CSIR NET Earth Science Mock Test - 1 - CSIR NET Earth Science MCQ

In the Northern Hemisphere, the December Solstice (December 22nd) is the winter solstice and the shortest day of the year. In the Southern Hemisphere, the December Solstice is the summer solstice and the longest day of the year. The Sun is directly overhead of the Tropic of Capricorn in the Southern Hemisphere 23 ¹/2^o S during the December Solstice.

The rubidium-strontium dating method is a radiometric dating technique. It is used by scientists to determine the age of rocks and minerals from the quantities they contain of specific isotopes of rubidium (87Rb) and strontium (87Sr, 86Sr).

The utility of the rubidium–strontium isotope system results from the fact that 87Rb decays to 87Sr with a half-life of 49.23 billion years. Rb is a highly incompatible element. During partial melting of the mantle, Rb prefers to join the magmatic melt rather than remain in mantle minerals.

As a result, it is enriched in crustal rocks. The radiogenic daughter, 87Sr, is produced in this decay process. It was produced in rounds of stellar nucleosynthesis predating the creation of the Solar System. This method is not used for dating ice cores.

Some common materials have been assigned hardness values according to Mohs scale and may prove useful in determination of hardness of an unknown mineral quickly. Hardness of human finger nail varies between 1.5 and 2.5.

Mineralogy is the branch of geology dealing the wide range of aspects related to minerals like, their individual properties, mode of occurrence and mode of formation

Hardness is an anisotropic property; a mineral may show different values in different directions.

The pelagic deposits consist of two major types of ooze and red clays.

Siliceous Ooze: In regions of relatively high productivity where siliceous tests accumulates faster than they dissolve, siliceous ooze are found.

They are dominated 14% of the deep oceanic areas. For example, diatomaceous ooze and radiolarian ooze.

Calcareous Ooze: They are the most widespread ooze. They are formed at the shallower oceanic depths from the remnants of small animals and plants.

They are found throughout the ocean floor. For example, globigerina ooze, Pteropod ooze and coccolithophores ooze.

Red Clay: They are the most widespread pelagic deposits. It is also known as brown clay or pelagic clay.

It mainly consists of hydrated silicates of aluminium and iron oxides. it covers 38% of the ocean floor and accumulate in slower speed than the other sediment types.

First appearance of fishes is in the Paleozoic era.

First appearance of Dinosaurs is in the Mesozoic era.

First appearance of flowering plants is in the Mesozoic era.

First appearance of Whales is in the Cenozoic era.

The condensation trails that are produced by jet aircrafts which often spread out to form broad bands of cirrus clouds are known as traces of precipitation. The name is given to rainfall of less than hundredths (0.01) of an inch.

• Development of karst landscape is karstification and it is favoured by the presence of thick, mechanically strong, jointed limestones in the sub-surface, a humid climate and sufficient relief for rainwater to travel through to a deep water table.
• High amounts of leaching in soils in hot and humid tropical regions leads to laterization.
• Where evaporation exceeds precipitation, calcification occurs in soils and Pedzolization takes place in cool and moist climates.

Although tropical regions receive adequate sunlight year round, a permanent thermocline prevents the mixing of surface and deep water.

As phytoplankton consume nutrients in the surface layer, productivity is limited because the thermocline prevents replenishment of nutrients from deeper water.

Thus, productivity remains at a steady, low level. Red curve indicates temperature of the water column, with high temperature toward the right.

The Global annual mean temperature in the Cretaceous was  > 10° Chigher than that today.

The Cretaceous, which occurred approximately 145 million to 66 million years ago, was one of the warmest periods in the history of Earth.

The poles were devoid of ice and average temperatures of up to 35 degrees Celsius prevailed in the oceans.

New research shows there was a severe cold snap during the geological age known for its extreme greenhouse climate.

Geologists believe that the commercial diamond deposits were formed in the mantle which are delivered to the surface by deep source volcanic eruptions.

Diamonds are found in several rock types. The primary commercial host rocks are kimberlite and lamproite.

Kimberlite is an igneous rock which contains diamonds.

The rock is named after the town of Kimberley in South Africa.

Lustre is an important property of a mineral that can help us to identify different minerals.

There are two main types of lustre – metallic, similar to that from a piece of metal and non-metallic.

There are several subtypes of non-metallic lustre viz. adamantine (diamond), vitreous (quartz), resinous (sphalerite), pearly (feldspar), greasy (graphite), and silky (asbestos)

There are various waves in the atmosphere and oceans. Wavy motions result from the conservation of potential vorticity is Rossby waves.

Kelvin waves balance the Coriolis force against a topographic boundary in the ocean or atmosphere. Shallow water gravity waves are external gravity wave.

These are the ‘long wave approximation’ end of gravity waves. These can exist only in internal density discontinuity or free surface.

The most important factor that results in the seasonal temperature changes in the climate is the changing angle at which the sun rays strike the surface of the earth. Since the earth is round, the sun rays strike the surface at different angles at different places.

The angle formed by the sun ray with the tangent of the earth’s circle at a point is called angle of incidence. When the sun is almost overhead, the rays of the sun are vertical.

The angle of incidence is large hence; they are concentrated in a smaller area, giving more amount of insolation at that place.

If the sun rays are oblique, the angle of incidence is small and sun rays have to heat up a greater area, resulting in less amount of insolation received there.

A large part of the oceanic biological production comes from phytoplankton. Phytoplanktons are also known as photoautotrophs. These are harvesting light to convert inorganic to organic carbon, and they supply this organic carbon to diverse heterotrophs organisms that obtain their energy solely from the respiration of organic matter.

