Inside Our Earth - Class 7 Geography - Extra Questions

Very Short Answer Type Question.
What is the special feature of the thinnest layer?

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.
The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. 


Answer the following question briefly.
What do you mean by a rock cycle?

Like most Earth materials, rocks are created and destroyed in cycles. The rock cycle is a model that describes the formation, breakdown, and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes. All rocks are made up of minerals.


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.

(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.


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

Rocks are used for many purposes but some of them that we can see in our daily life are cited below :

  1. Making Cement (Limestone) (Sedimentary Origin)
  2. Writing (Chalk) (Sedimentary Origin)
  3. Building Material (Sandstone) (Sedimentary Origin)
  4. Bath Scrub (Pumice) (Igneous Origin)
  5. Kerb Stone (Granite) (Igneous Origin)
  6. Roofing Material (Slate) (Metamorphic Origin)
  7. Statue/Ornaments/Decoration (Marble) (Metamorphic Origin)
  8. Valuable source of minerals (Gold, Diamond, Sapphire e.t.c)
  9. Some rocks acts as tourist attraction sites.


Very Short Answer Type Question.
What is called the uppermost layer of the earth?

It is called the crust.


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

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.


Very Short Answer Type Question.
Name the main mineral constituent of the continental mass.

Silica and alumina.


Very Short Answer Type Question.
What are the main constituents of the core?

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


Very Short Answer Type Question.
Name the constituents of the oceanic crust.

Silica and magnesium.


Very Short Answer Type Question.
What is the radius of the core?

The radius of the core is about $$3500$$ km.


Match column I with column II and select the correct answer using the codes given below columns

Basalt - Extrusive igneous rock
Granite - Intrusive igneous rock
Sandstone - Sedimentary rock
Marble - Metamorphic rock


Very Short Answer Type Question.
What happens when igneous and sedimentary rocks go under great heat and pressure?

They change into metamorphic rocks.


Class 7 Geography Extra Questions