Geomorphology Questions and Answers

Answer: D

Chemical weathering is more effective than mechanical weathering in the cool temperate region, as the official key gives. There moisture is available all year and the low temperature keeps organic acids and dissolved carbon dioxide in the water, so reactions such as solution, carbonation and hydrolysis work on the rock steadily.

In arid and semi-arid regions water is scarce, so weathering is dominated by mechanical processes such as temperature-driven expansion and contraction. A coastal region is mainly affected by wave action and salt crystallisation, which are largely mechanical or physical processes.

Answer: A

The slope formula with the number of contours per mile times the contour interval divided by 3361 is Wentworth's method. Wentworth expressed the tangent of the angle of slope in this way from the contour spacing on a map, so the number of contours crossed along a mile gives the gradient.

Raiz, Henry and Davis are the other names in the options. They are associated with other methods of describing relief (for example Raiz with landform maps and Davis with the cycle of erosion), not with this contour-count formula for average slope.

Answer: A

Both (A) and (R) are true and (R) is the correct explanation of (A). Wind erodes, transports and deposits material, but its work is widespread only where there is little vegetation and loose dry sediment, which means desert regions with scanty rainfall. Running water acts nearly everywhere on land, so wind is less widespread as an agent of gradation.

Because (R) states exactly why wind is limited to such regions, it explains (A). Option B is wrong since (R) does explain (A); options C and D are wrong because both statements are true.

Answer: A

The 'Two-Cycle Theory' of the origin of limestone caverns was proposed by Davis. He suggested that caverns were first dissolved below the water table in one cycle, and then, after uplift or lowering of the water table, were drained and decorated with deposits in a second cycle.

Swinerton, Gardner and Malott are the other names offered, but the two-cycle explanation is credited to Davis, which is why the key gives Davis. Naming it as a theory of one writer's cycle idea also fits his wider work on cycles of erosion.

Answer: A

All the processes that tend to bring the surface of the lithosphere to a common level are collectively known as gradation. It covers degradation (lowering of high ground by weathering and erosion) and aggradation (building up of low ground by deposition).

Degradation and aggradation are only the two halves of gradation, so neither can be the collective name. Mass wasting is just one process, the downslope movement of material under gravity, and is a part of degradation.

Answer: A

One of the forces responsible for continental drift according to Wegener was the tidal force. He argued that the pull of the sun and the moon on the earth acted to move the continents westwards.

Convection currents were proposed later by Arthur Holmes, not by Wegener. Tensional and compressional force are not forces Wegener proposed for drift, which he explained by the pole-fleeing force and the tidal force.

Wegener thought that the tidal attraction of the moon and the sun, together with the pole-fleeing force (centrifugal force from the earth's rotation), moved the continents. The idea was criticised because these forces seemed too weak, but he named them as the drivers of drift.

Answer: C

The normal cycle of erosion is associated with river erosion.

W. M. Davis described the 'normal' or fluvial cycle, in which a land mass raised above base level is cut by running water through the stages of youth, maturity and old age until it is reduced to a peneplain. Davis treated the work of rivers as the normal process in humid regions. Marine, wind (arid) and glacial erosion are treated as special cycles with their own landforms, which is why they are called modifications of the normal cycle rather than the normal cycle itself.

Answer: C

The correct matching is I-4, II-1, III-2, IV-3, which is option C.

A kettle is a deep depression, usually along the moraine belt, left where a block of buried ice melted (4). A tarn is a small mountain lake occupying a cirque (1). An esker is a low winding ridge of glacio-fluvial sand and gravel deposited by a stream flowing in or under the ice (2). A drumlin is an oval or elliptical hill of glacial till (3). Options A, B and D swap two or more of these, for example giving the cirque lake to the drumlin or the till hill to the kettle.

Answer: D

Most of the details of the world's topography belong to the Cenozoic era.

The present relief of the earth, including the Himalaya, the Alps and the Andes, the plains and the river valleys, was shaped largely in the last sixty-odd million years of the Cenozoic, through the Alpine mountain building and later erosion and glaciation. Pre-Cambrian, Palaeozoic and Mesozoic structures survive in shields, old fold belts and plateaus, but they have been worn down or buried, so most of the surface detail we see is of Cenozoic age.

Answer: A

Valleys that drain in the same direction as the original consequent drainage, but at a lower level and adjusted to new base levels, are resequent streams. Obsequent streams flow in the opposite direction to the consequent ones, down the face of a scarp. Insequent streams have no relation to the structure or the original slope and run in any direction, and subsequent streams develop along belts of weak rock at right angles to the consequents. Only resequent matches the description, so the answer is A.