Table of Contents
Upper Course Landforms #
1. V-shaped valleys are primarily formed by which process?
Answer: C
V-shaped valleys form when rivers cut downward through vertical erosion. The river cuts down into the rock while weathering breaks down the valley sides. Mass movement then carries the weathered material down to the river, creating the characteristic V-shape.
2. Why do rivers in mountainous areas flow around hills rather than cutting straight through them?
Answer: A
Rivers take the path of least resistance. In mountainous areas, the rock is usually hard, so it’s much easier for water to flow downward using gravity than to cut horizontally through solid rock. This creates interlocking spurs as rivers wind around hills.
3. What geological condition is essential for waterfall formation?
Answer: D
Waterfalls need hard rock on top of soft rock. The soft rock underneath erodes faster than the hard rock above, creating an overhang. Eventually the hard rock collapses, forming the waterfall. This process continues as the waterfall retreats upstream.
4. What is a plunge pool?
Answer: C
A plunge pool forms at the bottom of a waterfall where the falling water hits the riverbed. The force of the water and stones it carries creates a deep, circular pool through hydraulic action and abrasion.
5. How do waterfalls retreat upstream?
Answer: D
Waterfall retreat happens when the soft rock beneath is eroded faster than the hard rock above. This creates an overhang of hard rock that eventually becomes unstable and collapses. This process repeats, moving the waterfall slowly upstream over thousands of years.
6. What type of landform is created when a waterfall retreats over thousands of years?
Answer: A
As a waterfall retreats upstream over thousands of years, it leaves behind a steep-sided, narrow valley called a gorge. The gorge shows the path the waterfall took as it moved upstream. Famous examples include Niagara Gorge.
7. Potholes in riverbeds are formed by:
Answer: C
Potholes form when stones get trapped in small depressions in the riverbed. Fast-flowing water makes these stones spin around like a drill, gradually wearing away the rock to create deep, circular holes. This process is called corrasion or abrasion.
8. What are interlocking spurs?
Answer: B
Interlocking spurs are hills that existed before the river formed. The river flows around these hills because it’s easier than cutting through hard rock. From above, these hills appear to “interlock” like fingers, creating a zigzag river pattern.
Middle and Lower Course Landforms #
9. Why does water flow faster on the outside of a river bend?
Answer: A
On the outside of a meander, water has to travel a longer distance in the same time as water on the inside. This means it must flow faster to keep up. The faster flow causes more erosion on the outside bend.
10. What is helicoidal flow?
Answer: B
Helicoidal flow is the spiral movement of water in a meander. Water flows fast on the surface at the outside of the bend, then spirals down and across the river bed to the inside of the bend. This carries sediment from the eroded outside bank to the inside bank where it’s deposited.
11. What is a slip-off slope?
Answer: A
A slip-off slope forms on the inside of a meander where water flows slowly. The slow water deposits sediment here, creating a gentle slope. This contrasts with the steep river cliff on the outside of the meander where erosion occurs.
12. How does an oxbow lake form?
Answer: B
Oxbow lakes form when meanders become very pronounced. Eventually, the river cuts through the narrow neck of land between two bends, creating a new, straighter course. The old meander loop gets cut off and forms a crescent-shaped lake.
13. What typically triggers the formation of an oxbow lake?
Answer: B
Major floods often trigger oxbow lake formation. During floods, rivers have much more energy and can cut through the narrow neck of a meander more easily. The increased water volume and speed allow the river to take the shorter, straighter route.
14. Why are floodplains considered fertile?
Answer: A
Floodplains are fertile because they’re covered with alluvium – fine sediment deposited by floods. This sediment contains nutrients from upstream areas, making the soil very rich for farming. The Nile Delta is a famous example of fertile floodplain agriculture.
15. How are floodplains widened over time?
Answer: A
Floodplains widen as meanders migrate laterally across the valley floor over time. As meanders erode the outside banks and deposit on inside banks, they slowly move sideways, creating a wider flat area that becomes the floodplain.
16. What happens to sediment when flood water slows down on a floodplain?
Answer: D
When flood water slows down, it loses energy and can no longer carry sediment. The heaviest particles (like sand) are deposited first, close to the river channel. Lighter particles (like clay) are carried further away before being deposited.
