Mass movements, erosion, and deposition

Gravity pulls material down a slope in mass movements. For exams remember slope and gravity together.

Soil creep is very slow and becomes visible over a long time. In exams connect it with slow mass movement.

Heavy rainfall saturates slope material and makes it unstable. For exams treat rainfall and steep slopes as key causes of landslides.

Erosion is the removal of soil and rock from a river’s bed and banks by flowing water. Deposition means laying down the material carried by the river, so it is not the process of cutting. Exam tip: choose erosion for cutting or removal, and deposition for the accumulation of sediment.

When river velocity decreases its carrying capacity reduces and deposition occurs. For exams link low energy with deposition.

In rock fall rock fragments drop rapidly downslope. In exams sudden falling indicates rock fall.

Direct answer: D, rapid flow of water and loose debris. A debris flow is a very fast mass movement in which abundant water mixes with soil, stones, and other loose material and moves downslope like a thick muddy stream. Reasoning: heavy rain or sudden melting supplies water; loose slope material becomes saturated; the mixture loses stability; gravity drives it rapidly downhill. Option A, flying only in air, describes neither the usual material nor its water-rich flow. Option B, freezing only as ice, describes freezing or glacial conditions, not debris flow. Option C, remaining stable without water, is the opposite of the process: debris flow requires movement and commonly involves water. Option D is correct because it states both the water and the loose debris and emphasizes rapid movement. It is different from a dry rockfall, although both are mass movements. Memory cue: water + loose debris + steep slope + speed = debris flow.

On steep slopes the downslope effect of gravity becomes stronger. For exams connect steeper slopes with higher instability.

Gravity is the key force in mass movement while flowing water dominates river erosion. In exams identify the driving agent.

The outer bank of a bend has higher water energy and velocity. For exams remember outer bank erosion and inner bank deposition.

Lower velocity on the inner bank causes sediment deposition. In exams treat low velocity as the cause of deposition.

A glacier erodes by grinding and scratching rocks. For exams link glacial abrasion with erosion.

The direct answer is A: cutting of coastal rocks by sea waves is marine erosion. Erosion means wearing away and removing material. When waves repeatedly strike a rocky coast, their force, water pressure, and carried sand can break and remove pieces of the shore. Step by step: waves approach the coast; water and sediment hit cracks in the rock; pressure and abrasion enlarge the cracks; fragments are detached and carried away; the shoreline may retreat. Option A is correct because the agent is the sea and the action is cutting, so the process is marine erosion. Option B, terrestrial deposition, means land-based material being laid down, not coastal rock being cut. Option C, biological weathering, involves living organisms weakening or breaking rock and is not the process named here. Option D, soil formation, is the development of soil from rock, organic matter, and other materials, not the removal of coastal rock by waves. Exam cue: waves cutting a coast means marine erosion; waves depositing sand may form beaches.

Wind erodes by removing sand and deposits it by laying sand down. For exams note that one agent can perform both processes.

Sand dunes form when wind deposits sand. For exams treat dunes as a key example of wind deposition.

Soil creep slowly shifts surface material and can tilt trees and poles. In exams tilted poles are a clue for soil creep.

When carrying capacity decreases the river cannot transport sediment further and deposits it. For exams connect reduced capacity with deposition.

In mass movement material moves downslope due to gravity. In exams notice the absence of a definite river channel.

Vegetation roots bind soil particles and improve the soil’s grip on a slope. This reduces erosion and the likelihood of soil slipping, so afforestation is useful in landslide-prone areas. Unlike option C, vegetation generally slows surface runoff rather than increasing it. Exam tip: link slope stability with root binding of soil.

The upper course has a steep gradient which gives the river strong erosive power. For exams link upper course with deep valleys.

During floods rivers spread and deposit fine sediments to form flood plains. For exams connect flood plains with river deposition.

Steep slopes and sparse vegetation make the surface more exposed. For exams link bare steep slopes with higher erosion.

The direct answer is A: transport carries removed material to another place. Erosion is more than simply breaking or cutting a surface. In school geography, erosion usually involves the wearing away and removal of soil or rock by running water, wind, ice, waves, or gravity. Transport is important because the loosened material must be moved away from its original position. The step-by-step chain is: weathering loosens material, erosion removes it, transportation carries it, and deposition drops it when energy decreases. Option A is correct because it states this carrying function. Option B is wrong because keeping material in place is not transport; it is the opposite of movement. Option C is wrong because temperature reduction is not the defining work of transport. Option D is wrong because rocks do not become organisms through erosion or transport. Therefore A gives the exact reason transport matters in erosion. Remember: removal without movement is not complete transport; transport means carrying.

Water saturation can make loose material heavier and less stable. For exams connect saturation with landslide risk.

A river loses velocity when entering a sea or lake and deposits sediment. For exams remember mouth and deposition together.