📖 what
What is an alluvial fan?
Quick Answer
An alluvial fan is a fan-shaped deposit of sediment laid down where a fast-moving stream loses energy and spreads out on flatter ground.
The Full Story
Alluvial fans often form at the base of mountains where a stream exits a narrow canyon and suddenly slows down. Coarse gravel is dropped near the apex, while finer sand and silt are carried farther out, creating a graded fan shape. These features are common in arid and semi-arid regions, but they can occur anywhere steep terrain meets a plain. Alluvial fans can be important groundwater reservoirs and can also pose flash-flood hazards.
Key Facts
1.They form where streams lose energy at mountain fronts
2.Coarser sediment settles near the top of the fan
3.They are common in dry climates
YouTube Angle
Suggested video title for this topic:
"How mountain streams build giant gravel fans"
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