Mass movements, erosion, and deposition

Direct answer: B, broken particles and deposited material. Sediment means loose material that has been produced by weathering or erosion and may later be transported and deposited. Rocks can break into pebbles, sand, silt, or clay; soil can also be carried by water, wind, ice, or gravity. Step by step: first a rock or soil mass is broken or loosened; next the particles may move; finally they may settle in a new place. Option A, moisture in air, is water vapour and is not sediment. Option B is correct because broken rock and soil particles, especially when accumulated, are called sediment. Option C, sunlight, is energy, not a solid or loose earth material. Option D, Earth’s axis, is an imaginary line around which Earth rotates and has no connection with sediment. Remember: sediment is movable earth material; deposition is its settling.

At the mouth river energy decreases and sediments settle. Exam tip: connect delta with fluvial deposition.

Running water can remove fertile soil and reduce land productivity. Exam tip: connect water erosion with farming.

A steep slope increases the effect of gravity and helps material move down. Exam tip: link slope steepness with risk.

Waves and coastal currents carry sediments such as sand and deposit them along the shore. Therefore, the accumulation of sand on a sea coast is coastal deposition. In coastal erosion, waves remove material from the coast rather than building it up. Exam tip: addition of sediment indicates deposition, while removal of material indicates erosion.

A river can deepen its valley by eroding the bed and the lower parts of its channel. This process is called river erosion, and in the upper course it is especially associated with vertical or downward cutting. As the river removes rock and sediment from the channel floor, the valley becomes deeper and often develops a narrow V-shaped form in suitable mountainous areas.

The question asks about deepening, not the spreading of deposited material. Wind deposition and marine deposition add sediment rather than cut a river valley, and biological respiration is unrelated to this landform process. Although rivers also erode sideways and deposit sediments in other parts of their course, the main process responsible for valley deepening is downward river erosion. Therefore option A is correct.

Slope material moves downward when gravity overcomes the forces holding it in place. Loose rocks already have weak contact and little cohesion. When water fills the spaces between soil particles, the material becomes saturated. Water can increase its weight, reduce friction, and weaken the connection between particles. These changes make landslides or other mass movements more likely, especially on a steep slope.

A stable, dry slope usually has stronger resistance to movement. Flat land has little slope for material to descend, and the statement that there is no gravity removes the force that causes ordinary downslope movement. Therefore, the condition in option B—loose and water-saturated rocks—best explains why slope material can slide easily.

After erosion material may be carried by water wind or ice. Exam tip: understand the sequence erosion transportation deposition.

Lateral erosion helps a river become wider. Exam tip: connect bank cutting with lateral erosion.

Slow creep can gradually tilt trees and poles. Exam tip: remember visible signs of slow movement.

Road construction and deforestation can weaken slope stability. Exam tip: treat human interference as a risk factor.

At low speed wind cannot carry sand further and deposition occurs. Exam tip: connect low energy with deposition.

Erosion is the process by which soil, rock, or other surface material is worn away and carried from one place to another. Running water is one of the most important agents of erosion. A river can cut into its bed and banks, especially when the water flows quickly or carries sand and stones. Over a long period, this cutting can deepen valleys, widen channels, and change the shape of the land. Thus, a river and cutting are correctly connected with erosion.

Choice A is the only meaningful and correct pair. The Moon and farming do not form an erosion pair, and a star and soil have no such geomorphic relationship. Clouds may bring rain, but “rock birth” is not an erosion process, so choice D is also incorrect. The key idea is that erosion involves wearing away and removal, and flowing river water is a major agent that performs this work.

A delta forms from accumulation of river sediments. Exam tip: treat delta as a depositional landform.

Weathering breaks rock and erosion removes broken material. Exam tip: remember the difference between the two processes.

In mass movement, gravity pulls rock, soil, and debris down the slope. Therefore, the overall movement of material is downslope. Movement up the slope would be against the effect of gravity. Exam tip: remember that gravity is the main driving force of mass movement.

In rill erosion water cuts soil in small channels. Exam tip: connect small channels with rill erosion.

River sediments may contain fine and nutrient rich material. Exam tip: connect alluvial soil with river deposition.

A weak rock layer can become a surface along which stronger or heavier material above it moves. Water may enter the weak layer, reduce friction, or increase its weight and pressure, making sliding easier. If the layer is inclined in the same general direction as the slope, it can act as a plane of weakness and increase the chance of a landslide. The exact danger also depends on slope angle, rainfall, cracks, vegetation, and human activity.

Thus a weak layer does not remove gravity or always strengthen a slope. It can provide a slip surface, allowing the overlying mass to move downward under gravity. It may sometimes obstruct or redirect water, but that is not the main idea asked here. Therefore option A is correct because it directly links weak material with reduced stability and increased landslide risk.

Eroded material can be carried by agents and deposited elsewhere. Exam tip: treat erosion and deposition as linked stages.

During floods a river spreads and deposits fine sediments on plains. Exam tip: connect floodplains with river deposition.

Water can make slope material slippery and heavy. Exam tip: connect water with slope instability.

When energy decreases water wind or ice deposits material. Exam tip: link energy loss with deposition.

The direct answer is A: sea waves can wear away coastal rocks. This process is coastal erosion. Waves repeatedly strike cliffs and shore platforms, and the force of water, together with sand and pebbles carried by the waves, can scrape, hit, and weaken rock. Step by step: waves reach the coast; water pressure enters cracks; repeated impact enlarges cracks; loosened pieces are removed. Option A is correct because waves are a major coastal erosion agent. Option B, forest shade, may affect local temperature or moisture but does not directly cut coastal rock in the stated way. Option C, starlight, has no ordinary erosional force of this kind. Option D, underground metal, is not a standard external agent that wears away exposed coasts. Other agents, such as tides, wind, and weathering, may also contribute, but the best answer here is sea waves. Memory cue: wave attack makes a coast retreat.

Vegetation binds soil and drainage reduces saturation. Exam tip: remember both roots and drainage in prevention.