English - Affixes for Grade 6 to 11

Unit 08

The nature of the earth

Grade 07

 By Nisansala samadini (B.Sc. spp, PGDE,Higher dip in Eng, Dip. In teaching)

 

Our solar system

 

What is solar system?

The Solar System is the Sun and all the objects that orbit around it.

There are 8 planets in our solar system.

Earth is position on 3^rd place according to the distance from the sun.

8 planets around the earth accordingly

 

The structure of the earth

Earth is made out of 3 main layers

1.     Core

2.     Mantle

3.     Crust

In this lesson we have to learn bout these 3 layers

 

Core

·        It is the inner most layer of the earth.

·        Thickness of this layer is 3500 Km.

·        It is made out of molten iron and Nickel.

·        The temperature of this layer is about 4400 ⁰ C- 5000 ⁰ C 

·        Upper part of it is consisting of molten iron and Nickel.

 

Mantle

·        It is positioned above the core.

·        Thickness is 2900Km.

·        It is made out of solid rocks and molten rocks.

·        Elements consist in mantel are Silicon, Magnesium , Iron and oxygen 

·        Upper part is solid, due to high temperature lower part is made out of molten rocks.

 

Crust

·        Outer most layer of the earth.

·        Deep bottom of the ocean it is 5 Km and on land it is 35 Km.

·        It is made out of rocks and soil.

·        The elements consist on it is Silicon, Aluminium, Oxygen  

·        When compared with the other layers it is very thin.

 

 

Representing the structure of the earth by an egg

Uses of the crust for humans

1.     Provides us construction materials.

2.     Provides us Metals.

3.     Provides us Fissile fuels.

4.     Gives us soil for agriculture.

  

Tectonic plates and plate tectonics.

The surface layer of the earth crust is divided into secretions and those secretions are known as tectonic plates.

The boundaries between tectonic plates are known as plate boundaries.

 

 Sri Lanka is situated in Australian Indian tectonic plate

 

San Andreas Fault 

·        It is a plate margin situated between North American plate and Pacific plate.

·        It is place in North America. In California.

·        Length is 1000 Km.

·        In areal it is visible as a bird’s eye. 

 

Movement of tectonic plates 

·        Tectonic plates of the earth is floating on larva.

·        Tectonic plates are moving relatively to each other.

·        There are main 3 methods of the movement of tectonic plates.

·        There 3 methods are represented by the following given diagrams.

 

            1.       plates slide past each other

2.       Plates move apart               

3.       One plate moves up by pressing the other down      

 

•  These plates move slowly to each other about 1 to 2 cm per year.

·        Some of these tectonic plates are placed on the earth while some are bellow the sea.

·        When the tectonic plates on the land clash with each other earthquakes will take place.

·        Due to the clashing of tectonic plates clash under the sea Tsunami will take place.

·        Countries place on plate boundaries will subject to prominent earth quakes.

 

Examples for the countries and places of earth the earth quicks take place prominently.

Nepal

Pokhara

India

China

Tibet

Mount Everest

Kathmandu

Bhuthan

Bangladesh