UNIT 3

In Search of Earth's Secrets 

Q. Write the features of Core

Central part of the Earth.

■ From 2900 km to 6371 km.

◻️Two parts- outer core (molten state), inner core (solid state)

Q. Why inner core is also called NIFE?

📚 It is mainly made up of nickel (Ni) and iron (Fe),that is why it is also called NIFE.

Q. The inner core of the earth remains as solid. Why?

📚 Due to the high pressure prevailing at the centre, the inner core is in a solid state.

Q. Explain the terms Lithosphere and Asthenosphere.

📚 The crust and the upper part of the mantle together are known as lithosphere.

📚 The part beneath the lithosphere, where the materials exist in a partially molten state is known as lithosphere. 

Q. Write short note- Lithosphere.

📚 The crust and the upper part of the mantle together are known as lithosphere.

📚 The lithosphere is made (lithos' means rock) of rocks.

📚 Rocks of different colours and hardness. This diversity is due to its constituents.

📚 The constituents of rocks are called minerals.

📚 More than two thousand minerals such as silica, mica, hematite, bauxite, etc have been identified on earth.

Q. Classify the rocks based on the mode of formation.

■ Igneous rocks- Formed by the molten rock material rising through the fissures in the crust

 and solidifying either on the surface of the Earth or within the crust itself.

Eg:- granite, basalt.

◻️Sedimentary rocks- Rocks undergo weathering in course of time. The debris so formed will be deposited in the low regions as layers.

📚 These materials gradually get lithified and transformed into sedimentary rocks.

Eg:- sandstone, limestone.

◻️Metamorphic rocks - When rocks undergo physical and chemical changes due to high

temperature and pressure metamorphic rocks are formed.

Eg:- marble, slate.

Q. Sedimentary rocks are also called stratified rocks. Why?

📚 The sedimentary rocks are formed in layers, so they are also known as stratified rocks.

Q. Which type of rock is prominent in Kerala?

📚 Metamorphic rocks.

Q. What is rock cycle?

📚 The rocks may not remain in their original form forever.

📚 They are subjected to several changes over time.

📚Rocks from one form to other. 

Q. What is weathering?

📚 Disintegration or decomposition of rocks is known as weathering.

Q. Make a flowchart showing different types of weathering.

👉 WEATHERING

📚 Physical/Mechanical Weathering. 

◻️The expansion and

contraction of minerals due

to the variations in temperature result

weathering. Disintegration also occurs due to the freezing of water in the fissures of rocks.

📚 Chemical Weathering. 

◻️Oxygen, carbon dioxide, water etc. react with the minerals and result in the chemical decomposition of rocks.

📚 Biological Weathering. 

◻️The plant roots penetrating into the fissures in rocks, burrowing of animals, and the decomposition of plant and animal remains lead to

weathering. Human activities such as mining and quarrying also lead to

weathering.

Q. What are the human activities that lead to the weathering of rocks?

◻️Quarrying

■ Destruction of hills

■ Minning

■ Construction of buildings. 

Q. Weathering helps humans in many ways. Write examples.

■ Minerals in rocks get extracted

■ Helps in mining

■ Causes soil formation

Q. How is soil formed?

The soil is formed by prolonged processes like weathering of rocks and decomposition of

organic matter.

Q. What are the different factors influencing soil formation?

■ Climate

■ Topography

■ Parent rocks

■ Time

■ Plants and Animals. 

Q . What are the uses of soil?

📚 Making clay pots

📚 Agriculture purpose 

📚 Making ornaments

📚 Making of bricks 

📚For construction purpose. 

Q. Write the importance of soils.

👉 Without soil there won't be any plants or animals.

👉 Soil is one of the important factors that makes life on the earth possible.

👉 The green plants absorb nutrients from the soil and prepare food with the help of sunlight.

👉 Humans and other animals consume these plants.

👉 When plants and animals die, they return to the soil.

👉 For the function of a food chain. 

Q. Soil gets depleted due to various human activities. List out some activities.

■ Deforestation. 

◻️Destruction of hills

◻️Unscientific agricultural activities.

■ Non-degradable materials like plastic cause soil pollution.

■ Overuse of chemical fertilizers that alter the structure of soil.

■ Unscientific construction and quarrying.

◻️Use of agricultural land for non-agricultural purposes.

◻️Draining wastewater into soil on a large scale.

◻️Overgrazing.

 Q. Conservation of soil is essential for the sustenance of life. Justify.

◻️Once the top soil is lost what is left behind is barren land or rocky surface.

◻️It will take thousands of years for the top soil to regenerate.

◻️Top soil is essential for the continued sprouting of life. 

◻️For this conservation is the only solution.

Q. Write different steps to conserve soil.

📚Check deforestation

📚 Terrace farming. 

📚 Crop rotation

📚 Terrace farming along hill slopes.

📚 Construction of check dams.

📚 Planting of trees.

Q . Which day we celebrate as World Soil Day? 

📚 5th December.

Q. Find out different types of soil in India and Kerala. 

👉INDIA

📚 Alluvial soil 

📚 Black cotton soils.

📚Red soils.

📚Desert soils

👉KERALA

📚Alluvial soil

📚Laterite soils

📚Black cotton soils.

📚Red soils.

📚Forest soil