ASBOG Geomorphology and Quaternary Geology 3 — Questions and Answers
Question 1: Stream terraces form primarily as a result of:
- Lateral erosion widening the floodplain
- Stream incision following a change in base level or sediment supply (Correct answer)
- Aggradation caused by increased discharge
- Tectonic uplift blocking downstream flow
Correct answer: Stream incision following a change in base level or sediment supply
Stream terraces are abandoned floodplains left elevated when a river incises downward due to falling base level or decreased sediment supply.
Question 2: Which process describes the downslope movement of water-saturated soil and debris as a coherent mass over a curved failure surface?
- Debris flow
- Rotational slump (Correct answer)
- Solifluction
- Creep
Correct answer: Rotational slump
A rotational slump involves movement along a concave-upward failure surface, with the mass rotating backward as it slides.
Question 3: Pleistocene pluvial lakes, such as Lake Bonneville, formed primarily because of:
- Glacial meltwater input from nearby ice sheets
- Increased precipitation and reduced evaporation under cooler climates (Correct answer)
- Tectonic subsidence creating closed basins
- Volcanic damming of regional drainage
Correct answer: Increased precipitation and reduced evaporation under cooler climates
Pluvial lakes expanded during glacial intervals due to cooler, wetter conditions that reduced evaporation and increased precipitation.
Question 4: What is the term for a crescent-shaped sand dune with horns pointing downwind?
- Star dune
- Barchan (Correct answer)
- Transverse dune
- Longitudinal dune
Correct answer: Barchan
Barchan dunes are crescent-shaped with the concave side downwind, forming where sand supply is limited and wind direction is consistent.
Question 5: Drumlins are elongated glacial landforms that indicate:
- The direction of ice retreat
- The direction of former glacial flow (Correct answer)
- The location of a terminal moraine
- Areas of maximum glacial melting
Correct answer: The direction of former glacial flow
Drumlins are streamlined subglacial landforms whose long axes parallel the direction of ice flow, with the blunt end facing up-ice.
Question 6: Which luminescence dating technique uses heat to release trapped electrons from mineral grains to determine burial age?
- Optically stimulated luminescence (OSL)
- Thermoluminescence (TL) (Correct answer)
- Electron spin resonance (ESR)
- Carbon-14 dating
Correct answer: Thermoluminescence (TL)
Thermoluminescence (TL) dating releases trapped electrons by heating mineral grains, measuring light emitted to calculate the time since last exposure to heat or light.
Question 7: A wave-cut platform is best described as:
- A sandy beach deposited by longshore drift
- A subhorizontal bedrock surface eroded by wave action at the base of a sea cliff (Correct answer)
- A coral reef platform exposed at low tide
- A deltaic plain at a river mouth
Correct answer: A subhorizontal bedrock surface eroded by wave action at the base of a sea cliff
Wave-cut platforms are flat or gently sloping bedrock surfaces formed by wave erosion at the base of retreating sea cliffs.
ASBOG Geomorphology and Quaternary Geology 3
Stream terraces form primarily as a result of: