Physical Geography (UPSC) (Part-I)

Total Questions: 50

31. Along which one of the following meridians did India experience the first light of the sunrise of the new millennium? [2000]

Correct Answer: (d) 92°30' E  
Solution:

The first light of the sunrise of new millenium in India experienced at Kathal island of Andaman and Nicobar, which is located at 92 °30 E meridian.
The prime meridian is a special line that helps us measure places on Earth. It is like a zero point for measuring how far east or west a place is. The prime meridian runs through Greenwich, England, and it has a longitude of 0 degrees. The opposite of the prime meridian is called the antimeridian, and it is located 180 degrees away from the prime meridian.

32. Consider the following statements: [2000]

  1. Tides are of great help in navigation and fishing.
  2. High tide enables big ships to enter or leave the harbour safely   
  3. Tide prevents siltation in the harbours
  4. Kandla and Diamond Harbour are tidal ports

Which of these statements are correct?

Correct Answer: (d) 1, 2, 3 & 4
Solution:All the given statements are true.
• Tides are the regular, predictable rise and fall of ocean water levels along coastlines, caused by the gravitational forces exerted by the moon and the sun on Earth’s oceans, combined with Earth’s rotation.
• The gravitational pull of the moon is the primary force driving tides, while the sun also contributes, though to a lesser extent. When the moon’s gravity pulls on Earth’s oceans, it creates a bulge of water, causing the high tide.
• The areas perpendicular to the bulge experience low tide, as the water is pulled away. The Earth’s rotation causes different locations to pass through these high and low tide phases throughout the day.
• Tides occur in cycles, typically every 12 hours and 25 minutes, creating two high and two low tides daily (semi-diurnal tide).
• In some regions, tides may be diurnal (one high and one low tide per day). Tides are crucial for coastal ecosystems, navigation, and marine life.

33. Consider the following statements about the 'Roaring Forties': [2000]

  1. They blow uninterrupted in the northern and Southern Hemispheres
  2. They blow with great strength and constancy
  3. Their direction is generally from north-west to east in the Southern Hemisphere  
  4. Overcast skies, rain and raw weather are generally
    associated with them

Which of these statements are correct?

 

Correct Answer: (b) 2, 3 & 4
Solution:

The Roaring Forties are strong westerly winds that blow in the Southern Hemisphere between 40° and 50° South latitudes.
• The powerful west-to-east air currents are created by a combination of air being driven from the Equator towards the South Pole, the Earth’s rotation, and the scarcity of land masses at such latitudes to serve as windbreaks.
• The Furious Fifties and the Shrieking or Screaming Sixties are two similar but considerably stronger conditions that occur in more southerly latitudes.
• The roaring forties are places in the Southern Hemisphere between latitudes 40° and 50° south where the predominant winds are constantly from the west.
• Throughout the year, the roaring forties experience strong, often gale-force winds. The sailors who were the first to enter these latitudes gave them names.
• These powerful prevailing winds pushed ships across the Pacific throughout the Age of Sail (approximately 15th to 19th centuries), frequently at breakneck speed.
• Nonetheless, traveling west into heavy waves and severe headwinds, especially across Cape Horn at South America’s southern point, might take weeks, making it one of the world’s most dangerous sailing crossings.

34. Which one of the following weather conditions is indicated by a sudden fall in barometer reading? [2001]

Correct Answer: (a) Stormy
Solution:In stormy weather condition the pressure of atmosphere varies, which causes sudden fall in barometer reading.
A barometer is an instrument used to measure air pressure as it varies with distance either above or below sea level. Italian scientist Evangelista Torricelli invented the barometer in the year 1643. He studied the characteristics of mercury when placed in a vacuum and used that theory to develop the first barometer.
The working of a barometer depends on balancing mercury weight in the glass tube with respect to the atmospheric pressure. If the weight of the mercury is less than atmospheric pressure, the mercury level will increase. And if the weight of the mercury is more than the atmospheric pressure, the mercury level will decrease. The rising and falling of the mercury are measured using the inch scale marked on the glass tube.

35. Who amongst the following was the first to state that the earth was spherical? [2001]

Correct Answer: (a) Aristotle
Solution:Aristotle in 340 B.C first stated that the earth was spherical in his book "On the Heaven".
He noted that different constellations become visible as one travels north or south. He observed that Earth’s shadow on the moon during a lunar eclipse was always round. While Aristotle’s arguments were groundbreaking, the idea of a spherical Earth may have been considered or proposed by earlier thinkers. However, Aristotle was one of the first to offer concrete physical evidence and a well-reasoned argument, rather than simply a philosophical idea.

