5. Lithosphere
Geography · Maharashtra State Board · Question & Answer Notes
Questions Asked Inside the Chapter
Thought-provoking (p. 37): Let it be naturally built mountains or an anthill, both are forms found in the Lithosphere. Find other such forms of Lithosphere.
Ans: Other forms of the lithosphere are hills, hillocks, plateaus, plains, valleys, gorges, deserts, sand dunes, islands, volcanoes, caves, riverbanks, cliffs and the ocean floor.
Enlist the landforms around you.
Ans: Landforms around us (examples for a Maharashtra student): hills and hillocks of the Sahyadri, a plateau such as the Deccan, the Konkan coastal plain, river valleys, beaches, creeks and islands. Students should write the ones seen in their own area.
Table no. 5.1 Types of spheres (Figure 5.1)
| Nature of the sphere | Name of the sphere |
|---|---|
| Solid | Lithosphere |
| Liquid | Hydrosphere |
| Gaseous | Atmosphere |
| Habitat of living organisms | Biosphere |
Classify the components shown in the figure into ‘natural components’ and ‘man-made components’.
Ans: Natural components: trees, birds, fish, humans, clouds, sky, water, land. Man-made components: aeroplane, ship, road, railway track.
Which means of transport are shown in the figure?
Ans: The figure shows an aeroplane (air transport), a ship (water transport) and a road and railway track (land transport).
In which sphere do birds and aeroplanes fly?
Ans: Birds and aeroplanes fly in the atmosphere.
In which of the Earth’s spheres do ships travel?
Ans: Ships travel in the hydrosphere.
Which of the Earth’s spheres is used for constructing roads and railways?
Ans: The lithosphere is used for constructing roads and railways.
Which of the spheres of the Earth in the figure are the trees, birds, humans and fish?
Ans: Trees, birds, humans and fish belong to the biosphere.
Try to find: Conduct a comparative study of the environment of your region and other regions. On the basis of this, understand the effect of various spheres on the environment.
Ans: Sample answer: Our region (coastal Maharashtra) has a hot, humid climate, heavy rain, plains and sea. The Sahyadri hills and the Deccan Plateau have cooler weather and less rain, and a desert region like Rajasthan is dry and hot. This shows that the lithosphere (relief) decides land use, the hydrosphere (sea, rivers) affects rainfall and water supply, the atmosphere decides climate, and the biosphere (plants, animals, people) depends on all three.
Try to understand me (Fig. 5.4): Which questions regarding the interior of the Earth come to your mind when you look at the figure given above? Enlist those questions.
Ans:
- What is the inside of the Earth made of?
- How deep is the Earth and can we reach its centre?
- How hot is it inside the Earth?
- How do scientists know about the interior?
Find me: The names of the scientists who discovered that there are discontinuities between the layers due to layer-wise changes in densities are given to the respective discontinuities. Find out information about these discontinuities.
Ans:
- Mohorovičić discontinuity (Moho): between the crust and the mantle.
- Gutenberg discontinuity: between the mantle and the outer core.
- Lehmann discontinuity: between the outer core and the inner core.
Just do it: Prepare a model/diagram of the interior of the Earth by referring to Figure no. 5.5 and Table No. 5.2. Present it in the class.
Ans: Make a round model in layers, using clay or coloured paper: a thin outer ring (crust, brown), a thick ring (mantle, orange), a liquid outer core (red) and a solid inner core (yellow). Label each layer with its thickness, state and temperature from Table 5.2, then present it in class.
Find me around: Enlist the landforms found in your area, write and discuss their characteristics with your classmates.
Ans: Sample: Hill – higher than 600 m with gentle slope; Plain – flat, low-lying, below 300 m; Valley – low land between hills where a stream flows; Plateau – raised flat land with steep edges. Students should add the landforms of their own area.
Try if you can (Fig. 5.6): Identify the landforms in the figure given below and write the names at the correct places.
