Mass movements, erosion, and deposition

Laying down particles is a direct sign of deposition. In exams identify deposition whenever material is laid down.

In gully erosion running water forms small deep channels. For exams link uncontrolled surface runoff with gully erosion.

Correct answer: A, a deep valley. Downward cutting is called vertical or downward erosion. A river removes material from its channel bed, making the valley deeper. Where this process is strong, especially in a youthful river or an area with steep relief, the valley may become narrow and deep, sometimes developing a V-shaped form. B is wrong because a sand dune is built mainly by wind deposition. C is wrong because a sea bar is a coastal depositional feature formed by marine sediments, not by a river cutting downward. D is wrong because a coral reef is made by coral organisms in suitable warm, shallow marine conditions. The key distinction is erosion downward versus deposition or marine growth. Memory cue: vertical erosion increases depth; lateral erosion increases width.

The direct answer is A: lateral erosion widens the river valley. The word lateral means sideward. In a river, lateral erosion mainly attacks the banks, especially where the current bends and strikes the outer bank. Step by step: flowing water hits the sides; soil and rock are loosened; the current removes the loosened material; the banks retreat outward; the distance between the valley sides increases. Option A is correct because it describes the normal effect of side-cutting. Option B is wrong because lateral erosion does not always close a valley; it generally makes the channel or valley broader. Option C is wrong because erosion of river banks does not, by itself, raise mountains. Option D is wrong because erosion cannot turn ordinary river water into ice; freezing requires suitable temperature conditions and is a different process. The helpful memory link is “lateral = side = width.” Do not confuse it with vertical erosion, which mainly deepens the channel.

Road cutting can reduce slope support and increase instability. For exams consider human interference as a risk factor.

Higher velocity and discharge allow a river to carry more sediment. For exams link increased energy with carrying capacity.

A glacier can carry large and small particles together so its deposit can be unsorted. For exams link moraine with unsorted deposits.

Debris flow involves water mixed loose material flowing while slide involves sliding. In exams connect flow with water rich movement.

Erosion removes material and deposition builds new landforms. For exams treat them as complementary processes of landform change.

Slope makes gravity effective in causing downward movement. For exams connect hill slopes with mass movement.

In a lake water velocity decreases and fine particles settle. For exams connect calm water with deposition.

Low velocity and low discharge reduce river carrying capacity. For exams link low energy with low transport.

Dry areas with loose sand and sparse vegetation allow stronger wind erosion. For exams connect deserts with wind erosion.

Material is first eroded and then deposited when energy decreases. In exams understanding the process sequence is important.

Bed load includes larger particles rolling or bouncing along the river bed. For exams link heavy particles with bed load.

Terraces reduce runoff speed and protect soil. For exams remember it as a soil conservation method.

Direct answer: A, coastal erosion. Sea waves repeatedly strike cliffs and shore rocks. The impact, pressure and movement of water loosen particles, enlarge cracks and remove material; this wearing away is called coastal erosion. A is correct because it names the process directly caused by wave action. B, terrestrial condensation, concerns water vapour changing into liquid on land and is unrelated to wave attack. C, river deposition, means a river leaves sediment, whereas waves here are cutting and removing rock. D, soil creep only, is the very slow downhill movement of soil under gravity and does not describe wave action; the word “only” also makes it unsuitable. Exam cue: waves cutting a shore produce erosion, caves, arches and cliffs.

Vegetation and good drainage make slopes more stable. For exams remember roots and drainage for stability.

The correct answer is C. A river’s ability to carry material depends strongly on its velocity. Large, dense particles require stronger moving water, so when velocity suddenly falls, large pebbles and coarse sand lose support and settle first. Smaller particles such as silt and clay can remain suspended in slower water and may travel farther before deposition. Dissolved salts are carried within the water as a solution and do not behave like ordinary solid bed load. Vapour is not the normal solid sediment transported and deposited by a river. A common confusion is to think that the finest particles settle first because they are small; in reality, small particles are often carried farther because they settle slowly. Memory cue: largest load first, finest load last.

Slow downslope movement of small particles is typical of soil creep. For exams remember slow and continuous movement.

In river transportation particles of different sizes move with the current. For exams treat transport as the link between erosion and deposition.

Rainwater easily washes soil from a bare slope. For exams connect lack of vegetation with soil erosion.

An agent is a medium that performs erosion transport or deposition. For exams treat water wind glaciers and waves as major agents.

Steep slopes and loose sediments increase the chance of landslides. For exams connect unstable slopes with landslide risk.

In traction large particles drag or roll along the river bed. For exams link heavy particles with traction.