CSIR NET Earth Science Mock Test - 3 Free Online Test 2026

The feldspars are the most prominent group of rock-forming tectosilicate minerals that make up about 41% of the earth’s continental crust by weight.

The feldspars crystallize from the magma as veins in both the intrusive and the extrusive igneous rocks.

They are also present in various types of metamorphic rock.

The mineral occurs in the form of densely packed mass of small garin-like crystals, in the case of globular structure. Example: Chromite.

When the general water table is much below the minimum water level in the reservoir, permeability of the rocks along the base and the flanks is taken into consideration

Choice of the right method will, therefore, be possible only when the nature of the rocks and the ground all along the alignment is fully known. This is one of the most important aim and object of geological investigations.

The behaviour of a mineral towards the forces that tend to break, bend, cut or crush it is described by the term tenacity. Thus, when a mineral can be cut with a knife, it is described as sectile

Some minerals are not only flexible but elastic, that is, they regain their shape when the force applied on them is removed. Micas are best example. Hence they are both flexible and elastic.

Permeability of a rock measures the ability of a porous material to allow fluids to pass through it.

It depends on the size of the rock, interconnection, distribution, and volume of the pores of the rock.

The permeability of some rocks in increasing order of permeability is given below:

Coarse-grained rocks are usually more permeable than fine-grained rocks, and sands are more permeable than clays.

Well-rounded coarse-grained sediments usually have higher porosity than fine-grained sediments, because the grains do not fit together well.

Gulf streams are warm currents, which originate in the Gulf of Mexico from north equatorial current and move in north easterly direction along the eastern coast of North America and reaches the western coasts of Europe near 70^oN latitude.

Brazil current is a warm current, which originate in the Brazilian coast near Sun Rock from south equatorial current and moves southward along the east coast of South America upto 40^oS latitude.

Kuroshio is a warm current, which originates near Philippines from north equatorial current and moves in north easterly direction along the eastern coast of Asia towards pole.

Agulhas current is warm current, which originates near Madagascar from south equatorial current and moves southward along the eastern coast of Madagascar and joins Mozambique current up to the southern tip of the southern tip of Africa and ultimately diverted eastward.

In destructive plate boundaries, two plates moves towards each other and destroyed at subduction zones. Andes Mountain in South America is an example of Ocean-continent destructive plate boundaries.

In Constructive Plate boundaries, two plate move apart from each other and mainly forms by seafloor spreading or new ocean basin. The Atlantic ocean formed through rifting of a continent (Pangaea).

In conservative plate boundaries two plates past each other. The Pacific plate moves northwestward relative to the north American plate causing San Andreas Fault.

The Carlsberg Ridge is the northern section of the Central Indian Ridge, a divergent tectonic plate boundary between the African Plate and the Indo-Australian Plate.

The Southeast Indian Ridge (SEIR) is a mid-ocean ridge in the southern Indian Ocean. A divergent tectonic plate boundary stretching almost 6,000 km between the Rodrigues Triple Junction in the Indian Ocean and the Macquarie Triple Junction in the Pacific Ocean

The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from (north to south) the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate.

The Ninety East Ridge (also rendered as Ninetyeast Ridge, 90E Ridge or 90°E Ridge) is a linear structure on the Indian Ocean floor named for its near-parallel strike along the 90^th meridian at the center of the Eastern Hemisphere.

The Mariana is one of many deepwater ocean trenches formed by the geologic process of subduction. This occurs when a plate topped by oceanic crust is subducted beneath another plate topped by oceanic crust.

Its deepest point on earth is at 11,000 m.

Tidal range varies due to changes in the position and alignment of the Moon and Sun relative to Earth. Every 15 days, the largest tidal ranges in semi-diurnal regions occur during spring tides, when the Moon and Sun are in phase around times of new or full Moon; while the smallest tidal ranges occur during neap tides, when the Moon and Sun are out of phase.

In diurnal regions, the largest tidal ranges occur every 15 days during equatorial tides, when the Moon is over the tropics while smallest tidal ranges occur during tropic tides, when the Moon is over the equator.

Tidal range changes as the Moon moves from its closest (perigee) approach to Earth, to its furthest approach (apogee) and back when we discuss about in a month’s time.

Annually, tidal range changes occur as the Sun’s position varies north or south of the equator, and as it moves from its closest to furthest approach to Earth and back. The largest semi-diurnal tidal range occurs during the equinoxes (March and September), while the largest diurnal tidal range occurs during the solstices .

Earth’s core is predominantly Iron metal (Fe). It has also a significant amount of the element Nickel (Ni, about 4%) and a light element to make it less dense (about 10 % by mass).

This light element is either mostly oxygen or sulfur. Chemical composition of Earth’s core is similar to that of Iron meteorites.

These are remnants of small planetary bodies from early in our solar-system’s history that segregated small cores.

The chemical composition of Iron meteorites is dominated by the elements Fe, Ni and Co, which make up more than 95%.

