Geomorphology: UPSC Previous Year Questions (Geography)

Explanation

Factors of The Dynamic Changes of the Earth:

Electromagnetic radiation from the sun, particularly in the form of solar energy, drives atmospheric and surface processes such as weathering, erosion, and the water cycle. These processes contribute to the continuous reshaping of Earth’s surface. Geothermal energy originates from Earth’s internal heat, which fuels volcanic activity and drives plate tectonics. These internal processes lead to the formation of new landforms, mountain building, and seafloor spreading, all of which dynamically alter Earth’s surface. Gravity influences the movement of water, sediments, and tectonic plates. It plays a crucial role in processes like mass wasting (landslides), river flow, and glacial movement which contributes to the dynamic changes on Earth’s surface. The movement of tectonic plates leads to continental drift, mountain formation, earthquakes, and volcanic activity. Rotation of the Earth causes the Coriolis effect, which deflects moving air and water, influencing weather patterns, ocean currents, and thus affecting erosion and deposition. It also contributes to the tides. Revolution of the Earth around the sun, combined with its axial tilt, causes the seasons. Seasonal variations in temperature and precipitation influence weathering, erosion, and the activity of living organisms, all of which contribute to surface changes. Thus, all of the above are responsible for bringing dynamic changes on the surface of the earth. Since all the listed factors contribute to dynamic changes, the correct answer is option (d).

Explanation

Below the mantle, the core is divided into two main parts: the outer core and the inner core. Outer Core: This layer is in a liquid state and is primarily composed of iron mixed with nickel and small amounts of other elements. The movement of this liquid iron alloy is responsible for generating Earth’s magnetic field. Inner Core: At the center of the Earth lies the inner core, a solid sphere predominantly made up of iron. Its high density and the immense pressure it is subjected to keep it in a solid state despite the high temperatures.

Explanation

Statement 1 is incorrect: The Earth’s magnetic axis is tilted at approximately 11 degrees relative to its geographic axis (the axis around which the Earth rotates). The 23.5-degree tilt refers to the Earth’s rotational axis relative to its orbit around the Sun, which is responsible for the seasons, not the magnetic field.

Statement 2 is correct: The North Magnetic Pole is currently located in the Arctic region of Northern Canada, specifically on Ellesmere Island. The magnetic poles are not fixed and move over time due to changes in the Earth’s magnetic field.

Statement 3 is correct: The magnetic equator is an imaginary line where the Earth’s magnetic field is entirely horizontal (no dip angle). The magnetic equator passes near Thumba in South India. The Thumba Equatorial Rocket Launching Station was established in this location due to its proximity to the magnetic equator.

Explanation

Statement 1 is correct: The total land area of the Earth is approximately 1475 lakh square kilometers or 147.5 million square kilometers. The Earth’s surface area is about 510 million square kilometers, with land covering roughly 29% of it.

Statement 2 is incorrect: About 71% of the Earth’s surface is covered by water and 29% is land. This gives a land-to-water ratio of approximately 1:2.4 and not 1:4 as mentioned in the question.

Statement 3 is correct: The Pacific Ocean is the largest and deepest ocean, covering an area of about 168 million square kilometers. It contains the maximum percentage of Earth’s water, contributing significantly to the planet’s hydrosphere.

Explanation

The correct order of continents in terms of their percentage of Earth’s land area is:

Asia > Africa > North America > South America > Antarctica > Europe > Australia. The sequence that accurately reflects the decreasing order of land area is:

Africa: Second largest continent, covering 20.3% of Earth’s land area. North America: Third largest continent, covering 16.3% of Earth’s land area. South America: Fourth largest continent, covering 12.0% of Earth’s land area. Europe: Sixth largest continent, covering 6.8% of Earth’s land area.

Explanation

Option (a) is correct: Aristotle was the first to provide empirical evidence for the Earth’s spherical shape. In his work On the Heavens (De Caelo), he argued that the Earth must be a sphere based on observations such as:

The way ships disappear hull-first over the horizon. The circular shadow of the Earth on the Moon during a lunar eclipse. The changing position of stars when traveling north or south. These arguments strongly supported the idea that the Earth was not flat but spherical. Options (b), (c) and (d) are incorrect:

Nicolaus Copernicus is known for formulating the heliocentric model, which proposed that the Sun, not the Earth, was at the center of the universe. Claudius Ptolemy, an astronomer and geographer, expanded on the spherical Earth concept in his famous work Almagest. He developed the geocentric model (Earth-centered universe), which became dominant for over a thousand years. Strabo was a Greek geographer who described the Earth’s shape as a sphere in his work Geographica. But he relied on earlier works, especially those of Aristotle and Eratosthenes.

