[Mission 2023] STATIC QUIZ, 20 May 2023 – Geography

Solution: d)

A palaeochannel is a remnant of an inactive river or stream channel that has been filled or buried by younger sediment.

These paleochannels reveal the course of rivers that have ceased to exist.

A palaeochannel is distinct from the overbank deposits of currently-active river channels, including ephemeral water courses that do not regularly flow because the river bed is filled with sedimentary deposits unrelated to the normal bed load of the current drainage pattern.

Palaeochannels are important to geology for a number of reasons:

• Understanding movements of faults, which may redirect river systems and so form stranded channels that are, in essence, palaeochannels.
• Preserving Tertiary, Eocene and Holocene sediments and fossils within them.
• Preserving sedimentary records, which is useful for understanding climatic conditions

Palaeochannels can host economic ore deposits of uranium, lignite, precious metals such as gold and platinum, heavy minerals such as tin, tungsten, and iron ore preserved as paleo-placer deposits.

Solution: b)

Submergent Coasts are those that have been flooded by ocean waters because of a relative rise in the elevation of sea level at that location. The rise in sea level can be either the result of an increase in the volume of water in the ocean basins or the result of the land surface sinking, both of which create an apparent rise in the elevation of sea level. Features of a submergent coastline are drowned river valleys or rias and drowned glaciated valleys or fjords.

Estuaries are often the drowned mouths of rivers.

The Western Coastal Plains of the Indian subcontinent are examples of submergent coastline.

Emergent coasts are a result of local tectonic uplift of the land surface or a fall in the elevation of sea level because of a reduction in the water volume of ocean basins. Quite often, emergent coasts have rocky coastlines with cliffs and nearly flat platforms that extend inland where older coastal plains have been tectonically raised and are now elevated above the modern land and water interface.

The emergent coastline may have several specific landforms:

• Raised beach
• Wave cut platform
• Sea cave

Solution: c)

Most of the metallic minerals in India occur in the peninsular plateau region.

The North-Eastern Plateau Region: This belt covers Chhotanagpur (Jharkhand), Odisha Plateau, West Bengal and parts of Chhattisgarh. It has variety of minerals viz. iron ore, coal, manganese, bauxite, mica.

The South-Western Plateau Region: This belt extends over Karnataka, Goa and contiguous Tamil Nadu uplands and Kerala. This belt is rich in ferrous metals and bauxite. It also contains high grade iron ore, manganese and limestone. This belt packs in coal deposits except Neyveli lignite. This belt does not have as diversified mineral deposits as the north-eastern belt. Kerala has deposits of monazite and thorium.

The North-Western Region: This belt extends along Aravali in Rajasthan and part of Gujarat and minerals are associated with Dharwar system of rocks. Copper, zinc have been major minerals. Rajasthan is rich in building stones i.e. sandstone, granite, marble. Gypsum and Fuller’s earth deposits are also extensive. Dolomite and limestone provide raw materials for cement industry.

The Himalayan belt is another mineral belt where copper, lead, zinc, cobalt and tungsten are known to occur.

Solution: d)

Continental Shelf is the submerged edge of a continent which is a gently sloping plain that extends into the Ocean. The typical gradient is less than 1°. The average width of continental shelves is about 80 km. The largest continental shelf is the Siberian Shelf in the Arctic Ocean, which stretches to 1,500 kilometres in width. Because of the gentle slope, the continental shelf is influenced by the changes in the sea level.

The shelf is formed mainly due to

• Rise in sea level
• Submergence of a part of a continent
• Sedimentary deposits brought down by rivers

Solution: c)

Winds blowing across the ocean surface push water away. Water then rises up from beneath the surface to replace the water that was pushed away. This process is known as “upwelling.”

Upwelling occurs in the open ocean and along coastlines. The reverse process, called “downwelling,” also occurs when wind causes surface water to build up along a coastline and the surface water eventually sinks toward the bottom.

Water that rises to the surface as a result of upwelling is typically colder and is rich in nutrients. These nutrients “fertilize” surface waters, meaning that these surface waters often have high biological productivity.  Therefore, good fishing grounds typically are found where upwelling is common.