Answer: (B)

Explanation:

• Along much of the Ring of Fire, tectonic plates move towards each other creating subduction zones. One plate gets pushed down or is subducted by the other plate. This is a very slow process – a movement of just one or two inches per year. As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity. Subduction zones are also where most of the violent earthquakes on the planet occur. Hence, statement 1 and 2 are correct.
• The December 26, 2004 earthquake occurred along the subduction zone where the Indian Plate was subducted beneath the Burma plate. Hence, statement 3 is incorrect.

Answer: (D)

Explanation: The term karst describes a distinctive topography that indicates dissolution (also called chemical solution) of underlying soluble rocks by surface water or ground water. Although commonly associated with carbonate rocks (limestone and dolomite) other highly soluble rocks such as evaporates (gypsum and rock salt) can be sculpted into karst terrain. Understanding caves and karst is important because ten percent of the Earth’s surface is occupied by karst landscape and as much as a quarter of the world’s population depends upon water supplied from karst areas. Though most abundant in humid regions where carbonate rock is present, karst terrain occurs in temperate, tropical, alpine and polar environments. Hence, both statements are incorrect.

Answer: (A)

Explanation:

• Salinity changes with depth, but the way it changes depends upon the location of the sea. Salinity at the surface increases by the loss of water to ice or evaporation, or decreased by the input of fresh waters, such as from the rivers. Hence, statement 1 is incorrect.
• Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’ There is a marked difference in the salinity between the surface zones and the deep zones of the oceans. Hence, statement 2 is correct.
• The lower salinity water rests above the higher salinity dense water. Salinity, generally, increases with depth and there is a distinct zone called the halocline, where salinity increases sharply. Hence, statement 3 is incorrect.

Answer: (A)

Explanation: Dew point is the temperature at which the atmosphere is saturated with water vapour, when it is cooled without changing its pressure or vapour content. A given volume of air containing much water vapour has a higher dew point than the same volume of drier air; thus the dew point gives an indication of the humidity. In meteorology the dew point is applied, for example, in predicting the height of the base of certain types of clouds. A higher dew point means there will be more moisture in the air. Hence, statement 3 is incorrect.

Answer: (B)

Explanation: Divergent Boundaries: Where new crust is generated as the plates pull away from each other. The sites where the plates move away from each other are called spreading sites. The best-known example of divergent boundaries is the Mid-Atlantic Ridge. At this, the American Plate(s) is/are separated from the Eurasian and African Plates. Hence, option (b) is correct.