Daily Static Quiz -26th November 2022

Ans C
Justification : Magma cools slowly as it rises towards Earth’s surface . It can take thousands to millions of years to become solid when it is trapped inside Earth .
As the magma cools , solid rocks form ( igneous ) .
These rocks are mixtures of minerals . Granite is a common rock that forms when magma cools . Granite contains the minerals quartz , plagioclase feldspar and potassium feldspar .
The same igneous rock can be eroded , weathered , transported , deposited and consolidated as sedimentary rocks which are the source of non – metallic minerals .

Ans( a )
Justification : Azoic Age was used to describe the age of rocks formed before the appearance of life in the geologic sequence .
Also known as Pre – Cambrian rocks , these are the oldest rocks of the Earth’s crust .
The Archaean period covers over 85 % of the total geological history time of Earth and therefore is very significant . This period marks the development of first photosynthesis , the life support atmosphere .
The Archaean or Purana rock system in India is found in Aravallis mountains , two thirds of the Deccan peninsula and some parts of the North – east . These rocks have abundant metallic and non – metallic minerals such as iron , copper , manganese , bauxite , lead , zinc , gold , silver , tin , tungsten , mica , asbestos , graphite , etc.
They serve as the basement complex or fundamental gneisses .

Ans ( a )
Two types of Precambrian rocks of India are Dharwar system and Archaean system . In Dharwar system , rocks originate mainly from sediments . And they occur in a narrow elongated synclines that are resting on the gneisses found in Bellary district , Mysore , and the Aravallis of Rajputana . Manganese and iron ore , which represent a significant resource of these metals , are the major constituents of these rocks .
Dharwar system is later than the Archaean system but older than the other systems . The Dharwar period of rock formation has been largely fixed from 2500 million years ago to 1800 million years ago .

Ans( b )
The rugged terrain and adverse climatic conditions make exploration of minerals difficult and costly , but it can’t be a reason for lack of mineral resources . So , ( a ) and ( b ) are wrong .
Our rich mineralised zone is largely confined to the old , crystalline rock structures of plateaus and low hills of peninsular India . So , option ( d ) is clearly wrong .
In Himalayas , geological processes have led to major displacement of rock strata . This has disturbed the arrangement of rocks and made it complex , making Himalayas poor in mineral resources .

Ans A
Justification:
Statement 1 The Siwalik series comprehends the two zones of strata forming the outermost ranges of the Sub Himalayas . The series of rocks can be found near valleys of Ravi , Chenab and Jhelum . Petrologically , this group consists either of coarse conglomerates or of fine , brown clays , the latter being indistinguishable , in hand specimens , from the modern alluvium of the Punjab . The conglomerates occur mainly on the lines of the larger rivers , being replaced in the intervals by the clays .
Statement 2 : A Siwalik system of rocks falls under Cenozoic Era and belongs to Middle – Miocene , Pliocene and Lower Pleistocene period or Epoch .
This system of rocks is considered to be one of the largest storchouse of mammalian remains and other vertebrate fossils . So , 2 is wrong.
The study of these rocks has made it possible for geoscientists to probe into the mysteries of evolution of life , climate and physiography of these periods .
The era of Siwalik system of rocks is also called the ‘ Age of Mammals ‘ .
As the system contains considerable mammalian fossils , the geologists have divided it into three series viz . Upper Siwalik , Middle Siwalik and Lower Siwalik .

Ans( d )
Justification : Khasi hills , one of the youngest , belong to Tertiary period ( to which a large area in North – east also belongs ) .
Shiwaliks are part of Himalayas , so given the reasoning below , ( b ) will also be incorrect .
The alluvium which is found in the Indo Gangetic plain belongs to the Quaternary period . It was eroded from the Himalayas by the rivers and the monsoons since Himalayas were formed after Deccan traps , and are very young .
The Deccan Plateau in India is one of the oldest plateaus in India made mainly from igneous rocks .

Ans( d )
Justification :
Seasonal variation in discharge defines river regime . Three broad classes of regime can be distinguished for perennial streams . In the megathermal class , related to hot equatorial and tropical climates , two main variants occur ; discharge is powerfully sustained throughout the year , usually with a double maximum ( two peak values ) , but in some areas with a strong single maximum . In the mesothermal class some regimes resemble those of tropical and equatorial areas , with single or double summer maxima corresponding to heavy seasonal rainfall , while others include sustained flow with slight warm – season minima . Where midlatitude climates include dry summers, streamflow decreases markedly and may cease altogether in the warm half of the year .
Peninsular rivers entirely depend on monsoons and have no glaciers .

Ans ( d )
In the Himalayan reaches , the course of the Himalayan rivers is highly tortuous , but over the plains they display a strong meandering tendency and shift their courses frequently .
River Kosi , also known as the sorrow of Bihar , has been notorious for frequently changing its course . The Kosi brings huge quantity of sediments from its upper reaches and deposits it in the plains . The course gets blocked , and consequently , the river changes its course . Same is the case with Brahmaputra.
Justification : Basic facts .

Ans( d )
Justification :
Option ( a ) : There are no such anti – cyclones that blow around Indus delta throughout the year .
Option ( b ) : While the climate is arid , the region receives paltry 25 to 50 cm of rainfall in a normal year . So , B is incorrect . However , this is a factor adding to the wasteland problem .
Option ( c ) : Since the 1940s , the delta has received less water as a result of large – scale irrigation works capturing large amounts of the Indus water before it reaches the delta . So , ( c ) is incorrect .
The result has been catastrophic for both the environment and the local population .
Option ( d ) : The lack of freshwater ( from both rainfall and rivers ) and high amount of brackish water in the Indus region have led to the region turning into a wasteland .
However , the delta is still home to the largest arid mangrove forests in the world , as well as many birds , fish and the Indus Dolphin .

Ans( c )
Justification :
A proliferation of large dams that starve deltas of sediment , groundwater mining that causes land compaction , and artificial levees that affect river courses , have been responsible for the subsiding of major Indian deltas including Ganga – Brahmaputra , Krishna – Godavari , Brahmani and Mahanadi .