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Class VII: Chapter 3 (Our Changing Earth) Question & Answer

 

Very Short Answer Questions

Q1. Define: (a) Endogenic Forces (b) Exogenic Forces (c) Lithospheric Plates
Ans 1:
(a) Endogenic Forces: Forces which are working in the interior of the earth leading to earth movements, earthquakes and volcanic eruption are known as endogenic forces.
(b) Exogenic Forces: Forces which are working on the surface of the earth leading to the erosional and depotional features of wind, water and ice are known as exogenic forces.
(c) Lithospheric Plates: The crust of the earth is broken into a number of large and small plates known as the lithospheric plates.

Q2. What is volcano? What are its types?
Ans 2: Natural openings in the earth's crust through which molten materials, rocks, ashes, gases, etc are thrown out are called 'Volcanoes'. Volcanoes are classified into three types:
(a) Active Volcanoes: These volcanoes erupt frequently and give out gases, ash, lava, etc. e.g. Mt. Etna in Italy.
(b) Dormant Volcanoes: These are also known as 'Sleeping Volcanoes'. They erupt after a very long time. E.g. Mt. Vesuvius in Italy.
(c) Extinct Volcanoes: These are also known as 'Dead Volcanoes'. They have been inactive since a very long time. E.g. Mt. Kilimanjaro in East Africa.

Q3. What do you mean by 'Focus' and 'Epicentre'?
Ans 3: Focus: The point of origin of an earthquake is called its Focus.
Epicenter: The point directly/vertically above the focus on the earth's surface is known as Epicenter.

Q4. What are meanders?
Ans 4: Curves and large bends or loops formed by rivers in the plains are known as meanders.

Q5. Define the term 'Aggradation'.
Ans 5: The process of depositing the eroded material is called aggradation.

 

Short Answer Questions

Q6. How does the process of gradation creates various landforms?
Ans 6: The surface of the earth is continuously undergoing changes. Running water, moving ice, wind and waves are the main agents of gradation which continuously wear down the land surface and carry the broken fragments which are deposited in the low lying areas.
The process of reduction of height of landform is called 'degradation'. The process of depositing the eroded material is called 'aggradation'. Aggradation and degradation are the two main ways which as continuously at work creating different landforms on the earth surface.

Q7. What do you mean by erosion? What are the main agents of erosion?
Ans 7: The removal of outer layer of rocks in the natural environment is called erosion. The main agents of erosion are water, wind and ice.

 

Long Answer Questions

Q8. Give a detailed account of the features formed by Wind, Waves and Ice.
Ans 8: The features formed by wind are as follows:
(a) Mushroom Rocks: In deserts you can see rocks in the shape of a mushroom, commonly called mushroom rocks. Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top.

(b) Sand Dunes: When the wind blows, it lifts and transports sand from one place to another. When it stops blowing the sand falls and gets deposited in low hill – like structures. These are called sand dunes.
(c) Barkhan: A crescent shaped sand dune is called a barkhan.
(d) Loess: When the grains of sand are very fine and light, the wind can carry it over very long distances. When such sand is deposited in large areas, it is called loess.

The features formed by sea waves in the coastal areas are as follows:
(a) Sea Caves: Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves.
(b) Sea Arches: When these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches.
(c) Stacks: Further, erosion breaks the roof and only walls are left. These walls like features are called stacks.
(d) Sea Cliff: The steep rocky coast rising almost vertically above sea water is called sea cliff.
(e) Beaches: The sea waves deposit sediments along the shores forming beaches.

The features formed by ice are as follows:
(a) Lakes: Glaciers carve out deep hollows. As the ice melts they get filled up with water and become beautiful lakes in the mountains.
(b) U-Shaped Valley: Formation of "U" shaped valleys, which are deep and have steep sides.
(c) Glacial Moraines: The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.

Q9. What are tectonic plates? Why do they cause tremors?
Ans 9: The crust of the earth is not in the form of a continuous plate rather in the form of broken pieces. These pieces of the earth's crust are called tectonic plates. Broadly, there are seven major plates: African Plate, Antarctic Plate, Eurasian Plate, Indo-Australian Plate, North American Plate, Pacific Plate and South American Plate.
According to the theory of continental drift, these tectonic plates are constantly moving. When these plates collide with each other, tremors or earthquakes are caused. Sudden vibration caused by the movement of lithospheric plates is called earthquake.

