Geography · General Awareness

Geology and Earth Structure

1,268 Questions

Geology and Earth Structure explores the physical composition of the planet, including its layers, tectonic plates, and seismic activity. This topic is a core component of geography and general science sections in various competitive exams. Reviewing these concepts builds a solid foundation for answering questions related to natural phenomena.

Layers of the EarthTectonic PlatesEarthquakes and VolcanoesGeomagnetism ApplicationsGeophysical MethodsLandform Formation

Geology and Earth Structure Questions

Multiple choice

What is the purpose behind using the term 'death and taxes' in the passage?

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

  1. To draw the similarity between them and magnetic reversal

  2. To state that death and taxes are sure

  3. To draw the difference between them and magnetic reversal

  4. To state a hypothesis put forward earlier

  5. To show how taxes cause deaths
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The first two lines of the passage indicate the answer.

Multiple choice

Which of the following statements are correct?

I. In earthquakes, shocks are generated at a point known as the epicentre. II. The point of origin of shock may be within the crust or mantle. III. Most earthquake-prone areas are at the margins of tectonic plates.

  1. I and III

  2. I and II

  3. II and III

  4. I, II and III
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The point of origin of shock may be within the crust or mantle, and most earthquake-prone areas are at the margins of tectonic plates. There are two main causes of earthquakes. Also, statement I is not correct. The point where earthquake shocks are generated is called its "Focus". The point directly above the "Focus" on the earth's surface is its "Epicentre".

  

Multiple choice

Which of the following is a major tectonic plate?

  1. Philippine Plate

  2. Arabian Plate

  3. Cocos Plate

  4. India-Australia-New Zealand Plate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The India-Australia-New Zealand Plate (also called the Indo-Australian Plate) is one of the major tectonic plates covering approximately 0.2% of Earth's surface. The Philippine Plate, Arabian Plate, and Cocos Plate are smaller, minor plates. Major plates include: Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic plates.

Multiple choice

Which of the following options is part of the lithosphere?

  1. Crust and lower mantle

  2. Core and crust

  3. Upper core and mantle

  4. Crust and top mantle
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The lithosphere is Earth's rigid outer layer consisting of the crust and the uppermost solid mantle (approximately 100 km thick). It is broken into tectonic plates. The asthenosphere below it is the ductile part of the mantle. Options A, B, and C are incorrect because they include the lower mantle, core, or combinations that don't constitute the lithosphere.

Multiple choice

Assertion (A): The structure of the interior of the earth is deduced with the help of seismic waves. Reason (R): The 'S' wave travel in solid, liquid and gas while the 'P' waves travel only in solid.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are correct but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The structure of Earth's interior is indeed deduced using seismic waves (Assertion A is true). However, Reason R is false because it reverses the facts: P-waves (Primary) can travel through solids, liquids, AND gases, while S-waves (Shear) can ONLY travel through solids. This difference in behavior is actually what helps scientists understand Earth's internal structure.

Multiple choice

Moho-discontinuity is found between the

  1. crust and mantle

  2. upper mantle and lower mantle

  3. mantle and core

  4. inner core and outer core
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Mohorovicic discontinuity (Moho) is the boundary between Earth's crust and the mantle, discovered by Andrija Mohorovicic in 1909. It is characterized by a sharp increase in seismic wave velocity (from about 6-7 km/s to 8+ km/s) due to the change in composition from crustal rocks to denser mantle rocks (peridotite).

Multiple choice

Assertion (A): The outer core of the earth's interior is in molten state while the inner core is in solid state. Reason (R): The P-seismic waves disappear in outer core while S-waves penetrate up to the inner core.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are correct but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Correct Answer: (A) is true but (R) is false. The Earth was discovered to have a solid inner core distinct from its liquid outer core in 1936, by the seismologist Inge Lehmann, who deduced its presence by studying seismograms from earthquakes in New Zealand; she observed that the seismic waves reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface. Typical values for P-wave velocity in earthquakes are in the range 5 to 8 km/s. The precise speed varies according to the region of the Earth's interior, from less than 6 km/s in the Earth's crust to 13 km/s through the core.  

Multiple choice

Which of the following phenomena causes the shape of Earth?

  1. Internal structure

  2. Atmospheric pressure

  3. Rotation

  4. Revolution
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Earth's shape is an oblate spheroid - slightly flattened at the poles and bulging at the equator. This is caused by Earth's rotation. The centrifugal force from rotation is strongest at the equator, causing material to bulge outward there. The equatorial diameter is about 43 km greater than the polar diameter. Revolution (orbit around the Sun) and atmospheric pressure do not affect shape.

Multiple choice

The upper portion of the mantle is called

  1. lithosphere

  2. aethenosphere

  3. photosphere

  4. atmosphere
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The asthenosphere (spelled 'aethenosphere' in this question) is the upper, mechanically weak layer of the mantle, extending from about 100-200 km depth to 660 km. It lies beneath the lithosphere. The lithosphere is the rigid outer layer, while photosphere relates to the Sun, and atmosphere is the gaseous envelope surrounding Earth.

Multiple choice

Which of the following statements is/are not true in relation to earthquake?

  1. The point of rupture is called the 'focus' and may be located near the surface or deep below it.

  2. Earthquake whose focus lies more than 300 km below the earth's surface is called 'deep focus earthquakes'.

  3. Deep focus earthquakes are very destructive.

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Deep focus earthquakes are rarely destructive because by the time the waves reach the surface, the impact reduces. Shallow focus earthquakes are more common and are extremely damaging because of their proximity to the surface.

Multiple choice

With reference to earthquakes, which one of the following statements is not correct?

  1. S waves move objects at right angles to their direction of motion.

  2. S waves propagate through liquids.

  3. As the P waves propagate, they move material in a path parallel to the direction of movement.

  4. L waves travel along the surface of the earth's crust.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

S waves (shear waves) can only propagate through solids because they require the medium to resist shear stress. Liquids cannot support shear stress, so S waves cannot travel through them. This is why S waves cannot pass through Earth's liquid outer core. The statement 'S waves propagate through liquids' is incorrect, which is exactly what the question asks for (which statement is NOT correct).

Multiple choice

The circum Pacific belt is highly prone to the occurrence of earthquakes because it is a zone of

  1. divergent plate boundaries

  2. young folded mountains

  3. active volcanoes

  4. convergent plate boundaries
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The circum Pacific belt (Ring of Fire) is primarily located along convergent plate boundaries where plates collide, creating intense seismic and volcanic activity. These convergent boundaries involve subduction zones, volcanic eruptions, and frequent earthquakes. Divergent boundaries create new crust and are associated with different geological features, not the Ring of Fire.