36. If the stars are seen to rise perpendicular to the horizon by an observer, he is located on the: [2001]

Correct Answer: (a) Equator
Solution:If the stars are seen to rise perpendicular to the horizon by an observer then the observer is at the equator because celestical equator is an imaginary circle around the sky directly above the earth's equator. It is always 90° from the pole. All the stars rotate in a path that is parallel to the celestical equator.

37. Consider the following statements made about sedimentary rocks: [2001]

  1. Sedimentary rocks are formed at Earth's surface by the hydrological system
  2. Formation of sedimentary rocks involves the weathering of preexisting rocks
  3. Sedimentary rocks contain fossils
  4. Sedimentary rocks typically occur in layers

Which of these statements are correct?

Correct Answer: (d) 1, 2, 3 & 4
Solution:All the statements are true about the sedimentary rock.

• Sedimentary rocks are formed by lithification — consolidation and compaction of sediments.
• Hence, they are layered or stratified of varying thickness. Example: sandstone, shale etc.
• Sediments are a result of denudation (weathering and erosion) of all types of rocks.
• These types of rocks cover 75 per cent of the earth’s crust but volumetrically occupy only 5 per cent (because they are available only in the upper part of the crust).
• Ice deposited sedimentary rocks are called till or tillite. Wind-deposited sediments are called loess.
• They are formed by mechanical agents like running water, wind, ocean currents, ice, etc.
• Arenaceous sedimentary rocks have more sand and bigger sized particles and are hard and porous. They form the best reservoirs for liquids like groundwater and petroleum. E.g. sandstone.
• Argillaceous rocks have more clay and are fine-grained, softer, mostly impermeable (mostly non-porous or have very tiny pores). E.g. claystone and shales are predominantly argillaceous.

38. Volcanic eruptions do not occur in: [2001]

Correct Answer: (a) Baltic Sea
Solution:Volcanic eruptions do not occur in the Baltic Sea.
In case of Baltic sea, the Baltic sea does not lie in between the tectonic plates but instead the basathic rock found in Baltic sea is transported by glacier so volcanic eruptions do not occur in Baltic sea.
About Volcanism
• Volcanism is a term describing geological processes under which the magma, gases, and volcanic materials are released from the Earth’s interior to the surface.
• They are chiefly driven by the movement of tectonic plates and happen at divergent boundaries, convergent zones, and hot spots. In an eruption, magma appears as lava, which cools and solidifies to form igneous rocks.
• Volcanoes, being the surface expressions of volcanism, come in several forms: shield volcanoes, stratovolcanoes, and cinder cones, with each having its own typical lava composition and eruption style.
• Volcanic activity is explosive, carrying ash, pyroclastic flows, and gases, or it can be effusive, characterized by the steady outpouring of lava.
• Although in popular connotation, volcanism bears destruction—damaging property, taking lives, and influencing climates—there are many benefits too.
• It matures soils, provides geothermal energy, and continues to mold the Earth.
• The study of volcanism helps geologists in terms of predicting eruptions, understanding the processes within Earth, and reducing hazards caused by volcanoes so that people can be better prepared and resilient.

39. Quartzite is metamorphosed from: [2001]

Correct Answer: (c) sandstone
Solution:Quartzite is a metamorphosed form of sandstone.
• Metamorphic rocks are formed when pre-existing rocks (igneous, sedimentary, or other metamorphic rocks) are subjected to high pressure, temperature, or chemically active fluids, causing physical and chemical changes.
• Subtypes:
○ Foliated Metamorphic Rocks: These have a layered or banded appearance due to the alignment of minerals under pressure (e.g., schist, slate).
○ Non-Foliated Metamorphic Rocks: These lack a layered structure and are often composed of a single mineral or a homogenous texture (e.g., marble, quartzite).

40. Identify the correct order of the process of soil-erosion from the following: [2001]

Correct Answer: (a) Splash erosion, Sheet erosion, Rill erosion, Gully erosion
Solution:The correct order of soil erosion process is splash erosion, sheet erosion, rill erosion and gully erosion. Splash occurs when the raindrop hits the surface; explosive impact soil into individual particles.

Sheet erosion is the detachment of soil particles by rain drop and their removal down slope by water flowing overland as a sheet in definite channels. Rill erosion refers to the development of small ephemeral concentrated flow paths which function as both sedimentary source and sediment delivery systems for erosion on hill slopes.

Sheet erosion removes the this top layer by raindrop kill or orion occurs in lines which are less than 30 cm deep when these rills are deeper than 30 forming channels are called as gully erosion. Gully erosion occurs when water flows in narrow channels after heavy rain and melting snow.