Ans: Tallest pointed peak: Mountain; lower, rounded high land: Hill; small dome-shaped rise: Hillock; raised land with a flat top: Plateau; low land between the heights: Valley; flat low land at the right: Plain. (Match each name to the arrow in your book by shape and height.)
Let’s identify.
- I am created through fissure eruption. I am like a block though I have slopes. Though I am tall, flat is my top. → Plateau
- I am at a low level from the sea level. Have not become plain by rubbing. Low-lying, extensive is my identity. → Plain
- I don’t have a sharp peak, nor do I have a plain top. However, I look tall and straight on the ground. Circular and dome-shaped is my identity. → Hillock
- Where the slopes of two mountains meet, there are the imprints of my existence. ‘A river flows through me’ is my identity. → Valley
Friendship with Map (Fig. 5.8): Colour the continents in the given map and write their names.
Ans: Colour and name the seven continents: Asia, Africa, North America, South America, Antarctica, Europe, Australia. Write the names of the oceans too: Pacific, Atlantic, Indian, Arctic and Southern.
Find out (Fig. 5.9 World Physiography): Identify the landforms found all over the world in the physical map of the world given. Find out the names of the landforms with the help of the internet and teachers.
| Mountains | Plateaus | Plains |
|---|---|---|
| Himalaya, Rockies, Andes, Alps, Urals, Altai, Sahyadri, Atlas | Deccan, Tibetan, Siberian, Brazilian, Arabian, Ethiopian, Australian | Indo-Gangetic, Great Plains of North America, Amazon basin, Siberian plains, North European plain |
Exercise (pages 47 and 48)
A) Do as directed.
1) Complete the sentences by choosing the correct option.
(i) The height of the landforms on the Earth’s surface and the depth of the ocean floor start from ——- . (1000, 100, 10, 0)
Ans: The height of the landforms on the Earth’s surface and the depth of the ocean floor start from 0 (sea level).
(ii) The diameter of the Earth is approximately —— km. (6400, 12800, 3200, 9600)
Ans: The diameter of the Earth is approximately 12800 km. (The radius is 6400 km.)
2) Choose the incorrect statement.
Ans: Option c) A wide and shallow valley is called gorge is incorrect. A narrow and deep valley is called a gorge.
3) Choose the correct option of the pair. ‘Mountain’ – ‘Continent’
Ans: 1. The Rockies – d) North America; 2. The Ethiopian – f) Africa; 3. The Alps – e) Europe; 4. The Andes – a) South America; 5. The Altai – c) Asia. Correct option: B) 1-d, 2-f, 3-e, 4-a, 5-c.
B) Write the result.
1) Movement of liquid metals in the outer mantle.
Ans: The movement of liquid metals creates the Earth’s magnetic field, which protects the biosphere from harmful solar winds.
2) Tremendous pressure on the Earth’s centre.
Ans: Because of the tremendous pressure, the inner core remains in a solid state in spite of extremely high temperature.
3) Friction between plates.
Ans: Friction between the lithospheric plates causes earthquakes.
C) Explain the differences with the help of diagrams.
1) Mountain range and mountain chain
| Mountain range | Mountain chain |
|---|---|
| A continuous, high and steeply sloping series of mountains in one line. | A series of mountains spread in different directions. |
| Example: Sahyadri. | Example: a group of several ranges, such as the Himalayan system. |
Mountain range (one line)
Mountain chain (spread out)
2) George and Valley (Gorge and Valley)
| Gorge | Valley |
|---|---|
| Narrow and deep. | Broad and shallow, V or U shaped. |
| Steep sides; a river flows at the bottom. | Gentle sides; a stream flows through it. |
Gorge
Valley (U shape)
3) Upper and lower parts of the Crust (Continental crust and oceanic crust)
| Continental crust | Oceanic crust |
|---|---|
| Upper part, forms the landmass. | Lower part, lies below the oceans. |
| Thicker: 30 to 70 km. | Thinner: 3 to 5 km. |
| Silica + Aluminium (SiAl). | Silica + Magnesium (SiMa). |
| Density about 2.7; main rock granite. | Density about 3.0; main rocks basalt and gabbro. |
Crust: upper (land) and lower (ocean floor)
D) Give reasons.
