Mass movements, erosion, and deposition

When energy decreases the agent cannot carry sediment further. Exam tip: take energy loss as a sign of deposition.

Waves can erode coasts and also deposit material. Exam tip: remember both processes in coastal landforms.

Mass movement is the downslope movement, falling, sliding, or flowing of soil, rock fragments, or debris mainly under the force of gravity. Therefore, option A is correct. River erosion involves running water cutting and carrying material, whereas the question clearly excludes running water. Exam tip: landslides, rockfalls, and soil creep are examples of mass movement.

In transportation sediment moves further by river wind ice or waves. Exam tip: remember the order erosion transportation deposition.

Alluvium is fertile material brought and deposited by rivers. Exam tip: link it with river deposition.

Good drainage and roots stabilize slopes. Exam tip: remember drainage and vegetation in prevention.

At bends a river cuts its banks and widens its path. Exam tip: connect meanders with lateral erosion.

Heavier particles need more energy to carry so they deposit first. Exam tip: link particle size with order of deposition.

Cutting can disturb the natural balance of a slope. Exam tip: include human interference among landslide causes.

At its mouth a river may deposit sediment and form a delta. Exam tip: remember river mouth and deposition together.

In mass movement material shifts downward on a slope. Exam tip: also understand it as short-distance gravity movement.

The direct answer is A: sand accumulating along a coast is coastal deposition. Waves and longshore currents move sediment; where their energy decreases, they drop sand and build beaches, sand bars, or other coastal deposits. Step by step: weathering and erosion provide sediment; waves or currents transport it; slower water loses carrying power; sand settles and accumulates. Option A is correct because it names deposition at a coast. Option B is river vertical erosion, which means a river cuts downward into its bed; it is removal, not coastal accumulation. Option C, rockfall, is the sudden falling of rock from a steep slope. Option D, soil creep, is the very slow downslope movement of soil, usually on land. A beach is a useful visible example of deposition, although waves may also erode it under other conditions. Memory cue: a beach is where moving sediment is left behind.

Excess water can weaken slope material. Exam tip: remember water saturation as a cause of instability.

When flowing water cuts and removes material from the river bed, the process is river erosion. It deepens the river valley and is also called vertical erosion or downcutting. River deposition is the opposite process because it involves the settling of sediments. Exam tip: words such as “cutting” and “removal” indicate erosion, whereas “settling” indicates deposition.

The direct answer is A: dust and sand may be deposited when wind speed decreases. Wind can carry loose particles only when it has enough energy. Step by step: strong wind lifts or rolls dust and sand; the wind loses speed because of rough ground, obstacles, or a change in conditions; its carrying power becomes weaker; heavier sand settles first and finer dust may settle later. Thus deposition occurs. Option A is correct because slowing wind commonly causes wind-blown material to accumulate in dunes, sheets, or small deposits. Option B is wrong because particles do not always rise when wind becomes slow; rising generally needs upward movement and sufficient wind energy. Option C is wrong because dust and sand do not instantly become water; that would require a completely different physical process. Option D is wrong because particles do not disappear: they may simply move from the air to the ground. The exam clue is simple: strong wind transports, weak wind deposits.

Downslope movement of rock material is mass movement. Exam tip: place rock sliding under mass movement.

In erosion rock or soil is worn away from its original place. Exam tip: removal from original place is the key sign.

Loose rocks on high hills are dangerous because gravity can pull them down a steep slope. They may roll, bounce, or fall suddenly, especially when the supporting material is removed or weakened. Rainwater, freeze-thaw action, earthquakes, vibrations, and construction can loosen slope material further, but the basic reason remains the downward movement caused by gravity and the steep relief.

The question asks why loose rocks create danger, not what they become. They do not turn into light, stop rainfall, or make river water sweet. A loose block may fall by itself or join a rockfall, debris flow, or landslide, creating a hazard for people, roads, buildings, and river channels below. Therefore option A, that they can fall downward, is the correct and most direct explanation.

The direct answer is A: widening of a valley is linked with lateral erosion. A valley is the low area between higher lands, often containing a river. Erosion can work downward or sideways. Lateral means sideward, so lateral erosion removes material from the river banks. Step by step: water presses against the sides; bank material is loosened; flowing water carries it away; the banks retreat outward; the space between the sides increases and the valley becomes wider. Option A is correct because it directly describes this side-cutting process. Option B, dew formation, is the condensation of water vapour near the ground and does not cut valleys. Option C, a solar eclipse, is an alignment of the Sun, Moon, and Earth and is not an erosional process. Option D, thunder, is sound produced by rapidly heated and expanding air in a storm, not a process that widens a valley. Remember: vertical erosion makes a channel deeper, while lateral erosion generally makes a valley wider.

In transportation natural agents carry sediments forward. Exam tip: link agent energy with carrying capacity.

In rockfall, pieces of rock detach from a steep slope or cliff and fall rapidly and suddenly under gravity. Therefore, “Rapid and sudden” is correct. Soil creep is a very slow movement, while the downslope movement of water-saturated material is a different type of flow. Exam tip: remember rockfall as a rapid, sudden, gravity-driven mass movement.

Material is first eroded then carried and finally deposited. Exam tip: this sequence helps understand landform formation.

Soil creep is a very slow mass movement process. Exam tip: connect slow slope movement with soil creep.

When carrying capacity decreases the river starts depositing sediment. Exam tip: treat low energy as a sign of deposition.

Wind lifts and carries loose fine particles away. Exam tip: remember wind erosion in dry regions.