Q10. How are features formed by a river different from that formed by a river of Ice?
Ans 10: The features formed by a river are as follows:
(a) 'I' & 'V' shaped valley                              (b) Gorges or Canyons (deep valleys)
(c) Waterfalls, etc.                                         (d) Meanders (curves & large bends or loops)
(e) Oxbow Lakes                                          (f) Flood Plains
(g) Levees (slightly raised river banks)            (h) Delta
(i) River breakup into various streams called 'distributaries'.

The features formed by ice are as follows:
(a) ''U' shaped valley                      (b) Lakes                        (c) Glacial Moraines

The course of a river is very large in compression to that of a glacier (river of ice). A river flows from mountains, plains and forms various features before submerging into the sea. Whereas, course of a glacier is confined to the mountains only. River contains water which is in liquid form and Glaciers contain ice which is in solid/semi-liquid for, due to which the features formed are different.

Q11. Why are deltas so fertile?
Ans: A river when approaches towards its last stage of its course before submerging into the seas and oceans becomes very slow. Due to the load of sediments the river is carrying and because of the flat land, it is forced to deposit the sediments near the mouth. The river starts breaking into number of small streams known distributaries. The network of distributaries form a triangular shaped feature called delta. These deltas are most fertile areas in the course of a river. The deposition of sediments in the deltas is a continuous process making these deltas the most fertile areas. Sunderbans delta formed by the Ganga – Brahmputra river is the biggest delta and also is very fertile.

Q12. Name the erosional and depositional features found in coastal areas Explain how they are formed.
Ans: The erosional features formed by sea waves in the coastal areas are as follows:
(a) Sea Caves: Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves.
(b) Sea Arches: When these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches.
(c) Stacks: Further, erosion breaks the roof and only walls are left. These walls like features are called stacks.
(d) Sea Cliff: The steep rocky coast rising almost vertically above sea water is called sea cliff.

The depotional features formed by sea waves in the coastal areas are as follows: -
(a) Beaches: The sea waves deposit sediments along the shores forming beaches.

 

Give Reasons

Q13. Wind action is prominent in desert area. Why?
Ans 13: Wind action can be best seen in the desert areas. Features like sand dunes, Mashroom rocks, etc. are formed by the wind action. Wind acts as an agent of erosion and deposition which leads to the formations of different features.
In the deserts we don't find lot of vegetation due to which the wind flows without any disturbance or obstruction. Also, because of the lack of vegetation there is no moisture content in the soil and it is not able to hold itself and becomes very loose (sand). In a wide area with barren land the wind blows with great velocity creating new features specially in the deserts.

Q14. Meanders are formed by the rivers in plains. Why?
Ans 14: Rivers are the most important agents of degradation. As the river flows from the mountainous regions, it has great erosive power. Speed and force of water is great, during this course river does lots of erosional work. As the river enters into the plains, all of sudden the speed of flow of water is reduced to a greater extent and the river widens. In the plains river forms curves and large bends or loops called the meanders

 

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Class VII: Chapter 3 - Our Changing Earth

 

Objectives and Goals:

  • Pangaea.
  • The Continental Drift Theory.
  • The Theory of Plate Tectonics.
  • The forces active behind the changes on the earth.
  • The Lithospheric Plates.
  • The Tectonic Movements.
  • Endogenic (Internal) and Exogenic (External) Forces.
  • The Earth Movements.
  • The Volcanoes.
  • Three different types of volcanoes (i.e. Active, Dormant and Extinct).
  • Earthquakes. Instrument used to measure an earthquake.
  • The major landforms. Weathering, Erosion, Aggradations and Degradation.
  • Work of a river and features formed by a river.
  • Work of ice and features formed by ice.
  • Work of wind and features formed by wind.
  • Work of waves and features formed by waves.

