1.What are Minerals?
Rocks are made up of small grains. A single rock may be made up of grains of different colours. These grains are of naturally occurring substance known as minerals. Minerals are the building blocks of rocks. Each rock is a mixture of one or more minerals.
2. What are the earth's crust made up of?
The Earth's crust is made up of three main types of rocks. They are.
∗ Igneous rocks
∗ Sedimentary rocks
∗ Metamorphic rocks
3. How do igneous rocks form ?
Deep inside the Earth, it is so hot that the rocks melt. This melted ( or molten) rockl is known as magma . Magma gets pushed upwards to the surface of the Earth because of pressure inside. On the surface it cools to form solid rock again. These rocks are known as igneous rocks.
4. How we can classify igneous rocks ?
Ingenious rocks can be of different types depending on how the magma cools. Sometimes magma cools slowly under the Earth's surface. Sometimes it spills out through cracks in the Earth's crust or explodes out from a volcano as Lava. Once out the lava cools quickly and form rocks. Based on this igneous rocks can be classified into three. They are.
5. Write a short note about " Granite "?
Granite is formed when magma cools slowly under the surface of the Earth. It is very hard, and has large grains. It is made up of three main minerals - mica, quartz and feldspar. It may be white, grey, pink, red or black depending on the mixture of minerals it contains. Granite is very hard and is used in making buildings and statues.
6. What are the uses of Granite?
Granite is used in making building and statues. Polished granite is used for flooring. Small pieces of granite are used to make foundations for buildings and for paving roads.
7. What is Basalt?
Basalt is a fine - grained and glassy igneous rocks. It is formed when volcanic lava cools very fast and hardens quickly above the surface of the earth, after coming in contact.
8. Explain about pumice?
Pumice is one type of Igneous rock. Pumice is a light coloured igneous rock that forms when frothy lava cools quickly on the Earth's surface. As it cools, the gases in the froth remain trapped inside. Pumice therefore looks like a sponge with holes and pockets in it. Pumice is used as a body scrubber and also to polish furniture and floors.
9. What are sedimentary rocks / and how they forms ?
Sedimentary rocks are formed from older rocks that have been broken into tiny fragments. Wind and rain take away these tiny bits of rocks to rivers, lakes and seas where they sink to the bottom and form layers called sediments. As the layers of sediments build up, the layers below get squeezed together. Over millions of years the pressure turns these layers into hard rocks. Such rocks are known as sedimentary rocks. Sometimes, the remains of dead organism may be buried in sediments that later become sedimentary rocks.
10. What are fossils?
The hard part of organisms such as shells and bones either get preserved in the sediments, or leave behind an impression. These impressions left behind in sedimentary rocks are known as fossils . Fossils tell as alot about the types of living beings that existed on the Earth millions of years ago.
11. Which are the different types of sedimentary rocks?
12. What is shale?
Shale is one type of sedimentary rock. Shale is formed when layer of clay harden. It is smooth and mostly used to make tiles and bricks.
13. Write a short on sand stone?
Sandstone is one type of sedimentary rock. It is formed when sand grains get compressed and cemented together. It consists mostly of a mineral called quartz. Sandstone is commonly used in making buildings. The Red fort and a major portion of the Qutab Minar in Delhi are made out of red sand stone.
14. Differentiate conglomerates and Limestone?
Conglomerates and Limestone are two different types of sedimentary rocks.
Conglomerates:- Conglomerates look like pebbles cemented together with minerals. They are formed when the lower layers of sediments consist of pebbles and sands.
Limestone:- Limestone consists of mainly of a mineral called calcite. Calcite comes from the shells and skelton of tiny sea creatures. When these animals die, their shells and skeletons settle on the sea bed and form layers. These layers form limestone. Limestone is used to make cement and bricks. It is also used to extract iron from rocks containing the metal.
15. Describe about Metamorphic rocks?
' Metamorphosis ' means change . Metamorphic rocks are rocks that have gone through changes. They were originally sedimentary or igneous rocks.Deep inside the Earth, heat and pressure can bring about changes in their minerals. This changes their appearance and makes them together and harder. Metamorphic rocks are classified into four types. They are Marble, slate, Quartzite and Gneiss.
