The document summarizes key details about the structure and composition of the Earth's interior. It describes how the Earth can be divided into three main layers - the crust, mantle, and core. The crust is the solid outermost layer and is made up of either continental or oceanic crust. Below the crust is the mantle, which extends to a depth of 2,900 km and is composed of dense materials like iron and magnesium. The core is at the center of the Earth and is made of heavy metals like nickel and iron, with temperatures reaching over 5,000°C.

1. INSIDE OUR EARTH
Class 7
NCERT
Chapter- 2

2. Key points:
• Detailed study of interior is done by geologists
• Temperature increases with depth { approx.
5000⁰C at Centre}
• Earth is a solid body up to a depth of 2900km
• Average density of earth is about 5.5g per
cubic cm
• Density of rocks increases towards the centre

3. STRUCTURE OF EARTH

4. CRUST-
 Solid outermost layer
 Also known as lithosphere
 Continental crust(35km thick)
[SiAl]
 Oceanic crust(5km thick) [SiMa]
 Average density- 3.0 g per cubic
cm
MANTLE-
 Layer beneath crust
 2900km thick
 Made of dense and heavy materials
such as iron and magnesium
 Average density ranges between 3.5g
to 5.5 g per cubic cm
 Magma is found in this layer
CORE-
 Also known as barysphere
 Average radius is about 3500km
 Made of heavy metals such as
nickel and iron [NiFe]
 Temperature varies from 2200 to
5000⁰C
 Average density ranges between
5.0g and 13.0g per cubic cm

5. TYPES OF ROCKS

6. IGNEOUS ROCKS
• Comes from Latin word ‘ignis’ meaning ‘fire’
• Formed when magma cools and solidifies
• Also known as primary rocks
• Intrusive igneous rocks- rocks that cool below the surface of
the earth; rate of cooling is slow so crystals formed are large.
Eg: granite, dolerite
• Extrusive igneous rocks- cool on surface of the earth; also
known as volcanic rocks; due to rapid cooling crystals are fine-
grained

7. SEDIMENTARY ROCKS
• Fragments carried by running water, wind and ice are
deposited in depressions.
• The deposited materials are sediments ; on compression and
hardening forms sedimentary rocks
• Most widespread and cover 75% total land area of earth
• On the basis of formations- mechanically(sandstone);
chemically(salt) ; organically(coal)
• Also contain remains of plant and animals, called fossils

8. METAMORPHIC ROCKS
• Actually igneous or sedimentary rocks changed due to
excessive heat and pressure inside our earth
• Changed original properties of rocks such as colour, hardness,
texture and mineral composition
• Do not have empty spaces in them

9. ROCK CYCLE