Explanation

Common types of Sedimentary rocks include sandstone, shale, limestone, and conglomerates. They often host resources like coal, petroleum, and natural gas.

Statement 1 is correct: Sedimentary rocks form through the accumulation and lithification of sediments. The hydrological system (water cycle) plays a crucial role in their formation, as water transports, deposits, and compacts sediments. Rivers, lakes, oceans, and glaciers contribute to sediment deposition.

Statement 2 is correct: Sedimentary rocks originate from weathered materials of pre-existing rocks (igneous, metamorphic, or other sedimentary rocks). Weathering processes (physical, chemical, and biological) break down rocks into smaller particles. These sediments are transported and deposited before undergoing compaction and cementation to form sedimentary rocks.

Statement 3 is correct: Fossils are primarily found in sedimentary rocks because these rocks form in low-temperature and low-pressure environments that preserve organic remains. Limestone, shale, and sandstone commonly contain fossils.

Statement 4 is correct: Sedimentary rocks typically occur in distinct horizontal layers or strata, reflecting different periods of deposition. This characteristic layering is a key identifier of sedimentary rocks.

Explanation

Volcanic eruptions are mostly associated with tectonic activity, particularly along plate boundaries along divergent boundaries (e.g., mid-ocean ridges), convergent boundaries (e.g., Pacific "Ring of Fire") and hotspots (e.g., Hawaii).

Option (a) is correct: The Baltic Sea is located in a tectonically stable region of Northern Europe, far from active plate boundaries. This stability means that volcanic activity is entirely absent in and around the Baltic Sea. Options (b), (c) and (d) are incorrect:

Caspian Sea: Although primarily tectonically stable, certain nearby areas (like the Caucasus Mountains) exhibit minor geological and volcanic activity. Black Sea: While not highly active, the Black Sea contains regions with dormant and extinct volcanic formations, indicating past geological and volcanic activity. Caribbean Sea: Located along an active tectonic boundary, where the Caribbean Plate interacts with the North American Plate. Known for volcanic islands like Montserrat, St. Lucia, and Martinique, it is a region of frequent volcanic eruptions.

Explanation

Option (c) is correct: Quartzite is a metamorphic rock that forms when quartz-rich sandstone undergoes metamorphism due to intense heat and pressure. The process causes the quartz grains in the sandstone to recrystallize, forming a hard, dense rock with interlocking quartz crystals.

Option (a), (b) and (d) are incorrect:

Limestone metamorphoses into marble due to recrystallization of calcite under high pressure and heat. Famous for its use in sculpture and architecture. Obsidian: Not a metamorphic rock but an igneous rock that forms from the rapid cooling of lava, creating volcanic glass. Shale metamorphoses into slate, which can further transform into phyllite, schist, or gneiss with increasing metamorphic grade.

Explanation

Soil erosion is a natural process involving the detachment, transportation, and deposition of soil particles, primarily due to water or wind. The stages of water-induced soil erosion occur in the following sequence: Splash Erosion Sheet Erosion Rill Erosion Gully Erosion Fig: Stages of Water Induced Soil Erosion 1. Splash Erosion: This is the initial stage of erosion where raindrops hit bare soil surfaces, dislodging soil particles. It creates a loose layer of soil vulnerable to further erosion by runoff. 2. Sheet Erosion: A thin, uniform layer of soil is removed over a large area by surface runoff. In this stage, a thin, uniform layer of soil is washed away over a large area by surface runoff, without noticeable channels. Often goes unnoticed but contributes significantly to soil loss. 3. Rill Erosion: When runoff becomes concentrated, it forms small channels or rills in the soil. Rills disrupt agricultural fields and increase erosion intensity.

4. Gully Erosion: As rills expand and deepen, they turn into gul-lies, creating large channels that severely degrade the land and make it unsuitable for cultivation. The most destructive stage, often requiring intensive reclamation efforts.