16. Define Marble?
Marble is formed when limestone, a sedimentary rock undergoes changes. It can be curved and polished easily. It is used to make statues and buildings . The Taj Mahal is make of white marbles.
17. What is slate ?
Slate is made by the metamorphosis of shale, a sedimentary rock. Slate is shiny and easily split into thin sheets. It is found in grey and other colours. It is used to make slates, black boards and roofs of buildings.
18. Define Quartzite?
Quartzite is formed by the metamorphosis of sandstone. It is used to make slates.
19. How is Gneiss forms?
Gneiss is formed by the metamorphosis of granite. It is coarse grained and has irregular bands of different colours. They often glitter because they contain shiny mineral mica.
20. What property of metamorphic rocks makes them fit to be used for buildings?
Metamorphic rocks are rocks that have gone through changes. They were originally sedimentary or igneous rocks. Deep inside the Earth heat and pressure can bring about changes in their minerals. This changes their appearance and makes them together and harder. This behaviour of metamorphic rocks makes them fit to be used for buildings.
Marble is a metamorphic rock. It can be curved and polished easily . So it is used to make slates and buildings.
Slate is also a type of metamorphic rock state. It is shiny and easily splits into thin sheets. It is used to make roofs of buildings .
Gneiss is another type of metamorphic rock. They often gliter because they contain a shiny mineral mica. Gneiss and Quartzize are also used make buildings.
21. What are these?
a. Ores:- Many minerals that make up rocks contain metals. The metal can be obtained from these rock. Rocks containing metals that can be extracted are called ores .
Iron , Aluminum or copper are obtained from their respective ores.
b. Gemstones:- Many minerals are found in the form of crystals. They are hard and can be cut and polished into beautiful stones called gemstones.
Example : Rubies, Diamonds , Sapphires and Emeralds
c. Coal:- Coal is a type of sedimentary rock. It is formed from the remains of plants that grew in swampy forests millions of years ago. When they died they got buried in the swamps.
22. How is coal formed?
Coal is a type of sedimentary rock. It is formed from the remains of plants that grew in the swampy forest millions of years ago. When they died they got buried in the swamps. Layers of mud, sand and more plants deposited on them. As more and more layers deposited, the heat and pressure in the layers below gradually changed them to form coal.
23. How is crude oil formed?
Crude oil also called petroleum, is dark sticky liquid. It was formed over millions of years from the decade remains of plants and animal died, they sank to the bottom of the sea. As the sediments built up on top, the heat and pressure changed the remains into petroleum.
24. Match the following
|Igneous Rock||Lime stone||Shiny and easily splits into thin sheets|
|Sedimentary Rock||Granite||Used to make cement and bricks|
|Metamorphic Rock||State||Very hard and used to make buildings|
|Igneous Rock||Granite||Very hard and used to make buildings|
|Sedimentary Rock||Limestone||Used to make cement and bricks|
|Metamorphic Rock||State||Shiny and easily splits into thin sheets|
25. State the importance of coal and petroleum?
Coal and petroleum are our most important fuels. Coal is used as fuel. Kerosenel is used for cooking. It is used in the the power houses to generate electricity and in factories to run machines. Petrol and diesel obtained from petroleum are used to run cars, buses and trucks.Petroleum also gives us plastics, paints , fertilizers, medicines, cosmetics and various other products.
Practice in Related Chapters
|Volcanoes, Earth Quakes and Tidal Waves|
|Plants - Increasing the Numbers|
|Food and Health|
|Safety and First Aid|
|Solids,Liquids and Gases|
|Soil Erosion and Conservation|
|Rocks and Minerals|
|Animals,Habitat and Adaptation|
|Our Skeletal System|
|Our Nervous System|
|Our Life Supports|
|Houses All Around|
|Changes in our Environment|
|Light and Shadows|
|Earth, Sun, Moon|
|Force and Energy|
|Air and Water|
|Bones and Muscles|