Question Discussion & Solution

• A rock is any naturally occurring solid mass or aggregate of one or more minerals or mineraloid matter.
• The earth's crust is composed of rocks.
• It is categorized by the minerals included its chemical composition and the way in which it is formed.
• The rock cycle is a basic concept of transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous.
• Each rock type is altered when it is forced out of its equilibrium conditions.

​Metamorphic Rocks

• ​The word metamorphic means ‘change of form’.
• These rocks form under the action of pressure, volume and temperature (PVT) change.
• Metamorphism occurs when rocks are forced down to lower levels by tectonic processes.
• Or when molten magma rising through the crust comes in contact with the crustal rocks.
• Or the underlying rocks are subjected to great amounts of pressure by overlying rocks.
• Metamorphism is a process by which already consolidated rocks undergo recrystallisation and reorganisation of materials within original rocks.
• Common metamorphic rocks include slate, schist, gneiss, and marble.

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Thus, marble is an example of metamorphic rock.

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Igneous Rocks:

• Igneous Rocks are formed by crystallization from a liquid or magma.
• They are also known as primary rocks.
• There are two types of Igneous rocks based on their mode of occurrence: 

1. Volcanic or extrusive igneous rocks that form when the magma cools and crystallizes on the surface of the Earth
2. Intrusive or plutonic igneous rocks wherein the magma crystallizes at depth in the Earth.

• Magma is a mixture of liquid rock, crystals, and gas with a wide range of chemical compositions, temperature, and properties of a liquid.​

Sedimentary Rocks:

• ​The word ‘sedimentary’ is derived from the Latin word sedimentum, which means settling.
• Sedimentary rocks are called secondary rocks.
• They are often the result of the accumulation of small pieces broken off of pre-existing rocks.
• In many sedimentary rocks, the layers of deposits retain their characteristics even after deposition.
• Hence, we see a number of layers of varying thickness in sedimentary rocks like sandstone, shale etc.

The correct answer is Tendu.

Key Points
Tendu:

• Tendu is popularly known as ‘Vagad ka Chiku’ in Rajasthan.
• These are prominent in southeastern Rajasthan.
• It occurs in patches in most of the forest of Rajasthan.
• Its scientific name is Diospyros melanoxylon.
• It is used in the manufacturing of Bidis.
• Madhya Pradesh has the highest number of trees.

Additional Information

• In Rajasthan, the concentration of Tendu trees is in subtropical forests. The major regions in which tendu are found are Jhalawar, Bara, Kota, Chittorgarh, Banswara, Udaipur and Dungarpur. 

The correct answer is Dausa.

• As per the 2011 census, the Dausa district has the lowest percentage of the urban population.
• Of the total population of Rajasthan state, around 75.13 per cent live in the villages of rural areas.
  • In actual numbers, males and females were 26,641,747 and 24,858,605 respectively.
  • The total population of rural areas of Rajasthan state was 51,500,352.

Key Points

Top 5 Districts of Rajasthan having highest Rural population

Bottom 5 Districts of Rajasthan having the lowest Rural population

The correct answer is Dungarpur - Banswara.

Key Points

• In Rajasthan, the Mahi river forms the boundary with Dungarpur and Banswara districts.

Additional Information 

• Mahi is one of the major interstate west-flowing rivers.
  • The total length of Mahi is 583 km.
  • It originates in the Mahi Kanta hills, from the northern slopes of Vindhyas at an altitude of 500 m near village Bhopawar, Sardarpur Tehsil in Dhar district of Madhya Pradesh. 
  • It enters the Banswara district of Rajasthan and makes the border between Banswara and Dungarpur. 
  • Mahi river tributaries- Som, Anans, and Panam.
  • Mahi is the only river that crosses the tropic of cancer twice.

The correct answer is option 3 i.e Pali.

• Pali district is located between 24°45′ to 26°29′ North Latitudes and 72° 47′ to 74° 18′ East Longitudes 
• It shares its boundaries with 8 districts of the state namely, Ajmer, Barmer, Jalore, Jodhpur, Nagaur, Rajsamand, Sirohi and Udaipur.

Important Points

• Jawai Dam is one of the biggest dams of western Rajasthan and situated in Sumerpur tehsil of Pali district.
• Todgarh Raoli Wildlife Sanctuary is spread over Ajmer, Pali and Rajsamand districts of Rajasthan.

Additional Information

• Nagaur touches 7 districts namely, Jodhpur, Bikaner, Churu, Sikar, Jaipur, Ajmer, Pali.
• Jodhpur touches 5 districts namely, Jaisalmer, Bikaner, Nagaur, Pali, Barmer.
• Rajsamand touches 5 districts namely, Ajmer, Bhilwara, Chittorgarh, Udaipur, Pali.