External forces MCQ Quiz - Objective Question with Answer for External forces - Download Free PDF

Key Points

• Physical weathering is caused by various factors, including temperature fluctuations. As rocks are exposed to heating and cooling, they expand and contract, which leads to the physical breakdown of the rock over time.
• This process is called "thermal stress" or "thermal expansion," and it plays a key role in weathering, especially in environments with significant daily or seasonal temperature changes. Hence, Statement-I is correct.
• The process described in Statement-II is known as frost wedging or freeze-thaw weathering. When water enters the cracks in rocks and freezes, it expands, exerting pressure on the rock. As the ice melts and refreezes, the cycle continues, eventually causing the rock to break apart.
• This is a form of physical weathering directly tied to temperature fluctuations, as freezing and thawing depend on temperature changes. Hence, Statement-II is correct, and it explains Statement-I. 
• Wind erosion is a form of weathering, particularly in desert regions where wind carries small particles that sandblast rock surfaces, gradually wearing them down. However, this is a separate process from temperature-based physical weathering.
• Wind erosion is mechanical and involves abrasion by particles, not temperature changes. Hence, Statement-III is correct, but it does not explain Statement-I.

The correct answer is physical weathering.

Key Points

• Exfoliation is a type of physical weathering that involves the peeling away of layers of rock.
• This process often occurs in areas with significant temperature fluctuations, causing the rock to expand and contract.
• Over time, the stress from temperature changes leads to the separation of the outer layers of the rock.
• Exfoliation can be observed in large rock formations, especially in mountainous regions and granite domes.

Additional Information

• Physical Weathering:
  • It is the process of breaking down rocks into smaller pieces without changing their chemical composition.
  • Common agents of physical weathering include temperature changes, frost action, and the activity of living organisms.
  • Examples of physical weathering processes include freeze-thaw cycles, exfoliation, and abrasion.
• Chemical Weathering:
  • It involves the chemical alteration of minerals within the rock, leading to its breakdown.
  • Common agents include water, oxygen, carbon dioxide, and various acids.
  • Examples include oxidation, hydrolysis, and carbonation.
• Mass Wasting:
  • It refers to the downslope movement of soil and rock under the influence of gravity.
  • Examples include landslides, rockfalls, and soil creep.
• Biochemical Weathering:
  • It is the breakdown of rocks through the chemical and physical actions of organisms.
  • Examples include the production of organic acids by plant roots and the burrowing activities of animals.

The Correct answer is Gravitational and Centrifugal force. Key Points

• Together, the gravitational pull and the centrifugal force are responsible for creating the two major tidal bulges on the earth.
• The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide.
• when the tide is channelled between islands or into bays and estuaries they are called tidal currents.
• On the side of the earth facing the moon, tidal bulges occur while on the opposite side though the gravitational attraction of the moon is less as it is farther away, the centrifugal force causes tidal bulges on the other side. Additional Information 
• Gravitation- 
  • Everybody attracts another body by a force called the force of gravitation.
  • The force of gravitational attraction between two point bodies is directly proportional to the product of their masses and inversely proportional to the square of the distances between them.
• Centrifugal force-
  • Centrifugal force is such a pseudo force(the forces which can not be assigned to any object in the surrounding).
  • It is equal and opposite to Centripetal force.
  • Cream separator and centrifugal drier work on the principle of centrifugal force.

The correct answer is Salt crystal growth.