Open ocean heterotrophs include bacteria as well as more complex single- and multi-celled zooplankton (floating animals), nekton (swimming organisms, including fish and marine mammals), and the benthos (the seafloor community of organisms).

Lightning is discharge of electricity, a giant spark, that occurs in mature thunderstorms. Lightning is actually a flow of electrical current through the air. Rain falling from a thunderstorm will often evaporate before reaching the ground (virga). Lightning then strikes dry ground, starts a fire, and there isn’t any rain to put out or at least slow the spread of the fire. The occurrence of lightning with no rain is called dry lightning. When lightning strikes the ground positive charge is deposited on the ground.

Detoxification is the increase of heavy metals in ocean water. Acididification is the ongoing decrease in the pH of the Earth’s oceans.

Deoxygenation is the expansion of the oxygen minimum zone in the world’s ocean. These three functions are not ecologically advantageous.

Bioturbation functions are the reworking of soils and sediments by plants and animals. So, this functions are performed by marine benthic polychaetes is ecologically advantageous.

Shoaling is the effect by which surface waves entering shallower water change in wave height. Refraction is the change in direction of propagation of any wave as a result of its travelling at different speeds at different points along the wave front.

Shoaling and refraction processes most commonly occur when a surface gravity wave propagates into a shallow water region from deep water because the wave propagates from surface to gravity, where shoaling effect occurs and for the change in speed of the wave, refraction occurs.

Groynes are constructed transverse to the river flow. It extends from the bank into the river up to a limit.

They are also known as spurs, dikes or traverse dikes.

Siliceous ooze is siliceous pelagic sediment. It covers large areas of the deep ocean floor. Siliceous oozes consist predominantly skeletons made of silica. These sediment types commonly occur in ocean in trenches.

Foraminifera ooze are mostly widespread in both Atlantic and Indian oceans. Pteropod ooze is found only in the mid-Atlantic.

Hadal region are found from a depth of around 6,000 to 11,000 metres (20,000 to 36,000ft) to the bottom of the ocean. That much of depth is not suitable for Autotrophic phytoplankton. Autotrophic phytoplanktons are present in the ultra-oligotrophic marine regions cold, lowly illuminated surface waters, and euphotic layers laden with marine snow.

Albedo means whiteness in latin. Albedo is the measure of the diffused reflection of solar radiation out of the total solar radiation received by an astronomical body.

Surface albedo will be increased, and the net amount of solar radiation held by the Earth will be reduce when a reduction in the solar insolation-induced air temperature and results as snow fields and ice sheets expand.

Air temperature will be reduced further, resulting in glacial expansion.

Tides occur in characteristic patterns along the coastlines of different regions of the earth given in figure below. Tides are classified into three common types.

A semidiurnal tidal cycle is characterized by two high tides daily of about equal magnitudes

In a mixed tidal cycle, the tides also occur twice daily, but the two high tides and two low tides are unequal magnitudes.

A diurnal tidal cycle is characterized by a single high tide.

Two high and two low of unequal magnitudes tidal patterns characterizes the West coast of India.

Magma is formed at three main plate-tectonic settings:

divergent boundaries where melting happens by decompression

convergent boundaries where flux melting occurs as a result of water being released from slabs of subducting ocean crust

mantle plumes where hot mantle material is decompressed as it rises up from deep within the mantle, and can cause eruptions away from plate boundaries both on land and in the ocean

A mantle plume is an ascending column of hot rock (not magma) that originates deep in the mantle, possibly just above the core-mantle boundary. Mantle plumes are believed to form where convection currents in the earth’s mantle cause narrow columns of hot mantle rock to rise and spread radially outward at convergence zones. Many of the volcanic islands of the Pacific Ocean may have originated from a mantle plume like Hawaiian Islands.

Major elements are conservative because there are so much of them in sea water relative to their rate of supply via rivers and other sources. They have very long replacement (residence) times in sea water relative to the mixing time of the ocean, which is less than a thousand years.

Hjulstrom Curve have critical erosion velocity curve and mean settling velocity curve. The critical erosion curve shows the minimum velocity needed to transport and erode a particle. The mean settling velocity shows the minimum speed that particles of different sizes will be deposited by the river.

Small particles seem to have an erosive velocity that is the same as the velocity for larger particles. This is because smaller particles are cohesive, they stick together, making them harder to dislodge and erode without high velocities.

The winds that blow from sub-tropical high-pressure areas towards equatorial low-pressure areas called trade or easterly winds. Because of the Coriolis effect, the northern trade winds move away from the subtropical high in north-east direction.

In southern hemisphere, the trade winds diverge out of the sub-tropical high towards the equatorial low from the southeast direction. As the trade winds tend to blow mainly from the east, they are also known as the tropical easterlies.

The winds are constant in strength and direction. Trade winds sometimes contain intense depressions.

During spheroidal weathering, water seeps along the joints to this bedrock and causes disintegration and composition at their edges. At corner, water can enter from many direction causes decomposition, disintegration which changes the sharp corner to round.

Mainly, water and water vapour are the media for chemical reactions within the rocks. Pure water, distilled water is chemically inert. But when it mixes with atmospheric gases, chemical reaction takes place which leads to chemical weathering.

The Indian Ocean Dipole is an irregular oscillation of sea-surface temperatures in which the western Indian ocean becomes alternatively warmer and then colder than the eastern part of the ocean.

The Indian ocean dipole involves an aperiodic oscillation of sea-surface temperatures between positive and negative phases.

The Eastern Indian Ocean is colder than the western Indian Ocean and excess anomalous rainfall in the East Africa conditions co-occur with the positive Indian Ocean Dipole.