[Mission 2022] QUIZ – 2022: INSIGHTS STATIC QUIZ, 4 May 2022 – History – INSIGHTSIAS

Solution: b)

Some important minor plates are listed below:

(i) Cocos plate : Between Central America and Pacific plate

(ii) Nazca plate : Between South America and Pacific plate

(iii) Arabian plate : Mostly the Saudi Arabian landmass

(iv) Philippine plate : Between the Asiatic and Pacific plate

(v) Caroline plate : Between the Philippine and Indian plate (North of New Guinea)

(vi) Fuji plate : North-east of Australia.

Solution: c)

A shield volcano is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano’s distinctive form.

Solution: c)

The Archean system is the oldest rock system.

Dharwar System:

• Formation period ranges from 4 billion years ago to – 1 billion years ago.
• Highly metamorphosed sedimentary rock-system. [formed due to metamorphosis of sediments of Archaean gneisses and schists].
• They are the oldest metamorphosed rocks.
• Found in abundance in the Dharwar district of Karnataka.
• Economically the most important rocks because they possess valuable minerals like high grade iron-ore, manganese, copper, lead, gold, etc.

Solution: d)

Isohalines are lines (or contours) that join points of equal salinity in an aquatic system.

Solution: c)

Acidic Rocks

• Acidic rocks are characterised by high content of silica (quartz and feldspar) — up to 80 per cent.
• The rest is divided among aluminium, alkalis, magnesium, iron oxide, lime etc.
• These rocks have a lesser content of heavier minerals like iron and magnesium. Hence, they are less dense and are lighter in colour than basic rocks.
• These rocks constitute the sial portion of the crust.
• Due to the excess of silicon, acidic magma cools fast, and it does not flow and spread far away.
• High mountains are formed of this type of rock.
• Granite, quartz and feldspar are typical examples.