Grade-8, SST, Natural Resources - Land, Soil and Water

 

                                 EXERCISES

1. Fill in the blanks with appropriate words.

(a) Plateaus are also called tablelands.

(b) The highest density of population is found in the plains.

(c) Leaching is the process where minerals in the soil are dissolved by rainwater and drained off.

(d) Black cotton soil is also called regur.

(e) Disposal of sewage and industrial waste are major sources of water pollution.

 

2. Choose the correct answer.

(a) One of these is an alluvial soil:

(1) khadar.

(ii) red soil.

(iii) laterite.

(iv) regur.

Answer- (i) khadar - Alluvial soils are formed from deposits of silt and clay carried by rivers. Khadar is a type of alluvial soil found in newer river deposits.

 

(b) The black lava soil of the Deccan Plateau is best for the cultivation of

(i) rice.

(ii) tea.

(ii) cotton.

(iv) wheat.

Answer- (iii) cotton - Black lava soil, also called regur, is known for its high iron content and is ideal for cotton cultivation.

 

(c) The most densely populated region amongst the following is the

(i) Deccan Plateau.

(ii) Ganga Plain.

(iii) Andaman Islands.

(iv) Sub-Himalayan region.

Answer- (ii) Ganga Plain - The Ganga Plain is one of the most fertile and densely populated regions in India due to the rich alluvial soil deposited by the Ganga and Brahmaputra rivers.

 

(d) One of these does not help in soil conservation:

(i) contour farming.

(ii) over-cultivation.

(iii) growing forest.

(iv) crop rotation.

Answer- (ii) over-cultivation - Over-cultivation depletes soil nutrients and organic matter, reducing fertility. Contour farming, growing forests, and crop rotation are all methods that help conserve soil.

 

(e) The percentage of fresh water on earth:

(i) 2.7.

(ii) 21.

(iii) 7.2

(iv) 29

Answer- (i) 2.7 - Only a small percentage, approximately 2.7%, of Earth's water is fresh water. Most of it is stored in glaciers and ice caps.

 

3. Match column.

(a) alluvial soil (b) laterite soil (c) black soil (d) red soil (e) sandy soil (f) Mountain soil

(i) Karnataka  (ii) Rajasthan  (iii) Himalayas  (iv) Deccan Plateau (v) Ganga Plain (vi) Western Ghats

Answer

(a) alluvial soil – (v) Ganga plains (b) laterite soil -(vi) Western Ghats  (c) black soil - (iv) Deccan Plateau (d) red soil - (i) Karnataka  (e) sandy soil - (ii) Rajasthan  (f) Mountain soil - (iii) Himalayas

 

4. Write true or false. Correct the false sentences in your notebook.

(a) Alluvial soil is found in northern India. 

True. Alluvial soil is primarily found in the plains of northern India formed by the deposits of rivers like Ganga and Brahmaputra.

(b) The Deccan Plateau is rich in minerals. 

True. The Deccan Plateau is known for its rich mineral deposits, including iron ore, manganese, and bauxite.

(c) Laterite soil is more fertile than alluvial soil. 

False. Alluvial soil is generally considered more fertile than laterite soil due to its higher content of organic matter and minerals. Laterite soil can be less fertile because of heavy rainfall washing away nutrients.

(d) Contour farming is done to save soil erosion. 

True. Contour farming is a technique where plowing and planting are done across a slope following its elevation, creating steps that slow water flow and prevent soil erosion.

(e) Black soil of India is good for wheat cultivation.

False. Black soil, also called regur, is ideal for cotton cultivation due to its high clay content and ability to retain moisture. Wheat prefers well-drained soil, which black soil isn't known for.

 

5. Answer the following questions in one or two sentences. 

(a) Name the three major land features.

Answer- The three major land features are mountains, plateaus, and plains.

(b) Name any two plateaus from Asia.