Ocean information is collected using different types of remote sensing techniques such as optical, thermal, and microwave. Infrared sensors give information about sea surface temperature. Satellites are useful tools for observing the earth and the ocean that covers more than 70% of the planet.

By remote sensing data collected from their orbits high above the earth, satellites provide us much more information than would be possible to obtain merely from the surface.

Information gathered by satellites can tell us about ocean bathymetry, sea surface temperature, ocean colour, coral reefs, and sea and lake ice.

Chemical weathering is decomposition and disintegration of rocks due to chemical reactions. Water and water vapour are the media which activate several types of chemical reactions within the rocks and on the landscape,

Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to contamination of drinking water sources and other consequences.

Urbanization demands canals and drainage and leads to salt water intrusion to group water.

Urbanization also affects both the quality and quantity of groundwater table. Increase in vehicle, industry etc due to urbanization also leads to increased dust production. It also leads to decrease in the infiltration of rainwater.

The United States Department of Agriculture (USDA) classified soil into twelve soil orders based on the origin, composition, and other features.

Among which Entisols are the most extensive, occupying about 18% of the earth’s ice-free land area.

According to the classification of tropical storms by the World Meteorological Organization, several categories of storm and their maximum sustained wind speeds are given as:

The ocean conveyor belt circulation starts in the Norwegian Sea, where warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes. This loss of heat to the atmosphere makes the water cooler and denser, causing it to sink to the bottom of the ocean. As more warm water is transported north, the cooler water sinks and moves south to make room for the incoming warm water.

This cold bottom water flows south of the equator all the way down to Antarctica. Eventually, the cold bottom waters returns to the surface through mixing and wind-driven upwelling, continuing the conveyor belt that encircles the globe.

A subtropical gyre is a ring-like system of ocean currents rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere caused by the Coriolis Effect.

The Gauss-Matuyama polarity boundary was a result of one geologic event, Gauss-Matuyama. It was happened approximately 2.58 million years ago when the earth’s magnetic field underwent reversal.

This event is useful in dating sediments. This events separates the Piacenzian from the Gelasian. The beginning of the Quaternary period broadly coincides with the Gauss-Matuyama polarity boundary.

There is the tropical wet evergreen forest that grows in those areas where the annual rainfall exceeds 250 Cm. The annual temperature is about 25 degrees Celsius to 27 degrees Celsius the average annual Liberty exceeds 77% and the dry season is short. Due to high heat and humidity, the trees of these forests do not shed their leaves annually at least not together and a termed evergreen forests. These are lofty, very dense multi-layered forests with mesophytic evergreens. The trees often reach 45 meters in height individual trees exceed 60 meters.

Iron is essential for cell growth, metabolism and function in waters. Iron is an essential micronutrient for phytoplankton, being involved in cellular processes such as photosynthesis, nitrate reduction, N₂ fixation as well as providing protection from reactive oxygen species. It is also essential elements is the most critical for the growth and production of diatoms in the Antarctic waters.

The ocean conveyor belt circulation starts in the Norwegian Sea, where warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes. This loss of heat to the atmosphere makes the water cooler and denser, causing it to sink to the bottom of the ocean. As more warm water is transported north, the cooler water sinks and moves south to make room for the incoming warm water.

This cold bottom water flows south of the equator all the way down to Antarctica. Eventually, the cold bottom waters returns to the surface through mixing and wind-driven upwelling, continuing the conveyor belt that encircles the globe as the diagram given below:

A subtropical gyre is a ring-like system of ocean currents rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere caused by the Coriolis Effect as the diagram given below:

On an upper-level chart, normally we find warm air associated with high pressure and cold air associated with low pressure.

As the air warms up the molecules in the air become more active and they use up more individual space even though there is the same number of molecules. This causes an increase in the air pressure.

When the air cools down, the molecules slow down and they do not move and bump into each other. This causes a decrease in air pressure.

Slides are failures along a surface of separation, over which the failed mass slides downhill.

Translational slides indicate movement of en masse over a surface separating two different types of material.

This slide is downslope movement of material along the surface of weakness (such as- fault, joint bedding plane).

Rotational slide is downward slope movement of material along the curved surface.

Debris flow is large masses of soil with rock fragments moves down the slopes into streams, channel and form deposits on the valley.

Debris Avalanche is sudden collapse from unstable side of volcano, volcanic cones are unstable because of sudden growth of volcanic cones.

Granite domes are domical hills composed of granite with bare rock exposed over most of the surface. Generally, domical features such as these are known as bornhardts. Bornhardts can form in any type of plutonic rock but are typically composed of granite and granitic gneiss.

When a number of mountain ranges and ridges continue for extensive distances for thousands of kilometres maintaining their characteristic features throughout, the resulting complex structure is called a mountain belt or chain

Cirrostratus clouds are example of high clouds. Due to the presence of low temperatures and small quantities of water vapour at high altitudes, the high clouds are thin and white and they are made up primarily of ice crystals.

Altostratus clouds are considered as middle clouds because they are found at an altitude of 2,000 to 6,000 meters.

Nimbostratus and stratus clouds are considered as low clouds.