Transcription: A river is born at its source when underground springs reach the earth's surface and join rainwater and melted snow that have collected into streams. Other streams flowing into the new river are called tributaries. Rivers erode the rock over which they flow, initially cutting down and creating a winding valley. The river's banks are typically steep and V-shaped. When the river flows over hard rock onto soft rock, the softer rock wears away, ultimately creating a waterfall. As the river reaches flatter land, it flows more slowly and creates wider loops called meanders. Sometimes the river break ...
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