Key Points

• Chemical Weathering
  • Chemical weathering in geology is the process by which rocks are slowly broken down through chemical reactions, often resulting in a different substance entirely.
  • A cluster of weathering processes namely solution, carbonation, hydration, oxidation, and reduction. Hence Option 2 is correct.
  • These processes act on rocks to decompose, dissolve or moderate them to a fine clastic state through chemical reactions by oxygen, surface/ soil water, and other acids.
  • Water and air along with heat must be present to speed up all chemical reactions.
• Solution
  • When substances are dissolved in acids or water, then the water or acid with dissolved substances is called a solution.
  • This process includes the removal of solids in solution and depends upon the solubility of a mineral in weak acids or water.
• Carbonation
  • Carbonation is the reaction of bicarbonate and carbonate with minerals.
  • It is a general process helping the fragmentation of feldspars and carbonate minerals.
  • Carbon dioxide from the soil and atmospheric air is absorbed by water to form carbonic acid that acts like weak acid.
• Hydration 
  • Hydration is the chemical addition of water.
    Minerals take up water and enlarge.
  • This enlargement causes an increase in the volume of the material itself or rock.
• Oxidation and Reduction
  • In weathering, oxidation denotes a mixture of a mineral with oxygen to form hydroxides or oxides.
    Oxidation happens where there is ready access to the oxygenated waters and atmosphere.
  • The minerals commonly involved in this process are manganese, sulphur, iron, etc.
  • When oxidised minerals are positioned in a situation where oxygen is absent, the reduction occurs.
  • Such circumstances exist commonly below the water table, on waterlogged ground and in areas of stagnant water.
  • These weathering processes are interconnected.

The correct answer is Glacial.

Key Points

Glacial Landforms:

• A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and water that originates on land and moves downslope under the influence of its own weight and gravity. 

​Erosional Landforms:

• Glacial Valleys/Troughs:
  • ​These valleys are trough-like and U-shaped with broad floors and relatively smooth, and steep sides.
  • The valleys may contain littered debris or debris shaped as moraines with a swampy appearance.
  • Very deep glacial troughs filled with seawater and making up shorelines (in high latitudes) are called fjords/fiords.
• Cirques:
  • Often are found at the heads of glacial valleys, these are the most common of landforms in glaciated mountains.
  • They are deep, long and wide troughs or basins with very steep concave to vertically dropping high walls at their head as well as sides.
  • A lake of water can be seen quite often within the cirques after the glacier disappears. Such lakes are called cirque lakes or tarn lakes.
• Horns and Serrated:
  • Ridges Horns form through headward erosion of the cirque walls.
  • If three or more radiating glaciers cut headward until their cirques meet, high, sharp-pointed and steep-sided peaks called horns form.

Additional Information

Depositional Landforms:

• Glacial Till:
  • ​The unassorted coarse and fine debris dropped by the melting glaciers is called glacial till.
  • Some amount of rock debris small enough to be carried by such melt-water streams is washed down and deposited.
  • Such glaciofluvial deposits are called outwash deposits.
  • The outwash deposits are roughly stratified and assorted.
• Moraines:
  • ​They are long ridges of deposits of glacial till.
  • Terminal moraines are long ridges of debris deposited at the end (toe) of the glaciers.
  • Lateral moraines form along the sides parallel to the glacial valleys.
  • Many valley glaciers retreating rapidly leave an irregular sheet of till over their valley floors called ground moraines.
• Eskers:
  • ​These are ridges made of sands and gravels, deposited by glacial meltwater flowing through tunnels within and underneath glaciers, or through meltwater channels on top of glaciers.

The correct answer is Erosion.

Key Points

• Geologic Erosion or "natural" erosion, is the action of the wind, water, ice and gravity in wearing away rock to form soil and shape the ground surface. Except for some stream and shore erosion, it is a relatively slow, continuous process that often goes unnoticed.

Additional Information

• Accelerated Erosion is the speeding up of erosion due to human activity. Whenever we destroy the natural vegetation or alter the contour of the ground without providing some sort of surface protection, we greatly increase the rate of erosion.
• Soil erosion is the process of detachment transportation and deposition of soil particles by wind, water or other phenomenon.
• Water erosion is the process of detachment transportation and deposition of soil particles by water.

Weathering

• Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the earth.
• Weathering occurs when physical processes affect the rock, such as changes in temperature or when the rock is exposed to the effects of wind, rain, and waves.
• Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.
• Thus, this weathering which leads to both the mechanical breakup of rocks and the chemical weathering of minerals contributes to soil formation.
• Therefore, weathering leads to soil formation.

