CBSE Class 9 Social Science Chapter 02 Shaping Of The Earths Surface MCQs Set 01

Answer: (A) W.J. Morgan

Explanation:
The chapter credits W.J. Morgan with formulating plate tectonics, the theory describing how the Earth's crust is broken into moving plates.

Answer: (A) A semi-molten layer beneath the lithosphere that allows plates to slide

Explanation:
Sitting just below the rigid lithosphere, the asthenosphere is partly molten, which is precisely what lets tectonic plates glide over it rather than staying locked in place.

Answer: (A) Oceanic plates are denser and thinner than continental plates

Explanation:
The chapter notes oceanic crust is only about 5-7 km thick compared to 30-40 km for continents, and when the two collide, the denser oceanic plate is forced downward, triggering volcanic activity and earthquakes.

Answer: (C) Transform boundary

Explanation:
Plates sliding past one another without creating or destroying crust describes a transform boundary, and the chapter uses the San Andreas Fault as its real-world example, noting it mainly produces earthquakes.

Answer: (A) Upper course - V-shaped valley; middle course - meander; lower course - delta

Explanation:
Steep gradients near the source carve V-shaped valleys and waterfalls, the middle stretch loses energy and starts meandering, while the lower course deposits sediment to build deltas.

Answer: (A) Weathering only breaks rock down in place, while erosion also transports the broken material

Explanation:
Weathering simply fragments rock without moving it anywhere, whereas erosion picks up that loosened material and carries it elsewhere via agents like water, wind, or ice.

Answer: (C) Biological weathering

Explanation:
This falls under biological weathering, since living organisms such as plant roots are directly responsible for breaking the rock.

Answer: (A) Vayu, Agni, Indra, and Varuna

Explanation:
He connected quakes to wind, fire, thunder, and water, each tied to particular constellations and regions, blending early observation with cosmological thought.

Answer: (B) The Ring of Fire

Explanation:
Because plate boundaries cluster heavily around the Pacific, this zone experiences frequent seismic and volcanic activity and is popularly termed the Ring of Fire.

Answer: (B) Till, made up of rocks, soil, and debris

Explanation:
As glaciers melt, they drop the till they had been carrying and scraping along; this deposited material builds lateral, terminal, or medial moraines depending on where it collects.

Answer: (B) Rapid glacier melting, excess rainfall, or an earthquake weakening the natural dam

Explanation:
• Warming temperatures swell glacial lakes and strain their ice or moraine dams
• Extra rain or snowfall adds further pressure
• Earthquakes, avalanches, or landslides can crack the dam, releasing stored water suddenly downstream

Answer: (A) Baratang Island in the Andaman and Nicobar Islands

Explanation:
Unlike typical fiery volcanoes, the Baratang mud volcano simply bubbles mud due to trapped gases pushing upward, making it a distinctive natural feature described in the chapter.

Answer: (A) They receive rich alluvial soil deposited by the river at its mouth

Explanation:
As a river slows near its mouth, it drops the fertile sediment it has carried from upstream, building up nutrient-rich soil that favours crops such as rice and jute even though flooding remains a risk.

Answer: (D) Barchan dune

Explanation:
The chapter describes barchan dunes specifically as crescent-shaped, arising under conditions of limited sand and a consistent wind direction, unlike the multi-armed star dune or wind-parallel longitudinal ridges.

Answer: (B) Both used techniques like bunding, terracing, or earthen embankments to conserve soil and water

Explanation:
The Sindhu-Sarasvati civilisation practised contouring, bunding, terracing, and canal systems, while Nagaland's Zabo system used earthen bunds and check dams on hillslopes; both aimed at slowing runoff, curbing erosion, and boosting groundwater recharge.

Answer: (B) Mixed plate

Explanation:
The chapter divides tectonic plates into three kinds based on what they carry: continental plates carry only continents, oceanic plates carry only ocean floors, and mixed plates carry a combination of both.

Answer: (C) Divergent boundary

Explanation:
At a divergent boundary plates pull apart, letting magma rise and solidify into new crust, and the Mid-Atlantic Ridge is the textbook's example of this process forming a mid-ocean ridge.

Answer: (B) Convection currents in the mantle caused by heat from the core

Explanation:
• Heat rising from the core warms mantle material, causing it to rise.
• Cooler material sinks back down.
• This rising-and-sinking cycle sets up convection currents that push and pull the plates above, making them drift slowly.

Answer: (B) A natural feature on Earth's surface shaped by processes like weathering, erosion, deposition, and crustal movement

Explanation:
Landforms are described as natural surface features—mountains, valleys, plateaus, plains, deserts, and coasts among them—produced by ongoing shaping processes rather than by human construction or political boundaries.

Answer: (B) They acted as a barrier against invasion while still allowing cultural exchange through mountain passes

Explanation:
The mountains shielded India from many invasions, yet passes such as the Khyber Pass still permitted movement of people and ideas, showing that a single landform can both restrict and enable human contact.

Answer: (C) It limited large settlements but still encouraged trade routes like the Silk Route

Explanation:
Deserts are harsh for permanent settlement, yet the chapter notes that the Thar still fostered long-distance trade, showing that even a limiting landform can shape economic connections rather than only blocking them.

Answer: (B) Because a layer of hard rock resists erosion while the softer rock beneath it wears away, creating a sudden drop

Explanation:
Differential erosion is the key idea here: the tougher rock layer stays in place longer than the weaker rock underneath, so the river ends up dropping suddenly over a ledge once the soft rock is worn away.

Answer: (B) An isolated pillar of rock called a stack is left standing

Explanation:
The chapter traces a sequence—caves form on either side of a headland, they join to make an arch, and when that arch eventually collapses, what remains standing separately is called a stack.

Answer: (B) Stalactites hang down from the cave ceiling while stalagmites rise up from the cave floor

Explanation:
Both are formed by dissolved minerals deposited from dripping water, but their position differs—one grows downward from above, the other builds upward from below, and over time the two can even join to form a pillar.

Answer: (B) Deforestation, mining, road construction, and unplanned building on hillsides

Explanation:
Beyond natural triggers like rainfall and seismic shaking, the chapter points out that clearing forests, digging mines, cutting roads, and constructing buildings on slopes disturb the natural stability of hillsides, making them more prone to sudden failure.