Geomorphology MCQ Quiz - Objective Question with Answer for Geomorphology - Download Free PDF

The Earth is divided into three main layers. The dense, hot inner core, the molten outer core, the mantle, and the thin crust, which supports all life in the known universe.

Interior of the earth:

• Earth's interior is generally divided into three major layers: the crust, the mantle, and the core.
• The hard, brittle crust extends from Earth's surface to the so-called Mohorovicic discontinuity, nicknamed the Moho.
• The Moho is not located at a uniform depth, but about 10 kilometers (6 miles) below the seafloor and about 35 kilometers (22 miles) beneath the surface of continents.
• Beneath the Moho is the mantle, the viscous layer that makes up more than half of Earth's volume.
• The mantle is divided from the core by the Gutenberg discontinuity, about 2,880 kilometers (1,798 miles) beneath Earth's surface.
• The outer core is molten and liquid iron and nickel, while the inner core is solid and much denser than either iron or nickel at the surface.
• The crust forms only 1 percent of the volume of the earth, 84 percent consists of the mantle and 15 percent makes the core

Hence, the correct sequence of the layers of the earth by their volume in decreasing manner is Mantle → Core → Crust

The plate tectonic mechanism:

• The motion of tectonic plates is driven by convection in the mantle.
• In simple terms, convection is the idea that dense, cold things sink, and buoyant, warm things rise.
• In the earth the cold sinking things are slabs (subducting plates) and the warm things are plumes, or just rising material from deeper in the mantle.

The forces that drive Plate Tectonics include:

There are three main forces that determine the rate at which tectonic plates move as part of the mantle convection system:

• Slab pull: the force due to the weight of the cold, dense sinking tectonic plate
• Ridge push: the force due to the buoyancy of the hot mantle rising to the surface beneath the ridge.
• Viscous drag: the force opposing motion of the plate and slab past the viscous mantle underneath or on the side.

The convective curent mechanism:

• Convection Current Theory is the soul of Seafloor Spreading Theory.
• Arthur Holmes in 1930s discussed the possibility of convection currents in the mantle.
• These currents are generated due to radioactive elements causing thermal differences in the mantle.
• The movement of the lithospheric plates is caused by the movement of the magma in the mantle.

The Earth is divided into four main layers: the solid crust on the outside, the mantle, the outer core, and the inner core.

Interior of the Earth:

Crust:

• The uppermost layer over the earth’s surface is called the crust.
• It is the thinnest of all the layers.
• On the continental masses, It is about 35 km and on the ocean floors, only 5 km.
• The crust is the thinnest layer of the Earth and it amounts to less than 1% of our planet's volume.
• The earth is made up of several concentric layers with one inside another, just like an onion.
• The crust is the outermost layer of Earth and is made up of igneous, metamorphic, and sedimentary rocks. 
• The Earth's crust is unstable because of the exogenic forces.

Mantle:

• The Mantle extends up to a depth of 2900 km below the crust.
• It is the widest section of the Earth.
• The uppermost part of the mantle is known as the asthenosphere.

Core:

• The innermost layer is the core with a radius of about 3500 km.
• The central core has a very high temperature and pressure.
• The inner core (1200 km) is in the solid state whereas the outer core (2300 km) is in the liquid state.
• The innermost layer is the core with a radius of about 3500 km and divided into Inner and Outer cores.

Hence, the correct order of the layer of the earth is outward from the center is Inner core > outer core > lower Mantle > Asthenosphere > Crust

Discontinuity:

• All those layers are separated from each other through a transition zone.
• These transition zones are called discontinuities.
• Conrad Discontinuity: It lies between the Upper crust and Lower crust.
• Mohorovicic Discontinuity: It lies between crust and mantle.
• Repiti Discontinuity: It lies between the Upper mantle and Lower mantle.
• Gutenberg Discontinuity: It lies between core and mantle.
• Lehman Discontinuity: It lies between the upper core and lower core.​

The Earth is divided into three main layers. The dense, hot inner core (yellow), the molten outer core (orange), the mantle (red), and the thin crust (brown), which supports all life in the known universe. Click through this gallery to learn more about the mantle and the rest of Earth's interior.

Key Points

Source of volcanic material from Mantle:

• Geologists have long believed that solidified volcanic lava, or basalt, originates in the mantle, the molten rock just below the crust. 
• The mantle is the most solid bulk of Earth's interior.
• The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust.
• The mantle is about 2,900 kilometers (1,802 miles) thick and makes up a whopping 84% of Earth’s total volume.
• The upper mantle extends from the crust to a depth of about 410 kilometers (255 miles).
• The upper mantle is mostly solid, but its more malleable regions contribute to tectonic activity.
• Two parts of the upper mantle are often recognized as distinct regions in Earth’s interior: the lithosphere and the asthenosphere.
• The asthenosphere is the denser, weaker layer beneath the lithospheric mantle.
• It lies between about 100 kilometers (62 miles) and 410 kilometers (255 miles) beneath Earth’s surface.
• The temperature and pressure of the asthenosphere are so high that rocks soften and partly melt, becoming semi-molten.
• The lava that erupts from volcanic fissures is actually the asthenosphere itself, melted into magma.

