UPSC NDA-2

Lithosphere consists of

[amp_mcq option1=”upper and lower mantle.” option2=”crust and core.” option3=”crust and uppermost solid mantle.” option4=”mantle and core.” correct=”option3″]

C

The Earth’s internal structure can be described in terms of both chemical composition and physical (rheological) properties. The lithosphere is defined by its physical properties; it is the rigid, outermost shell of the Earth. It consists of the crust (both continental and oceanic) and the uppermost, rigid part of the mantle (also known as the lithospheric mantle). It sits atop the asthenosphere, which is a more ductile layer of the upper mantle.

The lithosphere is typically about 100 km thick, though its thickness varies significantly, being thinner under oceanic crust (around 50-100 km) and thicker under continental crust (up to 200 km or more beneath old mountain ranges). The movement of the lithospheric plates over the asthenosphere is the basis of plate tectonics.

Which one of the following is a major plate ?

[amp_mcq option1=”Pacific Plate” option2=”Cocos Plate” option3=”Arabian Plate” option4=”Philippine Plate” correct=”option1″]

A

The Earth’s lithosphere is divided into several large tectonic plates. Major plates are the largest ones. The generally accepted list of major plates includes the Pacific Plate, North American Plate, Eurasian Plate, African Plate, Antarctic Plate, Indo-Australian Plate, and South American Plate. The other options listed – Cocos Plate, Arabian Plate, and Philippine Plate – are typically classified as minor or secondary plates due to their smaller size.

There are roughly seven to nine major tectonic plates and numerous minor plates. Major plates cover vast areas, often including both continental and oceanic crust. Minor plates are smaller fragments of the lithosphere. Plate tectonics is the theory describing the large-scale motion of these plates, which is responsible for earthquakes, volcanic activity, mountain building, and ocean basin formation.

Stalactite, stalagmite and pillars are the depositional landforms of

[amp_mcq option1=”running water.” option2=”wind.” option3=”glacier.” option4=”underground water.” correct=”option4″]

Stalactites, stalagmites, and pillars are depositional landforms typically found in karst topography, which is shaped by the action of underground water dissolving and redepositing soluble rock, primarily limestone.

Stalactites hang from the ceiling of caves, formed by calcium carbonate deposited from dripping water. Stalagmites rise from the cave floor as water drips from above. Pillars are formed when a stalactite and a stalagmite meet.

These features are formed through the process of precipitation of dissolved minerals (calcite) as the water, supersaturated with calcium bicarbonate, loses carbon dioxide upon exposure to the cave air. Underground water is the primary agent responsible for both the dissolution (creating caves) and deposition (forming these structures) in karst regions.