1) Continental crust is called SiAl.
Ans: Continental crust is mainly made of the lighter elements Silica (Si) and Aluminium (Al). Hence it is called SiAl.
2) The Core is called ‘NiFe’.
Ans: The Core is mainly made of the heavy elements Nickel (Ni) and Ferrous (Fe, iron). Hence it is called NiFe.
E) Think and write an answer.
1) Why are the maximum quantities of Ferrous and Nickel found in the Core?
Ans: When the Earth was in a hot, liquid form, the heavy elements Nickel and Ferrous sank towards the deep middle part because of their weight, while lighter elements like Silica and Aluminium rose to the upper parts. So the Core has the maximum quantity of Ferrous and Nickel.
2) What are the reasons for the movements of plates other than the semi-fluid state of the outer mantle?
Ans: Other reasons are the intense heat from the Earth’s interior, which creates slow convection currents in the mantle, the stress and strain caused by energy waves inside the Earth, and the differences in density of the rocks that make hot rock rise and cooler, heavier rock sink.
F) Answer in brief.
1) Write a note about the temperature in the Earth’s interior.
Ans: The temperature increases with depth, by about 1 °C for every 32 metres. The average surface temperature is 15 °C. The outer mantle is about 1400 °C to 3000 °C, the outer core about 3000 °C and the inner core about 6000 °C.
2) Explain the difference between the inner core and the outer core.
| Outer core | Inner core |
|---|---|
| Liquid state. | Solid state, due to extreme pressure. |
| Between the mantle and inner core; about 3000 °C. | Innermost layer; about 6000 °C. |
| Mainly Nickel; creates the magnetic field. | Mainly Ferrous; density about 13 gm/cm³. |
3) Answer why the outer mantle is semi-fluid.
Ans: The temperature of the outer mantle is similar to the melting point of its rocks. So the rocks are in a semi-molten condition and the layer is in a semi-fluid state.
4) How could the Earth’s interior have been studied?
Ans: The Earth’s centre cannot be reached, so geologists study the interior indirectly through earthquake waves, materials thrown out in volcanic eruptions, the Earth’s magnetism and gravity, and the rise in temperature with depth.
5) Explain the impact of landforms on human life.
Ans:
- Plains: fertile soil, agriculture, big cities, roads and railways.
- Mountains and hills: forests, rivers, minerals, tourism; but they make transport and settlement difficult and affect rainfall and climate.
- Plateaus: rich in minerals and used for mining; good for cotton and pulses.
- Valleys: rivers give water for irrigation and electricity (dams).
G) Perform group discussion.
1) Have you ever been on a trip? Discuss in a group the differences between the landforms found in your area and the area you visited.
Ans: Sample points: Our area has plains and a coast, but the hill station visited had mountains, valleys, waterfalls and cooler weather. People there do tourism and grow tea or fruit, while our area depends on fishing, trade and industry. Each group should speak about its own trip.
Activity
Create a model of the structure of the Earth’s interior.
Ans: Prepare a layered model of the crust, mantle, outer core and inner core, as described in ‘Just do it’.
Enlist the landforms found in your area and write their characteristics.
Ans: Hill, plain, valley, plateau, etc., as listed in ‘Find me around’.
Enlist the landforms that are not found in your area, but are found in other parts of the world, with the help of your parents and present in class.
Ans: Examples: high snow-capped mountains (Himalaya), large plateaus (Tibetan Plateau), deserts (Thar, Sahara), Great Rift Valley (Africa), the Andes mountains (South America).
Observe the above picture and identify landforms.
Ans: The picture shows snow-capped mountains and hills, a valley with a winding river, waterfalls, a dam and lake, a plateau with steep edges (cliff), a plain with farms and villages, a bridge over the river and an island in the sea.