Social Science VSQ (2 Marks)

Limestone is changed into marble because igneous and sedimentary rocks change into metamorphic rocks under a great heat and pressure.

Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.

Extrusive rock: When molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure.
Intrusive rocks: Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous.

Three types of rocks are:

1. Igneous rocks also known as primary rocks.
2. Sedimentary rocks.
3. Metamorphic rocks.

The remains of dead plants and animal beneath the layer of rocks are called fossil.

Minerals are useful to humankind in the following ways:

1. Some are used as fuels. For example, coal, natural gas and petroleum.
2. They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.

• Yes.
• The interior has three major layers of rocks of different densities.
• The earth is made up of rocks.

Sedimentary rocks are formed by solidification of sediments. The sediments when transported by running water or wind carry the remains of plants and animals that come their way. These are sandwiched between the layers of the sedimentary rocks when solidified and become fossils.

Difference between sial and sima:

Sial	Sima
The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina).	The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium)

It is an intermediate layer lies between the crust and the core of the earth. Its avg thickness is about 29,00km. It is believed to consist of solid ultra basic rocks, rich in iron and magnesium.

Minerals are very important to humankind. Some are used as fuels. For example, coal, natural gas and petroleum. They are also used in industries- iron, aluminium, gold, uranium, etc. In medicine, in fertilizers, etc.

Lava is the hot red magma coming out from the interior of the earth to the surface. It cools down and become solid.

The main constituents of the core are nickel and iron. It is usually known as nife.

Igneous-granite, basalt.Metamorphic rocks- marble, slate, graphite.
Sedimentary- limestone, sandstone.

A mineral is a naturally occurring substance having a definite chemical composition and physical properties.

Rocks break down into small fragments known as sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks known as sedimentary rocks.

The remains of the dead plant and animals trapped in the layers of rocks are called fossils.

When the molten magma cools, it becomes solid. Rocks formed in this way are called igneous rocks.

Rocks due to cracks and hitting, breakdown into smaller fragments called sediments.

The innermost part of the earth is known as the core. The thickness of whole layer comprising the outer and the inner core is 4671 km. The outer core starts at the depth of 2900km, rich in iron and nickel.