Answer- Two plateaus in Asia are the Tibetan Plateau and the Deccan Plateau.

(c) What is leaching?

Answer- Leaching is the process where rainwater dissolves and carries away minerals from the upper layer of soil.

(d) What is humus? 

Answer- Humus is the dark, decomposed organic matter found in soil, rich in nutrients and essential for plant growth.

(e) What are the different types of soils found in India? Which soil is good for cotton cultivation in India?

Answer- India has various soil types like alluvial (river plains), laterite (high rainfall areas), black (Deccan Plateau, good for cotton), red (central and southern India), sandy (deserts), and mountain soil.

 

6. Answer the following questions in four or five sentences.

(a) Why are mountains important?

Answer- Mountains are crucial for our planet's health. They act as giant water towers, storing snow and glaciers that melt and feed rivers throughout the year. They also influence weather patterns, blocking winds and creating rain shadows on one side while bringing precipitation to the other. Additionally, mountains are rich in mineral resources and provide habitats for unique plants and animals.

 

(b) Explain how most of the plains were formed. Give examples and write about any one plain.

Answer- Most plains are formed by the deposition of sediments carried by rivers over millions of years. Floods wash away soil particles from mountains and plateaus, depositing them in the lowlands. These sediments gradually accumulate, forming vast fertile plains. Examples include the Indo-Gangetic Plains in India formed by the Ganga and Brahmaputra rivers, and the Amazon Basin in South America. The Indo-Gangetic Plains are one of the most densely populated regions due to their rich alluvial soil, ideal for agriculture.

 

(c) What do you understand by soil profile?

Answer- A soil profile is a vertical section of the soil, revealing distinct layers with different characteristics. These layers are formed due to weathering, decomposition, and the movement of water and minerals. The top layer (O horizon) is rich in organic matter (humus). The A horizon below it is fertile and contains minerals leached from the top layer. The B horizon has accumulated minerals, and the C horizon is the weathered parent rock. The bottommost layer (R horizon) is the unweathered bedrock.

 

(d) Give an account of any two soils found in India.

Answer- Here's an account of two common soils in India:

• Alluvial Soil: This fertile soil is found in river valleys and deltas. It's rich in organic matter and minerals deposited by floods, making it ideal for agriculture. Crops like wheat, rice, sugarcane, and pulses are grown extensively in these regions.
• Black Soil (Regur): This dark-colored soil is found in the Deccan Plateau and is known for its high clay content and ability to retain moisture. It's rich in iron and calcium, making it perfect for cotton cultivation. However, this soil can be sticky when wet and become challenging to work with.

 

Additional Questions

Land:

Q.1 What are the three main forms of land on Earth, and how are they useful to humans?

Answer- Three main forms of land: Mountains (highest regions, source of rivers, minerals, affect climate), Plateaus (elevated plains, store minerals, suitable for some crops), Plains (flat, fertile areas, good for agriculture and transportation).

 

Q.2 Describe the land-use pattern and the factors affecting it.

Answer- Land-use pattern: How land is used for various purposes (agriculture, housing, mining, etc.). Factors affecting it include physical factors (soil, climate, topography, minerals, water) and human factors (population, technology)

 

Q.3 Explain the different types of soil found in India and their characteristics.

Answer- Soil types in India:

• Alluvial soil (river basins, fertile due to yearly silt deposits)
• Laterite soil (reddish, formed in hot & wet regions, less fertile)
• Black soil (north-western Deccan Plateau, rich in iron, good for cotton)
• Red soil (weathered igneous rocks, high iron content, found in central and southern India)
• Sandy desert soil (porous, low in organic matter, can be cultivated with irrigation)
• Mountain soil (thin, not very fertile, suitable for specific crops with terracing)

Q.4 How can human activities lead to land degradation?

Answer- Human activities and land degradation: Encroachment, construction, overgrazing, excessive use of pesticides/fertilizers can lead to landslides, pollution, erosion, desertification, and loss of forest cover.