 

Some important points to remember: -

  • Forces like earthquake and volcanoes occurs beneath the earth's crust.
  • Forces like weathering, erosion, etc. are responsible for the changes on the earth's surface.
  • Forces are of two types: Endogenic (Internal) and Exogenic (External) forces.

(a)    Endogenic (Internal) Forces: Forces which form mountains, plateaus, plains, rising & sinking of coastal plains, movement of continental blocks, etc. These are slow and sudden forces. Internal forces are: -

         (i)   Earth Movements

         (ii)  Earthquakes

         (iii) Volcanoes

(b)   Exogenic (External) Forces: These forces originate on earth and form new landforms on the earth's surface. External forces such as: -

          (i)   Changes in atmospheric conditions.

          (ii)  Rivers, glaciers, sea waves and winds.

 

Earth Movements:

 Earth's crust or lithosphere consists of several lithospheric plates.Surface of Earth changes as the lithospheric plates moves.Earth movements arise inside the earth.Temperature and pressure inside the earth changes causes changes on the earth's surface.

According to the theory of continental drift, the world was made up of a single continent through most of geologic time. That continent eventually separated and drifted apart, forming into the seven continents we have today. The first comprehensive theory of continental drift was suggested by the German meteorologist Alfred Wegener in 1912.

Million of year also there was a single continent named "Pangaea". Pangaea broke into pieces due to internal forces and is drifting away from each other since last almost 250 million years.Two landmasses – "Laurasia in North" and "Gondwanaland in South". Both the landmasses were separated by a shallow sea called "Tethys Sea".Size of Tethys Sea kept on decreasing due to movement of landmasses towards each other, thus, resulting in the formation of the young fold mountains "Himalayas".

 

 

Theory of Plate Tectonics:

The continental blocks or the plates are floating on mantle. They move with the change or release of pressure and temperature inside the earth.Tectonic movements are of two types:

(a)    Vertical Movement: Causes land to uplift or subside or both.

(b)   Horizontal Movement:  Formation of mountains, trenches in the sea, widening of water bodies, etc. Such movements can cause both folding and faulting of structure.

 

Folding:

Caused by compression, when blocks of landforms come closer to each other, they form wrinkles or folds on the earth's surface. E.g. the young fold mountains 'Himalayas'. These young fold mountains are formed by sedimentary rocks.

Faulting:

The structure of rocks cracks or breaks along the weaker areas due to tension, this is called faulting. This may cause upliftment and subsidence of land and can form Block Mountains. E.g. Vindhyas and Satpura hills.When a part of land subsides between two faults, it forms Rift Valley. Narmada & Tapti Rivers flow through the rift valley.

 

Earthquakes:

  • The crust of the earth has cracks in it called the 'Faults'.
  • The study of earthquake shocks and its effects is called 'Seismology'.
  • Instruments used to records the shaking of land is known as 'Seismograph'.
  • The vibrations are called Seismic Waves.Earthquake is measured from 1 to 10 on the Richter Scale.
  • The point of origin of an earthquake is called its 'Focus'.
  • The point directly/vertically above the focus on the earth's surface is known as 'Epicenter'.
  • The scientists who study earthquake is known as 'Seismologists'.

 

Effects of earthquakes:

  • Displacement of the earth's crust (uplifts and subsides).
  • Results in landslides and avalanches in mountainous regions.
  • Destruction done by earthquakes can be seen like, falling of buildings, damaged roads, communication system, etc.

 

Volcanoes:

  • Natural openings in the earth's crust through which molten materials, rocks, ashes, gases, etc are thrown out are called 'Volcanoes'.
  • Volcanoes erupt due to excessive 'heat and pressure' inside the earth.
  • The opening through which lava comes out is called 'Vent of Volcano'.
  • The funnel shaped depression at the top of the vent is called 'Crater'.
  • Around the Pacific Ocean along the belt of volcanoes called 'Ring of Fire'.
  • About 68% of volcanoes occur in this region.
  • Lava ejected by volcanoes can be thick or thin in nature.

 

Volcanoes are classified into three types: -

(a)    Active Volcanoes: These volcanoes erupt frequently and give out gases, ash, lava, etc. e.g. Around Pacific Ocean, Hawaii Islands, etc.

