[Mission 2023] INSIGHTS STATIC QUIZ, 01 August 2022 – Geography

Solution: c)

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: b)

Mariana Trench is at east of Philippine coast.

Along a convergent boundary two lithospheric plates collide against each other. When one of the plates is an oceanic plate, it gets embedded in the softer asthenosphere of the continental plate, and as a result, trenches are formed at the zone of subduction.

Solution: c)

Jet streams are the product of two factors: the atmospheric heating by solar radiation that produces the large-scale Polar, Ferrel, and Hadley circulation cells, and the action of the Coriolis force acting on those moving masses.

Solution: c)

All the above factors influence insolation.

Rotation of earth: The rotation of the earth on the inclined axis has a greater influence on the amount of insolation received at different latitudes.

Length of the day: The length of the day determines the duration of sunlight which affects the amount of solar radiation received by the earth’s surface.

Transparency of the atmosphere: Atmosphere is not transparent for all the radiation coming from the sun because of different composition and layers. It is also one of the controlling factors of insolation to reach earth surface.

Angle of inclination of sun rays: Since the earth is a geoid resembling a sphere, the sun’s rays strike the surface at different angles at different places. This depends on the latitude of the place. The higher the latitude, the less is the angle they make with the surface of the earth. The area covered by the vertical rays is always less than the slant rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases. Moreover, the sun’s rays with small angle traverse more of the atmosphere than rays striking at a large angle.

Earth’s Distance from Sun: The earth is revolving around the sun in an elliptical orbit, resulting continuous change in the distance between sun and the earth on annual basis. It leads to seasonal variation in solar energy received by the earth.  During aphelion the northern hemisphere is facing the sun and therefore receives energy about 7 percent less than the perihelion (southern hemisphere).

Solution: c)

The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics. Generally, at the same latitude the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.