class 7 extra question chapter inside the earth
Answers
Question 1.
Have you ever wondered what lies in the interior of the earth? What is the earth made up of?
Ans.
Yes.
The interior has three major layers of rocks of different densities.
The earth is made up of rocks.
Question 2.
Describe the interior of the earth.
Answer:
Interior of the Earth:
The earth is made up of several concentric layers with one inside another, just like an onion.
Crust:
The uppermost layer on the earth’s surface is called the crust.
It is the thinnest of all the layers.
It is about 35 km, thick on the continental masses and only 5 km thick on the ocean floors.
Main minerals constituent of the continental mass are silica and alumina.
It is thus called sial (si – silica and al – alumina).
Inside Our Earth Class 7 Extra Questions Geography Chapter 2 - 2
The oceanic crust mainly consists of silica and magnesium.
It is therefore called sima (si – silica and ma – magnesium).
Inside Our Earth Class 7 Extra Questions Geography Chapter 2 - 3
Mantle
Just beneath the crust is the mantle.
It extends up to a depth of 2900 km below the crust.
Core
The innermost layer is the core with a radius of about 3500 km.
It is mainly made up of nickel and iron.
Hence it is called nife (ni—nickel and fe—ferrous i.e., iron).
The central core has very high temperature and pressure.
Rocks and Minerals
Question 1.
What is earth’s crust made up of?
Answer:
Earth’s crust is made up of different type of rocks. Rock is a natural mass of mineral matter. It is of different sizes, colours and texture and shapes. Earth is made up of sedimentary, igneous or metamorphic rocks.
Question 2.
Describe igneous rocks.
Ans.
Igneous Rocks
The molten rock material is called magma.
When it cools, it becomes solid.
Rocks formed in this way are called igneous rocks.
They are also called primary rocks because other rocks are formed out of these rocks.
There are two types of igneous rocks.
Intrusive Rocks and
Extrusive Rocks
Formation of Extrusive and Intrusive Rocks:
Due to extreme heat in the interior of the earth, rocks are found in the form of molten material called magma.
When magma comes out on the surface of the earth, it cools down and turns into solid rocks. Such rocks are termed as extrusive rocks.
Examples:
Basalt.
Deccan Trap is built of basalt.
When the molten magma cools down within the interior of the earth, it becomes solid to form intrusive rocks.
Examples:
Granite
Garbo
Question 3.
What is lava?
Answer:
Lava is the hot red magma coming out from the interior of the earth to the surface. It cools down and become solid.
Question 4.
What are two types of Igneous rocks?
Answer:
Igneous rocks are formed by cooling of the lava. When the lava cools down on the crust it forms extrusive igneous rock for example basalt. They have grained structure.
Sometimes when it cools down deep inside the crust it forms intrusive igneous rocks. They have large grains for example Granite. Grinding stones are made of granite.
Question 5.
Define the term sediment.
Answer:
Rocks due to cracks and hitting, breakdown into smaller fragments called sediments.
Question 6.
Give an account of sedimentary rocks.
Answer:
Sedimentary Rocks
The small particles are called sediments.
These sediments are transported and deposited by wind, water etc. in low areas.
These loose sediments are compressed and hardened to form layers of rocks.
These layered rocks are called sedimentary rocks.
Examples:
Sandstone.
These rocks also contain fossils of plants, animals and other micro-organisms that once lived on them.
Inside Our Earth Class 7 Extra Questions Geography Chapter 2 - 4
Question 7.
What are Fossils?
Answer:
Fossils:
The remains of dead plants and animals trapped in the layers of rocks are known as fossils.
Question 3.
The process of transformation of the rock from one form to another is known as
(a) road cycle
(b) food cycle
(c) rock cycle
(d) all of these
Answer:
rock cycle
Question 4.
Which rock is the molten magma made up of?
(a) Igneous
(b) Metamorphic
(c) Sedimentary
(d) None of these
Answer:
Igneous
Question 5.
What is the latin term of Igneous?
(a) Ignis
(b) Sedimentum
(c) Metamorphose
(d) None of these
Answer:
Ignis
Question 6.
Rocks which contain fossils are called
(a) metamorphic rocks
(b) igneous rocks
(c) core
(d) sedimentary rocks
Answer:
sedimentary rocks
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