Metamorphosis

• Metamorphosis is the process by which animals undergo rapid physical changes sometime after birth. Examples of metamorphosis include the process undergone by most insects and the transformation of tadpoles into frogs.

Sedimentation

• Sedimentation is the process of allowing solid particles in suspension in water to settle out of the suspension under the effect of gravity.
• The particles which settle down during sedimentation are called sediments.
• This method is used for the separation of insoluble substances which are heavier than liquid or water.
• In this process, heavier components of the mixture settle on the bottom on their own due to gravity.

The correct answer is Sea waves.

• Sea waves are not an outcome of endogenic forces.

Key Points

• Endogenic forces:
  • These forces are also called Internal Forces.
  • The forces originating in the interior of the earth are called the internal or the endogenic forces.
  • Volcanic eruptions, Earthquakes, and Landslides are examples of internal forces.
• Exogenic Forces:
  • These forces are also called External Forces.
  • The forces affecting the surface of the earth from outside are called the external or exogenic forces.
  •  Weathering and Erosion are examples of external forces.
• Sea waves are the outcomes of wind and gravitational energy.

The Correct Answer is Option 1 i.e Endogenic Forces.

• Endogenic forces:
  • These are internal forces that originate from within the surface of the earth. ​​
  • These internal forces lead to vertical and horizontal movements and result in subsidence, land upliftment, volcanism, faulting, folding, earthquakes, etc.
  • Mountain Building on the surface of the earth is a result of the Endogenic Force.
• Exogenic forces:
  • These are external forces, that occur on or above the earth's surface.
  • Weathering, mass wasting, erosion, and deposition are the main exogenic processes.
• Gravitational Force
  • The gravitational force is a force that attracts any two objects with mass.
  • Examples include the force that holds the gases in the sun and the force that causes a ball you throw in the air to come down again.
  • This is the weakest force among all the fundamental forces.
• Magnetic Force:
  • It is an attractive force between two moving charges.
  • Examples of magnetic force are a compass, a motor, train tracks, etc.

The correct answer is Building mountains.Key Points

• Endogenic forces are the forces that originate from within the Earth's crust and result in the formation of landforms.
• Building mountains is an example of endogenic forces as it involves tectonic activity where two tectonic plates collide, leading to the uplift of the Earth's crust and the formation of mountains.
• Glaciers are a result of exogenic forces (external forces) such as changes in climate and weather patterns.
• Sea-waves are a result of exogenic forces such as wind patterns, tides, and ocean currents.
• Wind is also result of an exogenic force that shapes the Earth's surface by eroding and depositing sediments.

Additional Information

• The Himalayas, the Andes, and the Rockies are examples of mountain ranges formed due to tectonic activity.
• Glaciers are large masses of ice that form in high-altitude areas where the temperature is below freezing.
  • They are formed due to a combination of factors such as temperature, precipitation, and topography.
  • Glaciers can shape the landscape by eroding rocks, creating valleys, and leaving behind moraines (piles of rocks and debris).
• Sea-waves are created due to a combination of factors such as wind patterns, tides, and ocean currents.
  • They can shape the coastline by eroding rocks, creating sea cliffs, and depositing sediments to form beaches.
• Wind is a result of differences in atmospheric pressure that cause air to move from high-pressure areas to low-pressure areas.
  • Wind can shape the Earth's surface by eroding rocks, creating sand dunes, and depositing sediments to form landforms such as deltas.

The correct answer is Cirque.

Cirque:

• They are usually formed at the top of the glacial valley.
• They are deep long basins with steep concave high vertical walls.
• It is a type of glacial landform formed due to erosion by the glaciers.

Key Points

• A depositional landform is a landform that was created due to glacial deposition.

Stalagmite:

• They are similar to stalactite in shape but are formed from the floor of the cave towards the roof.
• It is a type of landform formed by underground water deposition.

