What is the Earth?
(i) The earth is a dynamic planet and comprises of three layers: crust, mantle and core.
(ii) Constant changes take place inside as well as outside the earth.
Interior of the Earth:
(i) The Earth is made of several concrete layers.
(ii) The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km on the continental masses and only 5 km on the ocean floors.
(iii) Silica (Si) and alumina (Al) are the main mineral constituents of the continental mass. It is, thus, called sial.
(iv) The oceanic crust mainly consists of silica (Si) and magnesium (Mg) called sima.
(v) Just below the crust is the mantle up to an extent of 2,900 km.
(vi) The innermost layer is core with a radius of 3,500 km. As it is made of nickel (Ni) and iron (Fe), it is called nife. The central core has very high temperature and pressure.
Rocks and Minerals:
(i) The earth’s crust is made of various types of rocks. Any natural mass of mineral matter that makes up the earth’s crust is called a rock.
(ii) There are three major types of rocks; igneous rocks, sedimentary rocks and metamorphic rocks.
(iii) When the molten magma cools, it becomes solid. Rocks thus formed are called igneous or primary rocks. They are of two types, extrusive igneous rocks and intrusive igneous rocks.
- 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. For example, basalt.
- Sometimes, the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Since they cool down slowly, they form large grains. Granite is an example of such a rock.
(iv) Rocks roll down and break into small fragments and these smaller particles are called sediments. These sediments are transported, compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.
(v) Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure. For example, clay changes into slate and limestone into marble.
(vi) The process of transformation of the rock from one to another is called the rock cycle.
- When the molten magma cools; it solidifies to become igneous rock. These
igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks. - When the igneous and sedimentary rocks are subjected to heat and pressure, they change into metamorphic rocks.
- The metamorphic rocks which are still under great heat and pressure melt down to form molten magma. This molten magma again can cool down and solidify into
igneous rocks.
(vii) Rocks are made of different minerals. Minerals are naturally occurring substances which have certain physical properties and definite chemical composition.
For More :-
CBSE
Class–VII | CHAPTER – 1 Integers | NMMS
Revision Notes à Click
Here
Tracing
Changes Through a Thousand Years | NMMS Revision Notes | Class 7 | Social à Click
Here
New
Kings and Kingdoms | NMMS Revision Notes | Class 7 | Social à Click Here
The
Delhi Sultanate | NMMS Revision Notes | Class 7 Social à Click
Here
The
Mughal Empire | NMMS Revision Notes | Class 7 Social à Click Here
Tribes
Nomads and Settled Communities | NMMS Revision Notes | Class 7 Social à Click
Here
Devotional
Paths to the Divine | NMMS Revision Notes | Class 7 Social à Click
Here
The
Making of Regional Cultures | NMMS Revision Notes | Class 7 Social à Click
Here
Eighteenth
Century Political Formations | NMMS Revision Notes | Class 7 Social à Click
Here
Environment
| NMMS Revision Notes | Class 7 Social à Click
Here
Inside
Our Earth | NMMS Revision Notes | Class 7 Social à Click Here
Our
Changing Earth | NMMS Revision Notes | Class 7 Social à Click Here
Air |
NMMS Revision Notes | Class 7 Social à Click Here
Water
| NMMS Revision Notes | Class 7 Social à Click Here
Human
Environment Interactions the Tropical | NMMS Revison Notes | Class 7 Social à Click
Here
Life
in the Deserts | NMMS Revision Notes | Class 7 Social à Click Here
On
Equality | NMMS Revision Notes | Class 7 Social à Click Here
How
the State Government Works | NMMS Revision Notes | Class 7 Social à Click
Here
Role
of the Government in Health | NMMS Revision Notes | Class 7 Social à Click
Here
Growing
up as Boys and Girls | NMMS Revision Notes | Class 7 Social à Click
Here
Women
Change the World | NMMS Revision Notes | Class 7 Social à Click Here
Understanding
Media | NMMS Revision Notes | Class 7 Social à Click Here
Markets
Around Us | NMMS Revision Notes | Class 7 Social à Click Here
A
Shirt in the Market | NMMS Revision Notes | Class 7 Social à Click Here
Nutrition
in Plants | NMMS Revision Notes | Class 7 Science à Click Here
Nutrition
in Animals | NMMS Revision Notes | Class 7 Science à Click Here
Heat |
NMMS Revision Notes | Class 7 Science à Click
Here
Acids
Bases And Salts | NMMS Revision Notes | Class 7 Science à Click Here
Physical
And Chemical Changes | NMMS Revision Notes | Class 7 Science à Click
Here
Respiration
In Organisms | NMMS Revision Notes | Class 7 Science à Click Here
Transportation
in Animals and Plants | NMMS Revision Notes | Class 7 Science à Click
Here
Force
and Pressure | NMMS Quick Revision Notes
| Class: 8 Physics Ã
Click Here
Reproduction
In Plants | NMMS Revision Notes | Class 7 Science à Click Here
Motion
And Time | NMMS Revision Notes | Class 7 Science à Click Here
Electric
Current and its Effects | NMMS Revision Notes | Class 7 Science à Click
Here
Light
| NMMS Revision Notes | Class 7 Science à Click Here
Waste
Water Story | NMMS Revision Notes | Class 7 Science à Click Here
How
When and Where | NMMS Revision Notes | Class 8 Social à Click
Here
From
Trade to Territory | NMMS Revision Notes | Class 8 Social à Click Here
Ruling
the Countryside | NMMS Revision Notes | Class 8 Social à Click Here
Tribals
Dikus and Vision of Golden Age | NMMS Revision Notes | Class 8 Social à Click
Here
When
People Rebel | NMMS Revision Notes | Class 8 Social à Click Here
Weavers
Iron Smelters and Factory Owners | NMMS Revision Notes | Class 8 Social à Click
Here
Civilising
the Native Educating the Nation | NMMS Revision Notes | Class 8 Social à Click
Here
Women
Caste and Reform | NMMS Revision Notes | Class 8 Social à Click Here
