Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls. ... As a stream flows, it carries sediment.

How do waterfalls not run out of water?

If the sun were to stop shining, then all the waterfalls in the world would eventually stop. It is the sun which provides all of the energy needed to lift water from the ocean to the head of the river valley so that waterfalls can continually have water falling over them.

How do waterfalls begin?

Waterfalls may at first start off as rapids. The river flows over the hard rock while the soft rock beneath gets eroded. ... Eventually, the river flow becomes steep enough and forms the familiar formation of a waterfall. The hard rock also breaks loose after gradual erosion and falls into the plunge pool.