(b)    Dormant Volcanoes: These are also known as 'Sleeping Volcanoes'. They erupt after a very long time. E.g. Mt. Vesuvius in Italy.

(c)    Extinct Volcanoes: These are also known as 'Dead Volcanoes'. They have been inactive since a very long time. E.g. Mt. Kilimanjaro in East Africa.

 

MAJOR LAND FORMS

  • The landscape is being continuously changing away by two processes – weathering and erosion.
  • Weathering is the breaking up of the rocks on the earth's surface.
  • Erosion is the wearing away of the landscape by different agents like water, wind and ice.
  • The eroded material is carried away or transported by water, wind, etc. and eventually deposited.
  • This process of erosion and deposition create different landforms on the surface of the earth.
  • The process of reduction of height of landform is called 'degradation'.
  • The process of depositing the eroded material is called 'aggradation'.

 

Work of a River:

1.  Rivers are the most important agents of degradation.

2.  Work of the river depends on two factors: -

(a)  The volume of Water.                                     (b)  Slope of river beds.

3.  Common features formed by river while flowing through mountains: -

(a)  'I', 'V' shaped valley.                             (b) Gorges or Canyons (deep valleys)

(c)  Waterfalls, etc.

4.   Common features formed by river while flowing through plains: -

(a)  Meanders (curves & large bends or loops)      (b) Oxbow Lakes

(c)  Flood Plains                                                    (e)  Levees (slightly raised river banks)

5.   Common features formed by river when it reaches near the sea: -

(a)  River breakup into various streams called 'distributaries'.

(b)  Delta

 

Work of Sea Waves

  • The erosion and deposition of the sea waves gives rise to coastal landforms.
  • Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves.
  • When these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches.
  • Further, erosion breaks the roof and only walls are left. These wall like features are called stacks.
  • The steep rocky coast rising almost vertically above sea water is called sea cliff.
  • The sea waves deposit sediments along the shores forming beaches.

 

Work of Ice

  • Glaciers are "rivers" of ice which too erode the landscape by bulldozing soil and stones to expose the solid rock below.
  • Glaciers carve out deep hollows. As the ice melts they get filled up with water and become beautiful lakes in the mountains.
  • Formation of "U" shaped valleys, which are deep and have steep sides.
  • The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.

 

Work of Wind

  • An active agent of erosion and deposition in the deserts is wind.
  • In deserts you can see rocks in the shape of a mushroom, commonly called mushroom rocks.
  • Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top.
  • When the wind blows, it lifts and transports sand from one place to another.  When it stops blowing the sand falls and gets deposited in low hill – like structures. These are called sand dunes.
  • When the grains of sand are very fine and light, the wind can carry it over very long distances.
  • When such sand is deposited in large areas, it is called loess. A large deposit of loess is found in China.

 

 

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CLASS VII: CHAPTER 2 - INSIDE THE EARTH (QUESTION & ANSWER)

 

Very Short Answer Questions

Q1. Define: (a) Crust (b) Mantle (c) Core (d) Rocks (e) Ore (f) Lava (g) Magma
Ans 1:
(a) Crust: The outermost and thinnest layer of Earth is known as Crust.
(b) Mantle: The middle layer of Earth between Crust and Core is known as Mantle.
(c) Core: The innermost layer, forming the metallic centre of the Earth is known as Core.
(d) Rocks: All solid materials of the earth's crust, whether hard or soft, that make up the earth's crust are called Rocks.
(e) Ore: A rock in which a particular mineral is found in large percentage is called an ore.
(f) Lava: The red molted rock material erupting from the earth in the form of a volcano is known as Lava.
(g) Magma: The molted rock material inside the earth is known as Magma.

 

Q2. What are minerals?
Ans 2: Rocks form the solid mass of the earth's crust. The rock forming materials are known as "Minerals".