17. Natural levées are formed by:
Answer: C
Natural levées form when floods deposit the heaviest sediment closest to the main river channel. Over many flood events, this builds up raised banks along the river. The water slows down immediately when it leaves the channel, so deposits the heaviest material first.
18. Why do natural levées make flooding more dangerous?
Answer: C
Natural levées raise the height of river banks, allowing more water to be contained in the channel. If the levées break during extreme floods, the water falls from a greater height onto the surrounding land, causing more damage and deeper flooding.
Deltas and River Mouths #
19. What conditions are necessary for delta formation?
Answer: A
Deltas need two main conditions: rivers that carry lots of sediment, and calm water (sea or lake) where the sediment can settle. If the sea has strong waves or currents, they wash the sediment away before it can build up to form a delta.
20. What are distributaries?
Answer: D
Distributaries are the multiple channels that form when a river splits up as it flows through its delta. As sediment builds up, it blocks parts of the main channel, forcing the river to find new routes to the sea. This creates a network of smaller channels.
21. Why does a river’s velocity decrease when it enters the sea or a lake?
Answer: B
When a river enters the sea or lake, it spreads out into a much larger body of water. This reduces the velocity because the same amount of water is now spread over a much wider area. The reduced velocity means the river can no longer carry sediment, so it gets deposited.
Landform Identification and Location #
22. Which landforms would you expect to find in the upper course of a river?
Answer: C
Upper course rivers are characterized by vertical erosion and steep gradients. This creates V-shaped valleys (from downcutting and weathering) and waterfalls (where hard and soft rocks meet). Meanders, floodplains, and deltas form in middle and lower courses.
23. What is the main difference between upper course and lower course river processes?
Answer: C
Upper course rivers have steep gradients and cut downward (vertical erosion) to form V-shaped valleys. Lower course rivers have gentle gradients and erode sideways (lateral erosion) while also depositing sediment to form floodplains and deltas.
24. A student sees a river with a narrow channel, steep valley sides, and large boulders in the channel. This is most likely:
Answer: B
These features are typical of upper course rivers: narrow channels (not much water), steep valley sides (V-shaped valleys), and large boulders (angular load that hasn’t been worn down by transport). Lower course rivers have wide channels, gentle sides, and fine sediment.
25. What evidence would suggest that a valley was formed by river erosion rather than glacial erosion?
Answer: D
River valleys have V-shaped cross-sections and interlocking spurs because rivers wind around obstacles. Glacial valleys are U-shaped with straight sides because glaciers are powerful enough to cut straight through obstacles, creating wide, flat-bottomed valleys.
Processes and Formation #
26. What role does mass movement play in V-shaped valley formation?
Answer: D
Mass movement (like soil creep and rockfalls) is essential for V-shaped valley formation. While the river cuts down vertically, weathering breaks up the valley sides. Mass movement then carries this weathered material down to the river, which removes it. This widens the valley and creates the V-shape.
27. Why do meanders tend to become larger over time?
Answer: D
Meanders grow larger through positive feedback. Fast water on the outside bend causes erosion, making the bend deeper. Slow water on the inside bend causes deposition, making the bend wider. This process continues, making meanders progressively larger over time.
28. The term “alluvium” refers to:
Answer: D
Alluvium is the fine, fertile sediment that rivers deposit on floodplains and in deltas. It’s called “alluvial soil” and is very good for farming because it contains nutrients from areas the river has flowed through upstream.
29. What is the main reason why not all rivers form deltas?
Answer: C
Many rivers don’t form deltas because strong waves, tides, or ocean currents wash away the sediment before it can build up. The river mouth needs to be in calm water for sediment to settle and accumulate. Strong coastal processes prevent delta formation.
30. A geography student observes a crescent-shaped lake next to a meandering river. This feature is most likely:
Answer: D
A crescent-shaped lake next to a meandering river is characteristic of an oxbow lake. These form when meanders become so pronounced that the river cuts through the neck, leaving the old bend isolated as a curved lake. The crescent shape is the distinctive feature.
Study Tips for River Landforms:
- Remember the three course model: Upper (erosion), Middle (erosion and deposition), Lower (deposition)
- Connect landforms to processes: V-valleys = vertical erosion, Meanders = lateral erosion
- Think about energy: High energy = erosion, Low energy = deposition
- Practice identifying landforms from photos and maps
- Learn the formation processes step by step for each landform