Pillar: 

• When a Stalactite and a stalagmite come together, they form a complete pillar.
• It is a type of landform formed by underground water deposition. 

Moraines:

• It is a landform formed due to glacier deposition.

• It is formed due to the accumulation of glacial debris or till.

The correct answer is Erosion.

Key Points

•  Exogenic force
  • ​Exogenic forces, often known as external forces, are those that originate in the earth's atmosphere or get their energy from the outside of the planet.
  • While pressure that arises from within the earth is referred to as endogenic forces, also known as internal forces.
  • Denudation, which meaning to strip off or uncover, is a broad term used to describe all exogenic processes.
  • Geomorphic agents are the parts of nature that can carry out these exogenic processes (or exagenic geomorphic agents). the waves, water, wind, etc.

Additional Information

• ​The atmosphere, which is influenced by the sun's primary energy as well as the gradient that tectonic forces create, provides the exogenic forces with their energy.
• Slopes on the earth's surface are mostly produced by tectonic pressures or earth movements brought on by endogenic processes, 

The correct answer is Wind.

Key Points

•  Exogenic force:-​
  • ​Exogenic forces, often known as external forces, are those that originate in the earth's atmosphere or get their energy from the outside of the planet.
  • While pressure that arises from within the earth is referred to as endogenic forces, also known as internal forces.
  • Denudation, which means to strip off or uncover, is a broad term used to describe all exogenic processes.
  • Geomorphic agents are the parts of nature that can carry out these exogenic processes (or exogenic geomorphic agents). the waves, water, wind, etc. (Hence option 3 is correct)
• Wind:-
  • The movement of air from high-pressure areas to low-pressure areas is called wind.
  • There are three kinds of winds including permanent, seasonal, and local winds.

Additional Information

• Landslide:-
  • A landslide is the movement of rock, earth, or debris down a sloped section of land.
  • Landslides are caused by rain, earthquakes, volcanoes, or other factors that make the slope unstable. 
• Earthquake​:-​
  • A sudden shaking of the ground causes greater destruction to human life and is termed an earthquake.
• Volcano:-  
  • A Volcano is basically an opening in the Earth’s crust through which heated, materials usually in the form of magma are ejected out to the surface of Earth.

The correct answer is Loess .

Key Points

• Loess plains are formed due to wind deposits. 
• When the wind carries light and fine grains of sand and when this sand is deposited in large areas, it is called loess.
• Large deposits of Loess is found in China.
• Loess covers the 500km part of Kashmir Valley in northwestern India.

 Thus, we can say that Loess plains are formed due to wind deposits.

The correct answer is Exfoliation.

Key Points

Chemical weathering:

• Chemical weathering is the process of chemical decomposition of rocks and soil.
• Chemical weathering involves the rock interacting with chemicals to alter the rock's composition.
• A cluster of weathering processes namely solution, carbonation, hydration, oxidation, and reduction. 
• These processes act on rocks to decompose, dissolve or moderate them to a fine clastic state through chemical reactions by oxygen, surface/ soil water, and other acids.
• Water and air along with heat must be present to speed up all chemical reactions.

Additional Information

Exfoliation:

• Over time, sheets of rock break away from the exposed rocks along the fractures, a process known as exfoliation. Hence, option 4 is correct.
• Exfoliation due to pressure release is also known as “sheeting“.
• Temperature changes can also contribute to mechanical weathering in a process called thermal stress.
• The surface layers of the rocks tend to expand more than the rock at depth, and this leads to the peeling off of the surface layers (exfoliation).

The correct answer is option 2, i.e Karst landforms.

Key Points

• Many depositional forms develop within the limestone caves.
• The chief chemical in limestone is calcium carbonate which is easily soluble in carbonated water (carbon dioxide absorbed rainwater).
• Stalagmites may take the shape of a column, a disc, with either a smooth, rounded bulging end or a miniature crater-like depression.
• Stalactites hang as icicles of different diameters. Normally they are broad at their bases and taper towards the free ends showing up in a variety of forms.