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Rocks - introduction and importance - class-VIII

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Tick the correct answer.
Rocks which contain fossils are ______________.

  1. Sedimentary rocks

  2. Metamorphic rocks

  3. Igneous rocks

  4. None of the above


Correct Option: A
Explanation:

Sedimentary rock is only rock which contain fossils.
Igneous rocks form from molten rock, and rarely have fossils in them. Metamorphic rocks have been put under great pressure, heated, squashed or stretched, and fossils do not usually survive these extreme conditions. Generally it is only sedimentary rocks that contain fossils.

Tick the correct answer.
The rock which is made up of molten magma is?

  1. Igneous

  2. Sedimentary

  3. Metamorphic

  4. None of the above


Correct Option: A
Explanation:

Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava.

Gypsum is used in _______ industry.

  1. Textile

  2. Food

  3. Construction

  4. None of these


Correct Option: C
Explanation:

Gypsum Products and Properties as a Building Material for ConstructionGypsum is one of the widely used construction material mainly in interior designing. Gypsum is used as surface materials. Its application is prominent in wall and ceiling construction.

Lithification is a process of formation of

  1. minerals

  2. rocks

  3. plates

  4. none of these


Correct Option: B
Explanation:

Lithification is the process by which sediments combine to form sedimentary rocks. Compaction is a consolidation of sediments due to the intense pressing weight of overlying deposits. With compaction, sediment grains get squished together, reducing the size of the original pore space that divided them.

Plaster of Paris is prepared by 

  1. Rocky salts

  2. Salts

  3. Sugar

  4. Gypsum


Correct Option: D
Explanation:

Plaster of paris originally was made from the extensive gypsum deposits of Montmartre in Paris.

Plaster of paris, consists of a fine white powder (calcium sulfate hemihydrate), which hardens when moistened and allowed to dry. Known since ancient times, plaster of paris is so called because of its preparation from the abundant gypsum found near Paris.

The ___________ are the primary source of all other rocks.

  1. sedimentary rocks

  2. igneous rocks

  3. metamorphic rocks

  4. none of these


Correct Option: B
Explanation:

The igneous rocks are called primary rocks because these were originated first of all rocks during the formation of the upper crust of the earth on cooling, solidification, and crystallization of hot and liquid magmas after the origin of the earth. Thus, all the subsequent rocks were formed, whether directly or indirectly, from the igneous rocks in one way or the other.

A rock formed after evaporation of water is __________.

  1. Plaster of Paris

  2. Gypsum

  3. Both A and B

  4. None of these


Correct Option: B
Explanation:
  • Rocks formed after evaporation of water are called evaporites. Gypsum is an example of evaporites.
  • Plaster of Paris is manufactured from gypsum and thus it is a secondary product hence cannot be the right answer here.
  • Thus option B ie gypsum is the right answer.

Which of the following rocks is formed by the cooling of molten rock?

  1. shale

  2. sandstone

  3. granite

  4. limestone


Correct Option: C
Explanation:
  • Rocks formed by the cooling of molten rock are called igneous rocks. Among the given options only granite is an igneous rock while rest 3 are sedimentary ricks.
  • Hence option C is correct.

The rock which is made up of molten magma is ________.

  1. igneous

  2. sedimentary

  3. metamorphic

  4. none of these


Correct Option: A
Explanation:

The word igneous has been derived from a Latin word 'ignis', meaning thereby fire. The igneous rocks are formed due to cooling, solidification, and crystallization of hot and molten materials known as magmas and lavas. They were originated first of all the rocks during the formation of the earth.

Rocks which mostly contain fossils are

  1. sedimentary rocks

  2. metamorphic rocks

  3. igneous rocks

  4. none of these


Correct Option: A
Explanation:

Among 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 remains.

Rock salt and gypsum are ___________ formed sedimentary rocks.

  1. Chemically

  2. Mechanically

  3. Physically

  4. All of these


Correct Option: A
Explanation:

Chemical sedimentary rocks are formed by the precipitation of minerals from water. Precipitation is when dissolved materials come out of water. They are typically made up of the minerals halite (calcium chloride, or rock salt) and gypsum (calcium sulfate).

Gold, petroleum and coal are examples of ____________.

  1. Rocks

  2. Minerals

  3. Fossils

  4. Liquid


Correct Option: B
Explanation:

B. Minerals

Native gold is an element and a mineral. It is highly prized by people because of its attractive color, resistance to tarnish, and its many special properties - some of which are unique to gold. Its rarity, usefulness, and desirability make it command a high price. 

The term mineral is sometimes used in reference to natural earth (non-living) resources, and thus, in a non-scientific sense, petroleum resources are mineral resources and deposits of petroleum are often called mineral deposits. Coal, sands, gravel, and such would also be considered a mineral resource in this particular usage, even though coal is a rock, not a mineral, and the others are mixes of multiple minerals and/or rocks and not, strictly speaking, minerals.

Where are mushroom rocks formed?

  1. Deserts

  2. River valleys

  3. Glaciers

  4. None of these


Correct Option: A
Explanation:

Mushroom rocks are formed in deserts. It is an erosional landform of arid regions. The mushroom rocks have a broad upper part and narrow base resembling an umbrella. The erosive power of wind is very high at a certain height from the ground level. The resistant rocks take the shape of a mushroom having large top and a small neck.

Which of the following is a non-metallic mineral?

