[4 Marks Each] QUE-ANS

Question 14 Marks

Explain the alluvial (river) land- forms.

Answer

Alluvial landform : When the running water of a river tumbles with great force Over the solid (hard) rocks in a steep sloped valley, or in a low-lying land, its flow is called a waterfall.
When a river enters a plain, it flows in a zigzag path.
The larger zigzag paths (or bends) of a river are known as 'meanders'. The river continuously carries erosion and deposition on the banks of the meanders.
In due course of time, when these meanders come closer, they form a shape which resembles a horse-shoe or a circle. At this stage of the river,
when the river is flooded, the land parts between the meanders are cut-off by the deposition of the river flow and the river takes to straight path abandoning the longer path.
The water remains in the abandoned cylindrical part of the river.
As a result, a lake is formed there which is known as Ox-bow lake.
When the large rivers are flooded during rainy season, it forms a fertile plain on either banks of the river by depositing alluvium and other material, which is called When a large amount of silt is deposited on both sides of the river, the raised banks are called 'Levees'.
The flow of the river becomes slow as it approaches a sea ocean. Due to its slow flow, it deposits the alluvium which it brings along with it in the form of sand, clay and other matter.
Due to this the flow of the river is divided into many streams and distributaries.
Each distributary forms its own river mouth. Due to the collection of all sediments of all river mouths, a very fertile Delta is formed.

Glacial landforms : High latitudes or high mountainous regions remain snow-clad throughout the year.

The snow accumulated on the high slopes of the mountains gradually starts moving towards lower slopes.
This gradual flow of moving snow is called 'Glacier'.
The glacier erodes by bulldozing, rocks, etc.
to expose the solid rock below, and forms a specific landscape. Besides, the glacier forms 'U' shaped valley. It also forms deep gorges. In the mountainous regions, the ice (snow) in these gorges melts and water is filled in these gorges. This results in the formation of beautiful lake called ‘Tarns'.
The glacier brings small and large rock particles, sand, pebbles, etc. along with it and deposits them. Due to such deposits, the glacier forms a hillock-like landform in the middle of its flow which is called 'Drumlin'.

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Question 24 Marks

Explain the types of rocks giving examples.

Answer

On the basis of formation process, the main types of rocks are as follows :$(i)$ Igneous rocks, $(ii)$ Sedimentary or Stratified rocks and $(iii)$ Metamorphic rocks.$(i)$ Igneous rocks : During a volcanic eruption the hot magma (lava) in the interior of the earth spreads on the crust or on the surface of the earth. The rocks which are formed when this lava is cooled down are called 'Igneous rocks'. Igneous rocks are of two types :$(1)$ Extrusive igneous rocks and $(2)$ Intrusive igneous rocks.At the time of volcanic eruption, the rocks which are formed due to rapidly cooling down of the lava thrown out towards the surface of the earth are called 'Extrusive igneous rocks'.

These rocks have finer granular structure.
Basalt is the best example of extrusive igneous rock. If the magma or lava in the interior of the earth cools down in the earth's crust $(SiAl)$ or deep inside, then the solid rocks formed at that place are called 'intrusive igneous rocks'. Due to slow cooling of the lava, it forms larger granules.
Granite is the best example of intrusive igneous rocks. It is used mainly to grind cereals, grains or condiments and spices.
$(ii)$ Sedimentary rocks : The process of erosion the surface of the earth is continuously carried out by factors like rain, river, glacier and wind. The rock material, clay, vegetation, residue of animals, etc.
separated due to erosional process are carricd away by running water and are collected at another place.
Thus, one layer is formed over another layer by the material deposited in the water.
These layers are suppresed bccause of the pressure of overlying rock layers. With the passing of time, stratified solid rocks are formed out of this. That is why these rocks are called 'Sedimentary' or 'Stratificd rocks'.
E.g., sandstone is formed from the sand granules.
Fossils are formed out of vegetation, animals and minute bacteria.

$(iii)$ Metamorphic rocks : When igneous rocks and sedimentary (stratified) rocks come under extremely high heat and intense pressure, their basic composition, structure and shape change totally, and the rocks thus formed are called 'Metamorphic rocks'. E.g., sticky clay turns into slate and limestone into marble.

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Question 34 Marks

Explain the landforms caused by Sea Waves.

Answer

The erosion and the deposition by sea waves give rise to different coastal landforms.

The sea waves continuously strike against the rocks, as a result, cracks develop in them.
Over the time, these cracks become larger and wider which are called 'Sea Caves'.
When these caves become larger, only their roofs remain which form sea arches. Due to the constant erosion by the sea waves, the roof of these caves is broken and only the walls remain.
This wall-like landform feature is called 'Stack'.
The rocky coast rising almost vertically above the sea water is called 'Sea Cliff. The sea waves deposit

sediments along the seashores and form the 'Sea Beaches.

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Question 44 Marks

What is meant by an earthquake ? Explain the process of an earthquake.

Answer

Due to the oving of the lithospheric tectonic plates, certain weak part of the earth suddenly vibrates.

The sudden vibration (tremor) on the surface of the earth is called an earthquake'.
The place or the centre within the crust of the earth, from where the seismic waves start, is called 'Focus' of an earthquake.
The seismic waves originated from the Focus travel through various parts of the earth in different directions with different velocity.
The nearest place from the focus on the surface of the earth is called 'Epicentre'.
Maximum effect of an earthquake is felt in surrounding areas of the epicentre.
The effect of the earthquake reduces while going away from the epicentre. The effect of an earthquake over any region depends on the intensity of the earthquake.

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Question 54 Marks

Explain the utility of the rocks.

Answer

The crust of the earth is made up of different rocks.

The solid rocks are used for making of roads, houses and buildings.
There are many minerals in the rocks. Minerals have been useful in the development of human civilization.
Today, most of the industries are run by machines.
The machines are manufactured from mineral like iron. Coal and mineral oil are mostly used as the energy resources of the machines. Minerals are necessary for medicinal uses also.
Petrochemical industries are dependent only on minerals and natural gas.
Thus, recent industrial development is almost dependent on minerals. So the rocks are useful as the storehouse of minerals.

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Question 64 Marks

Explain the Rock cycle.

Answer

When the hot and liquid magma cools down and becomes solid, it forms igncous Scanned wrocks.

The igneous rocks turn into smaller particles, are transported from one place to another and form sedimentary or stratified rocks.
Due to extreme high temperature and pressure, the igneous or sedimentary rocks are transformed into metamorphic rocks. Due to the high temperature and pressure, thesc rocks melt and again become hot liquid magma.
This hot magma again cools down and solidifies into igneous rock again. Thus, under certain conditions, one type of rock transforms into another type of rock in a cyclic manner. This process is known as 'Rock Cycle'.

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Social Science [4 Marks Each] QUE-ANS

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