Question 1

Answer the following question briefly.What are the uses of rocks?

Accepted Answer

Rocks are used for many purposes but some of them that we can see in our daily life are cited below :Making Cement (Limestone) (Sedimentary Origin)Writing (Chalk) (Sedimentary Origin)Building Material (Sandstone) (Sedimentary Origin)Bath Scrub (Pumice) (Igneous Origin)Kerb Stone (Granite) (Igneous Origin)Roofing Material (Slate) (Metamorphic Origin)Statue/Ornaments/Decoration (Marble) (Metamorphic Origin)Valuable source of minerals (Gold, Diamond, Sapphire e.t.c)Some rocks acts as tourist attraction sites.

Question 2

Tick the correct answer.The innermost layer of the earth is?

Accepted Answer

The innermost layer of the earth is known as the core. It is divided into inner core and outer core. It comprises of a high concentration of nickel and iron.

Question 3

The uppermost layer over the earth's surface is called the ____________.

Accepted Answer

The three main layers of Earth include the crust (1 percent of Earth's volume), the mantle (84 percent), and the core (inner and outer combined, 15 percent). The outermost of all these three is the crust.

Question 4

SIAL and SIMA are the divisions of __________.

Accepted Answer

The topmost layer of the earth is solid, the thinnest and the lightest and is known as lithosphere. The lithosphere has two layer- the outer part and the inner part. The outer part which is immediately below the newer sedimentary formation, i.e, crust. The outer layer of lithosphere mainly found under the continent and inner layer it mostly found partly under oceans. The inner layer again has three layers, i.e, SIAL which is made of silica and aluminum. The average thickness is 8 to 100 km. The layer next to it is SIMA makeup of silica and magnesium and an average thickness of this layer is 100 to 2900 km. The innermost layer is NIFE madeup of nickel and ferrous and the density is 5.1 to 13.

Question 5

Give reasons:(i) We cannot go to the centre of the earth.(ii) Sedimentary rocks are formed from sediments.(iii) Limestone is changed into marble.

Accepted Answer

(i) To reach the centre of the earth one will have to dig a hole 6000 6000km deep on the ocean floor. This is quite impossible and therefore we cannot go to the centre of the earth.(ii) 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.(iii) Limestone is changed into marble as a result of metamorphism under great heat and pressure.

Question 6

Tick the correct answer.The thinnest layer of the earth is?

Accepted Answer

The thinnest layer of the earth is Crust.The Earth can be divided into four main layers: the solid crust on the outside, the mantle, the outer core and the inner core. Out of them, the crust is the thinnest layer of the Earth, amounting for less than 1% of our planet's volume.

Question 7

Answer the following question briefly.How are extrusive and intrusive rocks formed?

Accepted Answer

When the molten lava comes on the earth's surface, it rapidly cools down and becomes solid. Rocks formed in this way on the crust are extrusive igneous rocks.Sometimes the molten magma cools down deep inside the earth's crust. Solid rocks so formed are the intrusive igneous rocks.

Question 8

Which of the following is an igneous rocks?

Accepted Answer

Basalt is a dark-coloured, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. It has a composition similar to gabbro. The difference between basalt and gabbro is that basalt is a fine-grained rock while gabbro is a coarse-grained rock.

Question 9

The name of the layer of the Earth that separates the crust from the core is the ___?

Accepted Answer

Earth mainly consists of four
layers namely crust, mantle, outer core and inner core.Mantle is the widest of all the layers, which is 1800 miles thick. It is composed mostly of
silicate rocks rich in magnesium and iron. It is found beneath the earth’s crust. The
temperature of this layer is 1600 degrees Fahrenheit at the top to about 4000
degrees Fahrenheit near the bottom.

Question 10

Granite is an example of ______________.

Accepted Answer

Igneous rocks are formed through the cooling and solidification of magma or lava. Granite is a light-colored igneous rock. It is composed mainly of quartz and feldspar with a little amount of mica, amphiboles and other minerals.