geomorphology & earth landforms section 9 MCQ Questions & Answers Detailed Explanation

Answer: (d)

The Core is made up of heavier rocks having a density of 3 g/cm³. This type of rock found in the oceanic crust is basalt.

The mean density of material in the oceanic crust is 2.7 g/cm³.

The Mantle has a density higher than the crust’s (3.4 g/cm³).

The crust and the uppermost part of the mantle are called the lithosphere. Its thickness ranges from 10-200 km. The lower mantle extends beyond the asthenosphere. It is in a solid state.

The density of material at the mantle core boundary is around 5 g/cm³ and at the centre of the earth at 6,300 km, the density value is around 13g/cm³.

The core is made up of very heavy material mostly constituted by nickel and iron. It is sometimes referred to as the nife layer.

Answer: (b)

Alluvial fans are fan-shaped deposits of water transported material (alluvium). They typically form at the base of topographic features where there is a marked break in slope.

Consequently, alluvial fans tend to be coarse-grained, especially in their mouths. At their edges, however, they can be relatively fine-grained.

Answer: (b)

The Great Barrier Reef is in the Coral Sea, on Australia’s north-eastern coast. It stretches more than 2,300km along the state of Queensland’s coastline, beginning at the tip of Cape York Peninsula in the north and extending down to Bundaberg in the south. The Great Barrier Reef is ideal for Cairns Scuba Diving.

Answer: (c)

Marble is a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the term “marble” to refer to metamorphosed limestone. Marble is a rock resulting from the metamorphism of sedimentary carbonate rocks, most commonly limestone or dolomite rock.

Metamorphism causes variable recrystallization of the original carbonate mineral grains. The resulting marble rock is typically composed of an interlocking mosaic of carbonate crystals. Primary sedimentary textures and structures of the original carbonate rock (protolith) have typically been modified or destroyed.

Answer: (b)

The International Date Line (IDL) is an imaginary line on the surface of the Earth, that runs from the north to the South Pole and demarcates one calendar day from the next.

It passes through the middle of the Pacific Ocean, roughly following the 180° longitude but it deviates to pass around some territories and island groups. From the north, the dateline first deviates to the east of 180° to pass to the east of Russia’s Wrangel Island and the Chukchi Peninsula which is the easternmost part of Russian Siberia.

The dateline then passes through the Bering Strait between the Diomede Islands at a distance of 1.5 km from each island. The line then bends considerably southwest, passing west of St. Lawrence Island and St. Matthew Island.

It then passes midway between Alaska’s Aleutian Islands and Russia’s Commander Islands before returning southeast to 180°. Thus all of Siberia is to the west of the International Date Line, and all of Alaska is to the east of that line.

Answer: (b)

Loess is Aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20– 50 micrometre size range, twenty per cent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate.

It is usually homogeneous and highly porous and is traversed by vertical capillaries that permit the sediment to fracture and form vertical bluffs. The word loess, with connotations of origin by wind deposited accumulation, is of German origin and means “loose.” It was first applied to the Rhine River valley loess about 1821.