 

Long Answer Questions

Q3. Explain the classification and characteristics of rocks.
Ans 3:  Rocks have different colours, mineral composition, hardness, etc. and according to their formation, rocks can be classified into three categories: -
1. Igneous Rocks
2. Sedimentary Rocks
3. Metamorphic Rocks

1. Igneous Rocks: The word 'Igneous' is derived from Latin word "Ignis" meaning "Fire". This is also called Primary rock. These are the first rocks to be formed and are known as the ancestors of all the rocks. Igneous rocks are the hardest rocks available and it is formed by cooling and solidification of the Lava coming out from the interior of the Earth's interior. E.g. Granite, Basalt, etc. Igneous rocks are of two types:
(a) Solidification of rocks below the earth's surface is known "Intrusive rocks".
(b) The magma which reaches the earth's surface and gets solidified is known as "Extrusive Rocks".

Features of igneous rocks are: -
1. These rocks do not form layers.
2. They contain crystals of varying sizes.
3. They do not contain fossils.

2. Sedimentary Rocks: The word 'Sedimentary' is derived from Latin word "Sedimentum" meaning "Settle Down". Particles that form a sedimentary rock by accumulating are called sediments. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation.

Features of Sedimentary rocks are: -
1. They are layered, called stratified rocks.
2. They do not contains crystals.
3. They contain fossils embedded in them.
4. They are rich in coal and petroleum deposits.
5. Examples of Sedimentary rocks are: - Sandstone, Clay, Limestone, etc.
6. 70% of the total earth's surface is dominated with these rocks.

3. Metamorphic Rocks: The word 'Metamorphic' is derived from Greek word "Metamorphose" meaning "Change of Form". When igneous or sedimentary rocks are subjected to great heat or pressure, the original character and appearance of the rock change into a new form. Thus, these rocks are formed by the alteration of other rocks. E.g. graphite, slate, Marble, etc.

Features of metamorphic rocks are: -

1. They are hard in nature.
2. Valuable minerals like gold & silver are found in these rocks.

3. They do not contain fossils.

4. Takes a long time to form.

 

 Q4. Describe the rock cycle with a suitable diagram.

Ans 4:  Rocks undergo a cycle of transformation. Change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Hence, this cycle of change from one type of rock to another is called 'rock cycle'.

Rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

 

Q5. What is the usefulness of rocks and minerals to us?

Ans 5:  Rocks and minerals are very useful to mankind. Following are the usefulness of rocks and minerals:
1. Different vegetations.
2. Different types of minerals for industries.
3. Different rock materials for construction purposes.
4. Different chemicals for medicine and fertilizer industries.
5. Source of fuels like coal and crude oil.
6. Source of precious stones like, gold, silver, etc.

 

Q6. Why do we get both fossils and fossil fuels primarily in the sedimentary rocks?
Ans 6:   Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. Fossil fuels are fuels formed by natural processes such as decomposition of buried dead plants and animals.
Amongst the three major types of rock, fossils are most commonly found in sedimentary rock. Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants. Sedimentary rocks are formed by the deposition of sediments layer by layer making it easy to contain fossils and fossil fuels. Sedimentary rocks are soft rocks, thus it dose not destroy the fossils and in a longer run we get the fossil fuels like coal and petroleum products, which are very important for human life.

 

Q7. All the minerals are exhaustible. What would happen if coal, petroleum and few other minerals get exhausted completely? What effect it would have on our life?
Ans 7:  Coal, Petroleum and other minerals are non-renewable resources, they get exhausted when put to use. It takes millions of years to form these minerals. In todays world we cannot imagine human life without coal and petroleum products. coal and petroleum products are used in household sector, industrial sector, electrical sector, transportation sector, etc. making our life easy. But the usage of these products are increasing very fast day-by-day and if we are not serious very soon these minerals will be exhausted.
Human life will be effected very badly if coal and petroleum products get exhausted completely. If such a situation occurs we won't get proper electricity, transportation will be a great problem, all household items will become very costly, Food items will not be available on time, in short the survival of human life will be very difficult.

