[Mission 2022] QUIZ – 2020: INSIGHTS STATIC QUIZ , 21 October 2021 – Geography

Solution: a)

Pole fleeing force is a geophysical concept invoked in 1915 by Alfred Wegener to explain his ideas of Continental drift.

He suggested that a differential gravitational force (horizontal component of centrifugal force) and the Earth’s flattening would cause continental masses to drift slowly towards the equator.

This force is caused due to the spinning of earth.

The hypothesis was expanded in 1920 but the force is now known to be far too weak to cause plate tectonics. The toughness of the sublayers of the Earth’s crust is much stronger than assumed by Wegener.

Solution: a)

• Oceanic crust is the result of erupted mantle material originating from below the plate, cooled and in most instances, modified chemically by seawater.
• Oceanic crust is about 6 km thick, Continental about 10 Km. It is composed of several layers, not including the overlying sediment.
• The topmost layer, about 500 metres (1,650 feet) thick, includes lavas made of basalt (that is, rock material consisting largely of plagioclase [feldspar] and pyroxene).
• Oceanic crust differs from continental crust in several ways: it is thinner, denser, younger, and of different chemical composition.

Solution: c)

• Plate tectonics is the modern version of continental drift, a theory first proposed by scientist Alfred Wegener in 1912.
• Wegener didn’t have an explanation for how continents could move around the planet, but researchers do now.
• Plate tectonics is thus said to be the unifying theory of geology.
• The driving force behind plate tectonics is convection in the mantle. Hot material near the Earth’s core rises, and colder mantle rock sinks.

Solution: b)

The mapping of the ocean floor and palaeomagnetic studies of rocks from oceanic regions revealed the following facts:

(i) It was realised that all along the midoceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area.

(ii) The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties. Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks increases as one moves away from the crest.

(iii) The ocean crust rocks are much younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million years old. Some of the continental rock formations are as old as 3,200 million old.

(iv) The sediments on the ocean floor are unexpectedly very thin.

(v) The deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow depths. It means lava is in close vicinity.

Solution: d)

The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth.