Why do rivers form waterfalls in steps along their course?
Quick Answer
Step-like waterfalls form when a river crosses alternating bands of hard and soft rock or a staircase of rock layers. The softer sections erode faster, leaving drops and ledges.
The Full Story
Not all waterfalls are tall single drops; some rivers descend through a series of smaller steps. This happens when rock layers differ in hardness or when the riverbed has been broken into successive ledges by tectonic uplift or erosion. Each hard layer resists wear better than the softer material around it. Water plunges over one ledge, then another, creating a stepped profile. Such cascades are common in young mountain rivers and in regions with layered sedimentary or volcanic rocks.
Key Facts
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"Why some waterfalls come in a series of steps"