 

Soil:

Q.5 What is soil, and what are the different layers of a soil profile?

Answer- Soil definition: Combination of loose, weathered rock particles, minerals, and organic matter found on Earth's surface. Richness depends on parent rock and humus (decayed plant material).

Soil profile layers:

• O horizon (surface layer with humus and plant roots)
• A horizon (rich in humus, minerals leached from above)
• B horizon (little humus, collects leached minerals)
• C horizon (weathered parent rock)
• R horizon (parent rock)

 

Q.6A How long does it take to form a centimetre of soil?

Answer- Soil formation time: Hundreds of years to form a centimetre of soil.

 

Q.6B What are some ways to conserve soil?

Answer- Soil conservation methods: Growing forests (shelter belts), terracing/contour farming on slopes, avoiding excessive fertilizers/pesticides, leaving land fallow, crop rotation, constructing check dams, reducing overgrazing, using scientific agriculture.

 

Water:

Q.7 What percentage of Earth's water is fresh water, and where is most of it stored?

Answer- Fresh water percentage: Only 2.7% of Earth's water is fresh, mostly stored in ice caps and glaciers.

 

Q.8 How do human activities pollute water resources?

Answer- Water pollution: Sewage, industrial waste discharge harms marine life.

 

Q.9 How does water scarcity affect different parts of the world?

Answer- Water scarcity: Deforestation and climate change affect rainfall patterns, leading to water shortage in some regions.

 

Q.10 Describe how the Indira Gandhi Canal project has changed the land-use pattern in Rajasthan.

Answer- Indira Gandhi Canal project: Diverts Beas river water to Sutlej river, providing water to western Rajasthan, making it a fertile agricultural area.

 

Q.11 Why is water availability a problem in some regions of India?

Answer- Uneven water distribution in India: Rainfall is limited to monsoon season, causing water scarcity in central, western, and southern regions.

 

Q.12 Explain different methods for water conservation.

Answer- Water conservation methods: Preventing pollution, rainwater harvesting, using drip irrigation, reducing water runoff, constructing dams for storage and hydropower generation.

 

Understanding Concepts:

Q.13 How are mountains helpful for agriculture and climate regulation?

Answer- Mountains and agriculture/climate: Glaciers provide water for rivers, nourishing plains for agriculture. Mountains also act as barriers, affecting wind patterns and rainfall.

 

Q.14 Why are plains suitable for high population density?

Answer- Plains and population density: Flat, fertile land allows for intensive agriculture, supporting larger populations.

 

Q.15 How does the process of leaching affect soil fertility?

Answer- Leaching and soil fertility: Rainwater dissolves and washes away minerals from the upper soil layer (A horizon) reducing fertility.

 

Q.16 Explain the connection between deforestation and water scarcity.

Answer- Deforestation and water scarcity: Trees play a crucial role in the water cycle. They attract clouds by making the climate cool through transpiration. Also they help in restoration of ground water. Deforestation disrupts this cycle, leading to less rainfall and increased water scarcity.

 

Q.17 How do terrace farming and contour farming help prevent soil erosion?

Answer- Terrace/contour farming and soil erosion: These techniques involve farming across slopes following the elevation, creating steps that slow down water flow and prevent soil erosion.

 

Values and Life Skills:

Q.18 Why is it important to conserve land, soil, and water resources?

Answer- Importance of conservation: Land, soil, and water are essential for life and a good quality of life. Conservation ensures their availability for future generations.

 

Q.19 How can agricultural practices affect soil quality?

Answer- Agriculture and soil quality: Intensive farming practices can deplete soil nutrients and organic matter, leading to reduced fertility.

 

Q.20 Suggest solutions to reduce soil erosion caused by agriculture.

Answer- Solutions for soil erosion: Sustainable agricultural practices like crop rotation, using natural fertilizers, and reducing tillage minimize soil erosion.