any igneous rocks. We know that magma present in the core of the earth which has a high temperature, so to cool down, it takes time and this process is very slow that’s why we get rock in the form of granite (magma when cool off) for example granite. But if magma erupts and then cool down then you get volcanic rock which also termed as extrusive rocks. For example basalt.
These are most common igneous rock
- Volcanic bomb
These rocks are generally made from different types of magma that present in core.
Sedimentary rocks are the grains of sand that are formed by the accumulation of sediments. Igneous rock is found in the solid form then after a period of time due to various factors like air, chemical, natural processes that rock breaks down into small granules that are called sediments, and those rocks are called sedimentary rocks.
There are three types of sedimentary rocks:
- Clastic sedimentary rock: formed due to mechanical weathering debris. For example, breccia, sandstone, siltstone.
- Chemical sedimentary rock: form when the dissolved material precipitates from solution. For example, iron ore, flint.
- Organic sedimentary rock: form by the accumulation of plant or animal debris. For example, dolomite, coal, limestone.
Metamorphic rocks are formed when sedimentary rocks came under high temperature and high pressure, then metamorphic rocks are formed. For example, clay converted into slates and limestone converted into marble.
There are two basic types of metamorphic rocks:
- Foliated metamorphic rocks: these are having banded appearance, for example, gneiss, schist, slate.
- Non-foliated metamorphic rocks: they do not have folded or banded appearance, for example, hornfels, marbles, quartzite.