 

Q8. Differentiate between: (a) Crust and Mantle (b) Igneous and Sedimentary Rocks
Ans 8:
(a) Crust and Mantle

 

 

 

 

 

 

 

 

 

 

 

 

(b) Igneous and Sedimentary Rocks

                    

 

 

 

 

 

 

 

 

 

 

 

 

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Class VII: Chapter 2 - Inside the Earth

Objectives and Goals:

  • The interior of the earth.
  • The three different layer of the earth (i.e. Crust, Mantle and Core).
  • Differences between rocks and minerals.
  • The classification and characteristics of rocks (i.e. Igneous, Metamorphic and Sedimentary Rocks).
  • The "Rock Cycle".
  • The usefulness of rocks.

 

Some important points to remember:

  • Lithosphere (outer part of earth's structure) was formed 5 billion years ago. 
  • Geologists are the scientists who study the earth, its structure and substances. 
  • Petrology is the science which studies rocks and its formations. 
  • Fossils – remains of dead plants and animals are called fossils trapped in the layers of rocks. 
  • Ore – a rock in which a particular mineral is found in large percentage is called an ore. 
  • Plates – large blocks of earth's crust which are moving. 
  • Magma – it is molten rock material inside the earth. 
  • Rock cycle – rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

 

The radius of Earth is 6371 kms.  Earth's interior is broadly divided into three layers: -

1. Crust – Forms only 0.5% of the total Earth's volume.

2. Mantle - Forms only 16% of the total Earth's volume.

3. Core - Forms only 83% of the total Earth's volume.

 

CRUST:

  • Its is also called SIAL (Silica & Aluminum)
  • The outermost and thinnest layer of Earth.
  • It consists of lightest materials and its density is lowest.
  • Average thickness varies from 5 to 8 kms under the ocean floors and 35 kms under the continental masses.
  • Broken in large continental blocks called "Plates".
  • Lower part of Crust (oceanic crust) is known as SIMA (Silica & Magnesium).

 

MANTLE:

  • Layer located under the Crust is called "Mantle".
  • Its thickness is about 2900 kms.
  • This layer is in partially molted form.
  • Lithosphere plates (Crust) floats on this layer.
  • Layer is divided into two – Upper and Lower Mantle. The upper mantle is in solid form, whereas lower mantle is in semi-molten form.
  • Average temperature: Upper Mantle – 870 degree Celsius and Lower Mantle – 2200 degree Celsius.
  • This layer is made up of Iron, Magnesium and Silica.

 

CORE:

  • The innermost layer, forming the metallic centre of the Earth.
  • Core of the Earth is like a dense magnetic ball of minerals (Iron & Nickel). Hence, it is also called NIFE (NI – Nickel & Fe – Ferrous Magnesium i.e Iron).
  • Temperature increases at the rate of 1degree Celsius for every 32 meters of depth.
  • This layer is divided into two:

            (a) Outer Core: It is so hot that even metal also melts. Temperature is around 2200 degree Celsius.

            (b) Inner Core: Here the temperature is around 5000 degree Celsius.  Pressure is maximum in this layer.

 

MATERIAL OF THE EARTH'S CRUST

Earth's crust is composed of rocks and minerals. All solid materials of the earth's crust, whether hard or soft, that make up the earth's crust are called Rocks.

 

Characteristics of Rocks:

  • They are made up of one or more minerals.They don't have a definite chemical composition.There are broadly 12 rocks forming minerals.
  • Rocks form the solid mass of the earth's crust.
  • The rock forming materials are known as "Minerals".
  • Minerals are chemical substances found in nature. They have definite chemical composition and physical characteristics. Any variation in their proportion gives rise to a different mineral.
  • Rocks containing minerals gives us metals like Copper, Iron, Gold, etc.

 

Rocks have different colours, mineral composition, hardness, etc. and according to their formation, rocks can be classified into three categories: -

1.  Igneous Rocks

2.  Sedimentary Rocks

3.  Metamorphic Rocks

 

1.  IGNEOUS ROCKS

The word 'Igneous' is derived from Latin word "Ignis" meaning "Fire".

  • This is also called Primary rock. These are the first rocks to be formed. These are ancestors of all the rocks.
  • Igneous rocks are the hardest rocks available and  it is formed by cooling and solidification of the Lava coming out from the interior of the Earth's interior. E.g. Granite, Basalt, etc.
  • Solidification of rocks below the earth's surface is known "Intrusive rocks".
  • The magma which reaches the earth's surface and gets solidified is known as "Extrusive Rocks".

