Alluvial Fans mean:
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Answer: D. All of the above
Explanation
Alluvial fans form when stream flows emerge from narrow valleys into wider plains, suddenly slowing down and spreading out. As high-energy mountain streams enter flatter valley floors, they experience a sudden reduction in transport capacity. This abrupt loss of stream energy causes suspended sediment loads to deposit in a characteristic fan-shaped geometric pattern. Geomorphological landforms known as alluvial fans are depositional features commonly found in arid and semi-arid mountain foothills. Stream velocity drops rapidly as water disperses across multiple distributary channels radiating outward from the canyon mouth. Coarser gravel and boulders drop out near the apex while finer sand and silt particles travel further down the fan slope.
Option A describes the geographic setting where streams flow into larger valleys but ignores energy loss and deposition mechanics. Option B notes the spreading out behavior of water but omits the crucial stream velocity reduction and energy loss aspects. Option C explains stream slowing and energy loss but leaves out the initial valley exit setting where fans originate.
- Subject
- Agriculture
- Category
- Forestry
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- —
- Difficulty
- medium
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