Hence, the volcanic material has its origin in the mantle.

The Earth is divided into three main layers. The dense, hot inner core, the molten outer core, the mantle, and the thin crust, which support all life in the known universe.

Important Points

Interior of the earth: 

• Earth's interior is generally divided into three major layers: the crust, the mantle, and the core.
• The hard, brittle crust extends from Earth's surface to the so-called Mohorovicic discontinuity, nicknamed the Moho.
• The Moho is not located at a uniform depth, but about 10 kilometers (6 miles) below the seafloor and about 35 kilometers (22 miles) beneath the surface of continents.
• Beneath the Moho is the mantle, the viscous layer that makes up more than half of Earth's volume.
• The mantle is divided from the core by the Gutenberg discontinuity, about 2,880 kilometers (1,798 miles) beneath Earth's surface.
• The outer core is molten and liquid iron and nickel, while the inner core is solid and much denser than either iron or nickel at the surface.
• The crust forms only 1 percent of the volume of the earth, 84 percent consists of the mantle and 15 percent makes the core

Key Points

Characteristics of the Crust:

• The uppermost layer over the earth’s surface is called the crust.
• It is the thinnest of all the layers.
• It is about 35 km. on the continental masses and only 5 km. on the ocean floors.
• The main mineral constituents of the continental mass are silica and alumina.
• It is thus called sial (si-silica and al-alumina).
• The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium)
• The crust makes up only 1% of the volume of Earth.

Hence, 84% by volume constitute by the crust is not true about the crust.

The correct answer is outer core.

Important Points

• The interior of the earth is divided into three parts namely Crust, Mantle, and Core.
• The core is the innermost layer of the earth.
• The radius of the innermost layer(core) is about 3500 km.
• The core is made up of material constituted by nickel and iron.
• The temperature and pressure of the central core are very high.

Key Points

• The core is further subdivided into two layers called the outer core and inner core.
• The outer core of the earth is in a liquid state.
• The inner core is in solid-state
• The outer core is responsible for the earth's magnetic field.

Additional Information

• The crust is the outermost of the earth.
  • It is brittle in nature.
  • it the thinnest layer of Earth.
  • The thickness of the crust varies under the oceanic and continental areas.
• The mantle is the second layer in the interior of the earth.
  • The mantle extends from Moho’s discontinuity to a depth of 2,900 km.
  • The upper portion of the mantle is called the asthenosphere.

The correct answer is 4.

Important Points

• Based on historical seismic activity, the Bureau of Indian Standards has categorized regions in India into four seismic zones: zones II, III, IV and V.
• Of these, the most seismically active area is Zone V and the least active is Zone II. 
• There is a history of devastating earthquakes on the Indian subcontinent.
• The key cause for the high frequency and severity of earthquakes is that the Indian plate is driving into Asia at a rate of roughly 47 mm/year.
• India's geological figures indicate that about 54 percent of the land is prone to earthquakes.
• Research by the World Bank and the United Nations predicts that by 2050, about 200 million urban dwellers in India will be vulnerable to storms and earthquakes.
• The most recent edition of India's seismic zoning map given in India's earthquake-resistant design code [IS 1893 (Part 1) 2002] assigns four degrees of seismicity in terms of zone factors for India.
• In other words, unlike its previous edition, which consisted of five or six zones for the region, India's earthquake zoning map divides India into four seismic zones (Zone 2, 3, 4, and 5).
• According to the new zoning map, the maximum degree of seismicity is predicted in Zone 5, while the lowest level of seismicity is correlated with Zone 2.

Revised earthquake hazard zone map of India

Option 2 is correct, i.e. Aluminium.

Key Points

• Aluminium is the most plentiful (most abundant) of metals in the crust of the earth.
• Aluminium is around 8.1 per cent of the total metals on the surface of the earth.

Important Points

• The most plentiful non-metal in the earth's surface is Oxygen.
• The most plentiful metalloid in the crust of the earth is Silicon.
• O > Si > Al > Fe > Ca are the most abundant elements in the earth crust.

The correct answer is L waves.

Key Points

• L waves, or Love waves, are one type of surface wave in seismic activity.
  • Named after British mathematician A.E.H. Love, who first mathematically predicted their existence.
  • Love waves move the ground from side to side in a horizontal plane perpendicular to the direction of propagation.
  • As they travel along the Earth's surface, they cause horizontal shearing and produce entirely horizontal motion.
  • L waves are the slowest of all seismic waves and therefore the last to be recorded by seismographs.
  • These waves are particularly damaging to the foundations of structures due to their horizontal motion.

Additional Information

• P waves:
  • P waves, or Primary waves, are body waves that travel through the interior of the Earth.
  • They are the fastest seismic waves and thus the first to be detected by seismographs.
  • P waves cause particles to move in the same direction as the waves, creating a push-and-pull motion.
• S waves:
  • S waves, or Secondary waves, are also body waves that move through the Earth's interior.
  • They are slower than P waves but faster than surface waves.
  • S waves cause particles to move perpendicular to the wave direction, creating an up-and-down or side-to-side motion.
• R waves:
  • Also known as the Rayleigh wave.
  • It has both compressional and shear motions.
  • These waves result from the interaction of P-waves and vertically polarized S-waves with the surface and can exist in any solid medium.

