Geomorphology Questions and Answers

Answer: D

The concept of base level of erosion was proposed by J. W. Powell, who in his exploration of the Colorado River region described the level below which a stream cannot erode its bed, with sea level as the ultimate base level. Davis is known for the geographical cycle, Malott for work on karst and Johnson for shoreline studies, so none of them proposed the base level concept. The answer is Powell.

Answer: B

Both statements are true, but the reason does not explain the assertion, so the answer is B. Ice moves faster on steep slopes and where the ice is thick, which is the assertion. The reason is also true: movement is slower at the sides and bottom because of friction with the valley walls and floor and because the ice is thinner there. But the slowing at the sides does not explain why velocity increases with slope and thickness, so (R) is not the explanation. Options C and D make one true statement false.

Answer: C

The key states that Paige, Blackwelder and Johnson are the scholars who stressed the role of lateral erosion by streams in forming pediments. Lateral planation by streams issuing from the mountain front was the explanation of Blackwelder, Paige and Johnson, in contrast to the sheet-flood explanation of McGee. Hence the groups that include McGee are wrong, and the group that includes Lawson does not match, so the answer is C.

Answer: B

Incised meanders, paired valley terraces and multi-cyclic valleys are all topographic evidence of rejuvenation, which is a renewal of erosive power by uplift or a fall in base level: the stream cuts down into its old valley, leaving terraces, entrenched meanders and valleys with more than one cycle of profile. Structural benches are a product of differential erosion on horizontal layers of hard and soft rock and need not indicate rejuvenation, so the answer is B.

Answer: B

Loess is a wind deposit (iii), moraines are glacial deposits (ii), gravels are a marine deposit here (iv) and silt is a river deposit (i). The codes are (iii) (ii) (iv) (i), option B. Option A gives loess a river origin, option C gives moraines a river origin and option D gives moraines a marine origin, and each is wrong because loess is carried by wind and moraines are laid down by glaciers.

Answer: D

A paternoster lake is one of a series of lakes formed on glacial stairways: in a glaciated valley the ice scoops out hollows in the rock steps and the water collects in them, so they are arranged like beads of a rosary, which gives them the name. A lake of volcanic origin is a crater lake, a shallow stretch of water cut from the sea is a lagoon and a crescent shaped lake formed by a cut-off meander is an oxbow lake. The answer is D.

Answer: B

An earthquake is rated major if its magnitude on the Richter scale is between 7.0 and 7.9, option B. The usual descriptive classes are light at 4.0 to 4.9, moderate at 5.0 to 5.9, strong at 6.0 to 6.9, major at 7.0 to 7.9 and great at 8.0 and above.

The range in option A, 4.0 to 4.9, is the light class. The range in option D, 5.0 to 5.9, is the moderate class, and the range in option C, 6.0 to 6.9, is the strong class. Each of the wrong options is a lower class.

Answer: A

The Richter scale is logarithmic to the base 10: an increase of one unit means that the amplitude of the seismic wave is ten times larger (and the energy about thirty-two times larger). So the factor is 10. The values 100 and 1000 are the factors for two and three units, and 2 is not a factor of the scale.

Answer: B

Carbonation is the process that weathers rocks in a karst region. Karst forms on soluble carbonate rocks such as limestone and dolomite. Rain absorbs carbon dioxide and becomes weak carbonic acid, which converts calcium carbonate into soluble calcium bicarbonate that is carried away, producing sinkholes, caves and limestone pavements.

Scree formation is a product of frost shattering and gravity, not of chemical attack on limestone. Oxidation acts on iron-bearing minerals and gives rust-coloured weathering. Hydrolysis breaks down silicate minerals such as feldspar into clay, which is typical of granite, not of karst.

Answer: A

An esker is the glacial feature formed in the bed of a sub-glacial stream. Meltwater flowing in a tunnel beneath or within the ice carries sand and gravel and deposits it along the channel. When the ice melts a long, narrow, sinuous ridge of stratified material is left.

A moraine is unsorted debris dumped directly by the ice, not by a stream. A drumlin is a streamlined hill of till moulded under moving ice. A kame is a mound or hillock of stratified drift laid down by meltwater at the ice margin, not in a stream bed under the ice.