  1. Bauxite

  2. Magnesium

  3. Gypsum

  4. Manganese


Correct Option: C

Which of the following rock is formed from molten lava?

  1. Igneous rock

  2. Sedimentary rock

  3. Metamorphic rock

  4. Sand stone


Correct Option: A
Explanation:

Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Igneous rocks occur in a wide range of geological settings: shields, platforms, extended crust, basins, and oceanic crust.

The Maharashtra plateau and the Sahyadris are formed from which rock?

  1. Metamorphic rocks

  2. Igneous rocks

  3. Sedimentary rocks

  4. Lime stone


Correct Option: B

Marble belong to _______.

  1. Metamorphic rock

  2. Sedimentary rock

  3. Igneous rock

  4. Volcanic rock


Correct Option: A

Which rock is also called the primary rock?

  1. Igneous rock

  2. Metamorphic rock

  3. Sedimentary rock

  4. None of the above


Correct Option: A
Explanation:

Igneous rocks are known as primary rocks as they are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.

All other rocks are derived from them, so they are also called as parent rock.

Choose the correct answer form the alternatives given.
Which of the following mountains has oldest rocks in India ?

  1. Aravalli's

  2. Himalayas

  3. Diwalis

  4. None


Correct Option: A
Explanation:

The Aravalli  range are the oldest fold mountains in India. The northern end of range continues as isolated hills and rocky ridges into Haryana state, ending in Delhi. The famous Delhi Ridge is the last leg of the Aravalli Range, which traverses through  South Delhi and terminates into Central Delhi
where Raisina hill is its last extension. It is one of the world's oldest mountain ranges. 

The rocks on which the soils are formed consist of stones, clay and sand particles. It is known as Regolith, in the beginning of which, ________ was/were there.

  1. Only minerals

  2. Air

  3. Organic substances

  4. Water


Correct Option: C
Explanation:

Regolith is a region of loose unconsolidated rock and dust that sits atop a layer of bedrock. On Earth, regolith also includes soil. It includes dust, soil, broken rock, and other related materials. It is present on Earth, the Moon, Mars, some asteroids, and other terrestrial planets and moons.

Rock wastes have been used in ___________________.

  1. Formation of medicines.

  2. Manufacturing of various articles.

  3. Formation of buildings.

  4. None of these


Correct Option: B

Soils are derived from weathering of 

  1. minersal

  2. rocks

  3. forest

  4. none of these


Correct Option: B
Explanation:

Weathering is the name given to the process by which rocks are broken down to form soils. Rocks and geological sediments are the main parent materials of soils (the materials from which soils have formed).

Most of the Marble rocks are located in the state of _________.

  1. Madhya Pradesh.

  2. Uttar Pradesh.

  3. Andhra Pradesh.

  4. Arunachal Pradesh.


Correct Option: A
Explanation:

Most of the Marble rocks are located in the state of Madhya Pradesh.

Rocks which are formed by the solidification of lava, are________.

  1. Sandstone

  2. Limestone

  3. Granites

  4. Basalts


Correct Option: D

Rocks are the economic significance because _________________.

  1. They provide soils.

  2. They provide metals.

  3. They provide minerals.

  4. All of these


Correct Option: D
Explanation:
  • Rocks are the parent material for soil.
  • Rocks are also found in form of ores which serve as a source of various metals.
  • Rocks are the source of various minerals like phosphates and nitrates.
  • Hence all are correct.

Fossil fuels are obtain from _____________.

  1. mineral ores

  2. rocks

  3. water

  4. none of these


Correct Option: B
Explanation:
  • Fossil fuels are obtained from sedimentary rocks and are formed under extreme temperature and pressure conditions.
  • When the fossil sediments get compressed into the rocks, with passing time there is the gradual decay of the fossils under extreme temperature and pressure which converts fossils into fossil fuels deep inside.

The earth is said to be _________ million years old.

  1. 4700

  2. 5000

  3. 5015

  4. 5014


Correct Option: A
Explanation:
  • By dating the rocks in Earth's crust, as well as the rocks in Earth's neighbours, such as the moon and visiting meteorites, scientists have calculated that Earth is 4500 million years old.
  • Option A is closest, thus it is correct answer.

Rock cycle is a continuous chain through which  ___________________.

  1. old rock transforms into new rock

  2. new rock transforms into old rock

  3. weathering of rock happens

  4. none of these


Correct Option: A
Explanation:

Rocks do not remain in their original form for long but may undergo transformation. Rock cycle is a continuous process through which old rocks are transformed into new ones.

The igneous rocks are formed due to ____________.

  1. plate tectonic

  2. volcanic acitivity

  3. weathering

  4. none of these


Correct Option: B
Explanation:

Igneous rocks are of two types, extrusive and intrusive. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate.

The rock cycle is the process pass through formation of _______________.

  1. Sedimentary rock

  2. Metamorphic

  3. Igneous

  4. All of the above


Correct Option: D
Explanation:
  • Rock cycle is the transition of rocks of 3 basic types viz igneous, sedimentary and metamorphic into each other in a cyclic manner.
  • Primary rock is an igneous rock which is formed after solidification of lava. It may then get eroded and settled as various layers to form sedimentary rocks. The sedimentary rocks get metamorphosised under high pressure and temperature beneath the earth crust which forms metamorphic rocks.
  • Finally, all types of rocks may get subducted deep inside the earth were under extreme temperatures they get melted leading to the formation of liquid magma and the cycle repeats.
  • Thus all options are part of this cycle and option D is correct.
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