Features of igneous rocks are: -

  • These rocks do not form layers.
  • They contain crystals of varying sizes.
  • They do not contain fossils.

 

2.  SEDIMENTRY ROCKS

  • The word 'Sedimentary' is derived from Latin word "Sedimentum" meaning "Settle Down".
  • Particles that form a sedimentary rock by accumulating are called sediments.
  • Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation.

Features of igneous rocks are: -

  • They are layered, called stratified rocks.
  • They do not contains crystals.
  • They contain fossils embedded in them.
  • They are rich in coal and petroleum deposits.
  • Examples of Sedimentary rocks are: - Sandstone, Clay, Limestone, etc.
  • 70% of the total earth's surface is dominated with these rocks.

 

3.  METAMORPHIC ROCKS

  • The word 'Metamorphic' is derived from Greek word "Metamorphose" meaning "Change of Form".
  • When igneous or sedimentary rocks are subjected to great heat or pressure, the original character and appearance of the rock change into a new form. Thus, these rocks are formed by the alteration of other rocks. E.g. graphite, slate, Marble, etc.

Features of metamorphic rocks are: -

  • They are hard in nature.
  • Valuable minerals like gold & silver are found in these rocks.
  • They do not contain fossils.
  • Takes a long time to form.

 

ROCK CYCLE

Change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Hence, this cycle of change from one type of rock to another is called 'rock cycle'.

Rock Cycle: Rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

             

 

ROCKS PROVIDE US:

  • Different vegetations.
  • Different types of minerals for industries.
  • Different rock materials for construction purposes.
  • Different chemicals for medicine and fertilizer industries.
  • Source of fuels like coal and crude oil.Source of precious stones like, gold, silver, etc.

 

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CLASS VII: CHAPTER 1 - OUR ENVIRONMENT (QUESTION & ANSWER)

 

Very Short Answer Questions

Q1.  Define the term Environment.

Ans: The immediate natural surroundings of man is called environment. E.g.: Plants, Air, Water, Landforms, Wildlife, etc.......

The word Environment has been derived from a French word "Environner" which means "Neighborhood".

 

Q2.  What do you mean by Ecology?

Ans: The Science with studies the relationship between living and non-living environment is termed as Ecology.

 

Q3.  Why is an ecosystem considered as the central feature of ecology?

Ans: The Interrelation between plants and animals in the natural environment is called Ecosystem.

The Science with studies the relationship between living and non-living environment is termed as Ecology. Thus, Ecology helps us to understand how a large variety of life forms depend upon the non living things and are influenced by their interaction with their environment.

 

Short Answer Questions

Q4.  What are the different components of the environment?

Ans: Different components of the environment are:

(a) Natural Environment            (b) Human Environment        (c) Human Made Environment

Q5. Why is lithosphere important?

Ans: The hard outermost solid layer of the earth which is made up of rock material is called crust. This solid crust of the earth is called Lithosphere. On this lithosphere we find different landforms such as the mountains, plateaus and plains. It provides us land where we live and also, it is a great source of vegetation, wildlife and mineral wealth. The crust is covered by a thin layer of soil which is of great importance for life. Lithosphere provides us the three basic necessities of life, i.e. Food, Cloth and Shelter.

 

Q6.  Define atmosphere. Why is it important?

Ans: The layer of air around us is called Atmosphere. Following is the importance of atmosphere: -

(a)    It gives us life giving gases like oxygen for breathing of animal kingdom and carbon dioxide is inhaled by plant kingdom.

(b)   It has Ozone layer which protects us from the harmful ultraviolet rays of the sun.

(c)    There are tiny dust particles in the atmosphere which helps in the formation of the rain droplets.

(d)   It acts as a blanket which prevents the earth from becoming too hot during day and too cold during night.

(e)    It protects us from falling meteors and other cosmic dusts. They burn when coming in contact with the atmosphere.

(f)    Presence of gases, dust particles and water vapours lend colours to the sky.

