Weathering and Erosion Questions and Answers

Answer: A

Correct answer: solution

A river erodes four ways: hydraulic action, the sheer force of the water prising material loose; abrasion, the load it carries scouring the bed and banks; attrition, the load wearing itself smaller as the fragments collide; and solution, the chemical removal of soluble rock. Deflation is a wind process and plucking a glacial one, so neither belongs to a river.

Answer: B

Correct answer: a river

A river cuts downward in a narrow channel while the valley sides are worn back by weathering and slope processes, giving the characteristic V cross-section with interlocking spurs where the river winds. A glacier occupies the whole valley floor and erodes the sides as well as the bed, which straightens and deepens it into the quite different U shape.

Answer: C

Correct answer: a glacier

Ice fills the valley and erodes its sides as well as its floor, so it deepens and widens the valley into a U and cuts straight through the spurs a river would have wound around, leaving them truncated. Hanging valleys where tributary glaciers joined, and striations on the rock surfaces, complete the diagnosis.

Answer: D

Correct answer: removes loose fine material from a surface

Deflation is the wind lifting and carrying away loose sand and silt, leaving the coarser material behind as a lag deposit or desert pavement, and lowering the surface it strips. It is one of the two wind erosion processes, the other being abrasion, in which carried sand blasts against rock. Depositing the material as dunes or as loess is the subsequent stage.

Answer: A

Correct answer: wind, as silt carried far from its source

Loess is wind-blown silt, characteristically derived from glacial outwash or from desert margins and carried hundreds of kilometres before settling. It is unstratified, remarkably uniform in grain size, and held together by a weak clay and carbonate bond that gives it the ability to stand in vertical faces - and that collapses when the deposit is wetted.

Answer: B

Correct answer: unsorted and unstratified

Ice carries everything it picks up at the same speed regardless of size, so when it melts it dumps clay, silt, sand, gravel and boulders together with no separation and no layering. Water and wind sort their load by size as their velocity changes, producing the stratification typical of river and dune deposits. Till is therefore recognised at once by its chaotic mixture of sizes.

Answer: C

Correct answer: slow and imperceptible

Creep is the downslope movement of soil at millimetres a year, driven by repeated wetting and drying, freezing and thawing, and the burrowing of animals - each cycle displacing the particles a little further downhill. It is never observed directly; it is inferred from tilted poles and walls, curved tree trunks and bent strata near the surface. A landslide moves the same material in minutes.

Answer: D

Correct answer: curved, concave upward

A rotational slide fails on a curved surface, so the mass rotates backwards as it moves: the head drops leaving a steep scarp, the surface tilts back towards the slope, and the toe bulges outward. It is characteristic of thick homogeneous clay, where no plane of weakness dictates the surface and it forms in the position of least resistance. A planar surface indicates a bedding plane or joint controlling the failure.

Answer: A

Where a weak layer or an adversely dipping bedding plane exists, failure exploits it rather than generating its own surface. Identifying such planes and their dip relative to the slope is the essence of rock slope analysis.

Answer: B

Correct answer: travelling largely through the air

A fall detaches from a steep face and descends through the air, bouncing and rolling on arrival - there is no sliding surface and no continuous contact with the slope. A slide maintains contact and moves along a defined failure surface. The distinction governs the remedy: falls are dealt with by netting, catch fences and ditches, slides by drainage and by stabilising the surface itself.