Erosional and depositional landforms created by various agents

Direct answer: A, sea cliff. A sea cliff is a steep or nearly vertical coastal rock face produced mainly by wave erosion. The process can be understood step by step. Waves strike the foot of the coast, hydraulic pressure pushes water into cracks, and sand or pebbles carried by the waves scrape the rock. A wave-cut notch develops at the base. Continued undercutting makes the upper rock unstable; it collapses, and the shoreline retreats, leaving a steep cliff. A is correct because it describes this wave-eroded coastal feature. B is wrong because a drumlin is a streamlined hill shaped by glacial ice. C is wrong because a sand dune is a ridge or mound formed mainly by wind deposition. D is wrong because a floodplain is a relatively flat depositional surface beside a river, built from flood sediments. A useful warning is that a sea cliff is an erosional feature, whereas a floodplain and many dunes are depositional features.

The correct answer is Wave-cut platform. Waves erode the base of a sea cliff, and repeated cliff collapse causes the coastline to retreat. The former shore floor is gradually widened into a gently sloping, rocky platform exposed near the coast, called a wave-cut platform or shore platform. An alluvial fan and natural levee are river depositional features, whereas a cirque is a glacial erosional hollow, so none is formed by retreating sea cliffs.

Direct answer: A, sea arch. The formation can be followed in stages. Waves first enlarge cracks or a cave in a coastal headland. Continued erosion attacks the rock from the cave toward the opposite side. When the cave breaks through completely, there is an opening on both sides, while stronger rock remains above it as a curved roof. This through-opening is called a sea arch. A is correct because a sea arch is specifically a coastal erosional feature formed when a cave becomes open from one side to the other. B is wrong because a delta is sediment deposited where a river enters a sea or lake. C is wrong because a U-shaped valley is mainly carved by moving glacial ice. D is wrong because loess is fine dust and silt deposited by wind. Continued wave erosion may weaken the arch roof, causing collapse and leaving a sea stack, but the through-opening itself is the arch. Remember the sequence: cave, arch, stack.

A beach is a coastal depositional landform created when waves and longshore currents lose energy and leave behind sand, pebbles, and other sediments along the shore. Therefore, option A is correct. A gorge and a cirque are mainly erosional landforms associated with rivers and glaciers, while a yardang is carved by wind erosion in arid regions.

A spit is a narrow, elongated ridge of sand or shingle that projects from the coast into the sea. It usually develops through longshore drift, which transports sediment along the shoreline and deposits it where the coastline changes direction or the current loses energy. Thus, option A is correct; a cirque and drumlin are glacial features, while a pothole is formed by river erosion.

A sinkhole is a circular, funnel-shaped, or sometimes irregular depression formed when groundwater dissolves soluble limestone and removes material underground. It is a characteristic karst landform, so option A is correct. A delta forms where a river deposits sediment, a sand dune is built by wind deposition, and a sea stack is an isolated coastal rock left by marine erosion.

The governing process is chemical solution, in which slightly acidic groundwater dissolves soluble limestone along cracks and joints. Over time, this action enlarges underground passages and can produce caves, sinkholes and other karst features. Therefore, option A is correct. Deflation is wind removal, abrasion is scraping, and freezing involves ice rather than limestone dissolution.

Wind is the governing geomorphic agent for both features. A barchan is a crescent-shaped sand dune formed when persistent wind moves and deposits sand, usually where sand supply is limited. Loess is a blanket-like deposit of fine, wind-blown silt. Therefore option A is correct; glaciers, sea waves and groundwater produce different landforms.

Glaciers create both features through different actions. A cirque is a bowl-shaped hollow carved by glacial erosion near the head of a valley, whereas a moraine is an accumulation of unsorted rock debris deposited by moving or melting ice. Hence option A is correct. Rivers, wind and groundwater can erode landscapes, but they do not form this characteristic pair.

Sea waves are the governing coastal agent. Repeated hydraulic pressure and abrasion attack weaknesses in a sea cliff, enlarging cracks into caves. Continued erosion can cut through a headland to form an arch; when the arch collapses, an isolated sea stack remains. Thus option A is correct, while rivers, glaciers and wind do not normally create this connected coastal sequence.

Groundwater forms karst features mainly through solution of soluble limestone. Rainwater absorbs carbon dioxide from the soil and becomes weakly acidic; as it moves underground, it dissolves limestone along joints and bedding planes. Enlarged openings may collapse into sinkholes, while connected passages become caves. Therefore option A is correct; waves, glaciers and wind use different processes.

A meander is the characteristic feature of a river’s middle and lower course. On a relatively gentle slope, the fastest flow erodes the outer bank while slower water deposits sediment on the inner bank, causing the channel to bend laterally. Therefore option A is correct. Cirques are glacial, barchans are wind-made, and sea arches are coastal features.

A tombolo is a coastal depositional ridge, usually made of sand or shingle, that links an island to the mainland or to another island. Waves and longshore currents lose energy in the sheltered zone behind the island and deposit sediment there. Thus option B is correct. A lagoon is a water body, a sea cave is erosional, and a cirque is glacial.

The governing concept is river erosion. Abrasion, also called corrasion, occurs when rock fragments carried by flowing water scrape, rub and strike the river bed and banks, gradually wearing them away. Therefore, option A is correct. Deposition means sediment is laid down, while evaporation and condensation are changes involving water vapour, not processes that cut solid rock.

The governing concept is differential erosion. Softer rock is worn away faster than resistant hard rock, creating a sudden break in the river bed; water then plunges over the step and a waterfall develops. Therefore, option A is correct. A barchan is a wind-shaped dune, a moraine is deposited by a glacier, and a spit is a coastal depositional feature, so none fits the river process.

