Geomorphology Questions and Answers

Answer: A

Both (A) and (R) are true and (R) is the correct explanation of (A).

A fjord is a long, deep, steep-sided inlet of the sea. During glaciation a valley glacier deepens and widens a river valley into a U-shaped trough, often eroding it far below sea level. When the glacier melts back, the sea floods the trough, producing the fjords of Norway, Chile, Greenland and New Zealand.

The assertion says fjords are products of glacial erosion, and the reason describes exactly how that erosion and the later drowning create them, so R explains A. That rules out the options in which one statement is false or R does not explain A.

Answer: A

The difference is that conglomerate is round and breccia is angular.

Both are coarse clastic sedimentary rocks made of gravel-size fragments cemented together. In a conglomerate the fragments are rounded, because they were worn down by long transport in rivers or along beaches. In a breccia the fragments are angular, because they were deposited close to their source, as in scree, fault zones or landslide debris, without being rounded.

Option B reverses the two, and colour, porosity and compactness vary within each rock type, so they are not what distinguishes them.

Answer: C

The correct matching is a-4, b-3, c-1, d-2.

1. A scroll lake (oxbow or scroll-bar lake) forms on the inside of a river meander.
2. An alluvial fan builds up where a stream leaves the mountains at the piedmont and drops its load.
3. At a river mouth a delta splits the river into distributaries.
4. In a desert neighbouring alluvial fans merge into a bajada along the mountain foot.

Option A puts the scroll lake with distributaries and option B puts it with a bajada; option D links it with the piedmont, so only C fits all four.

Answer: C

Such wind-deposited silt is called loess.

Loess is a yellowish, unstratified deposit of silt-size particles (about 0.002-0.06 mm) carried by the wind from deserts and from glacial outwash plains and laid down far away. The thick loess of the Loess Plateau of China, from Gobi dust, and the loess of the Mississippi valley and central Europe are classic examples, and they form very fertile soils.

Dunes are mounds of wind-blown sand, not silt; tufa is a calcium carbonate deposit from springs; and colluvium is loose material moved down slopes by gravity.

Answer: C

The correct matching is a-3, b-2, c-4, d-1.

1. A natural levee is built by running water, when a river overflows and drops sediment along its banks.
2. A drumlin is a smooth, elongated hill of till shaped by a moving glacier.
3. A polje is a large flat-floored depression in karst country, formed by solution by underground water.
4. A seif is a long, sharp-crested linear dune shaped by the wind.

Options A and D give the polje to wind, and option B gives the levee to underground water, so only C is right.

Answer: A

The order from lower to higher altitude is (2) (3) (1) (4): medial moraine, cirque, arete, horn.

A medial moraine is a ridge of debris carried down the middle of a valley glacier where two glaciers join, so it lies lowest, on the glacier in the valley. Cirques are armchair-shaped hollows at the head of the valley where the glacier starts. Where two cirques erode back to back, the sharp ridge left between them is an arete, and where three or more cirques cut into one peak they leave a pyramidal horn, such as the Matterhorn, at the summit.

The other orders put the horn or arete below the cirque or the moraine at the top, which reverses the glacial landscape.

Answer: B

Slate forms by metamorphism of shale.

Shale is a fine-grained sedimentary rock of clay and silt. Under low-grade regional metamorphism its clay minerals recrystallise into tiny aligned micas, giving slate its slaty cleavage, which lets it split into thin flat sheets used for roofing. Further metamorphism turns it into phyllite and then schist.

Sandstone metamorphoses into quartzite, limestone into marble, and granite into gneiss, so none of them forms slate.

Answer: D

The correct matching is (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i).

1. A slide moving on a planar shear surface is a translational slide.
2. A slide on a curved, concave-up (spoon-shaped) surface, which rotates backwards as it moves, is a rotational slide or slump.
3. Loose material that has crept and washed down the valley sides and accumulated at their foot is colluvium.
4. A flowing mass of volcanic debris mixed with water is a lahar.

Options pairing (a) with lahar or rotational slide, or (b) with colluvium, confuse the shape of the failure surface with the type of deposit. Option C differs from the answer only by swapping colluvium and rotational slide for (b) and (c).

Answer: D

The parameter not used is kinematic viscosity.

Mean flow velocity in an open channel is normally estimated with the Manning equation:

\[ V = \frac{1}{n} R^{2/3} S^{1/2} \]

where R is the hydraulic radius (cross-sectional area divided by wetted perimeter), S is the channel (energy) slope and n is the Manning roughness coefficient. All three of the other options appear in it.

Kinematic viscosity enters the Reynolds number, which tells whether flow is laminar or turbulent, but natural rivers are fully turbulent and the Manning formula does not include it.

Answer: C

The Atlas mountains are not in Europe.

The Atlas range runs for about 2,500 km across north-west Africa, through Morocco, Algeria and Tunisia. Like the European Alpine ranges it was raised by the collision of the African and Eurasian plates, but it lies on the African side of the Mediterranean.

The Pyrenees separate France and Spain, the Alps run from France through Switzerland and Italy to Austria and Slovenia, and the Carpathians arc through Slovakia, Poland, Ukraine and Romania, so all three are European.