Our Changing Earth

The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly- just a few millimeters each year. This is because of the movement of the molten magma inside the earth.The molten magma inside the earth moves in circular manner as shown in the activity.

      The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them .The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces .

       Evolution of Landforms

What is Environment?

In the class Ram asked his teacher," What is environment?" "Whatever you see in your surroundings," said the teacher.

Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live .

     How do human beings modify this natural environment?

The car fumes pollute the air, water is collected in a pot, food is served in vessels and land is used to build factories.

Human beings make cars,mills factories and manufacture containers. this is how human beings modify natural environment.

The place ,people things and nature that surround any living organism is called environment. It is a combination of natural and human made phenomena.While the natural environment refers to both biotic and abiotic conditions existing on the earth,human environment reveals the activities,creations and interaction among human beings.

NATURAL ENVIRONMENT

Land , water,air,plants and animals comprise the natural environment. You are familiar with the meaning of lithosphere, hydrosphere,atmosphere and biosphere from your previous class, Let us learn some more facts about these domains.

    Lithosphere is the solid crust or the hard top layer of the earth. It is made up of rocks and minerals and covered by a thin layer of soil.It is an irregular surface with various landforms such as mountains,plateaus,plains,Valle-ys,etc.Landforms are found over the continents and also on the ocean floors.

Lithosphere is the domain that provides us forests,grasslands for grazing , land for agriculture and human settlements.It is also a source of mineral wealth.

The domain of water is referred to as hydrosphere. It comprises various sources of water and different types of water bodies like rivers,lakes,seas,oceans, etc.

The atmosphere is the thin layer of air that surrounds the earth.the gravitational force of the earth holds the atmosphere around it .It protects us from the harmful rays and scorching heat of the sun .It consists of a number of gases,dust and water vapour.The changes in the atmosphere produce changes in the weather and climate.

Plant and animal kingdom together make biosphere or the living world. It is a narrow zone of the earth where land,water and air interact with each other to support life.

  5 June world environment day

                Barter System

What is ecosystem?

At an NCC camp that Ram's class was attending, John exclaimed, " What a heavy downpour. It reminds me of my home in Kerala.You should come and see how it pours and pours and pours over the lush green fields and coconut plantation." 

      Heera from Jaisalmer exclaimed," We get no rains.We see only ' kikar ' and sand, as far as the eyes can see," " But you also find camels", said Ram.

      Heera says,"Not just camels.If you visit our desert,you will see snakes, lizards and many insects too."

      Ram wondered," Why do the animals, the vegetation and the way people live vary from place to place ? Are they all related to each other?"

     "Oh yes, very much so", the teacher replied.

    All plants animals and human beings depend on their immediate surroundings. Often they are also interdependent on each other. This relation between the organisms and their surroundings from an ecosystem.

There could be an ecosystem of large rain forest, grassland, desert, mountains,lake,river,ocean and even a small pond.

Ecosystem: It is a system formed by the interaction of all living organisms with each other and with the physical and chemical factors of the environment in which the live ,all linked by transfer off energy and material.

           A Ponds Ecosystem

Inside Our Earth

              Interior of the earth

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.

The main mineral Constituents of the continental mass are silica and alumina.It is thus called sial { Si - silica and Al - Alumina }

The oceanic crust mainly consists of silica and magnesium , it is therefore called Sima { Si - silica and Ma - magnesium } just beneath the crust is the mantle which extends up to a depth of 2900 Km.below the crust.

The innermost layer is the core with a radius of about 3500 Km .

It is mainly made up of nickel and Iron and is called nife { ni - nickle and fe - ferros that is Iron}

{ The deepest mine in the world is  South Africa In search for oil engineers have dug a hole about 6000 Km deep.}

                 

          Rocks and Minerals

The earth's crust is made up of various types of rocks.Any natural mass of mineral matter that makes up the earths crust is called a rock.Rocks can be of diffrent colour , size and texture.

There are three major types of rocks: igneous rocks, sedimentary  rocks{Ex- sandstone is made from grains of sand.these rocks may also contain fossils of plants,animals and other micro-organisms that once lived on them} and metamorphic rocks{Ex- clay changes into slate and limestone into marble}.

When the molten magma cools , it becomes solid. Rocks thus formed are called igneous rocks. They are also called primary rocks . There are two types of igneous rocks: intrusive rocks { Ex- Granite }and extrusive rocks{ Ex- Basalt.The Deccan plateau is made up of basalt rocks } .

Can you imagine lava coming out from the volcanoes? Lava is actually fiery red molten magma coming out from the interior of the earth on its surface.When this 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.Sometimes the molten magma cools down deep inside the earth's crust. Solid rocks so formed are called intrusive igneous rocks.

You will be surprised to know that one type of rock changes to another type under certain conditions in a cyclic manner. This process of transformation of the rock from one to another is known as 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 rock.