 

Long Answer Questions

Q7.  What efforts must be made to protect the environment?

Ans: Following are some of the efforts which must be made to protect the environment: -

(a)     Encourage / motivate others to be more sensitive towards environment.

(b)     Plant more trees (Aforestation)

(c)    Protest / control Deforestation.

(d)    Reduce, Reuse, Recycle.

(e)     Conserve every drop of water.

(f)     Cut Energy Consumption.

(g)     Support Climate Change Initiatives. E.g. reducing CO2 emissions

(h)     Buy Energy-efficient and Eco-friendly electrical appliances.

(i)      Drive Less and Drive Smart.

 

Q8.  "The environment gives us life and protection in various ways and maintain balance on its own". Enlist the human activities that cause imbalance in the environment.

Ans: Following are few of the human activities that have caused imbalance in the environment: -

(a)     Deforestation

(b)     Overgrazing

(c)     Pollution (Air, Water, Land and Noise)

(d)    Casual and careless attitude towards the environment.

(e)     Destroying the animal habitats

(f)     Hunting

(g)     Urbanization

(h)     Industrialization

(i)      Overpopulation

 

Q9.  Biosphere is the right combination of the three sphere or realms – Atmosphere, Lithosphere and Hydrosphere. Do you think that the biosphere can exist in the absence of anyone of them? Give reason for your answer.

Ans. Plant and animal kingdom together make Biosphere or the living worlds. It is a narrow zone of the Earth where Air (Atmosphere), Water (Hydrosphere) and Land (Lithosphere) interact with each other to support life.

There will be no existence of biosphere incase any one of the three sphere or realms is missing.

For example, to survive a human being requires oxygen to breathe (i.e Atmosphere), food cloth and shelter, the three basic necessities of life are provided by the Lithosphere and without water there is no survival.

Thus, we can understand that all the three spheres are equally important for the existence of life or the Biosphere.

 

Q10. We, the humans are an integral part of the environment but we are a bit different from other creatures. How? What makes us different?

Ans. There are a number of different things that make humans different from other creatures. Human beings adapt themselves to the natural environment by making modifications in their food, cloth and shelter. They also modify their natural environment to suit their social, biological, cultural and economic needs.

The early human beings slept on trees and caves, they used to roam around in search of food as that of other creatures but with the passage of time, with the help of their mind, thinking skills, ability, knowledge, hard work, etc. they have changed themselves drastically. Now, the modern man is far more organized, skilled, well mannered and cultured. They live in houses, eat cooked food, travel from one place to another by various means of transportation, etc.

The biggest difference is that the humans have the ability to create but in case of animals or other creatures, they cannot create. They must depend on whatever is available around them to survive.

 

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CLASS VII (PROJECT GUIDELINES)

 

Project Topic                           :      OUR ENVIRONMENT

Software Used                         :       MS POWERPOINT

 

Important: Project should be prepared only on the basis of the educational field trip which was organized on 27 April 2014 (Sunday).

 

GUIDELINES (SOCIAL SCIENCE - GEOGRAPHY):

1.   Students will highlight all the details related to the environment which they have seen, noticed, observed, felt during the educational field trip organized on 27 Apr 2014.

2.   Student needs to explain role of human beings in the construction or destruction of the environment.

3.   Add photographs to your presentation to highlight the important phases of the trip.

 

GUIDELINES (ENGLISH):

1.   Presentation, delivering and briefing the topic as per the slides.

2.   Uses of language and Sentence Formation.

3.   Overall content.

 

GUIDELINES (COMPUTER SCIENCE):

1.   Students will prepare a documentation of minimum of 15 slides.

2.   Document must be formatted using various formatting options.

3.   Animation effects should be given to all the slides.

4.  Proper clip art, word art and all formatting should be done.

5.  Use of Auto shapes i.e., Banners, Call outs, etc. should be made to make to make presentation attractive.

6.  Rehearse Timings should be given to the presentation.

7.  You can also give Sound (Audio) and Video files to your presentation.

8.  Flow charts can be projected to explain sequence if needed.

9.  The Presentation should be typed using proper Case as needed and should summarize the entire plan of trip.

 

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