The governing concept is river deposition on a floodplain. During repeated floods, a river spreads beyond its channel and loses carrying power, so fine alluvial silt settles across the adjacent low-lying surface. This produces a broad, level and often fertile floodplain, making option B correct. A cirque is glacial, a sea stack is coastal, and a yardang is carved by wind erosion.

The governing concept is deposition at the river mouth. As a river enters a lake or sea, its gradient and velocity usually decrease, reducing its ability to carry sand, silt and clay. These sediments accumulate near the mouth and may build a delta, so option C is correct. A sea cave is cut by waves, a mushroom rock by wind abrasion, and an arete is a sharp glacial ridge.

Direct answer: A, an alluvial fan. A mountain stream usually flows quickly down a narrow, steep valley and can carry gravel, sand and silt. When it emerges onto a flatter plain, the gradient and speed decrease. Its carrying capacity falls, so it deposits some of its load. The sediment spreads outward from the narrow valley mouth in a broad, fan-like shape, called an alluvial fan. B is a sea arch made by coastal wave erosion. C is a depression formed by dissolution or collapse in soluble rock. D is a sharp glacial peak formed by erosion around a mountain. Therefore only A matches a river leaving mountains and losing slope. Memory cue: steep valley to flat plain means the river drops its load in a fan.

Direct answer: B, seif dune. A dune forms when wind transports sand and deposits it after losing energy. A seif dune is a long, narrow, linear sand ridge that generally extends parallel to the prevailing or resultant wind direction. The word “parallel” is the decisive clue. B is correct because it names this elongated wind-built dune. A is wrong because a delta is a depositional landform made mainly by river sediments at a river mouth, not by wind. C is wrong because a cave is a hollow space in rock or underground material, not a sand ridge. D is wrong because a beach is a strip of sediment along a shore, shaped by waves, tides, and currents; it is not specifically a long dune parallel to wind. A helpful memory cue is to imagine a seif dune as a long sword of sand pointing with the wind. Do not confuse wind direction with dune height: the defining clue here is the elongated, roughly parallel alignment.

The correct answer is C, loess. Loess is a blanket-like deposit of very fine silt and dust transported and spread by wind, often over a large area. Because it may contain mineral particles and can develop deep, porous soils, loess regions are often agriculturally productive, although actual fertility also depends on moisture, climate, and soil management. A, an alluvial fan, forms when running water spreads sediment at the foot of a slope. B, an esker, is a winding ridge deposited by meltwater streams associated with glacial ice. D, a sea cave, is an erosional opening made by waves in a coastal cliff. Memory cue: “loess” sounds like loose dust, so connect it with wind-blown fine sediment.

The direct answer is B: sea cave. A coastal cliff may contain a crack, joint, or band of weaker rock. Waves repeatedly strike this weak line, forcing water and sediment into it. Water pressure helps widen the opening, while sand and pebbles carried by the waves scrape the rock through abrasion. As the opening becomes larger, a hollow space develops in the cliff; this is a sea cave. With continued erosion, the cave may enlarge through a headland and form a sea arch. If the arch later collapses, a sea stack and eventually a stump may remain. A, a delta, forms when a river deposits sediment near its mouth, not when waves erode a cliff. C, loess is fine wind-deposited sediment. D, a sinkhole generally forms when underground material dissolves or the ground collapses into a cavity. Therefore B is the only option produced first by the stated wave-erosion process. Memory cue: coastal erosion sequence—cave, arch, stack, stump.

The direct answer is C: sea arch. Coastal erosion often begins where waves attack a crack or weak zone in a headland. Continued hydraulic action and abrasion enlarge the crack into a sea cave. If erosion continues through the rock, the cave opens at both sides of the headland. The remaining rock above the opening forms a natural bridge called a sea arch. A, a beach, is a deposit of sand, gravel, or other sediment along the shore; it is not a hollow passage cut through a headland. B, a natural levee, is a raised bank beside a river channel, formed mainly by sediment deposited during floods. D, a barchan is a crescent-shaped sand dune produced by wind in an area with limited sand and a fairly consistent wind direction. Only C describes the next stage after a cave is cut through. If the roof of the arch later collapses, an isolated sea stack may remain. Memory cue: cave first, arch after breakthrough, stack after collapse.

The correct answer is D, a sea stack. Coastal erosion often follows a recognizable sequence. Waves enlarge a weakness into a sea cave. Continued erosion may cut the cave through the headland, producing a sea arch. Wave attack weakens the arch roof until it collapses, leaving an isolated, steep-sided pillar of rock near the coast. That pillar is called a sea stack. A, a sinkhole, is a surface depression caused mainly by underground dissolution or collapse. B, a drumlin, is a streamlined hill associated with glacial deposition or ice movement. C, an oxbow lake forms when a river cuts through the narrow neck of a meander. These three are therefore unrelated to the described marine sequence. Memory cue: cave, arch, stack, stump.

The governing concept is wave erosion at a rocky coast. Repeated wave attack cuts a notch at the foot of a sea cliff, and as the cliff retreats, the former shore floor is exposed as a broad, gently sloping rock surface. This is a wave-cut platform. A moraine is deposited by ice, a sand dune by wind, and an alluvial fan by streams at mountain fronts; therefore option A is correct.

The correct answer is B, a beach. A beach is an accumulation of loose material such as sand, gravel, pebbles, shells, or other sediment along the shore. Waves move this material and may deposit it when their energy decreases, while longshore currents can redistribute it along the coast. A, a cirque, is a bowl-shaped hollow carved by glacial erosion near the head of a mountain valley. C, a gorge, is a deep and narrow valley, commonly formed by river erosion. D, a drumlin, is a streamlined glacial hill made or reshaped beneath moving ice. Thus the description of wave-deposited coastal sediment identifies a beach. Memory cue: beach means material “brought and laid” along the shore.