Geomorphology — UPSC Prelims Geography previous year questions

All three statements give evidence for continental drift.
Statement I: The ancient rock belts of the Brazil coast match those of western Africa. This suggests the two coasts were once joined.
Statement II: The gold deposits of Ghana are thought to come from the Brazil plateau. This suggests the continents lay side by side.
Statement III: The Gondwana sediments of India have counterparts in six southern landmasses. This points to one southern super-continent.
So I, II and III are correct.
Remember: Alfred Wegener proposed continental drift in 1912.

Source: NCERT Class XI Fundamentals of Physical Geography, Ch. 4 (Distribution of Oceans and Continents)

Statement I is correct. Chalk is very permeable. Clay is almost impermeable.
Statement II is correct. Chalk is porous and absorbs water. Its pores are connected, so water flows through it. This explains Statement I.
Statement III is incorrect. Clay is porous, but its pores are tiny and poorly connected. Water cannot pass through it easily.
So only Statement II is correct, and it explains Statement I. Option (c) fits.
Remember: Porosity is how much water a rock can hold. Permeability is how easily water flows through it.

Source: NCERT Class XI Fundamentals of Physical Geography, Ch. 6 (Geomorphic Processes); standard physical geography texts on porosity and permeability

All four are volcanic products. Pyroclastic debris means fragments of rock thrown out in an eruption. Ash and dust are the finest of these fragments. Volcanic gases include sulphur compounds such as sulphur dioxide. They also include nitrogen compounds.
So the count is four. The options 'only one', 'only two' and 'only three' leave out at least one real product.
Remember: volcanic ejecta are solid (pyroclasts), liquid (lava) and gaseous (gases and vapour).

Source: NCERT Class XI Fundamentals of Physical Geography, Interior of the Earth (Volcanism)

Statement-I is correct. Rain water takes part in chemical weathering.
Statement-II is correct. Dissolved carbon dioxide forms weak carbonic acid. This acid dissolves limestone in a process called carbonation.
Statement-III is correct. Dissolved oxygen reacts with iron-bearing minerals. This is oxidation, and it makes rocks crumble.
Both II and III explain I. Each is a chemical process driven by rain water.
Remember: carbonation, oxidation, hydration and solution are the main chemical weathering processes.

Source: NCERT Class XI Fundamentals of Physical Geography, Geomorphic Processes (Weathering)

Row 1 is wrong. The Vosges lie in Europe (France), not Central Asia. They are block mountains.
Row 2 is wrong. The Alps are young fold mountains.
Row 3 is correct. The Appalachians are old fold mountains in North America.
Row 4 is correct. The Andes are young fold mountains in South America.
So only two rows are correct.
Remember: Vosges and Black Forest are classic block mountains on the Rhine rift valley.

Source: NCERT Class XI Fundamentals of Physical Geography, Geomorphic Processes; Landforms (mountains)

Statement 1 is correct. P waves travel faster, so they reach a seismograph first.
Statement 2 is correct. P waves are longitudinal, so particles move back and forth along the direction of travel.
S waves are transverse, so particles move at right angles to the direction of travel.
Remember: P means primary and S means secondary.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 3

The Rann of Kutch was once a shallow arm of the Arabian Sea. Repeated falls in sea level and tectonic uplift cut it off from the sea.
The region became a vast seasonal salt marsh.
Bhitarkanika mangroves grow in a river delta. Marakkanam salt pans are man-made. Naupada swamp is a coastal wetland formed by a different process.
Remember: The Rann of Kutch floods in monsoon and dries into a salt desert.

Source: Geological Survey of India / Standard Geography reference on Kutch

Statement 1 is correct. Barren Island in the Andaman Sea is India's only active volcano.
Statement 2 is incorrect. It lies about 140 km north-east of Port Blair in the Andaman Islands, not near Great Nicobar.
Statement 3 is incorrect. It has erupted several times since 1991, including in the 2000s and 2010s.
So only statement 1 is correct.
Remember: Barren Island is the only active volcano in South Asia.

Source: Geological Survey of India / Standard Geography reference

All four features show that the Himalayas are young fold mountains.
Deep gorges show that rivers are still cutting down rapidly. U-turn river courses show that rivers are adjusting to rising mountains. Parallel ranges result from the folding of sediments.
Steep gradients cause landslides because slopes have not yet been smoothed by erosion.
Old fold mountains, like the Aravallis, have low heights and rounded peaks.
Remember: the Himalayas formed from the collision of the Indian and Eurasian plates.