• Block mountains are the type of mountains in which the middle part of the mountain is lower and the parts on both sides are higher. 
• The middle part is known as the rift valley. 
• Black Forest (Germany), Salt Range (Pakistan), Vindhya and Satpura (India) are examples of block mountains. 
• The Ural is a fold mountain. Fold mountains are formed because of folds in the rocks due to the internal movements of the earth. 
• Block mountains - 

The correct answer is 30 km.

Key Points

• Earth’s crust:
  • The interior of the earth is made up of several concentric layers which are the crust, the mantle, the outer core and the inner core.
  • The crust is the outermost layer of the earth making up 0.5-1.0% of the earth’s volume and less than 1% of Earth’s mass.
  • Materials that initially stayed in their liquid phase during this process, called “incompatible elements,” ultimately became Earth's brittle crust. 
  • The lower layer of the crust consists of basaltic and ultra-basic rocks.
  • Density increases with depth, and the average density is about 2.7 g/cm3 (the average density of the earth is 5.51 g/cm³).
  • The thickness of the crust varies in the range of 5-30 km in the case of the oceanic crust and 50-70 km in the case of the continental crust.
  • The mean thickness of the oceanic crust is approximately 7 km, while the mean thickness of the continental crust is about 35-40 km.

Important Points

The correct answer is Increases

Key Points

• A rise in temperature with an increase in depth is observed in mines and deep wells.
• These evidence along with molten lava erupted from the earth’s interior supports that the temperature increases towards the centre of the earth.
• While in the upper 100kms, the increase in temperature is at the rate of 120C per km and in the next 300kms, it is 200C per km. But going further deep, this rate reduces to a mere 100C per km.
• It is assumed that the rate of increase in the temperature beneath the surface is decreasing towards the centre.
• Temperature is always increasing from the earth’s surface towards the centre.
• The temperature at the centre is estimated to lie somewhere between 30000C and 50000C, maybe that much higher due to the chemical reactions under high-pressure conditions.

​

The correct answer is Sandstone.

• Sandstone is NOT a metamorphic rock.

Key Points

• Metamorphic rocks are rocks that have become changed by intense heat or pressure while forming.
  • In the very hot and pressured conditions deep inside the Earth's crust, both sedimentary and igneous rocks can be changed into metamorphic rock.
  • ​Metamorphic rock can be formed locally when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior.
    • Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.
  • Marble, Slate, and quartz are formed after metamorphism. They changed in their original form due to extreme temperatures and pressure.
  • The three types of metamorphism are Contact, Regional, and Dynamic metamorphism.
  • Contact Metamorphism occurs when magma comes in contact with an already existing body of rock.

Additional Information

• Sandstone :
  • Sandstone is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material.
    • It also contains a cementing material that binds the sand grains together and may contain a matrix of silt- or clay-size particles that occupy the spaces between the sand grains.
  • Sandstone is a sedimentary rock composed mostly of quartz sand, but it can also contain significant amounts of feldspar, and sometimes silt and clay.
  • Sandstone that contains more than 90% quartz is called quartzose sandstone.

The correct answer is sedimentary rock.

Important Points

• Sedimentary rocks are formed by deposition, sedimentation, and lithification of sediments over a long period of time.
• Sedimentary rocks may also contain fossils of plants, animals that once lived on them.
• The word ‘sedimentary’ is derived from the Latin word "sedimentum".
• Shale, limestone, and conglomerate are some other examples of sedimentary rocks.

Key Points

• Sandstone is an example of sedimentary rock.
• Sandstone is made from grains of sand.

Additional Information 

• A rock is an aggregate of one or more minerals.
• Igneous rock is formed due to the cooling, solidification, and crystallization of hot and molten magma.
  • Granite, Basalt, Gabbro are examples of Igneous rocks.
• Metamorphic rocks are made up of sedimentary rock and igneous rock which have been subjected to high pressure and temperature.
  • Clay changes into slate and limestone into marble are the examples of metamorphic rocks.
• Marble and quartzite are examples of non-foliated metamorphic rocks.

The correct answer is Tethys Sea.

Important Points

• India is a part of Gondwana land.
• Around 200 million years ago, the large landmass called Panagea started splitting into two large continental masses called Laurasia and Gondwana.
• Gondwana was a supercontinent.
• It existed from the Neoproterozoic period until the Jurassic period.
• Laurasia is a continental mass in the Northern Hemisphere.
• It includes North America, Europe, and Asia except peninsular India.
• The Tethys Sea was an ocean during the Mesozoic era.

Additional Information

• The Black Sea separates Europe and Asia.
• The Red Sea lies between Africa and Arabia.
• The pacific ocean extends from the Arctic Ocean in the North to the Southern Ocean in the South.