Geography is scientific in its orientation and hence only the candidates having comprehensive understanding of the subject can answer all the questions of geography for the IAS Prelims Exam. Geography is so vast in its syllabus that it covers most section of the General Studies for the IAS Prelims Exam. The candidates cannot escapes or overlook the geography portion because there are various aspects of geography which enormously helps in the overall General Studies Preparations. So, it’s advisable to prepare geography from standard sources starting with NCERTS.
Origin and Evolution of Earth
Q1. Which of the following are correctly matched?
a)The moon- The big Splat theory
b)Origin of universe- The Big Bang theory
c)Evolution of earth- The Nebula Hypothesis
d)All are correctly matched
In 1950, Otto Schmidt and Carl Weizascar gave the ‘nebular hypothesis’, that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion. The most popular argument regarding the origin of the universe is the Big Bang Theory. It is also called expanding universe hypothesis. Edwin Hubble, in 1920, provided evidence that the universe is expanding. It is generally believed that the formation of moon, as a satellite of the earth, is an outcome of ‘giant impact’ or what is described as “the big splat”.
Q2. Arrange the following in the order of shortest to longest duration on Geological Time Scale?
The geological time scale (GTS) is a system of chronological dating that relates geological strata to time, and is used by geologists to describe the timing and relationships of events that have occurred during Earth’s history.
Evidence from radiometric dating indicates that Earth is about 4.54 billion years old. The deep of Earth’s past has been organized into various units according to events which took place in each period. Different spans of time on the GTS are usually marked by changes in the composition of strata which correspond to those, and indicate major geological events such as mass extinctions.
Q3. Consider the following statements regarding Nebular theory of Laplace?
1.The sun was surrounded by solar nebula containing mostly the hydrogen and silicon.
2.The collision of particle led to formation of a disk-shaped cloud and planets were formed through the process of accretion.
Choose the correct statements?
c)Both 1 and 2
d)None of the above
Nebular Hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating. Later in 1950, Otto Schmidt in Russia and Carl Weizascar in Germany somewhat revised the ‘nebular hypothesis’, though differing in details.
1.They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust.
2.The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.
Q4. Which one of the following processes is related to the formation or modification of the present atmosphere?
d)All of the above
The present composition of earth’s atmosphere is chiefly contributed by nitrogen and oxygen. The first stage is marked by the loss of primordial atmosphere. In the second stage, the hot interior of the earth contributed to the evolution of the atmosphere. Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis.
The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds. During the cooling of the earth, gases and water vapour were released from the interior solid earth. The process through which the gases were outpoured from the interior is called degassing. Continuous volcanic eruptions contributed water vapour and gases to the atmosphere.
Q5. Choose the correct statements regarding inner planets?
a)Planets between the sun and the earth.
b)Planets between the sun and the belt of asteroids.
c)Planets in gaseous state.
d)Planets without satellite(s)
Our Solar system consists of eight planets. Our solar system consists of the sun (the star), 8 planets, 63 moons, millions of smaller bodies like asteroids and comets and huge quantity of dust-grains and gases. Out of the eight planets, Mercury, Venus, Earth and Mars are called as the inner planets as they lie between the sun and the belt of asteroids the other four planets are called the outer planets. Alternatively, the first four are called Terrestrial, meaning earth-like as they are made up of rock and metals, and have relatively high densities. The rest four are called Jovian or Gas Giant planets. Jovian means Jupiter-like.
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Q6. Consider the following statements regarding the characteristics of Terrestrial Planets?
1.The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles.
2.The terrestrial planets are larger than Jovian planets and their lower gravity could hold the escaping gases.
Choose the correct statement?
c)Both1 and 2
d)None of the above
The first four planets are called Terrestrial, meaning earth-like as they are made up of rock and metals, and have relatively high densities. The rest four are called Jovian or Gas Giant planets. Jovian means Jupiter-like. Most of them are much larger than the terrestrial planets and have thick atmosphere, mostly of helium and hydrogen.
(i) The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location.
(ii) The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.
(iii) The terrestrial planets are smaller and their lower gravity could not hold the escaping gases.
Q7. Which of the following statements are incorrect regarding formation of stars?
a)A galaxy (large number of stars) starts to form by accumulation of helium gas.
b)The formation of stars is believed to have taken place some 5-6 million years ago.
c)The initial density difference in early universe is the core reason for star formation.
d)Both (a) and(b)
The distribution of matter and energy was not even in the early universe. These initial density differences gave rise to differences in gravitational forces and it caused the matter to get drawn together. These formed the bases for development of galaxies. A galaxy contains a large number of stars. Galaxies spread over vast distances that are measured in thousands of light-years. A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula. Eventually, growing nebula develops localized clumps of gas. These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars. The formation of stars is believed to have taken place some 5-6 billion years ago.
Q8. What are ‘planetesimals’ associated with theories of planet formations?
a)They are formed by cohesion of small rounded bodies of condensed gas cloud with the matter around the core.
b)They are a combined object formed around the comets and meteorites.
c)Large number of dwarf planets form one planetesimal.
d)None of the above
Development of planets:
(i) The stars are localized lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.
(ii) In the next stage, the gas cloud starts getting condensed and the matter around the core develops into small rounded objects. These small-rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collision, and gravitational attraction causes the material to stick together. Planetesimals are a large number of smaller bodies.
(iii) In the final stage, these large number of small planetesimals accrete to form a fewer large bodies in the form of planets.
Q9.Seismology helps us understand the origin and intensity of earth’s interior. Consider the following statements regarding Seismic waves?
1.All seismic waves are mechanical waves and require medium to propagate.
2.Their behavior change with the change in medium
Choose the correct option?
c)Both 1 and 2
d)None of the above
Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer.
The propagation velocity of the waves depends on density and elasticity of the medium. Velocity tends to increase with depth and ranges from approximately 2 to 8 km/s in the Earth's crust, up to 13 km/s in the deep mantle. The refraction or reflection of seismic waves is used for research into the structure of the Earth's interior, and man-made vibrations are often generated to investigate shallow, subsurface structures.
Q10. Which of the following statements regarding our solar system are incorrect?
a)The distance between celestial bodies are measured by light years.
b)All the planets were formed in the same period sometime.
c)Our Solar system consists of nine planets.
d)All the statements are correct
Our Solar system consists of eight planets. The nebula from which our Solar system is supposed to have been formed started its collapse and core formation some time 5-5.6 billion years ago and the planets were formed about 4.6 billion years ago. Our solar system consists of the sun (the star), 8 planets, 63 moons, millions of smaller bodies like asteroids and comets and huge quantity of dust-grains and gases. All the planets were formed in the same period sometime about 4.6 billion years ago. Till recently (August 2006), Pluto was also considered a planet. However, in a meeting of the International Astronomical Union, a decision was taken that Pluto like other celestial objects discovered in recent past may be called ‘dwarf planet’.
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