Source: NCERT Class XI, India: Physical Environment, Ch. 2

Statement 1 is correct. The Himalayas block the cold, dry winds from Central Asia and Siberia.
Statement 2 is correct. Rivers from the Himalayas carry silt and deposit it on the plains. Without the mountains, the extensive alluvium would not form.
Statement 3 is correct. The Himalayas stop the monsoon winds and force them to give rain over the plains. They also shape the summer low pressure over north India.
Remember: the Himalayas act as both a climatic and a drainage divide.

Source: NCERT Class XI, India: Physical Environment, Ch. 2 and 4

The core lies below the mantle and is made mainly of iron with some nickel.
This is why it is called the Nife layer.
Aluminium and silicon are major elements of the crust, and chromium is only a trace element.
Remember: The outer core is liquid and the inner core is solid.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 3

Mount St Helens is an active volcano in Washington state, USA.
It is part of the Cascade Range.
It erupted violently in May 1980.
Chile, Japan and the Philippines have other volcanoes but not this one.
Remember: Cascade volcanoes include Rainier, Hood and St Helens.

Source: USGS volcano records; standard atlas

Statement 1 is correct. They form at the surface by deposition of sediments, mostly carried by water.
Statement 2 is correct. Sediments come from weathering and erosion of older rocks.
Statement 3 is correct. Fossils are preserved in them because of gentle burial.
Statement 4 is correct. Deposition in successive layers gives stratification.
Remember: Fossils are found only in sedimentary rocks, not in igneous rocks.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 5

Mount Rainier is in Washington state, USA (4).
Etna is in Sicily, Italy (1).
Paricutin is in Michoacán, Mexico (2).
Taal is in Luzon, Philippines (3).
The correct code is 4, 1, 2, 3.
Remember: Paricutin appeared in a farmer's field in 1943.

Source: Standard world atlas

The Deccan Traps formed by lava flows in the late Cretaceous to early Eocene period.
The Western Ghats are taken here as shaped in the Late Cenozoic, by faulting and uplift on the western edge.
The Aravalli is among the oldest ranges and is Pre-Cambrian.
The Narmada-Tapti alluvial deposits are recent, from the Pleistocene.
So the match is A-3, B-1, C-2, D-5.
Remember: the Aravalli is the oldest fold mountain range of India.

Source: NCERT Class XI, Fundamentals of Physical Geography; India: Physical Environment, Ch. 2

Statement 1 is correct. The sinkhole is the commonest surface form in karst terrain.
Statement 2 is correct. A sinkhole is a depression, from under a metre to hundreds of metres deep.
Statement 2 only describes the size of a sinkhole. It does not explain why sinkholes are the commonest form.
So both are true but II does not explain I.
Remember: Sinkholes form by solution of limestone or by collapse.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 7 'Landforms and their Evolution' (karst)

Chemical weathering includes oxidation, so A matches 2.
Mechanical weathering includes the wedging action of plant roots, so B matches 3.
Glacial deposits are called till, so C matches 1.
Stalactites form by deposition from ground water, so D matches 4.
The code is 2 3 1 4.
Remember: Till is unsorted glacial deposit.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 6 'Geomorphic Processes'

Statement 1 is incorrect. The theory of plate tectonics was put forward in 1967 by McKenzie, Parker and Morgan. H.H. Hess gave the sea floor spreading hypothesis in the early 1960s.
Statement 2 is correct. Plate tectonics is built on the sea floor spreading idea, along with continental drift.
Remember: Wegener - continental drift (1912); Hess - sea floor spreading (1961-62).

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 4 'Distribution of Oceans and Continents'

Statement 1 is correct. The shadow zone depends on the position of the epicentre, so it differs from one earthquake to another.
Statement 2 is incorrect. Beyond 105 degrees, S-waves are not recorded at all. P-waves are also missing between about 105 and 145 degrees. So both waves are not recorded at every distance beyond 105 degrees.
Remember: S-wave shadow zone is wider than the P-wave shadow zone.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 3 'Interior of the Earth'

Loess is fine dust deposited by wind. So A matches 1.
A tombolo is a bar of sand joining an island to the mainland. It is deposited by the sea. So B matches 4.
Point bars are deposits on the inner bank of river meanders. So C matches 3.
Moraines are debris left by glaciers. So D matches 2.

Source: NCERT Class XI, Fundamentals of Physical Geography, Ch. 7 (Landforms and their Evolution)