Why can a long active fault affect more river basins than a short one?
Show answer & explanation
Answer: Longer fault, wider zone of weakened rock
Longer fault, older surrounding rock — Wrong. Rock age is not directly related to fault length. A long fault can cut through both young and old rocks. The key factor is the extent of the weakened rock zone, which scales with fault length.
Longer fault, more frequent earthquakes — Wrong. Longer faults can produce larger earthquakes, but the effect on river basins comes from the permanent weakened rock around the fault, not from how often earthquakes strike. The weakened zone exists regardless of recent seismic activity.
Longer fault, wider zone of weakened rock ✓ — Correct! A long active fault leaves a broad zone of fractured, weakened rock that fades with distance from the fault. This weakened zone can overlap many river basins, making erosion easier over a large area. The key is that fault length controls how far the rock weakening extends, not just how many earthquakes occur.
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