Landforms — Set 1

Correct Answer: D. Moraine

• **Moraine** = a depositional landform consisting of dirt and rocks pushed along or carried by a glacier, classified specifically as depositional rather than erosional. • **Lateral and Terminal moraines** — the two main types; lateral moraines form along the sides of a glacier while terminal moraines mark its furthest advance. • 💡 Wrong-option analysis: Cirque: an erosional bowl-shaped hollow carved by glacier at the valley head; Yardang: a wind-eroded ridge in deserts, not glacial; Barkhan: a crescent-shaped sand dune formed by wind, not glacial deposition.

Correct Answer: B. Canyon

• **Canyon** = a deep cleft between escarpments or cliffs formed by the erosive activity of a river over geologic timescales, exposing multiple rock layers. • **1.6 km deep** — the depth of the Grand Canyon in Arizona, carved by the Colorado River over about 5-6 million years. • 💡 Wrong-option analysis: Plateau: a flat-topped elevated landform, not a valley carved by a river; Archipelago: a group or chain of islands, not a river valley feature; Isthmus: a narrow strip of land connecting two larger land masses.

Correct Answer: D. Wind

• **Wind** = mushroom rocks (rock pedestals) are formed when wind-driven sand erodes the base of a rock more than the top, leaving a narrow base and wide top resembling a mushroom. • **Sand grains carried 1-2 metres high** — the typical height at which wind-driven sand is most concentrated, explaining why erosion is strongest at the base. • 💡 Wrong-option analysis: Underground water: creates karst features like stalactites and sinkholes, not mushroom rocks; Running water: forms V-shaped valleys, gorges, and waterfalls; Ocean waves: form sea cliffs, arches, and sea stacks along coastlines.

Correct Answer: A. Weathering

• **Weathering** = an exogenic process originating outside Earth's crust that acts on the surface, breaking down rocks through chemical or physical means. • **2 types** — chemical weathering (dissolves minerals) and physical/mechanical weathering (breaks rocks without chemical change), both driven by external energy. • 💡 Wrong-option analysis: Diastrophism: internal tectonic forces that fold and fault the crust, an endogenic process; Earthquake: caused by internal energy release at faults or plate boundaries; Volcanism: driven by internal magmatic activity, an endogenic force.

Correct Answer: B. Glaciers

• **Glaciers** = carve U-shaped valleys by widening and deepening existing V-shaped river valleys as they move slowly, creating flat bottoms and steep sides. • **Fjords** — U-shaped glacial valleys that became partially submerged by the sea after glaciers retreated and sea levels rose; Norway has over 1,000 fjords. • 💡 Wrong-option analysis: Rivers: carve V-shaped valleys through vertical downcutting; Wind: creates yardangs, dunes, and mushroom rocks; Sea waves: form cliffs, sea arches, and beaches along coastlines.

Correct Answer: A. Barkhan

• **Barkhan** = a crescent-shaped sand dune with tips or 'horns' pointing downwind, formed in areas with constant wind direction and limited sand supply. • **Up to 30 metres tall** — the typical height of barkhans, which can migrate across desert surfaces at up to 100 metres per year. • 💡 Wrong-option analysis: Inselberg: an isolated resistant hill rising from a flat plain in arid regions, not a dune; Stalagmite: a mineral formation growing upward from cave floors due to dripping water; Loess: fine wind-blown silt deposited in sheets, not a crescent-shaped dune.

Correct Answer: B. Sinkhole

• **Sinkhole** = formed when the roof of an underground limestone cavern collapses, creating a surface depression through which water drains; also called doline or swallow hole. • **Florida, USA** — one of the world's most sinkhole-prone regions, with the state reporting thousands of sinkholes due to its thick limestone bedrock. • 💡 Wrong-option analysis: Uvala: a larger depression formed by the merging of multiple sinkholes, not a single cave ceiling collapse; Lapies: grooved or furrowed rock surface formed by dissolution, not collapse; Blind valley: a valley where a stream disappears underground, not formed by ceiling collapse.

Correct Answer: A. Delta

• **Delta** = a fan-shaped accumulation of silt and sand formed at a river's mouth when it slows on entering a sea or lake and loses its sediment-carrying capacity. • **Sundarbans** — the world's largest delta, formed by the Ganges-Brahmaputra-Meghna system in India and Bangladesh, covering about 10,000 km². • 💡 Wrong-option analysis: Ox-bow lake: forms when a meander loop is cut off from the main channel; Meander: a winding loop formed by lateral erosion in the middle course; Waterfall: forms where a river flows over a resistant rock ledge, an erosional not depositional feature.

Correct Answer: B. Fluvial deposition

• **Fluvial deposition** = natural levees are elongated ridges of mud and silt deposited along river banks during flooding when overflowing water loses its energy and drops its sediment. • **Mississippi River levees** — some of the world's most studied natural levees, which have been artificially raised to over 9 metres to prevent flooding. • 💡 Wrong-option analysis: Coastal retreat: causes sea cliffs and wave-cut platforms, not river levees; Glacial abrasion: creates smooth U-shaped valleys and polished rock surfaces; Aeolian erosion: wind-driven process creating yardangs and ventifacts in deserts.

Correct Answer: C. Cliff

• **Cliff** = formed by continuous wave erosion undercutting the base of coastal rock, leading to collapse of the overhanging rock and retreat of the coastline. • **White Cliffs of Dover** — one of England's most iconic sea cliffs, up to 107 metres tall, formed by wave erosion of chalk rock. • 💡 Wrong-option analysis: Barrier island: a depositional landform of sand parallel to the coast; Spit: a depositional feature formed by longshore drift extending into the sea; Beach: a depositional landform formed by wave deposition of sand and pebbles.